High sensitive long period fiber grating biosensor for cancer biomarker detection

We report an innovative fiber optic biosensor based on Long Period Gratings (LPGs) working in reflection configuration for real time monitoring of human Thyroglobulin (Tg), a protein marker of differentiated thyroid cancer. A standard LPG is first transformed in a practical probe working in reflection mode, and then it is coated with a single layer of atactic polystyrene (aPS) in order to increase its surrounding refractive index sensitivity and to provide, at the same time, the desired interfacial properties for a stable anti-Tg antibody. The functionalized reflection-type LPG biosensor clearly demonstrates the effectiveness and sensitivity of the developed biosensing platform, allowing the real time and label-free detection of Tg in the needle washouts of fine-needle aspiration biopsies, at concentrations useful for pre- and post-operative assessment of the biomarker levels. Analyte recognition and capture were confirmed with a parallel on fiber ELISA-like assay using, in pilot tests, the biotinylated protein and HRP-labeled streptavidin for its detection. Dose-dependent experiments showed that the detection is linearly dependent on concentration within the range between 0 and 4 ng/mL, while antibody saturation occurs for higher protein levels.