Modification of the soft tissue response to implanted materials through the use of an anti-inflammatory drug

The soft tissue response of adult rats to a drug-loaded copolymer hydrogel was studied histologically by using monoclonal antibodies specific for certain inflammatory cell types. A hydrogel was loaded with Diclofenac sodium, a non-steroidal anti-inflammatory drug, and designed to release the drug at a constant rate after implantation into muscle tissue. The sites of antibody binding were analysed automatically, by using an image analysis system, providing information on the number of inflammatory cells and their distribution relative to the hydrogel implant. The ability to measure these and other parameters is considered to be of major importance in the assessment of biocompatibility. The experiments demonstrate that Diclofenac sodium (25–30 µg ml^–1) reduced the number of macrophages and neutrophils found at the implant site compared with a PBS control. Diclofenac sodium did not have any effect on the T cell response.