Viscoelastic ink for direct writing of hydrogel structures
A viscoelastic ink for direct writing of hydrogel structures includes a long chain polymer and a photopolymerizable moiety, which may be a photopolymerizable monomer or a photopolymerizable group attached to the long chain polymer. The ink may also include a crosslinking agent, a photoinitiator, and water. The long chain polymer is present at a concentration greater than a critical overlap concentration c* of the long chain polymer in the ink.
1. A viscoelastic ink for direct writing of hydrogel structures, the ink comprising:
a polymer;
a photopolymerizable moiety;
a photoinitiator; and
water,
wherein the polymer comprises poly(hyaluronic acid) (pHA), methacrylated hyaluronic acid or a blend of the two and is present at a concentration of about 5 wt. % or greater in the ink.
2. The ink of claim 1 , wherein the photopolymerizable moiety is selected from the group consisting of: a photopolymerizable monomer; and a photopolymerizable group attached to the polymer.
3. A method for forming a hydrogel scaffold, the method comprising:
forming an ink comprising a polymer and a photopolymerizable moiety, the polymer comprising poly(hyaluronic acid) (pHA), methacrylated hyaluronic acid or a blend of the two and being present at a concentration of about 5 wt. % or greater in the ink;
extruding the ink through a micronozzle to form an extruded filament;
photopolymerizing the extruded filament; and
depositing the extruded filament in a pattern on a substrate to form a hydrogel scaffold,
wherein the ink comprises a first viscosity at a low shear rate of about 0.1 s −1 and a second viscosity during the extrusion, the second viscosity being at least about an order of magnitude lower than the first viscosity.
4. The method of claim 3 , wherein the second viscosity is about 20 Pa·s or less.
5. The method of claim 3 , wherein the photopolymerization of the extruded filament occurs prior to depositing the extruded filament on the substrate.
6. The method of claim 3 , wherein the photopolymerization of the extruded filament occurs after depositing the extruded filament on the substrate.
7. The method of claim 3 , further comprising, after the photopolymerization, chemically treating the hydrogel scaffold to render the scaffold compliant for tissue growth.
8. The method of claim 7 , wherein chemically treating the scaffold comprises immersing the scaffold in a polylysine solution.
9. The method of claim 3 , wherein the concentration of the polymer is between about 10 wt. % and about 50 wt. %.
10. The method of claim 3 , wherein the photopolymerizable moiety comprises a photopolymerizable monomer present at a concentration of between about 25 wt. % and 55 wt. %.
11. The method of claim 3 , wherein the photopolymerizable moiety comprises a photopolymerizable group attached to the polymer.
12. The method of claim 3 , wherein, after photopolymerization, the extruded filament comprises a physically entangled polymer network and a chemically crosslinked polymer network.
13. The method of claim 3 , wherein, after photopolymerization, the extruded filament comprises a chemically crosslinked polymer network with no physically entangled polymer chains.
14. The ink of claim 1 , wherein the ink further comprises polyethylene glycol diacrylate (PEGDA).
15. The ink of claim 14 , wherein the PEGDA is present at a concentration in the ink of up to about 10 wt. %.
16. The ink of claim 15 , wherein the concentration of the pHA, the methacrylated hyaluronic acid, or said blend of the two is 10 wt. % and the concentration of the PEGDA is 8 wt. %.
17. The method of claim 3 , wherein the ink further comprises polyethylene glycol diacrylate (PEGDA).
18. The method of claim 16 , wherein the PEGDA is present at a concentration in the ink of up to about 10 wt. %.
19. The method of claim 18 , wherein the concentration of the pHA, the methacrylated hyaluronic acid, or said blend of the two is 10 wt. % and the concentration of the PEGDA is 8 wt. %.