This work provides quantitative analysis of association of the transport protein, Bovine Serum Albumin (BSA) with lipid nanoparticles using combined calorimetric and spectroscopic approach. Serum albumin is the most abundant protein in plasma accounting for about 60% of total protein content. It has a wide range of physiological functions involving transport, and delivery of fatty acids, drugs and steroids among others. With booming development of nano-medicines, significant attention has been paid to biocompatible solid lipid nanoparticles (SLNs) [1-2]. Studying the binding interactions of the SLNs with the serum albumin paves the way to understanding the bimolecular recognition process essential for the rational drug design process.
SLNs were successfully formed by employing GMS and pluronic F68 using hot emulsification methodology. The size of SLNs after incubation with the BSA is found to be almost similar to pristine SLNs which suggests that there is no significant adsorption of the protein on the SLNs surface which means there is less possibility of protein corona layer formation on the surface of the SLNs.
The energetics of interactions of BSA with the SLNs were examined. The value of association constant with a blue shift of 12 nm in the fluorescence emission of BSA suggests that weak interactions among SLNs and protein leads to internalization of tryptophan residues. The weak nature of SLN-BSA interaction has also been inferred from UV-visible spectroscopic measurements.
Thermal stabilization of BSA in presence of SLNs, suggests conformational change in protein leading to a more compact form as indicated by blue shift observed in fluorescence spectra. Further, CD spectroscopy also showed an increase in α-helicity in BSA upon addition of SLNs, while tertiary structure of protein is maintained. ITC results have demonstrated predominance of hydrophobic interactions in SLNs-BSA complex. Nonpolar patches of BSA interact with hydrophobic portion of SLNs resulting in desolvation and an increase in randomness of the system
The results demonstrate less possibility of weak protein corona formation on the surface of the lipid nanoparticles. To design a targeted drug delivery system, the present work will contribute to obtain mechanistic aspects of comprehending the interactions of lipid nanoparticles with protein.