Study On Self-powered Biosensor Based On Capacitor Assisted Signal Amplification

Self-powered biosensors are the current research hotspot in biomedical,chemistry,energy and other fields.Self-powered biosensors based on enzymatic biofuel cells have some unique advantages over conventional electrochemical biosensors:First,its detection limit is usually low,making it expected to be a tool for quantitative detection.Second,it does not require the reference and pair electrodes,and the entire device is easier to miniaturize.Finally,its no additional power supply,easy to build a portable device.Current low sensitivity limits the development of self-powered biosensors,the introduction of energy storage devices and biological amplification technology can further improve the sensitivity of the self-powered biosensors.This paper constructs a novel self-powered biosensors for the high-sensitive detection of micro RNA-21 based on the enzyme biofuel cell,capacitors,signal amplification strategy and portable multimeter.The main contents are as follows:（1）Self-powered electrochemical biosensors were constructed based on catalytic hairpin assembly and enzymatic biofuel cells,and capacitors were integrated into the biosensor to read the output signal through a digital multimeter.The matching relationship between self-powered biosensor and capacitors is studied and the relevant parameters are optimized.Generates electrons when the target micro RNA-21 triggers catalytic hairpin assembly cycle,while flows to cathode through the external circuit which can catalyze the reduction of oxygen with release[Fe（CN）₆]^3-electron acceptor.Under optimization conditions,the limit of detection of the developed biosensor is as low as 0.18 fmol/L（S/N=3）with a linear range of 0.5-1.0×10~4fmol/L.The sensitivity of the self-powered biosensor after the introduction of the capacitor is 38.72μA/pmol/L,16.83 times that of the enzymatic biofuel cells without introducing the capacitor（2.3μA/pmol/L）.（2）A micor RNA-21 self-powered biosensor with multiple signal amplification was constructed based on 3D DNA walker,enzymatic biofuel cells and capacitors.The 3D DNA walker was designed from an enzyme-free target triggered catalytic hairpin assembly modified gold nanoparticles.When triggered by the target micor RNA-21,the3D DNA walker will move along the catalytic hairpin track,bioanode glucose oxidation produces electrons,and the biocathode gets electrons,producing a large open circuit voltage.Capacitors were introduced into enzymatic biofuel cells with 28.82 times higher sensitivity.The self-powered biosensor showed a good linear relationship in the concentration range of 0.5-1.0×10~4fmol/L,with the detection limit of 0.17 fmol/L（S/N=3）.Finally,the constructed self-powered biosensor was applied to the human serum analysis to achieve the ultrasensitive detection of micro RNA-21.（3）A novel self-powered biosensing platform for multimeter reading visualization is constructed.The platform consisted of a enzymatic biofuel cells,a capacitor,a digital multimeter and a computer.An enzymatic biofuel cells based on dual recycling amplification are elaborately designed to double the output signal by converting a small number of targets into two glucose oxidase labeled output strand DNAs.Meanwhile,the squeezed-out output strand will also be recycled by the cathode to fix more[Ru（NH₃）₆]³⁺to further improve the sensitivity of micro RNA-21 detection.In addition,after the introduction of the capacitor,the digital multimeter reading can be recorded on the computer display screen in real time to improve the accuracy of the results.The linear range of the new method is 0.1-1.0×10~4fmol/L,and the detection limit is 0.04 fmol/L（S/N=3）.