M13 Bacteriophage-Gold Nanoparticle SERS Sensor for Metabolomics-Based Disease Diagnosis

One of the main goals of metabolomics is to obtain information about diseases or disorders in organisms through changes in the composition of metabolites generated from the activities of genes, proteins, etc. Mass spectrometry (MS) and nuclear magnetic resonance (NMR) are the most commonly used analytical methods in metabolomics. However, MS is sensitive but requires additional techniques for sample preparation, and the basic sensitivity of NMR is low, at the level of several mM.
Surface-enhanced Raman scattering (SERS) is an analytical method that does not require pretreatment and has high sensitivity. SERS is gaining attention as an alternative analytical method in metabolomics because it can provide information about the molecular vibration of metabolites and small molecule analytes. The electromagnetic field enhancement that occurs through the localized surface plasmon resonance between two or more metal nanoparticles with a dielectric between them generates a 10⁶~10⁸-fold increase in the Raman signal. However, since the region where the electromagnetic field enhancement occurs is very small (within 20–30 nm), the probability that the sample will enter that region is low, and the probability that a molecule of a large size (50–70 nm) will enter that region is very low. In addition, the polymer layer of metal nanoparticles is necessary to keep stable dispersion and maintain nanogap.
In this study, M13 bacteriophage, a functional polymer, was used as a dielectric layer for generating localized surface plasmon resonance (LSPR). M13 bacteriophage, which is genetically engineered to be 4E type by genetic engineering, has a negative charge on its surface and easily attaches to the surface of gold nanoparticles. M13 bacteriophage attached to the surface of gold nanoparticles also acts as a protective film to prevent particle aggregation, thereby securing nano gaps between gold nanoparticles. M13 bacteriophage and target material are mixed with gold nanoparticles in a solution state. The mixed solution is coated on the substrate surface by meniscus dragging deposition (MDD), and a film in which gold nanoparticles, M13 bacteriophage, and target material are evenly mixed is generated. In this structure, the probability that the target substance is located in the hotspot is higher than that of the conventional SERS substrate, and the three-dimensional nanocluster structure enables detection of larger molecules. This result suggests the possibility of performing disease diagnosis based on metabolomics more easily and can be further applied to the actual medical field to help determine the disease.