Hydrocolloid Inks for 3D Printing of Porous Hydrogels

Abstract

A new methodology is presented for generating hydrocolloid inks, emulsions of hydrogel precursor solutions with mineral oil, for solid freeform fabrication of porous hydrogel scaffolds. These hydrocolloid inks exhibit viscoplastic behavior and rapid photopolymerization that permit high fidelity printing of complex geometries. Hydrocolloid inks based on poly(ethylene glycol) diacrylate are utilized to fabricate custom scaffolds using open source 3D printing software and customized paste extruder with cure‐on‐dispense capabilities. Scaffolds exhibit a hierarchical porosity from the microscale emulsion templated pores to the macroscale lattice structure and geometry programmed into the printing process. The extensibility of this system is also demonstrated by creating hydrocolloid inks from a range of natural hydrogel solutions including cellulose, gelatin, alginate, and hyaluronic acid. Unlike other methods of modulating hydrogel rheology to increase printability, these versatile hydrocolloid inks enable high fidelity printing of hydrogels without relying on high polymer concentrations or complex polymerization mechanisms.

3D-Printable and Enzymatically Active Composite Materials Based on Hydrogel-Filled High Internal Phase Emulsions

“…Yield stress is an essential predictor of printability, especially for structures involving overhangs, as it substantially determines the bridging and shape retention capabilities of the material after extrusion (Sears et al, 2019 ). While the aqueous phase volume fraction and the surfactant concentration in the organic phase were found to strongly influence the yield stress, the monomer concentration in the aqueous phase had a minor effect ( Figure 4 ).…”

“…Applying a force above the yield stress initiates the flow of the material (Foudazi et al, 2015 ). This property makes HIPEs ideal candidates for extrusion-based 3D printing (Sears et al, 2016 , 2019 ). The external phase of HIPEs can be polymerized creating so-called polyHIPEs, a monolithic and porous polymer scaffold with void sizes typically in the range of one to several hundred micrometers (Hainey et al, 1991 ; Sergienko et al, 2002 ; Silverstein, 2017 ) and interconnecting pores between the voids (Silverstein, 2017 ).…”

“…The external phase of HIPEs can be polymerized creating so-called polyHIPEs, a monolithic and porous polymer scaffold with void sizes typically in the range of one to several hundred micrometers (Hainey et al, 1991 ; Sergienko et al, 2002 ; Silverstein, 2017 ) and interconnecting pores between the voids (Silverstein, 2017 ). There are two approaches toward formulating low-viscosity hydrogel precursor solutions as printable HIPE-based inks: Using oil-in-water HIPEs with a polymerizable external phase (Sears et al, 2019 ) or using water-in-oil HIPEs with both phases being polymerizable (Gitli and Silverstein, 2008 , 2011 ; Kovačič et al, 2011 ). The first approach yields a hydrogel filled with droplets of liquid oil, while the second approach yields a typical open-cell polyHIPE scaffold filled with hydrogel.…”

Bactericidal activity of 3D-printed hydrogel dressing loaded with gallium maltolate

“…Minimum inhibitory and bactericidal concentrations of GaM were determined to validate its use as an antimicrobial agent. Poly(ethylene glycol)-diacrylate (PEGDA) hydrogel dressings were then fabricated by 3D-printing hydrocolloid inks into a hydrogel dressing with the hierarchical porosity 45 . PEGDA was selected as the initial hydrogel chemistry due to its well-established biocompatibility, high water absorption, tunable mechanical properties, and photopolymerization which is amenable to our cure-on-dispense printing 46,47 .…”

“…These features make PEGDA a better candidate for these wound dressings than poly (vinyl alcohol) (PVA), which is frequently used in wound dressings and wound management systems 48 . Although PEGDA was selected for this initial study, we have previously demonstrated the versatility in generating hydrocolloid inks from a variety of hydrogel chemistries 45 . We hypothesized that the ability to control hydrogel properties, emulsion variables, and dressing geometry will allow for the development of a tunable dressing with a potential to improve wound moisture balance.…”