Essential Oil Loaded On Modified Mesoporous Silica And Its Sustained Release Properties

Mesoporous silica is a new type of functional material.Since the M41S series of mesoporous silica appeared in 1992,its uniform size and ordered arrangement of pores,large specific surface area,large pore volume and other structural characteristics make the material being widely concerned by researchers in the field of drug controlled release.In this field,mesoporous silica can be applied as the carrier to effectively reduce the volatilization of essential oil due to its porous structure and property of wonderful surface chemical modification.Furthermore,the modification of different chemical groups can enhance the interaction between mesoporous silica and essential oil,and thus improve both of the sustained release property and application effect.This paper is divided into two parts.In the first part,methyl eugenol,one of the sexual attractant,was used as the model essential oil.According to the molecular structure of methyl eugenol,we designed Schiff base to modify mesoporous silica.Methyl eugenol（Me）was loaded on the carriers by the post-adsorption method and the one-step method,respectively,in order to form aπ-πstacking structure.We systematically investigated the structural morphology,the sustained release properties and the sexual attraction of the material.In the second part,considering the complex composition of tea tree oil（TTO）,polymer-modified mesoporous silica was designed to adsorb tea tree oil,in order to restain the excessive volatilization speed of tea tree oil and achieve the purpose of prolonging the antibacterial property.（1）Me was loaded on schiff base modified mesoporous silica（Me-Sal-MCM,Me-Fur-MCM,and Me-Ben-MCM）by the poat-adsorption method.The above materials showed a hexagonal structure with a particle size of about 700⁸00 nm.With the modification of Sal,Fur and Ben,the loading of MCM for Me increased from 67.35%to67.89%,73.34%and 73.84%,respectively,while the final cumulative release rate decreased from 82.88%to 48.59%,56.63%and 37.21%,respectively.The release process of Me could be explained by the Korsmeyer-Peppas equation and the First-order model.（2）Me was loaded on schiff base modified mesoporous silica（Me-Sal-MSN,Me-Fur-MSN,and Me-Ben-MSN）by the one-step method.They exhibited a spherical appearance with a particle size of approximately 35⁴0 nm.There is an interaction between Me and schiff base.The loading of MSN for Me changed from 28.73%to 32.70%,14.84%and 15.88%,respectively,while the final cumulative release rate changed from 38.41%to22.06%,20.90%and 49.59%,respectively.The release process of Me could be explained by the Korsmeyer-Peppas equation and the Logistic model.The CTAB in the tunnel of MSN also decreased the release rate of Me.In comparison with the post-adsorption method,the cumulative release rates of this two types of sustained release materials did not exceed50%in 600 min,while the cumulative release rate of Me took about 389 min to reached its50%.The one-step method improved the lure efficiency for Bactrocera dorsalis of each unit of Me loaded on mesoporous silica.（3）Polyethyleneiminemodifiedmesoporoussilica（PEI600-MCMand PEI1800-MCM）showed a hexagonal structure with particle sizes of 650 nm.Although the difference in molecular weight of PEI was not significant for the loading amount of TTO,TTO,TTO-MCM,and TTO/PEI1800-MCM spent about 28 min,138 min,and 490 min in reaching the 50%cumulative release rate,respectively,while the cumulative release rate of TTO/PEI600-MCM did not exceed 50%within 750 min.The release process of TTO could be explained by the Weibull equation and the First-order model.TTO-MCM,TTO/PEI600-MCM and TTO/PEI1800-MCM reached the maximum inhibition zone at 24 h,72 h and 48 h,respectively.（4）Polyacrylicacidmodifiedmesoporoussilica（PAA/NH₂-MCM-2and PAA/NH₂-MCM-8）showed a hexagonal structure with particle sizes of 1000 nm.PAA is electrostatically modified to the surface of NH₂-MCM.Although the difference in modification amount of PAA was not significant for the loading amount of TTO,TTO-PAA/NH₂-MCM-2 took about 1377 min to reach the 50%cumulative release rate,while the cumulative release rate of and TTO-PAA/NH₂-MCM-8 did not exceed 50%within 1500 min.The release process of TTO could be explained by the Korsmeyer-Peppas equation.TTO-PAA/NH₂-MCM-2 and TTO-PAA/NH₂-MCM-8 obtained the maximum inhibition zone at 48 h and 72 h,respectively,with the smallest number of colonies of Escherichia coli.