Ultrasensitive detection of the epidermal growth factor receptor (EGFR) gene in non-small cell lung cancer (NSCLC) remains a critical challenge for early diagnosis and targeted therapy. While fiber-optic biosensors offer promising sensing capabilities, their performance is fundamentally limited by the temperature fluctuation and insufficient limit of detection (LOD). In this work, an approaching 4-fold amplification of EGFR-binding spectral shifts is achieved through the Vernier effect (VE) in the cascaded Sagnac interferometer (SI) and Mach-Zehnder interferometer (MZI), whose free spectral ranges (FSRs) are deliberately mismatched. Temperature compensation is achieved through a contour-based differential demodulation method enabled by integrating a fiber Bragg grating (FBG) into the biosensor, which effectively decouples temperature variations from the deoxyribonucleic acid (DNA) molecular hybridization signals. Functionalized with mercaptoethylamine (MEA)-mediated self-assembled monolayers and single-stranded probe DNA (pDNA) specific to the EGFR gene, the biosensor achieves 53.7-fold specificity discrimination with the 25.1593 nm wavelength redshift for complementary DNA (cDNA) versus 0.4683 nm for non-complementary DNA (nonDNA), caused by refractive index (RI) changes resulting from DNA hybridization between pDNA and cDNA. The biosensor achieves a prominent LOD of 0.03363 pM for the synthetic EGFR gene in the buffer, surpassing existing interferometric biosensors by four orders of magnitude. This work not only establishes a new paradigm for overcoming the temperature drift in photonic biosensing but also employs the VE to significantly enhance the LOD, offering transformative potential for early diagnosis of NSCLC in clinical settings.

This paper proposed a fiber optic temperature sensor with an ultra-wide detection range based on the polydimethylsiloxane (PDMS) film-coated tapered single-mode fiber (SMF). The SMF was tapered at first and then coated with a PDMS film to construct a Mach-Zehnder interferometer (MZI). The PDMS, which has a high thermo-optical coefficient and high light transmittance, was used to enhance the temperature measurement sensitivity in a wide temperature range. Combining it with a fiber Bragg grating (FBG), the device was capable of operating over a wide range of temperature, from −30 ℃ to 200 ℃. The maximum temperature sensitivity was 3.437 nm/℃ and the average sensitivity was 1.777 nm/℃. The techniques presented in this paper can be applied to other interferometric fiber optic sensors by combining the FBG to achieve beyond free spectrum range (FSR) measurement. The proposed temperature sensor has the ease of fabrication, high sensitivity, and a wide detection range, showing its application prospects in temperature sensing.