Fabrication of test strips with gold-silver nanospheres and metal–organic frameworks: A fluorimetric method for sensing trace cysteine in hela cells

Abstract

A fluorimetric test strips-based strategy has been initially developed for probing trace cysteine (Cys) in hela cells using gold-silver (Au-Ag) nanospheres and metal-organic frameworks of ZIF-8. Bimetallic Au-Ag nanoclusters were first synthesized by the protein-templated biominerization and then harvested by a desolvation route to form Au-Ag nanospheres showing strong fluorescence that could be specifically quenched by Cys. The as-prepared nanospheres were coated onto test strips to be further shelled with ZIF-8 by using a vacuum-aided fast drying route with super-hydrophobic patterns. It was discovered that the so fabricated test strips could not only achieve uniform coatings of fluorescent nano-probes, but also the ZIF-8 shell-enabled improvement of fluorescence, environmental and storage stabilities. In addition to the evaluation of Cys in serum samples, the developed fluorimetric test strips can facilitate the direct detection of Cys in hela cells with the linear concentrations ranging from 0.0032 to 32.0 μM, thus promising for the point-of-care monitoring of low-level Cys for the clinical early diagnosis of some diseases like cancers. Besides, such a proposed protocol forthe fabrication of stable and uniform test strips using MOFs coatings and super-hydrophobic patterns may be tailored for designing various solid-state testing platforms for the extensive analysis applications.