Rapid and label-free detection of breast cancer biomarker CA15-3 in clinical human serum samples with optofluidic ring resonator sensors.

Sensitive and specific detection of breast cancer biomarker CA15-3 in human serum is an important step toward successful evaluation of clinical treatment and prediction of breast cancer recurrence. In this work, we developed an optofluidic ring resonator (OFRR) sensor and the corresponding sensing protocols for label-free CA15-3 detection without any additional signal amplification steps. Nonspecific serum protein adsorption was minimized with effective surface blocking methods. The sensor performance for CA15-3 detection was first characterized in phosphate-buffered saline (PBS) buffer and in fetal calf serum. Then the potential use of the OFRR as a simple clinical laboratory testing device for breast cancer diagnostics was tested by measuring the CA15-3 level in clinical human serum samples, and the results were compared with those of standard clinical lab tests. It was found that the OFRR was capable of detecting approximately 1 unit/mL CA15-3 in both PBS buffer and diluted serum within approximately 30 min. Our work marks the first demonstration of the optical ring resonator biosensor in real clinical applications that features low cost, simple detection procedures, rapid response time, low sample consumption, and high specificity.