Carbon dots and MnO2 nanosheet nanocomposites sensing platform for sensitive detection of oxalate in urine samples of urolithiasis patients

Abstract

In the human body, oxalate tends to form calcium oxalate with calcium ions, which can trigger the formation of stones in the urinary system. Therefore, oxalate in urine is usually utilized as a crucial biomarker in clinical urolithiasis diagnoses. In this work, a turn-on fluorescent nanoprobe was developed based on nitrogen-doped carbon dots (N-CDs) and MnO₂ nanosheets (NSs) nanocomposites for oxalate sensing in urolithiasis patients. MnO₂ NSs is a good sensing platform with high extinction coefficients and rich redox chemistry. The fluorescent N-CDs can be quenched efficiently by MnO₂ NSs through the inner filter effect (IFE) to form N-CDs-MnO₂ nanocomposites. The reductive oxalate could operate the decomposition of MnO₂ NSs to Mn²⁺ resulting in the dissociation of the N-CDs-MnO₂ nanocomposites and fluorescence recovery of N-CDs. Under optimal conditions, the developed sensor revealed good specificity toward oxalate with a limit of detection (LOD) of 0.69 μM. The developed sensor was successfully applied to quantify oxalate content in 47 urine samples (41 urolithiasis patients and 6 healthy persons). The results showed great consistency with clinical diagnostic reports and computed tomography images. This novel method retains several unique advantages, including affordable, rapid, and validating potential clinical application.

Keywords: Carbon dots; Clinical analysis; Fluorescence; MnO(2) nanosheets; Oxalate.