| As a kind of natural polysaccharide,sodium alginate is widely used in fields like textile,agriculture,food and cosmetic industies for its fine biocompatibility,good biodegradability and low cost.The first aim of this study was to examine the ability of HM-alginate to work as an emulsifier.Then,sodium alginate was modified using dodecenyl succinic anhydride under neutral pH and 30~oC to acquire dodecenyl modified alginate(DMA).The colloidal characteristics,solubilization effect towards hydrophobic drugs and the ability to stabilize oil-in-water emulsion of DMA was studied through surface tension,viscosity,Zeta potential,particle size and interfacial tension measurements.The results are as follows:1.HM-alginate was able to reduce the interfacial tension between oil and water effectively.200 s after the injection of oil into water phase,the interfacial tension at the interface was lowered from 25.0 mN/m to 12.1 mN/m,which was about 51.6%lower.The interfacial tension at pH=4.0 didn’t differ much from that at neutral pH.However,the interfacial tension was lowered to 4.8 mN/m at pH=10.0.2.HM-alginate solution was able to stabilize 1:9 oil-in-water emulsion for up to15 days.When the emulsion was stabilized under the pH of 4.0,the properties of the emulsion didn’t differ much from the neutral condition and could also be stabilized for15 days.When the emulsion was stabilized under the pH of 10.0,the second emulsifier was brought to the system due to the alkaline condition,resulting in uneven distribution of the particle size.In this system,small particle ablated while large particle grew,and that boosted the aggregation of drops so the stability was relatively poor.3.The addition of NaCl increased the viscosity of the emulsion,reduced the zeta potential of the emulsion and the particle size of the emulsion droplets,which generally reduced the stability of the emulsion.When the salt content was 0.5%,the emulsion could be stored for 10 days,and when the salt content was 0.9%,the emulsion could be stored for 7 days.4.Sodium alginate was hydrophobically modified under neutral pH condition with dodecenyl succinic anhydride to obtain the amphiphilic polymer dodecenyl modified alginate(DMA).The modifying process needed low reaction temperature(30~oC),reduced difference between product batches,and did less corrosion of the reactor.The grafting ratio was characterized by nuclear magnetic resonance spectroscopy,which was about 9.83%.5.DMA is surface-active,and could form core-shell structured micelle in aqueous solution.The critical micelle concentration was about 0.70 mg/mL with the surface tension being at around 33.0 mN/m.Like sodium alginate solution,the DMA aqueous solution exhibited a thinning behavior when subjected to shearing force,and both of them were pseudoplastic fluid.Due to the fact that micelles were formed in aqueous solution,the flow resistance was lowered and the viscosity of the DMA aqueous solution is significantly lower than that of the alginate solution.6.The core of micelles formed in DMA solution offers a hydrophobic environment for insoluble drugs like Sudan IV and clofazimine to stay.The concentrations of Sudan IV and clofazimine in 3.0 mg/mL DMA aqueous solution were 20.7 times and 14.9times higher than that of the alginate solution at the same concentration.7.10.0 mg/mL DMA aqueous solution was able to stabilize the 1:9 peanut oil-in-water emulsion and 1:9 petroleum ether-in-water emulsion for 7 days.DMA can adsorb at the interface of water and oil,stretching the long hydrophobic chain into the oil phase,thereby significantly reducing the interfacial tension between the two phases.Even at low concentration levels,DMA molecules have a high efficiency of reducing interfacial tension. |
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