A reagentless tyrosinase biosensor based on 1,6-hexanedithiol and nano-Au self-assembled monolayers

An amperometric tyrosinase biosensor was developed via a simple and effective immobilization method using the self-assembled monolayers (SAMs) technique. The organic monolayer film was first formed by the spontaneous assembly of thiolor sulfur compound (1,6-hexanedithiol, HDT) from solution onto gold electrode. When these thiolrich surfaces were exposed to Au colloid, the sulfurs form strong bonds to gold nanoparticles, anchoring the clusters to the electrode substrate. After the assembly of gold nanoparticles layer, a new nano-Au surface was obtained. Thus, the tyrosinase could be immobilized onto the electrode. The tyrosinase retained its activity well in such an immobilization matrix. The various experimental variables for the enzyme electrode were optimized. The resulting biosensor can reach 95% of steady-state current within 10 s, and the trend in the sensitivity of different phenolic compounds was as follows: catechol > phenol > p-cresol. In addition, the apparent Michaelis-Menten constant (K-m(app)) and the stability of the enzyme electrode were estimated.