RESUMEN
Characterization of zein aqueous solutions, as a function of the ethanol content and pH, was performed, giving information on the zein aggregation state for the construction of complexes. The aggregation state and surface charge of zein was found to depend on the mixed solvent composition and pH. Nonstoichiometric complex nanoparticles (NPECs) were prepared by electrostatically self-assembling zein, as the polycation, and sodium alginate or chondroitin sulfate, as the polyanions, at a pH of 4. A wide range of parameters were investigated: the alcohol-water content in the zein solutions, the charge molar ratios, the solution addition order and the addition rate. The resulting nanoparticles were characterized by dynamic and electrophoretic light scattering, circular dichroism and scanning electron microscopy. The smallest size for the NPECs (100 nm) was obtained when the polysaccharides acted as the titrate with an addition rate of 0.03 mL·min-1. The NPECs with the best characteristics were selected for loading with ciprofloxacin and then deposited on a cellulosic material in order to evaluate their antibacterial activity. Substantial drug encapsulation with desired drug release profiles were found together with notable antibacterial efficiency, showing the tunability of the properties for both the zein and its complexes with polysaccharides, together with their application potential in the biomedical field.
RESUMEN
A hybrid synthetic-natural, thermoresponsive graft copolymer composed of poly(N-isopropyl acrylamide) (PNIPAM) side chains, prepared via RAFT polymerization, and a chitosan (Chit) polysaccharide backbone, was synthesized via radical addition-fragmentation reactions using the "grafting to" technique, in aqueous solution. ATR-FTIR, TGA, polyelectrolyte titrations and 1H NMR spectroscopy were employed in order to validate the Chit-g-PNIPAM copolymer chemical structure. Additionally, 1H NMR spectra and back conductometric titration were utilized to quantify the content of grafted PNIPAM side chains. The resulting graft copolymer contains dual functionality, namely both pH responsive free amino groups, with electrostatic complexation/coordination properties, and thermoresponsive PNIPAM side chains. Particle size measurements via dynamic light scattering (DLS) were used to study the thermoresponsive behavior of the Chit-g-PNIPAM copolymer. Thermal properties examined by TGA showed that, by the grafting modification with PNIPAM, the Chit structure became more thermally stable. The lower critical solution temperature (LCST) of the copolymer solution was determined by DLS measurements at 25-45 °C. Furthermore, dynamic and electrophoretic light scattering measurements demonstrated that the Chit-g-PNIPAM thermoresponsive copolymer is suitable of binding DNA molecules and forms nanosized polyplexes at different amino to phosphate groups ratios, with potential application as gene delivery systems.