Usingin situ rheology to characterize the microstructure in photopolymerized polyacrylamide gels for DNA electrophoresis

Abstract

Photopolymerized cross-linked polyacrylamide hydrogels are attractive sieving matrix formulations for DNA electrophoresis owing to their rapid polymerization times and the potential to locally tailor the gel pore structure through spatial variation of illumination intensity. This capability is especially important in microfluidic systems, where photopolymerization allows gel matrices to be precisely positioned within complex microchannel networks. Separation performance is also directly related to the nanoscale gel pore structure, which is in turn strongly influenced by polymerization kinetics. Unfortunately, detailed studies of the interplay among polymerization kinetics, mechanical properties, and structural morphology are lacking in photopolymerized hydrogel systems. In this paper, we address this issue by performing a series of in situ dynamic small-amplitude oscillatory shear measurements during photopolymerization of cross-linked polyacrylamide electrophoresis gels to investigate the relationship between rheology and parameters associated with the gelation environment including UV intensity, monomer and cross-linker composition, and reaction temperature. In general, we find that the storage modulus G' increases with increasing initial monomer concentration, cross-linker concentration, and polymerization temperature. The steady-state value of G', however, exhibits a more complex dependence on UV intensity that varies with gel concentration. A simple model based on rubber elasticity theory is used to obtain estimates of the average gel pore size that are in surprisingly good agreement with corresponding data obtained from analysis of DNA electrophoretic mobility in gels cast under identical polymerization conditions.

Universal aspects of hydrogel gelation kinetics, percolation and viscoelasticity from PA-hydrogel rheology

“…Consequently, it is one of the most widely studied water soluble polymers [1][2][3][4][5], and much has been learned from studies of its gelation [6][7][8], sol-gel transition [9], degree of crosslinking [10], and large-strain deformation [11]. See Denisin and Pruitt [12] for a recent example of how varying the degree of crosslinking in PA affects its stiffness.…”

History and Applications of Hydrogels

“…Among these, mean gel pore size, pore size distribution and stiffness of the gel play a crucial role. In order to achieve improved separation performance in 2-D electrophoresis applications, it is therefore essential to understand the specific nature of the pore structure of the gel and the parameters through which this pore structure can be controlled and manipulated [91,92]. In particular, it is of great interest to investigate structure-property relation-ships of these hydrogels in the attempt to optimize their functional performance.…”

Photo-induced Polymerization and Degradation of Formulations Containing Photolabile Crosslinkers Monitored in a Rheometer

“…For example, the analysis of photopolymerization and photo-induced gelation [6][7][8] by using the rheometer were reported in recent years.…”