Tone Reversal of an AFM Lateral Force Image Due to Hybridization of Oligonucleotides Immobilized on Polymers

The interaction between oligonucleotide strands and polymer chains on surfaces has been investigated by AFM and XPS, with cyclo-olefin-copolymer (COC) and polycarbonate (PC) as model polymers (see image). Lower friction recorded by the AFM tip when mapping the aggregates of covalently bound amino-terminated ssDNA chains on COC and PC surfaces can be explained by the preferential orientation of the free hydrophobic bases towards the outside of the aggregates; hybridization of the ssDNA aggregates leads to tone reversal of the lateral force image.