The Applications of Quenchbody: A Novel Fluorescent Immunosensor

Laura Weiler—Integrated Biomedical Engineering & Health Sciences 2026

Today’s society centers itself around immediacy and efficiency, and these values are also reflected in the world of medical research. Current diagnostic tools are continuously improving thanks to advancements in data manipulation, computer models, and assays.1

Among these advancements are Quenchbodies: fluorescent immunosensors that show promise as a novel, rapid antigen detector for disease diagnosis, food control, and environment monitoring.2

A Quenchbody (Q-body) uses an antibody fragment to detect a specific molecule (called an antigen or analyte) in an immunoassay.2 Antibodies are molecules involved in the immune response that detect a particular analyte, for example, a specific hormone, virus, or vitamin.3

Enzyme-linked immunosorbent assays (ELISAs) are frequently used immunoassays due to their high specificity and accuracy in detecting an analyte.4 A downside to an ELISA is that it requires additional steps to wash away any excess sample or antibodies throughout the process.5

Another type of immunoassay is a fluoroimmunoassay, which labels the antibodies with fluorescent tags and quantifies the antigen concentration using fluorescence (i.e., such that higher fluorescence means higher antigen presence).3 Q-bodies provide an innovative take on fluoroimmunassays due to their simplicity and accuracy.6

What is notable about a Q-body is that it does not involve any additional reagent or separation steps, as is the case with an ELISA.7 Ueda et al.7 discovered a “single chain variable region fragment” (scFv) of a fluorescent-labelled antibody which increased in fluorescence when the label was displaced by an antigen. Ueda et al.7 called it a Q-body: an scFv (also called a fragment antibody (Fab)) and a specific fluorescent label so that presence of the antibody’s antigen can replace the label.7 The name “Quenchbody” comes from the mechanism behind this enhanced fluorescence, which involves a naturally-occurring amino acid called tryptophan (Trp).7 Trp contained in an antibody interacts with the dye in the fluorescent tag and “quenches” or suppresses its fluorescent properties unless an antigen replaces the fluorescent label at the Fab, causing the label to fluoresce, as depicted in Figure 1.8 Generally, a Q-body can be made from any antibody and specific scFvs are readily available, making Q-bodies valuable tools for a variety of applications.7

Figure 1: Quenchbody Mechanism.

SOURCE: Creative Biolabs

The Q-body immunoassay has already been tested for its applications to monitor neonicotinoids for environmental and food safety.9 Neonicotinoids are known for their uses in insecticides, particularly Imidacloprid (ICP), the most popular insecticide worldwide.9 Neonicotinoids lead to paralysis and death of insects at even low doses and contribute to honey bee colony collapse.9 Since crop seeds are often coated with the insecticide before being planted, plants, nectar, and pollen may contain low concentrations of neonicotinoid.9 Conventional methods (gas or liquid chromatography and mass spectrometry) used to quantify pesticide residues are often time-consuming and lack portability.9 This is where using a Quenchbody assay comes in handy. The assay was completed within two minutes and successfully quantified ICP residues with a slightly lower sensitivity than when using an ELISA.9

As for other applications, researchers have been looking at using Q-body to monitor drug misuse, for cancer diagnostics, in vitro or in vivo imaging, and for SARS-CoV2 detection.6,8 Ueda et al.10 concluded that the Quenchbody measured the SARS-CoV2 nucleocapsid protein better than current lateral flow antigen tests. While the functionality and production of the Q-body assay still need to be fine-tuned, it offers a sensitive, simplified, rapid antigen detection system with a promising range of applications in medicine and health.


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