| Summary: | 博士 === 國立中央大學 === 化學工程與材料工程研究所 === 98 === Biosensor is a device with the ability to detect an analyte of its biological component together with the physicochemical detector component. It consists of 2 parts: the sensitive biological recognizing element, and the transducer and/or detector element. In recent years, self-assembled monolayers (SAMs) have been widespread employed as bases of the biological recognizing elements to be immobilized onto sensor surface. SAMs are ordered molecular assemblies formed by the adsorption of active surfactant molecules on solid surface. The advantages are the ease for preparation and provided wide ranges of functional groups for immobilizing the biomolecular assemblies on different substrates. This makes SAMs inherently attractive for biosensor fabrication. This study concentrates on the functionalized SAMs on gold and glass (SiO2) surfaces for developing optical biosensors, surface plasmon resonance (SPR), guided mode resonance (GMR) and electrode sensor, and interdigitated electrode (IDE) biosensors.
The study of SPR investigated the effect of Lewis bases and salt concentrations with different pH values on the mechanism of glycated hemoglobin (HbA1c) and phenylboronic acid (PBA) interaction. The results of the interaction between HbA1c and phenylboronic acid exhibited the pH value is an important factor affecting HbA1c and PBA, forming the complex and Lewis bases. Lewis bases could change the stereo-structure of phenylboronic acid to form B(OH)3 and therefore would easily bind with saccharine. In addition, a linear response ranging from 0.43 to 3.49 μg/ml appeared in HbA1c, and the detection limit was 0.01 μg/ml.
The SPR study in this thesis was extended to the protein biosensor fabrication via protein–DNA conjugates. The ssDNA probe surface was built up by following the mixed self-assembled monolayers (mixed SAMs) method. The results represented that the protein-DNA conjugates were immobilized on the chip surface with a sequence complementary to the ssDNA on the surface via sequence specific hybridization. In addition, the chip had high specificities to human serum albumin (HSA). The results demonstrated that the DNA chip was successfully converted into protein chip. This strategy would be useful and could be extensively employed for more versatile applications, such as drug screening, biosensors, and medical diagnostics.
In the GMR research, GMR served as an optical filter which reflects specific wavelength in transmission light. GMR periodic waveguides produced sharp spectra when the illuminating wave matched to a leaky waveguide mode. Since the coupling range was typically small, these resonating elements exhibited high parametric sensitivity. They could thus be extremely responsive to small amounts of the change of biological molecules on chip interface. Recent efforts for improvement of resonant sensor had employed amplitude mode where the wavelength shift of the reflectance was measured directly. The purpose of this case study was to use GMR to provide a new method for investigating the interactions between the biomolecular. In this case, we presented a simple design of GMR for DNA and protein detection. The results demonstrated that it was successful to obtain the DNA hybridization by analysis of the surface wavelength peak shift using different DNA mass of 20 mer, 40 mer, and 60 mer. The study also stretched to immobilize the thrombin aptamer on GMR device for detecting the thrombin. The results also showed that the linear relationship of the concentrations of thrombin from 0.25μM to 1.5μM and the equilibrium association constant (Ka) is about 106 M-1.
The investigation of interdigitated electrode sensor for biosensing is based on the fact that many biochemical reactions in a solution produce changes in the electrical resistance. Impedance measurements would reflect the changes of the resistance with the biomolecular assemblies attached to the sensor surface. This study showed an interdigitated electrode sensor for detection of Human Serum Albumin (HSA). The blue dye Cibacron Blue F3GA (CB), with a high affinity for HSA, was used as a captor. Experimental results showed a linear trend in the concentrations of HSA from 0.1 mg/ml to 0.4 mg/ml.
In this research, we studied the SPR, GMR and IDE biosensors. The SPR and GMR could provide useful knowledge to understand the mechanism of biomolecular recognition. The impedance sensor, IDE, demonstrated a great potential for detection of specific sites on various biomolecular species.
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