A newly developed Bluetooth-enabled biosensor allows for rapid, highly sensitive detection of two breast cancer biomarkers—human epidermal growth factor receptor 2 and cancer antigen 15-3—in saliva. The device achieves an impressive limit of detection of one femtogram per milliliter for both markers. This sensitivity is four to five orders of magnitude greater than that of conventional enzyme-linked immunosorbent assay methods. The technology offers a promising approach to noninvasive breast cancer screening and monitoring because results are available at the point of care or in remote settings, the study authors described.

Analytical Performance

The biosensor detected statistically significant differences in salivary human epidermal growth factor receptor 2 (HER2) and cancer antigen 15-3 (CA15-3) levels among healthy participants, patients with in situ cancer, and patients with invasive cancer. Both cancer groups differed from healthy controls.

• HER2: Limit of detection = one femtogram per milliliter; sensitivity = 95 units per order of magnitude increase in concentration.

• CA15-3: Limit of detection = one femtogram per milliliter; sensitivity = 190 units per order of magnitude increase.

A support vector classification model that combined HER2 and CA15-3 results achieved a test accuracy of 89%, with a high recall for patients in the diagnostic group.

According to the authors, led by Hsiao-Hsuan Wan, of the Department of Chemical Engineering at the University of Florida in Gainesville, the higher sensitivity for CA15-3 is attributed to its molecular size and greater number of glycosylated epitopes, which enhance antibody binding and electrochemical signal. The system outperforms standard enzyme-linked immunosorbent assay (ELISA) methods, which have limits of detection of 10⁻⁸ to 10⁻¹⁰ grams per milliliter for HER2 and about 10⁻⁹ grams per milliliter for CA15-3. Results are available in real time, whereas traditional laboratory assays or invasive tissue biopsies require hours. 

The biosensor’s limit of detection is up to 10,000 times lower than ELISA, and, unlike tissue biopsy, the new device is completely noninvasive and enables remote or home monitoring. The device’s portability and rapid performance are also well-suited to mobile health units and cancer screening initiatives, and could expand early detection efforts, especially in rural or underserved regions.

Methods and Device Architecture

The researchers tested the biosensor using saliva samples (n = 29) obtained from the University of Florida Clinical and Translational Science Institute Biorepository (UF IRB202101643). The cohort included 11 healthy volunteers, 5 with in situ breast cancer, and 13 with invasive breast cancer. Samples were stored at −78°C and applied directly to the sensor, without prior dilution or filtration. Among the cancer samples, HER2 biopsy scores were available for comparison in 14 cases.

The biosensor integrates a reusable printed circuit board with commercially available glucose test strips (Luvnshare Biomedical Inc., Hsinchu, Taiwan), which are specially prepared to detect HER2 and CA15-3 proteins. Test strips are treated with ozone, cleaned, and then functionalized with a solution that enables specific binding of monoclonal antibodies for HER2 or CA15-3. Strips are sealed and stored until use. More than 95% demonstrated high functionalization quality.

The printed circuit board includes a microprocessor to generate test pulses, a closed-loop amplifier for sensitivity, and a Bluetooth Low Energy module for wireless communication with a smartphone application. The system supports simultaneous detection of HER2 and CA15-3, and results are displayed in approximately one second. The device is compact (65 × 45 × 20 mm) and consumes roughly 45 milliwatts.

Limitations and Next Steps

This study represents a proof of concept with promising sensitivity and reproducibility in a small cohort of clinical samples, the authors concluded. They added that broader validation in larger, more diverse populations is necessary before routine clinical adoption.

Funding, Patents, and Disclosures

This work was supported by the National Institute of Dental and Craniofacial Research, University of Florida College of Dentistry Faculty Seed Grant, and the National Science and Technology Council, Taiwan. A provisional patent that covers the device technology has been filed (PCT/US2024/60095). The researchers reported no competing interests.

Source: biosensors