Controlling whole blood activation and resultant clot properties by carboxyl and alkyl functional groups on material surfaces: a possible therapeutic approach for enhancing bone healing

Abstract

Most research virtually ignores the important role of a blood clot in supporting bone healing. In this study, we investigated the effects of surface functional groups carboxyl and alkyl on whole blood coagulation, complement activation and blood clot formation. We synthesised and tested a series of materials with different ratios of carboxyl (-COOH) and alkyl (-CH₃, -CH₂CH₃ and -(CH₂)₃CH₃) groups. We found that surfaces with -COOH/-(CH₂)₃CH₃ induced a faster coagulation activation than those with -COOH/-CH₃ and -CH₂CH₃, regardless of the -COOH ratios. An increase in -COOH ratios on -COOH/-CH₃ and -CH₂CH₃ surfaces decreased the rate of coagulation activation. The pattern of complement activation was entirely similar to that of surface-induced coagulation. All material coated surfaces resulted in clots with thicker fibrin in a denser network at the clot/material interface and a significantly slower initial fibrinolysis when compared to uncoated glass surfaces. The amounts of platelet-derived growth factor-AB (PDGF-AB) and transforming growth factor-β (TGF-β1) released from an intact clot were higher than a lysed clot. The release of PDGF-AB was found to be correlated with the fibrin density. This study demonstrated that surface chemistry can significantly influence the activation of blood coagulation and complement system, resultant clot structure, susceptibility to fibrinolysis as well as release of growth factors, which are important factors determining the bone healing process.