Patterned and switchable surfaces for biomaterial applications

Chapter 1 - IntroductionOnce released from the surface, DNA is able to diffuse in solution, sooncontacting the surface of cells that are growing above the DNA loaded patches. Fromhere, the polyanionic DNA must permeate the cell membrane, which typically alsohas an overall negative charge. From the methods usually used to facilitatetransfection, only few can be used in a solid phase transfection scenario.Commonly, transfection reagents such as the commercially available Effecteneand Lipofectamine TM reagents, are used to assist transfection in TCMs [8, 35, 101].The transfection reagent is either mixed with DNA before spotting or afterwards,added on top of the DNA spots. Alternatively, inclusion of cationic polymers into thesubstratum enhances transfection due to the increased capacity for the surfacebinding of DNA resulting in an increased DNA concentration at the surface ofattached cells and increased membrane permeability of DNA-cationic polymercomplexes, which have a lower surface charge than bare DNA [163, 167].A limited number of transfection methods have also been described for TCMapplications as alternatives to the use of cationic polymers. Lentiviruses have beenutilised for the transfection of a number of primary and transformed mammalian cellsin a cell microarray format for both the overexpression of a particular gene andRNAi studies [168, 169]. Lentiviruses are advantageous over other transfectiontechniques in their ability to transfect a wide variety of cell types with a highefficiency. Another method developed to enhance DNA uptake is the use ofelectroporation [170]. The advantages of this approach is its ability to initiate bothDNA release from the surface and subsequent uptake into the cells through transientpores in response to the application of a voltage.Of particular interest have been studies showing that the interactions of ECMproteins enhance transfection efficiency [171-173]. The particular type of ECM1-56