Excipient Mediated Biostabilization of Protein Using Spray Drying Technique

Abstract

Biologically active molecules like proteins are better preserved in dry condition owing to lower water activity and lower intra-molecular movement. However, 3-D conformation of protein is dependent on water around it. Upon drying, water around the protein is lost and therefore, excipients that work as water substitute molecule is provided during drying to preserve its 3-D structure. Bovine serum albumin (BSA) is taken as a model protein in this study. BSA is one of the highly studied proteins. Easy accessibility, low cost and inert behaivour enhances its significant utility in various biochemical formulations. In this study, BSA and excipient-BSA combinations were subjected to different levels of heat stress and the resulting structural changes were assessed using native gel electrophoresis, DSC (Differential Scanning Calorimetry), FTIR (Fourier Transform Infrared Spectroscopy) techniques. Native PAGE, FTIR, DSC techniques are used to determine the aggregation, secondary structure and glass transition properties of the spray dried and heat treated proteins respectively. The moisture content of the spray dried samples was determined by Thermo gravimetric analysis (TGA). For a protein to be stable, low moisture content, high Tg values are ideal. Protein aggregation has a direct link with its secondary structure. Thus, upon heat treatment of BSA and excipient-BSA combinations it is important that protein does not aggregate and the secondary structure remain intact for the protein to be stable.