Nucleic acid-mediated SERS Biosensors: Signal enhancement strategies and applications

Surface Enhanced Raman Spectroscopy (SERS) is a powerful spectroscopic analysis technique applied in various fields due to its high selectivity, ultra-high sensitivity, and non-destructiveness. As natural biological macromolecules, nucleic acids perform a significant role in SERS biosensing. In this review, we first summarize how nucleic acids mediate the signal enhancement of SERS biosensors from three aspects: substrate self-assembly, analyte biorecognition, and molecular amplification. Among them, SERS substrates can be self-assembled by both DNA modification and coordination or electrostatic interactions. In the field of biorecognition, analyte biorecognition based on three nucleic acid recognition elements can enhance SERS signals by regulating the distance of analytes or Raman reporter molecules to the SERS substrate. In addition, nucleic acid-based enzyme and enzyme-free amplification can enhance SERS signals by enlarging the quantity of analytes or its nucleic acid intermediates. Subsequently, multidimensional applications of nucleic acid-mediated SERS signal enhancement in biomedicine, food safety, and environmental monitoring are listed. Finally, the current challenges and future exploration of nucleic acid-mediated SERS signal enhancement are discussed.

Prospects in interfaces of biomolecule DNA and nanomaterials as an effective way for improvising surface enhanced Raman scattering: A review

Surface Enhanced Raman Scattering (SERS) is a field of research that has shown promising application in the analysis of various substrate molecules by means of rough metallic surfaces. In directing the enhancement of substrate molecules in micro and nano-molar concentrations, plasmonic coupling of metal nanoparticles (NPs), morphology of metal NPs and the closely arrangement of rough metal surfaces that produces 'hot spots' can effectively increase the so-called enhancement factor (EF) that will be applicable in various fields. As the mechanistic aspects are still not clear, research has been triggered all over the world for the past two decades to have a clear understanding in chemical and electromagnetic effects. As the reproducibility of intensity of signals at low concentrations of probe molecules is of a big concern, metal NPs with various scaffolds were prepared and recently bio-molecule, DNA has been studied and showed promising advantages. This review first time highlights metal NPs with DNA interface as an effective rough metallic surface for SERS with high intensity and also with better reproducibility. Based on this review, similar kinds of scaffolds like DNA can be used to further analyze SERS activities of various metal NPs with different morphologies to have high intense signals at low concentrations of probe molecules.

Fe(III) Mixed IP6@Au NPs with Enhanced SERS Activity for Detection of 4-ATP

Surface Enhanced Raman Scattering (SERS) has been widely applied in many research fields such as biological detection and chemical analysis. However, for the common Au nanoparticles, it's too hard to guarante the three aspects: the great enhanced effect, the controllable aggregation and the uniformity of nanoparticles, the environmental friendliness and biocompatibility of nanoparticles. In this paper, phytate acid (IP6)-coated Au nanoparticles (IP6@Au NPs) are more stable and have a higher enhancement factor than Au nanoparticles. In order to achieve the uniformity of the spherical IP6-coated@Au nanoparticles (IP6@Au NPs), IP6 was used as a soft template. In the presence of IP6, IP6@Ag nanoparticles were first synthesized by reducing AgNO₃ with trisodium citrate, then IP6@Au NPs were obtained by reducing HAuCl₄ with Ag nanoparticles. The IP6@Au NPs exhibit excellent Raman signal enhancement by using p-aminothiophenol (4-ATP) as the probe molecules. The effects of Fe³⁺ on the performance of IP6@Au NPs SERS substrates were also studied. The results show that SERS has the best enhancement effect when adding proper amount of Fe³⁺ (0.56 PPM), and the limit of detection was 10^-7 M 4-ATP.

Green in Situ Synthesis of Clean 3D Chestnutlike Ag/WO3-x Nanostructures for Highly Efficient, Recyclable and Sensitive SERS Sensing

Surface-enhanced Raman scattering (SERS) has proven to be an effective technique for identifying and providing fingerprint structural information on various analytes in low concentration. However, this analytical technique has been plagued by the ubiquitous presence of organic contaminants on roughened SERS substrate surfaces, which not only often result in poorer detection sensitivity but also significantly affect the reproducibility and accuracy of SERS analysis. Herein, we developed a clean, stable, and recyclable three-dimensional (3D) chestnutlike Ag/WO_3-x (0 < x < 0.28) SERS substrate by simple hydrothermal reaction and subsequent green in situ decoration of silver nanoparticles. None of the organic additives were used in synthesis, which ensures the substrate surfaces are completely clean and free of interferences from impurities. The innovative design combines the SERS enhancement effect and self-cleaning property, making it a multifunctional and reusable SERS platform for highly sensitive SERS detection. Using malachite green as a model target, the as-prepared SERS substrates exhibited good reproducibility (relative standard deviation of 7.5%) and pushed the detection limit down to 0.29 pM. The enhancement factor was found to be as high as 1.4 × 10⁷ based on the analysis of 4-aminothiophenol. The excellent regeneration performance indicated that the 3D biomimetic SERS substrates can be reused many times. In addition, the fabricated substrate was successfully employed for detecting thiram in water with a detection limit of 0.32 nM, and a good linear relationship was obtained between the logarithmic intensities and the logarithmic concentrations of thiram ranging from 1 nM to 1 μM. More importantly, the resultant SERS-active colloid can be used for accurate and reliable determination of thiram in real fruit peels. These results predict that the proposed SERS system have great potential toward rapid, reliable, and on-site analysis, especially for food safety and environmental supervision.

ZnO oxide films for ultrasensitive, rapid, and label-free detection of neopterin by surface-enhanced Raman spectroscopy

Efficient and low-cost surface-enhanced Raman scattering (SERS) substrates based on Au coated zinc oxide layers for the detection of neopterin were prepared.

Design and fabrication of surface-enhanced Raman scattering substrate from DNA–gold nanoparticles assembly with 2–3 nm interparticle gap

This study provides a one-step strategy for preparing DNA–Au hybrids as SERS-active substrates by the simple mixing of DNA and Au colloids.