July 6, 2023 | Florida State University chemists are leading the development of a sensing platform based on the concept of energy transfer quenching, which makes dye-labeled peptides glow when mixed with a patient sample containing a cancer biomarker known as MMP-14 (matrix metalloproteinase-14). The new test employs a gold nanoparticle decorated with dye-peptides on its surface that brighten in the presence of ultraviolet light when interacting with the enzyme, according to Hedi Mattoussi, a professor in the department of chemistry and biochemistry.
“This is a kinetic process that requires a given concentration of MMP-14 and a certain reaction time to take place,” he explains. When the enzyme encounters the biosensor, the peptides are cleaved, freeing a fragment attached to the dye, which lights up because the gold is no longer quenching the dye emission. The light glowing from the sample can be measured to learn if the cancer marker is present in the sample and at what levels.
Cancer has many biomarkers but those in the MMP family are linked to tumor proliferation, differentiation, and angiogenesis. MMP-14 is most notably involved in regulating breast cancer progression and allowing tumor cells to escape and metastasize, says Mattoussi.
The platform has been tested on serum blood samples, which have also been spiked with the enzyme, in studies evaluating its clinical potential as a cancer detection assay. This platform can possibly be developed into a rapid multiplex test rivaling that of multiple lateral flow assays developed for diagnosing COVID-19, he continues. But the next step is to apply the technology to cell culture in the lab and “optimize the conditions for it to work” when using more complex samples.
Since there are peptides for every enzyme, the long-term vision here is creation of a multiplex test with a suite of cancer biomarkers, he says. Biosensors are now quite common as well as easy to implement and non-toxic. Moreover, other tests based on gold nanoparticles have shown great promise in diagnosing as well as treating disease.
A particularly appealing feature of the sensing platform is its simplicity, says Mattoussi. The same sort of approach has been pursued by other groups for DNA conjugation to gold nanoparticle surfaces for the directed assembly of materials, biosensors, and drug delivery.
Oftentimes the problem with these gold nanoparticle platforms is maintaining stable conjugation. Mattoussi and his colleagues have worked hard to keep the peptides used in their test from getting denatured, which can lead to adverse patient reactions such as undesired immune responses. With that issue resolved, a biosensor that delivers results in as little as 30 minutes can be developed, he says.
Regulatory approval of the platform is not expected to be particularly difficult because of the vast number of biosensor-based devices that have already been approved by the Food and Drug Administration, Mattoussi adds. The biggest issues will be ensuring that the test can be done quickly and inexpensively on human samples and, perhaps most importantly, can be multiplexed.
The simplicity of the testing method is tied to the fact that gold nanoparticles are ideally suited to be molecular “beacons” based on the concept of fluorescence quenching, he says, which has generated tremendous scientific interest across physics, chemistry, and imaging in biology. Encouragingly, as used here, they are also proving to be highly sensitive to low volumes of the pan-cancer MMP-14 biomarker.
Which is not to say that simultaneously detecting multiple enzymes will be easy. Even going from one to two biomarkers can be many times more than twice as complicated, says Mattoussi.
In parallel with their commercial ambitions, the research team hopes to simply learn more about the kinetics of the interactions between nanoparticles decorated with peptides and the target enzyme. A follow-up study, for example, will look at differences in speed of movement of the nanoparticles in a liquid based on their sizes and the number of peptides on their surfaces. Speed impacts the bound peptides’ “collision interaction” with an enzyme such as MMP-14.