POLYAMINO ACID MICROSPHERES - PREPARATION, CHARACTERIZATION AND DISTRIBUTION AFTER INTRAVENOUS-INJECTION IN RATS

A series of poly(hydroxypropyl L-glutamine) (PHPG) microspheres (mean diameter 2-3 mum) modified from poly(benzyl L-glutamate) (PBLG) were p repared and characterized. The microspheres were radiolabeled with I-1 31 for in vivo evaluation. Two different labeling methods were used fo r these particles. For PHPG, microspheres were directly labeled with I -131 via Iodogen. For PBLG, microcapsules loaded with a radiotracer ([ I-131]ethyliopanoate) were prepared. The tissue distribution of these particles was studied after intravenous injection in rats. The liver u ptake of PHPG microspheres at 20 minutes postadministration was reduce d from 74 to 19% of injected dose when hydrophilicity of PHPG microsph eres increased. Such reduction was also noted by increasing blood acti vity and decreasing spleen activity. Moderate clearance of PHPG micros pheres from the liver and the spleen was observed in the experimental period (2 days), suggesting that the polymer was degraded. The hydroxy functional groups present on the surface of poly(hydroxypropyl L-glut amine) microspheres allow attachment of targeting devices or drugs. Th us they may find potential applications as targetable drug carriers.