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International Journal of Bioprinting DNA-functionalized hyaluronic acid bioink

strategies, incorporating stem cells, utilizing advanced hydrogels offer unique programmability due to Watson–
engineering techniques, and creating scaffold designs are Crick base pairing, allowing the creation of precisely
among the techniques aimed at creating biostructures that tailored structures, adjustable mechanical properties, 30,31
are optimally conducive to cartilage regeneration. Among functional and targeted molecular recognition
4-6
these approaches, three-dimensional (3D) bioprinting has motifs, 28,32,33 stimuli responsiveness, 29,34-35 and exceptional
emerged as a potent tool, enabling precise manipulation biocompatibility. 36 The substantial transformation
of the spatial arrangement of cells, biomaterials, 10-12 and undergone by DNA-functionalized hydrogels is marked
7-9
bioactive cues 13-15 within three dimensions, thus emulating by the integration of DNA molecules as crosslinkers
the intricate structure of natural tissues. Considering the or functional components and their release with
distinctive tissue architecture of articular cartilage, such programmable, versatile, and responsive characteristics,
as low cell density and lack of vasculature, much emphasis making them well-suited for applications in bioprinting
is being placed on the careful selection of polymeric and tissue engineering. Initially, oligonucleotides were
biomaterials for cartilage tissue engineering, among which covalently attached to vinyl polymers, enabling self-
hyaluronic acid (HA)—a pivotal polysaccharide constituent assembly via complementary base pairing. Subsequent
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of the cartilage ECM and synovial fluid—has gained advancements incorporated DNA as crosslinkers, leading
prominence. 16-18 HA offers exceptional biocompatibility, to smart hydrogels. Notable milestones also include the
biodegradability, and low immunogenicity, playing a crucial development of a supramolecular peptide-DNA hydrogel,
role in maintaining cartilage structural integrity through capable of retaining shape and preserving cell viability, for
water retention and interactions with aggrecan and type II 3D bioprinting. Another innovation is represented by a
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collagen. Moreover, HA supplementation in patients with stimuli-responsive G-quadruplex-crosslinked pNIPAM
19
degenerative osteoarthritis promotes the production and hydrogel capable of reversible transitions. In 2021,
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retention of matrix components, contributing to cartilage DNA aptamers were employed to functionalize bioink
homeostasis. 20-22 Although HA-based hydrogels possess for 3D-printing cell-specific scaffold, which was utilized
appealing bioactive properties, they still have limitations to promote cartilage formation. A recent development
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in recapitulating tunable mechanical properties, stimuli involves a dynamic DNA-crosslinked matrix formed using
responsiveness, and flexibility in ligands’ adhesion akin to a synthetic DNA library-based hydrogel with ultra-high-
those of native tissues. molecular-weight polymers. This technology allows
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Regenerating cartilage tissue is a complex biological precise control over viscoelasticity, thermodynamics, and
process involving intricate interactions between cells kinetics, mimicking living tissue properties. Although
and bioactive factors within the matrix. The extracellular research on DNA-functionalized bioinks is in its early
matrix (ECM) plays a pivotal role in the cellular stages, these materials show great potential in constructing
microenvironment, encompassing organized, anisotropic, ideal artificial ECMs, enabling the formation of artificial
and dynamic structures that deliver essential physical cartilage tissues in vitro and facilitating advanced tissue
and chemical cues through interactions with cells. 23-25 regeneration in vivo. This review outlines the characteristics
Constructing 3D structures that closely mimic the natural and functional mechanisms of DNA sequence moieties,
ECM is essential for cartilage tissue regeneration. The including reversible DNA linkages, reconfigurable DNA
ideal HA-based bioink should possess tunable physical architectures, DNA plasmid, and targeted DNA aptamers,
and chemical properties, resembling the elastic modulus that are ideal for functionalizing HA hydrogels to create
and dynamic characteristics that respond to changes in dynamic bioinks for cartilage tissue engineering (Figure
the cellular metabolic microenvironment. Additionally, 1). With special emphasis, this review describes the
adhesive ligands, similar to those in the native ECM, should current state of strategies used to functionalize hydrogels
be incorporated into HA-based hydrogels to recognize and with DNA molecules, and exclusive advances of DNA-
interact with cell for desired biological functions. functionalized HA hydrogels as dynamic and smart
bioinks for engineering cartilage tissue. Although DNA-
DNA, traditionally known for its role in storing,
replicating, and transmitting genetic information within functionalized bioinks are in their infancy, this review
article aims to provide directions for guiding insightful
cells, has emerged as a versatile, non-genetic biomaterial research studies in this field.
for constructing or functionalizing hydrogels. 26,27 Notably,
certain well-designed DNA hydrogels, such as those driven 2. Action of DNA moieties
by DNAzyme catalysis, light, or magnetism, could
28
26
29
convert chemical energy, magnetic energy, or light energy 2.1. DNA as a crosslinker
into mechanical energy, and dynamically modulate the The intrinsic properties of DNA in encoding sequences
morphology and properties of the hydrogel network. DNA and its highly accurate structural assembly are keys to
Volume 10 Issue 2 (2024) 27 doi: 10.36922/ijb.1814