The rheological behaviour and drug-delivery property of chitosan/rectorite nanocomposites

The rheological behaviour of the nanocomposites based on chitosan (CS) and unmodified rectorite (REC) were first evaluated. The nanocomposites showed a low shear-rate non-Newtonian viscosity and a rapid shear-thinning behaviour. The zero shear rate viscosity and the storage and loss moduli for the nanocomposites displayed a monotonic increase with increasing REC content in comparison with pure CS. The results implied the presence of electrostatic and hydrogen-bonding interaction between CS and REC, which was corroborated by the SEM images and FT-IR analysis. Then CS beads and CS/REC nanocomposite beads were prepared via the cross-linking interaction of sodium tripolyphosphate and CS, SEM images indicated that the nanocomposite beads had more compact surface and internal structure than those of CS beads. The swelling degree of the nanocomposite beads in 0.9% (w/v) saline was only about 15%, while that of CS beads was 30%. The nanocomposite beads released the drug continuously; in the given 6 days the minimum cumulative release only reached 51.4%, much lower than that of pure CS beads (72.1%). Therefore, CS/REC nanocomposites are more suitable to apply as drug carrier than pure CS.