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Thermoresponsive N‐alkoxyalkylacrylamide polymers as a sieving matrix for high‐resolution DNA separations on a microfluidic chip

In recent years, there has been an increasing demand for a wide range of DNA separations that require the development of materials to meet the needs of high resolution and high throughput. Here, we demonstrate the use of thermoresponsive N‐alkoxyalkylacrylamide polymers as a sieving matrix for DNA separations on a microfluidic chip. The viscosities of the N‐alkoxyalkylacrylamide polymers are more than an order of magnitude lower than that of a linear polyacrylamide (LPA) of corresponding molecular weight, allowing rapid loading of the microchip. At 25°C, N‐alkoxyalkylacrylamide polymers can provide improved DNA separations compared with LPA in terms of reduced separation time and increased separation efficiency, particularly for the larger DNA fragments. The improved separation efficiency in N‐alkoxyalkylacrylamide polymers is attributed to the peak widths increasing only slightly with DNA fragment size, while the peak widths increase appreciably above 150 bp using an LPA matrix. Upon elevating the temperature to 50°C, the increase in viscosity of the N‐alkoxyalkylacrylamide solutions is dependent upon their overall degree of hydrophobicity. The most hydrophobic polymers exhibit a lower critical solution temperature below 50°C, undergoing a coil‐to‐globule transition followed by chain aggregation. DNA separation efficiency at 50°C therefore decreases significantly with increasing hydrophobic character of the polymers, and no separations were possible with solutions with a lower critical solution temperature below 50°C. The work reported here demonstrates the potential for this class of polymers to be used for applications such as PCR product and RFLP sizing, and provides insight into the effect of polymer hydrophobicity on DNA separations.