Raman spectroscopy for detecting neurological disorders: Progress and prospects

Raman spectroscopy (RS) is recognized as a highly sensitive and label-free technique capable of providing biochemical information about cells, tissues, and body fluids. The application of RS in neuroscience to investigate human saliva, serum, and blood components for disease diagnosis has been intensively studied, and it has recently acquired significant clinical interest, particularly when combined with artificial intelligence and machine learning algorithms. This chapter provides an in-depth exploration of RS and its variant techniques, encompassing Raman tweezers, surface-enhanced Raman scattering (SERS), coherent anti- Stokes Raman scattering (CARS), and resonance Raman spectroscopy (RRS), which holds a crucial and noteworthy role in the advancement of neuroscience research. The weak Raman signals obtained from clinical samples such as saliva and serum via conventional Raman spectroscopy are low enough for diagnostic purposes. In the SERS approach, the targeted analytes that have been adsorbed on metal colloidal nanoparticles or nanosubtrates experience substantially higher Raman scattering efficiency, ultimately resulting in the development of a noninvasive diagnostic pathway for detecting various neurological disorders (ND). Recent advancements in nanotechnology and cost-effective fabrication routes for generating nanostructures with tailor-made morphologies have contributed significantly to developing a wide variety of SERS nanosubstrates for sensing purposes. Raman tweezers represent a powerful integration of Raman spectroscopy and optical tweezers techniques. It enables the noncontact optical trapping of micron-sized particles suspended in physiological media, allowing the acquisition of Raman spectra at the level of individual cells. This innovative approach holds promise in the field of ND diagnosis and research. This chapter discusses the advancements in the exploration of different RS techniques for the identification and prediction of diseases from body fluids and tissues with a focus on neurological disorders. In addition, the potential utilization of Raman spectroscopy in neurosurgery is also discussed. This chapter concludes with the existing challenges to exploit this technology from bench to bedside as well as its possible future applications as a viable clinical diagnostic method for neurological illnesses.