Oligo-DNA Immobilization and Hybridization on Polyelectrolyte-Modified Surfaces

Aleksei Solomonov aleksei.solomonov@weizmann.ac.il Alexander Vaskevich Israel Rubinstein
Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel

Layer-by-layer adsorption on polyelectrolyte multilayers (PM) presents a convenient technique for surface functionalization. Initially developed for a sequence of oppositely charged polymer pairs, it was extended to polymers bound by hydrogen bonds including DNA. However, short oligo-DNA molecules electrostatically adsorbed on PM are prone to be released into solution, impeding the use of the method in biosensing applications.

In the present work, single- and double-stranded DNA molecules were adsorbed on PM of polyallylamine hydrochloride (PAH) and polystyrenesulphonate (PSS) formed on glass or gold island films. Labeling of oligo-DNA (23 mer) strands by chromophores (Cy5 and D2) allowed monitoring of both DNA probe immobilization and binding to complementary DNA using transmission UV-vis and by fluorescence spectroscopy. For gold island films accumulation of PM and oligo-DNA was also followed by LSPR spectroscopy.

DNA probes immobilized on PM showed high (up 1.1ยท1013 molecules/cm2) surface coverage. In agreement with previous studies, we found gradual desorption of DNA during washing and hybridization/melting cycling. Stabilization of recognition interface was achieved using covalent coupling of DNA to PM. Amine-terminated DNA was adsorbed on PM with outer PAH layer following by cross-linking with glutaraldehyde and reduction with sodium cyanoborohydride. Cross-linked DNA-PM layer retained high hybridization yield for complementary DNA binding is close to 100%, while surface coverage in hybridization/melting cycling remained constant. Variation of the number of PAH/PSS bilayers had no effect on the interface stability. Even single PAH-DNA bilayer showed the same specific binding of complementary DNA.

Stabilization of DNA-PM interface allowed the measurement of denaturation profiles of surface-bound DNA for complementary and unrelated strands. Melting temperature of double-stranded DNA linked to the surface was close to the value found in solution. Therefore, we assume that stepwise binding of the complementary strand to the DNA-PM interface results in the double helix formation.

Prof. Israel Rubinstein passed away on October 21, 2017.









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