3D Printable Gelatin Methacryloyl (GelMA)‐Dextran Aqueous Two‐Phase System with Tunable Pores Structure and Size Enables Physiological Behavior of Embedded Cells In Vitro

Abstract

The restricted porosity of most hydrogels established for in vitro 3D tissue engineering applications limits embedded cells with regard to their physiological spreading, proliferation, and migration behavior. To overcome these confines, porous hydrogels derived from aqueous two‐phase systems (ATPS) are an interesting alternative. However, while developing hydrogels with trapped pores is widespread, the design of bicontinuous hydrogels is still challenging. Herein, an ATPS consisting of photo‐crosslinkable gelatin methacryloyl (GelMA) and dextran is presented. The phase behavior, monophasic or biphasic, is tuned via the pH and dextran concentration. This, in turn, allows the formation of hydrogels with three distinct microstructures: homogenous nonporous, regular disconnected‐pores, and bicontinuous with interconnected‐pores. The pore size of the latter two hydrogels can be tuned from ≈4 to 100 µm. Cytocompatibility of the generated ATPS hydrogels is confirmed by testing the viability of stromal and tumor cells. Their distribution and growth pattern are cell‐type specific but are also strongly defined by the microstructure of the hydrogel. Finally, it is demonstrated that the unique porous structure is sustained when processing the bicontinuous system by inkjet and microextrusion techniques. The proposed ATPS hydrogels hold great potential for 3D tissue engineering applications due to their unique tunable interconnected porosity.

Structuring gelatin methacryloyl – dextran hydrogels and microgels under shear

“…S1, ESI †). 58 We have previously shown that phase separation occurs between pH 5.1 and pH 3.6, therefore above and below the IEP of GelMA, which highlights the influence of the protein charge density on the phase separation process, as shown in (Fig. 2A).…”

“…During phase inversion, the system consisting of dextran droplets dispersed in the GelMA rich-phase coexists with GelMA droplets dispersed in the dextran phase. 58 Although the origin of the formation of a multiple emulsion is still unknown and is beyond the scope of this work, it could be related to some intrinsic properties of GelMA, near the IEP. For instance, the self-association of the modified gelatin molecules in the absence of charge repulsion may affect the random coil conformation.…”

“…2A). In our previous study, 58 by varying the concentration of the dextran, bicontinuous, or D/G emulsion, systems were obtained, which led after UV curing of the GelMA rich-phase to interconnected or discontinuous pores, respectively. Moreover, by fine-tuning the pH in the pH range of phase separation, we found that pH affects the microstructure of the resulting hydrogels, i.e., the length scale of the pores or the formation of multiple w/w/w emulsions.…”

“…We used the same GelMA batch synthesized elsewhere. 58 The degree of methacrylation was determined by 1 H NMR and is 75%.…”

Block Polyelectrolyte Additives That Modulate the Viscoelasticity and Enhance the Printability of Gelatin Inks at Physiological Temperatures

“…We note that all GelMA/bPE inks were prepared in Dulbecco’s phosphate-buffered saline (DPBS), maintaining pH = 7.4, which lies within the isoelectric point ( pI ) of native gelatin type A (7 < pI < 9) . While gelatin and GelMA are both polyampholytes containing carboxylic acid and amino groups, the modification of gelatin into GelMA, pursued by methacrylation of the amino and hydroxyl groups on the gelatin backbone, shifts the pI to values approaching 4–5 and changes the availability of ionizable groups. , The pI and charge density of GelMA are, therefore, expected to depend on its degree of functionalization (DoF). Here, a particular concern is whether interactions between charged GelMA (above its pI ) and bPEs lead to the complexation of GelMA with bPE and/or whether GelMA influences the complexation-driven self-assembly of the oppositely charged bPEs, leading to an inhomogeneous microstructure (flocculation and phase separation) within the GelMA/bPE inks.…”