A 'mimic' makes PSA test for prostate cancer much more accurate

Scientists have created a new technology that is 110 times more sensitive than that used in the conventional PSA lab test for prostate cancer, according to a study published online September 3, 2015 in ACS Nano.

If this discovery is developed and proven effective, such a test could significantly reduce the number of false negatives in prostate cancer screening.

Current serum tests use the enzyme peroxidase to accelerate chemical reactions and increase the detectability of prostate specific antigen (PSA).

But peroxidases have a number of drawbacks. They can be difficult to extract and purify, and because they are made of protein, they are not dependably stable.

“Moreover, their efficiency is just fair,” said lead investigator Xiaohu Xia, PhD, assistant professor of chemistry at Michigan Tech, in Houghton, MI. “We wanted to develop a mimic peroxidase that was substantially more efficient than the natural peroxidase, which would lead to a more sensitive PSA test.”

So, Dr. Xia and his team, including researchers from Louisiana State University and the University of Texas at Dallas, sought to develop a highly efficient mimic of peroxidase. They engineered it by wrapping ultrathin skins of iridium—just a few atomic layers thick—around nanocubes of palladium.

The researchers conducted PSA tests using the palladium-iridium catalyst, and found that it was 110 times more sensitive than tests completed with the conventional peroxidase (which is derived from the horseradish root).

The investigators now know that it works, but are still trying to understand why it works so well. “We know the iridium coating is the key,” Dr. Xia said. “We think it makes the surface sticky, so the chemical reagents bind to it better.”

Regardless, Dr. Xia hopes that this peroxidase mimic will eventually be used to save lives through earlier detection of cancer and other diseases.

“After surgery, it’s vital to detect a tiny amount of prostate antigen, because otherwise you can get a false negative and perhaps delay treatment for cancer,” he said. “Our ultimate goal is to further refine our system for use in clinical diagnostic laboratories.”