Page 148 - IJB-10-2

International Journal of Bioprinting dECM bioink for in vitro disease modeling

required. The suitable physical treatment methods and on the type of detergent used. 118,119 Therefore, the type of
precautions for different tissue types are summarized in detergent for decellularization should be selected based
Table 2. on the target tissue type and the need to eliminate cellular
component.
3.2. Chemical treatment
The principle of chemical treatment in decellularization Enzymatic methods are used specifically to remove
lies in dissolving various intracellular and extracellular membrane surface allergens and cellular components (e.g.,
connections and destroying cellular membranes, a DNA, ribonucleic acid (RNA)). Examples of enzymes that
step instrumental for the elimination of nuclear and can be used for decellularization include nucleases, lipase
cellular components. 101,114 In this section, we introduce proteases, and alpha-galactosidase. 37,91,120 Nucleases can
representative solutions for decellularization, including disconnect ribonucleotide or deoxyribonucleotide chains
ionic/nonionic detergents, enzymes, and acids/bases. to make fractions that could then be washed away with
detergents or solutions. Proteases (e.g., trypsin) break
Detergents for decellularization can be categorized peptide bonds in proteins and destroy the microstructure
into ionic and nonionic detergents. The histological of native tissue, thereby allowing decellularization
features of decellularized tissues are strongly affected solution to permeate the tissue’s ultrastructure. The strong
by the type of detergent. 101,115 Ionic detergents, penetration effect of proteases underpins the success of
such as sodium dodecyl sulfate (SDS) and sodium the primary stage of decellularization; however, prolonged
deoxycholate, solubilize cell membranes and remove treatment induces protein loss, which decreases yield.
cellular components. These detergents are effective in Alpha-galactosidase can be additionally used for cleaving
the clearance of cytoplasmic components but can also alpha-gal epitopes—a range of representative antigenic
damage essential ECM proteins, such as collagen and carbohydrate molecules in mammalian tissue—that are
glycosaminoglycans (GAGs). By contrast, nonionic capable of inducing xenorejection in human transplants
detergents, such as Triton X-100, disrupt lipidic and inflammatory response in human-derived immune
interactions on cell membranes, including lipid–protein cells with immunoglobulin G (IgG).
and lipid–lipid interactions. 115,116 They are relatively Acid and base solutions can be utilized to hydrolyze the
gentle compared to ionic detergents; therefore, they cellular membrane and dissolve the cytoplasm, supporting
can be applied to thin and soft tissues. However, they the cleavage of nuclear components (e.g., DNA, RNA) in
may also disrupt the fibrous matrix network because of cells. 121,122 Furthermore, these solutions can sterilize dECMs
disconnection of the protein–lipid network. Therefore, by lysing microorganisms during the fabrication process.
nonionic and ionic detergents can be used together in Examples of acids used in decellularization include peracetic,
compensatory methods for preserving proteins and acetic, and sulfuric acids; these three acids are widely used for
preventing their denaturation. decellularization to eliminate cellular membranes and cell
The properties of the decellularized tissues can differ organelles. On the other hand, base solutions disassemble
depending on the detergent type. For example, a nonionic extracellular biomolecules and remove cellular components
detergent-treated decellularized urinary bladder matrix between ECM structures; however, they cut off the fibril
retains its fibrous network, whereas an ionic detergent- structures of fibrous proteins, inducing a transmutation of
treated one will contain an irregular fraction of the protein the mechanical properties of the ECMs.
network. However, the double-stranded deoxyribonucleic Collectively, a proper combination of chemical
acid (DNA) fraction was higher under nonionic conditions decellularization processes, including detergent-based,
than after being exposed to ionic detergent treatment. enzymatic, and acid–base decellularization approaches,
117
Conversely, in the case of eye tissue, decellularized corneal is necessary for eliminating cellular components while
hydrogels have different light transmittances, depending preserving essential proteins. Furthermore, treatment

Table 2. Physical treatments for decellularization and corresponding caveats for different tissue types

Physical treatment Applicable tissues Caveats
Chopping into small pieces Brain, lung, skin, kidney Obstruction to slurry formation due to small pieces
Freeze–thaw cycles Adipose tissues, lung, cornea Incomplete isolation of cellular component
Hydrostatic pressurization Cardiac tissue, vessel, bone Not suitable for soft tissue due to aggressive destruction of ECM structure
Mechanical agitation Brain, adipose tissue, skin Low-agitation RPM for soft tissue; high agitation RPM for hard tissue
Abbreviations: ECM, extracellular matrix; RPM, revolutions per minute.

Volume 10 Issue 2 (2024) 140 doi: 10.36922/ijb.1970