Controlling the responsive behavior of genetically engineered block copolymer hydrogels through molecular architecture

• Main Author: Guhr, Karen Iuga
• Language: ENG
• Published: ScholarWorks@UMass Amherst 2000
• Subjects: Polymers|Organic chemistry|Biomedical research
• Online Access: https://scholarworks.umass.edu/dissertations/AAI9960756

Precise control over the responsive behavior of hydrogels is crucial for medical applications of these materials. To better understand how pH-triggered gelation and materials properties of the resultant gels can be controlled, a series of multiblock copolymers has been prepared by genetic engineering. The advantage of genetically engineered materials is that they are well-defined, monodisperse materials. In particular, the exact length and sequence of each block of a multiblock copolymer can be controlled. In this system triggerable gelation is based on the self-association of the naturally occurring Fos leucine zipper domain to form crosslinks in response to changes in pH. A polyelectrolyte domain (C) is interspersed with the leucine zipper domains (F) and renders the network water-soluble. Three block copolymers, consisting of three (L2FC3), five (L2FC5), and seven (L2FC7) blocks, respectively, were prepared via bacterial protein expression. The responsive behavior of these materials with respect to pH and temperature was characterized using circular dichroism and rolling ball viscometry. The different architectures of these block copolymers play a role in modulating the response to pH. L2FC5 and L2FC7 exhibit a stronger pH-response as compared to L2FC3, but no difference was observed between the two longer block copolymers.