1,1′-Dioctadecyl-3,3,3′,3′ tetramethylindotricarbocyanine iodide-loaded poly(lactide-co-glycolide) nanoparticles increase local retention after paraspinal muscle injection

Abstract

Poly(lactide-co-glycolide) (PLGA) nanoparticles are promising materials for the development of new drug releasing systems. In this study, PLGA nanoparticles were doped with the fluorescent material 1,1′-dioctadecyl-3,3,3′,3′tetramethylindotricarbocyanine iodide (DiR), and the retention of the nanoparticles was evaluated in mice. Mice (n = 20) were injected with 0.1 mL DiR-loaded PLGA nanoparticles (200 nm) into the right paraspinal muscle, and the same volume of pure DiR solution was injected into the left paraspinal muscle. Fluorescence images were obtained using an IVIS Imaging System. Fluorescent images were taken 1 day after the injection, and seven more images were taken at 1-week intervals. After 7 weeks, 12 mice showed a right-sided dominant signal, representing the DiR-loaded PLGA nanoparticles

five mice showed a left-side dominant signal, representing the free DiR solution

and three mice showed no signal at all beginning 1 day after the injection. These last three mice were excluded from further analysis owing to apparent injection failure. Notably, DiR-loaded PLGA nanoparticles showed significantly higher fluorescence intensity over the 7-week period. In conclusion, the results of the current study suggested that therapeutic agents that bind to PLGA nanoparticles may exhibit prolonged retention times.