A new nanocomposite membrane uses layered fiber design to combine strength, flexibility, and antibacterial function for improved bone regeneration.
(Nanowerk Spotlight) Surgeons treating large bone defects—whether after tumor removal, traumatic injury, or severe infection—face a material problem with few good options. After clearing the damaged area, the space must be protected and isolated to allow new bone to grow. That protection comes in the form of a barrier membrane: a thin implant designed to keep soft tissue out while supporting the formation of new bone beneath it.
But in practice, most membranes fail to meet the competing demands of surgery and biology. They must be tough enough to resist pressure from surrounding tissue, flexible enough to conform to irregular surfaces, permeable to nutrients yet impermeable to bacteria, and stable long enough to support healing before degrading safely into the body.
Collagen membranes dominate the market due to their biodegradability and ease of use. However, their mechanical weakness and lack of antibacterial function make them vulnerable to failure, especially in complex or contaminated wounds. Titanium mesh solves the strength problem but is stiff, permanent, and can provoke inflammatory reactions. Neither approach delivers the combination of mechanical integrity, biological compatibility, and environmental responsiveness needed for robust bone regeneration.
Attempts to improve synthetic alternatives have produced partial results: better strength here, longer degradation there, but rarely all properties together in a single system. What’s missing is not another material, but a method for integrating materials structurally and functionally.
Biological systems offer solutions to similar design challenges. Nacre, the layered shell coating in mollusks, and the Bouligand structure—made of fibers stacked in a twisted, spiral-like pattern found in fish scales and insect exoskeletons—both achieve mechanical toughness through hierarchical organization. Nacre resists fracture through a staggered layering of stiff minerals and soft proteins, while Bouligand architectures twist fibers across layers to redirect and dissipate force.
Inspired by this, researchers at the University of Science and Technology of China and Tongji University developed a nanocomposite membrane that merges these structural principles into a single, functional material. Designed for guided bone regeneration, it addresses the contradictions that have stalled progress in membrane design (Advanced Materials, “Sword and Board in One: A Bioinspired Nanocomposite Membrane for Guided Bone Regeneration”).
The combination of structure design and composition regulation for multifunctionality. A) Schematic illustration of bioinspired design of d-BLG (nacre-inspired discontinuous Bouligand) nanocomposite membrane coupling nacre-like discontinuous arrangement, fiber-based Bouligand structure, and multiple components. B) d-BLG functions as “sword and board in one” for guided bone regeneration treatment. (Image: Reprinted with permission by Wiley-VCH Verlag) (click on image to enlarge)
The membrane, named d-BLG (nacre-inspired discontinuous Bouligand), incorporates a helically arranged fiber network with controlled discontinuities that mimic nacre’s staggered layers. It is built from four components: calcium silicate and silver nanofibers provide the inorganic phase; silk fibroin and sodium alginate form the organic matrix.
The fabrication process uses a liquid-phase sliding shear technique, allowing nanofibers to align in successive layers with a 20-degree rotation between each. This assembly produces a Bouligand-like architecture and a Janus surface—one rough and cell-adhesive, the other smooth and resistant to bacterial attachment.
Structurally, the membrane offers both passive mechanical strength and active biological interaction. Its twisted fiber layers enhance flexibility while resisting tearing or puncture. Under conditions mimicking infection, the acidic environment triggers the release of calcium ions from calcium silicate. These ions strengthen the membrane through additional crosslinking and help buffer the pH toward a more alkaline range, which favors bone cell activity and suppresses bacterial growth.
In mechanical tests under wet conditions, the d-BLG membrane showed a tensile strength of 12.4 MPa and could stretch over 100% before breaking. Its toughness reached 6.7 MJ/m³, exceeding that of membranes made with unidirectional or randomly oriented fibers. The puncture resistance was also significantly higher, with a peak force of 3.34 N.
When immersed in saline for 21 days, the membrane retained over 60% of its mass and maintained barrier function, whereas the commercial Bio-Gide collagen membrane degraded visibly and allowed cell infiltration. These performance advantages were attributed to the Bouligand architecture’s ability to deflect cracks and resist hydrolytic weakening, as confirmed by molecular simulations showing reduced water penetration compared to simpler fiber alignments.
Biological evaluations confirmed that the membrane also supports cell proliferation and osteogenic differentiation. Rat bone marrow stem cells seeded on the rough side of the membrane attached and spread effectively. Gene expression of osteogenic markers—including ALP, RUNX2, OCN, and collagen type I—was significantly elevated by day 7.
Antibacterial activity was equally strong: silver ions released from the membrane killed over 96% of both gram-positive (Staphylococcus aureus) and gram-negative (E. coli) bacteria depending on the silver ratio, with minimal cytotoxicity. This dual behavior—supporting bone-forming cells while actively suppressing microbial growth—is critical for success in contaminated surgical fields.
In vivo studies in rat calvarial (skull) defect models further demonstrated the membrane’s effectiveness. In both normal and bacteria-contaminated defects, the d-BLG membrane led to extensive new bone formation after eight weeks. Micro-CT imaging showed near-complete bridging of the defect space, and histological analysis confirmed the presence of mature bone tissue with organized collagen structure.
In contrast, the collagen control degraded too quickly to protect the defect site, leading to fibrous infiltration and minimal regeneration. The combination of sustained barrier function, mechanical resilience, and biological activity translated into a marked improvement in regenerative outcomes.
This performance is not the result of introducing exotic materials, but of organizing familiar ones in a more intelligent way. Each component—alginate, silk, calcium silicate, silver—has known biomedical applications. What makes the d-BLG membrane different is how these are structurally combined. The sliding shear fabrication technique allows the production of an ordered, helicoidal fiber network with precisely tuned interfaces and surface asymmetry. This enables a single-step, scalable, and additive-free route to a Janus membrane, eliminating the need for complex layering or chemical surface modifications.
The study demonstrates that multifunctionality does not require trade-offs when structure is used as a unifying principle. By translating biological architectural motifs into synthetic materials, the researchers have produced a membrane that withstands stress, conforms to irregular defects, resists infection, and promotes bone regrowth—all within a degradable, biocompatible scaffold.
The success of this strategy in both controlled and infected conditions suggests strong potential for clinical translation. Rather than compensating for material weaknesses with drugs or coatings, this work shows how structure alone can solve multiple design constraints, advancing both guided bone regeneration and the broader field of functional biomaterials.
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