Tapered fiber sensor usable for head and neck cancer screening

Head and neck squamous cell carcinoma (HNSCC) is a fatal disease with 650,000 newly diagnosed cases worldwide. Early detection of this cancer improves survival significantly. Salivary biomarker analysis demonstrates that screening of HNSCC is possible and potentially improves survival. Interleukin-8 (IL-8), a cytokine produced in abundance by the HNSCC stem cells, induces epithelial-mesenchymal transformation (EMT), enhances metastasis, and can be used as a salivary biomarker for HNSCC screening. A healthy individual has 300 - 500 picogram/ml (pg/ ml) in saliva, while HNSCC patients have 1700 - 2500 pg/ml. We have developed a novel tapered optical fiber biosensing system for label-free detection of antigens by attaching a molecular recognition agent to a tapered fiber surface for augmenting sensitivity and specificity of the analyte. In a tapered fiber, the evanescent electromagnetic field, which extends outside the fiber, is able to detect minute changes of the refractive index caused by the environment. The evanescent field intensity exponentially decreases with distance away from the surface of the fiber on a length scale in the order of the wavelength of light. Light from a tunable fiber laser is introduced into the tapered fiber from one end and the transmitted intensity is detected by a photodetector. Received data is then analyzed using Fourier transformation to find phase changes related to the biomolecular coating of the fiber, which is directly related to the antigen concentration. Real-time measurement of antigen concentrations at the level of 10 pg/ml is shown to be possible by successful integration of hardware and software systems. This approach has the potential to develop a pointof-care device to be used in the clinics.