Label-free colorimetric detection of serum cysteine using Ag-NP probes in the presence of Be2+ ions

The synthesis of Pt doped WO3 nanosheets and application on colorimetric detection of cysteine by naked eye using response surface methodology for optimization

We present a simple, sensitive, and specific colorimetric using the peroxidase properties method based on Pt doped WO₃ nanosheets to detect the cysteine. Pt@WO₃NSs were synthesized by hydrothermal method and characterized by Fourier transform infrared (FTIR), Transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction patterns (XRD) methods. The response surface methodology (RSM) method based on the central composite design (CCD) was used to optimize test parameters such as pH, nanosheet concentration, and temperature. When cysteine is present in the environment due to its competition with 3,3', 5,5'-Tetramethylbenzidine (TMB) in the use of hydrogen peroxide, the blue discoloration is reduced compared to the absence of cysteine and leads to its detection. We have favorably created a peculiar approach for sensing cysteine based on the colorimetric method in solution and paper with linear range 0.01-15 μM, 0.005-14 μM and R² = 0.9887 and R² = 0.9871 respectively. The detection limit for solution-based is 1.2 nM and for paper-based is 1 nM.

Tailoring cysteine detection in colorimetric techniques using Co/Fe-functionalized mesoporous silica nanoparticles

Over the past decade, there has been a dramatic increase in the number of studies focused on sensors for cysteine (Cys) as a crucial factor in physiological function and disease diagnosis. Among those sensors, nanomaterial-based peroxidase mimetics have received particular attention from researchers. This study introduces a new series of mesoporous silica nanoparticles (MSNs) incorporated with iron and cobalt (Co/Fe-MSN) with a molar ratio of Si/Fe = 10 and cobalt species at 1, 3, and 5 wt% that have great potential in the sensing application. These nanomaterial characterization was investigated by FTIR spectroscopy, SEM, TEM, XRD, and nitrogen adsorption-desorption. The peroxidase activity of these nanomaterials was studied through kinetic analysis. The findings revealed that Co/Fe-MSN (1%) showed higher peroxidatic activity than the others towards the common chromogenic substrate 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) diammonium salt. Based on the enzymatic activity of Co/Fe-MSN (1%), a colorimetric sensing platform was designed to detect H2O2 and Cys. The limit of detection (LOD) for H2O2 and Cys was determined to be 1.1 μM and 0.89 nM, respectively. The results indicated that the proposed enzyme mimic exhibited excellent potential as a sensor in medical diagnostics and biological systems.