石英晶體微天平的實驗和模擬應用於抗體與抗原結合之親和力分析

Abstract

本論文首先對石英晶體微天平在氣相下的NaCl質量負載進行量測，將獲得的實驗值與Sauerbrey's Equation的值、使用有限元素分析軟體(Comsol Multiphysic)的模擬値互相比較，發現在200ng~ 2000ng時彼此間有相近的値。 接著在液相下，量測Human IgG1和Anti-Human IgG1的結合頻率變化，並算出它們之間的親和力。但因質量傳輸限制的影響，導致實驗値低估ka値、高估kd値，因此利用有限元素法做曲線耦合時，必須慢慢調高ka値，再調低kd値，並考慮Anti-Human IgG1在管路中前後端的濃度因為擴散而稀釋。所以當ka=3.48×104 M-1s-1、kd= 1.29×10-4 s-1和用時間控制濃度進行模擬時，獲得模擬曲 線與實驗曲線近似。 最後因為本實驗使用的石英晶體微天平受質量傳輸限制的影響，無法利用公式求出ka、kd與實際値相似的結果，因此提出改善的方法。首先將流道的尺寸大小縮為現有實驗儀器流道的千分之一(金電極反應面的直徑為3.4×10-4m、流速5.31×10-4 m/s、流道直徑7×10-4m、流道高0.6×10-4m、入口和出口直徑1×10-4m)，接著將金電極的直徑變小為1.7×10-4m，最後再將流速調高為2.12×10-2m/s(流量10ul/min)，則利用改善後的條件進行模擬，可求到與實際相似的ka値。

This work starts with the experiment measuring the frequency shift of the lowest transwave shear mode by additional mass of NaCl on the electrode in the gas phase by QCM (Quartz Crystal Microbalance). In addition, the experimental data are compared to the preditions by Sauerbrey's equation and finite element simulation using Comsol Multiphysics. The comparisons are consistent for the adding mass of NaCl from 200ng to 2000ng. The Human IgG1 and Anti-Human IgG1 interactions are measured in liquid phase and their affinities (the association constant ka and dissociation constant kd) are calculated to give ka=1.212×104M-1s-1 and kd=3.501×10-3s-1 because of the effect of mass transport. It is readily known that the experimenta1 ka and kd is lower than real ka and kd. So, in order to obtain the consistent transient response with the experiments, bigger ka and kd must be used in the finite element simulations. It is found that ka=3.48×104M-1s-1 and kd=1.29×10-4s-1 are adequate such that the curves of simulation is close to the curves of experiment. Because of the effect of mass transport, real ka can't be obtained correctly from the experimental curves. Some improvements are made. We change channel volume, electrode diameter and fluid velocity respectively. Then we can learn that the new model scales are electrode diameter=1.7×10-4m, channel diameter=7×10-4m, channel highness=0.6×10-4m, inlet and outlet diameter=1×10-4m and fluid velocity= 2.12×10-2m/s respectively. As a result, new model is adopted and make the ka of simulation similar to real ka.