The monitoring of thiocyanate (SCN−) in food is of consumer health and safety relevance. In this work, a colorimetric method for the detection of SCN− in milk using a silver nanoparticles (AgNPs) nanozyme is presented. Here, silver nanoparticles were synthesized using the leaf extracts of Sclerocarya birrea (marula). The nanoparticles exhibited intrinsic oxidase mimetic catalytic activity. They could efficiently catalyze the colorimetric oxidation of 3,3′,5,5′- tetramethylbenzidine (TMB) in the presence of oxygen to form a blue colored cation radical with a characteristic absorption peak at 654 nm. We found out that adding thiocyanate (SCN−) strongly inhibited this colorimetric reaction by decreasing the oxidase-like activity of the AgNPs selectively. The inhibition and color variation of the assay was proportional to the concentration of SCN−. Based on these findings a colorimetric assay for the detection of SCN− was established. The assay exhibited excellent selectivity against potential interferents and sensitivity with a low detection limit of 2.89 μM. This novel application showed high accuracy with excellent recoveries of between 89.4 and 118.1 %, along with fast detection times of 3 min employing low sample volumes. These excellent characteristics of the developed assay present it as a potential simple, fast, sensitive, selective, visual, equipment free point-of-need diagnostic tool of high throughput for food safety diagnosis.
Citation: Semong O, Batlokwa BS. 2022. Morula Leaf Extract Mediated Synthesis of Silver Nanoparticles and their Application in the Analysis of SCN− Based on Inhibition of the Nanozyme Activity on 3,3’,5,5’-Tetramethylbenzidine (TMB) by the Silver Nanoparticles. J Food Chem Nanotechnol 8(4): 192-200.