A High-Performance Hybrid Biofuel Cell with a Honeycomb-Like Ti3 C2 Tx /MWCNT/AuNP Bioanode and a ZnCo2 @NCNT Cathode for Self-Powered Biosensing

Self-Powered Biosensor Driven by a Hybrid Biofuel Cell with CuCoP-Polyoxometallate Composite as Both Cathode Catalyst and Sensing Interface

Abnormal concentrations of hydrogen peroxide (H2O2) are toxic to living cells and may induce a number of diseases. Herein, a self-powered miniaturized biosensor (SPB) based on an enzyme biofuel cell is constructed to monitor H2O2. This SPB significantly minimized the use of bioenzymes that often experience instability and lead to the high cost of biosensors. More specifically, a composite of polydopamine (PDA)-gold nanoparticles (AuNPs) is prepared as an anodic catalyst scaffold to immobilize glucose oxidase to efficiently catalyze the oxidation of glucose (fuel) due to its excellent biocompatibility and electrical conductivity. Upon the incorporation of CuCoP with a polyoxometalate H3PW12O40 (PW12), a nanoenzyme of CuCoP-PW12 composite is realized as a non-biological cathodic catalyst to replace the conventional cathode enzymes for the reduction of H2O2. The abundant catalytic active sites on CuCoP-PW12 and high electron transfer rate of PW12 result in a high catalytic activity toward H2O2 reduction at the cathode. Owing to a good synergy between the bioanode and abiotic-cathode, the prepared SPB exhibits two linear ranges (2-20 and 20-50 µm) and a low detection limit (0.0589 µm) toward H2O2 detection. Upon the use of H2O2 as a model analyte, this work demonstrates that SPB can be effectively applied in biomedical sensing.

Target-Responsive Regulation of Bacteria-Surface Magnetic Element for Self-Powered Analysis of Aflatoxin B1 in Microbial Fuel Cell

The limitation of the sensing mode greatly restricts the detectable species and detection specificity of microbial fuel cell-based self-powered biosensors (MFC-SPBs). Herein, we develop a bacterial quantity change-based sensing mode for MFC-SPBs, in which the Fe3O4@Au content modified on exoelectrogenic bacteria is designed to correlate with analyte concentration for regulating the bacterial numbers absorbed onto the magnetic auxiliary anode. The polydopamine and Au nanoparticles comodified bacteria are attached with complementary DNA for hybridization with aptamer-modified Fe3O4@Au nanospheres. When aflatoxin B1 (AFB1) is used as the model analyte, its appearance can cause the liberation of Fe3O4@Au nanospheres from bacteria due to aptamer recognition. Furthermore, introduced exonuclease I can achieve a recycling amplification effect, intensifying the release of Fe3O4@Au nanospheres. With the decrease in bacteria-surface Fe3O4 content, bacteria that can be adsorbed onto the anode in a magnetic field will be reduced, leading to a decrease in the performance of MFC-SPBs. The results show that the developed MFC-SPBs can quantitatively determine AFB1 with a limit of detection of 5 nM (S/N = 3). Also, the MFC-SPBs show good detection specificity and can assess AFB1 in peanut samples. Considering the good specificity and species diversity of aptamers, we believe that this developed sensing mode will receive wide attention in the field of MFC-SPBs.

Apical Anchoring and Cofactor Customizing To Achieve Ultrahigh Active Nanoenzymes for Removing O2 Interference in Glucose Electro-oxidation

Noble metal nanozymes (NMs) are promising alternatives to the fragile glucose oxidase (GOD), however, in all previously reported NMs, O2 consumes electrons from glucose by competing with electrodes, which remarkably limits the Faraday efficiency. The low NM utilization rate and sluggish mass transfer severely limit the electrocatalytic activity. Herein, we report the first Au nanozyme that can catalyze glucose electro-oxidation (GEO) via a distinctive O2 immune pathway with record-breaking mass activity based on apical anchoring and cofactor customization. Strategically, we design a cofactor of lipoic acid (ALA) that can accept electrons from glucose in preference to O2 for Au nanoparticles, and anchor AuNPs/ALA on top of sheared hydrophilic carbon nanotubes (T-SCNT/AuNPs/ALA). Mechanistically, ALA has highly reversible redox activity, and its reduction state is insensitive to O2, thus, it can mediate direct electron transfer between the electrode and AuNPs. In addition, compared to CNT/AuNPs, T-SCNT/AuNPs/ALA has a larger electrochemical surface area, lower charge transfer resistance, and superior hydrophilicity, which are favorable for improving the reaction rate and efficiency. Notably, this strategy can be used to design bilirubin oxidase mimics (T-SCNT/AuNPs/rutin), whose oxygen reduction activity significantly surpasses that of bilirubin oxidase. Consequently, compared to CNT/AuNPs, T-SCNT/AuNPs/ALA boosts the Faraday efficiency of GEO from 50% to 98%, shows a 755-fold increase in mass activity, and enables glucose biofuel cells to offer a 118-fold increase in power density. To the best of our knowledge, this is the first study to achieve a non-O2-interference GEO nanozyme by synergistically regulating the cofactor and catalytic interface and will guide the engineering of demand-specific electrocatalysts.

Research Progress in Enzyme Biofuel Cells Modified Using Nanomaterials and Their Implementation as Self-Powered Sensors

Enzyme biofuel cells (EBFCs) can convert chemical or biochemical energy in fuel into electrical energy, and therefore have received widespread attention. EBFCs have advantages that traditional fuel cells cannot match, such as a wide range of fuel sources, environmental friendliness, and mild reaction conditions. At present, research on EBFCs mainly focuses on two aspects: one is the use of nanomaterials with excellent properties to construct high-performance EBFCs, and the other is self-powered sensors based on EBFCs. This article reviews the applied nanomaterials based on the working principle of EBFCs, analyzes the design ideas of self-powered sensors based on enzyme biofuel cells, and looks forward to their future research directions and application prospects. This article also points out the key properties of nanomaterials in EBFCs, such as electronic conductivity, biocompatibility, and catalytic activity. And the research on EBFCs is classified according to different research goals, such as improving battery efficiency, expanding the fuel range, and achieving self-powered sensors.

Advanced Self-Powered Biofuel Cells with Capacitor and Nanogenerator for Biomarker Sensing

Self-powered biofuel cells (BFCs) have evolved for highly sensitive detection of biomarkers such as noncodon micro ribonucleic acids (miRNAs) in the presence of interfering substrates. Self-charging supercapacitive BFCs for in vivo and in vitro cellular microenvironments represent the most prevalent sensing mechanism for diagnosis. Therefore, self-powered biosensing (SPB) with a capacitor and contact separation with a triboelectric nanogenerator (TENG) offers electrochemical and colorimetric dual-mode detection via improved electrical signal intensity. In this review, we discuss three major components: stretchable self-powered BFC design, miRNA sensing, and impedance spectroscopy. A specific focus is given to 1) assembling of sensors for biomarkers, 2) electrical output signal intensification, and 3) role of supercapacitors and nanogenerators in SPBs. We outline the key features of stretchable SPBs and the sequence of miRNA sensing by SPBs. We have emphasized the need of a supercapacitor and nanogenerator for SPBs in the context of advanced assembly of the sensing unit. Finally, we outline the role of impedance spectroscopy in the detection and estimation of biomarkers. We highlight key challenges in SPBs for biomarker sensing, which needs improved sensing accuracy, integration strategies of electrochemical biosensing for in vitro and in vivo microenvironments, and the impact of miRNA sensing on cancer diagnostics. This article attempts a specific focus on the accuracy and limitations of sensing unit for miRNA biomarkers and associated tool for boosting electrical signal intensity for a potential big step further.