Exploration of the formative mechanisms of colon-targeting composite particles of natural products prepared via mechanical dry particle coating

Mechanical dry particle coating, coating fine particles in waterless environment, possesses great potential to prepare colon-targeting composite particles of natural products. However, host and guest particles physical properties may impact its surface coverage efficiency. This study selected 10 natural products and 4 colon-targeting excipients as host and guest particles, respectively, and characterized 13 physical properties. Using planetary ball mill, 40 composite particles were prepared and evaluated for SEM, infrared features, and in vitro release. Grey relation analysis, served as the core method, identified critical materials attributes of host and guest particle physical properties affecting the surface coverage and colon-targeting of composite particles. Results indicated that only 9 composite particles achieved favorable surface coverage and in vitro colon-targeting, like guar gum coated total saponins of Pulsatilla with respective surface area coverage and maximum cumulative drug release in colon of 76.71 % and 83.55 %, and revealed the prerequisite of well-covered structure of composite particle for colon-targeting. Identified critical material attributes, including particle size and specific surface area, etc., affected surface coverage efficiency through influencing interparticle forces for adhesion, particularly in van der Waals forces. Moreover, guest particle with favorable hydrophobicity may form a hydrophobic layer, preventing host particles from dissolving under well-covered structure.