Catalytic activity of polymerized self-assembled artificial enzyme nanoparticles: applications to microfluidic channel-glucose biofuel cells and sensors

Abstract

Synthesized catalysts composed of hydrazine-bearing conducting polymer nanoparticles (poly[2,2′:5′,2′′-terthiophene-3′-yl hydrazine] (polyTHyd) and (poly[4-([2,2′:5′,2′′-terthiophen]-3′-yl) phenyl) hydrazine] (polyTPHyd)) were prepared through self-assembling monomers on gold nanoparticles (monomers–AuNPs: dia. 7.5 ± 2.0 nm). The monomers self-assembled on AuNPs were electrochemically polymerized to form conducting polymer nanoparticles, which possessed an enzyme-like catalytic activity for the reduction of H₂O₂. The polymer-assembled nanoparticles immobilized on microfluidic channel electrodes revealed well defined direct electron transfer (DET) processes, which were observed at +54.5/−20.9 and +64.8/+3.6 mV for polyTHyd and polyTPHyd. Glucose oxidase (GOx) and horseradish peroxidase (HRP) were immobilized on the carboxylated polyterthiophene (poly[2,2′:5′,2′′-terthiophene-3′-(p-benzoic acid)])-assembled nanoparticle layer to use as counter electrodes in the cells. The performances of microfluidic biofuel cells composed of a GOx-modified anode and cathodes of HRP and hydrazine-bearing polymer-assembled nanoparticles were compared using standard glucose, urine, and whole blood samples as fuels. The cell operated with a 10.0 mM glucose solution generated a maximum electrical power density of 0.78 ± 0.034 mW cm⁻² and an open-circuit voltage of 0.48 ± 0.035 V. The cell was also examined as a glucose-sensing device, which had a dynamic range of 10.0 μM to 5.0 mM with a detection limit of 2.5 ± 0.2 μM under alternating current potential modulation.