Patterned and switchable surfaces for biomaterial applications

Chapter 1 - Introductionefficiencies are reported for reverse transfection experiments [29, 35, 101, 159]. Lowtransfection efficiencies are detrimental as each colony may consist of as little as 30cells, thus, in order to gain statistically credible data close to 100% transfectionefficiency is desirable. This is often not observed, limiting the technique to cell linessuch as HEK and monkey kidney fibroblasts (COS) where relatively hightransfection efficiencies are easily obtained [161], thus restricting the ability to studygenes in the desired cell lines. Lastly, the requirement to accurately observephenotypic changes within tens of thousands of cell colonies in a high-throughputfashion imposes a formidable challenge for TCM assay development.1.4.4.1. Methods to generate DNA microarraysThe first step for TCM construction is the spatially controlled deposition of DNAin a microarray format. This is typically achieved by either contact printing or noncontactprinting with a robotic spotter, CP or on-chip DNA synthesis [15, 82, 94,162]. DNA-gelatin mixtures are often utilised to ensure spatial confinement of DNAby physical entrapment [8, 101]. This can also be achieved by producing a surfacewith variations in hydrophilicity that effectively confine a DNA droplet to thehydrophilic regions, enabling DNA adsorption only in confined regions [100].Spatial control of DNA has also been achieved utilising the electro-responsivenature of DNA to form switchable patterns of DNA on a microelectronics chip [92].By application of the appropriate positive and negative voltages DNA can bespatially confined. The advantage of this system is the ability to induce surfacediffusion of DNA by reversing the polarity of the applied voltage. This technique islimited by the pattern of the electrodes but combines spatial control withswitchability for advanced DNA surface manipulation.1-50