In vitro hemocompatibility testing of UV-modified hyaluronan hydrogels

Hydrogels (hylans) based on cross-linked hyaluronan (HA) are potentially good biomaterials for vascular tissue engineering applications because they are highly non-antigenic and -immunogenic. To facilitate surface endothelialization, vital to vascular deployment, we irradiated the gel surface with low wavelength UV light. This process micro-textures the smooth gel surface to provide sites for cell anchorage and causes limited scission of native long-chain HA yielding smaller fragments that elicit an enhanced cell response. In the current in vitro study, we assessed the effects of UV irradiation on the short-term (<45 min) interaction between hylan gels and human blood cells (RBCs, platelets) and coagulation proteins at physiologic temperature. Although the lowered hydrophilicity of irradiated (UV) hylans elicited greater vascular cell response relative to unmodified (U) hylans, platelet deposition was unaffected and much lower compared to collagen-coated glass controls. The adhered platelets were rounded or mildly pseudopodic and did not express p-selectin, an activation marker. Both gel types induced identical, and minimal platelet release as measured using an platelet factor 4 ELISA, and identically deferred the intrinsic and extrinsic coagulation pathways. Both gel types induced elevated levels of contact activation of bound, but not plasma-phase factor XII relative to controls. Hemolysis rates were also identical and within accepted standards. We conclude that UV-treatment of hylans, useful to improve surface endothelialization, does not compromise their short-term hemocompatibility, vital to their use as vascular implant materials.