New One-Step Syphilis Test Could Enable Earlier Detection and Faster Treatment

Syphilis can be difficult to diagnose because its symptoms may resemble other diseases and appear and disappear without treatment. Undetected infection can continue causing harm, spread to partners and pass to babies during pregnancy. In 2024, nearly 4,000 babies in the U.S. were born with syphilis. To support earlier detection, researchers have developed a rapid testing approach designed to identify low levels of antibodies associated with the infection.

Researchers at the Pennsylvania State University (Penn State; University Park, PA, USA) have developed a new pilot rapid syphilis testing device that integrates the treponemal and non-treponemal blood test sequence into one format. The test is designed to detect antibodies against Treponema pallidum and separate antibodies associated with disease-related cellular damage. This approach is intended to reproduce established diagnostic information in a faster, potentially point-of-care format.

The device uses multilayer gold-silver-gold nanoparticles instead of conventional gold nanoparticles to generate a stronger visible test line. The silver layer provides stronger optical properties, while the gold layers help preserve particle stability. Before embedding the particles in a lateral flow reporter, the researchers found that six times fewer multilayer particles were needed to form a visible mark than gold alone, and the particles remained visible with three times fewer sample target molecules.

The team evaluated the nanoparticles using 36 clinical specimens spanning a range of antibody concentrations from the U.S. Centers for Disease Control and Prevention and Boca Biolistics. In those experiments, line intensities increased 19% to 46% compared with conventional gold nanoparticles. The largest gains occurred in tests detecting antibodies at the lowest concentrations.

The study was published in ACS Sensors and involved Penn State, Penn State College of Medicine, and Louisiana State University. The researchers stated that two rapid syphilis tests have been approved by the U.S. Food and Drug Administration in recent years, but these detect only treponemal antibodies. They also stated that no single-step confirmatory syphilis test is approved for U.S. use, and that a European test does not detect antibodies in the low-titer range.

The team has applied for a patent for the device and is exploring industry partnerships as it moves toward larger validation studies, further prototype development, and regulatory submission. The researchers said the approach could shift testing from a multistep laboratory process toward diagnosis and treatment during one clinical visit.

“The low-titer range, meaning the range with the lowest concentration of antibodies, is particularly challenging for detecting syphilis. This range is also clinically important, occurring during early infection, later stages of syphilis or after treatment when antibody levels are declining to make sure treatment worked,” said Dipanjan Pan, Penn State’s Dorothy Foehr Huck & J. Lloyd Huck Chair Professor in Nanomedicine.

“We could potentially move syphilis testing from a multistep laboratory process toward a model of testing, diagnosing and treating in a single clinical visit,” concluded Pan.

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