Reflector-less nanoparticles doped optical fiber biosensor for the detection of proteins: Case thrombin.

A miniature biosensing platform based on MgO-based nanoparticle doped optical fiber was developed for the biomolecule detection. The technology used a single mode fiber with MgO-based nanoparticles doped core. The detection was based on collecting the Rayleigh backscattering signatures with increased gain upon the etching of the fiber 1-2 mm away from the tip. The shift from the backscattered signal with the maximum value of the cross-correlation was used to report the results. The sensor exhibited a sensitivity range from 0.75 nm/refractive index unit up to 19.63 nm/refractive index unit for a refractive index range from 1.3329 up to 1.37649. The deposition of the thin gold layer increased the overall sensitivity of the biosensor by 3.7 times for the etched part of the fiber with diameter 8-9 μm. The proposed biosensor was tested for the detection of thrombin molecule concentrations ranging from 0.625 μg/ml to 20 μg/ml. Thiol modified DNA specific aptamers were used to functionalize the gold coated surface of the fiber for the detection. The sensor showed detectable sensitivity and specificity as compared to the other control proteins. The proposed biosensing platform could be multiplexed and can be used in vivo for the detection in clinical settings due to its miniature size, biocompatibility of silica glass and reflector less set up.