Page 58 - v11i4

International Journal of Bioprinting 3D bioprinting of nerve guidance conduits

Table 4. Advantages and disadvantages of three-dimensional bioprinting technologies
Three-dimensional bioprint- Advantages Disadvantages
ing technology
Stereolithography High resolution (~30 µm); ability to manufacture complex Requirement of additional post-processing steps to
structures cure the printed part, a time-consuming printing
process, and high material waste; photoinitiators may
be toxic
Digital light processing High resolutions (~25 µm); simultaneous cross-linking Limited selection of photopolymerizable biomaterial
within layers for fast production speeds; low viscosity resins, photoinitiators may be toxic, and the high price
materials; fast light curing capability of the printer
Extrusion printing Suitable for a wide range of materials; printability of Reduction in cell viability after extrusion; low
bioinks at high viscosity and cell density; low cost and resolution down to 200 µm
relatively simple printing process
Kenzan Fully functional biological nerve guidance conduits can Conduit size is vulnerable to change during fusion of
be constructed without the need for biopolymer solutions cell spheres, with low dimensional accuracy
or hydrogels, relying only on cells

compared to pure PU and exhibited proper enzymatic bioprinting system to fabricate NGCs with oriented and
degradation after 6 weeks, which is expected to last long continuous microstructures. The researchers fabricated
enough for effective nerve regeneration. Perez et al. NGCs with different inner diameters, wall thicknesses
145
modified a commercial SLA printer with a sterile system (Figure 7A-i), and microfibers (Figure 7A-ii), and tested
to produce clean, particle-free conduits and reduced the the effect of functionalized nerve conduits loaded with
laser diameter to increase its micromachining capability HDAC3-specific inhibitor (RGFP966) nanoparticles after
for the fabrication of complex conduit structures. Singh implantation into 10 mm nerve defects in rats. The results
et al. prepared hollow, multi-channel, and factor-filled showed that the nerve conduction velocity of the loaded
146
biodegradable NGCs using SLA (Figure 6D), which could group was 29.83 m/s, which was significantly higher than
bridge a 15 mm nerve injury gap in rats. It was shown that that of the unloaded group (23.49 m/s), demonstrating
the synthesized NGC was biocompatible and could provide the promoting effect of RGFP966 on functional recovery.
guidance for the migration and proliferation of nerve cells, Tao et al. used DLP to fabricate natural polymers and
154
which improved the rate of nerve regeneration. platelets into NGCs. The compression test showed that the
4.2. Digital light processing conduit had good mechanical properties and could recover
Similar to SLA technology, DLP uses digital light projection the printed structure after deformation with structural
to polymerize or cure the entire photoactive resin for each integrity to support peripheral nerve regeneration. In
layer, which in turn enables the layered fabrication of addition, enzymatic degradation studies have shown
147
3D structures. The main advantage of DLP over SLA is that the conduit could be degraded in vitro, eliminating
the rapid production of 3D structures. The laser source the requirement of a secondary surgical resection after
in SLA systems crosslinks the resin at each laser spot, implantation. As a light-curing technology, exposure time
148
whereas the introduction of digital micromirror devices is an important process parameter in the printing process.
155
in DLP promotes the rapid crosslinking of the entire Ye et al. explored the optimal exposure time for GelMA in
layer. Similar to SLA, c, such as a limited selection of the DLP preparation of multi-channel neural conduits. To
photopolymerizable biomaterial resins, strong odors avoid the potentially harmful effects of ultraviolet light, a
caused by the polymerization between acrylate groups and 405 nm visible light source was used to cure the biomaterial
photoinitiators, and higher resin waste, which increases ink. During printing, the size of the conduit was affected by
the cost of printed parts. 149–151 For DLP, the resolution the layer exposure time, light intensity, and layer thickness.
of the projector determines the accuracy of the print, Printability was analyzed by adjusting the layer exposure
which is currently up to 25 µm, allowing more detailed time while other printing parameters remained constant.
152
microstructures of NGCs to be printed. Numerous Conduits printed with shorter exposure times (<20 s)
scholars have used DLP to conduct experiments on (Figure 7B-i) exhibited poor mechanical properties and
rational NGC printing, and NGCs fabricated using DLP were easily deformed. In contrast, longer exposure times
have demonstrated their ability to support peripheral enhanced the mechanical strength (Figure 7B-iii), but
nerve regeneration. Xu et al. established a DLP 3D resulted in significant blockage at the base of the multi-
153

Volume 11 Issue 4 (2025) 50 doi: 10.36922/IJB025140120