Figure 2: Schematic representation of working of biosensor
Bioreceptors are the biocatalytic molecule including enzymes, cells, antibodies, nucleic acids, and microbes that recognizes the analyte. According to the bioreceptors component, biosensors will be classified into DNA biosensors, enzymatic biosensors, non-enzymatic biosensors and immunosensors, and whole-cell biosensors. Enzymatic biosensors are the one which combines enzyme with transducer. The specific immobilized enzyme identifies a specific substrate and produces a signal, the substrate can be identified by any of the transducers (optical, electrochemical, thermal and Piezoelectric) and converted into electric signal. The non-enzymatic biosensor has metal like platinum integrated with a transducer. Non-enzymatic sensors are without biological functional units and can be beneficial in terms of structural simplicity and mass production (Mehrotra, 2016).
Immunosensors are selective, specific, and flexible biosensors that recognize a stable compound of particular antigens or antibodies. DNA biosensors are categorized by spontaneous hydrogen bonding of the target DNA with its complementary strand based on the detection of nucleic acid sequences from infectious microbes and tiny contaminants (Asal et al., 2018).
Whole-cell biosensors are those that use living organisms as the recognition component, such as bacteria, yeast, fungus, plant and animal cells, or even tissue slices, by monitoring the initial inputs into a biological response. Whole-cell biosensors have an advantage of providing sensitive, selective, real-time, rapid and unique data as compared to conventional chemical-based biosensors. A marine algaeSpirulina subsala has an application in detecting metals and pesticides (Tonnina et al., 2002). As biosensors are cost-effective and sensitive, their applications have increased rapidly in environment, medical and industrial applications (Anand Raj et al., 2020).