Citric Acid-Derived Carbon Quantum Dots with Tunable Emission and Oligonucleotide Functionalization for Biological Applications

Abstract

Carbon quantum dots (CQDs) are fluorescent nanomaterials that have attracted significant interest due to their chemical stability, low synthesis cost, tunable optical properties, and potential biocompatibility. In this work, CQDs were synthesized using citric acid as a precursor and incorporating different reagents in order to modulate their optical properties and explore their application in biological systems. The obtained materials were characterized by UV-Vis spectroscopy and fluorescence spectroscopy. Modifying the composition produced changes in the absorption profiles and shifts in the emission maxima, with fluorescence observed in the visible range and maxima between approximately 417 and 543 nm. The biocompatibility of the CQDs was evaluated through MTT cell viability assays in H1299 cells, showing high viability at the concentrations studied and no significant cytotoxic effects compared with the control. Subsequently, the functionalization of CQDs with a p53-derived oligonucleotide was explored. Electrophoretic analysis showed a change in oligonucleotide mobility compared with its free form, consistent with the formation of the Oligo-CQDs complex, while the fluorescent properties of the system were maintained. Overall, the results show that citric acid-derived CQDs allow their optical response to be modulated through changes in composition and exhibit characteristics compatible with their use as functionalizable fluorescent nanomaterials for future biological applications and studies of biomolecular interactions.

Keywords: carbon quantum dots; fluorescent nanomaterials; oligonucleotides