Citric acid cycle biomimic on a carbon electrode

A Mitochondrial Nanoguard Modulates Redox Homeostasis and Bioenergy Metabolism in Diabetic Peripheral Neuropathy

As a major late complication of diabetes, diabetic peripheral neuropathy (DPN) is the primary reason for amputation. Nevertheless, there are no wonder drugs available. Regulating dysfunctional mitochondria is a key therapeutic target for DPN. Resveratrol (RSV) is widely proven to guard mitochondria, yet the unsatisfactory bioavailability restricts its clinical application. Tetrahedral framework nucleic acids (tFNAs) are promising carriers due to their excellent cell entrance efficiency, biological safety, and structure editability. Here, RSV was intercalated into tFNAs to form the tFNAs-RSV complexes. tFNAs-RSV achieved enhanced stability, bioavailability, and biocompatibility compared with tFNAs and RSV alone. With its treatment, reactive oxygen species (ROS) production was minimized and reductases were activated in an in vitro model of DPN. Besides, respiratory function and adenosine triphosphate (ATP) production were enhanced. tFNAs-RSV also exhibited favorable therapeutic effects on sensory dysfunction, neurovascular deterioration, demyelination, and neuroapoptosis in DPN mice. Metabolomics analysis revealed that redox regulation and energy metabolism were two principal mechanisms that were impacted during the process. Comprehensive inspections indicated that tFNAs-RSV inhibited nitrosation and oxidation and activated reductase and respiratory chain. In sum, tFNAs-RSV served as a mitochondrial nanoguard (mito-guard), representing a viable drilling target for clinical drug development of DPN.

Metabolomics reveals the mechanism of polyethylene microplastic toxicity to Daphnia magna

Microplastic exposure leads to various toxic effects in Daphnia magna; however, the effects of microplastics on the metabolic processes in D. magna and the corresponding molecular toxicity mechanisms remain unclear. In the present study, the effects of acute exposure to polyethylene microplastics with different particle sizes (20 μm [MPs-20] and 30 μm [MPs-30]) on metabolites in D. magna and the mechanisms of toxicity were investigated by combining metabolomics and traditional toxicology techniques. Exposure to both MPs-20 and MPs-30 resulted in significant accumulation of microplastics in the gut of D. magna and significantly reduced D. magna survival and heart rate. Metabolomics analysis revealed that MPs-20 and MPs-30 induced significant changes in up to 88 and 91 differential metabolites, respectively, and collectively induced significant changes in 75 metabolites in D. magna. Among lipid metabolites, MPs-20 specifically downregulated phosphatidylcholine and upregulated phosphatidylethanolamine, which mainly affected phospholipid metabolism, whereas MPs-30 specifically downregulated amino acid metabolites l-glutamine, l-glutamate and malic acid, which mainly interfered with energy metabolism. The results of this study provide novel insights into the mechanism of effects of microplastics on metabolic processes in D. magna.

Dynamic behavior of liquid droplets with enzyme compartmentalization triggered by sequential glycolytic enzyme reactions

Dynamic droplet formation via liquid-liquid phase separation (LLPS) is believed to be involved in the regulation of various biological processes. Here, a model LLPS system coupled with a sequential glycolytic enzymatic reaction was developed to reproduce the dynamic control of liquid droplets; (i) the droplets, which consist of poly-L-lysine and nucleotides, compartmentalize two different enzymes (hexokinase and glucose-6-phosphate dehydrogenase) individually, accelerating the overall reaction, and (ii) each enzymatic reaction triggers the formation, dissolution and long-term retention of the droplets by converting the scaffold nucleotides. This model system will offer a new aspect of enzymes associated with LLPS in living cells.

Carbon Nanotube PtSn Nanoparticles for Enhanced Complete Biocatalytic Oxidation of Ethylene Glycol in Biofuel Cells

We report a hybrid catalytic system containing metallic PtSn nanoparticles deposited on multiwalled carbon nanotubes (Pt₆₅Sn₃₅/MWCNTs), prepared by the microwave-assisted method, coupled to the enzyme oxalate oxidase (OxOx) for complete ethylene glycol (EG) electrooxidation. Pt₆₅Sn₃₅/MWCNTs, without OxOx, showed good electrochemical activity toward EG oxidation and all the byproducts. Pt₆₅Sn₃₅/MWCNTs cleaved the glyoxilic acid C-C bond, producing CO₂ and formic acid, which was further oxidized at the electrode. Concerning EG oxidation, the catalytic activity of the hybrid system (Pt₆₅Sn₃₅/MWCNTs+OxOx) was twice the catalytic activity of Pt₆₅Sn₃₅/MWCNTs. Long-term electrolysis revealed that Pt₆₅Sn₃₅/MWCNTs+OxOx was much more active for EG oxidation than Pt₆₅Sn₃₅/MWCNTs: the charge increased by 65%. The chromatographic results proved that Pt₆₅Sn₃₅/MWCNTs+OxOx collected all of the 10 electrons per molecule of the fuel and was able to catalyze EG oxidation to CO₂ due to the associative oxidation between the metallic nanoparticles and the enzymatic pathway. Overall, Pt₆₅Sn₃₅/MWCNTs+OxOx proved to be a promising system to enhance the development of enzymatic biofuel cells for further application in the bioelectrochemistry field.

Computational investigation, comparative approaches, molecular structural, vibrational spectral, non-covalent interaction (NCI), and electron excitations analysis of benzodiazepine derivatives

The present work explores the structural parameters and vibrational frequencies as well as molecular interactions of benzodiazepine derivatives, such as clothiapine (CT), clozapine (CZ), and loxapine (LX). Employing fitting experimental data to theoretical results is used to assess the structural parameters of heading composites. The main assignment is passed out according to the overall distribution of energy of the vibrational modes. From the hyper-conjugative interaction, the permanency of the structure had been predicted through natural bond orbital analysis; it is also used to identify the bonding and antibonding regions of the molecules. Moreover, electrostatic potential (ESP), density of states (DOS), and charge transfer occurring of the molecule among HOMO as well as LUMO energy were calculated and presented; utilizing electron localized field (ELF), localized orbital locator (LOL), and reduced density gradient (RDG), the chemical interactive regions are found. Additionally, mean polarizability (α_tot), the first-order hyperpolarizability (β_tot), and softness and hardness of the entitled compounds were also performed. The interaction between protein-ligand was also predicted by docking studies.

Toxicological effects of microplastics in Litopenaeus vannamei as indicated by an integrated microbiome, proteomic and metabolomic approach

Microplastics (MPs) are a hazardous pollutant of world concern that threaten aquatic organisms and ecosystems. In this study, we chose the worldwide-distributed shrimp Litopenaeus vannamei as a model and investigated the toxicological effects of five types of MPs on L. vannamei using several omics approaches. After 14 days of exposure to MPs, obvious intestinal microbiota variation was observed, such as increased abundances of Bacteroidetes and Proteobacteria and a decreased abundance of Firmicutes. Specifically, MPs induced several putative opportunistic pathogens and reduced lactic acid- and short-chain fatty acid-producing bacteria. Alternatively, MPs altered haemolymph proteome profiles, but the five types of MPs had different effects on the enriched pathways and the expression of immune-related proteins. Furthermore, MPs also caused haemolymph metabolite variation, especially in amino acid and alpha-linolenic acid metabolism, and 28 differential metabolites were altered in the five MP-treated groups. Changes in intestinal bacteria were correlated with the haemolymph proteins and metabolites of the shrimp. Overall, these results reveal the toxicological effects of MPs on the intestinal microbiota and the host's immunity and metabolism in shrimp.

Ethanol Biofuel Cells: Hybrid Catalytic Cascades as a Tool for Biosensor Devices

Biofuel cells use chemical reactions and biological catalysts (enzymes or microorganisms) to produce electrical energy, providing clean and renewable energy. Enzymatic biofuel cells (EBFCs) have promising characteristics and potential applications as an alternative energy source for low-power electronic devices. Over the last decade, researchers have focused on enhancing the electrocatalytic activity of biosystems and on increasing energy generation and electronic conductivity. Self-powered biosensors can use EBFCs while eliminating the need for an external power source. This review details improvements in EBFC and catalyst arrangements that will help to achieve complete substrate oxidation and to increase the number of collected electrons. It also describes how analytical techniques can be employed to follow the intermediates between the enzymes within the enzymatic cascade. We aim to demonstrate how a high-performance self-powered sensor design based on EBFCs developed for ethanol detection can be adapted and implemented in power devices for biosensing applications.

Multi-Substrate Biofuel Cell Utilizing Glucose, Fructose and Sucrose as the Anode Fuels

A significant problem still exists with the low power output and durability of the bioelectrochemical fuel cells. We constructed a fuel cell with an enzymatic cascade at the anode for efficient energy conversion. The construction involved fabrication of the flow-through cell by three-dimensional printing. Gold nanoparticles with covalently bound naphthoquinone moieties deposited on cellulose/polypyrrole (CPPy) paper allowed us to significantly improve the catalysis rate, both at the anode and cathode of the fuel cell. The enzymatic cascade on the anode consisted of invertase, mutarotase, Flavine Adenine Dinucleotide (FAD)-dependent glucose dehydrogenase and fructose dehydrogenase. The multi-substrate anode utilized glucose, fructose, sucrose, or a combination of them, as the anode fuel and molecular oxygen were the oxidant at the laccase-based cathode. Laccase was adsorbed on the same type of naphthoquinone modified gold nanoparticles. Interestingly, the naphthoquinone modified gold nanoparticles acted as the enzyme orienting units and not as mediators since the catalyzed oxygen reduction occurred at the potential where direct electron transfer takes place. Thanks to the good catalytic and capacitive properties of the modified electrodes, the power density of the sucrose/oxygen enzymatic fuel cells (EFC) reached 0.81 mW cm-2, which is beneficial for a cell composed of a single cathode and anode.

Microfluidic screening system based on boron-doped diamond electrodes and dielectrophoretic sorting for directed evolution of NAD(P)-dependent oxidoreductases

We report the development of a micro total analysis system (μTAS) based on electrochemical measurements and dielectrophoretic sorting for screening of NAD(P)-dependent oxidoreductases. In this system, the activity of enzymes immobilized on microbeads, together with their encoding DNA, can be measured with a boron-doped diamond (BDD) electrode in each compartment (∼30 nL) of the microfluidic system. The 30 nL droplets containing microbead-displayed genes of enzymes with higher activity can then be recovered by dielectrophoretic sorting. Previously, we developed the NAD(P)H-measuring device containing the BDD electrode for high-throughput measurement of the activity of NAD(P)-dependent oxidoreductases. In this study, we fabricated an encapsulating device and a droplet-sorting device for nanoliter-size droplets, for the first time, and then combined these three devices to construct a μTAS for directed evolution of NAD(P)-dependent oxidoreductases. We confirmed that this system works by proof-of-principle experiments and successfully applied this system for screening of randomized libraries of NAD-dependent dehydrogenases.

Electrochemical biosensors: perspective on functional nanomaterials for on-site analysis

BACKGROUND

The electrochemical biosensor is one of the typical sensing devices based on transducing the biochemical events to electrical signals. In this type of sensor, an electrode is a key component that is employed as a solid support for immobilization of biomolecules and electron movement. Thanks to numerous nanomaterials that possess the large surface area, synergic effects are enabled by improving loading capacity and the mass transport of reactants for achieving high performance in terms of analytical sensitivity.

MAIN BODY

We categorized the current electrochemical biosensors into two groups, carbon-based (carbon nanotubes and graphene) and non-carbon-based nanomaterials (metallic and silica nanoparticles, nanowire, and indium tin oxide, organic materials). The carbon allotropes can be employed as an electrode and supporting scaffolds due to their large active surface area as well as an effective electron transfer rate. We also discussed the non-carbon nanomaterials that are used as alternative supporting components of the electrode for improving the electrochemical properties of biosensors.

CONCLUSION

Although several functional nanomaterials have provided the innovative solid substrate for high performances, developing on-site version of biosensor that meets enough sensitivity along with high reproducibility still remains a challenge. In particular, the matrix interference from real samples which seriously affects the biomolecular interaction still remains the most critical issues that need to be solved for practical aspect in the electrochemical biosensor.

Bioinspired architecture of a hybrid bifunctional enzymatic/organic electrocatalyst for complete ethanol oxidation

Electrochemical ethanol oxidation was performed at an innovative hybrid architecture electrode containing TEMPO-modified linear poly(ethylenimine) (LPEI) and oxalate oxidase (OxOx) immobilized on carboxylated multi-walled carbon nanotubes (MWCNT-COOH). On the basis of chromatographic results, the catalytic hybrid electrode system completely oxidized ethanol to CO₂ after 12 h of electrolysis. The fact that the developed system can catalyze ethanol electrooxidation at a carbon electrode confirms that organic oxidation catalysts combined with enzymatic catalysts allow up to 12 electrons to be collected per fuel molecule. The Faradaic efficiency of the hybrid system investigated herein lies above 87%. The combination of OxOx with TEMPO-LPEI to obtain a novel hybrid anode to oxidize ethanol to carbon dioxide constitutes a simple methodology with useful application in the development of enzymatic biofuel cells.

Tackling the Challenges of Enzymatic (Bio)Fuel Cells

The ever-increasing demands for clean and sustainable energy sources combined with rapid advances in biointegrated portable or implantable electronic devices have stimulated intensive research activities in enzymatic (bio)fuel cells (EFCs). The use of renewable biocatalysts, the utilization of abundant green, safe, and high energy density fuels, together with the capability of working at modest and biocompatible conditions make EFCs promising as next generation alternative power sources. However, the main challenges (low energy density, relatively low power density, poor operational stability, and limited voltage output) hinder future applications of EFCs. This review aims at exploring the underlying mechanism of EFCs and providing possible practical strategies, methodologies and insights to tackle these issues. First, this review summarizes approaches in achieving high energy densities in EFCs, particularly, employing enzyme cascades for the deep/complete oxidation of fuels. Second, strategies for increasing power densities in EFCs, including increasing enzyme activities, facilitating electron transfers, employing nanomaterials, and designing more efficient enzyme-electrode interfaces, are described. The potential of EFCs/(super)capacitor combination is discussed. Third, the review evaluates a range of strategies for improving the stability of EFCs, including the use of different enzyme immobilization approaches, tuning enzyme properties, designing protective matrixes, and using microbial surface displaying enzymes. Fourth, approaches for the improvement of the cell voltage of EFCs are highlighted. Finally, future developments and a prospective on EFCs are envisioned.

Tools and strategies for constructing cell-free enzyme pathways

Single enzyme systems or engineered microbial hosts have been used for decades but the notion of assembling multiple enzymes into cell-free synthetic pathways is a relatively new development. The extensive possibilities that stem from this synthetic concept makes it a fast growing and potentially high impact field for biomanufacturing fine and platform chemicals, pharmaceuticals and biofuels. However, the translation of individual single enzymatic reactions into cell-free multi-enzyme pathways is not trivial. In reality, the kinetics of an enzyme pathway can be very inadequate and the production of multiple enzymes can impose a great burden on the economics of the process. We examine here strategies for designing synthetic pathways and draw attention to the requirements of substrates, enzymes and cofactor regeneration systems for improving the effectiveness and sustainability of cell-free biocatalysis. In addition, we comment on methods for the immobilisation of members of a multi-enzyme pathway to enhance the viability of the system. Finally, we focus on the recent development of integrative tools such as in silico pathway modelling and high throughput flux analysis with the aim of reinforcing their indispensable role in the future of cell-free biocatalytic pathways for biomanufacturing.

An in vitro synthetic biology platform for emerging industrial biomanufacturing: Bottom-up pathway design

Although most in vitro (cell-free) synthetic biology projects are usually used for the purposes of fundamental research or the formation of high-value products, in vitro synthetic biology platform, which can implement complicated biochemical reactions by the in vitro assembly of numerous enzymes and coenzymes, has been proposed for low-cost biomanufacturing of bioenergy, food, biochemicals, and nutraceuticals. In addition to the most important advantage-high product yield, in vitro synthetic biology platform features several other biomanufacturing advantages, such as fast reaction rate, easy product separation, open process control, broad reaction condition, tolerance to toxic substrates or products, and so on. In this article, we present the basic bottom-up design principles of in vitro synthetic pathway from basic building blocks-BioBricks (thermoenzymes and/or immobilized enzymes) to building modules (e.g., enzyme complexes or multiple enzymes as a module) with specific functions. With development in thermostable building blocks-BioBricks and modules, the in vitro synthetic biology platform would open a new biomanufacturing age for the cost-competitive production of biocommodities.

Additive-induced aggregate changes of two structurally similar dyes in aqueous solutions: A comparative photophysical study

Absorption and emission spectral characteristics of the two structurally similar phenothiazine dyes, azure B and toluidine blue, in aqueous solutions of the two sets of molecular additives (ureas and monosaccharides) were studied as a function of the dye and additive concentrations. The absorption spectra of the dyes were also studied in pure tetramethylurea with an aprotic nature. The spectral data were analyzed using DECOM Program. The dimer structure of the interacting molecules in these dyes was discussed using the exciton model. The urea class of additives was found to act as water structure-breakers over the range of studied concentration. The carbohydrate additives were found to act as water structure-breakers at low concentrations. However, the water structure breaking process may be disfavored by the additive-additive interactions at higher concentrations. It can be concluded that at low additive concentrations, the main driving force for breaking the dye association is water-additive interaction, which disrupts the water hydrogen bonds induced by the additives. However, at the high additive concentrations, the different phenomena including additive-additive and additive-dye interactions can change the structure, strength, and aggregative properties of the dyes. Finally, the urea in water induces noticeably fluorescence quenching in emission spectra of both the dyes.

A more acceptable endoluminal implantation for remotely monitoring ingestible sensors anchored to the stomach wall

Several types of implant devices have been proposed and introduced into healthcare and telemedicine systems for monitoring physiological parameters, sometimes for very long periods of time. To our disappointment, most of the devices are implanted invasively and by surgery. We often have to surgically remove such devices after they have finished their mission or before the battery becomes worn out. Wearable devices have the possibility to become new modalities for monitoring vital parameters less-invasively. However, for round-the-clock monitoring of data from sensors over long periods of time, it would be better to put them inside the body to avoid causing inconvenience to patients in their daily lives. This study tested a less invasive endoluminal approach and innovative tools (developed during our research into therapeutic capsule endoscopy) for remotely anchoring ingestible sensors to the stomach wall. Preliminary investigations are also described about wireless communication (NFC, ZigBee, and Bluetooth) for low power consumption and inductive extracorporeal power feeding wirelessly to the circuits in a phantom lined with swine gastric mucosa. Electrocardiogram and pH were monitored and those parameters were successfully transmitted by wireless communication ICs to the Internet via a portable device.

Enhancement of ethanol-oxygen biofuel cell output using a CNT based nano-composite as bioanode

The present research, describes preparation and application of a novel bioanode for ethanol-oxygen biofuel cells. We applied an enzyme based nanocomposite consisting of polymethylene green as electron transfer mediator, carboxylated-multiwall carbon nanotubes as electron transfer accelerator, alcohol dehydrogenase as biocatalyst and polydiallyldimethylammonium chloride as supporting agent. In the presence of β-nicotinamide adenine dinucleotide as cofactor, and ethanol as fuel, the feasibility of the bioanode for increasing the power was evaluated under the ambient conditions. In the optimum conditions the biofuel cell produced the power density of 1.713 mW cm(-2) and open circuit voltage of 0.281 V.

Oxidative bioelectrocatalysis: From natural metabolic pathways to synthetic metabolons and minimal enzyme cascades

Anodic bioelectrodes for biofuel cells are more complex than cathodic bioelectrodes for biofuel cells, because laccase and bilirubin oxidase can individually catalyze four electron reduction of oxygen to water, whereas most anodic enzymes only do a single two electron oxidation of a complex fuel (i.e. glucose oxidase oxidizing glucose to gluconolactone while generating 2 electrons of the total 24 electrons), so enzyme cascades are typically needed for complete oxidation of the fuel. This review article will discuss the lessons learned from natural metabolic pathways about multi-step oxidation and how those lessons have been applied to minimal or artificial enzyme cascades. This article is part of a Special Issue entitled Biodesign for Bioenergetics--the design and engineering of electronic transfer cofactors, proteins and protein networks, edited by Ronald L. Koder and J.L. Ross Anderson.

Enhanced activity of acetyl CoA synthetase adsorbed on smart microgel: an implication for precursor biosynthesis

Acetyl coenzyme A (acetyl CoA) is an essential precursor molecule for synthesis of metabolites such as the polyketide-based drugs (tetracycline, mitharamycin, Zocor, etc.) fats, lipids, and cholesterol. Acetyl CoA synthetase (Acs) is one of the enzymes that catalyzes acetyl CoA synthesis, and this enzyme is essentially employed for continuous supply of the acetyl CoA for the production of these metabolites. To achieve reusable and a more robust entity of the enzyme, we carried out the immobilization of Acs on poly(N-isopropylacrylamide)-poly(ethylenimine) (PNIPAm-PEI) microgels via adsorption. Cationic PNIPAm-PEI microgel was synthesized by one-step graft copolymerization of NIPAm and N,N-methylene bis-acrylamide (MBA) from PEI. Adsorption studies of Acs on microgel indicated high binding of enzymes, with a maximum binding capacity of 286 μg/mg of microgel for Acs was achieved. The immobilized enzymes showed improved biocatalytic efficiency over free enzymes, beside this, the reaction parameters and circular dichroism (CD) spectroscopy studies indicated no significant changes in the enzyme structure after immobilization. This thoroughly characterized enzyme bioconjugate was further immobilized on an ultrathin membrane to assess the same reaction in flow through condition. Bioconjugate was covalently immobilized on a thin layer of preformed microgel support upon polyethylene terephthalate (PET) track etched membrane. The prepared membrane was used in a dead end filtration device to monitor the bioconversion efficiency and operational stability of cross-linked bioconjugate. The membrane reactor showed consistent operational stability and maintained >70% of initial activity after 7 consecutive operation cycles.

Recombinant oxalate decarboxylase: enhancement of a hybrid catalytic cascade for the complete electro-oxidation of glycerol

The complete electro-oxidation of glycerol to CO₂is performed through an electro-oxidation cascade using a hybrid catalytic system combining an organic oxidation catalyst, 4-amino-TEMPO and a recombinant enzyme, oxalate decarboxylase fromBacillus subtilis.

Smart core-shell microgel support for acetyl coenzyme A synthetase: a step toward efficient synthesis of polyketide-based drugs

The flexibility in tuning the structure and charge properties of PNIPAm microgels during their synthesis makes them a suitable choice for various biological applications. Two-step free radical polymerization, a common method employed for synthesis of core-shell microgel has been well adopted to obtain cationic poly(N-isopropylacrylamide-aminoethyl methacrylate) (PNIPAm-AEMA) shell and PNIPAm core. Scanning electron microscopy (SEM), dynamic light scattering (DLS), zeta potential, and ninhydrin assay suggests nearly monodispersed particles of cationic nature. Amino groups on the microgel provides suitable attachment point for covalent immobilization of acetyl coenzyme A synthetase (Acs) via 1-ethyl-3-(3-N,N- dimethylaminopropyl) carbodiimide (EDC) chemistry. On immobilization, 61.55% of initial activity of Acs has been retained, while Michaelis-Menten kinetics of the immobilized Acs indicates identical K(m) (Michaelis constant) but decrease in the V(max) (maximum substrate conversion rate) compared to free enzyme. Immobilized Acs shows an improvement in activity at wide temperature and pH range and also demonstrates good thermal, storage, and operational stability. The Acs-microgel bioconjugate has been successfully reused for four consecutive operation cycles with more than 50% initial activity.

On the direct electron transfer, sensing, and enzyme activity in the glucose oxidase/carbon nanotubes system

The signal transduction and enzyme activity were investigated in biosensors based on the glucose oxidase (GOx) and carbon nanotubes (CNT) embedded in a bioadhesive film of chitosan (CHIT). The voltammetric studies showed that, regardless of CHIT matrix, the GOx adsorbed on CNT yielding a pair of surface-confined current peaks at -0.48 V. The anodic peak did not increase in the presence of glucose in an O2-free solution indicating the lack of direct electron transfer (DET) between the enzymatically active GOx and CNT. The voltammetric peaks were due to the redox of enzyme cofactor flavin adenine dinucleotide (FAD), which was not the part of active enzyme. The presented data suggest that DET may not be happening for any type of GOx/CNT-based sensor. The biosensor was sensitive to glucose in air-equilibrated solutions indicating the O2-mediated enzymatic oxidation of glucose. The signal transduction relied on the net drop in a biosensor current that was caused by a decrease in a 4-e(-) O2 reduction current and an increase in a 2-e(-) H2O2 reduction current. The enzyme assays showed that CNT nearly doubled the retention of GOx in a biosensor while decreasing the average enzymatic activity of retained enzyme by a factor of 4-5. Such inhibition should be considered when using a protein-assisted solubilization of CNT in water for biomedical applications. The proposed analytical protocols can be also applied to study the effects of nanoparticles on proteins in assessing the health risks associated with the use of nanomaterials.

Biofuel cells for biomedical applications: colonizing the animal kingdom

Interdisciplinary research has combined the efforts of many scientists and engineers to gain an understanding of biotic and abiotic electrochemical processes, materials properties, biomedical, and engineering approaches for the development of alternative power-generating and/or energy-harvesting devices, aiming to solve health-related issues and to improve the quality of human life. This review intends to recapitulate the principles of biofuel cell development and the progress over the years, thanks to the contribution of cross-disciplinary researchers that have combined knowledge and innovative ideas to the field. The emergence of biofuel cells, as a response to the demand of electrical power devices that can operate under physiological conditions, are reviewed. Implantable biofuel cells operating inside living organisms have been envisioned for over fifty years, but few reports of implanted devices have existed up until very recently. The very first report of an implanted biofuel cell (implanted in a grape) was published only in 2003 by Adam Heller and his coworkers. This work was a result of earlier scientific efforts of this group to "wire" enzymes to the electrode surface. The last couple of years have, however, seen a multitude of biofuel cells being implanted and operating in different living organisms, including mammals. Herein, the evolution of the biofuel concept, the understanding and employment of catalyst and biocatalyst processes to mimic biological processes, are explored. These potentially green technology biodevices are designed to be applied for biomedical applications to power nano- and microelectronic devices, drug delivery systems, biosensors, and many more.