| A new nanochannel electroporation (NEP) was developed recently in our laboratory to realize dosage-controlled delivery. The nanochannel was fabricated by using large DNA molecules as building blocks in a new DNA combing and imprinting process. Large DNA was stretched to generate the nanowire array that was then used to fabricate the nanochannel array. During the electroporation, transfection agents including DNA molecules were electrophoretically driven through microchannel, nanochannel, and finally into individual cells. Therefore, DNA dynamics and cell electroporation are two main components in the process of NEP. In this dissertation, we study the DNA stretching dynamics in DNA combing, DNA electrophoretic dynamics in the microchannel and nanochannel, cell electroporation mechanism in NEP, and the detection of membrane poration.;Computational analyses and simulations along with experimental observations and measurements were performed to investigate micro/nanofluidics induced DNA dynamics and cell electroporation. Brownian dynamics simulation with the bead-spring model was combined with the dewetting free surface flow computation to study the DNA stretching dynamics on a micropattern. The droplet formation during the dewtting creates the flow pattern standing for DNA stretching and immobilization. The dependence of electrophoretic (EP) mobility on the DNA instantaneous conformation was studied in DNA microfluidic electrophoresis that was set up in a converging microchannel. From experimental observations, DNA instantaneous EP motilities were determined by tracking DNA center-of-mass locations and correlated with their conformations. It was found that the mobility increases with the stretching and the degree of enhancement is conformation dependent. The experimental findings were explained by a theoretical model based on electrohydrodynamic interactions. Due to the use of electric pulses in nanochannel electroporation, DNA electrophoretic transport through the nanochannel under pulses was studied computationally using the Brownian dynamics simulation with the bead-rod model. Because of the chain recoiling between electric pulses, distinguished single DNA transport processes were found between long and short pulses even though the total pulse length were the same. For each individual DNA, degree of entrance was affected by its conformation and geometrical span over the electric field. Multiple-chain dynamics was also studied by considering the intermolecular interaction. The effect of multi-chain dynamics is stronger and the chain passing rate is reduced under short pulses.;The mechanism of NEP was clarified by computational analysis. High applying voltage in NEP can generate much higher electrophoretic driving force without damaging the cell because of high electrical resistance and small channel cross section. A pore in the size of nanochannel could be created by considering the pore formation. Thus, large transfection agents could be delivered into the cell in NEP. However, the pore formation on the cell cannot be observed directly in the experiment. We proposed to use electrochemical impedance spectroscopy to detect the membrane poration. This idea was tested on the tethered lipid bilayer membrane where the pores were created by reducing the lipid concentration. The measured impedance spectra were verified by finite element analysis. A correlation between membrane morphology and impedance spectrum was established that provides the knowledge base for the detection of cell membrane poration. |
