In inflammatory bowel disease (IBD) the disruption of the intestinal barrier function and the strong presence of immune-related cells like macrophages in inflamed tissue allow the selective accumulation of particulate carrier systems at the site of action. We developed clodronate loaded nanoparticles (ClNP) based on a cationic polymethacrylate (Eudragit RL) using a modified solvent displacement method. Particle diameter of ClNP was around 120nm and dissolution experiments showed that ionic interactions with either the dissolution medium or mucin have to take place to enable complete drug release. In murine experimental colitis in-vivo, myeloperoxidase activity decreased significantly in 2,4,6-trinitrobenzenesulfonic acid (TNBS)-colitis and oxazolone (OXA)-colitis models after treatment with ClNP while free clodronate did not show a mitigating effect. Similarly, alkaline phosphatase could be lowered significantly from 12.5±1.9 to 6.8±2.2ng/mg tissue in TNBS-colitis and from 16.6±6.2 to 11.8±2.7ng/mg tissue in OXA-colitis. In cultured RAW 264.7 cells, only ClNP but not clodronate alone led to a decrease in tumor necrosis factor-alpha and interleukin-6 secretion of the activated macrophages. The therapeutic benefit of ClNP was confirmed in-vivo although it is limited compared to data with other drugs. Cell culture experiments indicated that intracellular delivery of clodronate was necessary to obtain an anti-inflammatory effect.
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