(1) Abstract: 

From a bone regeneration materials perspective, this study constructs a biodegradable Janus piezoelectric membrane, J-PLLA-ZnO, based on PLLA. One side is a dense layer acting as a soft-tissue barrier, while the other is a porous PLLA-ZnO nanowire interface providing piezoelectric responses and acidic microenvironment-responsive Zn²⁺ release. The material integrates spatial barrier protection with defect-facing bioactivity in a single membrane, combining antibacterial action, immunomodulation, and osteogenic promotion in an infected bone defect model, reducing alveolar bone loss and improving bone defect repair.

(2) Background: 

Bone defect repair is often limited by infection, chronic inflammation, and soft-tissue invasion, forming a pathological cycle of inflammation, bone resorption, and impaired repair. Conventional barrier membranes mainly provide physical isolation and struggle to simultaneously regulate the infected microenvironment and promote osteogenesis. Bone tissue engineering requires spatially rational integration of barrier protection, antibacterial/immunomodulatory regulation, and osteogenic stimulation. Piezoelectric materials convert mechanical stimuli into electrical signals, providing a biomimetic electrical microenvironment for bone regeneration.

(3) Main Content: 

A Janus structure was constructed by electrospinning PLLA, in situ growth of ZnO nanowires, and spin-coating a dense PLLA layer. The dense layer restricts fibroblast penetration, while the porous ZnO-functional interface enhances piezoelectric output and releases Zn²⁺ under acidic conditions. The ZnO interface inhibits periodontal pathogens and biofilms, promotes macrophage polarization toward a reparative phenotype, and enhances osteogenic differentiation of periodontal ligament stem cells. In vivo, it controls early infection and inflammation and improves bone height and bone formation at later stages.

(4) Study Design: 

Morphology, elemental distribution, FTIR/XRD, mechanics, piezoelectric output, contact angle, Zn²⁺ release, and degradation were characterized. In vitro assays evaluated cytocompatibility, osteogenic mineralization, ALP, osteogenic genes and proteins, antibacterial activity and biofilms, and macrophage polarization. A rat periodontal bone defect model was established, with micro-CT, H&E, Masson, immunohistochemistry, and transcriptomics for early inflammation and long-term bone regeneration analysis.

(5) Results: 

Janus construction did not obviously weaken the osteogenic activity of the ZnO-functional interface. The ZnO interface showed antibacterial activity, biofilm disruption, and promotion of M2-related polarization, and increased osteogenic markers and mineralization. In vivo, it reduced early inflammation and bacterial colonization, improved long-term alveolar bone height, bone formation, and periodontal ligament-like tissue organization, and reduced soft-tissue invasion; no obvious histopathological abnormalities were observed in major organs.

(6) Future Directions:

From a bone regeneration perspective, this work provides a composite design strategy of "spatial compartmentalization + piezoelectric interface + ion release." Future studies should distinguish the independent contributions of piezoelectric stimulation, Zn²⁺ release, and nanotopography to osteogenesis and osteoclastogenesis, optimize piezoelectric output and ion release kinetics, evaluate long-term degradation, immune homeostasis, and bone remodeling quality in infected bone defects, and test the generality of the materials principles in different bone defect models.

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