A versatile technique for indiscriminate detection of unlabeled biomolecules via double-enhanced Raman scattering

Surface-enhanced Raman scattering is a rapid, highly sensitive and non-destructive technique, whereas, it was still limited to designing different types of enhancing substrates or using probe molecules to only identify single biomolecules. Especially, some special biomolecules have weak Raman signals in solid state, so it is a huge challenge to obtain their enhanced Raman signals in liquid. To solve the problem, a double-enhanced Raman scattering (DERS) detection platform was developed in this study based on silver nanoparticles that were prepared by using an appropriate amount of sodium borohydride and guided by calcium ions to form good "hot spots". This enabled one to successfully obtain fingerprints of various types of biomolecules under the identical experimental conditions. The addition of sodium borohydride as reducing agent could protect silver nanoparticles from oxidation, and biomolecules were adsorbed on the exposed silver surface and demonstrated their initially enhanced Raman signals. Furthermore, the "hot spots" formed by silver nanoparticles without silver oxide coating could further enhance the Raman signal of biomolecules, making the enhancement factor up to 10 [8]. To sum up, the possibility of fast identification of different species of biomolecules via DERS has wide application prospects in the fields of biomarker detection and medical diagnosis.