Patterned and switchable surfaces for biomaterial applications

Chapter 2 – Spatially controlled electro-stimulated DNA adsorption and desorption for biodeviceapplications750 and -1000 mV was applied for 2 min to samples after 4 hr preincubation withplasmid to allow cell attachment. Transfection efficiencies were measured after afurther 20 hr incubation and are shown in Figure 2.8. When -250 mV was applied noimprovement in transfection efficiency was observed as compared to when novoltage was applied (Figure 2.8A). However, an increase in transfection efficiencyabove 13% (transfection efficiency when no voltage was applied) was observedwhen voltages greater than -250 mV were applied with a maximum of 21%transfection efficiency attained upon application of -750 mV. Previous electrostimulatedDNA desorption experiments (Figure 2.7) suggested that -250 mV wasnot sufficient to overcome DNA-ALAPP interactions and, thus, drive DNAdesorption, which only resulted at the application of higher voltages (Figure 2.7).This result strongly suggests that the key mechanism to enhanced transfectionefficiency by application of a voltage bias to the DNA-constraining substrate in therange of -500 mV to -750 mV is a result of the increased availability of DNA foruptake by nearby cells due to the electro-stimulated desorption of otherwise boundDNA from the surface overcoming DNA-surface interactions. This is clearly shownby the failure of -250 mV to enhance transfection efficiency whereupon this voltagealso does not electro-stimulate DNA desorption. Transfection efficiency was seen todecrease back to 12% when -1000 mV was applied. Presumably, this was caused bya decrease in the viability of cells as a result of the higher voltage application. As-750 mV was observed to cause the highest increase in transfection efficiency it wasselected for further studies. -750 mV voltage was applied for 0, 0.5, 1 and 5 min tosamples after 4 hr preincubation with plasmid with a subsequent 20 hr incubationbefore analysis. An increase in transfection efficiency was observed when the lengthof time -750 mV was applied for was increased from 0-1 min (Figure 2.8B). No2-90