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Sensitivity Enhancement of Functionalized MoS2 Based Plasmonic Biosensors for Detection of Pregnancy Associated Plasma Protein A2 (PAPP-A2) in Clinical Serum Samples
Surface plasmon resonance
本研究使用兩種方式製備官能化二硫化鉬晶片，分別為將草酸(Oxalic)及氯乙酸(MCA)兩種有機酸的羧基(-COOH)修飾至二硫化鉬表面，進行感測材料的優質化比較。其中氯乙酸修飾技術，主要是以氯原子佔據硫空缺，有較高的穩定性及結合率，有別於傳統的方法以硫醇直接吸附於硫空缺。利用XPS、FTIR、TEM、UPS和Zeta potential等方式成功證實羧基修飾至二硫化鉬表面，且於XPS的分析結果顯示，羧基在碳原素的含量佔24.4%，在氧原素中佔28.2%。在生物檢測方面，提出低注入量(20 μL)和低流速(6 μL/min)於牛血清白蛋白免疫法實驗，進行與傳統SPR晶片靈敏度比較，在氯乙酸修飾的官能化二硫化鉬晶片靈敏度提升2.35倍。在PAPP-A2重組蛋白的實驗，迴歸係數達到R2=0.99，而加入干擾物後並不影響靈敏度與線性值。於檢測臨床血清樣本之新型妊娠相關血漿蛋白(PAPP-A2)的實驗，將檢體稀釋至40,000倍(0.05 pg/mL)，仍可檢測到共振角位移量為0.96 mo，且線性迴歸係數可達到R2=0.958。
The advantages of surface plasmon resonance (SPR) biosensor includes high sensitivity, lable-free and real-time monitoring. The principle is the use of optical sensing interfacial refractive index changes associated with any affinity binding interaction between a biomolecule immobilized on a sensor surface. In this study, we propse a new sensing material, which modified the carboxyl acid groups (-COOH) with molybdenum disulfide (MoS2) to enhance the bio-interaction affinity, the work function and electric field propagation characteristics. Thereby improving the detection sensitivity. In this study, functionalized MoS2 chips (f-MoS2 chip) were prepared in two ways. The carboxyl acid groups (-COOH) of oxalic and chloroacetic acid (MCA) were modified to the surface of MoS2 to carry out the quality of the sensing material comparison. Which MCA modification technology, mainly chlorine atoms occupy sulfur vacancies, have a high stability and binding efficiency, different from the traditional method of thiol ligand modifications, in this instance, they yield physisorbed disulfides that are easily removed. The results of XPS analysis showed the content of carboxyl group was 24.4% in C1s and 28.2% in O1s, and f-MoS2 was confirmed by XPS, FTIR, TEM, TEM, UPS and Zeta potential. In the biological detection, low injection (20 μL) and low flow rate (6 μL / min) in bovine serum albumin (BSA) immunoaffinity detection were carried out to compare with traditional SPR chip sensitivity in the presence of f-MoS2 (MCA) chip sensitivity increased by 2.35 times. In the PAPP-A2 recombinant protein experiment, the R2=0.99, and after adding the interference does not affect the sensitivity and linearity. PAPP-A2 in clinical serum samples, the sample was diluted to 40000 times, and the SPR angle of PAPP-A2 at a concentration of about 0.05 pg/mL could still be detected, R2 = 0.958. We demonstrated that f-MoS2 chip has high sensitivity in the detection of clinical samples. PAPP-A2 has a high specificity and has the potential to become a new indicator protein for future diagnosis of pregnancy disorders, which is expected to be a screening protein for Down's syndrome, achieving rapid screening and high detection rates in the future.
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