Abstract: A novel maleic rosin-based ester tertiary amine salt surfactant (RETAS) with three hydrophilic groups was synthesized through D-A addition reaction, acyl chlorination, esterification reaction and salt forming reaction with rosin acid as raw material. The critical micelle concentration (C_CMC) of RETAS was 0.73 mmol/L (0.50 g/L), and the corresponding surface tension at CMC (γ_CMC) was 38.58 mN/m. The RETAS was mixed with natural soapnut saponin. The best compound proportion of mixed system was obtained by determining the surface tension, emulsification property and foam property to study the synergistic effect. And the self-assembly behavior and micelle morphology of the composite system was characterized by transmission electron microscopy (TEM) and the micelle formation mechanism was speculated in detail. The results showed that the γ_CMC and C_CMC of mixtures were 37.57 mN/m and 0.40 g/L when the optimum mass ratio of RETAS/soapnut saponin was 5:5. The emulsifying properties of RETAS and saponin were only 292 s and 310 s respectively, but the emulsifying properties increased to 373 s in the optimum mass ratio. Finally, the cytotoxicity of RETAS on human colon adenocarcinoma cells (Caco-2) was investigated and it was found that it had non-toxic or low toxicity and was applied to study the drug loading properties of anticancer drug doxorubicin (DOX). The release rates of DOX on RETAS were 67% and close to 100% in pH value 7.4 and 5.0, respectively. While the release rates of DOX on the mixture were 68% and close to 90% in pH value 7.4 and 5.0. The results showed that both RETAS and mixed product could be used as the target carrier of DOX. Under simulated tumor conditions, DOX was still slowly released after 24 hours in pH=5.0.

Key words: maleic rosin, soapnut saponin, self-assemble, targeted drug delivery, sustained-release