Particle agglomeration of chitosan–magnesium aluminum silicate nanocomposites for direct compression tablets
Exfoliated nanocomposites of chitosan-magnesium aluminum silicate (CS-MAS) particles are characterized by good compressibility but poor flowability. Thus, the aims of this study were to investigate agglomerates of CS-MAS nanocomposites prepared using the agglomerating agents water, ethanol, or polyvinylpyrrolidone (PVP) for flowability enhancement and to evaluate the agglomerates obtained as direct compression fillers for tablets. The results showed that the addition of agglomerating agents did not affect crystallinity, but slightly influenced thermal behavior of the CS-MAS nanocomposites. The agglomerates prepared using water were larger than those prepared using 95% ethanol because high swelling of the layer of chitosonium acetate occurred, allowing formation of solid bridges and capillary force between particles, leading to higher flowability and particle strength. Incorporation of PVP resulted in larger agglomerates with good flowability and high strength due to the binder hardening mechanism. The tablets prepared from agglomerates using water showed lower hardness, shorter disintegration times and faster drug release than those using 95% ethanol. In contrast, greater hardness and more prolonged drug release were obtained from the tablets prepared from agglomerates using PVP. Additionally, the agglomerates of CS-MAS nanocomposites showed good carrying capacity and provided desirable characteristics of direct compression tablets.
Size enlargement of CS-MAS nanocomposites for flowability im- provement was successfully achieved by using agglomerating agents such as water, ethanol and PVP. The incorporation of an agglomerating agent slightly affects thermal behavior of the CS-MAS nano composites, but crystallinity of the nanocomposites is unchanged. Water shows good efficiency to form larger agglomerates compared with 95% ethanol because it can strongly induce the swelling layer of chitosonium acetate, leading to solid bridges and capillary forces between particles. This leads to good flowability and higher strength of the agglomerates prepared using water. The addition of PVP results in larger agglomer- ates that display good flowability and high strength due to the binder hardening mechanism. The tablets prepared from agglomerates using water show a fast release of drug because of low hardness and short disintegration times, whereas the agglomerates prepared using 95% ethanol yield sustained-release tablets. Moreover, higher hardness and more prolonged drug release occur in the tablets prepared from ag- glomerates prepared using PVP. Furthermore, the agglomerates ob- tained show a good carrying capacity and possess desirable character- istics for direct compression, which are dependent upon the type of agglomeration agent. These findings suggest that agglomerates of CS- MAS nanocomposites demonstrate strong potential for use as direct compression fillers for tablets.
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