STRUCTURAL ENCAPSULATION OF MODEL PROTEINS IN BIOPOLYMER

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Description (Adapted from Application): Many proteins, including pharmaceutically relevant ones, can be delivered for prolonged times from synthetic biocompatible polymers to the human body. These findings hold the promise of significantly expanding the use of such proteins for the prevention and cure of diseases. However, the encapsulation of proteins in biocompatible polymers includes events detrimental to their structure, such as exposure to organic solvents, shear forces, hydrophobic interfaces, and dehydration. While it is routine to analyze the release kinetics of proteins from such devices, the applicants recently provided the first structural data on proteins within biocompatible polymers. The overall objective of this proposal is to apply the newly developed spectroscopic methods to further rationalize the impact of the encapsulation conditions on the structure of model proteins and relate structural with release and stability data. The ultimate goal is to understand the structure and stability consequences of protein encapsulation in biocompatible polymers to provide rational formulation strategies. To this end they will primarily employ Fourier-transform infrared (FTIR) spectroscopy to quantitatively characterize changes in the secondary structure of model proteins at various stages of their encapsulation. In addition, high-resolution H/D exchange NMR spectroscopy will be applied to gain complementary structural data. The structural data will be correlated with stability parameters, such as cumulative release of the proteins from the devices and their specific biological activity. They will, in particular, concentrate on optimizing non-aqueous encapsulation approaches, where they have already achieved structural preservation of two model proteins (recombinant human growth hormone and bovine serum albumin) upon encapsulation in FDA-approved poly(lactic-co-glycolic)acid. In addition, the most common method used for protein encapsulation, the double emulsion solvent evaporation technique, will be systematically analyzed by variation of the processing parameters. They are particularly interested in the stabilization of proteins in the detrimental first encapsulation step, where an aqueous-organic solvent interface is formed and protein solutions are subjected to high shear forces. They will also address the conformational. Stability of proteins in organic solvents experimentally, particularly focussing on the influence of additives on their thermal stability.