Thromboresistant Silicones and Polyurethanes Prepared with Amphiphilic Surface-modifying Additives
Abstract
Silicones and polyurethanes (PUs) are often used in blood-contacting medical devices; however, their hydrophobicity makes them susceptible to non-specific protein adsorption and subsequent thrombosis. In this work, amphiphilic poly(ethylene oxide) (PEO)-based surface modifying additives (SMAs) were evaluated for their capacity to enhance surface hydrophilicity and thromboresistance. In prior studies, these PEO-silane amphiphiles [PEO-SA; α-(EtO)₃-Si-(CH₂)₂-ODMSm₋block-PEOn₋CH₃] exhibited rapid, substantial surface restructuring and protein resistance in a condensation cure silicone. Various SMA structures were assessed, including those of differing PEO (n = 3 – 16) and oligo(dimethyl siloxane) (ODMS; m = 0 – 30) repeat units. PEO-SAs with (XL diblock) and without (Diblock) the crosslinkable triethoxysilane (TEOS) group were also assessed to determine the impact on SMA modified silicone stability (e.g. water uptake and leaching). The TEOS group was determined to be unnecessary, particularly with a longer, m = 30, ODMS tether.
Herein, both XL diblock and Diblock PEO-SAs were prepared with ODMS lengths of m = 13 or 30, and constant PEO length (n = 8). As SMAs in a condensation cure silicone (5 – 100 µmol/g), these were assessed similarly to determine their minimum effective concentration and stability. PEO-SA modified silicones ≥ 25 µmol/g showed enhanced hydrophilicity and protein resistance that was sustained following aqueous conditioning. All modified silicones also had minimal water uptake and leaching, further indicating the TEOS group is not needed with a sufficiently long ODMS tether. Following this, the XL diblock, m =13 and Diblock, m = 30 PEO-SAs were tested as SMAs in silicone against whole human blood. Under both static and dynamic conditions, PEO-SA modified silicones showed effective resistance to protein adsorption and platelet adhesion at 10 µmol/g or greater.
Finally, the XL diblock, m = 13 PEO-SA was incorporated as SMAs in PU (5 – 100 µmol/g) to assess hydrophilicity, stability, and thromboresistance. PEO-SAs showed some immiscibility in PUs; however, the resulting modified PUs (at concentrations ≥ 25 µmol/g) exhibited increased hydrophilicity and good stability (i.e. low water uptake and leaching) following aqueous conditioning. Lastly, PEO-SA modified PUs (at concentrations ≥ 10 µmol/g) showed significantly reduced protein adsorption and platelet adhesion from whole human blood under static conditions.
Citation
Ngo, Bryan Khai Dinh (2020). Thromboresistant Silicones and Polyurethanes Prepared with Amphiphilic Surface-modifying Additives. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /191798.