Efficiency of magnetic liposomal transforming growth factor‐beta 1 in the repair of articular cartilage defects in a rabbit model

We evaluated the efficacy of a magnetic liposomal delivery system of transforming growth factor (TGF)‐β 1 in the treatment of articular cartilage defects in a rabbit model. Articular cartilage defects were created in the patellar groove of rabbits, and a permanent magnet or a nonmagnetic alloy was implanted in the defect site. Magnetic liposomal drugs, prepared by the conventional film method and sonication, were injected into the defect site 1 week after surgery. First, the efficacy of the magnetic liposomal delivery system was evaluated by using a model compound fluorescence‐labeled dextran 40,000 (FD‐40). Then, the therapeutic efficiency of magnetic liposomal TGF‐β 1 was evaluated by cartilage histological scoring at 4, 8, and 12 weeks after surgery. The injected magnetic liposomal FD‐40 accumulated at the target site where a permanent magnet had been implanted. The histological score showed that the injection of magnetic liposomal TGF‐β 1 under magnetic force was significantly effective in the repair of the defect site over 12 weeks after surgery. Injection of TGF‐β 1 into the cartilage defect was effective as a magnetic liposomal preparation under magnetic force, resulting in acceleration of the cartilage repair, probably because of the desirable accumulation of TGF‐β 1 at the target site. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res 73A: 255–263, 2005