Research On Highly Sensitive And Fast Response Optical Fiber Nucleic Acid Biosenser

Nucleic acid detection has vital research significance in biomedicine,virus detection,and other fields.Fiber-optic biosensors are a hot research topic in recent years because of their optical approach to biological nucleic acid detection,which has the advantages of label-free,high sensitivity and immunity to electromagnetic interference.In this dissertation,the MachZehnder Interferometer(MZI)and the Tilted Fiber Bragg Grating(TFBG)were used as the sensor head,and the covalent binding method and gold film selfassembly method were used to fix target nucleic acids respectively.The two nucleic acid sensors with fast response and high sensitivity were realized,mainly as follows.1.A fast response fiber optic nucleic acid sensor based on MZI is proposed.The sensing head is made of single-mode optical fiber staggered and fused,and the surface of the fiber is pre-modified using covalent binding method to immobilize the functionalized probe nucleic acid with amino groups on the surface of the sensing head.When the probe nucleic acid is bound to the complementary target nucleic acid on the fiber surface,the effective refractive index of the fiber surface increases,which is manifested as an increase in transmission intensity in the spectrum.The experimental results show that the obtained nucleic acid sensor has a response time of 30 s,which can achieve fast detection;the lower detection limit can reach 1 n M,the concentration sensitivity is 0.175 d B/n M,and it exhibits good linearity.In addition,the present sensor has the function of specificity detection,which can effectively avoid cross-sensitivity in the detection of non-complementary nucleic acids.Finally,the present sensor uses intensity demodulation to detect nucleic acid concentration,which overcomes the shortcomings of wavelength demodulation device such as expensive.2.A high-sensitivity nucleic acid sensor based on Surface Plasma Resonance(SPR)of TFBG is proposed.a 50 nm thick gold film is coated on the surface of TFBG using magnetron sputtering,which can effectively excite SPR.the probe nucleic acid is functionalized with sulfhydryl groups,and the probe nucleic acid is immobilized using Au-S covalent bond.The target nucleic acid is signal-enhanced with gold nanoparticles of 30 nm particle size,which increases the refractive index perturbation.When the target nucleic acid binds to the probe nucleic acid on the fiber surface,the refractive index of the SPR surface excited by the gold film changes strongly due to the modification of the gold nanoparticles,resulting in a significant increase in the sensitivity of the sensor.The experimental results showed that the lower detection limit of the sensor reached 1 p M and the sensitivity was 1.32 d B/lg(n M)when the target nucleic acid concentration was in the range of 1 p M-100 n M,which greatly increased the sensitivity and lower detection limit of the sensor.A linear detection range of five orders of magnitude is achieved.