Optical instrumentation for fluorescent biosensors

Abstract

Biosensors are the analytical devices that sense the analyte through a biological recognition element (enzymes, DNA, nanoparticles) and convert the biological signal into an electrical signal through the transducers. The transducers (photodiodes, pH electrodes, Thermistors, piezo-electrics) typically converts one form of energy (photons, ion concentrations, change in temperature, mass, etc.) into another form (electrical signals). The conversion of signals from one form to another can be accomplished by optical transducers and others (like electrochemical, piezo-electric, etc.). The fluorescent biosensors measure the optical signals generated due to the fluorescence. Here, fluorescence can be defined as a molecular phenomenon in which a substance absorbs light of some wavelength and almost instantly emit light of another color of lower energy and higher wavelength. The optical signal in the form of photons is then detected by the optical instrumentation set-up. An ideal optical set-up should be portable, easy to use, economical, sensitive, capable of real-time analysis and amenable for the point-of-care (POC) applications (Kaushik & Mujawar, 2018). The advancements in the development of POC devices make them suitable for using them for biosensing technologies. The POC devices are expressed as a great candidate for the monitoring of food quality and detection of contaminations in food samples through biosensing technologies. Food safety is now becoming a global concern and needs to be addressed with an optimized solution. The conventional methods (like HPLC, GC and Mass spectroscopy) of detecting food contaminations are time consuming, require pre-sample treatment, skilled operators and are costly in nature (Choi et al., 2019). The efforts from food industries related to food safety bring an essential opportunity to develop POC devices to address such problems associated with the food sector. The POC devices have been used and explored to address the challenges of food safety. For example, paper-based and chip-based POC devices have been used for the detections of food toxins (Liu et al., 2017) and food born pathogen detection (X. Li et al., 2017; Pang et al., 2018). The use of paper based and thin-film-based sensing enables the colorimetric and fluorescence-based detection of food contaminations (i.e. urea) in complex food matrices such as milk. The advancement in health care management is a fundamental key to rendering improved health solutions. The promotions of POC devices for smart bio-sensing helps to develop rapid, cost-effective solutions for real time diagnosis and analysis of chemical parameters or biomarkers with high sensitivity and selectivity in biological samples for better health. POC devices can be used in cheap, disposable point-of-use devices for innovative biosensor technology. The POC devices have been evolved over the past few decades for biosensors technologies to detect the biomarkers in complex biological matrices. The on-site measurements of analytes such as urea and glucose in plasma and urine samples provide the advancement for personalized health care (Vasan et al., 2013).