Enhanced Catalytic Efficiency of Nanozyme with V-structured chip for Microfluidic Biosensing of S. typhimurium

Nanozymes, the nanomaterials with enzyme-like characteristics which exhibit lower cost, easier synthesis and functionalization, better stability compared with natural enzymes, have been widely developed for biosensing, disease therapy and environmental governance. However, the lack of catalytic efficiency of nanozymes compared to natural enzymes makes it difficult to completely replace natural enzymes to achieve higher sensitivity and lower detection limit in biosensing. Herein, magnetism-controlled technology was used to form nanozyme array consisted of stacked Fe3O4/Au NPs at the bottom of the microchannel as a spatially confined microreactor for the catalytic reaction. By enhancing the mass transfer process of substrate towards nanozyme which was mediated by the corresponding V-structure, a higher local concentration of substrate and more efficient utilization of active sites of nanozyme were obtained to increase the catalytic efficiency (kcat/KM) of the nanozyme array consisted of the Fe3O4/Au NPs by 95.2%, which was two orders of magnitude than that of the open reactor. Based on this, a colorimetric method on an integrated microfluidic platform was proposed for sensitive biosensing of Salmonella typhimurium. The entire detection could be completed within 30 minutes, yielding a linear range from 102 to 107 CFU/mL and a detection limit as low as 5.6 CFU/mL.