Controlled surface graft polymerizations allowed a wide range of functionalities, from antibacterial effects to cell adhesion properties, to be imparted on titanium surfaces. A trichlorosilane coupling agent, containing an atom-transfer radical polymerization (ATRP) initiator, was first immobilized on the oxidized titanium (Ti−OH) surface to cater for the surface-initiated ATRP of 2-hydroxyethyl methacrylate (HEMA). The pendant hydroxyl end groups of the grafted HEMA chains were subsequently converted into carboxyl or amine groups to allow the coupling of gentamicin, penicillin, or collagen via the carbodiimide chemistry. The functionalized Ti surfaces were characterized by X-ray photoelectron spectroscopy and assayed for antibacterial activities or cell adhesion properties. The covalently immobilized antibiotics retain the antibacterial properties, as indicated by a significant reduction in the viability of contacting Staphylococcus aureus. The collagen-immobilized surfaces, on the other hand, promote fibroblast and osteoblast cells adhesion and proliferation. Thus, the present surface-initiated living radical graft polymerization technique allows the tailoring of the Ti surface with vastly different functions and is potentially useful to the design or improvement of Ti-based biomedical implants.

Surface-active microporous membranes were prepared from the poly(vinylidene fluoride)-graft-poly(2-(2-bromoisobutyryloxy)ethyl acrylate) copolymer (PVDF-g-PBIEA copolymer) by phase inversion in water. The PBIEA side chains could function as initiators for the atom transfer radical polymerization (ATRP) of 2-(N,N-dimethylamino)ethyl methacrylate on the membrane surfaces to give rise to the PVDF-g-PBIEA-ar-PDMAEMA membranes. N-alkylation with hexyl bromide and nitromethane gave rise to the quanternized PVDF-g-PBIEA-ar-QPDMAEMA membranes with polycation chains chemically tethered on the membrane surface, including the pore surfaces. The changes in the surface morphology and the surface chemical composition were confirmed by scanning electron microscopy and X-ray photoelectron spectroscopy. The scanning electron microscopy revealed that, in comparison to the pristine PVDF-g-PBIEA membranes, not only could the PVDF-g-PBIEA-ar-QPDMAEMA membranes remove the Gram-negative bacterium Escherichia coli but also inhibited the bacterial reproduction on the membranes to a significant extent.

Keratoprosthetic devices are subject to chronic inflammatory, pathological processes and the external environment that affect their stability and biocompatibility with the ocular surface and adjacent ocular tissues. We compared the corrosion resistance property and tissue-implant reaction of titanium oxide (TiO(2)) with hydroxyapatite (HA) in artificial tear fluid and a rabbit skin implantation model. The dissolution properties of the implant surfaces were evaluated with scanning electronic microscope (SEM) and atomic force microscope (AFM). Tissue inflammatory reactions were evaluated by Hematoxylin & Eosin staining, avidin biotin peroxidase complex (ABC) immunoassay and immunofluorescence. SEM and AFM images showed that there was less pitting corrosion on the surface of TiO(2) implants compared with HA. TiO(2) and HA exhibited a similar pattern of foreign body capsule formation and inflammatory cellular responses. The Collagen I/Collagen III ratio of the TiO(2) capsule was higher than that of the HA capsule. TiO(2) implants possess a high corrosion resistance property both in vitro and in vivo and the inflammatory cellular response to TiO(2) is similar to HA. With regards to corrosion resistance and inflammatory tissue responses, TiO(2) appears to be a promising material for keratoprosthetic skirt devices.

Crosslinked poly(4-vinylbenzyl chloride) (PVBC) microspheres of about 550 µm in diameter were first synthesized by suspension copolymerization of 4-vinylbenzyl chloride (VBC) in the presence of a crosslinking agent, ethylene glycol dimethacrylate (EGDMA). Subsequent surfaceinitiated atom transfer radical polymerization (ATRP) of 4-vinylpyridine (4VP), using the VBC units of PVBC on the microsphere surface as the macroinitiators, produced well-defined (nearly monodisperse) and covalently tethered poly(4-vinylpyridine) (P4VP) brushes. Quaternization of the tertiary amine groups of the P4VP brushes with hexyl bromide gave rise to a high concentration of quaternary ammonium salt (QAS) on the microsphere surfaces. The chemical composition of the microsphere surfaces at various stages of surface modification was characterized by X-ray photoelectron spectroscopy (XPS). The bactericidal effect of the QAS-functionalized microspheres on Escherichia coli (E. coli) was demonstrated. No significant loss in the surface bactericidal activity of the microsphere was observed during repeated applications.

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