Introduction:
Anthocyanins (AntCys) are natural pigments with pH-sensitive chromatic properties and antioxidant activity, making them attractive for stimuli-responsive materials. However, their application is limited by poor stability in neutral and alkaline environments. This study explores the encapsulation of AntCys, extracted from red cabbage, into surface-nanostructured microparticles obtained via Pickering emulsion polymerization to enhance stability and enable environmental responsiveness.
Methods:
The AntCy extract was incorporated into poly(methacrylic acid) microparticles synthesized using a Pickering emulsion stabilized by silica nanoparticles. Encapsulation efficiency was quantified spectrophotometrically. The release behavior of AntCy was studied in water, saline solution, and ethanol–water mixtures, and interpreted using various kinetic models. Morphology and uptake were evaluated by SEM and colorimetric analysis. Color responses to pH and gas vapors were tested for sensing applications.
Results:
The encapsulated AntCys in the microparticles were predominantly stabilized as flavylium cations inside the acidic polymer matrix. This way, the microparticles could preserve the integrity of AntCys towards degradation in high pH solutions yet maintaining its antioxidant ability. The release of AntCys was highly sensitive to external conditions. In saline and ethanol-rich environments, the release kinetics followed a diffusion-based profile, with increased release rates attributed to ionic screening and enhanced solubility. The colorimetric response of AntCy-loaded microparticles enabled the visual detection of acidic and basic vapors. A biocompatible polyvinyl alcohol composite embedded with microparticles was successfully prototyped for gas sensing.
Conclusions:
Pickering emulsion-derived polymeric microparticles provide a robust platform for encapsulation and stabilization of anthocyanins, enabling controlled release and preserving antioxidant activity. Their pH- and solvent-responsive release profiles, combined with visible colorimetric changes, make them suitable for use in intelligent packaging, biosensors, and environmentally responsive coatings.
