Michigan Tech researchers working on test strips for cancer detection

HOUGHTON — Detecting cancer could soon be as easy as a home pregnancy test.

Currently, commercially available test strips are not sensitive enough to detect the very low concentrations of cancer biomarkers in blood, compared to pregnancy biomarkers present in urine.

Now, platinum-coated gold nanoparticles developed by a team led by Michigan Technological University researchers could change that to make cheap and simple cancer detection by test strip a reality.

The research, led by Xiaohu Xia, an assistant professor of chemistry at Michigan Tech, was published recently in Nano Letters (DOI: 10.1021/acs.nanolett.7b02385).

Gold Nanoparticles with Platinum Skins

Gold nanoparticles have been used widely for decades for in vitro diagnostics to make medical care and treatment decisions quicker and easier for physicians and patients. What is new with Xia’s research is adding a dual function to the nanoparticle by decorating each tiny sphere in a thin skin of platinum.

Doing so makes it easier for the naked eye to observe changes on the test strip. It also increases the accuracy and provides quantifiable results for extremely low concentrations of key biomarkers, which are measured in picograms per milliliter. In Xia’s study, they focused on prostate-specific antigen (PSA), looking for signals of mere trillionths of a gram in a single drop of blood.

“We require the detection to be very sensitive,” Xia said, explaining that platinum is a great catalyst and a little goes a long way to boost the chemical reaction that causes a test strip stripe to show up. “Gold nanoparticles are a distinct red color and as long as the platinum is ultrathin, the red of the gold nanoparticles will show through.”

Xia’s team took that improvement a step further: they created a low-sensitivity mode (color from gold nanoparticle cores) and a high-sensitivity mode (color produced by platinum skins through catalysis) to detect PSA. As the photo below shows, the high-sensitivity mode greatly improves test strip visibility; the low-sensitivity mode is on par with commercially available test strips.

Gold nanoparticles appear red on test strips; the high-sensitivity mode developed by Xia’s team is much darker on the test strip and shows a two-magnitude increase in sensitivity. (MTU photo)

Detecting Disease

What’s more is that Xia estimates the thin platinum skin will not significantly increase the cost of current gold nanoparticle test strips on the market and the design is compatible with detecting other kinds of cancer biomarkers.

“A key component in the test strip is the antibodies, which are unique to each cancer biomarker, and are commercially available,” he said. “We can easily replace the antibody, so this is a general detection platform.”

The next step, Xia said, is verifying the application for other cancer biomarkers and even experimenting with applications for infectious diseases.

“The advantage of this technology is simple,” he said. “Point-of-care devices mean people can buy them and do diagnosis on their own; in a clinic, this is a cheap and quick technique that also improves diagnosis and therefore treatment.”

This work was supported in part by the startup funds from Michigan Technological University and a National Science Foundation (NSF) Career Award (CHE-1651307). Part of the electron microscopy work at Brookhaven National Laboratory was supported by the U.S. Department of Energy, Basic Energy Sciences, Division of Materials Science and Engineering, under Contract No. DE-SC0012704.

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