Renewable Biomaterials from Bovine Serum Albumin

Abstract

Bovine Serum Albumin (BSA) is one of the most abundant proteins from the livestock industry, and it has been widely used in biomedical research as a reagent. However, only limited areas of application and a very small amount of BSA is utilized. Comprehensive research to discover novel renewable protein based biomaterials as well as innovative cost-effective solution for its biomedical application is attempted in the following projects. These projects may have profound impacts on protein based biomaterials development and utility of by-product from agriculture. In the first project, BSA was made to aggregate into long, linear fibers. Production of fibers occurs on a glass surface where dehydration conditions can be manipulated so that directional drying results in a linear protein aggregation. Interactions between BSA and salts suggest that removing the inner water shell surrounding the globular protein leads to protein unfolding and aggregation at the water/air interface. Fibril elongation is controlled by drying rate, chemical makeup, as well as solution geometry on the glass surface. Tensile testing of the product suggested crosslinked fibers are comparable with silk in mechanical properties. BSA fibers can be formed into larger assemblies such as yarns, and dyed with desired colorants, thus, possessing foreseeable potential for future industrial-scale development. In the second project, BSA and low molecular weight polyethylene glycol (PEG) were reacted in a single-step reaction to synthesize translucent hydrogels with a Sol-Gel transition attemperatures between 37°C and 40°C. Gelation occurred by aggregation of smaller assemblies of BSA-PEG precursors at minutes time scale. The Sol-Gel transition concentration is depending onthe molecular weight of PEG and lies at temperatures below 35°C. Above 45°C, phase separation occurred that resulted in the precipitation of BSA-PEG from the solution. Microscopic examination of the gel revealed a porous structure with BSA-PEG forming the network with water filling in the spaces. At a low grafting ratio, BSA preserved its native secondary and tertiary structures and maintained its capacity for binding and enclosing small molecules. Drug delivery using the BSA-gel was assessed by a discontinuous method in vitro with 5-fluorouracil. Degradation tests with trypsin confirmed that the hydrogels were biodegradable. This novel material holds promise for biomedical applications as a potentially drug delivery vehicle for hydrophobic drugs which is difficult to be incorporated with other hydrogels. In the third project, BSA was employed as a model protein to create a cost-effective artificial Model ECM (extracellular matrix) for potential tissue engineering applications. For this purpose, reduced BSA was PEGlyated and glycosylated to synthesize a linear glycoprotein as the major component of ECM. The glycosylated protein was crosslinked with EDC to mimic the mesh structures of native ECM. Coating and 3D porous structures were created by varying solution concentration and different fabrication steps. NIH 3T3 cells were cultured on 2D and 3D scaffold. Good cell adhesion, confluence and viability were achieved compared to those by collagen and tissue culture polystyrene. It is hypothesized that glycoprotein composition and specific morphology of the assembly will provide favorable circumstances for cell growth. Such ECM could eventually serve as an alternative culturing method for the more expensive collagen and fibronectin based materials currently in use and render tissue engineering more affordable.