RGD-modified PEGylated paclitaxel nanocrystals with enhanced stability and tumor-targeting capability

Nanocrystals has been constructed for insoluble drugs as a novel type of nanoscale drug delivery systems with high drug loading. How to prepare nanocrystals with good stability and tumor targeting capability is still challenging. This study was to modify paclitaxel nanocrystals with polyethylene glycol (PEG) for stabilization and RGD peptide for tumor targeting. Inspired by the structure of mussels foot protein, polydopamine (PDA) was introduced to the drug delivery system for the modification of nanocrystals. Briefly, PDA was coated on the surface of nanocrystals to form a reaction platform for further PEGylation and RGD peptide conjugation. PEGylated nanocrystals with RGD peptide modification (NC@PDA-PEG-RGD) were prepared with near-spheroid shape, drug loading 45.12 +/- 1.81% and a hydrodynamic diameter 419.9 +/- 80.9 nm. The size of NC@PDAPEG-RGD remained basically unchanged for at least 72 h in the presence of plasma while the size of unmodified nanocrystals (NC) increased and exceeded 1000 nm in 12 h. Cellular uptake and cellular growth inhibition experiments using the lung cancer cell line A549 demonstrated the superiorly of NC@PDA-PEG-RGD over NC or PEGylated nanocrystals without RGD modification (NC@PDA-PEG). In A549 model tumor bearing-mice, NC@PDA-PEG-RGD showed significantly higher intratumor accumulation and slower tumor growth than NC@PDA-PEG or free paclitaxel. In summary, our study suggested the superiority of RGDmodified PEGylated paclitaxel nanocrystals as a lung cancer-targeted delivery system and the potential of PDA coating technique for targeting functionalization of nanocrystals.