Nano-scaled hydroxyapatite/polymer composite II. Coating of sintered hydroxyapatite particles on poly(2-(o-[1 -methylpropylideneamino] carboxyamino) ethyl methacrylate)-grafted silk fibroin fibers through covalent linkage

Abstract

Hydroxyapatite (HAp) has been applied to various biomaterials because of its good biocompatibility for hard and soft tissue. A percutaneous device with sintered HAp was developed by Aoki et al. but had the disadvantage of limiting a patient’s mobility due to the rigid ceramic disc [1, 2]. We have developed nano-scaled HAp particles and a HAp/polymer composite to add further improvement in the application of HAp to this device [3–6]. It is expected that this HAp/polymer composite can be developed as percutaneous implant material. Silk fibroin (SF) shows good qualities for biomaterials because of its unique physicochemical properties [7]. It is expected that SF can be applied to a polymer substrate of the composite with HAp since SF can add appropriate flexibility to the inorganic material. In our former paper [8], we reported the coupling between a nano-scaled HAp and a poly(γ -methacryloxypropyl trimethoxysilane)-grafted SF through vinyl bonds of 2-methacryloxyethyl isocyanate (IEM). This synthetic way requires, however, a three-step procedure and is complicated. In this report, to improve the method of synthesizing a novel composite consisting of HAp particles and SF through covalent linkage, therefore, we adopted the graft-polymerization with 2-(o-[1′-methylpropylideneamino] carboxyamino) ethyl methacrylate (IEM blocked with oxime; IEMoxime) onto the SF by free radical initiation. This is because blocked isocyanate groups combining with HAp can be introduced onto the SF by only one step.