Biosensors are devices which use a biological recognition element retained in direct spatial contact with transduction system (IUPAC definition) (1)
. Biosensors can be straightforwardly depicted as devices that convert a physical or biological event into a measurable signal (2)
; they are composed of a biosensing element (i.e. enzyme, tissue, living cell) that provides selectivity and a transducer that converts the chemical responses into a 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.