Preparation and photo-thermal controlled release properties of nanodiamond/yeast-chitosan composite microspheres

It is important to develop high-performance functional photo-thermal materials and establish controlled drug release models for the development of intelligent transportation materials for pesticides. Herein, nanodiamond (DND) was employed to prepare novel nanodiamond/yeast-chitosan (DND/YS-CS) composite hydrogel microspheres which had a cross-linked network structure through alkali gelation method. The microstructure, mechanical resistance and photo-thermal conversion performance of the composites were investigated. Moreover, indole-3-butyric acid (IBA) was used as a model to discuss the loading and controlled drug release and reveal the photo-thermal controlled release mechanism of IBA by DND/YS-CS. The results show that the composite microspheres has good mechanical properties, and the water retention capacity of the composite microspheres with DND content of 2.0 mg/mL reached 70.5% and 74% after ultrasonication and centrifugation for 1 h, respec-tively. The maximum temperature of the composites can reach to 37.6℃ under one sunlight intensity, proving that the composites possess excellent photothermal conversion ability. The maximum adsorption of IBA is 41.73 μg/mg when the composites have a DND concentration of 1.2 mg/mL. Finally, the controled drug release pattern of the composites is in accordance with the Korsmeyer-Peppas model, which exhibits an obvious stimulus response behavior and an "on-off" pattern of drug release under light.