Bottom-up synthesis of nitrogen and oxygen co-decorated carbon quantum dots with enhanced DNA plasmid expression

An "on-off-on" Fluorescent Sensor Based on Carbon Dots for the Detection of Au (III) and Creatinine

The present study proposes a new approach for detecting trace amounts of creatinine (Cre) through the utilization of a fluorescence sensor system consisting of nitrogen doped carbon dots (NCDs) and gold ions (Au3+). Yellow fluorescent carbon dots were prepared using a one-step hydrothermal method with o-phenylenediamine and isopropanol as raw materials. First, gold ions are reduced to gold nanoparticles (Au NPs), which bind to NCDs, resulting in electron transfer and fluorescence quenching of NCDs. After adding creatinine, Cre and Au NPs were preferentially combined to form non-fluorescent complexes, and the NCDs fluorescence was restored. The study achieved a detection limit of 1.06 × 10-7 M for Au3+ and 9.29 × 10-9 M for creatinine, indicating a high level of sensitivity. The sensing system has also been successfully utilized for detecting Au3+ in lake water and Cre in human urine, indicating its promising potential and practical applications in the areas of environmental monitoring and biosensing.

Carbon quantum dot-induced developmental toxicity in Daphnia magna involves disturbance of symbiotic microorganisms

With the increasing synthesis and application of carbon quantum dots (CQDs), their prevalence as pollution in water environments has increased. However, the toxic effects of CQDs on aquatic organisms are unclear, and their environmental safety must be evaluated. Herein, Daphnia magna was used as a model organism to explore the developmental toxicity of CQDs under a full life-cycle exposure. It was found that the feeding rate and offing number of D. magna decreased with increasing CQD concentration, and the body length of D. magna showed a trend of first increasing and then decreasing. These results indicated that long-term exposure to CQDs has evident toxic effects on D. magna development. Symbiosis analysis showed that the composition of the symbiotic microbial community of D. magna was disturbed by CQDs. The abundance of microorganisms involved in the immune response of D. magna such as Rhodobacter, decreased; those involved in the inflammation such as Gemmobacter, increased; and those involved in the nitrogen cycle, such as Hydrogenophaga and Paracoccus, decreased. When D. magna was subjected to environmental pressure, host-microflora interactive immune regulation was induced. The abundance of probiotics in D. magna, such as Rhodococcus, increased in response to environmental pressure. The results of KEGG function prediction showed that the abundance of symbiotic microorganisms involved in energy absorption and metabolism was affected by CQDs. In addition, the correlation analysis showed that there was a correlation between the changes in the symbiotic microbial community and the damage to D. magna after exposure to CQDs. Thus, it is appealed that as a potential environmental pollutant, CQDs have aquatic environmental risks, and their safe application deserves attention.

High-performance photocatalytic peroxymonosulfate activation by carbon quantum dots via precise surface chemistry regulation: Insight into the structure-function relations

Carbon quantum dots (CQDs) are considered promising metal-free green catalysts for the activation of persulfates, but direct experimental evidence to identify the true active sites on the surface of CQDs is still lacking. We prepared CQDs with different oxygen contents by controlling the carbonisation temperature, using a simple pyrolysis method. Photocatalytic activity experiments show that CQDs₂₀₀ exhibits the best PMS activation performance. By investigating the relationship between the oxygen functional groups on CQDs surface and photocatalytic activity, it was postulated that the C=O groups might be the predominant active site, which was confirmed by selective chemical titrations of the C=O, C-OH and COOH groups. Furthermore, limited to the weak photocatalytic properties of the pristine CQDs, ammonia and phenylhydrazine were used to precisely nitrogen-modify the o-CQD surface. We found that phenylhydrazine-modified o-CQDs-PH promoted the absorption of visible light and the separation of photocarriers, thus enhancing the activation of PMS. Theoretical calculations provide more insights from different levels of the pollutant, fine-tuned CQDs, and their interactions.

Intrinsic specificity of plain ammonium citrate carbon dots for Helicobacter pylori: Interfacial mechanism, diagnostic translation and general revelation

The exploitation of carbon dots (CDs) is now flourishing; however, more effort is needed to overcome their lack of intrinsic specificity. Herein, instead of synthesizing novel CDs, we reinvestigated three reported CDs and discovered that plain ammonium citrate CDs (AC-CDs) exhibited surprising specificity for Helicobacter pylori. Notably, we showed that the interfacial mechanism behind this specificity was due to the affinity between the high abundant urea/ammonium transporters on H. pylori outer membrane and the surface-coordinated ammonium ions on AC-CDs. Further, we justified that ammonium sulfate-citric acid CDs also possessed H. pylori-specificity owing to their NH₄⁺ doping. Thereby, we suggested that the incorporation of a molecule that could be actively transported by abundant membrane receptors into the precursors of CDs might serve as a basis for developing a plain CD with intrinsic specificity for H. pylori. Moreover, AC-CDs exhibited specificity towards live, dead, and multidrug-resistant H. pylori strains. Based on the specificity, we developed a microfluidics-assisted in vitro sensing approach for H. pylori, achieving a simplified, rapid and ultrasensitive detection with two procedures, shortened time within 45.0 ​min and a low actual limit of detection of 10.0 ​CFU ​mL⁻¹. This work sheds light on the design of more H. pylori-specific or even bacteria-specific CDs and their realistic translation into clinical practice.

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Plain ammonium citrate CDs have intrinsic specificity for Helicobacter pylori.

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Affinity of outer-membrane urea receptors to NH₄⁺ on CDs decides the specificity.

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The specific CDs coupling microfluidics confers a simplified detection of H. pylori.

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The mechanism and translation inspire the engineering of bacteria-specific CDs.

Assessing the Environmental Effects Related to Quantum Dot Structure, Function, Synthesis and Exposure

Quantum dots (QDs) are engineered semiconductor nanocrystals with unique fluorescent, quantum confinement, and quantum yield properties, making them valuable in a range of commercial and consumer imaging, display, and lighting technologies. Production and usage of QDs are increasing, which increases the probability of these nanoparticles entering the environment at various phases of their life cycle. This review discusses the major types and applications of QDs, their potential environmental exposures, fates, and adverse effects on organisms. For most applications, release to the environment is mainly expected to occur during QD synthesis and end-product manufacturing since encapsulation of QDs in these devices prevents release during normal use or landfilling. In natural waters, the fate of QDs is controlled by water chemistry, light intensity, and the physicochemical properties of QDs. Research on the adverse effects of QDs primarily focuses on sublethal endpoints rather than acute toxicity, and the differences in toxicity between pristine and weathered nanoparticles are highlighted. A proposed oxidative stress adverse outcome pathway framework demonstrates the similarities among metallic and carbon-based QDs that induce reactive oxygen species formation leading to DNA damage, reduced growth, and impaired reproduction in several organisms. To accurately evaluate environmental risk, this review identifies critical data gaps in QD exposure and ecological effects, and provides recommendations for future research. Future QD regulation should emphasize exposure and sublethal effects of metal ions released as the nanoparticles weather under environmental conditions. To date, human exposure to QDs from the environment and resulting adverse effects has not been reported.

Synthesis and Properties of Nitrogen-Doped Carbon Quantum Dots Using Lactic Acid as Carbon Source

Nitrogen-doped carbon quantum dots (N-CQDs) were synthesized in a one-step hydrothermal technique utilizing L-lactic acid as that of the source of carbon and ethylenediamine as that of the source of nitrogen, and were characterized using dynamic light scattering, X-ray photoelectron spectroscopy ultraviolet-visible spectrum, Fourier-transformed infrared spectrum, high-resolution transmission electron microscopy, and fluorescence spectrum. The generated N-CQDs have a spherical structure and overall diameters ranging from 1-4 nm, and their surface comprises specific functional groups such as amino, carboxyl, and hydroxyl, resulting in greater water solubility and fluorescence. The quantum yield of N-CQDs (being 46%) is significantly higher than that of the CQDs synthesized from other biomass in literatures. Its fluorescence intensity is dependent on the excitation wavelength, and N-CQDs release blue light at 365 nm under ultraviolet light. The pH values may impact the protonation of N-CQDs surface functional groups and lead to significant fluorescence quenching of N-CQDs. Therefore, the fluorescence intensity of N-CQDs is the highest at pH 7.0, but it decreases with pH as pH values being either more than or less than pH 7.0. The N-CQDs exhibit high sensitivity to Fe³⁺ ions, for Fe³⁺ ions would decrease the fluorescence intensity of N-CQDs by 99.6%, and the influence of Fe³⁺ ions on N-CQDs fluorescence quenching is slightly affected by other metal ions. Moreover, the fluorescence quenching efficiency of Fe³⁺ ions displays an obvious linear relationship to Fe³⁺ concentrations in a wide range of concentrations (up to 200 µM) and with a detection limit of 1.89 µM. Therefore, the generated N-CQDs may be utilized as a robust fluorescence sensor for detecting pH and Fe³⁺ ions.

Carboxyl-Rich Carbon Dots as Highly Selective and Sensitive Fluorescent Sensor for Detection of Fe3+ in Water and Lactoferrin

As lactoferrin (LF) plays an essential role in physiological processes, the detection of LF has attracted increasing attention in the field of disease diagnosis. However, most current methods require expensive equipment, laborious pretreatment, and long processing time. In this work, carboxyl-rich carbon dots (COOH-CDs) were facilely prepared through a one-step, low-cost hydrothermal process with tartaric acid as the precursor. The COOH-CDs had abundant carboxyl on the surface and showed strong blue emission. Moreover, COOH-CDs were used as a fluorescent sensor toward Fe3+ and showed high selectivity for Fe3+ with the limit of detection (LoD) of 3.18 nM. Density functional theory (DFT) calculations were performed to reveal the mechanism of excellent performance for Fe3+ detection. Meanwhile, COOH-CDs showed no obvious effect on lactobacillus plantarum growth, which means that COOH-CDs have good biocompatibility. Due to the nontoxicity and excellent detection performance for Fe3+, COOH-CDs were employed as a fluorescent sensor toward LF and showed satisfying performance with an LoD of 0.776 µg/mL, which was better than those of the other methods.

Determination of chondroitin sulfate in synovial fluid and drug by ratiometric fluorescence strategy based on carbon dots quenched FAM-labeled ssDNA

Chondroitin sulfate (CS) plays an increasingly important role in clinical settings and pharmacy quality control. However, sensitive and simple methods for CS detection remain limited. In this work, positively charged nitrogen doped carbon dots (P-NCDs) with internal luminescence and quenching property to FAM-labeled random-sequence ssDNA (F-ssDNA) were prepared by a simple heating method. P-NCDs attached and quenched F-ssDNA through electrostatic interaction to form the system of P-NCDs and F-ssDNA (P-NCDs/F-ssDNA) with retained fluorescence intensity of P-NCDs. The highly negatively charged CS reacted electrostatically with P-NCDs and then replaced F-ssDNA in P-NCDs/F-ssDNA to recover the fluorescence intensity of the original quenched F-ssDNA while retaining the internal fluorescence intensity of P-NCDs. Thus, by using restored F-ssDNA as the signal controlled by adding CS to P-NCDs/F-ssDNA, a ratiometric fluorescence strategy based on the retained fluorescence of P-NCDs as reference signal was fabricated through synchronous fluorescence spectrometry for the sensitive detection of CS. Under the optimal experimental conditions, a linear equation for CS was obtained for CS concentration within the range of 0.05-2.0 μg/mL. The method was also successfully applied for the accurate determination of CS in joint fluid samples of arthritic patients, chondroitin sulfate tablets, and chondroitin sulfate eye drops, suggesting its appreciable application potential in the clinic.

A review of carbon quantum dots and their applications in wastewater treatment

Carbon quantum dots (CQDs) are a fascinating class of carbon nanoparticles with sizes around 10 nm. The unique properties of CQDs are low toxicity, chemical inertness, excellent biocompatibility, photo-induced electron transfer and highly tunable photoluminescence behaviour. Sustainable raw materials are commonly used for the fabrication of CQDs because they are cost-effective, eco-friendly and effective to minimise waste production. CQDs can be fabricated using laser ablation, microwave irradiation, hydrothermal reaction, electrochemical oxidation, reflux method and ultrasonication. These methods undergo several chemical reactions such as oxidation, carbonisation, pyrolysis and polymerisation processes to produce CQDs. Due to small particle sizes of CQDs, they possess strong tunable fluorescent properties and highly photo-luminescent emissions. It also contains oxygen-based functional groups and highly desired properties as semiconductor nanoparticles. Therefore, CQDs are promising nanomaterials for photo-catalysis, ions sensing, biological imaging, heavy metal detection, adsorption treatment, supercapacitor, membrane fabrication and water pollution treatment. This review paper will discuss the physical and chemical properties of CQDs, raw materials and methods used in the fabrication of CQDs, the stability of CQDs as well as their potential applications in wastewater treatment and biomedical field.

Smart, Tunable CQDs with Antioxidant Properties for Biomedical Applications-Ecofriendly Synthesis and Characterization

Carbon quantum dots (CQDs) are nanoobjects of a size below 10 nm. Due to their favorable features, such as tunable luminescence, unique optical properties, water solubility, and lack of cytotoxicity, they are willingly applied in biomedicine. They can be obtained via bottom-up and top-down methods. However, to increase their quantum yield they must undergo post-processing. The aim of the following research was to obtain a new type of CQDs modified with a rhodamine b derivative to enhance their fluorescence performance without biocompability deterioration. For their preparation glucose was used as a precursor and four different carbonizing agents which affected semi- and final products luminescence properties. The ready nanomaterials were investigated over their chemical structure by FTIR and NMR, whereas morphology was investigated by the TEM method. Their optical properties were determined by UV–VIS spectroscopy. Fluorescence behavior, photo- and pH-stability, as well as solvatochromism showed their applicability in various biomedical applications due to the controlled properties. The samples exhibited excellent antioxidant activity and lack of cytotoxicity on L929 mouse fibroblasts. The results showed that proposed strategy enables preparation of the superior nanomaterials with outstanding luminescence properties such as quantum yield up to 17% which can be successfully applied in cell labelling, bioimaging, and theranostics.

Enhanced Gene Delivery in Bacterial and Mammalian Cells Using PEGylated Calcium Doped Magnetic Nanograin

BACKGROUND

Beyond viral carriers which have been widely used in gene delivery, non-viral carriers can further improve the delivery process. However, the high cytotoxicity and low efficiency impedes the clinical application of non-viral systems. Therefore, in this work, we fabricated polyethylene glycol (PEG) coated, calcium doped magnetic nanograin (PEG/Ca(II)/Fe3O4) as a genome expression enhancer.

METHODS

Monodisperse magnetic nanograins (MNGs) with tunable size were synthesized by a solvothermal method. The citrate anions on the spherical surface of MNGs capture Ca2+ ions by an ion exchange process, which was followed by surface capping with PEG. The synthesized PEG/Ca(II)/Fe3O4 was characterized using Fourier-transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) spectra, vibrating sample magnetometer (VSM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). MTT test was utilized to assess the toxicity of PEG/Ca(II)/Fe3O4. Real time qPCR was applied for quantification of gene expression.

RESULTS

DLS spectra and TEM images confirmed a thin layer of PEG on the nanocarrier surface. Shifting the zeta potential in the biological pH window from -23.9 mV (for Fe3O4) to ≈ +11 mV (for PEG/Ca(II)/Fe3O4) confirms the MNGs surface protonation. Cytotoxicity results show that cell viability and proliferation were not hindered in a wide range of nanocarrier concentrations and different incubation times.

CONCLUSION

PEGylated calcium doped magnetic nanograin enhanced PUC19 plasmid expression into E. Coli and GFP protein expression in HEK-293 T cells compared to control. A polymerase chain reaction of the NeoR test shows that the transformed plasmids are of high quality.