Patterned and switchable surfaces for biomaterial applications
Patterned and switchable surfaces for biomaterial applications
Patterned and switchable surfaces for biomaterial applications
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Andrew Hook – <strong>Patterned</strong> <strong>and</strong> <strong>switchable</strong> <strong>surfaces</strong> <strong>for</strong> <strong>biomaterial</strong> <strong>applications</strong>oligonucleotide solution (Figure 2.6A). After the application of a positive voltage(Figure 2.6B), <strong>and</strong> subsequent washing (Figure 2.6C) the pattern persisted, whilst thepattern disappeared after applying a negative bias (Figure 2.6D) suggesting thecomplete removal of oligonucleotide. These results can be taken as evidence that theapplication of a positive or negative voltage stimulated the adsorption or desorptionof DNA. However, additional factors such as the stringency of the washings <strong>and</strong>background adsorption at 0 V bias needed to be considered. A fading of thefluorescence was observed upon successive rinsing, even at +1.5 V bias (data notshown), suggesting that the washing protocol could influence the results of thefluorescence studies. There<strong>for</strong>e, to independently investigate voltage bias inducedDNA adsorption, an experiment was conducted without washing. Oligonucleotidewas injected over the patterned surface (Figure 2.6E) <strong>and</strong> a higher fluorescenceintensity was observed on the ablated ALAPP regions. Once +1.5 V was applied tothe surface, an increased fluorescence intensity was observed on the chip surface,suggesting an increase in the amount of DNA adsorbed to the surface due to biasen<strong>for</strong>cedadsorption of the oligonucleotide to the surface (Figure 2.6F). However,adsorption in this case was not discriminative between ALAPP <strong>and</strong> the PEG<strong>surfaces</strong>, suggesting that prevention of DNA adsorption by the PEG layer wasovercome by the application of a positive voltage. A similar electrostatic effect hasbeen documented <strong>for</strong> proteins [84]. Furthermore, the application of -1.5 V resulted inthe release of oligonucleotide from the surface as witnessed by a decrease influorescence (Figure 2.6G) both on ALAPP <strong>and</strong> PEG regions, suggesting that theattractive interactions between the DNA <strong>and</strong> ALAPP are overcome by theapplication of the negative voltage. However, a faint contrast remains in Figure 2.6G2-83
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