Study On Microsphere Of Chitosan Encapsulating Dimethyl Fumarate And Its Application For Litchi

In this study, a green sustained release microsphere was prepared to encapsulate dimethyl fumarate (DMF) by an emulsion-cross-linking method for sustained release. The morphology and structure of the microspheres were characterized by laser particle size analyzer, scanning election microscopy (SEM), Differential scanning calorimetry (DSC), X-Ray diffraction (XRD) and fourier transform infrared spectroscopy (FT-IR). The sustained release of DMF encapsulated in microspheres was analysed in phosphate buffer solution with different pH, and the release kinetics was also studied. The antimicrobial and antifungal properties of microspheres were studied by using the colony counting method. And its application for litchi preservation was also studied. The results were shown in the below:1. The results of DSC, XRD and FT-IR showed that DMF successfully encapsulated in chitosan microspheres. The crystallization degree was reduced after vanillin crosslinked with chitosan, but DMF did not change the amorphous phase property of chitosan microspheres. The absorption peak of the amide bond for crosslinked microspheres was found, indicating that the Schiff base reaction may occur between aldehyde groups of vanillin and amino groups of chitosan. The microspheres were heterogeneous in size from 20 to 150 μm. The highest encapsulation efficiency and loading efficiency were 85.7% and 13.2%, respectively.2. Chitosan microspheres allowed the sustained release of DMF in a long time, which indicated good release property. The release percentage of DMF was up to 89.8%,76.7% and 28.6% within 15 days in PBS buffer with pH 5.3, 7.4 and 10.7, respectively. Base on correlating the sustained release profiles with five different common kinetic models, it can be found that the Weibull or Ritger-Peppas model was the optimal model for describing DMF release kinetics on all pH values in PBS solution. And the Fickian diffusion was the major release mechanism for the sustaibed release of DMF from microspheres.3. The antibacterial performance test shown that the antimicrobial and antifungal properties of microspheres were improved after encapsulating DMF. After 15 days, the diameters of inhibition zone of DMF-loaded microspheres on E. coli, S. aureus and Litchi separated bacterium were 18.5±1.12 mm,14.6± 0.93 mm and 20.4 ±0.86 mm, respectively. But the diameters of inhibition zone of chitosan microspheres were only 1.32±0.03 mm,1.04±0.02mm and 0.57± 0.06 mm. The results proved that DMF-loaded microspheres exhibited long-lasting antimicrobial activity.4. The litchis after treatment with DMF-loaded microspheres were freshness and still with good nutritional value store under room temperature (25-28℃) for 8 days, while the control group only for 4 days. The weight loss of treated with DMF-loaded microspheres was the lowest, the concentration of total soluble solid and vitamin C content were highest. However, the effect of preservation with the control group was the worst.The results showed that the DMF-loaded microspheres prepared in this research are expected to be applied in the preservation for subtropical fruits and other fruits and vegetables.