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Materials Science in Additive Manufacturing Fibrous silk in biomedicine

enhanced the compressive modulus and stiffness nearly and extracellular matrix (ECM) production. Furthermore,
eightfold. Biochemical analyses showed increased DNA, in vivo experiments confirmed that CMAF scaffolds
sulfated glycosaminoglycan (1.5-fold), and collagen exhibited superior cartilage formation ability and evenly
(1.4 fold) content compared to pure SF solution scaffolds deposited specific ECM components.
(p<0.01). Furthermore, cartilage-specific gene markers,
such as collagen II, Sox-9, and aggrecan, were upregulated 4.3. Soft tissue regeneration: tendon and ligament
by approximately 1.5-fold. These findings suggest that the Tendons and ligaments are vital dense connective tissues
FS-enhanced material holds potential for cartilage tissue characterized by exceptional strength and toughness.
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engineering. Similarly, Kazemnejad et al. developed a Tendons, as extensions of muscle, connect muscles to
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chondrocyte-seeded scaffold. Subcutaneous implantation bones and are primarily composed of tightly packed
experiments in mice demonstrated that the scaffold collagen fibers surrounded by cells. Their primary
exhibited an appropriate in vivo degradation rate and function is to transmit muscle-generated forces to bones,
regeneration capacity. The chondrocyte-seeded scaffolds thereby enabling movement. Conversely, ligaments are
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effectively repaired most cartilage defects after 36 weeks, located between bones and surrounding joints, where
underscoring the potential for cartilage engineering. they enhance joint stability. Ligaments are composed of
Combining FS with hydrogels merges their intricate fibrous tissue that restricts the direction of joint
respective material and biological advantages, enhancing movement and absorbs mechanical shocks. Both tendons
cartilage repair scaffolds. Weitkamp et al. created a and ligaments can be damaged by leverage, excessive stress,
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porous 3D FS matrix embedded with chondrocytes, muscle contraction, joint activity, or trauma, causing joint
which was then immersed in a tyrosine-modified instability and abnormal movement. 125
hyaluronic hydrogel, enhancing cartilage induction and Altman et al. employed FS to fabricate artificial
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biomechanics. Mirahmadi et al. incorporated chopped ligaments by bundling single fibers to mimic the structure of
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FS and electrospun FS into thermosensitive chitosan/ ACL. Notably, the mechanical strength of these constructs
glycerophosphate hydrogels, fabricating a transparent matched that of natural ACLs. Further experiments
scaffold for cartilage regeneration. FS enhancement notably demonstrated that FS scaffolds supported the proliferation,
improved the mechanical properties of the scaffolds. differentiation, and migration of BMSCs and exhibited key
Both scaffold types preserved the chondrocyte cartilage protein markers characteristic of natural ACLs, including
phenotype, with significantly increased glycosaminoglycan collagen I, collagen III, and tenascin C. Teuschl et al.
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content in the FS-hydrogel and notably higher collagen fabricated FS scaffolds, seeded them with cells, and
II expression in electrospun FS-hydrogel. Kim et al. performed ACL resections on 33 goats, randomly divided
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devised a bilayered polyethylene glycol (PEG) hydrogel for into two groups. Histological analysis at 6 and 12-month
cartilage repair. The composite hydrogel featured a high- post-surgery revealed connective tissue growth around the
density PEG top later with a compression modulus of 700.1 FS scaffold. After 6 months, the seeded-cell group exhibited
kPa and a 3D FS-reinforced low-density PEG bottom layer reduced FS material and increased tissue growth compared
with a compression modulus of 13.2 kPa. FS incorporation to the unseeded group. After 12 months, FS density had
ensured robust interfacial bonding. The 3D FS constructs significantly decreased in both groups, accompanied by
achieved a modulus of 567 kPa, with covalently bonded pronounced inward tissue growth. Notably, FS degradation
layers ensuring stability against torsion. The bottom layer and tissue regeneration were comparable between groups.
promoted controlled degradation and cartilage formation. Fan et al. successfully established an ACL regeneration
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This research advances the potential of composite model in pigs using mesenchymal stem cells (MSCs) seeded
hydrogels for joint cartilage reconstruction, with ongoing on FS scaffolds. In vitro, MSCs proliferated effectively,
animal studies exploring further applications. differentiated into fibroblast-like cells, and expressed
Finally, studies confirm the potential of FS-based ligament-specific genes (collagen I, collagen III, and
scaffolds for osteochondral defect repair. Yao et al. tenascin C). Post-implantation, fibroblast-like morphology
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innovatively integrated PLLA porous microspheres into was observed at 24 weeks, along with significant production
FS scaffolds, forming millimeter-scale channels through of ligament-specific ECM. In addition, a ligament-to-bone
physical drilling. This technique was applied to ear cartilage insertion comprising bone, Sharpey’s fibers, and ligament
regeneration. The composite scaffold exhibited remarkable zones was formed. Despite scaffold degradation, the
mechanical strength. In vitro experiments demonstrated regenerated ligament maintained tensile load at 24 weeks,
that the FS+PLLA PMs porous microspheres (CMAF) indicating the promising potential of FS-based, cell-seeded
scaffold enhanced cartilage cell proliferation, migration, scaffolds for ligament repair and regeneration.

Volume 4 Issue 2 (2025) 10 doi: 10.36922/MSAM025130020