Polymer coatings can be applied to a variety of electrode materials but unlike alkanethiols, the absorption mechanism for polymer layers is not well understood. They can be formed on the electrode surface using two methods: solution casting of preformed polymers, or electropolymerisation of monomers. Using preformed polymers allows easy control of the particle sizes, but poor adhesion to the electrode surface. Electropolymerisation overcomes this obstacle; it involves the application of an appropriate potential to the working electrode, immersed in an aqueous solution of the monomer, allowing for better control over the deposition thickness than the casting method. Another advantage of electrodeposition is it concentrates the deposition of the polymer to the electrode area and can coat complicated geometries and 3D structures. A one-step immobilisation process can be used by including the biological component in the solution, which will be homogenously incorporated into the growing polymer, during the electropolymerisation. This entrapment of the biological molecules is popular in enzyme-based biosensors but generally is not suitable for an immunosensor. Entrapment of the molecule can diminish its biological activity due to steric hinderance, as the surrounding polymer reduces accessibility to immobilised molecule. Instead this section will focus on two-step immobilisation, where the polymer is first deposited onto the electrode surface and then the antibody or antigen is attached to the polymer layer. A two-step procedure permits the polymer to be deposited in harsher conditions for an optimal layer, while the biorecognition element can still be immobilised in mild conditions to prevent denaturing. 81