Page 268 - IJB-9-2

International Journal of Bioprinting Bioprinting of β-islet-like constructs

pancreas or pancreatic islets from human or animal classified 3D bioprinting approaches within the general
sources, has always been a viable option to restore active technology field of 3D printing into different categories
insulin secretion in T1D [48–50] . Allograft transplantation based on standard document ISO/ASTM 52900:2015-12
has limitations because of the shortage of pancreatic for additive manufacturing techniques, material jetting, vat
tissue donors. The transplantation of xenogeneic islets photopolymerization, and material extrusion (Figure 2B
has often been studied to overcome donor scarcity. Islet and Table 2).
tissue from different species has been explored. Porcine
pancreatic islets have been addressed because of their 3.1. Material jetting printing
insulin structural similarities with human ones and other Since its inception, 3D material jetting printers have
reasons. Immune rejection after transplantation is one of evolved to print various materials and continuously
the major challenges in this issue. The encapsulation of increase resolution, which, when it comes to inkjet, refers
β-islets with biocompatible polymers has been developed to the droplet size itself . The droplets are measured in
[67]
to attenuate the complications of immunosuppressive the picoliter to nanoliter range in volume and contain
agents. This encapsulation can supply physical hindrance the biological medium desired for the 3D construct [68,69] .
to transplanted islets and prevent immune rejection by the Based on the mentioned classification, in addition to the
recipients . One possible solution to the donor shortage methods including piezoelectric/thermal inkjet, acoustic
[51]
is the generation of β-cells or islet-like tissues from human wave jet, and electrohydrodynamic jet, which is regulated
MSCs [52,53] , human embryonic stem cells (hESCs) [54–56] and by controlling droplets based on the nozzle function, the
induced pluripotent stem cells (iPSCs) (Figure 1C) [57,58] . laser-assisted bioprinting (LAB) or laser-induced forward
Directed cell differentiation and xenograft models alone transfer (LIFT) technique is belonged in the material
cannot solve the lack of donors, the three-dimensional (3D) jetting bioprinting category also . The piezoelectric
[66]
structure is also necessary. A functional artificial pancreas jetting relies on signals translated to vibrations within the
that resembles the original tissue can become a reality with printer head. The vibrations break the medium into little
3D tissue bioprinting, a revolutionary development in droplets ready for printing . Meanwhile, the thermal
[70]
recent years. This technology can provide everything that inkjet dispenses droplets by increasing the temperature
may be needed, even for clinical use. However, choosing of the heating element to approximately 200°C, causing a
the right printing technology and using the right cells and bubble that pushes the bioink out from the printer head.
scaffolds can significantly influence the results. Despite the high temperature, the heat has (theoretically)
little impact on the viability of the cells within the bioink .
[71]
3. 3D Bioprinting Instead, in practice, the energy is dispersed as bubbles,
with little to no heat energy ever reaching the cells or the
In the context of tissue engineering and regenerative hydrogel itself, which is mostly true, whereas acoustic wave
medicine, the terms biofabrication and bioprinting, jetting utilizes acoustic energy to create droplets , and in
[72]
which indicate the integration or participation of biology electrohydrodynamic jetting, droplets are formed based
with other fields of science, are frequently mentioned. on electric voltage. LIFT is a form of printing that does not
Biofabrication is defined as “the automated generation require direct contact with the print surface. It works by
of biologically functional products with a structural propelling hydrogel droplets containing suspended cells onto
organization from living cells, bioactive molecules, a growth surface. The method requires a laser transparent
biomaterials, cell aggregates such as microtissues, print ribbon and a receiving substrate. There are two layers
hybrid cell-material constructs through bioprinting or within the print ribbon for propelling . A sacrificial layer
[73]
bioassembly” . Bioprinting technology is an innovative is lost during the process, and a material layer is meant to
[59]
process in advanced tissue engineering that allows the be a viable postprint. The sacrificial layer absorbs the laser
layer-by-layer arrangement of a wide array of cell types, energy and evaporates, and through the expansive power of
biomaterials, and bioactive factors in precise order . This evaporation, the material transfer layer is ejected onto the
[60]
emerging technology has introduced promising prospects substrate. The amount of projected material is controlled
in regenerative medicine to simulate the native tissue by the laser energy profile. To lower the kinetic energy by
environment for fabricating clinically applicable live tissues the propulsion, the substrate is coated with an additional
and in vitro 3D models for screening therapeutics [61,62] . layer of hydrogel. LIFT is the only printing approach that
Bioprinter cartridges contain a combination of various offers direct visualization of cells both before and after
types of cells in hydrogel biomaterials as scaffold printing. Unlike other inkjet printing methods, which use
precursors, which are actually called bioinks [63–65] . a nozzle, LIFT does not need it and can thus print various
Although different classifications have been described substances that would otherwise clog the nozzle. Hakobyan
for different types of bioprinting methods, Lee et al. et al. have generated a 3D pancreatic cell spheroid which
[66]
[74]
Volume 9 Issue 2 (2023) 260 http://doi.org/10.18063/ijb.v9i2.665