Photothermal performance of a novel carbon dot and its conjugate with disulfiram for prostate cancer PC3 cell therapy.

Aim: To develop and employ a copper, sulfur, nitrogen-carbon quantum dot (C,S,N-CQD) multifunctional platform for synergistic cancer therapy, combining chemotherapy and photothermal treatment with in vitro cancer cell imaging. Materials & methods: Cu,S,N-CQDs were synthesized hydrothermally, loaded with disulfiram (DSF), and characterized through UV-Vis spectrophotometry, photoluminescence, Fourier-transform infrared spectroscopy, high-resolution transmission electron microscopy, dynamic light scattering, x-ray diffraction and EDAX. Results: Cu,S,N-CQD exhibited 5.5% absolute fluorescence quantum yield, 46.0% photothermal conversion efficiency and excellent stability. The release of DSF-loaded Cu,S,N-CQD, photothermal performance, and IC50 on PC3 prostate cancer cells, were evaluated. The impact of cellular glutathione on nanocarrier performance was investigated. Conclusion: Cu,S,N-CQD as a photothermal agent and DSF carrier showed synergy (combination index: 0.71) between chemotherapy and photothermal therapy. The nanocarrier simultaneously employed for in vitro cancer cell imaging due to its unique fluorescence properties.

Nanometer-scale particles can be used to treat and detect cancer in many ways. A type of nanoparticle was designed to attack cancer in two different ways. These nanoparticles ­ copper, sulfur, nitrogen­carbon quantum dots (C,S,N­CQDs) ­ were designed to both deliver a chemotherapy drug to cancer cells and act as a photothermal agent. This means that when light of a particular energy is shone on these particles, they heat up and can kill cancer cells. These C,S,N­CQDs loaded with the chemotherapy drug disulfiram were then tested on the prostate cancer cell line PC3. When a laser was shone on these particles and they became excited, they reduced cancer cell viability both by releasing the drug and heating up and killing the surrounding cells. These Cu,S,N-CQDs are also fluorescent, meaning they can be used to image cancer cells in tests like these.

Ultrasensitive FRET-based aptasensor for interleukin-6 as a biomarker for COVID-19 progression using nitrogen-doped carbon quantum dots and gold nanoparticles.

A label-free and specific FRET-based interleukin-6 (IL-6) aptasensor was developed using a DNA aptamer modified with nitrogen-doped carbon quantum dots (NCDs) and gold nanoparticles (AuNPs) as a donor-quencher pair. The assayed target was capable of disrupting the donor-acceptor assemblies yielding a concentration-related fluorescence recovery of NCDs (λem = 445 nm and λex = 350 nm). By designing two different probes, the interaction of DNA aptamers with IL-6 protein was studied using FRET efficiency. It appeared that the sensing probes showed slightly different sensing profiles. One of the aptasensors showed a linear response of 1.5-5.9 pg/mL for IL-6 with a coefficient of determination of R2 ≥ 0.99 and the a detection limit of 0.82 pg/mL (at S/N = 3). The experimental results indicated that the biosensor can be applied to determine IL-6 in human serum (with recovery of 95.7-102.9%). Due to the high sensitivity, excellent selectivity, and simplicity of the procedure, this strategy represents a promising alternative for IL-6 sensing in clinical applications.

Label-free triplex DNA-based biosensing of transcription factor using fluorescence resonance energy transfer between N-doped carbon dot and gold nanoparticle.

Herein, a new turn-on fluorescent assay was established as a platform for the sensing of transcription factor NF-kB p50 based on triplex DNA labeled with N-doped carbon dots (NCDs) and gold nanoparticles (AuNPs) as donors and acceptors, respectively in the fluorescence resonance energy transfer (FRET) system. The synthetized nanoparticles were studied by different characterization techniques. A labeled DNA molecule was designed to form a triplex when no target protein existence and reported its formation by the change in FRET efficiency. While the triplex DNA was formed, the fluorescence of carbon dots at 503 nm (excitation at 460 nm) was quenched by FRET between NCD and AuNP. However, presence of NF-kB p50 followed by the considerable enhancement in the fluorescence intensity caused by the release of AuNPs labeled single stranded DNA from the triplex DNA structure, used for sensitive determination of the transcription factor. This technique showed a linearity (R2 = 0.9943) in the range of 20-150 pM with a limit of detection of 9 pM for the determination of NF-kB p50. Moreover, the sequence-specific triplex-based biosensor could discriminate NF-kB p50 from the other proteins with high selectively. Our results suggest that the biosensor provides a generalizable platform for rapid detection of NF-kB p50 in synthetic medium, promising in prevention and early diagnosis of cancer.

Carbon dots-embedded N-acetylneuraminic acid and glucuronic acid-imprinted polymers for targeting and imaging of cancer cells.

Diagnosis, treatment, and prediction of cancer progression require new targeting agents to specifically target cell surface receptors. Herein, we demonstrated fluorescent carbon quantum dots-molecularly imprinted polymer (CQD-MIP) for selective targeting and imaging of cancer cells. Carbon quantum dots (CQDs) were synthesized and characterized. The synthesized CQDs had average size of 1.5 nm and show intense fluorescence emission at wavelength of 450 nm with excitation at 370 nm. CQD-MIP nanoparticles imprinted with N-acetylneuraminic acid and glucuronic acid were prepared and characterized. CQD-MIPs were successfully applied for selective targeting and imaging of MCF-7, HepG-2, and NIH-3T3 cell lines. Non-imprinted polymer (NIP) showed no binding properties toward a target molecule. Non-imprinted polymer (NIP) and non-cancerous human cell lines were used for controlling the imprinting and targeting effects, respectively. Acceptable results were obtained with imprinted polymers on cancer cells.

A carbon dot and molecular beacon based fluorometric sensor for the cancer marker microRNA-21.

A carbon quantum dot (CQD) labeled molecular beacon was synthesized and applied to the detection of microRNA-21. The CQDs possess low cytotoxicity, excellent water solubility, and photostability. The CQDs were characterized by transmission electron microscopy, dynamic light scattering, Fourier-transform infrared spectroscopy, and fluorescence spectroscopy. The molecular beacon (MB) was labeled with the CQDs at the 5' end, and with Black Hole Quencher 1 (BHQ1) at the 3' end. The two labels act as the donor and acceptor parts of a FRET system, respectively. Only weak fluorescence is observed in the absence of microRNA-21, and in the presence of scrambled or mismatched sequences. However, in the presence of microRNA-21, fluorescence intensity of the CQDs at 460 nm (excitation at 360 nm) recovers. The hybridization of the hairpin structure of the MB with microRNA-21 opens the loop of MB. Consequently, the distance between the BHQ1 quencher and the CQDs is increased and fluorescence changes. The probe has high sensitivity (with a 0.3 nM limit of detection) and specificity. It can distinguish between microRNA-21 and its single mismatch mutant and hence represents a valuable tool for the early cancer diagnosis. Graphical abstract Schematic presentation of a fluorometric microR-21 assay using carbon dots carrying a molecular beacon (MB) labeled with a black hole quencher. Quenching is suppressed once the MB binds to microRNA-21.