Amit Kumar Bhunia

ZnO nanoparticle-protein interaction: Corona formation with associated unfolding

The interaction as well as the formation of bioconjugate of Bovine Serum Albumin (BSA) and Zinc Oxide nanoparticles (ZnO NPs) is investigated. The surface binding along with reorganization of BSA on the surface of ZnO NPs forms stable “hard corona.” The time constants for surface binding and reorganization are found to be 1.10 min and 70.68 min, respectively. The close proximity binding of BSA with ZnO NPs via tryptophan is responsible for bioconjugate formation. Fibrillar aggregated structure of BSA is observed due to conformational change of BSA in interaction with ZnO NPs.

Biocompatibility study of protein capped and uncapped silver nanoparticles on human hemoglobin

The interactions of human hemoglobin with protein capped silver nanoparticles and bare silver nanoparticles were studied to understand fundamental perspectives about the biocompatibility of protein capped silver nanoparticles compared with bare silver nanoparticles. Bare silver (Ag) nanoparticles (NPs) were prepared by the chemical reduction method. High resolution transmission electron microscopy (HRTEM) analysis along with absorption at ~390 nm indicated the formation of bare Ag NPs. Protein coated Ag NPs were prepared by a green synthesis method. Absorption at ~440 nm along with ~280 nm indicated the formation of protein coated Ag NPs. The biocompatibility of the above mentioned Ag NPs was studied by interaction with human hemoglobin (Hb) protein. In presence of bare Ag NPs, the Soret band of Hb was red shifted. This revealed the distortion of iron from the heme pockets of Hb. Also, the fluorescence peak of Hb was quenched and red shifted which indicated that Hb became unfolded in the presence of bare Ag NPs. No red shift of the absorption of Soret, along with no shift and quenching of the fluorescence peak of Hb were observed in the presence of protein coated Ag NPs. A hemolysis assay suggested that protein coated Ag NPs were more biocompatible than bare one.

Safety concerns towards the biomedical application of PbS nanoparticles: An approach through protein-PbS interaction and corona formation

Semiconductor nanoparticles (NPs) with near-infrared (NIR) fluorescence has achieved great interest for early detection of colon tumors/cancer. We have synthesized lead sulphide (PbS) NPs (5–7 nm) having emission in NIR region and investigated its interaction with bovine serum albumin (BSA) to determine the bio-safety of PbS NPs. The interaction of PbS NPs with BSA occurs through formation of “hard” and “soft” protein NPs corona and follows exponential association. The hard corona represents that the core PbS NPs are fully covered by BSA with shell thickness of ∼8 nm, i.e., the dimension of BSA monomer. A large number of PbS NPs with hard corona of BSA forms “colony” with diameters in the range of 200–400 nm. The soft corona grows surrounding this colony. The quenching of fluorescence BSA in the presence of PbS NPs follows dynamic quenching process with tryptophan as major binding sites. Nearest to human body temperature, positive cooperative association between PbS NPs and BSA are found, and affinity of BSA to the PbS NPs gradually increases in superlinear fashion. The electrostatic interaction is the key force in binding of PbS NPs with BSA, and hydrophobic interaction between PbS NPs and BSA is responsible for conformational change of BSA.