Dual-resonance optical fiber lossy mode resonance immunoprobe for serum PSA detection.

Biomarker detection has emerged as an essential complementary approach for early-stage screening of tumors. Conventional methods are constrained by bulky systems, cumbersome operation steps, and low detection accuracy. Here, we demonstrate a dual-resonance optimally configured lossy mode resonance (LMR) immunoprobe for detecting prostate-specific antigen (PSA), a biomarker for prostate cancer (PCa). The dual-resonance structure used in this study introduces low-refractive-index magnesium fluoride (MgF2) as a matching layer before adding indium tin oxide (ITO) as a lossy mode excitation layer to enhance the phase matching between the evanescent wave and the lossy mode to realize dual-resonance. Compared with classical optical fiber LMR, the dual-resonance effect not only improves the detection precision but also features a high accuracy of joint detection. The limit of detection (LOD) of the optical fiber immunoprobe based on dual-resonance for PSA immunoassay can reach down to 52 pg/mL, making it ideally suited for early risk management and prognostic diagnosis of PCa. In addition, the optical fiber immunoprobe is used to detect suspected PCa patients, with a successful recognition rate of 90% compared with that of standard commercially available chemiluminescent assays. This work may pave the way for promising applications of optical fiber immunoprobe for high-precision, high-accuracy, and portable early-stage screening of tumors.