Catalase-mimicking synthetic nano-enzymes can reduce lipopolysaccharide-induced reactive oxygen generation and promote rapid detection of hydrogen peroxide and l -cysteine

Purpose Here, we present the fabrication of a novel molybdenum-based, synthetic blue nano-enzyme (Synz) as an in situ oxygenic catalase mimic for the reduction of H 2 O 2 and the detection of hydrogen peroxide (H 2 O 2 ) and l -cysteine ( l -Cys). Methods Molybdenum-based synthetic nano-enzymes (Synz) were fabricated by the flash freeze–heating method. Field emission scanning electron microscopy, energy-dispersive X-ray spectrometry, X-ray diffraction analysis, X-ray photoelectron spectroscopy (HP-XPS) and Fourier transform infrared spectroscopy were used for the physicochemical characterization of the developed Synz. Ultraviolet–visible (UV–Vis) absorption spectra were used to detect both H 2 O 2 and l -Cys. Digital photographs were taken to visualize the colour changes in Synz-coated paper incubated with both H 2 O 2 and l -Cys. Results Synz was used as a colorimetric biosensor for the detection of both H 2 O 2 and l -Cys. Furthermore, co-incubation with lipopolysaccharide and Synz reduced the levels of both H 2 O 2 and reactive oxygen species in J77A4 macrophage cells. Additionally, the incubation of H 2 O 2 on Synz-coated cellulose filter paper led to a substantial change in the paper’s colour from blue to white with a low H 2 O 2 detection limit of 10 µM and, on the contrary, retained the blue colour with the addition of an l -Cys + H 2 O 2 solution with l -Cys concentration detection limit of 70 µM. Conclusion Collectively, our results show Synz to be a promising catalase-mimicking biomaterial that can alleviate H 2 O 2 and be used to develop a low-cost colorimetric paper biosensor for prognostic or theranostic applications.