A Molecular Beacon-Based Signal-Off Surface-Enhanced Raman Scattering Strategy for Highly Sensitive, Reproducible, and Multiplexed DNA Detection

摘要

Surface-enhanced Raman scattering (SERS) spectroscopy has been recognized as a powerful analytical tool due to its several merits, including: 1) ideally amplifying Raman signals by factors up to ≈ 10~(10–14), which offers opportunities to detect targets at the single-molecule level and provides spectral fingerprinting information of molecules; 2) featuring narrow Raman bands that lead to a multiplexed detection capability with a single laser excitation; 3) facile manipulation free of complicated sample preparation; and 4) being insensitive to humidity, oxygen, and foreign species. ~([1–6]) Therefore, SERS has been widely employed for the detection of various biological and chemical species (e.g., DNA, proteins, viruses, TNT, heavy metallic ions). ~([7–12]) In principle, most existing SERS strategies are generally based on detection of signal amplification, that is, SERS intensities are amplified significantly in the presence of targets (the so-called “signal-on” procedure). Taking DNA detection as an example, the SERS substrate is first assembled with rigid linear capture DNA, followed by hybridization with target DNA tagged with Raman labels (e.g., organic dyes), thereby producing enhanced SERS signals for DNA detection (in some cases, reporter DNA is also utilized to construct a sandwiched DNA structure). For instance, Kim et al. reported an Au particle on-wire system employing probe, target, and reporter DNA as a specific, sensitive, and multiplex DNA sensor. The particle-on-wire sensor provided amplified SERS signals in the presence of target DNA in proportion to the DNA concentration spanning from 10 p m to 10 n m. ~([13]) Nie and co-workers introduced a class of gold nanoparticle (AuNP)-based SERS probes with unique mechanisms for molecular recognition. Typically, distinct signal enhancement could be observed by biomolecular binding and dissociation events by using spectrally encoded and bioconjugated AuNPs. ~([14]) Our group designed a sandwiched DNA structure, in which organic dyes became close to SERS substrates when target DNA was hybridized with reporter DNA, thus producing significantly high SERS signals for detection of DNA with a notably low concentration (≈ 10 f m). ~([15]) Recently, by using a similar signal-on strategy, we further developed AuNP-decorated graphene as a novel SERS substrate for sensitive DNA detection. ~([16]) Notwithstanding, these advances remain short of increasing demand for sensing applications, and efforts are thus still required to develop novel SERS strategies with high sensitivity, specificity, reproducibility, and multiplexed detection capability.