Collagen type II dynamics and assembly in anisotropic porous polyacrylamide hydrogels.
Tsai Mario M, Adedeji Adediwura Deborah AD, Suresh Sneha S, Morozova Svetlana S
Inspired by liquid crystallinity and hierarchical organization in natural systems, we fabricate anisotropic polyacrylamide (PAAm) networks by templating polymerization around disodium cromoglycate (DSCG) liquid crystal phases. These anisotropic porous networks act as scaffolds that guide collagen fiber alignment, recapitulating key aspects of extracellular matrix (ECM) organization in biological tissues. The pore morphology and characteristic length scales are tuned by varying the modulus of the PAAm network, while polymerization at different temperatures induces distinct DSCG phases and corresponding pore anisotropies. Network architecture is characterized by confocal microscopy. The hydrogels are subsequently swollen in 1 mg mL-1 collagen solutions prepared in 0.012 M HCl, followed by fibril formation triggered in a neutral pH buffer. Collagen localization within the pore walls and voids is visualized, and collagen dynamics are quantified using confocal microscopy and differential dynamic microscopy (DDM), respectively. As the gel concentration increases, collagen mobility is progressively slowed and the distribution within the gel depends on the morphology and the local acrylamide concentration in pores. In networks polymerized at 30 °C, collagen localizes exclusively within the pore walls. In contrast, in gels polymerized at -20 °C collagen freely diffuses and assembles within the anisotropic pores, yielding highly aligned structures at higher collagen concentrations. Together, these results provide insight into self-assembly within crowded, elastic environments and establish a strategy for engineering biomimetic ECM scaffolds.