Effect of molecular weight and pH on the self-assembly microstructural and emulsification of amphiphilic sodium alginate colloid particles

Abstract Biopolymer-based Pickering emulsions have attracted increasing interest in research areas including food, pharmaceutics and drug delivery. However, understanding of self-assembly behavior from the dedicate structure of stabilizers has not been well explored yet. In this work, we proposed to investigate how molecular weight affect the self-assembly behavior and to explore the potential of biopolymer colloidal particle-stabilized Pickering emulsion for controlling release of hydrophobic drugs. Amphiphilic sodium alginate derivatives (Ugi-Alg) with three molecular weights (685 kDa, 307 kDa and 48 kDa) were successfully incorporated with a hydrophobic group. Based on the characterizations of morphology and rheology behavior, the high-molecular-weight derivatives (H-Ugi-Alg) can form a compact micelle structure in aqueous solution. Emulsions stabilized by H-Ugi-Alg exhibited a higher stability and stronger viscoelasticity than those using Ugi-Alg with a lower molecular weight. In addition to the entangled polymer chains caused by higher molecular weight and hydrophobic association, the partially protonated carboxyl groups reduced electrostatic repulsion at pH = 4.2 also facilitate the formation of compact micelle structure. Approximately 78.6% of the encapsulated curcumin released from the emulsion stabilized by H-Ugi-Alg, which exhibits a similar release efficiency compared with the nanoparticle-stabilized Pickering emulsions.