Freezing-assisted reverse microemulsion synthesis of hollow mesoporous silica encapsulated glucose oxidase

Bio-activity conservation of biomolecules after immobilizing in nanomaterials has been a tough challenge, especially in biomedical applications. Herein, we developed a novel freezing-assisted reverse microemulsion method to encapsulate water-soluble enzymes in hollow mesoporous silica nanospheres (HMSNs) for maximumly maintaining enzyme bio-activity. Firstly, a low-temperature and ethanol-free synthesis was carried out, and glucose oxidase (GOx) as a model enzyme was encapsulated into HMSNs to obtain GOx@HMSNs. The TEM and SEM images showed a uniform sphere morphology of GOx@HMSNs with a large hollow cavity for GOx loading. The element mapping, FTIR spectrum and TGA curve further confirmed the effective physical encapsulation of GOx in HMSNs, which can maintain stable bio-activity as verified by the enzyme activity assay. In addition to the facile synthesis for avoiding enzyme-denaturation, the N2 adsorption–desorption curves further demonstrated that small mesopores on HMSNs for blocking enzyme leakage may be another important factor for conserving GOx activity. Finally, GOx@HMSNs as a biosensor significantly possessed a wider linear range of 0.06 mM to 2.61 mM with a low detection limit of 0.01 mM, indicating high sensitivity. Therefore, our synthesis method provides a promising approach for biomolecule immobilization with potent bio-activity and biosensor applications with superior sensitivity.