They are presented as a powerful tool for the development of PoC devices, as they combine the high specificity of enzymes, with the advantages of electrochemical methods, including easy handling, sensitivity and compatibility with screen-printing, which allows the low-cost mass production of miniaturised devices. This has led to a steady growth in recent years in the development of enzymatic biosensors for application in the detection of a wide variety of analytes.

The operation of these biosensors is based on the immobilisation of an enzyme (chosen so that the substrate of this enzyme is the analyte to be determined) on the electrochemical transducer, which, after being exposed to a sample containing the target analyte, will transform the biological recognition process (which occurs between the enzyme and the analyte) into a quantifiable response (such as a current) that will allow us to determine the presence of the analyte in the sample analysed.

Lateral flow (LF) immunoassays, such as the world-renowned pregnancy test, have dominated the rapid diagnostic market. These devices, based on the use of nitrocellulose membranes to support immunological reactions, are portable, fast and easy to use, allowing for Point of Care, PoC testing.

The operation of this type of FL immunosensors is based on the migration of a sample through a porous paper substrate, on which the immunological reactions take place. If the analyte is present in the sample, it can be detected visually by the appearance of a coloured band. This visual evaluation allows a qualitative analysis, but could be analysed quantitatively by means of a portable FL strip reader.