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Nitrogen-doped carbon quantum dots as fluorescent sensor for doxorubicin and chlortetracycline: experimental and DFT
Sondos Lotfy1, Mohamed M Aboelnga1,2, Elhossein A Moawed1
1Chemistry Department, Faculty of Science, Damietta University New Damietta Damietta 34517 Egypt sayedelbayoumy@du.edu.eg.
Abstract:
The accurate and rapid detection of clinically vital but potentially toxic pharmaceutical residues, such as the anticancer agent Doxorubicin (DOX) and the broad-spectrum antibiotic Chlortetracycline (CTC), is essential for therapeutic drug monitoring and environmental safety. This work presents the development of a novel fluorescent sensor based on nitrogen-doped carbon quantum dots (NEDA-CQDs) synthesized via a simple hydrothermal method using N-(1-naphthyl) ethylenediamine (NEDA) and citric acid (CA) as precursors. The obtained CQDs exhibited excellent aqueous dispersibility, strong blue fluorescence with a quantum yield (QY) of 2.7%, and high photostability. Comprehensive characterization revealed uniform quasi-spherical nanoparticles enriched with amino (NH2), hydroxyl (OH), and carboxyl (COOH) functionalities. The NEDA-CQDs exhibited remarkable fluorescence quenching in the presence of DOX and CTC, allowing for their quantitative detection with limits of detection (LOD) of 4.02 µM and 2.53 µM, respectively. Stern-Volmer analysis demonstrated highly linear quenching behavior, indicating a combined static quenching and inner filter effect (IFE) mechanism. Application to human serum and urine samples resulted in excellent recoveries ranging from 93.65% to 106.34%, highlighting the practical utility of the sensor. Density functional theory (DFT) calculations further elucidated the sensing mechanism, demonstrating strong binding energies, significant HOMO-LUMO gap reductions, Fermi level shifts, and enriched non-covalent interactions (NCI), including π-π stacking and hydrogen bonding. Reduced density gradient (RDG) and NCI analyses confirmed the formation of a stable drug-sensor complex, consistent with the experimentally observed fluorescence quenching. Overall, the synergy between experimental findings and theoretical insights establishes NEDA-CQDs as an efficient, low-cost, and robust fluorescent nano-sensor for monitoring DOX and CTC in biological and environmental matrices.
Insights
A novel nitrogen-doped carbon quantum dot (NEDA-CQDs) fluorescent sensor was developed for detecting Doxorubicin (DOX) and Chlortetracycline (CTC). This efficient sensor shows high sensitivity and accuracy in biological samples, aiding drug monitoring and environmental safety.
Area of Science:
- Materials Science
- Analytical Chemistry
- Nanotechnology
Background:
- Accurate detection of pharmaceutical residues like Doxorubicin (DOX) and Chlortetracycline (CTC) is crucial for therapeutic drug monitoring and environmental safety.
- Existing detection methods may lack the sensitivity, speed, or cost-effectiveness required for real-time analysis.
- Development of novel, highly sensitive, and selective sensors is essential for addressing these challenges.
Purpose of the Study:
- To develop a novel fluorescent sensor based on nitrogen-doped carbon quantum dots (NEDA-CQDs) for the sensitive detection of DOX and CTC.
- To characterize the synthesized NEDA-CQDs and elucidate their sensing mechanism using experimental and theoretical approaches.
- To evaluate the sensor's performance in complex biological matrices like human serum and urine.
Main Methods:
- Synthesis of NEDA-CQDs using a hydrothermal method with N-(1-naphthyl) ethylenediamine (NEDA) and citric acid (CA).
- Characterization of NEDA-CQDs using spectroscopy, microscopy, and surface analysis techniques.
- Fluorescence quenching assays for DOX and CTC detection, including Stern-Volmer analysis.
- Application of the sensor in human serum and urine samples.
- Density Functional Theory (DFT) calculations to investigate the sensing mechanism and drug-sensor interactions.
Main Results:
- NEDA-CQDs exhibited strong blue fluorescence (QY 2.7%), good dispersibility, and photostability.
- Remarkable fluorescence quenching was observed in the presence of DOX (LOD 4.02 µM) and CTC (LOD 2.53 µM).
- High recovery rates (93.65%–106.34%) were achieved in human serum and urine samples.
- DFT calculations confirmed strong binding interactions, including π-π stacking and hydrogen bonding, between NEDA-CQDs and the analytes.
Conclusions:
- NEDA-CQDs serve as an efficient, low-cost, and robust fluorescent nano-sensor for DOX and CTC detection.
- The sensor demonstrates practical utility for monitoring these pharmaceuticals in biological and environmental samples.
- The combined experimental and theoretical approach provides a deep understanding of the sensing mechanism.
- This work offers a promising platform for developing advanced fluorescent sensors for pharmaceutical residue analysis.
