| AVS 57th International Symposium & Exhibition | |
| Biomaterial Interfaces | Wednesday Sessions |
| Session BI2-WeM |
| Session: | Proteins & Peptides on Surfaces |
| Presenter: | S. Sammeta, University of New Mexico |
| Authors: | S. Sammeta, University of New Mexico G. Doroudian, University of New Mexico G.P. Lopez, University of New Mexico E.Y. Chi, University of New Mexico |
| Correspondent: | Click to Email |
Utilization of biological molecules such as proteins in biosensing and biofuel cell applications is one of the most innovative research fields. A major challenge that needs to be overcome in these applications is the adequate stabilization of proteins. Porous silica material made by the sol-gel process provides a promising host matrix for the encapsulation of proteins to increase their stability. The main objective of this study is to elucidate protein-host matrix interactions for the stabilization of proteins. In our study, lysozyme and cytochrome c were used as model proteins. We have developed two novel vapor exposure sol-gel techniques to encapsulate proteins using tetra methyl orthosilicate (TMOS) as a precursor: (I) in-situ protein exposure method, where a buffer containing a protein is directly exposed to TMSO vapor, and (II) buffer exposure method, where a buffer was first exposed to TMOS vapor and then a protein was added. Additionally, organically-modified glasses are used to study the effect of host-matrix hydrophobicity on protein structure and stability. Circular dichroism and high resolution derivative UV spectroscopy are used to evaluate the structure and thermal stability of encapsulated proteins. The effect of protein concentration and sucrose (a model osmolyte) on the structure and stability of encapsulated proteins are characterized. Cytochrome c retained native-like structures while lysozyme becomes partly unfolded when encapsulated in the silica matrix. Entrapment generally increases the thermal stability of proteins. Proteins encapsulated via the in situ technique are found to have higher thermal stability compared to those encapsulated using method II. In general, method II gave rise to proteins with more secondary structure. However, proteins in this matrix are less resistant to thermal denaturation. In addition, there are concentration-dependent decreases in protein secondary structure when encapsulated by method II. We believe that the trends are due to protein adsorption onto silica which causes denaturation. Osmolytes shift the protein native state ensemble towards more compact conformations, thereby increasing the conformational stability of proteins. We observed enhanced secondary structure of cytochrome c with the addition of 0.5 M sucrose and this enhanced structure and stability is preserved when the protein is encapsulated in silica gel in the presence of sucrose. The effect of increasing the host-matrix hydrophobicity by incorporating alkyl group substituted alkoxysilanes into the silica matrix on protein structure and stability will be presented.