Microneedle-based transdermal electrochemical biosensors based on Prussian blue-gold nanohybrid modified...

We report on the fabrication of a microneedle-based electrochemical biosensor for use in transdermal biosensing, which includes a screen-printed electrode containing a Prussian blue-gold nanohybrid as the working electrode. The Prussian blue gold nanohybrid is made from polyethylenime (PEI)- mediated simultaneous synthesis of Prussian blue (PBNP) and gold nanoparticles (AuNP), which forms a PBNP-AuNP nanohybrid with a remarkable change in the Prussian blue character. PEI-protected polycrystalline PBNPs can be synthesized in acidic media from the single precursor potassium ferricyanide [K₃ Fe(CN)₆ ] at 60°C. Since PEI also enables the controlled formation of gold nanoparticles (AuNPs) in the presence of formaldehyde, nanohybrids containing PBNPs and AuNPs may be prepared. Two different methods of PEI mediated synthesis of AuNP in the presence of PBNP were considered. In Method 1, AuNP and PBNP were made independently and mixed together in an appropriate ratio. In Method 2, PBNPs were made first, followed by PEI- and formaldehyde-mediated reduction of gold cations in the presence of PBNP. PBNP-AuNPs display a remarkable change in Prussian blue behavior such that the absorption maxima of PBNP-AuNPs made through Method 1 tend to increase at 670 nm as a function of gold concentration as compared with the control; the reverse was observed when PBNP-AuNPs were made through Method 2. As made PBNPs and PBNP-AuNPs made through Method 1 display excellent catalytic activity toward both reduction and oxidation of hydrogen peroxide based on peroxidase mimetic activity. In addition, the as-synthesized PBNPs displayed superparamagnetic behavior that can be manipulated in the presence of AuNPs. The results from peroxidase mimetic activity, chemiluminescence, cyclic voltammetry, and amperometry showed suitable analytical performance of the as-made PBNP-AuNP nanohybrid for biomedical applications.