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Materials Science in Additive Manufacturing Fibrous silk in biomedicine

instantaneously heats a thin film beneath the donor layer, synchronized with the rate of tissue regeneration to
propelling droplets of high-viscosity biomaterials – such prevent premature material failure or prolonged scaffold
as FS hydrogels – with submicron precision. This enables persistence, which may lead to chronic inflammation or
the construction of intricate microarchitectures and fibrosis. Further, achieving high print fidelity, maintaining
multi-cellular composite constructs while preserving high structural integrity post-printing, and ensuring long-term
cell viability. DLP, by comparison, offers rapid, spatially shelf stability remain key technical hurdles.
controlled solidification of photosensitive FS-based On the commercialization front, regulatory pathways
bioinks, achieving fast printing speeds and highly accurate are often slow, fragmented, and inconsistent. Although over
scaffold geometries. It is particularly suitable for producing 700 FS-related studies are published annually, only a small
bone, cartilage, and neural tissue scaffolds. fraction progress to clinical trials. To date, few FS-derived
LIFT offers several unique advantages for complex products – such as Silk Voice – have received approval
tissue engineering. For example, in neural tissue from the United States Food and Drug Administration,
applications, LIFT has been used to deposit neural stem and these are typically in powder form, limiting their
cell-laden FS bioinks to generate aligned scaffolds that suitability for implantable tissue-engineered constructs.
promote directional axonal growth and support functional To advance FS bioprinting toward clinical translation,
recovery. In addition, LIFT has been applied to fabricate three key areas must be addressed: (i) scalable and
microvascular networks by precisely patterning endothelial standardized bioink production, with modular design
cells and FS, achieving a synergistic integration of biological and reproducible print performance; (ii) establishment
activity and structural fidelity. A key advantage of LIFT is of unified regulatory frameworks and expedited approval
its nozzle-free mechanism, which avoids shear stress and processes; and (iii) integration with cutting-edge
nozzle clogging – common issues in conventional nozzle- technologies such as stem cell engineering, organ-on-a-
based printing – making it especially advantageous for chip platforms, and microfluidics. Through innovations in
printing highly viscous or cell-laden FS-based inks. 214 these areas, FS-based biomaterials may enable a paradigm
Since unmodified FS lacks photocrosslinkable shift from structural repair to true biological regeneration.
functional groups, it is not directly suitable for DLP
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printing. To meet the photocuring requirements of DLP, 6. Limitations and prospects of FS -based
FS has been chemically modified through methacrylation biomaterials
to produce silk methacrylate (Sil-MA), significantly To provide a balanced view of the biomedical advantages
enhancing its printability in light-based systems. Sil-MA and challenges of FS materials, we summarize their
bioinks exhibit favorable rheological behavior and tunable key strengths and weaknesses in Table 3. For further
crosslinking kinetics, resulting in excellent shape fidelity context, Table 4 offers a detailed comparison of FS with
and structural stability during printing. Experimental other commonly used biomaterials, including collagen
studies have demonstrated that Sil-MA scaffolds effectively and synthetic polymers, based on parameters such as
support the encapsulation, proliferation, and functional mechanical properties, biocompatibility, degradation
expression of various cell types, including chondrocytes, behavior, cost, and scalability. These tables serve as a
osteoblasts, and endothelial cells. These properties make foundation for the following discussion on the current
Sil-MA a promising FS-based platform for applications in limitations and future prospects of FS-based biomaterials.
bone, cartilage, corneal, and vascular tissue engineering.
6.1. Limitations of FS -based biomaterials
5.4. Technical challenges and future directions
The long-term in vivo stability of FS scaffolds is
Despite the significant promise of FS-based 3D printing critically influenced by their degradation behavior and
in regenerative medicine, several challenges hinder its compatibility with tissue regeneration timelines. Although
clinical translation. First, the current range of FS bioinks the β-sheet structure of FS confers slow degradation
remains limited in both diversity and function, restricting (typically exceeding 12 weeks), exposure to dynamic
their application in the engineering of multicellular mechanical environments (such as joints or blood vessels)
and architecturally complex tissues. To address this, can cause material fatigue or disruption of crystalline
future efforts must focus on chemical modifications, domains, ultimately compromising structural integrity.
incorporation of ceramic or conductive components, and For example, FS scaffolds implanted in the ACL of goats
the development of gradient formulations to enhance exhibited significant mechanical strength degradation
mechanical performance and biological function. Second, after 12 months, despite incomplete material resorption.
the degradation kinetics of FS scaffolds must be precisely In addition, the size and chemical composition of FS

Volume 4 Issue 2 (2025) 15 doi: 10.36922/MSAM025130020