Carbon quantum dots in the electroanalysis of DNA and albumin

Nano-carbon quantum dots (nano-CQDs) were prepared by a hydrothermal method using chitosan and melamine and characterized by FTIR, TEM and SEM. The maximum excitation and emission wavelengths of the carbon dots were determined to be 338 nm and 412 nm, respectively, indicating their strong fluorescence. The fluorescence properties of complexes of nano-CQDs with dsDNA and bovine serum albumin (BSA) were investigated. It was shown that DNA and albumin acquire fluorescent properties upon formation of complexes with CQDs. DNA and albumin labeled with CQDs exhibit electrochemical properties comparable to unlabeled biomolecules. DNA and DNA/CQDs complexes reveled peaks corresponding to guanine, adenine and thymine bases. BSA and BSA/CQDs complexes exhibited one broad peak corresponding electrochemical oxidation of tyrosine amino acids of polypeptide backbone. This indicates the biocompatibility of CQDs and the preservation of the spatial structures of DNA and bovine serum albumin upon formation of fluorogenic complexes. The studied electrochemical behavior of nucleic acid or protein complexes with CQDs allows using these structures for the visualization of biological objects and their electrochemical analysis simultaneously.