Mineral deposit on mechanically active cardiovascular prosthesis can result premature failure of the device. This proposal addresses three general approaches to prevent or reverse the calcification process and describes and in vitro model system to evaluate the effectiveness of these methods. The first approach involves pretreatment of the hydrophobic polymers with surfactants which have a diphosphonate, phosphate, sulfate or carboxylate polar head group. The carboxylate group is thought to enhance mineralization while the three other groups are reported to inhibit calcium deposition. Increasing alkyl chains (C-8, C-12, C-18, C-24) will be prepared for each functional group. The inhibitors will be entrapped in the polymer and their long term stability evaluated along with changes in bulk and surface characteristics of the polymers. The second area of investigation is specifically aimed at reversing mineralization by changing the physicochemical environment at the blood contacting interface. Both temperature and pH are important factors in calcification and can be controlled by altering the pneumatic drive system (CO2 or Air) and the gas temperature. These parameters can be manipulated to fabor calcium dissolution. The third approach will explore fabrication parameters that contribute to microbubble formation on the polymer surface. This type of fabrication defect can serve as a site for mineralization. Casting conditions will be varied to determine the factors that contribute to microbubble fomration. Changes in relative humidity, solvent systems, atmosphere, and curing temperature will be evaluated to determine their contribution to microbubble formation. The consequences of these approaches will be evaluated using an in vitro calcification system. Information from this study will provide realistic alternatives to prevent mineral deposition or enhance mineral dissolution on elastomeric blood pumps.
| Dong, D E; Andrade, J D; Coleman, D L (1987) Adsorption of low density lipoproteins onto selected biomedical polymers. J Biomed Mater Res 21:683-700 |
