Silk Fibroin-Confined Star-Shaped Decahedral Silver Nanoparticles as Fluorescent Probe for Detection of Cu2+ and Pyrophosphate

A green, one-step method for the fabrication of silk fibroin (SF) protected silver decahedral nanoparticles (SF@AgNPs) has been developed. High-resolution transmission electron microscopy characterization demonstrated that the silver decahedral nanoparticles can provide more binding sites with (111) facets. Moreover, a facile strategy based on Cu2+ mediated SF@AgNPs was reported as an on-off-on fluorescent system for the detection of Cu2+, and the SF@AgNPs can be also used for the determination of pyrophosphate ion (P2O74-, PPi). The fluorescence of SF@AgNPs was quenched by Cu2+ as a complex formed between SF and Cu2+ and was restored when PPi was introduced into the system due to the higher binding affinity between PPi and Cu2+. Herein, a novel SF@AgNPs-Cu2+ fluorescent probe for Cu2+ and PPi detection is presented. The proposed assay shows a linear relationship at a Cu2+ concentration range from 1 to 6 mu M with a detection limit of 33.3 nM. This simple, reliable, selective, and environmentally friendly fluorescent probe also has a wide concentration range from 100 to 700 mu M with a detection limit of 6.7 mu M for PPi. The 16 types of anions lead to negligible changes in the SF@AgNPs-Cu2+ complexes, while restoring the fluorescence intensity of the complexes when added with PPi. Additionally, it is demonstrated that the SF@AgNPs-based fluorescent assay works in real biological samples. It suggests that this proposed method has the potential for application in the clinical detection of Cu2+ and PPi.