(191f) Effects of Flexibility and Ionic Strength on Membrane Filtration of Poly(dT60) Single-Stranded DNA

Certain unique features inherent to membrane filtration technology offer several advantages for a variety of applications. Microfiltration (MF) and ultrafiltration (UF) membranes are commonly employed in the food processing, biotechnology, pharmaceutical, and water/wastewater treatment industries. Membrane filtration of flexible particles has sparked a renewed interest in DNA purification in pharmaceutical companies and filamentous virus filtration in water treatment plants. The ability of flexible particles to adopt conformations and enter membrane pores influences their filterability. Understanding the effects of mechanical flexibility on the rejection coefficient is crucial for designing and implementing of membrane separation. The main objective of this study is to obtain quantitative data on the transmission of single-stranded DNA (ssDNA) -which is designed for DNA therapeutics- through ultrafiltration membrane by considering the factors that govern the transmission of ssDNA through membrane pores. The effects of flexibility, transmembrane pressure (TMP), solution ionic strength, and membrane pore size on the rejection coefficient were investigated using track-etched polycarbonate ultrafiltration membrane in a stirred cell set-up. To characterize flexibility of DNA, Fluorescence Recovery After Photobleaching was integrated with Worm Like Chain polymer model to determine the persistence length. The results demonstrate that increasing TMP results in decreasing the rejection coefficient due to the ability of DNA to deform and pass through the pores easier in higher pressure. In addition, studying the effects of solution ionic strength shows the electrostatic interactions between the same charged DNA and membrane increase DNA rejection. Results generated from this study will be important for the optimal design of micro- and ultrafiltration systems for water and wastewater treatment and DNA purification in the biotechnological and pharmaceutical sectors.