Universal Method for Label-Free Detection of Pathogens and Biomolecules by Surface-Enhanced Raman Spectroscopy Based on Gold Nanoparticles.

The detection of biomolecules is the key to basic molecular research, diagnostics, drug screening, and other biomedical applications. However, the existing detection techniques can only detect single classes of biomolecules, which warrant the development of a versatile biomolecule detection platform. Here, we developed a universal method for label-free detection of biomolecules via surface-enhanced Raman spectroscopy (SERS) by using sulfhydryl-modified gold nanoparticles as the substrate. The biomolecules can be adsorbed on the surface of gold nanoparticles cleaned by bromide ions to obtain initially enhanced Raman signals, and the aggregator (calcium ion) was further added to form a "hot spot", which enhanced the biomolecular signal again. Through the "two-step enhancement method", we were able to obtain fingerprints of DNA, RNA, amino acids, peptides, proteins, viruses, bacteria, and lipid molecules. This low-toxic, highly sensitive, and widely applicable technique has potential applications in biomedical research, clinical testing, and disease diagnosis and lays the foundation for the development of SERS technology in various fields.

Rapid Detection of SARS-CoV-2 Spike RBD Protein in Body Fluid: Based on Special Calcium Ion-Mediated Gold Nanoparticles Modified by Bromide Ions.

The receptor-binding domain of the SARS-CoV-2 spike mediates the key to binding the virus to the host receptor, but capturing the molecular signal of this spike RBD remains a formidable challenge. Here, we report a new surface-enhanced Raman spectroscopy (SERS) approach, which used gold nanoparticles prepared by low-speed constant-temperature centrifugation by bromine and calcium ions in two cleaning steps as the enhanced substrate to rapidly and accurately detect spike RBD large protein molecules in body fluids. The detection signal was extremely stable, and the orientation of the spike RBD on the enhanced substrate surface was also determined. This approach was specific in distinguishing different SARS-CoV-2 variants of spike RBD, including Delta, Beta, Gamma, and Omicron. Additionally, the enhanced substrate can identify biologically active or inactive spike RBD. This two-step cleaning enhanced substrate opens up opportunities not only for early diagnostics of SARS-CoV-2 virus but also for developing targeted drugs against viruses.

Label-Free Detection of DNA Supramolecular Structure Formation by Surface-Enhanced Raman Spectroscopy.

The precise self-assembly of DNA molecules can be used to create nanoprecision supramolecular materials. However, the lack of methods to characterize such supramolecular materials limits their development. Surface-enhanced Raman spectroscopy (SERS) is widely used to detect the secondary structure of simple DNA molecules, but its application in the revealing of complex DNA supramolecular information remains challenging. Herein, we proposed a modified SERS-based platform able to provide structural information on DNA supramolecular materials. The silver nanoparticle-enhanced substrate uses acetonitrile as an internal standard and modifier, and calcium ions are used as an aggregating agent to induce the formation of stable "hotspots" of silver nanoparticles, where the base planes in DNA supramolecules are perpendicular to the surface of the substrate, obtaining enhanced Raman signals of base ring in both single-stranded DNA and DNA supramolecules for the first time. The structure of DNA supramolecules was efficiently characterized using this technique, showing the great application potential of this technique in the structural analysis of nucleic acids and their ligands.