Increasing surface enhanced Raman spectroscopy effect of RNA and DNA components by changing the pH of silver colloidal suspensions

This work focused on establishing the parameters for enhancing the Raman signals of DNA and RNA constituents: nitrogenous bases, nucleosides and nucleotides, using metallic nanoparticles as surface enhanced Raman scattering substrates. Silver nanospheres were synthesized using sodium borohydride as a reducing agent and sodium citrate as a capping agent. The prepared nanoparticles had a surface plasmon band at ∼384 nm and an average size of 12 ± 3 nm. The nanoparticles’ surface charge was manipulated by changing the pH of the Ag colloidal suspensions in the range of 1–13. Low concentrations as 0.7 μM were detected under the experimental conditions. The optimum pH values were: 7 for adenine, 9 for AMP, 5 for adenosine, 7 for dAMP and 11 for deoxyadenosine.

Graphical abstractParameters for enhancing the Raman signals of DNA and RNA constituents: nitrogenous bases, nucleosides and nucleotides, using metallic nanoparticles as SERS substrates.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Surface charges on Ag NPs were modified from normal values by changing the pH of colloidal sols. ► Modification of surface charges led to more amenable SERS substrates for DNA and RNA constituents. ► This in turn resulted in more intense vibrational signals for these analytes. ► Lower LODs were achieved in these biomolecular systems by tailoring the Ag NPs surface charges.