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International Journal of Bioprinting dECM bioink for in vitro disease modeling

it will be necessary to attempt decellularization for various 2.4. Troubleshooting issues related to dECM bioink
organs that have not yet been developed and consider in 3D bioprinting
adjusting the decellularization process to ensure that the Compared to other biomaterials, dECM bioink provides
manufactured dECM bioink generates ECM with the same a tissue-specific microenvironment by preserving its own
components for each batch. 86 biochemical composition of native tissue. Despite that, the
dECM must be improved with regard to safety, mechanical
2.3.2. Usability as bioink for 3D bioprinting properties, and fabrication yield to develop safer and more
Three-dimensional bioprinting uses biological materials, sophisticated dECM bioink-based in vitro models for
including cells, as bioinks to create specific cell structures. drug screening and discovery. In this section, we discuss
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This technology enables the fabrication of structures with considerations for improving dECM bioink in the context
controlled biomechanical properties, including fine-tuned of safety and fabrication usability.
cells and biomaterials, thereby enabling the manufacture
of various in vitro models and implanted structures for 2.4.1. Immunogenicity of dECM bioink
tissue regeneration. Three-dimensional bioprinting Animal tissue is the most widely used source of dECM
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methods can be categorized into laser-assisted, inkjet, and bioink, encompassing porcine, bovine, and murine
extrusion-based bioprinting. Conventionally, extrusion- tissues. These animal-derived tissue sources are easy to
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based bioprinting has been widely used to fabricate layered acquire for experiments and produce sufficient quantities
structures with cells. In 3D bioprinting, the required and various types of dECMs; however, animal-related
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printing material is referred to as a bioink, which is a pathological factors, such as viruses, antigens, or bacteria,
polymer solution containing living cells. A bioink is are safety concerns in the dECM application with human
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primarily a hydrogel material that must have sufficient cells. For example, all mammalian tissues, except those of
mechanical properties to maintain the shape of its structure primates, have a carbohydrate antigen called the alpha-
after printing and spraying. 89 gal epitope on the cell surface, which induces immune
rejection and inflammation in human tissues. 91,92 In
Owing to the capability of dECMs to form tissue-
specific microenvironments, there have been even further addition, some animal-specific viruses are not known to
be safe in reaction with human cells. Porcine endogenous
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developments of dECM bioinks for various organs recently, retrovirus (PERV) is a porcine genome-encoded virus
and printability tests have been conducted to confirm that can infect human cells. Another concern regarding
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that the bioinks could be used for 3D bioprinting. The the immunogenicity of the dECM is the adverse effects
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dECM bioinks can serve as a support structure and cell of the residual detergent. The residual detergent can
delivery carrier in the printing process and should be destroy the intracellular microstructure and affect
compliant with 3D bioprinting in terms of mechanical the permeability of the adapted cell membrane in the
properties, printability, and biocompatibility. Moreover, dECM. Thus, if the immune cells that are employed in
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they can protect cells from external stimuli, such as shear the dECM are activated because of immunogenicity in
stress and temperature changes, that occur during the the dECM, the basal immune reaction elicited from the
printing process. Each dECM bioink preserves its ECM cells in vitro is not reflective of the health status; therefore,
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components and provides an organ-specific environment the unintended cytotoxic reactivity restricts the study
for organ-derived cells, improving biocompatibility and cell concerning a disease. 96,97 Therefore, the decellularization
function compared to those provided by other hydrogels, process should include proper immunogen removal for
such as collagen and hyaluronic acid. Additionally, the safe applications of dECM. However, if the immunogen
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dECM bioink can simulate the pathophysiological removal process is too violent, the dECM can lose its
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microenvironment better than other hydrogels. For protein composition and microstructure, affecting the
example, Kim et al. succeeded in fabricating a precise in tissue specificity. Therefore, it is necessary to discuss the
vitro model of diabetes via 3D bioprinting using a visceral reliable standard for immunogenicity lessening and the
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adipose tissue-derived dECM (vadECM) bioink. The similarity to the native tissue in the context of biochemical
vadECM bioink proved superior to other hydrogels in features. 98,99 The concern about the immunogenicity of
simulating diabetes. dECM can be traced to the regulatory issues stemming

Taken together, the complex tissue-specific composition from the approvals by US Food and Drug Administration
of the dECM bioink provides excellent biochemical (FDA). Currently, one of the FDA’s regulatory criteria for
function, biocompatibility, and a pathophysiological approving medical devices is a detection level of <0.5 EU/
environment. Therefore, it is widely used as an effective mL for endotoxins. Another criterion for immunogen
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bioink for the fabrication of various organ-mimicking removal is that the residual DNA level must be <50 ng/mg
models and disease models via 3D bioprinting. for dry products. In view of these criteria, production
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Volume 10 Issue 2 (2024) 138 doi: 10.36922/ijb.1970