Label-free optical biosensors for food and biological sensor applications

Safety of food is a scientific domain requiring advanced handling, preparation, and storage. Food is a paramount need for growth of microorganisms it serves as a medium for proliferation and contamination. The primary historical techniques for food analysis are time-consuming and laborious whereas biosensors have an easier control over these limitations. Biosensor technology is a powerful tool for food analysis. Optical sensors reveal higher calibre for analysis of drugs, pesticide residues, pathogens, heavy metals, toxic substances as well as for overall hygiene monitoring in the food system. Label-free operations altogether acquired a well-established need for the characterization and identification of molecular components. We review the recent advances in label-free optical biosensors based on the target analytes. This study focuses on the concise classification, underlying principles on the optical transducer, optical (surface) analytical techniques as a part of biosensing and use of nanostructures in optical sensors. The main highlights include characterisation of localized surface plasmon and surface plasmon resonance based biosensors. Additionally, other optical biosensors such as bioluminescent optical fibre biosensors, evanescent wave fluorescence, ellipsometric, surface-enhanced Raman scattering and light-addressable potentiometric sensors are also well explained and characterized for food and environmental applications.