Preparation and application of carbon dots derived from cherry blossom flowers

A Fluorescence Biosensor Based on Carbon Quantum Dots Prepared from Pomegranate Peel and T-Hg2+-T Mismatch for Hg2+ Detection

Mercury ions (Hg2+) can cause damage to human health, and thus, the study of the detection of Hg2+ is extraordinarily important in daily life. This work reported a fluorescence biosensor for the detection of Hg2+. The key point of this strategy was that the fluorescence of carbon quantum dots made from pomegranate peel (P-CQDs) was quenched by hemin, and restored after G-quadruplex binding with hemin. The presence of Hg2+ caused thymine (T)-rich DNA fragments to form T-Hg2+-T mismatches, and this change allowed the release of G-quadruplex. G-quadruplex could change the fluorescence of hemin/P-CQDs. P-CQDs exhibited excellent properties through characterization analysis, such as transmission electron microscope, X-ray photoelectron spectroscopy and Fourier transform infrared. This proposed fluorescence detection strategy established the linear ranges of Hg2+ from 1 nM to 50 nM. In conclusion, this simple biosensor had the advantages of strong sensitivity, high selectivity, and low cost for Hg2+ detection in environmental water samples.

Multifunctional natural derived carbon quantum dots from Withania somnifera (L.) - Antiviral activities against SARS-CoV-2 pseudoviron

Natural carbon dots (NCQDs) are expediently significant in the photo-, nano- and biomedical spheres owing to their facile synthesis, optical and physicochemical attributes. In the present study, three NCQDs are prepared and optimized from Withania somnifera (ASH) by one-step hydrothermal (bottom-up) method: HASHP (without dopant), nitrogen doped HASHNH3 (surface passivation using ammonia) and HASHEDA (surface passivation with ethylenediamine). The HR-TEM images reveal that HASHP, HASNH3, HASHEDA are spherically shaped with 2.5 ± 0.5 nm, 4 ± 1 nm and 5 ± 2 nm particle size, respectively, whereas FTIR confirms the aqueous solubility and nitrogen doping. The XRD patterns ensure that the NCQDs are amorphous and graphitic in nature. Comparatively, HASHNH3 (32.5%) and HASHEDA (27.6%) portray better fluorescence quantum yield than HASHP (5.6%). The increase in quantum yield for the doped NCQDs can be attributed to the surface passivation using ammonia and ethylenediamine. Surface passivation plays a crucial role in enhancing the fluorescence properties of quantum dots. The introduction of nitrogen through ammonia and ethylenediamine provides additional electronic states, possibly reducing non-radiative recombination sites and hence boosting the QY. In addition, an antiviral study unveils the striking potential of surface passivated NCQDs to curb Covid-19 crises with around 85% inhibition of SARS-CoV pseudoviron cells, which is better in comparison to the non-doped NCQDs. Hence, to understand the paramount efficacy of these NCQDs, a hypothesis on their possible mechanism of action against Covid-19 is discussed.

Multi-applications of carbon dots and polydopamine-coated carbon dots for Fe3+ detection, bioimaging, dopamine assay and photothermal therapy

Carbon dots (CDs) or CDs/polymer composites have been applied in numerous fields. Here, novel CDs were synthesized by carbonization of egg yolk, and characterized by TEM, FTIR, XPS and photoluminescence spectra. The CDs were found to be approximate sphere in shape with an average size of 4.46 ± 1.17 nm, and emitted bright blue photoluminescence under UV irradiation. The photoluminescence of CDs was found selectively quenched by Fe³⁺ in a linear manner in the range of 0.05-0.45 mM, meaning they could be applied for Fe³⁺ detection in solution. Moreover, the CDs could be uptaken by HepG2 cells to exhibit bright blue photoluminescence. The intensity could reflect the level of intracellular Fe³⁺, indicating they could be further used for cell imaging and intracellular Fe³⁺ monitoring. Next, dopamine was polymerized on the surface of CDs to obtain the polydopamine (PDA)-coated CDs (CDs@PDA). We found PDA coating could quench the photoluminescence of CDs via inner filter effect, and the degree of quenching was linearly related to the logarithm of DA concentration (Log C_DA). Also, the selectivity experiment indicated the method had a high selectivity for DA over a number of possible interfering species. This indicated the CDs in combination with Tris buffer could be potentially applied as the assay kit of dopamine. At last, the CDs@PDA exhibited excellent photothermal conversion capability, and they could efficiently kill HepG2 cells under NIR laser irradiation. Overall, the CDs and CDs@PDA in this work exhibited many excellent advantages, and could be potentially used for multi-applications, such as Fe³⁺ sensor in solution and cellular, cell imaging, dopamine assay kit, as well as photothermal agents for cancer therapy.

Easy Synthesis and Characterization of Novel Carbon Dots Using the One-Pot Green Method for Cancer Therapy

In this study, hyaluronic acid (HA) and carboxymethyl chitosan (CMCS) were used for the synthesis of novel targeted nanocarrier carbon dots (CDC-H) with photo-luminescence using a one-step hydrothermal method. Doxorubicin (DOX), a common chemotherapeutic agent, was loaded with the CDC-H through electrostatic interactions to form DOX-CDC-H complexes as a targeted antitumor drug delivery system. The synthesized CDC-H show a particle size of approximately 6 nm and a high fluorescence quantum yield of 11.64%. The physical and chemical character properties of CDC-H and DOX-CDC-H complexes were investigated using various techniques. The results show that CDC-H have stable luminescent properties and exhibit excellent water solubility. The in vitro release study showed that DOX-CDC-H exhibited pH-dependent release for 24 h. Confocal laser scanning microscopy was applied to investigate the potential of CDC-H for cell imaging and the cellular uptake of DOX-CDC-H in different cells (NIH-3T3 and 4T1 cells), and the results confirmed the target cell imaging and cellular uptake of DOX-CDC-H by specifically binding the CD44 receptors on the surface of tumor cells. The r MTT results suggest that the DOX-CDC-H complex may induce apoptosis in 4T1 cells, reducing the cytotoxicity of free DOX-induced apoptosis. In vivo antitumor experiments of DOX-CDC-H exhibited enhanced tumor cancer therapy. CDC-H have potential applications in bioimaging and antitumor drug delivery.

Transforming waste into value: pomelo-peel-based nitrogen-doped carbon dots for the highly selective detection of tetracycline

Tetracycline (TC) is widely used as a veterinary drug, and its residue in livestock products could enter the human body and cause damage. In this study, we developed an eco-friendly approach that utilized pomelo peel as a carbon source to synthesize new water-soluble N-doped carbon dots (P-NCDs) with blue fluorescence, obtaining a high quantum yield of up to 76.47% and achieving the goal of turning waste into value. Our prepared P-NCDs can selectively recognized TC, and their fluorescence was quenched based on the IFE. P-NCDs could measure the TC concentration in the linear range of 0–100 μmol L⁻¹ with a detection limit (LOD, S/N = 3) as low as 0.045 μmol L⁻¹. Furthermore, we have successfully applied our P-NCDs to the detection of TC in milk samples with convincing results within 90 s. Overall, our newly synthesized fluorescent sensor, P-NCDs, demonstrated huge potential to become an alternative way to detect TC in a simple, efficient, sensitive way without using any special instruments.

We developed an eco-friendly approach utilizing pomelo peel as a carbon source to synthesize P-NCDs, obtaining a high quantum yield of up to 76.47%. Our prepared P-NCDs can recognize tetracycline, and their fluorescence was quenched based on an IFE.