Vascularization Of Porous Hydroxyapatite Orbital Enucleation Implant Coated With Collagen/heparin Multilayers

Background:Orbital implants have been used for cosmesis following enucleation. Wearing appropriate ocular prosthesis after enucleation is an ideal treatment to reconstruct facial appearance. Vascularization is defined as the ingrowth of viable vascular connective tissue.It is possible that the inadequate vascularization of implants may contribute to the development of complications such as exposure.Therefore,improving the vascularization of orbital implant materials is an effective way to reduce the complications and improve the quality of patients’life.Aims:Multilayer of COL(Collagen)/HEP(Heparin) is developed in porous orbital implant via layer-by-layer (LBL) assembly to accelerate vascularization and improve biocompatibility. In vitro characterization of orbital implant materials provides a basis for further in vivo experiments. The complex orbital implant could be a promising approach for future clinical application. Methods:Collagen and heparin were selected as the building blocks to modify the porous HA orbital implant material by the LBL technique. Briefly, the porous HA scaffold was treated in COL solution and washed to ensure the charged state of the substrate. It was subsequently incubated in HEP solution to adsorb a layer of HEP, and then rinsed three times. In the next step, positively charged COL was assembled by incubating the HEP-enriched orbital implant in COL solution. The process was repeated until five bilayers had been deposited. The physical and chemical features, and the biological feature of the implant were characterised.Results:The content of COL/HEP multilayers in the interior of porous HA orbital implant measured by TG was0.87%. The degradation rate within one week in PBS was0.38%. The mechanical property of the material after assembly did not change significantly. CLSM observation, and MTT assay displayed that the orbital implant covered with five bilayers of COL and HEP had better cytocompatibility for endothelial cells comparing with the unmodified ones. The implant displayed the ability to support vasculogenesis by a chorioallantoic membrane (CAM) assay in vivo.Conclusions:Herein we have provided a practical and simple technique, LBL assembly, through which a cytocompatible material can be easily fabricated. The implant displayed the ability to support vasculogenesis in vitro. Our results suggested that the complex orbital implant could be a promising candidate for future clinical application.