In a study published this week in the Journal of the American Chemical Society, scientists present a new type of immunoassay that is capable of detecting small molecules with 50-fold greater sensitivity than conventional detection methods. The new method can also be easily integrated into existing diagnostic platforms.
Health monitoring and disease diagnosis depend on technologies that detect levels of small molecules, such as proteins, hormones, and drugs. However, some molecules are so small that they cannot be detected by the most widely available analysis techniques, leaving questions about crucial substances like amino acids, sugars, and lipids largely unanswered.
"The enhanced analytical sensitivity of our assay enables measurements of small molecules at extremely low concentrations, and opens a window into biological phenomena that were previously unreachable," says senior author David Walt, Ph.D., of Harvard University.
The new approach is based on a type of analysis called a competitive immunoassay. In a competitive immunoassay, a sample with an unknown concentration of a molecule of interest is added alongside a known concentration of the same molecule to an array of antibodies. The labeled and unlabeled molecules then "compete" for antibody binding sites, making it possible to determine the unknown concentration.
In this study, the researchers created two types of competitive immunoassays based on the Simoa system from Quanterix™ to detect small molecules at the single-molecule level. They used their new assays to analyze two small molecules that are important for normal human body function: cortisol and PGE2. Cortisol is widely used to evaluate the function of the adrenal, pituitary, and hypothalamus glands, while PGE2 is a hormone-like prostaglandin molecule that influences inflammation, fertility, and immune function. The new competitive methods were able to detect their targets within about an hour and with up to 50 times greater sensitivity than a conventional ELISA.
"Our plan is to use this method in diagnostics for improved detection of hormones in blood samples," says first author Xu Wang, Ph.D., a Postdoctoral Research Fellow at BWH and the Wyss Institute.