Nitrosoreductase-Like Nanocatalyst for Ultrasensitive and Stable Biosensing

Abstract

Enzyme-like nanocatalytic reactions developed for high signal amplification in biosensors are of limited use because of their low reaction rates and/or unwanted side reactions in aqueous electrolyte solutions containing dissolved O-2. Herein, we report a nitrosoreductase-like catalytic reaction, employing 4-nitroso-1-naphthol, Pd nanoparticles, and H3N BH3, which affords a high reaction rate and minimal side reactions, enabling its use in ultrasensitive electrochemical biosensors. 4-Nitroso-l-naphthol was chosen after five hydroxy-nitro(so)arene compounds were compared in terms of high signal and low background levels. Importantly, the nanocatalytic reaction occurs without the self-hydrolysis and induction period observed in the nanocatalytic reduction of nitroarenes by NaBH4. The high signal level results from (i) fast nanocatalytic 4nitroso-1-naphthol reduction, (ii) fast electrochemical redox cycling, and (iii) the low influence of dissolved O-2. The low background level results from (i) slow direct reaction between 4-nitroso-1naphthol and H3N BH3, (ii) slow electrode-mediated reaction between 4-nitroso-1-naphthol and H3N BH3, and (iii) slow electrooxidation of H3N BH3 at electrode. When applied to the detection of parathyroid hormone, the detection limit of the newly developed biosensor was similar to 0.3 pg/mL. The nitrosoreductaselike nanocatalytic reaction is highly promising for ultrasensitive and stable biosensing.