Freeform inkjet printing of cellular structures with bifurcations

Abstract

Organ printing offers a great potential for the freeform layer-by-layer fabrication of three-dimensional (3D) living organs using cellular spheroids or bioinks as building blocks. Vascularization is often identified as a main technological barrier for building 3D organs. As such, the fabrication of 3D biological vascular trees is of great importance for the overall feasibility of the envisioned organ printing approach. In this study, vascular-like cellular structures are fabricated using a liquid support-based inkjet printing approach, which utilizes a calcium chloride solution as both a cross-linking agent and support material. This solution enables the freeform printing of spanning and overhang features by providing a buoyant force. A heuristic approach is implemented to compensate for the axially-varying deformation of horizontal tubular structures to achieve a uniform diameter along their axial directions. Vascular-like structures with both horizontal and vertical bifurcations have been successfully printed from sodium alginate only as well as mouse fibroblast-based alginate bioinks. The post-printing fibroblast cell viability of printed cellular tubes was found to be above 90% even after a 24 h incubation, considering the control effect.

Study of extrudability and standoff distance effect during nanoclay-enabled direct printing

“…As the internal scaffold material during extrusion, Laponite XLG is added to prepare the NIPAAm-Laponite nanocomposite hydrogel precursor to investigate the improvement of the bioink extrudability. For comparison, high-concentration NaAlg, a natural polysaccharide widely used for biorelated applications [6,7,9,10,18], is selected as a benchmark bioink material herein. In summary, four biocompatible materials (NIPAAm, Laponite, NIPAAm-Laponite, and NaAlg) are extruded through a transparent glass nozzle to study their extrudability, and the velocity field distribution is measured to evaluate the effects of nanoclay on the extrudability.…”

A comprehensive review on droplet-based bioprinting: Past, present and future

“…A C C E P T E D ACCEPTED MANUSCRIPT 11 fabrication of complex 3D tissue constructs, similar to PIJ studies [11,60], are lacking. Overall, microvalve bioprinters require low-range of pneumatic pressure compare to that of PIJ bioprinters and hence they are less prone cell injury and damage [46].…”

“…At the same time, single nozzle piezoelectric printheads, such as MicroFab printheads, offer a greater control over the droplet generation (number of droplets) and the droplet placement, and are more suitable for fabricating complex 3D tissue constructs. However, small secondary droplets, known as satellite droplets [86], often M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 14 accompany the primary droplets affecting the bioprinting resolution [60]. In addition, printheads are prone to clogging if the bioink viscosity is high.…”

“…As a result, the surface tension at the nozzle orifice is overcome and a droplet of the bioink is ejected [58]. Overall, studies on PIJ bioprinting technology have thus far investigated the feasibility and possibility of fabricating 3D tissue constructs [9,11,59,60]. For example, The tissue construct comprising alginate and NIH3T3 cells was fabricated by a single nozzle PIJ bioprinter.…”

“…For example, The tissue construct comprising alginate and NIH3T3 cells was fabricated by a single nozzle PIJ bioprinter. Further, some studies optimized process parameters, including the bioink constituents [61], piezoelectric element actuation modes (pull-push and push-pull) [62], and voltage pulse characteristics (amplitude, rise and fall times, dwell time, echo time, and frequency) [11,60], to improve process efficiency. Furthermore, few other studies attempted to improve process reliability [63] and control the M A N U S C R I P T…”