Biocompatibility Modification Of Solid Materials Via Living Free Radical Polymerization

In this thesis, following works have been carried out: a) functional monomers were grafting on the surface of stainless steel by surface-initiated atom transfer radical polymerization, to enhance biocompatibility of the SS surface; b) surface-initiated atom transfer radical polymerization was employed to modified the surface of silk fibroin, to get a silk fibroin biological material with controllable cell adhesion, spread and detachment. The detailed results can be summarized as follows:(1) Biocompatible surface of stainless steel modified by surface- initiated atom transfer radical polymerization. Polished 316L stainless steel (SS) was first treated with air plasma to enhance surface hydrophilicity and was subsequently allowed to react with 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane to introduce an atom transfer radical polymerization (ATRP) initiator. Accordingly, the surface-initiated atom transfer radical polymerization of polyethylene glycol methacrylate (PEGMA) was carried out on the surface of the modified SS. The grafting progress was monitored by water contact angle measurements, X-ray photoelectron spectroscopy and atomic force microscopy. The polymer thickness as a function different polymerization times was characterized using a step profiler. The anticoagulative properties of the PEGMA modified SS surface were investigated. The results showed enhanced anticoagulative to acid-citrate-dextrose (ACD) blood after grafting PEGMA on the SS surface.(2) Surface-functionalized silk fibroin film with controllable cell adhesion by surface-initiated atom transfer radical polymerization. Surface-initiated atom-transfer radical polymerization (ATRP) was employed to tailor the functionality of silk fibroin (SF) film surface in a well-controlled manner. A simple two-step method, involving the activation of surface amide groups with formaldehyde and the reaction of the resulting N-methylol polyamide with 2-bromoisobutyryl bromide, was developed for the covalent immobilization of ATRP initiators on SF films surface. Functional polymer brushes of N-isopropylacrylamide (NIPAAm) and 2-hydroxyethyl methacrylate (HEMA) were prepared via surface-initiated ATRP from the SF films. The dormant chain ends of the grafted NIPAAm polymer [P(NIPAAm)] and HEMA polymer [P(HEMA)] on SF films could be reactivated for the consecutive surface-initiated ATRP to produce the corresponding SF films functionalized by P(NIPAAm)-b-P(HEMA) and P(HEMA)-b-P(NIPAAm) diblock copolymer brushes. Surface cultures of the 3T3 cell line on the functionalized SF films were evaluated. At 37oC [above the lower critical solution temperature (LCST, 32oC) of P(NIPAAm)], the seeded cells adhered, spread, and proliferated on the SF films grafted by P(NIPAAm) [SF-g-P(NIPAAm)] surface. Below the LCST, the cells detached from the SF-g-P(NIPAAm) surface spontaneously. The SF film with P(HEMA) grafted surface resisted attachment and growth of this cell line. SF films grafted with P(NIPAAm)-b-P(HEMA) and P(HEMA)-b-P(NIPAAm) diblock copolymer brushes showed the similar cell attachment/detachment with that of P(HEMA) and P(NIPAAm) modified SF films, respectively. Thus, the functionalized SF films can be potentially useful as SF-based biomedical materials, such as wound dressing, wound healing material and cell cultivation substrates. The methodology used in this paper also offer opportunities for further surface modification of functional materials derived from SF protein.