Développement d'un hydrogel fonctionnalisé comme biomatériau de recrutement cellulaire pour l'ingénierie tissulaire

Chronic coronary syndrome often requires the surgical replacement of coronary arteries. It is a worldwide hope to develop small-diameter vascular grafts that can replace autologous vessels use in clinics. The development of a functional biocompatible coating to avoid thrombogenesis and promote endothelialization is essential to the development of small diameter vascular grafts. We propose here to combine the properties of type I collagen, the main protein forming the vascular extracellular matrix with weak antigenicity and heparins, used as anticoagulant in clinics, to achieve this goal. Therefore, low molecular weight heparin and unfractionated heparin at three different concentrations (1, 6 or 10 UI/mL) were added to collagen-based hydrogels formed by pH-driven self-assembly. These heparinized collagen-based hydrogels were evaluated for their physicochemical properties (gelation kinetic, swelling, spreading, viscoelastic properties, stability and heparin loading), their biocompatibility (albumin adsorption, endothelial cells growth) and their capacity to release active heparins with antithrombotic properties (standard clotting times, thrombin generation test). The heparinization of collagen-based hydrogels did not influence their gelation kinetic formation, swelling, or stability in human albumin solution. However, hydrogel spreading on a collagen coated surface was facilitated by the increase in both type of heparin loading attested by a decrease in contact angle and hydrogel height. The specific heparin content was directly quantified using FITC-labeled heparins showing that heparin loading in collagen-based hydrogels increased along the initial concentration of both heparins types used to prepare the gels. Although collagen-based hydrogel prepared with 10 UI/mL had the highest heparin content, its incorporation ratio of 25% for LH10 and 44% for UH10 was identical to the one of collagen-based hydrogel prepared with 6 UI/mL. Therefore, the study of viscoelastic properties of hydrogel was continued with collagen-based hydrogels prepared with 1 and 6 UI/mL. The highest heparin concentration resulted in the formation of a softer hydrogel. Moreover, heparin released from collagen-based hydrogels during three hours delayed blood coagulation (activated partial thromboplastin time and thrombin time) and decreased or abolished thrombin generation in the presence of platelets, with low albumin adsorption and no impact on cell viability compared with non-heparinized collagen-based hydrogel. Moreover, collagen-based hydrogel had the potential to retain heparin for at least seven days of culture with endothelial cell, providing the possibility of long-term antithrombotic properties. Finally, the functionalization of collagen-based hydrogel prepared with 6 UI/mL of both heparins was achieved with monocyte chemoattractant protein-1. Its loading was enhanced when collagen-based hydrogels were heparinized with unfractionated heparin.