Emulsifying properties and degradation characteristics of bioresorbable polymeric emulsifiers in aqueous solution and oil-in-water emulsion

Three amphiphilic bioresorbable copolymers derived from lactide (LA), ε-caprolatcone (CL) and poly(ethylene glycol) (PEG) were investigated for their emulsifying properties and degradation characteristics. Polymers consisted of 80 wt% hydrophilic PEG block and 20 wt% lipophilic PLA, PCL, PLACL block were synthesized by ring-opening polymerization of LA and/or CL in the presence of monomethoxy PEG. By possessing similar hydrophilic-lipophilic balance (HLB) values, these polymeric emulsifiers have an equivalent ability to stabilize squalane/water interfaces during emulsification. Degradation of polymers in aqueous solution and within emulsion was carried out in water at 37 °C selected to mimic the human body conditions. Our results demonstrated that the degradability intrinsic to each polymer is the predominant cause of destroying the emulsion. Moreover, polymer matrices within the emulsion exhibited lower degradation rates than the corresponding polymers in aqueous solution. These features are of great interest in pharmaceutical applications, especially for the design of sustained delivery systems.

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