A label-free fluorometric assay for actin detection based on enzyme-responsive DNA-templated copper nanoparticles.

Herein, we develop a fluorescent strategy for label-free detection of actin by the in situ formation of double-stranded DNA (dsDNA) templated copper nanoparticles (CuNPs) and the digestion capability of deoxyribonuclease I (DNase I). In this design, the introduction of actin can effectively hinder the enzymic digestion owing to the exceptional target-mediated conformational structure between actin and DNase I. Consequently, the remaining adenine-thymine-rich dsDNA can act as an efficient template for fluorescent CuNPs (λex = 340nm, λem = 585nm) with a Mega-Stokes shifting (245nm). This novel fluorescent strategy exhibits several advantages such as low-cost and environmental-friendly, because it does not require the toxic organic dyes and laborious procedures. Under optimized experimental conditions, this method realizes a turn-on selective and sensitive response for actin with a detection limit of 0.12μgmL-1 and a detection capability in complex biological media with satisfactory results.