Polymer composite fiber-optic Fabry–Perot cavity sensor based on Ti3C2TX MXene enhanced photothermal effect for low-concentration bilirubin detection

The World Health Statistics 2023, as presented by the World Health Organization (WHO), underscores a significant global health concern: 73% of global mortality is attributed to chronic diseases. Within the domain of medical diagnostics, serum bilirubin levels serve as a critical biomarker for identifying several prevalent chronic conditions in adult and geriatric populations. In this study, a polymer composite fiber-optic Fabry–Pérot interferometer is prepared, wherein the reflective surfaces are, respectively, constituted by polyurethane (PU), with characteristics marked by high thermal responsiveness and rapid thermal transfer rates, and a single-mode fiber. Subsequently, the outer surface of the PU reflective end undergoes deposition with Ti3C2TX MXene material, which has the capability to enhance the adsorption of bilirubin molecules. This work proposes a detection method using the photothermal effect of bilirubin. When the sensor is operational, bilirubin generates a thermal effect under 405 nm laser irradiation. The Fabry–Pérot air cavity rapidly expands with the increased heat absorption, leading to shifts in the interference spectrum, which enables the effective detection of low concentrations of bilirubin within the serum. The experimental results indicate that the sensor exhibits a sensitivity of 7.51 [nm/(μmol/L)] and a detection limit of a mere 0.002 19 μmol/L within the linear dynamic range of 1–10 μmol/L. Furthermore, a tenfold improvement is observed when compared to the previously reported lowest detection limit. The sensor delineated herein is characterized by heightened sensitivity, minimal detection limit, rapid response time, and substantial robustness, rendering it suitable for potential applications in the early diagnosis and prognosis of chronic diseases such as Alzheimer's disease.