New trends in immunoassays.

This article takes a special focus on signal amplification technologies in immunoassays and new generations of lateral-flow assays. Novel signal amplification technologies based either on new classes of biofunctional nanocrystals consisting of releasable fluorophores or on aggregation-induced emission (AIE) can improve the sensitivity and the limits of detection in immunoassays. A bio-barcode assay also allows signal amplification by utilizing antibody-coated magnetic beads to concentrate the analytes and antibody-coated gold nanoparticle probes to carry with a large number of oligonucleotides. These innovative technologies boost the development of immunoassays. Growth in rapid immunoassay is fueled by the increasing number of diabetics, the globalization of infectious diseases and the surge in cardiovascular and other chronic diseases as well as other chronic conditions. Rapid, near patient, decentralized, point-of-care (POC) tests are emerging as a tool for more efficient diagnosis and patient evaluation. Technological innovations in lateral-flow assays have enabled a move to bring testing closer to the patient. A novel "digital-style" lateral-flow assay provides semi-quantitative results by simply counting the number of red lines in the test without any expensive reading instrument. An immuno-threshold-based assay can give a signal directly proportional to the concentration of a hapten to prevent confusion on interpretation of the test results. In addition, POC tests become more meaningful to healthcare professionals by combining the benefits of new technologies to provide quantitative results. A molecular compact disc provides a high-resolution imaging capability that can identify and quantify many different antigens simultaneously in highly complex immunoassays. Further advances in immunoassays will bring diagnostic testing even closer to the patient, and can help physicians to monitor diseases that require immediate test results, thereby enhancing the quality of patient care.