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Materials Science in Additive Manufacturing Fibrous silk in biomedicine

In another study, Panas-Perez et al. investigated highlighting the urgent demand for small-diameter
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ACL reconstruction using a collagen-FS scaffold. When vascular grafts. Although autologous vessels are ideal,
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FS content was ≥14% and collagen content ≤86%, the their use is limited by scarcity and donor site morbidity. 137-139
scaffold’s initial tensile strength matched or surpassed To address the limitations of autologous grafts, research
that of human ACL. After 8 weeks in a rabbit model, the has increasingly focused on developing artificial blood
scaffold’s strength reduced by 84 – 92%, while its volume vessels through vascular tissue engineering, particularly
decreased by 22 – 26%. Mechanical testing indicated that for small-diameter replacements. 140,141 Key design
scaffolds with an ultimate tensile strength ≥129 MPa and considerations for engineering grafts include resilience to
an FS-to-collagen volume ratio of approximately 48:52 met
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the requirements for ACL reconstruction. Chen et al. cyclic blood pressure, compatibility with host vessels, and
anti-thrombogenicity. Synthetic materials such as polyester
further applied collagen-FS scaffolds for medial collateral and expanded polytetrafluoroethylene have been widely
ligament repair, demonstrating enhanced medial collateral used in vascular surgery; however, they suffer from high
ligament tissue regeneration. In addition, DiSCAFF
technology was employed to coat FS fibers with a HEMA- hydrophobicity, promoting platelet and plasma protein
co-METAC hydrogel, enhancing their mechanical adsorption while hindering endothelial cell adhesion
properties and improving stem cell adhesion. Coated FS and growth. In addition, their inability to grow, repair, or
fibers also upregulated the mRNA expression levels of remodel elevates the risk of thrombosis and may induce
collagen I and III. 131 immune responses, limiting their suitability for small-
caliber (<6 mm) artificial blood vessels. 142,143 Compared to
Fang et al. developed an FS-based tendon scaffold synthetic biomaterials, natural materials such as silk fibers,
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and confirmed its effectiveness through in vitro and in vivo elastin, and collagen exhibit superior biocompatibility and
studies. The scaffold promoted cell adhesion, proliferation, cell compatibility, owing to their functional molecules and
and new tendon formation after 16 weeks in mice. intricate structures. These natural materials demonstrate
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Furthermore, the internal collagen bundles of the newly anti-thrombotic properties and enhanced adaptability.
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formed tendon tissue exhibited uniformity and alignment. Specifically, FS promotes endothelial cell attachment, while
Chen et al. introduced an FS/collagen scaffold loaded SF provides anti-thrombotic surfaces capable of enduring
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with human embryonic stem cells and BMSCs. Both high shear stress and blood flow pressure. 145
in vitro and in vivo studies demonstrated that these cells
differentiated into tendon lineages, successfully generating In recent years, significant progress has been made in
artificial tendon tissue, thus offering a promising approach developing composite vascular grafts based on natural
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for tendon tissue engineering. Zheng et al. created a 3D FS. Mi et al. devised a novel three-layer vascular graft
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macroporous FS scaffold specifically designed for shoulder comprising an FS-woven inner layer, a polyacrylamide
muscle–tendon regeneration. The scaffold fostered a hydrogel middle layer, and a thermoplastic polyurethane
highly structured, tissue-like environment, boosting cell nanofiber outer layer. FS’s intricate weave mimics the
infiltration and differentiation into tendon cells. Finally, structure of vascular collagen, while polyacrylamide
Kardestuncer et al. cultured tendon cells on RGD- and thermoplastic polyurethane replicate the elasticity
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modified FS sutures. Compared to tissue culture plastic and of elastin, thereby enhancing biocompatibility with
unmodified FS, FS-RGD enhanced tendon cell adhesion, endothelial cells and mechanical strength and addressing
proliferation, and differentiation. Specifically, the adhesion issues of rejection and leakage observed with traditional
force of tendon cells on FS-RGD sutures increased by grafts. Nakazawa et al. created an alternative vascular
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1.3-fold relative to control, and the transcription levels graft by weaving and compressing FS onto polymer tubes,
of collagen I and decorin were significantly higher after followed by an SF coating, to foster cell adhesion and
6 weeks. Northern blotting analysis further confirmed proliferation during vascular repair. Ding et al. employed
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that mRNA levels were 2 – 3 times greater on FS-RGD finite element analysis to simulate graft deformation and
compared to tissue culture plastic. compliance, developing vascular grafts with woven FS
skeletons of three pore sizes. His study found that grafts
4.4. Vascular tissue regeneration with intermediate pore sizes provided optimal mechanical

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Vascular diseases, including hypertension and myocardial properties and smooth muscle cell regeneration. Li et al.
infarction, pose a major threat to human life. The global successfully assembled silk nanofibers in formic acid using
burden and mortality from these diseases are projected a microfluidic chip that mimics the geometry of a silkworm
to surge, with an estimated 23.4 million deaths forecasted gland. These fibers exhibited aligned structures, enhanced
by 2030. At present, replacing diseased or narrowed mechanical properties, and promoted cell proliferation.
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vessels remains the most effective treatment, particularly In addition, they demonstrated the ability to modulate

Volume 4 Issue 2 (2025) 11 doi: 10.36922/MSAM025130020