Vinyl-functionalized polyphenolic-carbon dot-based fluorometric turn-off-on biosensor for the dual detection of mercury and cysteine and their in vivo sensing in zebrafish larvae.

The fluorometric turn-off-on biosensor was developed for the ultra-sensitive detection of mercury (Hg2+) and cysteine (Cys) utilizing the highly fluorescent carbon dots (CDs). Herein, the sophisticated low-temperature reflux-mediated reaction was adopted using precursors namely citric acid (CA) and polyphenolic kaempferol (KMP) by using dimethylformamide (DMF) as a solvent. The resulting CDs (i.e., CKCDs) were in the highly negative charged groups (-OH) presented with a bright-orange fluorescence. These CKCDs were functionalized with 4-vinylaniline (4-VA) by employing EDC/NHS coupling reaction, which switched its photoluminescence (PL) towards the strong-blue colored emission and termed as V-CKCDs. The functionalized V-CKCDs can be capable enough to detect mercury via the strong electrostatic interactions between positively charged Hg2+ cations and negatively charged anions (-OH groups). Hence, an adequate fluorescence quenching was observed in V-CKCDs with the lowest concentrations of Hg2+ around 0.5 µM. Significantly, after adding the complex of V-CKCDs-Hg2+ to the Cys, the fluorescence enhancement was observed. This might be attributed from the strong interactions between Hg2+ in the fluorescence sensing system and thiol (-SH) moieties from the Cys. The developed V-CKCDs are highly sensitive for detecting Hg2+ and Cys, which showed detection limits of 10.6 and 42. 48 nM, respectively. Also, the in vivo studies were investigated in zebrafish larvae using V-CKCDs for the detection of Hg2+ and Cys. The V-CKCDs were investigated in the real water samples and human serum to detect Hg2+ and Cys, respectively.

Ruthenium(II)-curcumin liposome nanoparticles: Synthesis, characterization, and their effects against cervical cancer.

Ruthenium complexes have increased the scope for improvement in current cancer treatment by replacing platinum-based drugs. However, to reduce metal-associated toxicity, a biocompatible flavonoid, such as curcumin, is indispensable, as it offers uncompensated therapeutic benefits through formation of complexes. In this study, we synthesized metal-based flavonoid complexes using ruthenium(II) and curcumin by adopting a convenient reflux reaction, represented as Ru-Cur complexes. These complexes were thoroughly characterized using 1H, 13C NMR, XPS, FT-IR, and UV-vis spectroscopy. As curcumin is sparingly soluble in water and has poor chemical stability, we loaded Ru-Cur complexes into liposomes and further formed nanoparticles (NPs) using the thin layer evaporation method. These were named Ru-Cur loaded liposome nanoparticles (RCLNPs). The effects of RCLNPs on cell proliferation was investigated using human cervical cancer cell lines (HeLa). These RCLNPs exhibited significant cytotoxicity in HeLa cells. The anticancer properties of RCLNPs were studied using reactive oxygen species (ROS), LDH, and MTT assays as well as live-dead staining. Nuclear damage studies of RCLNPs were performed in HeLa cells using the Hoechst staining assay.

Fiber-optic biosensor based on the laccase immobilization on silica-functionalized fluorescent carbon dots for the detection of dopamine and multi-color imaging applications in neuroblastoma cells.

An efficient and cost-effective biosensor is of the great demand for the detection of the biologically significant neurotransmitter dopamine. In this context, enzymatic biosensors show excellent sensitivity and selectivity. In this study, we developed a laccase immobilized fiber-optic biosensor based on the fluorescence principle for the detection of dopamine. To design this biosensor, we used microwave irradiation to synthesize carbon dots (CDs) using curcumin and dimethylformamide, and the resulting CDs were called CDD-CDs. These were functionalized with a silicon precursor, 3-(aminopropyl)-triethoxysilane, and were referred to as APT-CDs. Furthermore, laccase was covalently immobilized to the APT-CDs to construct a novel bioprobe. The CDD-CDs, APT-CDs, and bioprobe showed orange (λem = 586 nm) green (λem = 533 nm), and blue-colored emissions (λem = 476 nm) at 430, 380, and 360 nm excitation wavelengths, respectively. The CDD-CDs and bioprobe showed quantum yields of 14.8% and 10.2%, respectively. The CDD-CDs displayed solvatochromism in various solvents. Bioprobe showed a significant fluorescence quenching for dopamine in the linear range of 0-30 µM with a detection limit of 41.2 nM. Bioprobe was immobilized on the tapered optical fiber using ethyl cellulose by a simple dip-coating method and investigated for multi-color imaging applications. The resulting tapered optical fiber achieved a satisfactory detection limit of 46.4 nM in the dopamine concentration range of 0-10 µM. The bioprobe demonstrated high biocompatibility, long-lasting photostability, and thermal stability, and had sufficient cytotoxicity in human neuroblastoma cells (SH-SY5Y) with excellent multi-color imaging potential. The practicality of the bioprobe was investigated in human serum and cerebrospinal fluid.

Lanthanum mediated rutin yellow-fluorescent carbon dots as multifaceted sensing probes for the detection of calcium ions in melanoma and plant cells.

Calcium (Ca2 +) as a signaling ion and intracellular second messenger plays a crucial role in living organisms for various cellular functions. In the present work, we have designed a novel yellow-fluorescent carbon dots (LERCDs) using lanthanum, ethylenediaminetetraacetic acid (EDTA), and rutin as precursors for the sensing of Ca2 + ions. In this sense, a combination of hydrothermal and reflux methods was adopted. The as-designed LERCDs display bright yellow color emission in the aqueous solutions with a high quantum yield (23.8%). The LERCDs showed excitation-independent emission property along with magnificent photostability and time stability. The LERCDs show potential fluorescence quenching response towards the Ca2+ ions in the concentration range of 0-25 µM with a detection limit of 2.19 µM. The LERCDs have studied for extracellular sensing of Ca2 + ions in both melanoma cell lines (A375) and onion epidermal cells by employing fluorescence microscopy. The LERCDs facilitate low cytotoxicity and superior biocompatibility features in A375 cells. The practicality of LERCDs was studied in biological samples like the human serum.

Biosynthesized Highly Stable Au/C Nanodots: Ideal Probes for the Selective and Sensitive Detection of Hg2+ Ions.

The enormous ongoing industrial development has caused serious water pollution which has become a major crisis, particularly in developing countries. Among the various water pollutants, non-biodegradable heavy metal ions are the most prevalent. Thus, trace-level detection of these metal ions using a simple technique is essential. To address this issue, we have developed a fluorescent probe of Au/C nanodots (GCNDs-gold carbon nanodots) using an eco-friendly method based on an extract from waste onion leaves (Allium cepa-red onions). The leaves are rich in many flavonoids, playing a vital role in the formation of GCNDs. Transmission electron microscopy (TEM) and Scanning transmission electron microscopy-Energy-dispersive X-ray spectroscopy (STEM-EDS) elemental mapping clearly indicated that the newly synthesized materials are approximately 2 nm in size. The resulting GCNDs exhibited a strong orange fluorescence with excitation at 380 nm and emission at 610 nm. The GCNDs were applied as a fluorescent probe for the detection of Hg2+ ions. They can detect ultra-trace concentrations of Hg2+ with a detection limit of 1.3 nM. The X-ray photoelectron spectroscopy results facilitated the identification of a clear detection mechanism. We also used the new probe on a real river water sample. The newly developed sensor is highly stable with a strong fluorescent property and can be used for various applications such as in catalysis and biomedicine.