Oxygen vacancies promote electron transfer in PRT@MnO2-x with boosting oxidase-mimicking activity for dual-mode detection of β-galactosidase

A novel oxygen vacancy-rich PRT@MnO 2-x nanozyme was fabricated via a facile one-pot ultrasonic method. • The as-prepared material possesses prominent oxidase-like activity, relying on in-situ water activation rather than exogenous oxygen. • A sensitive colorimetric/fluorescent dual-mode sensing platform was constructed for β-Gal activity with low detection limits. • The developed strategy shows satisfactory performance in human serum, possessing promising clinical application potential. Vacancy engineering has been widely applied to modulate the enzyme-like activity of nanomaterials by adjusting their surface/electronic structures and creating additional active sites. Regulating oxygen vacancies in nanomaterials and elucidating their oxygen activation mechanisms are crucial for designing high-performance nanozymes. Herein, we employed KMnO 4 as the manganese source and protamine as the stabilizer to prepare transition metal manganese oxide (PRT@MnO 2-x ) rich in oxygen vacancies. The as-prepared PRT@MnO 2-x exhibited superior oxidase-like activity, which is proposed to originate from oxygen vacancy-mediated electron transfer and valence band hole-driven water oxidation to ·OH. Steady state kinetic constant (K m ) suggested that PRT@MnO 2-x had a stronger affinity toward 3,3′,5,5′-tetramethylbenzidine and possessed prominent catalytic performance (K m and V max were 0.074 mM and 0.031 mM s −1  mg −1 ). An innovative method is proposed to employ PRT@MnO 2-x nanosheets with abundant oxygen vacancies for colorimetric/fluorescent dual-mode detection of β-Galactosidase (β-Gal) activity. Notably, the OXD-like activity of PRT@MnO 2-x is largely independent of dissolved oxygen or molecular oxygen. Instead, it facilitates electron transition from the valence band to the conduction band through the form of oxygen vacancies, enabling the oxidation of water to ·OH on the valence band of PRT@MnO 2-x . The detection limits (LOD) determined by colorimetric and fluorescence analysis for β-Gal activity are 0.015 U/L and 0.054 U/L respectively, and satisfactory spiked recovery results were achieved in human serum samples. This method has the advantages of low cost, simple operation and rapid response. The dual-mode signal sensor is expected to provide more accurate and robust detection of β-Gal than the single-mode probe, and has a wider application prospect. Download: Download high-res image (203KB) Download: Download full-size image