Chitosan-Coated Poly(lactic-co-glycolic acid)-Diiodinated boron-Dipyrromethene Nanoparticles Improve Tumor Selectivity and Stealth Properties in Photodynamic Cancer Therapy.

Their limited solubility and lack of tumor selectivity limit the clinical usefulness of photosensitizers. Various nanostructures have been evaluated as delivery agents for photosensitizers in an attempt to overcome these obstacles, but these have typically been limited by premature clearance by the reticuloendothelial system (RES) and non-specific interactions with normal cells that result from their hydrophobic surfaces. In this study, we report our attempt to circumvent these problems by applying a low molecular weight chitosan (25 kDa) coating to a poly(lactic-co-glycolic acid)-diiodinated boron dipyrromethene (PLGA-I2BODIPY) nanoparticle-photosensitizer construct. This chitosan coating increased the hydrophilicity and decreased the charge of PLGA-I2 BODIPY nanoparticle surfaces without changing their size (average diameter 147 nm) or morphology. In comparison to the uncoated controls, the coated nanoparticles reduced the burst release of I2BODIPY, increased its predominantly lysosomal cellular uptake, and enhanced its photocytotoxicity in 4T1 murine and MDA-MB-231 human breast cancer cells. PLGA-Chitosan-I2BODIPY nanoparticles also showed reduced serum protein adsorption and macrophage uptake compared to the uncoated controls. In 4T1 tumor-bearing mice, the PLGA-Chitosan-I2BODIPY nanoparticles exhibited better tumor-targeting selectivity and significantly reduced accumulation in RES tissues, including the lymph nodes, spleen and liver (by 10.2-, 2.1- and 1.3-fold, respectively), and in non-tumorous organs, such as the skin and eyes (by 22.7- and 4-fold, respectively). The PLGA-Chitosan-I2BODIPY and PLGA-I2BODIPY nanoparticles also showed increased anticancer efficacy compared to free I2BODIPY. These results suggest that the low molecular weight chitosan (25 kDa) is a promising nanoparticle "stealth coating" that improves tumor selectivity.