Simple and facile preparation of silver–polydopamine (Ag–PDA) core–shell nanoparticles for selective electrochemical detection of cysteine

Abstract

Selective and sensitive non-enzymatic electrochemical detection of cysteine (CySH) is achieved in the present work using a polydopamine capped silver nanoparticles (Ag–PDA) modified indium tin oxide (ITO) electrode. Efficient redox properties, synergistic effects and the specific steric hindrance associated with the Ag–PDA core–shell nanoparticles provide higher selectivity and larger sensitivity for CySH detection over other competitive bio-thiols namely, homo-cysteine and glutathione. A simple one-step method is used for the preparation of Ag–PDA core–shell nanoparticles. The structure, morphology and composition of Ag–PDA nanoparticles are characterized by using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-visible (UV-vis) and Fourier transform infra red (FTIR) spectroscopic techniques. Electrochemical characteristics are investigated by using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). These studies clearly reveal the formation of Ag–PDA nanocomposite on the ITO electrodes and their corresponding redox properties. Non-enzymatic electrochemical detection of CySH is carried out using Ag–PDA modified ITO electrodes in 0.1 M PBS (pH = 5.0) aqueous solution. Under the optimized conditions, this particular electrochemical biosensor exhibits a perfect linear calibration plot in the concentration range between 0.05 μM and 300 μM. Further, a sensitivity value of 0.023 μA μM⁻¹ and a lower detection limit of 0.02 μM are determined for CySH detection. Moreover this Ag–PDA modified ITO electrode is applied further for the determination of CySH in human blood serum samples and the results are promising and satisfactory, suggesting the possible analytical application of this biosensor for the determination of CySH in biological samples.