Hybridisation of surface-immobilised single-stranded oligonucleotides and polymer monitored by surface plasmon resonance

We have investigated the hybridisation of thiol-modified single-stranded DNA embedded in a polyacrylamide layer through the technique of surface plasmon resonance (SPR). Kinetic studies were carried out by two different immobilisation methods: (a) SH-ssDNA was firstly attached on gold and the remaining free space was filled with polymer and (b) SH-ssDNA and the polymer was attached onto the surface from the same solution. The immobilisation methods were compared for various concentrations of SH-ssDNA. Hybridisation was dependent on both the immobilisation method and the concentration of the components. The highest hybridisation was obtained when SH-ssDNA and the polymer was immobilised from the same solution at low SH-ssDNA concentration or when high concentrations of oligos were spread onto the surface and the surface was post-treated with polymer. The target response corresponded to a surface coverage of 100±15ng/cm2. The same surface coverage on hybridisation was also obtained when low concentration of SH-ssDNA and polymer was attached onto the surface from the same solution. The non-specific binding of sample DNA was very low at optimal concentrations due to the polymer and the hybridisation was linearly dependent on target concentration.