Technetium-99m-labeled poly(DL-lactide-co-glycolide) nanoparticles as an alternative for sentinel lymph node imaging

The present investigation was focused on developing Technetium-99m (⁹⁹(m)Tc)-labeled poly(dl-lactide-co-glycolide) (PLGA) nanoparticles as an alternative to ⁹⁹(m)Tc-labeled sulfur colloid/albumin nanocolloid for sentinel lymph node detection. PLGA nanoparticles were prepared by emulsion solvent evaporation technique and the system was characterized with respect to particle size and morphology. They showed spherical morphology with a mean particle diameter of ∼131 nm and a low polydispersity index indicative of homogenous distribution. The developed colloidal system was further stabilized by lyophilization, and the lyoprotective action of various carbohydrate cryoprotectants was investigated. The lyophilized product was characterized with respect to particle size, appearance, and reconstitution ability. Further, the PLGA nanoparticles were labeled with ⁹⁹(m)Tc using SnCl₂ as the reducing agent. ⁹⁹(m)Tc-labeling yield was not high, requiring purification of labeled product, but purified product was stable for up to 12 hours when stored at 4°C in saline. Biodistribution and scintigraphic imaging studies performed in Wistar rats revealed localization of ⁹⁹(m)Tc-labeled PLGA nanoparticles in the sentinel nodes. Although further modification of labeling route is required for a clinically suitable product, the developed ⁹⁹(m)Tc-PLGA nanoparticle system provides an adequate proof-of-concept for PLGA-based systems as an advantageous replacement to currently used sentinel lymph node detection tools.