TARGETING OF MICRODISCS IN WHITE CELLS TO TIBIAL ABSCESSES IN RABBITS

The ability to deliver drugs to specific foci of infection is a sought -after goal. One solution is to use microparticles as drug carriers. T his approach is limited by detection of microparticles by the reticulo endothelial system (RES). In order to reduce RES uptake of such partic les, we investigated the possibility of ''hiding'' microparticles with in white cells prior to targeting them to experimental tibial abscesse s. We used radioactive silicone microdiscs, supplied by the Royal Sign als & Radar Establishment. Twelve rabbits with abscesses in the right tibia were used: six control animals received radioactive opsonised mi crodiscs intravenously, and six animals received the same dose of micr odiscs following incubation of the microdiscs with white cells. Each a nimal's liver, spleen, lungs, and both tibiae were removed, weighed, a nd homogenised. Radioactivity counts were obtained from each tissue, a nd the ratio of counts per gram of tissue for the right/left tibiae wa s calculated for the two groups of animals. The ratio of counts in the control group was 1.66 (+/- 0.57 SD), and the mean ratio of counts fr om the rabbits who had microdiscs incubated with white cells was 3.32 (+/- 0.52 SD). This difference was statistically significant at p = 0. 02 (Mann-Whitney U test).