Optimizing on-chip concentration of DNA molecules against a nanoslit barrier

On-chip concentration method for deoxyribonucleic acid (DNA) molecules is preconcentrating DNA molecules before analyses using nanometer-sized structures formed in a microchannel and is effective in improving the sensitivity in DNA analyses using microfluidic devices. Although accurate and predictive theoretical models of concentration profile and concentration factor in on-chip concentration can be used for designing nanostructures and optimizing conditions for concentration, there has been few studies on models. In our previous study, we presented a method of on-chip concentration of DNA molecules using a nanoslit, which is a smaller gap than the diameter of random-coiled DNA molecules. This method is based on the principle of an entropic trap, and we achieved DNA concentration by controlling the applied voltage. In this study, we developed theoretical models of concentration profile and concentration factor in on-chip concentration for DNA molecules using a nanoslit. We conducted concentration experiments of lambda DNA (λ DNA) using our fabricated chip device with a 25-nm nanoslit. The theoretical results of our models were in good agreement with these experimental results. Based on our theoretical models, we determined the optimal applied voltage to be 0.95 V for maximizing the concentration factor in λ DNA concentration by using our chip device.