Patterned and switchable surfaces for biomaterial applications

Chapter 1 - Introductioncues to control cell growth. This technique has been widely used and is able topattern surfaces down to sub-micron dimensions, but suffers from the requirementfor rigorous laboratory protocols and high setup and maintenance costs.Photolithography has also been particularly useful for the patterning of proteins[81]. A number of approaches have been employed, but the general approachconsists of coating a surface with a photoresist that is subsequently patterned byphotolithography to re-expose the underlying material at specific locations. Thismaterial is functionalised, often by the use of silanes or self-assembled monolayers(SAMs) with a functional group that either adsorbs protein or is able to covalentlylink protein such as arylazide derivatives. The rest of the photoresist is subsequentlyremoved and the remaining re-exposed surface is functionalised with a low-foulingmaterial [81].Falconnet et al., [78] produced a chemically patterned platform for spatiallydirected cell growth based upon the spontaneous adsorption of PLL grafted PEG tonegatively charged surfaces, including oxides of niobium, titanium, silicon andindium tin as well as PS. A photoresist layer was coated onto niobium oxide coatedsilicon and patterned by photolithography using UV illumination. PLL-grafted-PEGfunctionalised with the RGD peptide was adsorbed onto the patterned surface, andthe remaining photoresist was subsequently removed by washing with an organicsolvent that did not disrupt the PLL-grafted-PEG layer. A pattern of functionalisedPLL-grafted-PEG remained on a surface of bare niobium oxide. The bare niobiumoxide was subsequently coated with non functionalised PLL-grafted-PEG, leaving apatterned surface with cell adhering regions separated by non-cell adhering regions.A pattern of human foreskin fibroblasts was successfully realised on this surface.1-18