Vinayaraj Ozhukil Kollath

A Modular Approach To Study Protein Adsorption on Surface Modified Hydroxyapatite

Biocompatible inorganic nano- and microcarriers can be suitable candidates for protein delivery. This study demonstrates facile methods of functionalization by using nanoscale linker molecules to change the protein adsorption capacity of hydroxyapatite (HA) powder. The adsorption capacity of bovine serum albumin as a model protein has been studied with respect to the surface modifications. The selected linker molecules (lysine, arginine, and phosphoserine) can influence the adsorption capacity by changing the electrostatic nature of the HA surface. Qualitative and quantitative analyses of linker-molecule interactions with the HA surface have been performed by using NMR spectroscopy, zeta-potential measurements, X-ray photoelectron spectroscopy, and thermogravimetric analyses. Additionally, correlations to theoretical isotherm models have been calculated with respect to Langmuir and Freundlich isotherms. Lysine and arginine increased the protein adsorption, whereas phosphoserine reduced the protein adsorption. The results show that the adsorption capacity can be controlled with different functionalization, depending on the protein-carrier selections under consideration. The scientific knowledge acquired from this study can be applied in various biotechnological applications that involve biomolecule-inorganic material interfaces.

Protein-calcium phosphate nanocomposites: Benchmarking protein loading via physical and chemical modifications against co-precipitation

The low protein loading capacity of commercially available calcium phosphate (CaP) is a major impediment in effectively using this inorganic material as a protein carrier despite its recognized biocompatibility. In this study, nanocomposites of CaP and BSA were prepared by carefully designed precipitation methods in aqueous media. In the first co-precipitation method (CaP–BSA-1), calcium and phosphate precursors were simultaneously added to the protein solution matrix and in the second method (CaP–BSA-2) the protein solution was added after the reaction of the precursors. The crystallinity and phase composition of the resulting powders were determined using an X-ray diffraction technique. Qualitative confirmation of the presence of BSA on the nanocomposites, was obtained using mass spectrometry, ATR-FTIR and XPS. The results from desorption and thermogravimetric measurements indicated that BSA was trapped inside the cavities in the case of CaP–BSA-1 whereas it was mostly surface adsorbed in the case of CaP–BSA-2. The protein loading capacity of these composites was compared with various physical and chemical surface modification strategies used on commercially available calcium phosphate powders. Nanocomposite particulates were found to have about 275% higher protein loading capacity as compared to a commercial CaP powder with the same surface area. Overall, this study benchmarks the different techniques used for protein loading enhancement on inorganic materials.