Synthesis and characterization of surface-grafted polyacrylamide brushes and their inhibition of microbial adhesion

A method is presented to prevent microbial adhesion to solid surfaces exploiting the unique properties of polymer brushes. Polyacrylamide (PAAm) brushes were grown from silicon wafers by atom transfer radical polymerization (ATRP) using a three-step reaction procedure consisting of immobilization of a coupling agent gamma-aminopropyltriethoxysilane, anchoring of an ATRP initiator 4-(chloromethyl)benzoyl chloride, and controlled radical polymerization of acrylamide. The surfaces were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, ellipsometry, and contact-angle measurements. The calculated grafting density pointed to the presence of a dense and homogeneous polymer brush. Initial deposition rates, adhesion after 4 h, and detachment of two bacterial strains (Staphylococcus aureus ATCC 12600 and Streptococcus salivarius GB 24/9) and one yeast strain (Candida albicans GB 1/2) to both PAAm-coated and untreated silicon surfaces were investigated in a parallel plate flow chamber. A high reduction (70-92%) in microbial adhesion to the surface-grafted PAAm brush was observed, as compared with untreated silicon surfaces. Application of the proposed grafting method to silicone rubbers may offer great potential to prevent biomaterials-centered infection of implants.</p

Anti-adhesive properties and physiological stability of surface-grafted polyacrylamide brush coatings

Biomedical implants based on synthetic polymers are being used more and more in medicine for applications such as joint replacement, vascular grafts, contact lenses and voice prostheses. Silicone rubber (SR) is an example of a non-biodegradable synthetic polymer that is very suitable for biomedical applications because of its good chemical, physical and physiological properties. Unfortunately, silicone rubber has two major drawbacks: (1) the presence of siloxane oligomers and/or catalyst residues that can easily diffuse out of the SR material and give rise to inflammatory reactions and (2) protein adsorption to the SR surface, leading to the formation of a harmful biofilm. In this thesis these two issues are investigated