Investigation And Application Of Boronic Acid Based Fiber-Optic Surface Plasmon Resonance Sensing Technology For Sugar And Derivative Measurement

Surface plasmon resonance(SPR)is a kind of electromagnetic wave caused by the interaction between the photons of incident light and free electrons of the metal.SPR sensing technique is sensitive to the external refractive index change.Compared with other sensing techniques,SPR sensors show many distinct advantages,such as high sensitivity,good signal stability,free from analytes pre-purification,real-time monitoring and electromagnetic immunity,which have been widely used in medical science,food safety,and environmental monitoring.Fiber-optic SPR sensors are portable and flexible devices combining both the advantages of optical fibers and traditional SPR sensors,their unique merits include small size,high cost effective,the ability for remote sensing,which have shown great potential applications in medical detection and environmental monitoring in recent years.Sugar is main energy source for organisms and also plays an important role in physiological activities.Various disease such as diabetes,iron deficiency anemia and cancer can be analyzed and diagnosed by detecting sugar or its derivatives.Boronic acid can selectively bind with different sugar and its derivatives and is widely used in glycoprotein detection,cancer cell monitoring,drug delivery.However,the related investigations of boronic acid application in fiber-optic SPR biosensing area are limited.In this thesis,to improve the limitation of sugar detection and extend the application of fiber-optic SPR biosensing,we integrate SPR sensing,fiber-optic devices,nanomaterials,molecular recognition technology together.Design and synthesis a variety of boronic acid recognition systems and then apply them in fiber-optic SPR biosensors,we conduct the measurement of the saccharide,glycoprotein and RNA with high sensitivity and selectivity.Our research works can be extended for applying fiber-optic SPR sensors in biochemical detection and disease diagnosis.Major research works are listed as follows:1.We modified boronic acid molecular and applied them on the surfaces of fiber-optic SPR sensors,which selectively realized the fructose detection in neutral condition.Usually,most commercial boronic acid molecules only can recognize and detect the saccharide in alkaline condition.However,in biological research,many biological samples need neutral analyzing environments.To solve this problem,we introduced an N atom near the B atom,the B-N interaction allow the boronic-acid modified fiber-optic sensor to detect the saccharide in neutral condition,which expends the application of boronic acid for small molecule detection.2.Through the extension of the alkyl chain in boronic acid molecular,we realize high-selectivity glycoprotein detection by using boronic acid modified fiber-optic SPR sensor.The long alkyl chain allows the boronic acid group binding with glycosylation sites inside the glycoprotein,which contribute to the sensitivity improvement for glycoprotein detection.We used it for concanavalin A(ConA)recognition,the detection limit was as low as 0.29 nM.Furthermore,we optimized the boronic acid functionalized sensing system.As an antifouling material,BSA can efficiently reduce non-specific adsorption over 85%.Using Ethanol/PBS solution(pH=3)to rinse the binding sensing surface,90%of the sensing surface can be regenerated.3.We apply boronic acid functionalized sensing technique on tilted fiber-optic Bragg grating(TFBG)based SPR sensors and extend the SPR biosensing technology to fiber-optic communication spectral band.We conduct the sensor calibrations in both wavelength modulation and intensity modulation on TFBG-SPR sensors,the refractive index sensitivities were achieved as 576.08 nm/RIU and 1792.5 dB/RIU respectively.Then,we use the TFBG-SPR sensor for ConA testing,the detection limit was 15.6 nM.Compared with multimode fiber-optic SPR sensors,TFBG-SPR sensors have with smaller size which own more potentials for vivo detection.4.Phenylboronic acid modified Au nanoparticles(PBA-AuNPs)were synthesized and developed as a signal enhancement method for miRNA(microRNA)reorganization by using fiber-optic SPR sensors.As a kind of non-coded sequence RNA,miRNA plays fundamental roles in regulating bio-activities.However,due to its small molecular weight and low concentration,it is hard for fiber-optic SPR sensor to recognize the miRNA directly.The basic unit of miRNA is ribonucleotide,which contain cis-diol in five carbon sugar.Therefore,the boronic acid can selectively bind with RNA through the cis-diol group.Furthermore,the sensing signal can be greatly enhanced by the existing of AuNPs.The detection limitation for miRNA was 2.7×10-13 M(0.27 pM).Combining the boronic acid enhancing technique with fiber-optic SPR sensor,we selectively differentiated RNA and DNA with different sequences.This PBA-AuNPs technique is universal and can be applied for other RNA sequence detection with further investigation.In this thesis,we designed and synthesized functional boronic acid molecules and applied them in multiple types of fiber-optic SPR sensors for saccharide,glycoprotein and single-stranded RNA detection.This work demonstrates its innovations for boronic acid functionalization and fiber-optic biosensing application,which is significant and valuable for many areas include saccharide analysis,medical care diagnosis and food inspection.