Generalizing hydrogel microparticles into a new class of bioinks for extrusion bioprinting

Abstract

Hydrogel microparticles (HMPs) are an emerging bioink that can allow three-dimensional (3D) printing of most soft biomaterials by improving physical support and maintaining biological functions. However, the mechanisms of HMP jamming within printing nozzles and yielding to flow remain underexplored. Here, we present an in-depth investigation via both experimental and computational methods on the HMP dissipation process during printing as a result of (i) external resistance from the printing apparatus and (ii) internal physicochemical properties of HMPs. In general, a small syringe opening, large or polydisperse size of HMPs, and less deformable HMPs induce high resistance and closer HMP packing, which improves printing fidelity and stability due to increased interparticle adhesion. However, smooth extrusion and preserving viability of encapsulated cells require low resistance during printing, which is associated with less shear stress. These findings can be used to improve printability of HMPs and facilitate their broader use in 3D bioprinting.

3D Printing of Cell‐Laden Microgel‐Based Biphasic Bioink with Heterogeneous Microenvironment for Biomedical Applications

“…For JM bioink, the excess water in the interstitial spaces was extruded first, and microgels were packed closer before yielding to flow as previously reported. [23,24] We observed a clogging problem and the discontinuous extrusion of JM bioink during printing (Figure S9c, Supporting Information), which was consistent with previous report; [31] whereas, for MB bioink, microgels (red fluorescent) were evenly extruded with interstitial hydrogel precursor (green fluorescent) due to less resistance (Figure 3a(ii) and Movie S1, Supporting Information). Further, we optimized the 3D printing parameters including the printing speed at 1 mm s −1 and extrusion rate at 0.35 µL s −1 before printing complex structures (Figure S10, Supporting Information).…”

Microcarriers in application for cartilage tissue engineering: Recent progress and challenges

“…Overjamming: Due to more resistance, HMPs were not extruded until rupture of the beads. Reproduced with permission [ 302 ]. Copyright 2021, the Authors.…”

“…5 G). The research results of Xin et al revealed a large enough opening was required for smooth printing of MCs bioinks, but the shape and size of the syringe and nozzle as well as the size and polydispersity of the HMPs must also be considered [ 302 ]. Furthermore, the jamming process within the syringes also affected the printing stability and cytocompatibility.…”

Mechanical characterization of soft microparticles prepared by droplet microfluidics

“…We note that the wall resistance can be controlled through the selection of appropriate nozzle opening size compared to the microparticles and that the mechanical properties of hydrogel microparticles also affect the overall printability. For example, Xin et al 123 recently investigated the effect of elastic modulus of PEG‐norbornene hydrogel microparticles by using different MW PEG molecules (PEG5, PEG10, and PEG20). For the same nozzle opening and particle size, microparticles with the highest modulus (PEG5) experience more stress and exhibit higher flow resistance compared to other microparticles, resulting in higher packing.…”