Simulation of Specific Capture of Bacteria By Molecular Imprinting Method Under Dielectrophoresis
Authors: Tamura Mamoru , Tokonami Shiho , Iida Takuya 
Published: February 2020

A structure of the target molecule can be transcribed into a surface of polymer film with molecular imprinting method. With use of the molecular imprinted films, a development of efficient molecular sensors has been reported. In addition, this method enables to create “bacterial imprinted film (BIF)” with a surface structure of target bacteria. It has been demonstrated that only target bacteria are specifically captured by BIF with the help of dielectrophoresis (DEP) even in a mixture liquid of various kinds of bacteria including the target ones and different ones with a similar shape. An applied research for a highly specific sensor for bacteria with use of BIF based on the DEP and a mass measurement by quartz crystal microbalance was also performed [1]. However, there remain still unresolved problems in a physical mechanism of specific capture. Therefore, in order to theoretically clarify the mechanism, we have performed the pioneering work on a computational simulation of behavior of bacteria under the DEP assuming a coarse-grained model of recognition mechanism.
As the assumption of the recognition mechanism, we consider the chemical structures (CSs) on a bacterial surface are also transcribed into the BIF, and they are specifically recognized by the imprinted site by defining as the molecular recognition site (MRS). Fig. 1 shows the considered model of the bacteria with CSs and the BIF with MRS. To calculate the DEP force, the general expression of force exerted on the electrically neutral matter by the oscillating electric field [2] is used. Previously, we simulated the stochastic behavior of nanoparticles under the light in time domain with Langevin equation [3] and in energy domain with Metropolis method [4]. Based on the latter method, we develop a novel method to simulate the stochastic behavior of bacteria under the DEP and the interaction at MRS, i.e. “Molecular recognition Metropolis method (MRMM)”.
We have performed simulations to clarify the specificity of BIF under DEP force. First, it has been confirmed that bacteria move randomly and do not enter the BIF without DEP force for the both models in Fig. 1. Remarkably, only after the DEP force is turned on, the bacteria can enter the BIF. In addition, we assume the DEP is turned off after that. In this case, bacteria <A> with CSs array corresponding to the imprinted MRS on BIF are captured continuously, while bacteria <B> with mismatched CSs array escape from BIF quickly. This tendency seems to show good agreement with the previous experimental report in Ref. [1]. If we investigate the detailed mechanism and determine the unknown parameters, the general guiding principles of specific capture in BIF would be developed.
By constructing our original theoretical method MRMM, we have simulated the specific recognition of bacteria by the BIF and confirmed the correspondence with experimental results. Moreover, the MRMM and obtained information will open the way to a guiding principle to design a highly sensitive biosensing devices based on specific capture of bacteria with BIF.
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Figure 1