Rheological Behavior of Responsive DNA Hydrogels

Abstract

Dynamic rheological measurements performed during the solution cross-linking of DNA (about 2000 base pairs long) at a concentration of 9.3% w/v show formation of strong to weak DNA hydrogels depending on the concentration of the cross-linker ethylene glycol diglycidyl ether (EGDE). At a cross-linker content of 10 wt % or above (with respect to DNA), the elastic modulus G′ of DNA hydrogels is more than 2 orders of magnitude larger than the viscous modulus G″, and both moduli are essentially independent of frequency over the range 10−2−101 Hz. The value obtained for G′ (103 Pa) is of the same order of magnitude as the elastic modulus for chemical gels or cross-linked biopolymer gels. At lower cross-linker contents (below 10 wt %), weak DNA hydrogels exhibiting frequency-dependent moduli were obtained. Thermal behavior of DNA gels and DNA solutions was investigated by heating the samples above the DNA melting temperature (87.5 °C) and subsequently cooling down to 25 °C. At high cross-linker contents, no sign...