Stronger and longer bioluminescence for viral detection

Since the COVID-19 pandemic, many point-of-care diagnostic tests have reached the market, but despite this, many have only limited accuracy.

“One major problem with almost all of these rapid tests is the sensitivity and specificity of these assays, especially when you're dealing with samples with a clinically relevant, low amount of the target virus,” explains Hadi Shafiee, whose team develops new diagnostic tools at Harvard Medical School.

Shafiee’s group has now developed an easy-to-use bioluminescent diagnostic test that can accurately detect several viruses in blood serum (Nat. Biomed. Eng. 2025, DOI: 10.1038/s41551-025-01405-9).

Using bioluminescent proteins from nature, such as the firefly luciferase used to make this test, is not new. However, the luminescence cascade–based sensor (LUCAS) assay created by Shafiee and his team produced a much stronger signal that lasted eight times as long as those of other available bioluminescent tests.

The team achieved this increase by adding an intermediate enzyme, β galactosidase, to a target antibody specific to the virus. This reacts with the luciferase to create an enzyme cascade that creates a continuous light signal for at least an hour.

“The 500-fold increase in signal is significant because I think the principle that is used is really interesting,” says protein engineer Maarten Merkx at Eindhoven University of Technology, who was not involved in the work. “It addresses a problem that luciferases sometimes have, [which] is that they don’t generate a lot of photons.”

The LUCAS assay was able to detect SARS-CoV-2, HIV, and hepatitides B and C in serum to a high degree of accuracy in less than 25 min, even when the test was carried out by nonexperts. Notably, a head-to-head comparison with currently available HIV tests on samples with low viral counts showed that the LUCAS system achieved an accuracy of 96%, compared with 74–82% for the other tests.

To make the system easy to use, the team developed an automated microfluidic cartridge controlled by a smartphone app, as well as a simple-to-use electronic sample reader. The estimated costs were under $3 for the cartridge and less than $90 for the reader.

“There is huge potential for something like that in underserved communities,” Shafiee says, although he acknowledges that the technology is still at an early stage.

Merkx agrees about the promise of the test but adds, “My main concern if you really want to use these devices in remote areas is the stability of the components . . . especially if you think about point-of-care applications where you'd like to have long-term stability and storage of your solutions.”

The researchers now want to test the technology with other sample types, like saliva and urine, as successful tests with these would make the technology even easier and less invasive to use. They also plan to explore testing for other diseases.