SMALL PARTICLES OF FUSINITE AND CARBOHYDRATE CHARS COATED WITH AQUEOUS SOLUBLE POLYMERS - PREPARATION AND APPLICATIONS FOR IN-VIVO EPR OXIMETRY

The development of oxygen-sensitive paramagnetic materials is being pu rsued actively because of their potential applications in in vivo EPR oximetry. Among these materials, several charcoals and carbohydrate ch ars are of special interest because of their desirable EPR properties: high sensitivity of the EPR linewidth to the partial pressure of oxyg en, simple EPR spectra, and high spin density, Their potential use in humans, however, is limited by the need to demonstrate that they will not lead to deleterious effects. A strategy was used to optimize the b iocompatibility of the oxygen-sensitive materials by decreasing the si ze of the particles and coating them with suspending or surfactive age nts such as arabic gum, poloxamer (Pluriol 6800(R)), and polyvinylpyrr olidone. The coated particles of a carbohydrate char and fusinite were characterized in vitro for their size, stability, and pO(2) sensitivi ty. The feasibility of performing pO(2) measurement was examined in vi vo by inducing ischemia in the gastrocnemius muscle of mice, The use o f arabic gum for coating the fusinite particles preserved the pO(2) se nsitivity in vivo, whereas the other surfactive agents led to a loss o f the pO(2) sensitivity in vivo. Small particles of fusinite coated by arabic gum and intravenously administered to mice accumulated in the liver, whereas the uncoated fusinite was toxic when injected intraveno usly due to the large size and aggregation of the particles. Histologi cal studies performed up to 6 months after the injection in muscles of mice did not indicate any toxicity from the materials used in the pre sent study.