Biosensors are devices that use a biological recognition element kept in direct contact with a transducer (IUPAC definition) (1)
. Biosensors can be directly represented as devices that convert a physical or biological event into a measurable signal (2)
; they are composed of a biological sensing element (an enzyme, a tissue, living cells, etc.) that provides selectivity, and a transducer that converts physico-chemical variations into processable signals (3)
. Specifically, biosensor consists of three parts: the first element is the biomediator (a biomimic or biologically derived material e.g. tissue, microorganisms, organelles, cell receptors, enzymes
, nucleic acids
, and biological sensitive elements created with genetic engineering
), the second element is the transducer (physicochemical, optical, piezoelectric, electrochemical, etc.) that transforms the signal resulting from the analyte’s interaction with the biological element into a signal that can be measured and quantified; the third element is the associated electronics or signal processor, responsible for a user-friendly way of the results visualization (4)
.Some biosensors require a process of biomediator immobilization to the sensor surface (metal, polymer or glass and other materials) using physical or chemical techniques.