Electrospinning Machine| Polylactic acid-Ag@Sr composite membranes with balanced osteogenic and antibacterial properties for guided bone regeneration

The large-scale repair of alveolar and craniomaxillofacial bone defects is a significant clinical challenge. Although guided bone regeneration (GBR) membranes have been widely used, traditional multi-component GBR membranes still suffer from limitations such as single functionality, complex structure, and poor stability, particularly in infectious cases. Therefore, developing multifunctional GBR membranes that combine osteogenic and antibacterial properties while maintaining biocompatibility is crucial.\

Recently, Professor Chen Qiang’s team at Northwestern Polytechnical University published their latest research, "Polylactic acid-Ag@Sr composite membranes with balanced osteogenic and antibacterial properties for guided bone regeneration," in the International Journal of Biological Macromolecules. The researchers prepared a composite fiber membrane of polylactic acid (PLA) and bifunctional core-shell nanoparticles (Ag@MSN@Sr) via a one-pot electrospinning process, integrating osteogenesis, antibacterial activity, and biocompatibility.

This design employs an Ag-Sr "two birds with one stone" synergistic strategy for infectious bone regeneration. The "Ag core" in the core-shell nanoparticles provides broad-spectrum antibacterial effects by sustained Ag⁺ release, preventing post-implantation infections, while the Sr²⁺ loaded in mesopores promotes osteoblast proliferation and differentiation by activating the Wnt/β-catenin pathway and stimulates collagen production to synergistically enhance bone formation. The MSN shell not only precisely regulates dual-ion release kinetics but also buffers acidic PLA degradation products via its Si-OH groups, creating a favorable microenvironment for bone repair.

Figure 1: Design concept of the PLA-Ag@Sr composite nanofiber membrane.

Through systematic characterization of the physicochemical/mechanical properties and ion release behavior of the PLA-Ag@Sr composite membrane, combined with in vitro evaluations of cytocompatibility, antibacterial activity, and osteogenic performance—as well as in vivo validation using rat cranial infection and defect models—the results demonstrated that the PLA-Ag@Sr membrane exhibits excellent biocompatibility, mechanical strength, osteogenic capacity, and antibacterial properties, showing significant potential for GBR applications.

Figure 2: Fabrication and morphology of the PLA-Ag@Sr composite nanofiber membrane.

Using a "kill two birds with one stone" material design strategy, the researchers prepared core-shell structured Ag/Sr co-doped mesoporous silica nanoparticles (Ag@MSN@Sr) via a sol-gel method and fabricated the PLA-Ag@Sr composite nanofiber membrane via electrospinning. As shown in Figure 2, SEM images of PLA-Ag@Sr revealed uniform fiber morphology with evenly distributed doped particles. After particle incorporation, the PLA fiber diameter significantly decreased from 518 ± 160 nm to 208 ± 72 nm (PLA-Ag@Sr).

Figure 3: Physicochemical characterization of the PLA-Ag@Sr composite nanofiber membrane.

Figure 3c shows that PLA-Ag@Sr has a water contact angle of 50.9 ± 3.5°, indicating moderate hydrophilicity, which facilitates cell spreading. Stress-strain curve analysis (Figures 2d-e) demonstrated that compared to pure PLA membranes (elastic modulus: 8.5 ± 0.8 MPa), the introduction of nanoparticles increased the moduli of PLA-Ag and PLA-Ag@Sr by 27.1% (10.8 ± 1.9 MPa) and 56.5% (13.3 ± 0.5 MPa), respectively, attributed to nanoparticle reinforcement.

The PLA-Ag@Sr membrane also exhibited outstanding mechanical adaptability—remaining intact after 720° twisting (Figure 3f), stretching 50% under 4N tension without breaking (Figure 2g), and even supporting a 500g weight (Figure 3h), meeting clinical GBR membrane mechanical requirements.

Ion release studies (Figures 3i-j) revealed that PLA-Ag@Sr achieves dual-ion controlled release via the core-shell structure (Ag@MSN@Sr)—Ag⁺ rapidly releases within 24 hours (preventing early bacterial colonization), while Sr²⁺ sustains release for 21 days (matching bone healing cycles).

Figure 4: In vitro antibacterial performance of the PLA-Ag@Sr composite nanofiber membrane.

Figure 5: In vitro biocompatibility of the PLA-Ag@Sr composite nanofiber membrane.

Figure 6: In vitro osteogenic performance of the PLA-Ag@Sr composite nanofiber membrane.

Figure 7: In vivo osteogenic performance of the PLA-Ag@Sr composite nanofiber membrane.

Figure 8: In vivo biocompatibility of the PLA-Ag@Sr composite nanofiber membrane.

Furthermore, in vitro and in vivo experiments confirmed that the PLA-Ag@Sr composite membrane exhibits excellent antibacterial properties (>99% inhibition against S. aureus and E. coli), good biocompatibility, and osteogenic activity, upregulating osteogenic markers (RUNX2, COLIα, OCN, OPG, OST) and significantly promoting mineralized nodule formation.

This study provides a new strategy for constructing an integrated anti-infection and bone-regenerating GBR platform and offers novel insights into multifunctional electrospun membrane development.

Paper link: https://www.sciencedirect.com/science/article/pii/S0141813025057824