Structuring of multiple parallel pectin gel filaments by applied shear

Structuring gelatin methacryloyl - dextran hydrogels and microgels under shear

Gelatin methacryloyl (GelMA) is a widely used semi-synthetic polymer for a variety of bioapplications. However, the development of versatile GelMA hydrogels requires tuning of their microstructure. Herein, we report the possibility of preparing hydrogels with various microstructures under shear from an aqueous two-phase system (ATPS) consisting of GelMA and dextran. The influence of an applied preshear on dextran/GelMA droplets and bicontinuous systems is investigated by rheology that allows the application of a constant shear and is immediately followed by in situ UV-curing of the GelMA-rich phase. The microstructure of the resulting hydrogels is examined by confocal laser scanning microscopy (CLSM). The results show that the GelMA string phase and GelMA hydrogels with aligned bands can be formed depending on the concentration of dextran and the applied preshear. The influence of the pH of the ATPS is investigated and demonstrates the formation of multiple emulsions upon decreasing the charge density of GelMA. The preshearing of multiple emulsions, following gelation, leads to the formation of porous GelMA microgels. The diversity of the formed structures highlights the application potential of preshearing ATPS in the development of functional soft materials.

Dynamic gelation of shear-induced filamentous domains for cellulose ether assemblies due to polyion complexation

Assemblies of carbohydrate polymers are important in a number of applications and improved methods for their fabrication are increasingly sought after. Herein, we report that an aqueous two-phase system of alginate (Alg) and hydroxypropyl cellulose with poly(methacrylic acid) graft chains (HPC-PMA) facilitated the assembly of Alg/HPC-PMA in both phases. Dynamically formed filamentous domains in a flow field were gelled by rapid complexation with cationic polyethyleneimine (PEI). The fabricated HPC-PMA gel filament morphologies can be switched between the bundled and dissociated gel filaments using a co-flow microfluidic device in response to the amount of supplied PEI crosslinker. Excess complexation of PEI contributes to the fabrication of cationic gel filaments; this contribution results in a dissociated structure due to electrostatic repulsion. In contrast, an appropriate amount of PEI resulted in a bundle structure. The proposed spinning method avoids the risk of nozzle clogging, and enables the one-step spinning of multiple gel filaments.