Hierarchical Co(OH)₂/FeOOH/WO₂ ternary nanoflowers as a dual-function enzyme with pH-switchable peroxidase and catalase mimic activities for cancer cell detection and enhanced photodynamic therapy

Negar Alizadeh^a, Abdollah Salimia,b, Tsun-Kong Sham^c, Paul Bazylewski^d, Giovanni Fanchini^d, Fardin Fathi^e, Farzad Soleimani^e

Department of Chemistry, University of Kurdistan, 66177-15175 Sanandaj, Iran.

Abstract

Development of novel nanomaterials with enzymatic activity as nanoprobes for cancer cell detection and therapy is an essential issue in clinic diagnostics. In this work, due to their low cost and high stability of metal oxides nanomaterials we report synthesis of Co(OH)₂/FeOOH/WO₃ nanoflowers via one step and simple hydrothermal method as dual-function enzyme with enhanced peroxidase and catalase-like activity. Interaction between prepared nanoflowers and H₂O₂ in aqueous solution studied by electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS) and UV–vis techniques. Artificial enzymes being increasingly used but little has known based on the pH switchable peroxidase-like and catalase-like activities of metals. Here, we report pH-switchability for Co(OH)₂/FeOOH/WO₃ nanoflowers, which at acidic pH (pH < 7) peroxidase catalytic activities is dominant in contrast at basic pH (pH > 7) the catalase activities is dominant. Indeed, these nanomaterials catalyze H₂O₂ to hydroxyl radicals at acidic pH and catalyze H₂O₂ to oxygen at basic condition. It was also found that the amount of generated hydroxyl radicals and oxygen was subordinate to the concentration of Co(OH)₂/FeOOH/WO₃ nanoflowers. Due to peroxidase-like catalytic behavior of proposed nanoflowers a colorimetric biosensor for detection of human cervical cancer cells (HeLa cancer cells) at wide detection range from 50 to 5 × 10⁴ cells/mL with a detection limit as low as 12 cells/mL developed using 3,3′,5,5′-tetramethylbenzidine(TMB) as typical peroxidase substrate in the presence of H₂O₂. Furthermore, the anticancer behavior of Co(OH)₂/FeOOH/WO₃ via their intrinsic catalase-like activity and production of O₂ supply for photodynamic therapy (PDT) is also evaluated. This work paves a way to design the highly active nanozymes not only in development of colorimetric biosensors but also in diagnosis and treatment of cancers.

Keywords: Co(OH)₂/FeOOH/WO₃ nanoflowers, pH-switchable, Peroxidase activity, Catalase activity, Cancer cells, Photodynamic therapy.