ウィースターラットにおける関節内注射：ナノマテリアル投与のための正確なプロトコルの標準化と実験的検証

(1) Background: Intra-articular injection is a fundamental technique in preclinical research for evaluating therapeutics and inducing joint disease models in rodents. However, the absence of standardized and validated protocols compromises reproducibility and translational validity. (2) Methods: This study establishes and experimentally validates a refined protocol for precise intra-articular injection in the knee of adult male Wistar rats. The comprehensive procedure specifies anatomical landmarks (medial border of the patellar tendon), instrumentation (27 G needle, 100 µL Hamilton syringe), a maximum volume of 35 µL, and operative verification criteria based on tactile feedback. Experimental validation was performed by administering a suspension of wear particles (2.35 mg/mL) generated from tribocorrosion tests of CoCr surfaces biofunctionalized with graphene oxide-hyaluronic acid (GO-HA) into the left knee of five rats. (3) Results: Histological analysis using the cutting-grinding technique and Toluidine Blue staining confirmed the exclusive intra-articular localization of particles in all injected animals (5/5 success rate). Qualitative assessment revealed abundant particulate distribution within the synovial space, with numerous individual particles and multiple aggregates observed per high-power field, without evidence of extravasation in any case. (4) Conclusions: The protocol demonstrated high intra-operator repeatability and provides a reliable, ethically refined tool for precise intra-articular administration of nanomaterials and for generating robust joint disease models, thereby enhancing reproducibility and animal welfare in preclinical research.