Abstract
Phage Display and Selex are combinatorial technologies that use in vitro, ex vivo and in vivo functional selections for the discovery of novel ligands against specific biological targets. Phage Display is a technology for biological selections using combinatorial libraries that display very diverse set of random peptides or very large repertoire of antibody fragments fused to the capsid surface of filamentous phage that have been successfully exploited for the discovery of novel biomarkers. Such molecules can be either peptide ligands that mimic epitope regions (mimotope) or monoclonal antibody fragments (Fab or scFv). The selected mimotopes of proteins, carbohydrates, and lipids may be used as individual epitope-mimicking antigens or immunogens, and can also be directly used in phage-based ELISA immunoassays, resulting in simple, specific, sensitive, and low-cost immunodiagnostic tests. Similarly, the selection of antibodies from combinatorial libraries has also become an important tool for the generation of reagents, diagnostics, and therapeutic molecules. It is the only method to obtain specific antibodies bypassing the immunization step, which mimics the maturation process of human antibody in vivo, resulting in high affinity antibody ligands, which may be suitable to human administration and potentially applicable to clinical diagnosis and treatment. Another important combinatorial technology is the selection of aptamers through Selex. Random RNA or DNA sequences with conformational actions specifically bind to a variety of targets, including proteins, small molecules, oligonucleotides, and peptides. Such ligands are evolved during several cycles of selection, elution, PCR amplification, cloning and transformation. Aptamers offer several advantages over other common biomarkers, which include the similar molecular recognition of antibodies, the chemical synthesis in test tubes at very low costs, resistance to high temperatures and humidity, lack of immunogenicity, high potency and specificity. I will discuss on how combinatorial technologies may reveal functional determinant sites of molecules, and in combination with multiple research tools, nanotechnology, and instruments may entirely enable novel approaches for diagnostics and therapeutics of human diseases.