| Summary: | 碩士 === 國立陽明大學 === 生物醫學工程學系 === 103 === Presenting minute amouts of lipopolysaccharides (LPS) in blood can stimulate the secretion of active cytokines by cell, which results in toxic effects such as fever or low blood pressure and may even cause sepsis shock with high mortality. Many studies manifested that polymyxin B (PMB) molecules can effectively detoxify LPS. However, due to the toxicity of the PMB molecule, it is necessary to immobilize the molecule for its application as a binding agent in removing LPS molecule from blood. In this work, a zwitterionic poly(carboxybetaine methacrylate) (polyCBMA) biomometic material was employed to create a unique coating with an ultralow fouling background for the immobilization of PMB molecule, enabling the sensitive and specific detection of LPS molecules in blood plasma. Gold slides were first modified using self-assemble monolayer (SAM) with a bromine atom. PolyCBMA was then grafted from the Br-SAM substrates using the atom-transfer radical polymerization (ATRP) method. PMB was immobilized on pCBMA using EDC/NHS. Fourier transform infrared spectroscopy (FTIR) was used to analyze the compositions of the modified surfaces. Ellipsometry and SPR were used to measure the adsorption of proteins and LPS molecules on these surfaces.
The results of FTIR and contact angle analysis demonstrated that the pCBMA and PMB molecules were successfully coated on the gold substrate. It has been show that by properly control the proportion of the ethanol/methanol-to-water ratio, one is able to increase the thickness of the pCBMA surface film. The coated film is highly hydrophilic and exhibits an optimum thickness for its anti-fouling property. Film thickness higher or lower than the optimum value will both cause an increase in nonspecific protein adsorption. PMB immobilized on a pCBMA substrate not only improves its resistance to the adsorption of plasma proteins but also increase its binding capacity to LPS. It is also shown that the CBMA side chain can be degraded in acid or alkali solutions, which in consequence can cause the detachment of the immobilized PMB molecule. Nevertheless, the pCBMA- PMB film is stable for up to 7 days in a solution of pH=7.4.
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