| Volatile oil is a kind of volatile and strong aroma compound extracted from aromatic Chinese medicine and other plants.It has significant antibacterial,anti-inflammatory,antioxidant,antiviral and other pharmacological activities.It is widely used in medicine,food,agriculture,cosmetics and other industries.However,volatile oils are easily volatile,unstable,and are highly susceptible to external factors(such as light,temperature,oxygen and humidity,etc.)causing oxidative degradation and isomerization reactions.In addition,poor water solubility of volatile oils also reduces their bioavailability and absorption in vivo.These make the application of volatile oils in the pharmaceutical industry a great challenge.Therefore,it is urgent to improve the stability of volatile oils and protect their biological activity through new preparation techniques.Pickering emulsion(PE)provides a new method to improve the water dispersibility and stability of volatile oil.Volatile oil from Mosla chinensis Maxim.cv.Jiangxiangru(MJO)has significant antibacterial and anti-inflammatory effects.In this study,MJO was used as a model drug,and food-grade cationic surfactant Lauroyl arginate ethyl(LAE)was used as a modifier to modify nano-silica in situ to obtain partially hydrophobic solid particles.Pickering emulsification technology was innovatively used to emulsify and encapsulate MJO into a stable oil-in-water Pickering emulsion(MJO-PE).The antibacterial properties and mechanisms of MJO-PE and its anti-ulcerative colitis efficacy were systematically evaluated.In addition,in order to solve the problems of inconvenient storage of emulsion and further processing of preparations,MJO-PE was spary-dried into microcapsule powder by spray-drying technology and used as an intermediate for tablet application.(1)Preparation and characterization of modified nano silicaThe hydrophobic modified nano-silica dispersion of LAE was prepared by high pressure homogenization method.The in-situ surface modification was realized by the electrostatic interaction between the negatively charged hydrophilic surface of nano-silica and the positively charged head group of LAE.The effects of different contents of LAE on the particle size,Zeta potential,water phase dispersion,surface tension and contact angle of modified nano-silica were investigated,and the binding mechanism of the two was analyzed.The results showed that under the low content of LAE(0.002 ～ 0.1wt %),the surface of nano-silica was gradually covered by LAE monolayer under the control of electrostatic force,the hydrophobicity increased,the surface tension decreased rapidly,and the surface potential was gradually neutralized(-28.63 ± 0.57 ～-9.46 ± 0.35 mV).At this time,the particle size was low(138.27 ±1.08 ～ 521.33 ± 5.06 nm),and the water phase dispersion was good.When the content of LAE was 0.1 wt %,the contact angle of modified nano-silica was the largest(40.8 °),and the hydrophobicity was the best,which was suitable for stabilizing oil-in-water emulsion.The modified nano-silica was characterized by Fourier transform infrared spectroscopy(FT-IR),Thermogravimetric analysis(TGA),Scanning electron microscope(SEM)and Transmission electron microscope(TEM).When the content of LAE is excessive(0.14 ～ 0.4 wt %),the excessive LAE molecules may self-assemble on the surface of nano-silica,resulting in a decrease in hydrophobicity.The surface tension gradually reaches a plateau,and the Zeta potential gradually approaches zero(-2.59 ± 0.08 ～ 1.51 ± 0.07 mV).The LAE alkyl chain begins to bridge,and the LAE hydrophobically modified nano-silica dispersion is prepared by high-pressure homogenization.The in-situ surface modification is achieved by the electrostatic interaction between the negatively charged hydrophilic surface of nano-silica and the positively charged head group of LAE.The effects of different contents of LAE on the particle size,Zeta potential,water phase dispersion,surface tension and contact angle of modified nano-silica were investigated,and the junction of the two was analyzed.(2)Preparation and characterization of MJO-PE stabilized by modified nano-silicaMJO-PE was prepared by high pressure homogenization method with LAE modified nano-silica as stabilizer.The effect of LAE content on the stability of Pickering emulsion was analyzed by Zeta potential,rheology,standing stability,centrifugal acceleration stability and Turbiscan Lab stability.The results showed that the stability of emulsion increased first and then decreased with the increase of LAE content.The stability of LAE at 0.1wt % content reached the highest,and the TSI was0.62.In addition,the effects of nano-silica content,oil phase composition,oil phase volume fraction and homogenization pressure on Pickering emulsion were investigated by static stability,centrifugal acceleration stability and Turbiscan Lab stability analysis.The optimum formulation and process were determined as follows:0.1 wt % LAE-2 wt % nano-silica as stabilizer,phase volume fraction of 15 %,oil phase composition of MJO: soybean oil = 8: 2(V / V),homogenization at 200,400,600 and 800 bar for 60 cycles,respectively.The pH and temperature stability of the best Pickering emulsion were investigated.The results showed that the Pickering emulsion was not unstable at 80 °C,and the pH was higher than 10,which was not conducive to the stability of Pickering emulsion.Optical microscopy and laser confocal microscopy showed that the modified nano-silica formed an interface film on the surface of the droplets,and a three-dimensional network structure was formed between the droplets,which hindered the migration and merger of the droplets and improved the stability of the Pickering emulsion.(3)Evaluation of antibacterial and anti-ulcerative colitis efficacy of MJO-PE stabilized by modified nano-silicaThe antibacterial activity of MJO-PE was evaluated by minimal inhibitory concentration(MIC)and minimal bactericidal concentration(MBC)values.The results showed that MJO-PE had strong antibacterial activity against Gram-negative bacteria(Escherichia coli and Pseudomonas aeruginosa)and Gram-positive bacteria(Staphylococcus aureus).The MIC were 0.45,1.2 and 0.6 μL/mL,and the MBCs were 0.45,4.8 and 0.6μL/mL,respectively.The antibacterial effect on Escherichia coli and Staphylococcus aureus was higher than that of MJO,indicating that the antibacterial activity of MJO was enhanced after PE emulsification and encapsulation.The results of bacterial cell membrane morphology observation,nucleic acid and MDA content determination showed that MJO-PE killed bacteria by destroying the bacterial cell membrane structure and causing the outflow of intracellular macromolecules.Through mouse ulcerative colitis(Ulcerative colitis;UC)model was used to evaluate the anti-inflammatory effect of MJO-PE.The results showed that MJO-PE enhanced SOD activity,down-regulated NO production,reduced lipid peroxidation,reduced oxidative stress injury,and inhibited the levels of pro-inflammatory factors such as TNF-α and IL-1β to achieve significant anti-inflammatory activity.(4)Study on MJO solid preparation based on Pickering emulsification technologyMJO-PE was dried into volatile oil microcapsules by spray drying technology,and spray drying protective agent was added before drying to avoid emulsion demulsification during spray drying.The results showed that the microcapsules had the highest recovery rate(44.95 %)and the strongest protective effect of volatile oil(the retention rate was 98.54 ± 1.11 %).The surface morphology analysis showed that the microcapsules had regular shape and regular surface.TGA results showed that the thermal stability of volatile oil was significantly improved after encapsulation.The stability analysis results of microcapsules stored at different water activities for one month showed that the microcapsules with 100 % inulin as the protective agent maintained macroscopic stability when the water activity was lower than 0.432.X-ray diffraction analysis of microstructure and SEM morphology observation found that it can still maintain the amorphous structure and cystic structure.After the water activity reached 0.689,the microcapsules agglomerated,the microcapsule matrix began to undergo crystal transformation,the structure collapsed,and the cystic structure disappeared,which provided guidance for the storage of Chinese medicine volatile oil microcapsules.The tablet compression suitability of MJO-PE microcapsule powder was studied by direct powder compression technology.The powder fluidity was investigated by the angle of repose.The amount of colloidal silicon dioxide needed for the flow aid was 1.76 %,and the angle of repose was 34.77 ± 1.42 °.The compressibility of tablets was investigated by disintegration and friability.The results showed that 39.10 % microcrystalline cellulose(MCC)PH 302 as filler,9.77 %Polyvinylpolypyrrolidone(PVPP)was used as a disintegrating agent,and the hardness was 21.37 ± 0.99 N.The tablets could rapidly disintegrate into fine particles within 2 min and 40 s under the requirements of friability,indicating that MJO could be successfully prepared into MJO tablets based on Pickering emulsification technology to meet different clinical needs. |
PDF Full Text Request