Inverse Thermogelation of Aqueous Triblock Copolymer Solutions into Macroporous Shear-Thinning 3D Printable Inks

Amphiphilic block copolymers that undergo (reversible) physical gelation in aqueous media are of great interest in different areas including drug delivery, tissue engineering, regenerative medicine and biofabrication. We investigated a small library of ABA-type triblock copolymers comprising poly(2-methyl-2-oxazoline) as the hydrophilic shell A and different aromatic poly(2-oxazoline)s and poly(2-oxazine)s cores B in aqueous solution at different concentrations and temperatures. Interestingly, aqueous solutions of poly(2-methyl-2-oxazoline)-block-poly(2-phenyl-2-oxazine)-block-poly(2-methyl-2-oxazoline) (PMeOx-b-PPheOzi-b-PMeOx) undergo inverse thermogelation below a critical temperature. The viscoelastic properties of the resulting gel can be conveniently tailored by the concentration and the polymer composition. Storage moduli of up to 110 kPa could be obtained while the material remains shear-thinning and retains rapid self-healing properties. We demonstrate 3D-printing of excellently defined and shape persistent 24-layered scaffolds at different aqueous concentrations to highlight its application potential e.g. in the research area of biofabrication. A mesoporous microstructure, which is stable throughout the printing process, could be confirmed via cryo-SEM analysis. The absence of cytotoxicity even at very high concentrations opens wide range of different applications for this first-in-class material in the field of biomaterials.