Carboxymethyl konjac glucomannan coating on multilayered emulsions for improved bioavailability and targeted delivery of curcumin.

Curcumin was entrapped in multilayered emulsions to increase its stability and bioavailability. Curcumin emulsion stabilized by whey protein isolate (WPI) was coated with chitosan (CHI) or carboxymethyl konjac glucomannan (CMKGM) alone to form secondary emulsions and their combination in sequence to form the tertiary emulsion, in which, the polyelectrolyte concentrations were 1.0% WPI for the primary emulsion, 0.4% CMKGM for the secondary emulsion -CMKGM, 0.2% CHI for the secondary emulsion -CHI, and 0.1% CMKGM for the tertiary emulsion. The characteristics of the emulsions, including their particle size, ζ potential, microstructure, creaming stability, and biopolymer distribution, were investigated and their colon-targeted delivery potential was evaluated through both in vitro and in vivo studies as well. The curcumin-loaded secondary and tertiary emulsions were stable with a narrow size distribution and were generated by layer-by-layer assembly according to confocal laser scanning microscope observation. When CMKGM was located at the outermost layer, the corresponding secondary and tertiary emulsions showed a greatly reduced release of curcumin in the simulated gastric fluid, but exhibited increased release in the ß-mannanase-containing simulated colonic fluid. In vivo evaluation in mice demonstrated that the bioavailability of curcumin in the CMKGM-coated secondary and tertiary emulsions was increased by about 4 folds compared with that of free curcumin and curcumin could be released in a sustainable manner. These results demonstrated that multilayered emulsions coated with CMKGM could promote curcumin absorption in the gastrointestinal tract and hence is a promising colon-targeted delivery system for curcumin.

Preparation and properties of chitosan-based microspheres by spray drying.

In this study, the chitosan-based release microspheres were prepared by spray drying method. Chitosan was used as the carrier material, and Panax notoginseng extract, Codonopsis extract, and Atractylodes extract (the mass ratio was 2:7:5) were active substance. The spray drying preparation process of microsphere was optimized by single factor experiment and L9 (34) orthogonal design. Drug loading (DL), particle size, and sustained release performance of microspheres were investigated. The mass fraction of chitosan was 1.5%, the mass ratio of drug to chitosan was 1:3, the inlet air temperature was 130°C, and the injection rate was 400 ml/hr. The chitosan-based microspheres prepared under the above conditions had a smooth surface, and the DL was 23.87 ± 0.93%; the average particle diameter was 10.27 ± 1.05 µm, and the encapsulation efficiency (EE) of the microspheres was 91.28 ± 1.04%. The preparation process of chitosan-based drug microsphere prepared by spray drying method was simple and stable. The prepared microspheres in this paper showed a sustained release effect in vitro.

Complex coacervation of carboxymethyl konjac glucomannan and chitosan and coacervate characterization.

Carboxymethyl konjac glucomannan (CMKGM) shows potential in the construction of colon-targeted delivery systems through electrostatic interaction-based techniques. Its coacervation with chitosan (CHI) was investigated as a function of degree of substitution (DS). CMKGMs displayed the same optimum coacervation conditions of pH 6.5 and mass ratio 1:1 with CHI, but the coacervate yield was positively related to their DS. The coacervation was weakened by the presence of NaCl, but was not affected in temperatures 25-75 °C and total biopolymer concentrations 0.05-0.15% (w/v). Both electrostatic interaction and hydrogen bonding were involved in the coacervation and a higher DS contributed a denser network structure, a smaller particle size, and greater elasticity. The coacervates maintained their structures in simulated gastrointestinal fluids, but could be degraded by the ß-mannanase in simulated colonic fluid. Hence, CMKGMs could be used in colon-targeted and enzyme-triggered delivery systems and the delivery performance could be tailored by varying their DS.