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International Journal of Bioprinting Bioprinted organ-on-a-chip with biomaterials

between batches, weak physical properties, low Polydimethylsiloxane (PDMS) is an elastic and non-
resolution, and the potential for a xeno-immune response. degradable material prepared by blending a curing agent
Addressing these limitations is crucial to fully realizing and an elastomer base. It is suitable for fabricating
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the potential of dECM as a biomaterial. Recent efforts tubular instruments or microfluidic platforms and can
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have been directed at minimizing non-uniformity in ECM be reversibly bonded to various materials such as plastic
composition between batches by automating dECM bioink or glass. Therefore, PDMS can serve as the outer wall
manufacturing and standardizing the manufacturing of a platform to contain hydrogel or culture medium.
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process. Moreover, hybrid dECM bioink, incorporating Due to these properties, PDMS has found extensive
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photocurable materials, has been developed and used for applications in various fields, including micropumps,
3D bioprinting, offering good physical properties due to dressings, and optical systems. In particular, it has been
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the inclusion of photocurable materials. 59 utilized in the production of various medical devices, such
as particulate blood analogs mimicking red blood cells
2.1.2. Synthetic biomaterials and microvalves or blood vessel analogs with excellent
Synthetic biomaterials exhibit tailorable mechanical elasticity. 69,70 The PDMS-covered platform is well-suited
and biodegradable properties, excellent printability, for cell culture requiring oxygen enrichment due to its
and consistent quality. Despite lacking bioactivity, good oxygen permeability. After curing, PDMS exhibits
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synthetic biomaterials typically possess superior physical a low shrinkage rate, high tensile modulus, and high
properties and rigidity compared to natural biomaterials. thermal conductivity. Additionally, PDMS offers optical
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Consequently, they find application as a robust cell support transparency and the ability to easily track target particles,
framework in organs-on-a-chip. Additionally, when rendering it valuable for organ-on-a-chip applications
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modified to resist degradation, synthetic biomaterials are requiring these characteristics. Despite being widely
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well-suited for fabricating the housing of an organ-on-a- used for organ-on-a-chip manufacturing owing to its low
chip. Moreover, the combination of synthetic biomaterials cost and ease of production, incorporating PDMS into 3D
with 3D bioprinting technology enables the realization of bioprinting poses challenges. Shrestha et al. produced a
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various organs in organs-on-a-chip. Below, we discuss lung-on-a-chip containing lung epithelial cells by treating
several synthetic biomaterials widely used in organ-on-a- PDMS with oxygen plasma and trichlorosilane and
chip fabrication through 3D bioprinting. applying a final coating with an ECM. However, the digital
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Polycaprolactone (PCL) is a United States Food and light processing (DLP) method used for 3D bioprinting
Drug Administration (USFDA)-approved biomaterials can generate oligomers and monomers that interfere with
widely used in biomedicine owing to its low degradation PDMS polymerization; thus, careful selection of the 3D
rate and high biocompatibility. With a lower melting point bioprinting method is necessary when using PDMS. There
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than other synthetic biomaterials, PCL solidifies rapidly are also concerns that cytotoxic uncrosslinked oligomers
upon ejection from a nozzle. This characteristic makes it may be generated in PDMS, and cell attachment may
suitable for constructing frameworks that directly interact be difficult due to the low hydrophilicity of the PDMS
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with cells and support cell structures. Accordingly, PCL surface. Furthermore, its low surface energy makes
is typically used for organ-on-a-chip fabrication through deposition on other materials challenging. To overcome
3D bioprinting. However, its use for cell encapsulation these difficulties in cell adhesion, PDMS has been coated
is limited as it can directly stress cells owing to its high with other hydrogels such as laminin, fibronectin, and
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transition temperature. 63 collagen. By combining these hydrogels with PDMS, an
organ-on-a-chip more similar to the microenvironment of
Pluronic F-127 (PF-127) is a copolymer biomaterial an actual organ can be manufactured using various cells.
composed of hydrophobic poly(propylene oxide) (PPO) In addition, controlling properties such as mechanical
between two hydrophilic poly(ethylene oxide) (PEO) properties and hydrophilicity is easier, enabling the
layers. PF-127 exhibits a thermoreversible gelation production of more complex and diverse organ-on-a-chip
behavior, transitioning from an insoluble to a soluble state designs. However, some hydrogels may require a long
in aqueous solution based on concentration. Additionally, time to crosslink and may exhibit severe shrinkage. Thus,
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PF-127 can be easily removed as a liquid at temperatures careful consideration is needed in selecting an appropriate
below 4°C. Conversely, above 4°C, PF-127 forms micelles hydrogel to coat the PDMS based on the specific design
and transforms into a viscous gel. Leveraging these requirements of the organ-on-a-chip.
characteristics for creating sacrificial components, PF-
127 is used in the manufacturing of blood vessel mimics 2.2. Three-dimensional bioprinting methods
or in fabricating perfusable proximal tubules requiring an As a method for fabricating an organ-on-a-chip, 3D
empty hole. 65 bioprinting—a technique involving the creation of a 3D

Volume 10 Issue 1 (2024) 25 https://doi.org/10.36922/ijb.1972