Role reversal of silica nanoparticles with bovine trypsin from enzyme inhibitor to enzyme activator on surface modification

Silica nanoparticles (SiNPs) are one of the most extensively used nanoparticles, which are employed in diverse fields such as bioimaging, drug delivery, biosensing, etc. In this study, SiNPs were synthesized using condensation method, with further surface functionalization using 3-aminopropyltetraethoxysilane (APTES) to facilitate the formation of bioactive conjugates. These nanoparticles were characterized using SEM, HR-XRD, TEM, DLS, FTIR, and TGA. Further, comparative studies for determining the effect of SiNPs and SiNPs@APTES on the structure and activity of bovine trypsin were performed using different physicochemical techniques, accompanied by enzymatic activity assay. UV-Visible, FTIR, and fluorescence studies indicated a possible change in the conformation of trypsin due to both types of nanoparticles. The quantitative analysis using UV-Visible data showed that the SiNPs (KBH = 5.50 ×104 M-1) have higher binding potential, as compared to that of SiNPs@APTES (KBH = 2.96 ×104 M-1). CD results showed that SiNPs destabilize the structure of trypsin, while SiNPs@APTES provide an overall stabilizing effect. Enzymatic activity studies revealed that SiNPs@APTES work as an activator, while SiNPs work as an inhibitor for trypsin activity, suggesting the role reversal of SiNPs on surface modification. Our studies strongly suggest that SiNPs and SiNPs@APTES can be employed for regulating trypsin activity for biomedical applications.