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International Journal of Bioprinting 3D bioprinting of nerve guidance conduits

best performance in facilitating directed axonal extension PCL. Ouyang et al. developed a seamless axial NGC
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and SC migration in vitro due to the combined effects of the consisting of biocomposite collagen/PLGA nanofibers by
topological cues provided by the aligned nanofibers and electrospinning and evaluated the ability of the conduit
the biochemical cues retained in the porcine decellularized to support SC proliferation and axonal growth both in
nerve matrix hydrogel. Consistent results were obtained in vitro and in vivo. The aligned NSCs were significantly
animal experiments with the fabricated NGCs, confirming superior to those composed of randomly aligned collagen/
that PLA is generally a promising approach for NTE and PLGA fibers in facilitating regeneration and functional
the treatment and diagnosis of PNI. restoration and were nearly as effective as autologous grafts.
Moreover, the collagen/PLGA conduits were mechanically
3.2.2. Polycaprolactone strong enough to suture severed nerve endings and resist
PCL is a biodegradable aliphatic polyester characterized by collapse in vivo, remaining structurally intact for at least
a low melting point, ease of processing, high mechanical 3 months postoperatively. Namhongsa et al. deposited
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strength, good biodegradability, and miscibility with polypyridine particles on 3D-printed poly(l-lactic acid-
various other polymers. However, due to its high co-ε-caprolactone)/PLGA conduits to change the electrical
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plasticity, the physical, chemical, mechanical, and conductivity of the conduit surface. Studies have shown
biological properties of PCL can be improved by modifying that PLGA-based conduits degrade faster and are more
functional groups or combining it with other materials suitable for short-gap nerve injuries, and vice versa. By
(e.g., synthetic polymers, metallic materials, etc.). PCL- optimizing the structural and surface modifications of the
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based NGCs support the adhesion and proliferation of SCs conduits, these materials can provide a favorable option
and olfactory sheath cells without causing severe swelling for enhancing cellular biocompatibility. The controlled
that may locally compress the nerve. Zhu et al. employed degradation properties of PLGA are also a valuable factor
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electrospinning techniques to fabricate a PCL-based NGC for achieving multi-phase release of neurotrophic factors.
featuring directionally aligned fibers complemented by a For instance, Lackington et al. developed a PLGA
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concentration-gradient NGF coating on its surface. This microparticle with encapsulated NGF and glial-derived
innovative design facilitated the directional guidance of neurotrophic factor. The factors are sequentially released
DRG neurons toward the high NGF-concentrated region into the nerve regeneration microenvironment over 28
and successfully repaired a 15 mm sciatic nerve defect days, promoting nerve repair. However, PLGA generally
in rats. Chen et al. tested the mechanical properties exhibits poor hydrophilicity, and its degradation products
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of 3D-printed PCL conduits with maximum tensile create an acidic microenvironment, often resulting in
strength and modulus of elasticity of 21.2 and 142.5 MPa, limited bioactivity.
respectively—values significantly higher than those of
native nerves. This enhanced strength offers greater ease 3.2.4. Polyethylene glycol
of handling and suturing during surgical procedures. Qian PEG is a linear polyether compound with strong mechanical
et al. innovatively invented an LBL casting method and degradation properties that can encapsulate cells, good
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for the fabrication of NGCs, utilizing either single-layer hydrophilicity, and water absorption. However, due to its
graphene or multi-layer graphene with PCL. Results biological inertness and poor oxidative stability, it may
showed that the higher the number of layers of graphene, cause cell death during ultraviolet cross-linking. Therefore,
the lower the conductivity achieved (8.92 × 10 S/cm for it is typically combined with other biomaterials to improve
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a single-layer graphene/PCL conduit, 6.37 × 10 S/cm its performance.
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for a multi-layer graphene/PCL conduit). All the above- 114
mentioned studies demonstrate that NGCs made from Berkovitch et al. sought to evaluate hydrogel assemblies
PCL have great potential for future research and clinical PEG-fibrinogen (Fib) in different formulations for NGCs.
applications. In addition to this, even with synthetic Three PEG-Fib hydrogels were prepared and tested:
polymers, hybridization with other materials is still an compliant PEG-Fib, rigid PEG-Fib, and micropatterned
essential way to enhance the performance of conduits. PEG-Fib with microchannels. All three compositions were
implanted into 8 and 12 mm rat sciatic nerve defect models
3.2.3. Poly(lactic-co-glycolic acid) to verify their effectiveness in repairing PNI. Rigid PEG-
PLGA is a functional polymeric organic compound formed Fib constructs containing 40 mg/mL of PEG diacrylate
by the random polymerization of two monomers, lactic acid (PEGDA) were shown to be better at promoting complete
and hydroxyacetic acid, with a controlled biodegradation bridging at the injury site compared to fibronectin/
rate and good cell adhesion. Although the degradation PEGDA. The semi-synthetic compositions were superior
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rate of PLGA reduces with increasing lactic acid content, to fibronectin and fibronectin/PE-DA in bridging nerve
it remains significantly higher than that of PLA and injuries. In addition, PEG conduits promoted homeostasis

Volume 11 Issue 4 (2025) 46 doi: 10.36922/IJB025140120