Chapter 10 - Noninvasive biomarker sensors using surface-enhanced Raman spectroscopy

Abstract

Biological fluids contain a wide spectrum of biomarkers that reflect hydration state, mental stress, nutrition, and other physiological changes and therefore can provide rich information about human health conditions. Several types of wearable sensors have recently attracted research interest due to their enormous potential for a wide range of applications. However, progress in the field of on-body sensing has been hampered due to the lack of reliable noninvasive chemical sensors. Biosensors that noninvasively analyze body fluids such as saliva, sweat, and tears are of greater importance these days because of their ability to assess health status by continuously monitoring the changes in metabolic processes. For the development of such noninvasive biosensors, ease of sample collection, presence of biomarkers, types of metabolites and electrolytes in body fluids, device fabrication and integration, etc., have to be seriously considered. In this scenario surface-enhanced Raman spectroscopy (SERS) is a label-free technique for monitoring biomarkers in biological matrices at trace-level concentrations. Compared to other conventional techniques, SERS-based biosensors have many advantages such as high sensitivity, lower detection limits, low cost, simple design, ease of sample collection, and low consumption of costly and/or toxic reagents. In this chapter we review the recent advances in the field of SERS-based sensors for biomarker detection in body fluids such as sweat, saliva, and tears with an emphasis on the analysis of biomarkers, fabrication techniques, and potential real-time applications for biochemical sensing.