Gluconate‐Stabilized Silver Nanoparticles as pH Dependent Dual‐Nanosensor for Quantitative Evaluation of Methionine and Cysteine

Abstract

AbstractSilver nanoparticles (AgNPs) based naked‐eye and spectrophotometric dual‐nanosensor for two most important biothiols: methionine and cysteine would be highly useful for an analyst. We have explored potential use of gluconate‐stabilized AgNPs (Glu‐AgNPs) for such unique purpose. Simply, aggregation of Glu‐AgNPs by the analyte, methionine/cysteine technique was adopted. Gluconate ions make the AgNPs anionic in nature. The anionic Glu‐AgNPs, as a pH‐ dependent nanosensor are selective to sensing methionine and cysteine over other amino acids in aqueous solution. By tuning pH of the particles’ solution we have at different demonstrated that the equilibria components of methionine/cysteine at different pH may play guiding roles in aggregating the particles, consequently in selectivity and sensitivity of the nanosensor. The LOL, LOQ, and LOD for methionine are 42, 9.89 and 2.97 μM, and for cysteine are 1.4, 0.49 and 0.14 μM, respectively. The interactions of cysteine (Kasso, 3.07x105 M−1) with the anionic Glu‐AgNPs are greater than that of methionine (Kasso, 1.635x104 M−1). Overall, the recovery results from the real samples: urine, blood serum and aCsF are excellent, which may make the developed nanosensor attractive to an analyst.