Tyrosinase-catalyzed polymerization of l-DOPA (versusl-tyrosine and dopamine) to generate melanin-like biomaterials for immobilization of enzymes and amperometric biosensing

Abstract

Learning from nature emerges as one of the most promising ways to develop advanced functional materials and biodevices. Here, inspired by melanin formation, we report the tyrosinase (Tyr)-catalyzed polymerization of L-DOPA (versus L-tyrosine and dopamine) to immobilize enzymes for amperometric biosensing. The enzymatic polymerization is examined by UV-vis spectrophotometry, scanning electron microscopy and electrochemical methods. A poly(L-DOPA) (PD)-Tyr/glassy carbon electrode (GCE) prepared by casting an aqueous mixture of L-DOPA and Tyr on a GCE exhibits a linear cathodic amperometric response to catechol concentration from 0.4 to 57 μM (R² = 0.997) with a sensitivity of 4.29 mA mM⁻¹ cm⁻² and a limit of detection (LOD) of 70 nM (S/N = 3). A PD-glucose oxidase (GOx)-Tyr/Pt electrode prepared by casting an aqueous mixture of L-DOPA, GOx and Tyr on a Pt electrode exhibits a linear anodic amperometric response to glucose concentration from 2 to 5700 μM (R² = 0.998) with a sensitivity of 78.6 μA mM⁻¹ cm⁻² and a LOD of 0.1 μM (S/N = 3). The PD-based enzyme electrode shows better biosensing performance and higher bioactivity of the immobilized Tyr than those based on similarly biosynthesized poly(L-tyrosine) and polydopamine as well as well-established chitosan and Nafion systems, implying that the biosynthesized PD as a melanin-biomimetic material has promising application potential for biomacromolecular immobilization and biosensing.