Label-free fluorescence DNA walker for protein analysis based on terminal protection and dual enzyme assisted cleavage induced G-quadruplex/berberine conformation
The development of simple, fast, cost-efficient and sensitive approach of accurate protein analysis is of very significance for its potential application in disease diagnosis and biomedicine research. Thus, we established a label-free fluorescence DNA walker for streptavidin detection based on terminal protection and dual enzyme assisted cleavage induced G-quadruplex/berberine conformation. In this paper, the swing arm probe and report probe were pre-assembled to gold nanoparticles. With the addition of target, through the high-efficiency affinity between streptavidin and biotin in order to prevent the hydrolysis of exonuclease I, the swing arm probe which contains 8-17 DNAzyme cannot be destroyed and play its role of catalytic cleavage toward report probe, the liberating fragment of report probe which contains a specific sequence (5′-(TTAGGG)4) of G-quadruplex units can combine with berberine and shows an evident fluorescence signal enhancement. With our method, the sensitive and selective method of protein detection achieves with the detection limits toward streptavidin as 20 pM. This developed DNA walker which combines terminal protection and dual enzyme assisted strategy united provides a prospective channel for streptavidin detection, and should also be used for the design of biosensors in order for the extensive application in bio-detection and disease diagnosis.