Formation of chitosan-fucoidan nanoparticles and their electrostatic interactions: Quantitative analysis.

The stoichiometric distributions of both positive amino groups and negative sulfate ions loaded in chitosan-fucoidan nanoparticles (CFNs) were predicted quantitatively by correlating the separate yields of loaded chitosan and fucoidan, and a proposed relative charge density model (case 1). In addition, those distributions of both positive amino groups and negative sulfate ions loaded in CFNs were obtained by deriving the expression of their loaded concentrations directly from the experimental data (case 2). Both the model-prediction and experimental derivations were remarkably consistent with each other except at pH 2. The discrepancy between cases 1 and 2 at pH 2 was explained by an increase in the sulfate group loading because of the most intensive electrostatic (specific ion) interactions at pH 2. The ratio of the CFN-free net charge density shielded by counter-ions in the solution entrapped in CFNs to their counter-ion-crosslinking charge density was suggested to be a quantitative criterion for determining the size distribution of CFNs. The formation of CFNs ranked according to size was predicted well and explained reasonably by the suggested criterion, considering both the ionic strength of the entrapped solution in CFNs and the nonspecific binding (interaction) of the positive amino groups among the chitosan molecules. Furthermore, the fraction of nonspecifically-bound positive amino groups causing hysteresis was quantified from the positive net charged amino groups per unit-mass CFN. Thus, its magnitude was predicted to have a strong correlation with the CFN-preparation conditions, such as pH and fucoidan to chitosan mass ratio.

Relative charge density model on chitosan-fucoidan electrostatic interaction: qualitative approach with element analysis.

This paper proposes a relative charge density model of prepared chitosan-fucoidan nanoparticles (CFNs) to provide insight into an analysis of the ionic interactions in terms of polyelectrolyte complexes. Using the relative charge density model, the extent of the ionic interactions is predicted in terms of the pH (2 through 6) and used fucoidan to chitosan mass ratio (FCMR) (1:0.05 through 1:1), through which the formation of CFNs can be controlled to be ranked qualitatively according to size and stability. It was confirmed by the measurements of their zeta potentials and sizes and by the analysis of their decay with time. Moreover, the relative charge density model was validated to predict the isoelectric condition of a polyelectrolyte complexed suspension of CFNs. Elemental analysis with a proper mass-conversion showed that the ratio of the stoichiometric coefficients of sulfate groups to amino groups in CFNs formed were almost consistent to that of the sulfate groups to amino groups in a chitosan solution mixed with a fucoidan solution prior to the occurrence of polyelectrolyte complexation. In a pH 2-environment, there were locally intensive electrostatic interactions with a low yield to form sulfate group-rich CFNs. In contrast, in a pH 6-environment, extensive electrostatic interactions occurred to form sulfate group-poor CFNs with a high yield. In addition to the chitosan-amide groups, the separate yield-distribution of loaded chitosan indicated the possible involvement of positively charged amino groups in the electrostatic interactions among chitosan molecules.

Studies on the characteristics of drug-loaded gelatin nanoparticles prepared by nanoprecipitation.

The morphology of gelatin nanoparticles loaded with three different drugs (Tizanidine hydrochloride, Gatifloxacin and Fluconazole) and their characteristics of entrapment and release from gelatin nanoparticles were investigated by the analysis on nanoparticle size distribution, SEM and FT-IR in this study. The particles were prepared by nanoprecipitation using water and ethanol as a solvent and a nonsolvent, respectively. The exclusion of a crosslinking agent from the procedure led the system to have an irregularly-shaped morphology. Nonetheless, the uncrosslinked case of Gatifloxacin loading generally led to a more homogeneous population of nanoparticles than the uncrosslinked case of Tizanidine hydrochloride loading. No loading was achieved in the case of Fluconazole, whereas both Tizanidine hydrochloride and Gatifloxacin are observed of being capable of being loaded by nanoprecipitation. Tizanidine hydrochloride-loaded, blank and Gatifloxacin-loaded nanoparticles yielded, under crosslinked condition, 59.3, 23.1 and 10.6% of the used dried mass. The crosslinked Tizanidine hydrochloride-loaded particles showed the loading efficiency of 13.8%, which was decreased to 1.1% without crosslinking. A crosslinker such as glutaraldehyde is indispensable to enhance the Tizanidine hydrochloride-loading efficiency. To the contrary, the Gatifloxacin-loading efficiency for crosslinked ones was lower by a factor of 2-3 times than that for uncrosslinked ones. This is due to the carboxylic groups of Gatifloxacin and the aldehyde groups of glutaraldehyde competing with each other during the crosslinking process, to react with the amino groups of gelatin molecules. The loading efficiency of gelatin nanoparticles reported by other investigators greatly varies. Nevertheless, the loading efficiency reported by us is in good agreement with the drug-loading data of gelatin nanoparticles reported by other investigators. The 80% of loaded Tizanidine hydrochloride was released around 15 h after start-up of the release experiment, while the 20% of loaded Gatifloxacin was released more rapidly, as free Gatifloxacin, than the loaded Tizanidine hydrochloride and it showed the trend of sustained slow release during the remaining period of its release experiment. Furthermore, the result of comparative FT-IR analysis is consistent to that of the corresponding drug release study.