Diagnosis is the key component in disease elimination to improve global health. However, there is a tremendous need for diagnostic innovation for neglected tropical diseases that largely consist of mosquito-borne infections and bacterial infections. Early diagnosis of these infectious diseases is critical but challenging because the biomarkers are present at low concentrations, demanding bioanalytical techniques that can deliver high sensitivity with ensured specificity. Owing to the plasmonic nanomaterials-enabled high detection sensitivities, even up to single molecules, surface-enhanced Raman spectroscopy (SERS) has gained attention as an optical analytical tool for early disease biomarker detection. In this mini-review, we highlight the SERS-based assay development tailored to detect key types of biomarkers for mosquito-borne and bacterial infections. We discuss in detail the variations of SERS-based techniques that have developed to afford qualitative and quantitative disease biomarker detection in a more accurate, affordable, and field-transferable manner. Current and emerging challenges in the advancement of SERS-based technologies from the proof-of-concept phase to the point-of-care phase are also briefly discussed.

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The Raman scattering tensor for each gerade vibrational mode of crystalline naphthalene is evaluated from polarized Raman spectra of oriented single crystals. For molecular crystals, where the intermolecular interactions are weak, the form of the tensors is determined by the properties and symmetry of the molecule rather than the crystal; consequently, the symmetries of the gerade vibrations are readily identified. A comparison of these data with the phosphorescence and fluorescence spectra allows the fundamental vibrational frequencies to be assigned empirically. Except for one b2g mode and one b3g mode, the empirical assignments support those in the literature made on the basis of force field calculations. It is found that crystal effects on the gerade vibrations are small: frequency shifts are 2–4 cm−1, exciton splittings are less than 1 cm−1, and intensities are described qualitatively by the oriented gas model, although an unambiguous example of crystal-induced Fermi resonance is evident. Disagreement between the observed exciton splittings and some calculated splittings by N. Rich and D. Dows [Mol. Cryst. Liquid Cryst. 5, 111 (1968)] based on an atom–atom potential model may indicate that some finer features of the intermolecular potential are not well represented by such a model. The temperature dependence of the Raman linewidth and line shape is documented.

Data are presented for the Raman spectrum of benzene and perdeutero-benzene at 77° and 2°K, with a resolution of 0.65 cm−1. Splittings are detected for all Raman-active degenerate vibrations but for none of the nondegenerate vibrations, with the possible exception of ν5(b2g) in C6H6. Interaction matrix elements are found for three degenerate bands where splittings seem to be uncontaminated by site-group splitting. Comparison is made between the present data and the recent calculations of Harada and Shimanouchi. Extension of the calculation to include intermolecular carbon—hydrogen interactions is indicated by the data.

Point-of-care systems require highly sensitive, quantitative and selective detection platforms for the real-time multiplexed monitoring of target analytes. To ensure facile development of a sensor, it is preferable for the detection assay to have minimal chemical complexity, contain no wash steps and provide a wide and easily adaptable detection range for multiple targets. Current studies involve label-free detection strategy for relevant clinical molecules such as heme using G-quadruplex based self-assembly. We have explored the measurement of binding and kinetic parameters of various G-quadruplex/heme complexes which are able to self-associate to form a DNAzyme with peroxidase mimicking capabilities and are critical to nucleic acid research. The detection strategy includes immobilizing the G-quadruplex sequences within a polymer matrix to provide a self-assembly based detection approach for heme that could be translated towards other clinically relevant targets.