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>aminated polypyrrole silica particles, which had a near-zero surface charge despitethe presence of protonated amine groups. The positive charges are compensated byanionic silanol groups. This study suggests that isolated positively charged groups<strong>and</strong> not a net positive surface charge are sufficient to stimulate DNA adsorption.Lemeshko et al., [28] investigated simplifying DNA microarray <strong>for</strong>mation byadsorbing DNA probes to a surface utilising the electronegative nature of DNA <strong>for</strong><strong>for</strong>mation of electrostatic interactions with a positively charged 3-aminopropyltrimethoxysilane modified surface instead of by covalent linkage. Adensely packed single-str<strong>and</strong>ed oligonucleotide layer was successfully adsorbed tothis surface, where the ssDNA oligomers were adsorbed side-on on the surface, <strong>and</strong>was used <strong>for</strong> subsequent hybridisation experiments that confirmed the accessibilityof the adsorbed DNA probes <strong>for</strong> the <strong>for</strong>mation of base pairs with complementarytarget DNA str<strong>and</strong>. Interestingly, asymmetric dissociation <strong>and</strong> DNAse digestion wasobserved <strong>for</strong> dsDNA <strong>for</strong>med in the manner described, whereupon, the hybridisedtarget DNA str<strong>and</strong>s dissociated quicker <strong>and</strong> were more heavily digested than theinitial electrostatically bound probes. This suggests that a typical DNA helix is not<strong>for</strong>med between these two str<strong>and</strong>s upon hybridisation.More recently, the polyelectrolytic nature of DNA has been utilised <strong>for</strong> <strong>for</strong>mationof multilayered films consisting of alternating layers of DNA <strong>and</strong> cationicpolyelectrolytes [32, 39-41]. One polycation commonly used is PEI, which has beenused to allow the adsorption of plasmid DNA to poly(lactic acid) (PLA) particles[42]. Yamauchi et al., [41] utilised this strategy to attain a very high DNA <strong>for</strong> TCM<strong>applications</strong>. Layer-by-layer assembly of PEI <strong>and</strong> plasmid DNA was utilised <strong>for</strong><strong>for</strong>mation of an electrode with a DNA of 0.6 g/cm 2 that was subsequently used <strong>for</strong>the transfection of cells adherent on the electrode.1-9
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