A biosensor is a measuring device that includes a probe, a physics-chemistry detector element, and a transducer, as well as a sensitive biological detecting substance or a biological receptor. Biosensor research and development is becoming the most widely studied discipline because biosensors are simple, quick, low-cost, highly sensitive, and highly selective, and they help advance next-generation medicines like individualised medicine and ultrasensitive point-of-care detection of disease markers. Biosensors are increasingly widely used in biomedical diagnostics, as well as a variety of other applications such as point-of-care treatment and illness progression monitoring, environmental monitoring, food safety, drug discovery, forensics, and biomedical research. Biosensors can be developed using a wide variety of ways. Their combination with high-affinity biomolecules allows them to detect a wide range of analytes in a sensitive and selective manner. The rapid advancement of biosensors in recent decades, both in terms of research and product development, is largely due to: (i) advances in miniaturisation and microfabrication technologies; (ii) the use of novel bio-recognition molecules; (iii) novel nanomaterials and nanostructured devices; and (iv) improved interaction between life scientists and engineering/physical scientists.