Characterization of biodegradable poly(D,L-lactide-co-glycolide) nanoparticles loaded with bacteriochlorophyll-a for photodynamic therapy

Objective: Bacteriochlorophyll-a (BChl-a) was incorporated into nanoparticles of poly(D,L-lactide-co-glycolide) (PLGA), in order to evaluate this photosensitizer when associated with this specific drug delivery system (DDS) to analyze its physical and spectral properties. Background Data: It has been suggested in the literature that BChl-a is a potential sensitizer in photodynamic tumor therapy and until now has only been investigated in organic media. Methods: Nanoparticles loaded with the photosensitizer BChl-a were prepared by the solvent evaporation technique. Parameters such as particle size, drug encapsulation efficiency, external morphology, and in vitro release behavior were evaluated. The photophysical properties (absorption, fluorescence, fluorescence quantum yields, and singlet oxygen quantum yields) of BChl-a, were investigated in toluene and when encapsulated in nanoparticles. Results: Scanning electron microscopy and dynamic light scattering revealed that particles loaded with BChl-a are spherical in shape, and they have a diameter of 660 nm and a low tendency to aggregate. The encapsulation efficiency obtained in this procedure was 69%. Spectroscopic analysis showed an absorption band centered at 782 nm in nanoparticles used as a DDS. Fluorescence quantum yield (phi F = 0.19) and higher efficiency in singlet oxygen production (Phi(Delta) = 0.26) was also observed. Conclusions: The results suggest that this DDS is potentially useful for the delivery and release of BChl-a as a photosensitizer in photodynamic therapy (PDT) protocols due to its excellent biodegradability, biocompatibility, and maintenance of its spectroscopic properties when compared with other dyes in homogenous media. The biocompatible DDS medium is a new proposal and will make feasible the use of BChl-a as a dye for PDT, improving the utilization of non-organic media to deliver this kind of molecule.