Design and application of a new optical fiber and gradient lens biosensor system

The biosensor system of molecular interaction has been wildly used in various research fields, such as bioinstrumentation, pharmacology development, environmental monitoring, medical examination, and clinical diagnostic reagents development. This system can simultaneously achieve the kinetic parameters of molecules interaction, determination of biological molecular, and the concentration of antibody, protein, DNA or other molecular. In this paper, a new gradient lens-optical fiber-gradient lens composition biosensor System was designed. It is based on the thin film interference principle, followed by the Snell's Law. Established qualitative and quantitative relationship between the film thickness increment and the biomolecule. Data simulation using ZEMAX optical soft indicated that the best biosensor probe design was that the length and core diameter of the optical fiber were adopted 40mm and 400μm while the thickness and diameter of the gradient lens were 2.24mm and 1.0mm. In the light spot footprint distribution figure obtained from this biosensor system, the light spot well distributed and relatively high illumination. It can maximum enhance light intensity and light coupling efficiency, and improve detection sensitivity and stability. The end surface of the biosensor probe use high refractive index material coating film design, prepared by electron beam evaporation tantalum pentoxide (Ta2O5) film, the thickness 20nm, the refractive index 2.1. And use the same method prepared a silicon dioxide (SiO2) thin film layer 700nm. The SiO2 layer covalently immobilize antigen to the end surface of the biosensor probe through hydroxylation treatment and chemical reagent modification. Applied this system, the association constant, dissociation constant and affinity constant of the horseshoe crab factor G protein and carboxymethyl 1,3β-D-glucan were obtained 3.346×104 (1/Ms), 9.792×10−4 (1/s) and 2.926×10−8 (M), respectively. Calibration curves y = 0.0869ln(x)+0.262, were created for carboxymethyl 1, 3β-D-glucan ranging 0.15625μg/ml to 20μg/ml. The correlation coefficient (r2) values showed good linearity and the limit of detection was 0.1μg/ml. This rapid and sensitive biosensor system has high practical value, and contributes to the qualitative and quantitative analysis of biomolecules in various fields.