A hierarchical cobalt/carbon nanotube hybrid nanocomplex-based ratiometric fluorescent nanosensor for ultrasensitive detection of hydrogen peroxide and glucose in human serum.

Highly sensitive detection of HO and glucose is critical for fundamental research and disease diagnosis. A ratiometric sensor can simultaneously afford two readout signals that provide an internally normalized response to change, thereby reducing false results and improving detection accuracy. A novel ratiometric fluorescent nanosensor for ultrasensitive detection of hydrogen peroxide and glucose was constructed on the basis of the peroxidase-like properties of a hierarchical cobalt/carbon nanotube hybrid nanocomplex (Co-CNT). The as-prepared Co-CNT catalyzes the transformation of the non-fluorescent Amplex Red (AR) into a fluorescent derivative and the transformation of fluorescent scopoletin (SC) into a non-fluorescent derivative in the presence of HO. The sensing system changes colour from yellow to blue, which can be clearly seen with the naked eye. With the fluorescence ratio of AR to SC as readout, the detection limit of HO reaches as low as 100 nM. The developed assay is further utilized for determining HO-related oxidase reactions with the glucose and glucose oxidase system as model. Glucose can be selectively and sensitively detected as low as 150 nM. Satisfactory recoveries are obtained for glucose detection in serum samples. The developed assay is simple in terms of preparation and operation and provides a straightforward method for cost-effective and reliable detection of HO and HO-related reactions in clinical diagnosis and biomedical applications. Graphical abstract.