Preparation of polypyrrole/chitosan-sodium alginate composite microspheres and their slow-release properties

The development of novel drug controlled release composite materials is of great significance in the fields of medicine and agriculture. Using chitosan and sodium alginate (CS-Alg) gel network as carrier, PPy/CS-Alg composite slow-release material was prepared by in-situ oxidation of polypyrrole (PPy). The microstructure, structure composition and photothermal conversion properties were studied by SEM, FTIR, XPS and UV-vis-NIR. Indolebutyric acid (IBA) was used as a model drug molecule to study its sustained release performance. The results show that the porous morphology of PPy/CS-Alg microspheres is conducive to the loading and release of IBA. The PPy oxidized state formed by in-situ oxidation can be slowly reduced in the CS-Alg gel network, and changes from a positive state to an uncharged state. As a result, IBA can be slowly released from the gel network of PPy/CS-Alg microspheres, with the long-term release rate of 56.12%. In addition, the temperature of PPy/CS-Alg microspheres under simulated sunlight can rise from 26℃ to 39℃ based on the photothermal effect of PPy, which is conducive to the formation of temperature gradients inside and outside the microspheres and further enhancing the slow-release of IBA. The controlled release material of auxin IBA based on the slow reduction and photothermal effect of PPy has broad application prospects in the agricultural field.