چكيده فارسي :
We report herein the development of a highly sensitive colorimetric method for the determination of glutathione, based on the non-identical interaction of the citrate capped gold nanoparticles (AuNPs) and glutathione at two different pH values. The main point of the proposed method is the formation of aggregated and dispersed AuNPs at two pH values. This was exploited from high affinity of low-molecular-weight aminothiols towards the Au NPs surface, which could induce displacement of the citrate shell by the thiolate shell of target molecules, resulting in aggregation of the NPs through intermolecular electrostatic interaction or hydrogen-bonding at proper pH values. As a result of aggregation, this can be affected by the ionic strength, pH and concentration of Au NPs, the plasmon band at around 519 nm decreases gradually, along with formation of a new red shifted band [1]. Because of the presence of hydroxyl, carboxyl and amine groups in glutathione, pH is the critical parameter that should be taken into consideration [2]. We have developed a simple and highly sensitive colorimetric method for detection of glutathione with the bare eye or UV-vis spectrometry based on the aggregation size-dependent optical property of citrate capped spherical Au NPs, through utilizing the strong pH-dependent interaction of the thiol group towards the surface of the Au NPs [3]. The effects of affecting parameters, including concentration of NPs, ion strength and pH have been investigated to find the optimized condition, with highest sensitivity and selectivity [4].
