Fatih Gurcan

PeerJ Computer Science • 2024

Background The continuous increase in carbon dioxide (CO 2 ) emissions from fuel vehicles generates a greenhouse effect in the atmosphere, which has a negative impact on global warming and climate change and raises serious concerns about environmental sustainability. Therefore, research on estimating and reducing vehicle CO 2 emissions is crucial in promoting environmental sustainability and reducing greenhouse gas emissions in the atmosphere. Methods This study performed a comparative regression analysis using 18 different regression algorithms based on machine learning, ensemble learning, and deep learning paradigms to evaluate and predict CO 2 emissions from fuel vehicles. The performance of each algorithm was evaluated using metrics including R 2 , Adjusted R 2 , root mean square error (RMSE), and runtime. Results The findings revealed that ensemble learning methods have higher prediction accuracy and lower error rates. Ensemble learning algorithms that included Extreme Gradient Boosting (XGB), Random Forest, and Light Gradient-Boosting Machine (LGBM) demonstrated high R 2 and low RMSE values. As a result, these ensemble learning-based algorithms were discovered to be the most effective methods of predicting CO 2 emissions. Although deep learning models with complex structures, such as the convolutional neural network (CNN), deep neural network (DNN) and gated recurrent unit (GRU), achieved high R 2 values, it was discovered that they take longer to train and require more computational resources. The methodology and findings of our research provide a number of important implications for the different stakeholders striving for environmental sustainability and an ecological world.

Fred Farrell, Orkun S. Soyer, Christopher Quince

bioRxiv (Cold Spring Harbor Laboratory) • 2018

Abstract The increasing popularity of genome resolved meta genomics - the binning of genomes of potentially uncultured organisms direct from the environmental DNA - has resulted in a deluge of draft genomes. There is a pressing need to develop methods to interpret this data. Here, we used machine learning to predict functional and metabolic traits of microbes from their genomes. We collated an extensive database of 84 phenotypic traits associated with 9407 prokaryotic genomes and trained different machine learning models on this data. We found that a lasso logistic regression based on the frequency of gene orthologs had the best combination of functional prediction performance and interpretability. This model was able to classify 65 phenotypic traits with greater than 90

M. Mashkour, M. Rahimnejad, F. Raouf et al.

Biofuel Research Journal • 2021

Materials at the nanoscale show exciting and different properties. In this review, the applications of nanomaterials for modifying the main components of microbial fuel cell (MFC) systems (i.e., electrodes and membranes) and their effect on cell performance are reviewed and critically discussed. Carbon and metal-based nanoparticles and conductive polymers could contribute to the growth of thick anodic and cathodic microbial biofilms, leading to enhanced electron transfer between the electrodes and the biofilm. Extending active surface area, increasing conductivity, and biocompatibility are among the significant attributes of promising nanomaterials used in MFC modifications. The application of nanomaterials in fabricating cathode catalysts (catalyzing oxygen reduction reaction) is also reviewed herein. Among the various nanocatalysts used on the cathode side, metal-based nanocatalysts such as metal oxides and metal-organic frameworks (MOFs) are regarded as inexpensive and high-performance alternatives to the conventionally used high-cost Pt. In addition, polymeric membranes modified with hydrophilic and antibacterial nanoparticles could lead to higher proton conductivity and mitigated biofouling compared to the conventionally used and expensive Nafion. These improvements could lead to more promising cell performance in power generation, wastewater treatment, and nanobiosensing. Future research efforts should also take into account decreasing the production cost of the nanomaterials and the environmental safety aspects of these compounds.

Ren Wei, W. Zimmermann

Microbial Biotechnology • 2017

Petroleum‐based plastics have replaced many natural materials in their former applications. With their excellent properties, they have found widespread uses in almost every area of human life. However, the high recalcitrance of many synthetic plastics results in their long persistence in the environment, and the growing amount of plastic waste ending up in landfills and in the oceans has become a global concern. In recent years, a number of microbial enzymes capable of modifying or degrading recalcitrant synthetic polymers have been identified. They are emerging as candidates for the development of biocatalytic plastic recycling processes, by which valuable raw materials can be recovered in an environmentally sustainable way. This review is focused on microbial biocatalysts involved in the degradation of the synthetic plastics polyethylene, polystyrene, polyurethane and polyethylene terephthalate (PET). Recent progress in the application of polyester hydrolases for the recovery of PET building blocks and challenges for the application of these enzymes in alternative plastic waste recycling processes will be discussed.

Katherine E. Duncker, Zachary A. Holmes, L. You

Microbial Cell Factories • 2021

Many applications of microbial synthetic biology, such as metabolic engineering and biocomputing, are increasing in design complexity. Implementing complex tasks in single populations can be a challenge because large genetic circuits can be burdensome and difficult to optimize. To overcome these limitations, microbial consortia can be engineered to distribute complex tasks among multiple populations. Recent studies have made substantial progress in programming microbial consortia for both basic understanding and potential applications. Microbial consortia have been designed through diverse strategies, including programming mutualistic interactions, using programmed population control to prevent overgrowth of individual populations, and spatial segregation to reduce competition. Here, we highlight the role of microbial consortia in the advances of metabolic engineering, biofilm production for engineered living materials, biocomputing, and biosensing. Additionally, we discuss the challenges for future research in microbial consortia.

B. D. Batista, B. Singh

Microbial Biotechnology • 2021

The use of microbial tools to sustainably increase agricultural production has received significant attention from researchers, industries and policymakers. Over the past decade, the market access and development of microbial products have been accelerated by (i) the recent advances in plant‐associated microbiome science, (ii) the pressure from consumers and policymakers for increasing crop productivity and reducing the use of agrochemicals, (iii) the rising threats of biotic and abiotic stresses, (iv) the loss of efficacy of some agrochemicals and plant breeding programs and (v) the calls for agriculture to contribute towards mitigating climate change. Although the sector is still in its infancy, the path towards effective microbial products is taking shape and the global market of these products has increased faster than that of agrochemicals. Promising results from using microbes either as biofertilizers or biopesticides have been continually reported, fuelling optimism and high expectations for the sector. However, some limitations, often related to low efficacy and inconsistent performance in field conditions, urgently need to be addressed to promote a wider use of microbial tools. We propose that advances in in situ microbiome manipulation approaches, such as the use of products containing synthetic microbial communities and novel prebiotics, have great potential to overcome some of these current constraints. Much more progress is expected in the development of microbial inoculants as areas such as synthetic biology and nano‐biotechnology advance. If key technical, translational and regulatory issues are addressed, microbial tools will not only play an important role in sustainably boosting agricultural production over the next few decades but also contribute towards other sustainable development goals, including job creation and mitigation of the impacts of climate change.

S. Mandal, William W. Van Treuren, Richard A. White et al.

Microbial Ecology in Health & Disease • 2015

Background Understanding the factors regulating our microbiota is important but requires appropriate statistical methodology. When comparing two or more populations most existing approaches either discount the underlying compositional structure in the microbiome data or use probability models such as the multinomial and Dirichlet-multinomial distributions, which may impose a correlation structure not suitable for microbiome data. Objective To develop a methodology that accounts for compositional constraints to reduce false discoveries in detecting differentially abundant taxa at an ecosystem level, while maintaining high statistical power. Methods We introduced a novel statistical framework called analysis of composition of microbiomes (ANCOM). ANCOM accounts for the underlying structure in the data and can be used for comparing the composition of microbiomes in two or more populations. ANCOM makes no distributional assumptions and can be implemented in a linear model framework to adjust for covariates as well as model longitudinal data. ANCOM also scales well to compare samples involving thousands of taxa. Results We compared the performance of ANCOM to the standard t-test and a recently published methodology called Zero Inflated Gaussian (ZIG) methodology (1) for drawing inferences on the mean taxa abundance in two or more populations. ANCOM controlled the false discovery rate (FDR) at the desired nominal level while also improving power, whereas the t-test and ZIG had inflated FDRs, in some instances as high as 68% for the t-test and 60% for ZIG. We illustrate the performance of ANCOM using two publicly available microbial datasets in the human gut, demonstrating its general applicability to testing hypotheses about compositional differences in microbial communities. Conclusion Accounting for compositionality using log-ratio analysis results in significantly improved inference in microbiota survey data.

Ting Yu, Shixuan Su, Jing Hu et al.

Advanced Materials • 2022

Microorganisms can serve as biological factories for the synthesis of inorganic nanomaterials that can become useful as nanocatalysts, energy‐harvesting–storage components, antibacterial agents, and biomedical materials. Herein, the development of biosynthesis of inorganic nanomaterials into a simple, stable, and accurate strategy for distinguishing microorganisms from multiple classification levels (i.e., kingdom, order, genus, and species) without gene amplification, biochemical testing, or target recognition is reported. Gold nanoparticles (AuNPs) biosynthesized by different microorganisms differ in color of the solution, and their features can be characterized, including the particle size, the surface plasmon resonance (SPR) spectrum, and the surface potential. The inter‐relation between the features of micro‐biosynthetic AuNPs and the classification of microorganisms are exploited at different levels through machine learning to establish a taxonomic model. This model agrees well with traditional classification methods that offers a new strategy for microbial taxonomic identification. The underlying mechanism of this strategy is related to the biomolecules produced by different microorganisms including glucose, glutathione, and nicotinamide adenine dinucleotide phosphate‐dependent reductase that regulate the features of micro‐biosynthetic AuNPs. This work broadens the application of biosynthesis of inorganic materials through micro‐biosynthetic AuNPs and machine learning, which holds great promise as a tool for biomedical research.

J. Chow, P. Pérez-García, Robert F. Dierkes et al.

Microbial Biotechnology • 2022

Global economies depend on the use of fossil‐fuel‐based polymers with 360–400 million metric tons of synthetic polymers being produced per year. Unfortunately, an estimated 60% of the global production is disposed into the environment. Within this framework, microbiologists have tried to identify plastic‐active enzymes over the past decade. Until now, this research has largely failed to deliver functional biocatalysts acting on the commodity polymers such as polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), ether‐based polyurethane (PUR), polyamide (PA), polystyrene (PS) and synthetic rubber (SR). However, few enzymes are known to act on low‐density and low‐crystalline (amorphous) polyethylene terephthalate (PET) and ester‐based PUR. These above‐mentioned polymers represent >95% of all synthetic plastics produced. Therefore, the main challenge microbiologists are currently facing is in finding polymer‐active enzymes targeting the majority of fossil‐fuel‐based plastics. However, identifying plastic‐active enzymes either to implement them in biotechnological processes or to understand their potential role in nature is an emerging research field. The application of these enzymes is still in its infancy. Here, we summarize the current knowledge on microbial plastic‐active enzymes, their global distribution and potential impact on plastic degradation in industrial processes and nature. We further outline major challenges in finding novel plastic‐active enzymes, optimizing known ones by synthetic approaches and problems arising through falsely annotated and unfiltered use of database entries. Finally, we highlight potential biotechnological applications and possible re‐ and upcycling concepts using microorganisms.

B. Nataraj, S. Ali, P. Behare et al.

Microbial Cell Factories • 2020

Probiotics have several health benefits by modulating gut microbiome; however, techno-functional limitations such as viability controls have hampered their full potential applications in the food and pharmaceutical sectors. Therefore, the focus is gradually shifting from viable probiotic bacteria towards non-viable paraprobiotics and/or probiotics derived biomolecules, so-called postbiotics. Paraprobiotics and postbiotics are the emerging concepts in the functional foods field because they impart an array of health-promoting properties. Although, these terms are not well defined, however, for time being these terms have been defined as here. The postbiotics are the complex mixture of metabolic products secreted by probiotics in cell-free supernatants such as enzymes, secreted proteins, short chain fatty acids, vitamins, secreted biosurfactants, amino acids, peptides, organic acids, etc. While, the paraprobiotics are the inactivated microbial cells of probiotics (intact or ruptured containing cell components such as peptidoglycans, teichoic acids, surface proteins, etc.) or crude cell extracts (i.e. with complex chemical composition)”. However, in many instances postbiotics have been used for whole category of postbiotics and parabiotics. These elicit several advantages over probiotics like; (i) availability in their pure form, (ii) ease in production and storage, (iii) availability of production process for industrial-scale-up, (iv) specific mechanism of action, (v) better accessibility of Microbes Associated Molecular Pattern (MAMP) during recognition and interaction with Pattern Recognition Receptors (PRR) and (vi) more likely to trigger only the targeted responses by specific ligand-receptor interactions. The current review comprehensively summarizes and discussed various methodologies implied to extract, purify, and identification of paraprobiotic and postbiotic compounds and their potential health benefits.

S. De Corte, T. Hennebel, B. De Gusseme et al.

Microbial Biotechnology • 2011

While precious metals are available to a very limited extent, there is an increasing demand to use them as catalyst. This is also true for palladium (Pd) catalysts and their sustainable recycling and production are required. Since Pd catalysts exist nowadays mostly under the form of nanoparticles, these particles need to be produced in an environment‐friendly way. Biological synthesis of Pd nanoparticles (‘bio‐Pd’) is an innovative method for both metal recovery and nanocatalyst synthesis. This review will discuss the different bio‐Pd precipitating microorganisms, the applications of the catalyst (both for environmental purposes and in organic chemistry) and the state of the art of the reactors based on the bio‐Pd concept. In addition, some main challenges are discussed, which need to be overcome in order to create a sustainable nanocatalyst. Finally, some outlooks for bio‐Pd in environmental technology are presented.

Hang Xu, Yong Xiao, Meiying Xu et al.

Nanotechnology • 2018

Bimetallic nanoparticles (NPs) often exhibit improved catalytic performance due to the electronic and spatial structure changes. Herein, a novel green biosynthesis method for Pd–Pt alloy NPs using Shewanella oneidensis MR-1 was proposed. The morphology, size and crystal structure of Pd–Pt alloy NPs were studied by a suite of characterization techniques. Results showed Pd–Pt alloy NPs were successfully synthesized inside and outside the cell. The biosynthesized Pd–Pt alloy NPs were polycrystalline and face-centered-cubic structure with the particle size ranged from 3–40 nm. Furthermore, the catalytic experiment demonstrated that the Pd–Pt alloy NPs exhibited the highest performance for the catalytic reduction of nitrophenol and azo dyes compared with the as-synthesized Pd and Pt monometallic NPs. This enlarged catalytic activity resulted from the synergistic effect of Pd and Pt element. Thereby, this paper provided a simple biosynthesis method for producing bimetallic alloy nanocatalyst with superior activity for contaminant degradation.

V. Coker, J. A. Bennett, N. Telling et al.

ACS Nano • 2010

Precious metals supported on ferrimagnetic particles have a diverse range of uses in catalysis. However, fabrication using synthetic methods results in potentially high environmental and economic costs. Here we show a novel biotechnological route for the synthesis of a heterogeneous catalyst consisting of reactive palladium nanoparticles arrayed on a nanoscale biomagnetite support. The magnetic support was synthesized at ambient temperature by the Fe(III)-reducing bacterium, Geobacter sulfurreducens , and facilitated ease of recovery of the catalyst with superior performance due to reduced agglomeration (versus conventional colloidal Pd nanoparticles). Surface arrays of palladium nanoparticles were deposited on the nanomagnetite using a simple one-step method without the need to modify the biomineral surface, most likely due to an organic coating priming the surface for Pd adsorption, which was produced by the bacterial culture during the formation of the nanoparticles. A combination of EXAFS and XPS showed the Pd nanoparticles on the magnetite to be predominantly metallic in nature. The Pd(0)-biomagnetite was tested for catalytic activity in the Heck reaction coupling iodobenzene to ethyl acrylate or styrene. Rates of reaction were equal to or superior to those obtained with an equimolar amount of a commercial colloidal palladium catalyst, and near complete conversion to ethyl cinnamate or stilbene was achieved within 90 and 180 min, respectively.

Yiyan Song, Hui-jun Jiang, Bangbang Wang et al.

ACS Applied Materials & Interfaces • 2018

To tackle severe environmental pollution, a search for materials by economical and eco-friendly preparations is demanding for public health. In this study, a novel in situ method to form silver nanoparticles under mild conditions was developed using biomimetic reducing agents of polydopamine coated on the rodlike mesoporous silica of SBA-15. The synthesized SBA-15/polydopamine (PDA)/Ag nanocomposites were characterized by a combination of physicochemical and electrochemical methods. 4-Nitrophenol (4-NP) and methylene blue (MB) were used as models for the evaluation of the prepared nanocatalysts of SBA-15/PDA/Ag in which the composite exhibited enhanced catalytic performance toward degrading 4-NP in solution and MB on the membrane, respectively. Additionally, compared with that of solid core-shell SiO2/PDA/Ag, tubular SBA-15/PDA/Ag showed the prolonged inhibitory effect on microbial growth as typified by Escherichia coli (60 h), Staphylococcus aureus (36 h), and Aspergillus fumigatus (60 h), which demonstrated efficient control of silver nanoparticles release from the mesopores. The constructed dual-functional SBA-15/PDA/Ag as the long-term antimicrobial agent and the catalyst of industrial products provides an integrated nanoplatform to deal with environmental concerns.

Sagar Vikal, Y. K. Gautam, Swati Meena et al.

Nanoscale Advances • 2023

The different dyes used and discharged in industrial settings and microbial pathogenic issues have raised serious concerns about the content of bodies of water and the impact that dyes and microbes have on the environment and human health. Efficient treatment of contaminated water is thus a major challenge that is of great interest to researchers around the world. In the present work, we have fabricated functionalized silver-doped ZnO nanoparticles (Ag-doped ZnO NPs) via a hydrothermal method for wastewater treatment. X-ray photoelectron spectroscopy analysis confirmed the doping of Ag with ZnO NPs, and X-ray diffractometry analysis showed a decreasing trend in the crystallite size of the synthesized ZnO NPs with increased Ag concentration. Field emission scanning electron microscopy study of pure ZnO NPs and Ag-doped ZnO NPs revealed nanocrystal aggregates with mixed morphologies, such as hexagonal and rod-shaped structures. Distribution of Ag on the ZnO lattice is confirmed by high-resolution transmission electron microscopy analysis. ZnO NPs with 4 wt% Ag doping showed a maximum degradation of ∼95% in 1.5 h of malachite green dye (80 mg L−1) under visible light and ∼85% in 4 h under dark conditions. Up to five successive treatment cycles using the 4 wt% Ag-doped ZnO NP nanocatalyst confirmed its reusability, as it was still capable of degrading ∼86% and 82% of the dye under visible light and dark conditions, respectively. This limits the risk of nanotoxicity and aids the cost-effectiveness of the overall treatment process. The synthesized NPs showed antibacterial activity in a dose-dependent manner. The zone of inhibition of the Ag-doped ZnO NPs was higher than that of the pure ZnO NPs for all doping content. The studied Ag-doped ZnO NPs thus offer a significant eco-friendly route for the effective treatment of water contaminated with synthetic dyes and fecal bacterial load.

Sherif Elbasuney, A. M. El-Khawaga, M. A. Elsayed et al.

Scientific Reports • 2023

Hydroxyapatite (HA), the most common bioceramic material, offers attractive properties as a catalyst support. Highly crystalline mono-dispersed silver doped hydroxyapatite (Ag-HA) nanorods of 60 nm length was developed via hydrothermal processing. Silver dopant offered enhanced chemisorption for crystal violet (CV) contaminant. Silver was found to intensify negative charge on the catalyst surface; in this regard enhanced chemisorption of positively charged contaminants was accomplished. Silver dopant experienced decrease in the binding energy of valence electron for oxygen, calcium, and phosphorous using X-ray photoelectron spectroscopy XPS/ESCA; this finding could promote electron–hole generation and light absorption. Removal efficiency of Ag-HA nanocomposite for CV reached 88% after the synergistic effect with 1.0 mM H_2O_2; silver dopant could initiate H_2O_2 cleavage and intensify the release of active ȮH radicals. Whereas HA suffers from lack of microbial resistance; Ag-HA nanocomposite demonstrated high activity against Gram-positive ( S. aureus ) bacteria with zone of inhibition (ZOI) mm value of 18.0 mm , and high biofilm inhibition of 91.1%. Ag-HA nanocompsite experienced distinctive characerisitcs for utilization as green bioceramic photocatalyst for wastewater treatment.

Eréndira Garza-Duran, Gregorio Vargas-Gutiérrez, Beatriz Escobar-Morales et al.

ECS Meeting Abstracts • 2019

Microbial Fuel Cells (MFCs) are bio-electrochemical systems that use bacteria to generate bioelectricity via the oxidation of organic matter contained in a substrate (such as wastewater). However, this new method of renewable energy recovery has several technical challenges. At the cathode, for example, the Oxygen Reduction Reaction (ORR) takes place. This reaction is kinetically slow, remaining one of the main drawbacks of MFCs. Even though Pt/C nanocatalysts are widely used to promote the ORR, their performance in MFC is low due to the complex operating conditions. Therefore, alternative cathode nanocatalysts must be developed. Regarding to this issue, core-shell nanocatalysts are a promising alternative for MFCs cathodes. In this study, Fe 3 O 4 @Pt core-shell nanoparticles have been supported on N-doped and functionalized graphene (N-Gf) to obtain the Fe 3 O 4 @Pt/N-Gf nanocatalyst. First, nitrogen-doped graphene (N-G) has been synthesized by a one-step ball milling process using graphite as carbon source and melamine as both exfoliating agent and nitrogen source. Then, N-G has been functionalized by a mild acid treatment and labeled as N-Gf. Separately, the Fe 3 O 4 core has been obtained by co-precipitation reaction of Fe 2+ /Fe 3+ , using citric acid as surfactant. The Pt shell has been deposited on the core by the Bromide Anion Exchange (BAE) method, resulting in a Fe 3 O 4 @Pt nanostructure having a 1:1 Fe 3 O 4 :Pt molar ratio. The 20 wt.% Fe 3 O 4 @Pt/N-Gf core-shell nanocatalyst has been obtained also by the BAE method. Regarding N-Gf, its X-ray diffraction (XRD) pattern shows well-defined peaks at 2θ=26.5°, 44.39 and 54.4°, characteristic of graphitic structures. Moreover, its I D /I G intensity ratio calculated from Raman spectra is 1.40, which indicates a high degree of disorder in the carbon lattice, most likely due to the incorporation of N species into the structure. Additionally, an N content of 1.40 at. % has been determined by energy-dispersive X-ray spectroscopy (EDS). The XRD pattern of the magnetite phase shows reflections at 2θ= 30.44, 35.53, 43.46, 54.01, 57.79, 63.06 and 74.75°, attributed to the (220), (311), (400), (422), (511) (440) and (531) planes. The crystallite size of Fe 3 O 4 has been calculated as 9.2 nm. In addition, its Raman spectrum shows signals corresponding to the A 1g , E g and T 2g vibrational modes, characteristic of magnetite. Meanwhile, the catalytic activity of the Fe 3 O 4 @Pt/N-Gf nanocatalyst for the ORR has been evaluated by the Rotating Ring-Disk Electrode (RRDE) technique in 0.5 M H 2 SO 4 and in H 2 SO 4 having a pH=6.1. The latter is because of the pH of the pharmaceutical residual water used as substrate in the MFC. Electrochemical parameters such as hydrogen peroxide percentage, number of electrons transferred, and onset and half wave potentials has been determined. The results show that Fe 3 O 4 @Pt/N-Gf has a catalytic activity for the ORR in low and almost neutral pH comparable to that of a commercial Pt/C nanocatalyst. Therefore, these results suggest that Fe 3 O 4 @Pt/N-Gf is a promising cathode nanocatalyst for MFC applications. To the best of the authors knowledge, this is the first time that such nanostructures have been evaluated in MFCs.

Enayatollah Sheikhhosseini, Mahdieh Yahyazadehfar

Frontiers in Chemistry • 2023

In this study, the recyclable heterogeneous cluster bud Fe-MOF@Fe 3 O 4 ‘nanoflower’ composite (CB Fe-MOF@Fe 3 O 4 NFC) was successfully synthesized using Fe(NO 3 ) 3 ·9H 2 O, 8-hydroxyquinoline sulfate monohydrate, and Fe 3 O 4 nanoparticles by microwave irradiation. The as-prepared CB Fe-MOF@Fe 3 O 4 NFC was characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), vibrational sampling magnetometry (VSM), and Fourier transform infrared spectroscopy (FTIR). The CB Fe-MOF@Fe 3 O 4 NFC samples proved to have excellent catalytic activity. The activity of the CB Fe-MOF@Fe 3 O 4 NFC nanocatalyst was explored in the synthesis of dihydropyrano[3, 2-c]chromene derivatives via a three-component reaction of 4-hydroxycoumarin, malononitrile, and a wide range of aromatic aldehyde compounds. Optimized reaction conditions had several advantages, including the use of water as a green solvent, environmental compatibility, simple work-up, reusability of the catalyst, low catalyst loading, faster reaction time, and higher yields.

M. Maruthupandy, Muthusamy Anand, Govindhan Maduraiveeran et al.

Advances in Natural Sciences: Nanoscience and Nanotechnology • 2015

The extracellular appendages of bacteria (flagella) that transfer electrons to electrodes are called bacterial nanowires. This study focuses on the isolation and separation of nanowires that are attached via Pseudomonas aeruginosa bacterial culture. The size and roughness of separated nanowires were measured using transmission electron microscopy (TEM) and atomic force microscopy (AFM), respectively. The obtained bacterial nanowires indicated a clear image of bacterial nanowires measuring 16 nm in diameter. The formation of bacterial nanowires was confirmed by microscopic studies (AFM and TEM) and the conductivity nature of bacterial nanowire was investigated by electrochemical techniques. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), which are nondestructive voltammetry techniques, suggest that bacterial nanowires could be the source of electrons—which may be used in various applications, for example, microbial fuel cells, biosensors, organic solar cells, and bioelectronic devices. Routine analysis of electron transfer between bacterial nanowires and the electrode was performed, providing insight into the extracellular electron transfer (EET) to the electrode. CV revealed the catalytic electron transferability of bacterial nanowires and electrodes and showed excellent redox activities. CV and EIS studies showed that bacterial nanowires can charge the surface by producing and storing sufficient electrons, behave as a capacitor, and have features consistent with EET. Finally, electrochemical studies confirmed the development of bacterial nanowires with EET. This study suggests that bacterial nanowires can be used to fabricate biomolecular sensors and nanoelectronic devices.

Yan-Zhai Wang, Yu Shen, Lu Gao et al.

RSC Advances • 2017

Direct electricity production from biomass hydrolysate by microbial fuel cells (MFC) holds great promise for the development of the sustainable biomass industry. Shewanella oneidensis MR-1 is one of the most extensively studied model exoelectrogens in MFC. But it is still unclear whether this model strain could generate bioelectricity from biomass or not. Here, a biomass hydrolysate MFC was constructed by using S. oneidensis MR-1 and electricity output was obtained from corn straw hydrolysate. More impressively, by promoting the extracellular electron transfer efficiency with electron shuttle addition and electrode modification using the vertically aligned polyaniline (PANI) nanowire array, the electricity output from biomass hydrolystate by S. oneidensis MR-1 was greatly improved and a high energy output was obtained, i.e., ∼1260 mA m−2 current output (∼7-fold increase over that of the control) and ∼660 mW m−2 power output (∼37-fold increase over that of the control) were achieved. This work demonstrates that S. oneidensis MR-1 has great potential in electrical energy harvesting from biomass hydrolysate, which broadens the fuel spectrum of the model exoelectrogen (S. oneidensis MR-1) inoculated MFC and also provides a new opportunity for the biomass industry.

Yin Ye, Xing Liu, K. Nealson et al.

mBio • 2022

The low power generation of microbial fuel cells limits their utility. Many factors can affect power generation, including inefficient electron transfer in the anode biofilm. ABSTRACT Conductive nanowires are thought to contribute to long-range electron transfer (LET) in Geobacter sulfurreducens anode biofilms. Three types of nanowires have been identified: pili, OmcS, and OmcZ. Previous studies highlighted their conductive function in anode biofilms, yet a structural function also has to be considered. We present here a comprehensive analysis of the function of nanowires in LET by inhibiting the expression of each nanowire. Meanwhile, flagella with poor conductivity were expressed to recover the structural function but not the conductive function of nanowires in the corresponding nanowire mutant strain. The results demonstrated that pili played a structural but not a conductive function in supporting biofilm formation. In contrast, the OmcS nanowire played a conductive but not a structural function in facilitating electron transfer in the biofilm. The OmcZ nanowire played both a structural and a conductive function to contribute to current generation. Expression of the poorly conductive flagellum was shown to enhance biofilm formation, subsequently increasing current generation. These data support a model in which multiheme cytochromes facilitate long-distance electron transfer in G. sulfurreducens biofilms. Our findings also suggest that the formation of a thicker biofilm, which contributed to a higher current generation by G. sulfurreducens, was confined by the biofilm formation deficiency, and this has applications in microbial electrochemical systems. IMPORTANCE The low power generation of microbial fuel cells limits their utility. Many factors can affect power generation, including inefficient electron transfer in the anode biofilm. Thus, understanding the mechanism(s) of electron transfer provides a pathway for increasing the power density of microbial fuel cells. Geobacter sulfurreducens was shown to form a thick biofilm on the anode. Cells far away from the anode reduce the anode through long-range electron transfer. Based on their conductive properties, three types of nanowires have been hypothesized to directly facilitate long-range electron transfer: pili, OmcS, and OmcZ nanowires. However, their structural contributions to electron transfer in anode biofilm have not been elucidated. Based on studies of mutants lacking one or more of these facilitators, our results support a cytochrome-mediated electron transfer process in Geobacter biofilms and highlight the structural contribution of nanowires in anode biofilm formation, which contributes to biofilm formation and current generation, thereby providing a strategy to increase current generation.

Hanyu Wang, Fang Qian, Gongming Wang et al.

ACS Nano • 2013

Here we demonstrate the feasibility of continuous, self-sustained hydrogen gas production based solely on solar light and biomass (wastewater) recycling, by coupling solar water splitting and microbial electrohydrogenesis in a photoelectrochemical cell-microbial fuel cell (PEC-MFC) hybrid device. The PEC device is composed of a TiO2 nanowire-arrayed photoanode and a Pt cathode. The MFC is an air cathode dual-chamber device, inoculated with either Shewanella oneidensis MR-1 (batch-fed on artificial growth medium) or natural microbial communities (batch-fed on local municipal wastewater). Under light illumination, the TiO2 photoanode provided a photovoltage of ~0.7 V that shifted the potential of the MFC bioanode to overcome the potential barrier for microbial electrohydrogenesis. As a result, under light illumination (AM 1.5G, 100 mW/cm(2)) without external bias, and using wastewater as the energy source, we observed pronounced current generation as well as continuous production of hydrogen gas. The successful demonstration of such a self-biased, sustainable microbial device for hydrogen generation could provide a new solution that can simultaneously address the need of wastewater treatment and the increasing demand for clean energy.

Fang Qian, Hanyu Wang, Yichuan Ling et al.

Nano Letters • 2014

Here we report the investigation of interplay between light, a hematite nanowire-arrayed photoelectrode, and Shewanella oneidensis MR-1 in a solar-assisted microbial photoelectrochemical system (solar MPS). Whole cell electrochemistry and microbial fuel cell (MFC) characterization of Shewanella oneidensis strain MR-1 showed that these cells cultured under (semi)anaerobic conditions expressed substantial c-type cytochrome outer membrane proteins, exhibited well-defined redox peaks, and generated bioelectricity in a MFC device. Cyclic voltammogram studies of hematite nanowire electrodes revealed active electron transfer at the hematite/cell interface. Notably, under a positive bias and light illumination, the hematite electrode immersed in a live cell culture was able to produce 150% more photocurrent than that in the abiotic control of medium or dead culture, suggesting a photoenhanced electrochemical interaction between hematite and Shewanella. The enhanced photocurrent was attributed to the additional redox species associated with MR-1 cells that are more thermodynamically favorable to be oxidized than water. Long-term operation of the hematite solar MPS with light on/off cycles showed stable current generation up to 2 weeks. Fluorescent optical microscope and scanning electron microscope imaging revealed that the top of the hematite nanowire arrays were covered by a biofilm, and iron determination colorimetric assay revealed 11% iron loss after a 10-day operation. To our knowledge, this is the first report on interfacing a photoanode directly with electricigens in a MFC system. Such a system could open up new possibilities in solar-microbial device that can harvest solar energy and recycle biomass simultaneously to treat wastewater, produce electricity, and chemical fuels in a self-sustained manner.

Bo-Lin Song, Zhibin Wang, Lei Wang et al.

ACS Biomaterials Science & Engineering • 2023

The conductive microbial nanowires of Geobacter sulfurreducens serve as a model for long-range extracellular electron transfer (EET), which is considered a revolutionary "green" nanomaterial in the fields of bioelectronics, renewable energy, and bioremediation. However, there is no efficient pathway to induce microorganisms to express a large amount of microbial nanowires. Here, several strategies have been used to successfully induce the expression of microbial nanowires. Microbial nanowire expression was closely related to the concentration of electron acceptors. The microbial nanowire was around 17.02 μm in length, more than 3 times compared to its own length. The graphite electrode was used as an alternative electron acceptor by G. sulfurreducens, which obtained a fast start-up time of 44 h in microbial fuel cells (MFCs). Meanwhile, Fe(III) citrate-coated sugarcane carbon and biochar were prepared to test the applicability of these strategies in the actual microbial community. The unsatisfied EET efficiency between c-type cytochrome and extracellular insoluble electron receptors promoted the expression of microbial nanowires. Hence, microbial nanowires were proposed to be an effective survival strategy for G. sulfurreducens to cope with various environmental stresses. Based on this top-down strategy of artificially constructed microbial environmental stress, this study is of great significance for exploring more efficient methods to induce microbial nanowires expression.

I. Ng, C. Hsueh, Bor-Yann Chen

Bioresources and Bioprocessing • 2017

This review tended to decipher the expression of electron transfer capability (e.g., biofilm formation, electron shuttles, swarming motility, dye decolorization, bioelectricity generation) to microbial fuel cells (MFCs). As mixed culture were known to perform better than pure microbial cultures for optimal expression of electrochemically stable activities to pollutant degradation and bioenergy recycling, Proteus hauseri isolated as a “keystone species” to maintain such ecologically stable potential for power generation in MFCs was characterized. P. hauseri expressed outstanding performance of electron transfer (ET)-associated characteristics [e.g., reductive decolorization (RD) and bioelectricity generation (BG)] for electrochemically steered bioremediation even though it is not a nanowire-generating bacterium. This review tended to uncover taxonomic classification, genetic or genomic characteristics, enzymatic functions, and bioelectricity-generating capabilities of Proteus spp. with perspectives for electrochemical practicability. As a matter of fact, using MFCs as a tool to evaluate ET capabilities, dye decolorizer(s) could clearly express excellent performance of simultaneous bioelectricity generation and reductive decolorization (SBG and RD) due to feedback catalysis of residual decolorized metabolites (DMs) as electron shuttles (ESs). Moreover, the presence of reduced intermediates of nitroaromatics or DMs as ESs could synergistically augment efficiency of reductive decolorization and power generation. With swarming mobility, P. hauseri could own significant biofilm-forming capability to sustain ecologically stable consortia for RD and BG. This mini-review evidently provided lost episodes of great significance about bioenergy-steered applications in myriads of fields (e.g., biodegradation, biorefinery, and electro-fermentation).

Qing Yang, Y. Liu, Zetang Li et al.

Angewandte Chemie International Edition • 2012

An integrated system consisting of a carbon fiber-ZnO hybrid nanowire (NW) multicolor photodetector is driven by a microbial fuel cell (see picture; PMMA = poly(methyl methacrylate), E = electrode). The self-powered photodetector can detect at light levels of as little as nW cm(-2) intensity with a responsivity of more than 300 A W(-1).

Xiaoshuai Wu, Xiaofen Li, Zhuanzhuan Shi et al.

Materials • 2023

The sluggish electron transfer at the interface of microorganisms and an electrode is a bottleneck of increasing the output power density of microbial fuel cells (MFCs). Mo-doped carbon nanofibers (Mo-CNFs) prepared with electrostatic spinning and high-temperature carbonization are used as an anode in MFCs here. Results clearly indicate that Mo2C nanoparticles uniformly anchored on carbon nanowire, and Mo-doped anodes could accelerate the electron transfer rate. The Mo-CNF ΙΙ anode delivered a maximal power density of 1287.38 mW m−2, which was twice that of the unmodified CNFs anode. This fantastic improvement mechanism is attributed to the fact that Mo doped on a unique nanofiber surface could enhance microbial colonization, electrocatalytic activity, and large reaction surface areas, which not only enable direct electron transfer, but also promote flavin-like mediated indirect electron transfer. This work provides new insights into the application of electrospinning technology in MFCs and the preparation of anode materials on a large scale.

Ke Liu, Zhuo Ma, Xinyi Li et al.

Materials • 2023

Microbial fuel cell (MFC) performance is affected by the metabolic activity of bacteria and the extracellular electron transfer (EET) process. The deficiency of nanostructures on macroporous anode obstructs the enrichment of exoelectrogens and the EET. Herein, a N-doped carbon nanowire-modified macroporous carbon foam was prepared and served as an anode in MFCs. The anode has a hierarchical porous structure, which can solve the problem of biofilm blockage, ensure mass transport, favor exoelectrogen enrichment, and enhance the metabolic activity of bacteria. The microscopic morphology, spectroscopy, and electrochemical characterization of the anode confirm that carbon nanowires can penetrate biofilm, decrease charge resistance, and enhance long-distance electron transfer efficiency. In addition, pyrrolic N can effectively reduce the binding energy and electron transfer distance of bacterial outer membrane hemin. With this hierarchical anode, a maximum power density of 5.32 W/m3 was obtained, about 2.5-fold that of bare carbon cloth. The one-dimensional nanomaterial-modified macroporous anodes in this study are a promising strategy to improve the exoelectrogen enrichment and EET for MFCs.

K. Su, X. Yao, S. Sui et al.

Fuel Cells • 2015

Abstract The cathode electrocatalyst layers were prepared by in situ growing Pt nanowires (Pt‐NWs) in two kinds of matrixes with various Pt loadings for proton exchange membrane fuel cells (PEMFCs). Commercial carbon powder and 20 wt.% Pt/C electrocatalyst were used as the matrix material for the comparison. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), polarization curves tests, and electrochemical impedance spectroscopy (EIS) were carried out to examine the effects of the matrix materials on the Pt‐NW growing and the electrode performance. The optimum Pt‐NW loadings of 0.30 mg cm −2 in the carbon matrix (CM) and 0.20 mg cm −2 for the Pt/C matrix (PM) were obtained. The results indicated that the Pt‐NWs grown in the CM had a better crystalline, longer size length and better catalyst activity than those in the PM. The mechanism of the matrix affection is further discussed in this paper.

Alaa Abbas, Mostafa M. Omran, Antonio Marzocchella et al.

ECS Meeting Abstracts • 2025

The depletion of energy resources due to increasing human demands has become a growing concern; thus, developing sustainable energy technologies is essential. One innovative approach is soil microbial fuel cells (SMFCs), which are affordable and carbon-neutral bioremediation energy systems for polluted lands. Carbonaceous materials (CMs) are the most used materials as anodes for SMFCs, as they have reasonable conductivity, biocompatibility, and high surface area. However, decorating the CMs with metal oxide increases their specific surface area, enhancing the electrochemical behavior of the anode and enriching the exoelectrogenic microbial community. Although decorating the anodes with metal oxides, such as Co 3 O 4 , MnO 2, and Fe 2 O 3 , has enhanced the SMFCs' performance, they suffer instability through metal oxide leakage under operation conditions 1,2 . Thus, more stable metal oxides, such as bimetallic nanostructure oxides, should be investigated as anodes for SMFCs. These oxides are also expected to enhance the electron transfer rate, conductivity, and the exoelectrogenic microbial community. In this work, carbon felt (CF) is decorated with MoCoO 4 nanowires using hydrothermal synthesis. The MoCoO 4 nanowires were then coated with an electropolymerized conductive polymer as a carbon source to achieve better stability and electrical conductivity. The SEM images confirmed the formation of a homogeneous layer of MoCoO 4 nanowires, and the XRD and XPS results demonstrated their crystal structure and chemical composition. A significant improvement in the growth/adhesion of the microbial layer was observed due to the increase in surface area of the roughened electrodes, shown in SEM images, which, in turn, increased the power produced by the SMFC. Accordingly, the SMFC with maximum power was produced using MoCoO 4 @CF anode (87 mW/m 2 at 178.5 mA/m 2 ), with a power double that produced by the blank GF(44 mW/m 2 at 100 mA/m 2 ) and higher than that previously reported in the literature using Cobalt oxide nanoflakes interweaved with polyaniline (70 mW/m 2 at 143 mA/m 2 ) 1 . The SMFC that employed MoCoO 4 @CF electrodes maintained high power after fifty days of being in the soil setup, indicating the stability of the nanostructure. References: S. K. Dhillon, J. Dziegielowski, P. P. Kundu, and M. D. Lorenzo, RSC Sustain. , 1 , 310–325 (2023). D. Nosek, T. Mikołajczyk, and A. Cydzik-Kwiatkowska, International Journal of Environmental Research and Public Health , 20 , 2580 (2023).

Mingkai Liu, Peng Zhang, Z. Qu et al.

Nature Communications • 2019

Long-term stability and high-rate capability have been the major challenges of sodium-ion batteries. Layered electroactive materials with mechanically robust, chemically stable, electrically and ironically conductive networks can effectively address these issues. Herein we have successfully directed carbon nanofibers to vertically penetrate through graphene sheets, constructing robust carbon nanofiber interpenetrated graphene architecture. Molybdenum disulfide nanoflakes are then grown in situ alongside the entire framework, yielding molybdenum disulfide@carbon nanofiber interpenetrated graphene structure. In such a design, carbon nanofibers prevent the restacking of graphene sheets and provide ample space between graphene sheets, enabling a strong structure that maintains exceptional mechanical integrity and excellent electrical conductivity. The as-prepared sodium ion battery delivers outstanding electrochemical performance and ultrahigh stability, achieving a remarkable specific capacity of 598 mAh g−1, long-term cycling stability up to 1000 cycles, and an excellent rate performance even at a high current density up to 10 A g−1. Here the authors construct carbon nanofiber interpenetrated graphene architecture with in-situ grown MoS2 nanoflakes alongside the framework. The design combines exceptional mechanical integrity and excellent electronic conductivity, enabling outstanding electrochemical performance in sodium-ion battery.

Jianhao Wang, Yuan Zhao, Xiao-Yi Chen et al.

ACS Nano • 2019

Biofilm infections can induce chronic inflammation and stall normal orchestrated course of wound healing cascades. Herein pH-switchable antimicrobial hydrogel with nanofiber networks for biofilm eradication and rescuing stalled healing in chronic wound is reported based on the self-assembly of a designed octapeptide (IKFQFHFD) at neutral pH. This hydrogel is biocompatible and exhibits acidic pH (pathological environment of infected chronic wounds)-switchable broad-spectrum antimicrobial effect via a mechanism involving cell wall and membrane disruption. The antimicrobial activity of hydrogel is derived from its acidic pH-dependent nanofiber networks destabilization and activated release of IKFQFHFD which is antimicrobial only at acidic pH due to the antimicrobial peptides-like molecular structure. In addition, supramolecular nanofiber networks loaded with drugs of cypate (photothermal agent) and proline (procollagen component) are further developed. In vitro experiments show that loaded drugs exhibit acidic pH (pH ~5.5)-responsive release profiles, and synergistic biofilm eradication and subsequent healing cascades activation of cells proliferation is achieved based on the supramolecular nanofiber networks. Remarkably, the nanofiber networks of hydrogel enables in vivo complete healing of MRSA biofilm-infected wound in diabetic mice within 20 days, showing great potential as promising chronic wound dressings. The proposed synergistic strategy for eradicating biofilm and activating subsequent healing cascades may offer a powerful modality for the management of clinical chronic wounds.

Xiao Peng, Kai Dong, Cuiying Ye et al.

Science Advances • 2020

A breathable, biodegradable, antibacterial, and self-powered skin is developed. Mimicking the comprehensive functions of human sensing via electronic skins (e-skins) is highly interesting for the development of human-machine interactions and artificial intelligences. Some e-skins with high sensitivity and stability were developed; however, little attention is paid to their comfortability, environmental friendliness, and antibacterial activity. Here, we report a breathable, biodegradable, and antibacterial e-skin based on all-nanofiber triboelectric nanogenerators, which is fabricated by sandwiching silver nanowire (Ag NW) between polylactic-co-glycolic acid (PLGA) and polyvinyl alcohol (PVA). With micro-to-nano hierarchical porous structure, the e-skin has high specific surface area for contact electrification and numerous capillary channels for thermal-moisture transfer. Through adjusting the concentration of Ag NW and the selection of PVA and PLGA, the antibacterial and biodegradable capability of e-skins can be tuned, respectively. Our e-skin can achieve real-time and self-powered monitoring of whole-body physiological signal and joint movement. This work provides a previously unexplored strategy for multifunctional e-skins with excellent practicability.

Tao Li, Mingchao Sun, Shaohua Wu

Nanomaterials • 2022

Electrospun nanofiber materials have been considered as advanced dressing candidates in the perspective of wound healing and skin regeneration, originated from their high porosity and permeability to air and moisture, effective barrier performance of external pathogens, and fantastic extracellular matrix (ECM) fibril mimicking property. Gelatin is one of the most important natural biomaterials for the design and construction of electrospun nanofiber-based dressings, due to its excellent biocompatibility and biodegradability, and great exudate-absorbing capacity. Various crosslinking approaches including physical, chemical, and biological methods have been introduced to improve the mechanical stability of electrospun gelatin-based nanofiber mats. Some innovative electrospinning strategies, including blend electrospinning, emulsion electrospinning, and coaxial electrospinning, have been explored to improve the mechanical, physicochemical, and biological properties of gelatin-based nanofiber mats. Moreover, numerous bioactive components and therapeutic agents have been utilized to impart the electrospun gelatin-based nanofiber dressing materials with multiple functions, such as antimicrobial, anti-inflammation, antioxidation, hemostatic, and vascularization, as well as other healing-promoting capacities. Noticeably, electrospun gelatin-based nanofiber mats integrated with specific functions have been fabricated to treat some hard-healing wound types containing burn and diabetic wounds. This work provides a detailed review of electrospun gelatin-based nanofiber dressing materials without or with therapeutic agents for wound healing and skin regeneration applications.

Elahe Fallah Talooki, M. Ghorbani, M. Rahimnejad et al.

Environmental Technology • 2023

ABSTRACT Photo-assisted microbial fuel cells (PMFCs) are novel bioelectrochemical systems that employ light to harvest bioelectricity and efficient contaminant reduction. In this study, the impact of different operational conditions on the electricity generation outputs in a photoelectrochemical double chamber configuration Microbial fuel cell using a highly useful photocathode are evaluated and their trends are compared with the photoreduction efficiency trends. As a photocathode, a binder-free photo electrode decorated with dispersed polyaniline nanofiber (PANI)−cadmium sulphide Quantum Dots (QDs) is prepared here to catalyse the chromium (VI) reduction reaction in a cathode chamber with an improvement in power generation performance. Bioelectricity generation is examined in various process conditions like photocathode materials, pH, initial concentration of catholyte, illumination intensity and time of illumination. Results show that, despite the harmful effect of the initial contaminant concentration on the reduction efficiency of the contaminant, this parameter exhibits a superior ability for improving the power generation efficiency in a Photo-MFC. Furthermore, the calculated power density under higher light irradiation intensity has experienced a significant increase, which is due to an increment in the number of photons produced and an increase in their chance of reaching the electrodes surface. On the other hand, additional results indicate that the power generation decreases with the rise of pH and has witnessed the same trend as the photoreduction efficiency. GRAPHICAL ABSTRACT

Sunshine Holmberg, M. Rodríguez-Delgado, Ross D. Milton et al.

ACS Catalysis • 2015

In this study, the bioelectrocatalytic reduction of molecular oxygen by two highly thermostable laccase isoforms from a native strain of Pycnoporus sanguineus CS43 were evaluated and compared to commercially available laccase from Trametes versicolor (TvL). The laccase isoforms (LAC1 and LAC2) and TvL laccase were immobilized by orientation onto anthracene-modified multiwalled carbon nanotubes (AC-MWCNT), which were subsequently immobilized onto carbon nanofiber mat electrodes fabricated using a carbon MEMS (C-MEMS) process. The performances of the isoforms were evaluated at differing pHs, temperatures, and with various inhibitors under hydrodynamic and hydrostatic conditions. Both LAC1 and LAC2 had onset potentials of over +650 mV vs Ag/AgCl at pH 4.0, which are among the highest reported to date for any laccase bioelectrode. High current densities were also obtained, producing 825 ± 88 μA/cm2 and 1220 ± 106 μA/cm2 with LAC1 and LAC2, respectively. The bioelectrodes also demonstrated remarkable operation...

Hamza Abdalla Yones

International Journal of Electrochemical Science • 2021

MgO decorated carbon nanofiber (MgO@CNFs) nanocomposite was prepared by electrospinning and carbonization method. Then the nanocomposite was casted on carbon ionic liquid electrode (CILE) with the following immobilization of hemoglobin (Hb) by Nafion polymer film. UV-Vis spectroscopic results showed that Hb maintained its original structure without changing after mixing with nanocomposite. The resultant MgO@CNFs modified electrode provided a favorable microenvironment for Hb to realize electrochemistry and the bioelectrochemical properties of Hb were studied in details. The results showed that MgO@CNFs nanocomposite on electrode improved Hb loading amount with its bioactivity maintained and electron transfer rate fasten, which was attributed to big specific interface area, excellent biocompatibility and high conductivity. Nafion/Hb/MgO@CNFs/CILE also displayed high electrocatalytic activity to the electroreduction of trichloroacetic acid. This study provided a novel way for the fabrication of the nanostructured biosurfaces for electrochemical biosensors.

Kyoung-im Kim, Dong-Ae Kim, K. Patel et al.

Scientific Reports • 2019

Although PMMA-based biomaterials are widely used in clinics, a major hurdle, namely, their poor antimicrobial (i.e., adhesion) properties, remains and can accelerate infections. In this study, carboxylated multiwalled carbon nanotubes (CNTs) were incorporated into poly(methyl methacrylate) (PMMA) to achieve drug-free antimicrobial adhesion properties. After characterizing the mechanical/surface properties, the anti-adhesive effects against 3 different oral microbial species (Staphylococcus aureus, Streptococcus mutans, and Candida albicans) were determined for roughened and highly polished surfaces using metabolic activity assays and staining for recognizing adherent cells. Carboxylated multiwalled CNTs were fabricated and incorporated into PMMA. Total fracture work was enhanced for composites containing 1 and 2% CNTs, while other mechanical properties were gradually compromised with the increase in the amount of CNTs incorporated. However, the surface roughness and water contact angle increased with increasing CNT incorporation. Significant anti-adhesive effects (35~95%) against 3 different oral microbial species without cytotoxicity to oral keratinocytes were observed for the 1% CNT group compared to the PMMA control group, which was confirmed by microorganism staining. The anti-adhesive mechanism was revealed as a disconnection of sequential microbe chains. The drug-free antimicrobial adhesion properties observed in the CNT-PMMA composite suggest the potential utility of CNT composites as future antimicrobial biomaterials for preventing microbial-induced complications in clinical settings (i.e., Candidiasis).

S. Vasquez, M. C. Angeli, Andrea Polo et al.

Scientific Reports • 2024

In vitro simulators of the human gastrointestinal (GI) tract are remarkable technological platforms for studying the impact of food on the gut microbiota, enabling continuous and real-time monitoring of key biomarkers. However, comprehensive real-time monitoring of gaseous biomarkers in these systems is required with a cost-effective approach, which has been challenging to perform experimentally to date. In this work, we demonstrate the integration and in-line use of carbon nanotube (CNT)-based chemiresitive gas sensors coated with a thin polydimethylsiloxane (PDMS) membrane for the continuous monitoring of gases within the Simulator of the Human Microbial Ecosystem (SHIME). The findings demonstrate the ability of the gas sensor to continuously monitor the different phases of gas production in this harsh, anaerobic, highly humid, and acidic environment for a long exposure time (16 h) without saturation. This establishes our sensor platform as an effective tool for real-time monitoring of gaseous biomarkers in in vitro systems like SHIME.

Huanan Wu, Min Lu, Lin Guo et al.

Water Science and Technology • 2014

Polyelectrolyte–single wall carbon nanotube (SCNT) composites are prepared by a solution-based method and used as metal-free cathode catalysts for oxygen reduction reaction (ORR) in air-cathode microbial fuel cells (MFCs). In this study, two types of polyelectrolytes, polydiallyldimethylammonium chloride (PDDA) and poly[bis(2-chloroethyl)ether-alt-1,3-bis[3-(dimethylamino)propyl]urea] (PEPU) are applied to decorate the SCNTs and the resulting catalysts exhibit remarkable catalytic ability toward ORR in MFC applications. The enhanced catalytic ability could be attributed to the positively charged quaternary ammonium sites of polyelectrolytes, which increase the oxygen affinity of SCNTs and reduce activation energy in the oxygen reduction process. It is also found that PEPU–SCNT composite-based MFCs show efficient performance with maximum power density of 270.1 mW m−2, comparable to MFCs with the benchmark Pt/C catalyst (375.3 mW m−2), while PDDA–SCNT composite-based MFCs produce 188.9 mW m−2. These results indicate that PEPU–SCNT and PDDA–SCNT catalysts are promising candidates as metal-free cathode catalysts for ORR in MFCs and could facilitate MFC scaling up and commercialization.