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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.

Since bacterial infections associated with implants remain a major cause of their failure, this study investigated the use of polyelectrolyte multilayers (PEMs) comprising hyaluronic acid (HA) and chitosan (CH) to confer antibacterial properties on titanium (Ti). HA and CH were deposited on Ti using the layer-by-layer deposition method. The antibacterial efficacy of the functionalized Ti substrates was assessed using Escherichia coli and Staphylococcus aureus. The number of adherent bacteria on Ti functionalized with HA and CH PEMs was up to an order of magnitude lower than that on the pristine Ti. The effects of chemical crosslinking of the PEMs on the structural stability and antibacterial efficacy were investigated. The chemical crosslinking of the PEMs imparts greater structural stability and preserves the antibacterial properties even after the prolonged immersion in phosphate-buffered saline. The cytotoxicity of the PEMs to osteoblasts was evaluated using the MTT assay. The results showed that the biocompatible and long-lasting antibacterial nature of the functionalized Ti substrates offers great potential for reducing implant-associated infections.

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