One-step fabrication of porous calcium alginate microspheres templated from O/W/O Pickering double emulsion via in situ ionotropic gelation

Porous polymer microspheres have attracted considerable interest in biomedicine, catalysis, and adsorption. However, their practical applications remain limited because poor biocompatibility restricts biomedical use, whereas cumbersome fabrication processes hinder scalable production and precise structural control required for catalytic and adsorption applications. Herein, we report a facile and green strategy for fabricating porous calcium alginate microspheres using oil-in-water-in-oil Pickering double emulsions as templates. Hydrophobic silica nanoparticles are used to stabilize the emulsion interfaces, while alginate dissolved in the intermediate aqueous phase undergoes in situ ionotropic gelation. The gelation process is triggered by the gradual release of Ca 2 + from ethylenediamine tetraacetic acid calcium disodium (EDTA-Ca) complexes during glucono-δ-lactone (GDL) hydrolysis. This one-step approach enables regulation of microsphere morphology and internal structure by adjusting the concentrations of GDL, EDTA-Ca, and alginate. As a proof of concept for delivery system, bovine serum albumin was efficiently encapsulated within the porous microspheres, and its release behavior could be regulated by varying the protein loading and environmental pH. By avoiding synthetic surfactants, this green and scalable strategy provides a versatile platform for the fabrication of biocompatible porous microspheres, with promising applications in controlled delivery, protein and enzyme immobilization, tissue engineering, and related advanced applications. Download: Download high-res image (182KB) Download: Download full-size image A facile and green strategy using Pickering double emulsions as templates successfully fabricates porous calcium alginate microspheres which achieve efficient protein encapsulation and pH-responsive controlled release.