Selective and Controlled Release Responsive Nanoparticles with Adsorption-Pairing Synergy for Anthocyanin Extraction

Anthocyanins with different structures have different anti-inflammatory and anti-cancer properties. Precise structural use can improve the chemopreventive effects of anthocyanins and enhance treatment outcomes because the anthocyanin structure influences its functional sites and activities. However, owing to the available variety of anthocyanins and their complex structures, the low matching of intermolecular forces between existing adsorbents and anthocyanins limits the targeted separation of anthocyanin monomers. Short-range and efficient selective binding, which is difficult to achieve, is the current focus in the extraction field. We here developed self-assembled Fe₃O₄-based nano adsorbers with different surface modifications based on adsorption-pairing synergy. The electrostatic force, coordination bond, hydrogen bond, and π-π* bond together induced selective adsorption between Fe₃O₄ nanoparticles and anthocyanin molecules. An acid-release solution disrupted the polarity balance in the aforementioned association system, thereby promoting the controlled release of anthocyanins. Among the candidates, the effects of morphology, particle size, surface charge, and functional group on adsorption performance were analyzed. The polyacrylamide-modified magnetic Fe₃O₄ nanoparticles were found to be favorable for selectively extracting anthocyanin, with an adsorption capacity of 19.74 ± 0.07 mg g^-1. The release percentage of cyanidin-3-O-glucoside reached up to 98.6% ± 1.4%. This study offers a scientific basis for developing feasible nanotechniques to extract anthocyanins and plant active substances.