Dual pH- and magnetic-responsive Fe3O4@ZIF-8 core–shell nanoparticles for ultra-fast adsorption and desorption of histidine-rich proteins

To address the need for rapid desorption in protein adsorption applications, we developed and characterized magnetic core–shell nanoparticles composed of a zeolite imidazolate framework-8 (ZIF-8) coating on magnetite (Fe 3 O 4 ) cores (Fe 3 O 4 @ZIF-8). This nanostructure integrates the pH-sensitive properties of ZIF-8 with the magnetic responsiveness of Fe 3 O 4 , enabling rapid separation within one minute via an external magnetic field. In the synthesis of Fe 3 O 4 @ZIF-8, the particle size of the ZIF-8 shell was found to increase concurrently with the molar ratio of zinc nitrate hexahydrate to 2-methylimidazole. The resulting shells were uniformly distributed on the surface of the Fe 3 O 4 cores. Furthermore, a positive correlation was observed between the ZIF-8 particle size and the adsorption capacity for histidine-rich proteins. In adsorption experiments using bovine hemoglobin (BHB) as a model protein, Fe 3 O 4 @ZIF-8 achieved an adsorption capacity of 1013.5 mg/g within 3 min, representing 87% of its maximum adsorption potential. Saturation adsorption, with a capacity of 1164.3 mg/g, was reached within 8 min. Importantly, the pH-responsive nature of the ZIF-8 component facilitated highly efficient desorption. A high release efficiency of 90% was achieved in just 1 min using a phosphate buffer at pH 5.2. This dual pH- and magnetic-responsive system demonstrates significant potential for applications requiring fast and controllable protein adsorption and desorption, positioning it as an ideal tool for targeted protein recovery in various biochemical and industrial processes.