The In-Vivo Co-monitoring of Protein, Polymeric Delivery System, and Spectator Ions by Radioisotope Induced X-Ray Fluorescence

Abstract The subcutaneous delivery of iodinated bovine serum albumin (I-BSA) incorporated into a barium alginate hydrogel matrix, synthesized from barium bromide, was monitored in vivo by radioisotope-induced X-ray fluorescence. By measuring the iodine, barium, and bromine X-ray fluorescence signals, we were able to simultaneously monitor the status of an entrapped protein, the hydrogel delivery device, and the spectator ions in the hydrogel. The release of the labeled protein followed first-order kinetics with half-lives of 6 h for the I-BSA in phosphate buffer solution up to 28 h for the I-BSA incorporated in the alginate hydrogel. The degradation of the barium alginate hydrogel was biphasic, and the disappearance of the bromide spectator ion from the hydrogel was well described by Fickian diffusion.