No abstract

A green sustained delivery biomaterial was prepared to encapsulate dimethyl fumarate (DMF) by an emulsion−cross-linking method for sustained release. The average size of the microspheres was 20−150 μm. The highest encapsulation efficiency and loading efficiency were 85.7 and 13.2%, respectively. The release of DMF in phosphate buffer saline followed a Fickian diffusion. In addition, the results of inhibition zone showed that DMF-loaded microspheres exhibited antimicrobial and antifungal properties much better than those of CS microspheres. Furthermore, weight loss of treated fruit was reduced insignificantly, and storage time was extended with the stable quality of litchi as compared with that of the control group. Thus, the microspheres were synthesized successfully as a sustained delivery system for DMF, which might have broad prospect and development value in preservation of fruits and vegetables.

The aim of the present work was to investigate a new use of chitosan in the modification of calcium carbonate (CaCO 3 ) particles in order to confer specific antibacterial functionality to the particles. Adipic acid was used to introduce carboxyl groups onto the surface of CaCO 3 particles. CaCO 3 particles double-coated with chitosan-adipic acid (abbreviated as CAC) were prepared through the ionic interaction between the 2 site amino group of chitosan and the carboxyl group of adipic acid. The structure of CAC was characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The zeta potential and contact angle of CAC were studied to evaluate particle interfacial properties. FTIR and TGA analyses showed that chitosan and adipic acid on CAC were combined through electrostatic interactions. When the chitosan concentration was more than 5%, the surface of the CaCO 3 particles were coated completely. When chitosan was applied at a 9% concentration to make CAC, the zeta potential increased from -27.58 mV for unmodified particles to +13.11 mV for CAC due to the increased positive charge from chitosan. In a similar way, the specific surface area increased from 2.846 m 2 /g to 4.709 m 2 /g, the average particle size decreased from 11.21 μm to 7.49 μm, and the contact angle increased from 0°to 87°. CAC had antibacterial capacity when evaluated with E. coli and S. aureus. The approach in this study provides a method for fabricating chitosan-adipic acid-modified CaCO 3 particles, an antibacterial filler for potential applications.