Preparation and characterization of anionic pullulan thermoassociative nanoparticles for drug delivery

Thermoassociative nanoparticles were obtained through the crosslinking reaction of periodate oxidized carboxymethyl pullulan with two difunctional Jeffamines: ED-600 and ED-2003. The nanoparticles were characterized through 1H NMR spectra; their particle size, determined by dynamic light scattering (DLS) presented a bimodal distribution, with dimensions varying as a function of amount and type of crosslinking agent used; transmission electron microscopy photos confirmed the spherical shape of the nanoparticles and their dimensions determined by DLS. Their amphiphilic character was evidenced by retention of the dyes: hydrophobic (Rose Bengal), amphiphilic (Brilliant Blue) and hydrophilic (Vitamin B12). The thermosensitive properties, more pronounced for ED-2003 crosslinked nanoparticles, were evidenced through absorbance variation, fluorescence and DLS measurements as a temperature function. The nanoparticles retain important amounts of anionic (diclofenac: 40–80 mg/g), cationic (methylene blue: 70–125 mg/g) and hydrophobic (alpha-tocopherol: 220–350 mg/g) drugs. The in vitro characterization of the drug–polymer conjugates recommends the synthesized nanoparticles as supports for drug delivery.