IT03. Bio-nano sensing and instrumentation: Evolution and trends

Abstract

Summary form only given. The non judicious application of a particular class of pesticides - organophosphates (OPs) to control agricultural pest has become a serious environmental issue leading to soil and subsequently surface & ground water pollution. The environmental concerns regarding persistence of organophosphates and toxic metabolites in soil and ground water has stimulated the research to develop rapid and sensitive bio-assay. Fluorescence-based biosensors have generated considerable interest over other biosensors as they allow the safe non electrical remote sensing of materials in hazardous or sensitive environments which derive an analytical signal from the fluorescence emission process. Recently, there has been an intense research effort to develop biosensor devices for the determination of organophosphorus pesticides (OPs) and Organophosphorus hydrolase (OPH), a biological catalyst, can effectively catalyze the hydrolysis of wide range of OPs resulting in the detection of these pesticides. Detection of OPs has been demonstrated by the conjugation of Organophosphorus hydrolase (OPH) and the fluorophorei.e 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS or pyranine). The hydrolysis of the OPs by the enzyme decreases the pH in its vicinity which is being detected by the pH reporter fluorophore. The fluorophorepyranine has excitation at 460 nm and emission at 510 nm which can be used as pH indicator in the pH range of 7-10 and this has been monitored by developing the associated instrumentation. Enhancement in fluorescence detection signal was observed when amine functionalized silver nanoparticles were covalently attached to OPH6His-pyranine conjugate due to `Metal Enhanced Fluorescence' which in turn has resulted in lower detection limits of ~ 2ppb for paraoxon which are much better as compared to other enzyme based biosensors for organophosphate pesticides. The enhancement in the sensitivity of the biosensing assay due to introduction of silver nanoparticles with amine group is because of the metal enhanced fluorescence and stability of the bond between AgNPs and bioconjugate comprising of OPH6His-pyranine. This opens the possibility of the assay to be used for rapid field detection for organophosphates and contributing towards preserving environment.