Aspartic acid-based modified PLGA–PEG nanoparticles for bone targeting: In vitro and in vivo evaluation

Nanoparticles (NP) that target bone tissue were developed using PLGA–PEG (poly(lactic-co-glycolic acid)–polyethylene glycol) diblock copolymers and bone-targeting moieties based on aspartic acid, (Asp)n(1,3). These NP are expected to enable the transport of hydrophobic drugs. The molecular structures were examined by 1H NMR or identified using mass spectrometry and Fourier transform infrared (FT-IR) spectra. The NP were prepared using the water miscible solvent displacement method, and their size characteristics were evaluated using transmission electron microscopy (TEM) and dynamic light scattering. The bone targeting potential of the NP was evaluated in vitro using hydroxyapatite affinity assays and in vivo using fluorescent imaging in zebrafish and rats. It was confirmed that the average particle size of the NP was <200 nm and that the dendritic Asp3 moiety of the PLGA–PEG–Asp3 NP exhibited the best apatite mineral binding ability. Preliminary findings in vivo bone affinity assays in zebrafish and rats indicated that the PLGA–PEG-ASP3 NP may display increased bone-targeting efficiency compared with other PLGA–PEG-based NP that lack a dendritic Asp3 moiety. These NP may act as a delivery system for hydrophobic drugs, warranting further evaluation of the treatment of bone disease.