Construction Of Amino-mesoporous Silica Loaded Tea Tree Oil System And Its Antibacterial Properties

Tea Tree oil（TTO）,as a broad-spectrum antimicrobial oil,has become a research hotspot in the field of biological antimicrobial agents.However,TTO is easy to volatilize,and it is difficult to preserve and affects the efficacy.In an effort to improve the continuous antibacterial properties of TTO,three kinds of functionalized mesoporous silica were used as carriers to prepare the TTO powders for preservation.The carriers are polyacrylic acid（PAA）chemically modified aminated mesoporous silica（NH₂-M41S）,abietic acid sodium salt（RA-Na）modified NH₂-M41 S and one-pot synthesis of Mesoporous silica-coated TTO.A novel sustained-release preparation was developed by the interaction between the carrier and the TTO.The common Escherichia coli（E.coli）and Staphylococcus aureus（S.aureus）were selected as test bacteria to study the sustained-release and antibacterial properties of the preparation system.The antibacterial mechanism of TTO was discussed,and a new preparation method was provided for the application of essential oil antibacterial agents.The research contents and results were listed as follows:The PAA modified NH₂-M41S（PAA-NH₂-M41S）has a hexagonal shape,and the highest loading rate of the physical loading TTO reaches 56%.With the increase of the molecular weight of PAA,the release rate of TTO was reduced from 100% to 50% with sustained release at 40℃ for 10 h.The release process of TTO could be explained by the Korsmeyer-Peppas and the First-order model.The TTO in this system exhibited a stable and sustained antibacterial effect even after 50 days in a natural environment.The antibacterial rate of the TTO to S.aureus was 100% at 0.6 mg/mL and to E.coli was 100% at 1.2 mg/mL.TTO can increase cell permeability by disrupting bacterial cell membranes.In addition,TTO also caused a decrease in the OD value of the bacterial solution,leakage of nucleic acid contents,and increased electrical conductivity,which inhibited cell growth and caused bacterial death.The rosin-acidified mesoporous silica supports（RA-Na@NH₂-M41S-1 and RA-Na@NH₂-M41S-2）were prepared by introducing RA-Na into NH₂-M41 S through chemical and physical modification.And the carrier is hexagonal rod-like structure.The loading ratio of M41 S to TTO was increased from 64% to 69% due to the modification of RA-Na.The minimum cumulative release rate of the TTO in RA-Na@NH₂-M41S-1 was 46% at a constant temperature of 40 °C for 10 h,which was lower than that of the TTO in RA-Na@NH₂-M41S-2,and the sustained release behavior of TTO was consistent with the Korsmeyer-Peppas kinetic model.RA-Na@NH₂-M41 S and TTO can produce synergistic antibacterial effect on S.aureus.In this system,the MBC of TTO on S.aureus was reduced from 0.4 mg / mL to 0.3 mg/mL and the MIC was reduced from 0.2 mg/mL to 0.15 mg/mL.The MBC of TTO on E.coli was 0.6 mg/mL,and the MIC was 0.3 mg/mL.The TTO in this system exhibited a stable and sustained antibacterial effect even after 43 days in a natural environment.There was no significant difference in bacteriostatic effect between chemically and physically modified carriers.After E.coli and S.aureus treated with TTO,there were problems such as cell deformation,cell membrane destruction,low OD value of bacterial solution,high conductivity and high nucleic acid content,which caused bacterial death.The mesoporous silica carrier synthesized by one-pot method（M41S@TTO-1,M41S@TTO-2 and M41S@TTO-3）showed a spherical appearance with particle sizes of 790⁸10 nm.The loading capacity of M41 S to TTO was 10%,11% and 12%,respectively.The release rate of TTO was reduced from 96% to 20% with sustained release at 60℃ for 8 h.There is an interaction between CTAB and TTO.With the increase of the proportion of CTAB,the cumulative release rate of TTO in this system decreased from 69% to 20%.The release process of TTO could be explained by the Zero-Order model and the Logistic model.CTAB could inhibited the release of TTO,and when the dosage of CTAB reached 1.5 g,it had synergistic antibacterial effect with TTO.In addition,the MBC of TTO on E.coli and S.aureus was reduced to 0.06 mg/mL,the MIC was reduced to 0.03 mg/mL.The TTO in this system exhibited a stable and sustained antibacterial effect even after 45 days in a natural environment.The OD value of bacterial fluid decreased after TTO treatment.The bacterial cell membrane is destroyed,causing the bacteria to lose their stable internal environment and die.