Intra-articular drug delivery system could directly deliver a drug to an affected joint and offer the possibility of reaching high drug concentrations at the site of action with limited systemic toxicity. However, depending on their chemical structure, some active compounds were rapidly cleared from the joint, thus requiring numerous injections, which could cause infection or joint disability. To control the release behavior for prolonged time periods, a novel biologically based drug delivery vehicle was designed for intra-articular using microsphere/thermally responsive hydrogel combination system in this paper. And brucine was the test drug. The system was constructed by dispersing the brucine microspheres which was prepared by using a spray-drying method in a thermally responsive biopolymer hydrogel contained with chitosan-glycerol-borax. The microspheres were spherical as evidenced by the scanning electron microscopy (SEM) photographs. And the entrapment rate was 98.60% w/w with an average size range of 0.9-4.5 μm. Fourier transforms infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) revealed the absence of drug-polymer interaction and amorphous nature of an entrapped drug. From the in vitro drug release study we could see that there was a burst release of microsphere, which was obviously retarded when dispersed in hydrogel. And the studies of biocompatibility with synovium showed that no apparent thickening or hyperplasia of the synovium, a small quality of phlogocyte imbibitions was observed. The results of FX imaging in rats showed that by intra-articular injection the BMH could stay in articular for over 7 days were consistent with our in vitro release. And the results of pharmacodynamics revealed the BMH could benefit OA joint by suppressing the levels of TNF-α and IL-1β, protect the damaged joint from degradation. The novel microsphere/thermoresponsive hydrogel combination system could be a promising treatment option for OA and RA. In conclusion, the system appears to be generally biocompatible with synovium and could control the drug release for several days; hence it might be suitable for the development of treatment strategies for rheumatic diseases.
