Selective Amplification of SPR Biosensor Signal for Recognition of rpoB Gene Fragments by Use of Gold Nanoparticles Modified by Thiolated DNA

An experimental approach for improving the sensitivity of the surface plasmon resonance (SPR) DNA hybridization sensor using gold nanoparticles (GNPs), modified by specific oligonucleotides, was elaborated. An influence of the ionic strength on the aggregation stability of unmodified GNPs and GNPs modified by the thiolated oligonucleotides was investigated by monitoring a value of light extinction at 520 nm that can be considered as a measure of a quantity of the non-aggregated GNPs. While the unmodified GNPs started to aggregate in 0.2 × saline-sodium citrate (SSC), GNPs modified by the negatively charged oligonucleotides were more stable at increasing ionic strength up to 0.5 × SSC. A bioselective element of the SPR DNA hybridization sensor was formed by immobilization on the gold sensor surface of the thiolated oligonucleotides P2, the sequence of which is a fragment of the rpoB gene of Mycobacterium tuberculosis. The injections into the measuring flow cell of the SPR spectrometer of various concentrations of GNPs modified by the complementary oligonucleotides T2-18m caused the pronounced concentration-dependent sequence-specific sensor responses. The magnitude of the sensor responses was much higher than in the case of the free standing complementary oligonucleotides. According to the obtained experimental data, the usage of GNPs modified by specific oligonucleotides can amplify the sensor response of the SPR DNA hybridization sensor in ~1200 times.