Diagnostic Applications of Phycobiliproteins

Phycobiliproteins (PBPs) are widely used as fluorescent detection system in both medical and non-medical diagnostics. This chapter focuses research arena with extensive coverage of patents and commercial products. Being unique and brilliantly colored proteinaceous photosynthetic accessory pigments of algal kingdom, they were mainly employed in the diagnosis of human metabolic disorders, infectious diseases, cancers, and immune disorders. It was further extended to the prognosis of few human diseases too. They find novel applications in human theranostics either as fluorescent detection component or both as detection system and therapeutic molecule. Apart from medical diagnosis, they were largely used in the diagnosis of cell components, cell lineages and subsets, and other biological and environmental probing too. It was further extended to the diagnosis of pathogenic diseases in birds and mammals. There are available extensive patented research on the development of methods of using them as detection probes in the form of molecular tags, protein conjugates, fusion proteins, antibody conjugates, and with DNA probes. Their incorporation into micro beads, magnetic beads, and biochips were elaborate. Globally, several companies market diagnostic products of PBPs in the form of preparations like streptavidin conjugates, activated PBPs, fluorescein isothiocyanate (FITC) cross-linked forms, purified and activated forms, antibody conjugates, and as multi-color detection systems including custom designing. Among various phycobiliproteins, phycoerythrins find common application followed by allophycocyanin and phycocyanin. Generation of novel hybrids and conjugates coupled with improvement in signal generation and amplification that helps in early diagnosis are in the offing.