A Simple Gold Nanoparticles Based Colorimetric Assay For The Detection Of Highly Reactive OH• Radicals

The design and development of simple methodology to measure short-lived OH. radicals is of considerable importance owing to the deleterious consequences associated with the oxidative stress that it can incur. Here, we describe a facile colorimetric assay that explores the plasmon absorbance of gold nanoparticles to realise rapid detection of OH center dot radicals. We have employed 4-hydroxy benzoic acid (4-HBA) as the reactive substrate that gives rise to a single hydroxylated product, protocatechuic acid (PCA) on reaction with OH center dot radicals. The resultant PCA showed capability of directly reducing Au3+ to give AuNPs while the original 4-HBA cannot reduce Au3+. The ensuing surface plasmon absorption of AuNPs was monitored for assaying the OH center dot radical activity. Redox active Fe2+ was used as a source of OH center dot radical and a linear relationship was observed between concentration of OH center dot radical and plasmon absorbance, allowing for quantitative estimation of OH center dot radical in solution.