A novel colorimetric DNA biosensor for genetic assay purpose based on gold nanoparticles self-assembled onto a functionalized glass surface

Abstract

Abstract We have demonstrated a novel DNA sensing strategy employing S-H labeled DNA modified glass surface to detect a synthetic target DNA by an inexpensive spectrophotometric method. Firstly a well cleaned glass surface was functionalized with 3-(mercaptopropyl) trimethoxysilane (MPTS) and was self-assembled with gold nanoparticles and then a thiol modified ss-DNA was immobilized onto gold nanoparticles. After methylene blue (MB) accumulation, MB interacted with free guanine base of single strand DNA and absorbed onto glass surface. In this step the absorbance of accumulated MB on the modified glass surface was measured at the λ max of MB. After immersion of the ss-DNA modified glass surface in the target DNA solution, hybridization between probe and target DNA occurred. In this step because of the hybridization the free guanine bases on the glass surface decreased and hence less MB absorbed onto glass surface and its absorbance decreased. This decrease in MB absorbance was in linear relationship with addition of target DNA and can be viewed by naked eye and detected by spectrophotometric method. The linear range of the developed biosensor for determination of complementary target DNA was from 1 to 300 nM with a detection limit of 0.6 nM.