Electrochemical Estimations of the Gold Nanoparticle Size Effect on Cysteine-Gold Oxidation

Abstract Gold nanoparticles are interesting for nanobiomedical applications, such as drug delivery and diagnostic imaging contrast agents. However, their stability reactivity in-vivo influenced by surface properties size. Here, we investigate the electrochemical oxidation of differently sized citrate-coated gold in presence absence L-cysteine, a thiol-containing amino acid with high binding affinity to gold. We found that smaller (5, 10 nm) were significantly more susceptible L-cysteine interactions and/or L-cysteine-facilitated than larger (20, 50 nanoparticles, both same mass nominal area, under conditions investigated (pH 7.4, room temperature, stagnant solutions, scan rates 0.5 450 mV/s). The measurements drop-casted nanoparticle suspensions on paraffin-impregnated graphite electrodes quality electrode. Increased cycling resulted irreversible detachment/oxidation into solution. Our results suggest L-cysteine-gold stronger nanoparticles.