Biomineralization of Hemoglobin with ZIF-90 under Mild Conditions for Oxygen Sensing Application

Hemoglobin (Hb), owing to its superior oxygen adsorption properties, has emerged as a potential material for oxygen sensing. However, the practical applications of Hb have been significantly limited due to the propensity of bioactive molecules to become deactivated. This study employed a biomineralization strategy through Metal–Organic Frameworks (MOFs), bestowing external protection to Hb in a mild aqueous system. By leveraging the intrinsic hydrophilic nature of the protein structure, we have successfully obtained the Hb@ZIF-90 composite material through the de novo synthesis method in an aqueous phase, which was applied in the field of gaseous-phase oxygen sensing. In contrast to conventional approaches, this work not only preserved the bioactivity of the Hb molecules but also improved the crystallization of the ZIF-90 shell. In addition, although the Hb size is much larger than the cages of ZIF-90, Hb can be entrapped within interstitial spaces between the ZIF crystallites; density functional theory (DFT) calculations confirmed that the encapsulation of Hb could be controlled by leveraging a competitive regulation mechanism between surfactants and hemoglobin. Moreover, the Hb@ZIF-90 composite demonstrated stable and rapid oxygen sensing capabilities in gaseous environments due to the protection from the external biomineralized shell and the presence of ordered porous channels of ZIF-90.