Oligonucleotide/poly(l-lysine) complexes attachment on poly(styrene/maleic acid) and poly(styrene/maleic anhydride polymeric surfaces

The immobilization efficiency of the complexes of oligonucleotide/poly(L-lysine) onto Poly(Styrene/Maleic Acid), PSMA, and Poly(Styrene/Maleic Anhydride), PSMAA, has been investigated using X-ray photoelectron spectroscopy and atomic force microscopy (AFM) in conjugation with fluorescence-based measurements of DNA attachment. A mono-molecularly thin layer of either electrostatically or covalently (via amide bond) coupled poly(L-lysine) (PL) allows the 'switching' of the chemistry from a COOH-based to NH2-based one. The COOH-based chemistry has the advantage of a high yield of reaction but the disadvantage of a low surface concentration of DNA molecules (negative-negative electrostatic exclusion) whereas the NH2-based chemistry provides a higher surface concentration (positive-negative electrostatic attraction) but has a lower yield of covalent binding reaction. The immobilization efficiency of covalently coupled 26-mer oligonucleotides/poly(L-lysine) to polymeric surfaces was estimated as 0.3-0.5 x1012 molecules/mm2 for both polymeric surfaces studied. The electrostatic adsorption of poly(L-lysine)/oligonucleotides onto PSMA and functionalized PSMAA surfaces yielded 0.5 x 1011 and 0.1 x 1010 molecules/mm2, respectively. Although this mode of attachment is not 'covalent binding' per se, the evidence is provided that this attachment is strong enough to withstand PCR cycles. The properties of these oligonucleotide/poly(L-lysine) complexes make them promising candidates for DNA-DNA hybridisation assays and PCR.