(A) An overview of midland blotting. The sensor is incubated in the presence of a Horseradish Peroxidase (HRP)-conjugated reagent which recognizes a target group of interest (R) upon the biosensor surface. Upon addition of a luminol-based developing reagent, HRP catalyses a reaction which generates a chemiluminescent (light) signal, which is proportional to the amount of bound HRP. (B) Target groups can include: (i) functional groups upon polymers or Self-Assembled Monolayers (SAM), such as amines (NH2) or carboxyl groups (COOH), which can be detected by biotinylation and subsequent addition of HRP-streptavidin; (ii) bioreceptors, such as antibodies, which can be detected using HRP-conjugated secondary antibodies; (iii) bound analytes, which can be detected using primary antibodies coupled with HRP-conjugated secondary antibodies.
