A biosensor is an analytical device which combines a biological component with a transducer to convert a biological response into a detectable electronic signal. It has three components, the biorecognition site; the transducer; and the reader. The bio-recognition site or bioreceptor is the biological component that will interact with the analyte. This must selectively recognise the analyte of interest. Common bioreceptors include microorganisms, antibodies, enzymes, cells, and DNA. An immunosensor is a biosensor which exploits the highly specific antibody/antigen interaction. Either an antigen is immobilised onto the transducer surface and detects the antibody, or the antibody is the bioreceptor immobilised on the transducer and it detects the antigen. The interaction between the antigen and antibody cause a variation in electric charge, mass, optical or temperature properties detectable by the transducer. The transducer converts the event at the bio-recognition site into a measurable signal, which is proportional to the analyte/bioreceptor interactions. Examples of transducers include optical, electrochemical, piezoelectric and electrochemiluminescent devices. Their signal is processed by the reader and displayed in a user-friendly format. Electrochemical transducers present many advantages including their robustness, easy miniaturization, excellent detection limits, small sample volumes, ability to be used in turbid biofluids, and compatibility with integrated circuits and microfluidics. Due to these characteristics, electrochemistry devices are often adapted for pointof-care (POC) platforms. Furthermore devices can be designed to allow for simultaneous measurement of different analytes. Electrochemical impedance spectroscopy (EIS), in particular, can sensitively monitor the changes in capacitance or charge-transfer resistance associated with material binding at specifically prepared receptive electrode surfaces, and requires no prior labelling. Typically, biosensors require a label such as a fluorophore, enzyme, or nanostructure to enable detection. Labelling techniques can change binding properties of biomolecules, increase costs, assay time and requires extra sample handling making them unsuitable for POC devices. 9