Green light-emitting BSA-conjugated dye supported silica nanoparticles for bio-imaging applications

Abstract

Silica nanoparticles have attracted a huge bioaudience as these are biosafe materials for targeted delivery applications due to their ease of functionalisation, less toxicity, and bio-compatibility. However, poor knowledge of the interaction mechanism between silica nanoparticles and protein causes less development of silica-based fluorescent probes for practical applications. Hence, in this work, the interaction mechanism and structural changes in BSA caused by silica nanoparticles with different functional groups have been studied. First dye-supported silica nanoparticles with hydroxyl terminal (DSN) and amine terminal (DSFN) were synthesized by a modified Stober process. The dye supported on silica nanoparticles resulted in improving the photostability, with less toxicity when compared to the bare dye system. To improve the bioavailability, BSA was conjugated with both hydroxyl (BSA–DSN) and amine functionalised dye supported silica nanoparticles (BSA–DSFN). To understand the structural modification induced by silica with different terminals, nanoparticles were incubated with BSA (Bovine Serum Albumin) for 48 h. Then, the structural changes caused by BSA interacting with silica nanoparticles were evaluated using various techniques such as UV-VIS spectroscopy, fluorescence spectroscopy, CD (circular dichroism), and lifetime measurements. Longer lifetime emphasized the stable photophysical properties of BSA conjugated dye supported silica nanoparticles for live-cell imaging. These interaction studies generated knowledge on structural modification induced by BSA adsorption on silica nanoparticles and its bioavailability for cell imaging. The circular dichroism measurement divulges that the stabilisation of the secondary structure and improved thermal stability of BSA were attained after conjugating with silica nanoparticles. Cell toxicity and imaging results showed that BSA conjugated with amine-functionalised silica nanoparticles BSA@DSFN proved to be an ideal candidate for long-life fluorescent probes for cellular imaging application.