Patterned and switchable surfaces for biomaterial applications

Andrew Hook – Patterned and switchable surfaces for biomaterial applicationsthat the most significant thermodynamic force for the adsorption of DNA isentropically favourable surface dehydration, whilst hydrogen bond formation alsocontributed to the interfacial interaction. Kang et al. [201] were able to visualise inreal-time the adsorption of individual DNA molecules on silica using total internalreflection fluorescence microscopy. Interestingly, the report revealed the importanceof hydrophobic interactions. DNA adsorption was only observed at a pH below 4.5,where the DNA surface concentration increased with decreasing pH. Thehydrophobic interactions were more significant for single stranded DNA, suggestinginteractions of the surface with the nucleobases [22]. Adsorption of DNA tonegatively charged surfaces has also been observed due to the formation of cationicbridges often by the use of cations such as Mg 2+ [43]. Furthermore, Saoudi et al. [27]reported the adsorption of DNA to aminated polypyrrole silica particles, which had anear-zero surface charge where the charge contribution from protonated aminegroups was balanced by anionic silanol groups, suggesting that isolated positivelycharged groups and not a net positive surface charge is sufficient to stimulate DNAadsorption. DNA adsorption to polypyrrole is also closely related to dopantphosphateion exchange at the DNA/polypyrrole interface [202].The low protein ‘fouling’ behaviour of poly(ethylene glycol) (PEG) layers as wellas their ability to reduce cell attachment has been well studied [67, 203-206].However, the use and performance of PEG coatings in conjunction with DNAbinding has not been widely studied, despite evidence suggesting PEG is able toresist non-specific adsorption of DNA [207, 208]. Studies are limited to theadsorption of short, single-stranded oligomers, thus, investigation to longer anddouble-stranded DNA would be of interest, particularly for applications involving3-99