科研之友
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摘要
A novel ratiometric surface-enhanced Raman scattering (SERS) nanosensor has been developed to probe the activity of endonuclease under in vitro and in living cells conditions. The optimized alloyed Au/Ag nanoparticles (Au/AgNPs) were synthesized as the SERS substrate, which combined the superior properties of both the pure Au and Ag nanoparticles: they exhibit excellent plasmonic property with high chemical stability and low cytotoxicity. They were then employed for quantitative detection of endonuclease through functionalization with single-stranded DNA (ssDNA) carrying 3-(4-(phenylethynyl)benzylthio) propanoic acid (PEB) as endonuclease-responsive SERS signaling molecule, and 4-thiol phenylacetylene (TPA) as the internal standard SERS signaling molecule. In the presence of endonuclease, the ssDNA was cleaved, releasing the PEB molecules from the particle surface and decreasing the SERS signal at 2215 cm-1 from PEB. Since the SERS signal at 1983 cm-1 from alkynyl TPA remained the same, quantitative detection of endonuclease was achieved based on the ratiometric peak intensity of I1983/I2215, with a detection limit as low as 0.056 U/mL. A highly biocompatible and anti-jamming ratiometric SERS sensor was established by combining the alloyed Au/AgNPs with two unique alkynes molecules with Raman signal in the cellular silent region. The ratiometric sensor was successfully employed to detect intracellular endonuclease activity as well as endonuclease in living cells for the first time.
