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International Journal of Bioprinting DNA-functionalized hyaluronic acid bioink

plasmids, resulting in the formation of recombinant of ATP in the hydrogel, thereby achieving fine control over
plasmids that can be introduced into host cells. This the mechanical properties of the hydrogel. Additionally,
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procedure requires the use of restriction enzymes to cleave aptamers can be conjugated into DNA hydrogels as
DNA at specific sites, followed by the application of ligases targeting recognition molecules to enable selective
to facilitate the fusion of DNA molecules. By harnessing binding and internalization of target cells by the DNA
these methodologies, researchers can construct plasmids nanohydrogels, thus achieving targeted gene delivery.
containing precise DNA sequences. The inherent capacity Cartilage ECM is characterized by its intricate
of plasmid DNA to carry and independently replicate structure and multifaceted functions, serving as a source of
foreign DNA sequences establishes it as a fundamental mechanical, chemical, and biological cues that orchestrate
tool in genetic engineering. In recent years, DNA plasmids cell behaviors such as proliferation, differentiation,
have been introduced into hydrogel materials for tissue migration, and tissue formation. Consequently, the
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regeneration applications. For example, Wang et al. properties of hydrogels, which act as synthetic ECMs, play
constructed two plasmids that encode mouse vascular a pivotal role in shaping cell functions during cartilage
endothelial growth factor (VEGF) and transforming regeneration. Mechanical properties hold particular
growth factor-β1 (TGF-β1), respectively. They combined significance in the context of cartilage regeneration, as
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these plasmids with arginine-modified chitosan (Arg-CS) this tissue must endure varying loads and directions.
to form Arg-CS/pDNA nanoparticles, which acted as gene Additionally, hydrogels possess the unique capacity
carriers. Next, they incorporated these nanoparticles into to emulate the recognition attributes of natural ECM,
a composite hydrogel prepared from N-carboxymethyl which facilitates selective recruitment or release of
chitosan (NCMC) and sodium alginate (SA), forming a cells and substances. Notably, the functionalization of
gene-activated matrix (GAM). This GAM could achieve hydrogels with DNA molecules allows them to mimic the
long-term and sustained gene release and expression in vitro characteristics of cartilage ECM, inducing differentiation
and in vivo. Kim et al. combined plasmid DNA (pDNA) of cells into chondrocytes and enhancing cartilage tissue
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encoding mouse bFGF gene, which is a growth factor that support. This can be achieved through the introduction of
can promote tissue regeneration, with polyethylenimine- reversible DNA crosslinking that enables the regulation of
grafted poly(ethylene glycol) (PEI-g-PEG) complex to hydrogel mechanical properties in a reversible or even self-
form a nanoparticle carrier that can protect pDNA from healing manner. 39,52 The incorporation of reconfigurable
degradation and enhance transfection efficiency. They DNA structures further enhances hydrogel responsiveness,
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further loaded the nanoparticles into a mixture hydrogel enabling adaptation to complex and dynamic
of alginate (ALG) and hyaluronic acid (HA), which can microenvironments and regulation of cell behaviors and
solidify under mild conditions and release pDNA complex fate. 56,57,59 By enhancing the recognition properties of
slowly (Figure 3d). hydrogels, DNA aptamers represent an additional avenue
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2.2.5. Aptamers for enabling the selective adsorption and release of target
Aptamers are oligonucleotide molecules with high affinity cells or molecules, thereby enhancing the efficiency and
and specificity that are obtained by systematic evolution quality of cartilage regeneration. 60
screening. They can interact with specific target molecules,
making hydrogels targeted and specific (Figure 3e). For 3. DNA-functionalized hyaluronic acid
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instance, the adenosine triphosphate (ATP) aptamer, hydrogels
whose 3D structure is designed to precisely match the In comparison to pure DNA hydrogels, hybrid DNA
molecular structure of ATP, can be integrated into the hydrogels offer a broader spectrum of applications. Hybrid
linker DNA to regulate the mechanical properties of the hydrogels constructed through DNA crosslinking not only
hydrogel. When ATP is present, it is recognized and bound retain the inherent biological functions of DNA but also
by the aptamer, causing a change in the 3D structure of preserve the structural integrity of hydrogels. The energy
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the aptamer and subsequently forming a stable framework necessary to break the bonds between complementary
composed of two stacked G-quartets. The formation of DNA base pairs is notably lower compared to the energy
this framework triggers a conformational change in the required for traditional polymer chains and crosslinking
aptamer-DNA, thereby altering the physical properties agents. The integration of customizable DNA into polymer
of the DNA hydrogel, such as its mechanical strength. As gel systems imparts a degree of structural control and
a result of the specific interaction between ATP and its property modulation. HA is a linear high-molecular-weight
corresponding aptamer, the mechanical strength of the polysaccharide comprising repeating disaccharide units
hydrogel increases from 204 Pa to 380 Pa. This regulatory composed of N-acetyl-D-glucosamine and D-glucuronide.
mechanism can be achieved by changing the concentration

Volume 10 Issue 2 (2024) 32 doi: 10.36922/ijb.1814