Influence of photo-cross-linking on emulsifying performance of the self-assemblies of poly(7-(4-vinylbenzyloxyl)-4-methylcoumarin-co-acrylic acid).

Polymeric micelles could be used as model polymeric particulate emulsifiers to elucidate the correlation between the micellar structure and their emulsifying performance. Photo-cross-linkable and pH-responsive micelles were prepared with amphiphilic random copolymers, poly(7-(4-vinylbenzyloxyl)-4-methylcoumarin-co-acrylic acid) (PVMAA), via the self-assembly in selective-solvent DMF/H2O and then used as polymeric particulate emulsifiers to stabilize toluene-in-water emulsions. Primary micelles, based on PVMAA with 12 mol % of hydrophobic composition, were chosen as model to investigate the influence of photo-cross-linking on the emulsifying performance. The larger shrinkage degree by photo-cross-linking (SDC) the micelles have, the lower emulsifying efficiency the micelles exhibit. Furthermore, the structural transitions of micelles with SDC of 0% and 95% in response to pH change were comparatively confirmed by a combination of electrophoresis, dynamic light scattering (DLS), and transmission electron microscopy (TEM). The micelles of various states, manipulated by photo-cross-linking and pH changes, were used as emulsifiers to stabilize toluene-in-water or styrene-in-water emulsions. For the un-cross-linked micelles, polymer chains gradually protrude from micelles with pH increasing, which benefits the increase in the emulsifying efficiency of micelles. However, as pH elevated over 8, the stability of emulsions significantly decreases due to the disintegration of micelles. On the contrary, micelles with SDC of 95% keep their structural integrity and become more rigid as pH increase, leading to lower emulsifying efficiency of micelles and worse stability of the emulsions. This paper provides a new insight into the principles governing the extremely high emulsifying efficiency of polymeric particulate emulsifiers and pH-dependent or pH-responsive properties of the formed emulsions.

Stable emulsions prepared by self-assembly of hyaluronic acid and chitosan for papain loading.

A simple, green and effective process is developed to fabricate hyaluronic acid (HA)/chitosan (CS) complex colloidal particles through electrostatic interactions. The obtained complexes can be used as biocompatible emulsifiers and novel potential carriers for papain loading. An HA/CS mass ratio of 2 is the optimal condition leading to the smallest Dh (420.9 nm). The complexes with eight different mass ratios are used to stabilize white oil/water emulsions. The structure of the complexes at the oil-water interface varies in response to the mass ratio and can be classified into two typical structures, similar to typical polymeric surfactants and solid particulate emulsifiers. Furthermore, papain is introduced into the complex systems. Formation of the papain/HA/CS complexes in a compact form can protect the enzyme. Here, a novel strategy is introduced to fabricate a biocompatible emulsion from the HA/CS complexes and demonstrate that the stable complex is a suitable enzyme delivery system.