SYNTHESIS AND CHARACTERIZATION OF A CHITOSAN DERIVATIVE FOR THE PREPARATION OF NANOPARTICLES

N-trimethyl chitosan (TMC) is a partially N-chitosan quaternary derivative readily soluble at physiological pH, with mucoadhesive properties, high biocompatibility and biodegradability. The aim of this work is to obtain TMC with different degrees of quaternization, slightly modifying the synthetic procedures reported in literature [1]. We performed the methylation reaction with CH3I in basic medium, and the degree of quaternization was modified increasing the reaction time and steps. Appropriately quaternized TMC was used to prepare nanoparticles drug delivery systems, suitable to be administered orally, ocularly or parenterally. TMC derivatives were characterized by means of spectroscopic methods (I.R and 1H- NMR) and XRD. Water dispersions of TMC were submitted to physical-chemical analyses, such as pH, rheological and evaporation- freezing assays, and stability studies. TMC nanoparticles were prepared by ionotropic gelation technique with tripolyphosphate (TPP). Preliminary morphological examination of the nanoparticles was performed by scanning electron microscopy (SEM). The size and zeta potential of the TMC nanoparticles were measured with a Malvern Zetasizer Nano. The particle-size distribution of the nanoparticles is reported as a polydispersity index (PDI). 1H-NMR studies (performed on a Varian 500MHz spectrophotometer) confirmed that TMC derivatives with different degrees of quaternization were obtained and these derivatives were suitable for different routes of administration. Moreover TMC dispersions showed higher stability if compared with the corresponding chitosan dispersions. As a matter of fact apparent viscosity data of dispersions remain relatively unchanged over time and the good stability of the water solutions was confirmed by 1H- NMR spectra. Finally TMC nanoparticles exhibit good PDI values and are stable over time. [1] Wang et al, Int J Pharm 386 (2010) 249-255.