Lossy mode resonance-based optical fiber sensors for the label-free detection of osteosarcoma-related biomarkers

Introduction: The effect of cancer on health, society, and global economy makes early identification and treatment of the disease by biomarker detection in body fluids one of the biggest challenges in the modern world. Current gold-standards (PCR, flow cytometry, immunofluorescence, western blotting, ELISA, etc.) remain laborious, operator-dependent, time-consuming, and require large sample volumes. Therefore, an effective and real-time monitoring platform with clinically relevant limits of detection (LODs) for cancer diagnosis using biofluids remains urgent. To fulfil this demand, we introduce a compact biophotonic platform that integrates lossy mode resonance-based optical fiber sensors with embedded microfluidics.

Methods: The device employs a D-shaped single-mode optical fiber coated with a thin film of SnO₂ that supports the generation of lossy mode resonance (LMR), a physical phenomenon enabling high sensitivity and resolution in the detection of biomolecules, while retaining key advantages of optical fibers, such as unique light control, flexibility, electromagnetic immunity, robustness in harsh environments, and compatibility with optoelectronics. Firstly, the sensing surface is functionalized with a commercial polymer (Eudragit L100) to provide COOH groups. Afterwards, the sensor is integrated into a specially engineered microfluidic system and then the sensing surface is passivated with bovine serum albumin (BSA) to suppress nonspecific adsorption and improve assay specificity. Finally, the platform is evaluated across clinically relevant concentration ranges of transforming growth factor beta 1 (TGF-β₁) as an osteosarcoma-related biomarker.

Results: The device showcases excellent analytical performance in a standard running buffer (PBS), with a clinically relevant LOD of 5 pg/mL for TGF-β₁, demonstrating strong potential for early cancer biomarker detection.

Conclusions: These promising results lay the groundwork for the next experimental tests using clinically mimicking biofluids to assess the real performance of the biophotonic sensing device integrated with microfluidics.