Controlling molecular orientations of hydrogels in oil-drug@hydrogel particle delivery systems for pH-selective/sustained release and stabilization of bioactive drugs

Abstract

As potential oral and topical drug delivery applications, we fabricate oil-drug@molecularly-oriented hydrogel shells particles with regulated molecular orientation, for improved loading efficiencies, controlled and pH-specific releases, and anti-denaturation of hydrophilic drugs. The hydrogel shell is made with a natural polymer (alginate or curdlan) and Ca2+, and features oriented/crystallized structures. With a simple drop-dripping device, an optimum condition is established to encapsulate an oil-hydrophilic drug mixture with these shells and to manipulate molecular orientation/crystal structures of hydrogel shells. As a result, drug (arbutin) loading efficiencies are increased to 90% in the particles. In addition, depending on the types of physicochemical properties of hydrogel shells, not only pH-selective (in simulated gastric or intestinal fluid) but also pH-insensitive drug releases of oil-drug@hydrogel particles are possible. Moreover, due to crystals' excellent barrier properties, highly oriented hydrogels are also effective in preventing the denaturation of L-ascorbic acid, enabling long-lasting therapeutic effects of drug. This particulate system can also load a variety of functional materials in oil core of the core-shell particles and hence could expand the application to various fields.