Investigation on silver nanocrystals induced structural modulation of biomarker alkaline phosphatase through spectroscopic and thermodynamic assessment

Study on interactions between alkaline phosphatase (ALP), a clinical biomarker, and biocompatible silver nanoparticles (AgNPs) can provide better insight towards the generation of novel functional biochemical units that interface the exceptional optoelectronic characteristics of metallic nanocrystals with the exclusive recognition and catalytic properties of enzyme molecules. Here, we endeavored to explore the mode of interactions of alkaline phosphatase with differently produced AgNPs through various spectroscopic techniques and micro-calorimetric measurements. Fluorescence spectroscopic results suggest that modifications of tryptophan residues of ALP by as-synthesized AgNPs have taken place to the different extents due to the morphological differences among various nanoparticles which may be caused by variation in protein adsorption. The circular dichroism spectroscopic measurements signify AgNPs induced minor conformational changes in α helical structures of enzyme molecule and occurrence of protein unfolding. Thermodynamic data reveal that the interactions involved between AgNPs and ALP are exothermic and enthalpy driven spontaneous process. This report provides valuable information on enzyme-nanoparticle interactions which are very much demanding fundamental aspects of nano-bio interfacing and applications in the emerging areas of biotechnological and industrial applications of nano-structured materials, like enzyme immobilization, sensing, etc.