Colorimetric sensing of glucose using plasmonic gold nanoparticles.

Colorimetric sensors are extensively explored class of optical biosensors due to the visible eye detection enabled by them. An efficient way of colorimetric sensing can be achieved by studying the surface plasmon resonance (SPR) properties of noble metal nanoparticles like gold, silver etc. The SPR band of gold nanoparticles is influenced not only by their size and shape but also by the dielectric properties of the environment and the proximity of other nanoparticles which make them most suitable candidates for colorimetric sensing applications. In this work, we developed a novel, rapid, enzyme free colorimetric assay for glucose level determination. The normal levels of glucose in human blood range from3.8 to 6.9 mM approximately, although these levels may change during the day, being lower upon fasting and reaching a peak in post-cenal states. Both high and low glycemic levels are detrimental for health status. Glucose of various physiological concentrations (3 mM-50 mM) acts simultaneously as reducing and capping agent for the gold nanoparticle synthesis from tetrachloroauric acid enabling its label free detection. The increase in glucose concentration from normal to diabetic range cause a colour change from blue to red. The localized surface plasmon resonance (LSPR) peak is shifted from 520 to 580 nm due to the agglomeration of gold nanoparticles at lower concentrations of glucose. [ABSTRACT FROM AUTHOR]