A fluorescent imaging assay of cast in renal disease based on graphene quantum dots and Fe3O4 nanoparticles

Background Renal disease has become a global public health problem. Cast is a useful disease marker of kidney injury and renal failure. Hence, a cast-targeted fluorescent imaging assay is developed for the laboratory diagnosis of renal disease. Methods Firstly, graphene quantum dots (GQDs) were stripped from graphene oxide sheets and amine-modified. Then, anti-human IgG antibody was conjugated with Fe 3 O 4 nanoparticles to identify the cast in urine. Furthermore, the modified GQDs were linked onto the surface of Fe 3 O 4 /anti-IgG nanocomposites. Lastly, this Fe 3 O 4 /GQD fluorescent probe was added into the sample to detect the cast through fluorescent imaging. Results Preliminary application of this probe in clinical detection showed that the common types of casts in urine (including RBC , WBC, fatty and granular casts) could be detected by this fluorescent imaging assay. The method has the advantages of fast speed, high sensitivity (lowest detection limit to 2   casts/ml), good selectivity, and wide linear range (2–2000   casts/ml). Regression analysis also showed that there was a good linear relationship (y   =   0.9495   ×   +   10.974, R 2   =   0.9879) between the fluorescent counts and the casts in urine. Conclusion This cast-targeted fluorescent imaging assay may be a potential method for the laboratory diagnosis of renal disease.