Carbon dot-copper nanocomposite-based fluorescent sensor for detection of creatinine in urine samples of CKD patients.

Creatinine (CR) is accepted as a clinical biomarker of chronic kidney disease (CKD) such as renal injury and kidney failure. To help facilitate the prognosis of CKD, a highly luminescent carbon dot (CD)-based fluorescent (FL) sensor has been built and employed for CR detection in diverse media (e.g., artificial and human urine). CDs, synthesized from sucrose precursor by a rapid microwave-assisted method (average diameter 20 nm), exhibited highly luminescent green emission upon UV exposure (λ = 390 nm, λ = 453 nm) with excellent temporal stability over three months. The nanocomposites are formed between CDs and metal ions (e.g., Cu) to realize the optimum biosensing of CR. Although Cu ions showcases a maximum quenching (73 %) of the CDs, Cu/CDs system restores 77 % of the original FL intensity upon the addition of CR. The linear detection range and limit of detection for CR are estimated as 10 to 0.1 mg·dL (R = 0.936) and 5.1 × 10 mg·dL, respectively. Furthermore, our biosensor shows excellent reproducibility and selectivity for CR in urine samples of healthy subjects and CKD patients. The Bland-Altman analysis for urine samples (n = 30) showcased an excellent agreement (R = 0.95) between our method and the gold standard 'Jaffe' method. These observations supported the practical utility of our method proposed for detection of CR in clinical samples.