Celecoxib-Loaded "Nano-in-Nano" Hierarchical Implant Shows Dual Drug Delivery and Mechanical Support for Osteoarthritis

A research team has developed a celecoxib查看药品详情-loaded "Nano-in-Nano" hierarchical delivery system (NiN-HDS) that integrates sustained anti-inflammatory drug release with adaptive mechanical support for the localized treatment of osteoarthritis (搜索)搜索该疾病 (OA). The implantable platform, described in Drug Design, Development and Therapy, addresses two longstanding challenges in OA management: rapid drug clearance from the joint cavity and the need for mechanical protection of degenerating cartilage under repetitive loading.

The system employs a layered architecture in which drug delivery and mechanical support are structurally decoupled. Celecoxib查看药品详情 (CXB), a BCS Class II non-steroidal anti-inflammatory drug with poor water solubility, was first encapsulated into PLGA (搜索)搜索该药品 nanoparticles (CXB-NPs) via an emulsion solvent evaporation method. These nanoparticles, measuring 64.90 ± 0.57 nm with a polydispersity index of 0.142 ± 0.004 and zeta potential of −13.29 ± 0.35 mV, were then embedded within electrospun PVA nanofibers to form a "Nano-in-Nano" membrane. This membrane was subsequently laminated with a genipin-crosslinked gelatin layer to produce the final NiN-HDS construct.

Structural Characterization and Drug Loading

Transmission electron microscopy confirmed that CXB-NPs retained their nanostructure after electrospinning, with particle size increasing to 138.4 ± 4.3 nm and zeta potential rising to −58.74 ± 16.58 mV—an enhanced electrostatic repulsion that stabilizes the nanoparticles against aggregation. The encapsulation efficiency of CXB-NPs was 72.87 ± 0.30%, with a drug loading of 1.50 ± 0.01%. Scanning electron microscopy of the NiN-HDS revealed uniform nanofibers with an average diameter of 145.95 ± 26.05 nm, and cross-sectional imaging confirmed tight bonding at the nanofiber–gelatin interface with no visible gaps.

Differential scanning calorimetry, X-ray diffraction, and Fourier transform infrared spectroscopy collectively demonstrated that celecoxib查看药品详情 transitioned from its native crystalline state to an amorphous dispersion within the polymer matrix. The characteristic crystalline melting endothermic peak of raw CXB near 169.49°C was virtually absent in both CXB-NF-HDS and NiN-HDS, while sharp XRD diffraction peaks disappeared, confirming amorphization that enhances dissolution and bioavailability.

Sustained Release and Mechanical Performance

In vitro release studies conducted at both pH 6.8 (simulating the mildly acidic OA joint microenvironment) and pH 7.4 (normal physiological conditions) demonstrated that NiN-HDS achieved cumulative celecoxib查看药品详情 release of 67.16% and 68.22%, respectively, over 168 hours. This contrasted sharply with free CXB, which rapidly reached saturation, and CXB-NPs alone, which released 96.70% (pH 6.8) and 95.08% (pH 7.4) by 120 and 96 hours. The release kinetics of NiN-HDS followed the Ritger-Peppas model, with an exponent n of 0.45269 at pH 6.8 indicating a combined Fickian diffusion and matrix erosion mechanism, and n of 0.40931 at pH 7.4 indicating Fickian diffusion-dominated release.

Mechanical testing showed that drug loading did not significantly alter the mechanical properties of the system. NiN-HDS exhibited a Young's modulus of 17.239 ± 2.645 MPa—substantially higher than the 0.5–7.5 MPa range reported for healthy knee cartilage—along with a fracture strength of 20.02 ± 2.34 N and an elongation at break of 307.478 ± 32.011%. The crosslinked gelatin layer approximately doubled the tensile strength compared to uncrosslinked gelatin (P < 0.05). The system reached swelling equilibrium after approximately 150 minutes with a swelling ratio of 163.97 ± 9.76%, and degraded continuously in vitro for over 10 days, reaching approximately 88.53 ± 2.03% mass loss by day 10.

In Vivo Efficacy in a Rat OA Model

Therapeutic efficacy was evaluated in a rat OA model induced by intra-articular injection of monosodium iodoacetate (MIA). At day 28 post-induction, rats were randomized into model, oral CXB (10.5 mg·kg⁻¹ daily), sham surgery, and NiN-HDS implantation groups (n=8 per group). NiN-HDS implants (approximately 3.2 mm × 3.2 mm × 0.5 mm, containing ~20 μg celecoxib查看药品详情) were surgically placed with the nanofiber membrane in contact with femoral trochlear cartilage.

After seven days of treatment, gross morphological evaluation using the Pelletier scoring system showed that the NiN-HDS group exhibited significantly greater cartilage protection than both the model group (P < 0.001) and the oral CXB group (P < 0.05). H&E staining revealed that NiN-HDS-treated joints maintained normal cartilage thickness, improved structural integrity, and higher chondrocyte density compared with model and sham groups. Safranin O-fast green staining demonstrated near-intact cartilage structure with distinct calcified layer boundaries. Mankin scoring confirmed that NiN-HDS treatment produced the most substantial therapeutic effect (P < 0.001 vs. model), surpassing the oral CXB group (P < 0.01 vs. model).

Immunohistochemical analysis revealed that MMP-13 (搜索)搜索该靶点 expression was significantly upregulated in the model group (P < 0.001), while NiN-HDS intervention produced the most pronounced suppression among all treatment groups. Similarly, IL-1β (搜索)搜索该靶点 expression was significantly elevated in the model group versus normal controls (P < 0.001), and NiN-HDS achieved the greatest downregulation. The authors attribute these outcomes to the structural separation of drug delivery and mechanical support functions, which synergistically optimizes sustained anti-inflammatory delivery while providing local mechanical buffering against abnormal joint loads.

The researchers note that the study was conducted in a small-animal model and that durable stability and treatment effectiveness require additional confirmation in large-animal models that better replicate clinical loading conditions. Future directions may include integrating stimuli-responsive or multidrug delivery strategies into the layered architecture.