A groundbreaking customizable immunoassay system developed by Japanese researchers offers rapid detection of disease biomarkers, allergens and other biomolecules with exceptional sensitivity, potentially revolutionising point-of-care diagnostics

Scientists from the Institute of Science Tokyo have developed a novel immunoassay platform that could transform how we detect and measure various biological molecules, from disease markers to environmental contaminants. The system, called OpenGUS, represents a significant advancement in homogeneous immunoassay technology, offering both speed and sensitivity without requiring complex laboratory procedures. The research team, led by Associate Professor Tetsuya Kitaguchi, has engineered an innovative approach using specially designed protein probes that can detect target molecules at extremely low concentrations – in the picomolar to nanomolar range. This level of sensitivity makes it particularly valuable for early disease detection and monitoring.

How the system works

The heart of this new technology lies in its OpenGUS probes – artificial proteins comprising two Z-domains and a spacer, specifically engineered to bind to antibodies. When these probes encounter their target molecules, they trigger the formation of an active enzyme complex that produces either a fluorescent signal or a visible colour change. According to the research paper published in Biosensors and Bioelectronics [1], the system utilises β-glucuronidase (GUS) monomers that assemble into active tetramers when target molecules are present. This clever design eliminates the need for the washing steps typically required in traditional immunoassays. The researchers achieved this feat through strategic mutations in the GUS monomers and careful optimization of the reaction conditions.

Practical applications demonstrated

The research team validated their system by successfully detecting three distinct molecules: a Japanese cedar pollen allergen, a cardiovascular disease biomarker (C-reactive protein), and human lactoferrin, an inflammation marker. These tests demonstrated the system’s versatility across different types of biological targets. “Thanks to our optimization procedure, the immunoassay results can
be confirmed using a smartphone or the naked eye in situations where a fluorometer is unavailable, such as outdoors, at home, or in lessequipped laboratories,” explained Kitaguchi. The system showed particular promise in detecting C-reactive protein, a crucial marker for cardiovascular disease and inflammation. The researchers demonstrated that their method could detect this protein at clinically relevant concentrations, making it potentially valuable for monitoring patients with inflammatory conditions.

Advantages over conventional methods

Traditional immunoassays, while reliable, often require complex procedures and skilled laboratory personnel. The new OpenGUS system eliminates these requirements while maintaining high sensitivity and accuracy. Unlike other modern immunoassay techniques, it doesn’t require long pre-incubation periods at low temperatures or complex genetic modification of antibodies. The system’s ability to provide results within 15 minutes represents a significant improvement over conventional methods that can take several hours. This rapid turnaround time could be particularly valuable in emergency medical situations where quick decisions are crucial.

Looking ahead

The system’s versatility and ease of use could make it particularly valuable for point-of-care diagnostics, high-throughput testing, and environmental monitoring. The researchers demonstrated its effectiveness in real-world applications, including detecting allergens in pollen extracts and biomarkers in human serum and saliva samples. The technology’s potential for use with smartphones opens up possibilities for telemedicine applications, where patients could potentially perform tests at home and share results directly with healthcare providers. This could be particularly valuable in remote areas or during public health emergencies.

Limitations and ongoing development

While promising, the system does have some limitations. The researchers noted that when testing human samples, certain pre-treatments might be necessary, particularly for specimens containing human immunoglobulin G. However, they suggest that future modifications to the binding domains could overcome these challenges. There are also opportunities for further optimization of the system for specific applications. The research team is continuing to work on improvements that could enhance sensitivity and broaden the range of detectable molecules. The research team believes that their customizable OpenGUS immunoassay could become a mainstay in both research and practical settings, potentially revolutionising how we approach diagnostic testing in various environments. The system’s combination of speed, sensitivity, and ease of use makes it particularly promising for future developments in point-of-care diagnostics.

Reference:
1. Zhu, B., Yamasaki, Y., Yasuda, T., Qian, C., Qiu, Z., Nagamine, M., Ueda, H., & Kitaguchi, T. (2025). Customizable OpenGUS immunoassay: A homogeneous detection system using β-glucuronidase switch and label-free antibody. Biosensors and Bioelectronics, 267, 116796. https://doi.org/10.1016/j.bios.2024.116796