Carbon dots and Methylene blue facilitated photometric quantification of Hemoglobin

Early detection and monitoring of any abnormality of Hemoglobin (Hb) concentration in whole blood samples are important as this may be related to anemia, leukemia, dengue, etc. To facilitate quantitative detection and to monitor the hemoglobin level in the blood, we attempt to develop a low-cost, portable point of care (POC) device based on the spectrophotometric principle. Optical sensitivities of carbon quantum dots (CDs) are found to be highly responsive, while there is a selective reaction between Hb and reduced form of Methylene Blue (MBred). The interaction of Hb, MBred, and CDs is delineated using UV-Visible (UV-Vis) spectroscopy. CDs have a characteristic UV-Vis peak at similar to 347 nm, and it shows a gradual increase in intensity with a slight red shift (similar to 355 nm) on the progressive increase in Hb concentration. Simultaneously, the colorless MBred is oxidized to its blue oxidized form MBox and its characteristic peak starts reappearing at similar to 663 nm. These responses are exploited to quantify Hb concentration with a limit of detection (LOD) as low as similar to 2 g dL(-1) in a developed POC device, and the results are validated with the clinical data obtained from a local hospital with reasonably good agreement. This photometric detection approach can be adopted for other quantitative biosensors. (C) 2022 Elsevier B.V. All rights reserved.