Facile and sensitive S1 endonuclease activity and inhibition assay using positively-charged Ag nanorods

Abstract In this work, we designed a facile and promising strategy for fluorescence determination of S1 endonuclease activity and inhibition based on fluorescence resonance energy transfer (FRET) between positively Ag nanorods (AgNRs) and negatively-charged ROX-labeled sing-stranded DNA (ROX-ssDNA). In the absence of S1 endonuclease, the fluorescence signal of the ROX-ssDNA was efficiently quenched when the ROX-ssDNA was adsorbed on the surface of AgNRs via strong electrostatic interaction. However, upon addition of different concentration of S1 endonuclease, the fluorescence was gradually restored owing to the reduction of FRET efficiency caused by S1 endonuclease specific cleavage ROX-ssDNA into short fragments, which reduced the electrostatic interaction between AgNRs and short oligonucleotide fragment. This assay strategy exhibited a high sensitivity and excellent specificity for S1 endonuclease with a detection limit of 0.004 U/mL and a dynamic concentration range from 0.01 U/mL to 5.0 U/mL. In addition, the capabilities for screening of S1 endonuclease inhibitors and S1 endonuclease detection from complex biological matrixes were also verified.