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International Journal of Bioprinting AI for sustainable bioprinting

bioink into droplets. Inkjet printing is cost-effective for advancing bioprinting technologies while adhering to
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and widely available but faces challenges such as cell eco-friendly principles.
damage from heat or sound, inconsistent droplet size, and These sustainable hydrogels can be broadly categorized
nozzle clogging. 24 based on their origin and composition, including natural
Extrusion-based bioprinters use mechanical or hydrogels, derived from renewable biopolymers, and
pneumatic systems to deposit continuous bioink recycled hydrogels, made from repurposed polymers
filaments with high precision across x-, y-, and z-axes. engineered for reusability. 42,43
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This method accommodates a wide range of bioink 2.2.1. Biopolymers
viscosities, supporting structural integrity with higher Biopolymers, which are derived from natural plants,
viscosities or promoting cell viability with lower ones. 26,27 microbes, and other organisms, are more sustainable than
It excels in printing bioinks with varying cell densities and synthetic polymers. Hydrogels made from biopolymers
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mechanical properties. 28,29 are also inherently biocompatible and biodegradable,
Laser-assisted bioprinting employs laser-induced mimicking the extracellular matrix to promote cell
forward transfer to deposit bioinks with cell-level attachment and proliferation. However, their mechanical
precision. 30,31 A laser pulse vaporizes the metal film or properties often require enhancement through chemical
bioink layers, creating bubbles that propel droplets onto modifications or blending with other materials to meet the
the substrate. This technique offers exceptional patterning structural demands of bioprinting.
accuracy but is limited by low flow rates, high costs, Common biopolymers used for bioprinting include
metallic residues, and small print sizes, restricting its use alginate, collagen, and gelatin. Alginate is a natural, water-
for larger tissue or organ fabrication. 31 soluble material primarily derived from brown seaweed
and bacteria. It has been used successfully for maintaining
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Stereolithography bioprinting uses photopolymeriza-
tion to solidify bioink layer-by-layer with ultraviolet (UV) a chondrogenic phenotype of chondrocytes and enhancing
Its ionic crosslinking property
neocartilage formation.
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or visible light. 32,33 A light source selectively cures bioink in facilitates printing of stable structures, contributing to
precise patterns to form complex three-dimensional (3D) its widespread use in bioprinting. Collagen is the main
structures. As an entire layer is solidified simultaneously structural protein in the articular cartilage and meniscus
with the light projection, this layer-by-layer process can extracellular matrix, and can be isolated from numerous
often increase printing speeds. However, its reliance on biological tissues, retaining key signalling, adhesive, and
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light-sensitive materials and the potential cytotoxicity of other biochemical cues. Gelatin is a water-soluble and
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unpolymerized residues may pose challenges. biodegradable polypeptide produced through collagen
hydrolysis. It has been extensively integrated with natural
2.2. Sustainable hydrogels for bioprinting
Hydrogels stand out as bioink materials and are becoming or synthetic hydrogels to enhance the biological properties
of hydrogel composites.
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indispensable in bioprinting due to their high-water
content, biocompatibility, and ability to mimic the 2.2.2. Recycled/upcycled polymers
extracellular matrix, supporting cell adhesion, proliferation, Recycled or upcycled hydrogels offer another avenue
and differentiation. 2,35,36 Traditional hydrogels often pose for sustainability. These materials not only reduce
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environmental challenges, including resource-intensive environmental waste but also align with circular economy
production and limited recyclability. Sustainable hydrogels principles by repurposing byproducts into functional
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are therefore becoming a focal point in bioprinting biomaterials. These hydrogels prioritize resource
due to their potential to address both functional and efficiency by enabling reuse through chemical or physical
environmental challenges associated with conventional modifications, such as phase separation or crosslinking,
materials. 37–39 These hydrogels are specifically designed retaining functionality across bioprinting cycles. 42,51
to meet the rigorous demands of bioprinting, such as Recent advances in hydrogel design have introduced
biocompatibility and biodegradability, while maintaining recyclable and upcycled polymers that support sustainable
environmental responsibility. Unlike traditional materials bioprinting by reducing material waste and enabling
that may rely on finite resources or involve energy-intensive multiple reuse cycles. Charlet et al. developed recyclable
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production processes, sustainable hydrogels emphasize double-network granular hydrogels with a disulfide-
minimal environmental impact by utilizing renewable or based network that allows selective degradation and
recycled materials. 40,41 This dual focus on functionality microgel recovery while preserving printability. Xu et al.
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and sustainability makes them an essential component created phase-separated supramolecular hydrogels with

Volume 11 Issue 4 (2025) 136 doi: 10.36922/IJB025170164