(112b) Carbon Microspheres as Network Nodes in a Novel Biocompatible and Biodegradable Gel Matrix

Crab shell-derived chitosan is a linear copolymer composed of glucosamine and N-acetylglucosamine residues. By attaching n-dodecyl tails to the chitosan backbone, an associating biopolymer is formed, where hydrophobic interactions can lead to a macromolecular, viscoelastic network. Both types of chitosan have biocompatible and antibacterial properties, leading to many pharmaceutical and surgical applications, including use as biodegradable wound dressings and sutures. Chitosan is usually obtained from seafood-processing wastes (crab, shrimp and lobster shells), making its production environmentally friendly. Previous studies have shown that this biopolymer is able to gel cells and vesicles, indicating that a novel drug delivery system, using drugs encapsulated inside vesicles or liposomes, may be developed. We investigate the addition of this hydrophobically-modified biopolymer to monodisperse hard carbon spheres (HCS) (diameters of 300 nm to 1.2 microns), combining the biocompatible, gel-inducing properties of chitosan with the friction-reducing properties of HCS for application as biological lubricants. Due to their spherical, monodisperse properties, the HCS show excellent potential as lubricants, yielding initial coefficients of friction as low as .04, on par with Teflon and approaching that of synovial fluid. However, past studies have been unable to keep the HCS in place long enough to be effective as synthetic cartilage. With the addition of the modified chitosan, the hydrophobic tails of the biopolymer may interact with the hydrophobic surfaces of the HCS to gel the solution and keep the carbon particles in place for stable, long-term joint lubrication. Studies are being carried out to analyze the stability, concentration/coefficient of friction relationship and mechanical properties of these samples, in order to determine whether the materials have potential as long-term biological lubricants or vehicles for drug delivery.