Horseradish peroxidase-AuNP/LDH heterostructures: influence on nanogold release and enzyme activity

Gold nanostructures (AuNP) are important as strong platforms for targeted therapeutic and diagnostic applications. Tireless effort has been devoted nowadays to explore the multifunctionality of AuNP in multicomponent biostructures. Herein, we report the fabrication of horseradish peroxidase enzyme (HRP)-AuNP/ZnAlLDH heterostructure by the facile synthesis of AuNP on the biocompatible matrices of layered double hydroxides (LDH) followed by the immobilization of the enzyme on AuNP/LDH assemblies. During this process, ZnAlLDH have a dual function of exploring its structural “memory effect” for the synthesis of nanogold and acting as a support for the enzyme immobilization. X-ray diffraction (XRD), UV-Vis spectrometry, transmission electronic microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and infrared (FTIR) spectroscopy have been used to characterize the structural, chemical composition, optical, and morphology of the novel materials. We present here the release of AuNP from HRP-AuNP/ZnAlLDH by using as controlled variables HRP:LDHs ratio and the pH of the solution. Results show that AuNP established close interactions with HRP and formed an HRP-AuNP bioconjugate. Results reveal that HRP suffers a significant loss of the activity in the presence of nanoparticles of gold, such that, AuNP act to inhibit the activity of the enzyme. AuNP behavior in enzyme-bio-heterostructures should be inspiring for future applications of AuNP in nanomedicine.