**4.2 Selectivity**

Selectivity is arguably the most significant element of a biosensor. The bioreceptor's capability to identify a particular analyte in a sample that contains different contaminants and admixtures is referred to as selectivity. The selectivity in the example is the relationship between an antibody and an antigen. Traditionally, antibodies are fixed to the surface of the transducer to act as bioreceptors. A solution, which is normally a salt containing buffer, is then introduced to the transducer, where there is only an interaction of antibodies with the antigens [10].
