Enzyme-Controlled Self-Assembly and Transformation of Nanostructures in a Tetramethylbenzidine/Horseradish Peroxidase/H₂O₂ System

Enzyme-assisted bottom-up nanofabrication has attracted considerable attention because it provides an ideal strategy for fabricating and tailoring well-defined nanostructures with desired properties under physiological reaction conditions. Here, we report self-assembly and transformation of nanostructures controlled by enzymatic kinetics in a system consisting of horseradish peroxidase (HRP), hydrogen peroxide (H(2)O(2)), and 3,3',5,5'-tetramethylbenzidine (TMB). In this system, several TMB derivatives, produced in the presence of the enzyme HRP at different concentrations, assemble into nanoscale structures in a variety of morphologies and colors. Significantly, the assembly process is reversible, resulting in transformation of the synthesized nanostructures from one morphology into another through disassembly and reassembly processes under physiological conditions. The capability of synthesizing and controlling these "nano-transformers" through tuning enzymatic kinetics creates new opportunities for synthesis of smart materials and biomimetic nanofabrication.