*3.1. Optical Detection*

Optical detection of cells implies the use of optical techniques and instruments for the detection, classification, and stratification of cells [41]. Various types of optical-based biosensors have been developed and utilized for diverse biological and clinical applications, such as surface plasmon resonance (SPR), optical waveguides, optical resonators, and fluorescence [3,58,59]. Optical biosensors have several advantages, including their high sensitivity, real-time detection, label-free analysis, small form factor, and low cost [41]. These characteristics make optical biosensors an appealing option for integration into lab-on-a-chip devices, which seek to carry out sample preparation, research, and detection in a miniaturized and automated format [59]. In the next section, we will review the latest developments of optical-based biosensor devices in the identification and clinical diagnosis of various types of cancers, as well as data analysis with machine learning techniques.
