Preparation and characterization of poly(D,L-lactic-co-glycolic acid) nanoparticles containing 3-(benzoxazol-2-yl)-7-(N,N-diethyl amino) chromen-2-one

Nanoparticles (NPs) of poly(D,L-lactic-co-glycolic acid) containing the compound 3-(benzoxazol-2-yl)-7-(N,N-diethyl amino)chromen-2-one (C2) were prepared by the solvent-evaporation technique with a mean loading efficiency of 74.0 +/- 3.0%. Size distribution studies, done with dynamic light scattering and scanning electron microscopy, revealed that these particles were spherical in shape, with a mean diameter of 253 nm, a low polydispersity, and a tendency toward aggregation; the last was confirmed by the low potential. A low release profile was observed for C2 when the NPs were dispersed in Hank's buffer (pH = 7.4); this was related to the low porosity of the NPs and the extremely low diffusivity of C2 in water. Differential scanning calorimetry data presented a glass-transition temperature depression caused by an increase in the NP molecular mobility after the incorporation of C2. Spectroscopic and photophysical data exploring the capabilities of C2 as a fluorescent probe suggested a high microviscosity for the environment in which the probe was allocated, which was most likely due to strong polar interactions involving ester groups from the polymer and the diethylamino moiety from C2. The cellular toxicity and uptake of C2 and NP-C2 systems were evaluated with B16-F10 murine cells, which showed that C2 (in solution or encapsulated) was nontoxic and able to be located inside the neoplasic cells. Besides, the encapsulation method was capable of maintaining the drug's properties and improved the drug delivery to the target cell. (C) 2007 Wiley Periodicals, Inc.