Sodium gluconate capped silver nanoparticles as a highly sensitive and selective colorimetric probe for the naked eye sensing of creatinine in human serum and urine

Abstract

A highly selective and fast analytical assay using sodium gluconate -capped Ag nanoparticles (GA@AgNPs) was developed for the determination of creatinine by UV–Vis spectrophotometric detection. By adding creatinine to the GA@AgNPs solution, the extinction intensity of the surface plasmon resonance (SPR) band of the corresponding UV–Vis spectrum of GA@AgNPs at 393 nm reduced and meanwhile a new absorption peak appeared at 560 nm gradually with increasing creatinine concentratin. Induced aggregation of GA@AgNPs by creatinine, accompanied with color changes from yellow to red, can be directly observed by the nacked eye in five minutes. The extinction spectra ratio of A560/A393 was used for the colorimetric determination of creatinine. Effective parameters on the absorption intensity such as the sample pH, the type and buffer concentration, ionic strength and AgNPs concentration were optimized. Under the optimal conditions, a linear relationship between the SPR intensity ratio of A560/A393 values and creatinine concentrations is obtained over the range of 0.3–50 nM with a correlation coefficient of 0.9763 and a limit of detection of 0.2 nM. The relative standard deviation (RSD%) for five measurements of creatinine solution at 1 nM was 4.0%, exhibiting good repeatability. The results indicate that the developed probe can be successfully used for the determination of creatinine in serum and urine samples with satisfactory results.