Gold-nanoparticle-based miniaturized laser-induced fluorescence probe for specific DNA hybridization detection: studies on size-dependent optical properties

A compact, highly specific, inexpensive and user friendly optical fibre laser-induced fluorescence (LIF) sensor based on fluorescence quenching by nanoparticles has been developed to detect single-strand (ss-) DNA hybridization at femtomolar level. The fluorescence of fluorophore-tagged ss- DNA increases by a factor of 80 when it binds to a complimentary DNA, while the addition of single-base mismatch DNA had no effect on the fluorescence efficiency. We present theoretical and experimental results on dye fluorescence quenching induced by gold nanoparticles having different particle sizes. Fluorescence spectra clearly show that the quenching efficiency decreases with increasing size of the gold nanoparticles and increasing the distance between dye and nanoparticles. The mechanism of size- and distant-dependent fluorescence quenching has been discussed. Effects of various influential experimental parameters and configurations were investigated in order to optimize and miniaturize the sensor performance.