ABSTRACT
The determination of thiol based biological molecules and drugs, such as cysteine (Cys) (I), α-lipoic acid (II), and sodium 2-sulfanylethane sulphonate (Mesna (III)) in human plasma are becoming progressively more important due to the growing body of knowledge about their essential role in numerous biological pathways. Herein we demonstrate a sensitive colorimetric sensor for the determination of medicinally important thiol drugs based on aggregation of the citrate capped silver nanoparticles (Ag NPs). This approach exploited the high affinity of thiols towards the Ag NPs surface which could tempt replacement of the citrate shell by the thiolate shell of target molecules, resulting in aggregation of the NPs through intermolecular electrostatic interaction or hydrogen-bonding. Because of aggregation, the plasmon band at around 400nm decreases gradually, along with the appearance of a new band connoting a red shift. The calibration curves are derived from the intensity ratios of A530/A400, which display a linear relation in the range of 1µM-150µM, 5µM-200µM and 10µM-130µM, respectively. The obtained detection limits (3σ) were found to be 1.5µM, 5.6µM and 10.2µM for compound I-III, respectively. The proposed method has been successfully applied for the detection of thiol compounds in real samples.
