Attachment of Single-Stranded DNA to Certain SERS-Active Gold and Silver Substrates: Selected Practical Tips

Abstract

Layers formed from single-stranded DNA on nanostructured plasmonic metals can be applied as “working elements” in surface–enhanced Raman scattering (SERS) sensors used to sensitively and accurately identify specific DNA fragments in various biological samples (for example, in samples of blood). Therefore, the proper formation of the desired DNA layers on SERS substrates is of great practical importance, and many research groups are working to improve the process in forming such structures. In this work, we propose two modifications of a standard method used for depositing DNA with an attached linking thiol moiety on certain SERS-active structures; the modifications yield DNA layers that generate a stronger SERS signal. We propose: (i) freezing the sample when forming DNA layers on the nanoparticles, and (ii) when forming DNA layers on SERS-active macroscopic silver substrates, using ω-substituted alkanethiols with very short alkane chains (such as cysteamine or mercaptopropionic acid) to backfill the empty spaces on the metal surface unoccupied by DNA. When 6-mercapto-1-hexanol is used to fill the unoccupied places on a silver surface (as in experiments on standard gold substrates), a quick detachment of chemisorbed DNA from the silver surface is observed. Whereas, using ω-substituted alkanethiols with a shorter alkane chain makes it possible to easily form mixed DNA/backfilling thiol monolayers. Probably, the significantly lower desorption rate of the thiolated DNA induced by alkanethiols with shorter chains is due to the lower stabilization energy in monolayers formed from such compounds.

Molecular beacon decorated silver nanowires for quantitative miRNA detection by a SERS approach

“…We obtained a LOD of 3 × 10 −16 M for the surface with only a MB, while a higher LOD value, 2.4 × 10 −15 M, was obtained with the mixed MB–MCH layer. These differences, related to the functionalization of the SERS substrate, were partially explained by considering a combination of factors influencing the immobilized MB and the relative SERS signal; as discussed above, the presence of MCH can increase the distance between ROX and the SERS surface and, as reported elsewhere, 66 MCH, commonly optimal for surface passivation on gold, may be not equally useful in the case of the Ag-based surfaces such as the proposed AgNW SERS substrate. However, the treatment with MCH could also lead to a more homogeneous MB coating by removing from the SERS substrate those MBs which are only unspecifically adsorbed or by lifting up the part of the MB adsorbed (Fig.…”

Editors’ Choice—Challenges and Opportunities for Developing Electrochemical Biosensors with Commercialization Potential in the Point-of-Care Diagnostics Market

“…188 Functionalization of electrodes with nucleic acids has been demonstrated using chemical methods employing thiol, carbodiimide, phosphonate coupling, click chemistry, and biotin-streptavidin chemistry, as well as physical methods including physical adsorption, physical entrapment, and electrostatic interactions as reviewed elsewhere. 188,[191][192][193][194][195][196][197][198] Molecularly imprinted polymers.-MIPs are synthetic polymer analogues of antibodies that are designed to bind specific antigens or a group of related targets. MIPs are manufactured by polymerizing monomers in the presence of a target or a template, followed by template removal, leaving cavities for target binding.…”