Microfluidic chip-photothermal lens microscopy for DNA hybridization assay using gold nanoparticles

A new approach employing a microchip in combination with photothermal lens microscopy has been described for a DNA hybridization assay using gold nanoparticles. The difference in adsorption propensities of single- and double-stranded DNAs on gold nanoparticles was used for a highly sensitive DNA hybridization assay through a photothermal lens effect in a femtoliter scale of detection volume. Under the optimized conditions, the results showed that the variation of photothermal lens signal in the focal volume of 105 fL (10(-15) L) was linearly proportional to the target DNA concentration over the range of 50-500 nM with detection limits of 30.7 nM and 27.3 nM for target DNA I and II, respectively. The lowest amount of target DNA that was measured using gold nanoparticles was 2.6 zepto mole. The assay was completed within 5 min and the relative standard deviations (n = 8) for both target DNAs were about 2.34%. The hybridization process was proved by two different common methods including gel electrophoresis and in situ fluorescence monitoring of DNA hybridization. The performance of this detection method was investigated in diluted human serum sample as a complex sample. The recovery values were between 98 and 104.9%. Graphical abstract