ABSTRACT
Immunoassays can be immunometric or competitive systems. They can be further sub-divided into direct, indirect, competitive or sandwich immunoassay formats. This chapter outlines important points to be addressed before carrying out an immunoassay or optimisation of assay protocols. Biological matrices comprise many components such as lipids, crystals, unwanted cells, minerals and proteins, all of which may impact on the sensitivity and reproducibility of the immunoassay. Antibody-conjugated quantum dots can be used as detection molecules in sandwich and indirect immunoassays. The most commonly used buffers in immunoassays are phosphate buffered saline and tris-buffered saline. The main objective of incorporating washing steps into immunoassays is to separate unwanted and non-specific proteins from specifically bound protein, thus helping to reduce background noise. Fluorescent immunoassays or Fluorescence-Linked Immunosorbent Sandwich Assays use the same basic steps as standard enzyme-linked immunosorbent assays but differ in that the enzyme conjugated to the detection antibody use substrates that produce a product that emits fluorescence instead of colour.
