A Chelation-enhanced Fluorescence Assay using Thiourea Capped Carbonaceous Fluorescent Nanoparticles for As (III) Detection in Water Samples.

Herein, we designed a sensitive and selective "Turn-On" fluorescence nanosensor using water-soluble carbonaceous fluorescent nanomaterials (CFNs) functionalized with thiourea (CFNs-Thiourea) for efficient detection of trace concentrations of arsenic (III) in aqueous samples. The CFNs and CFNs-Thiourea were characterized by transmission electron microscopy (TEM), UV-visible spectroscopy (UV-vis) and fourier transformed infrared spectroscopy (FTIR). The emission peak intensity of proposed nanosensor at 425 nm was gradually enhanced on arsenite addition in a wide detection range (3.3-828.5 µg L-1) attributed to the binding of arsenite species with sulfur groups of CFNs-Thiourea. The limit of detection (LOD) was 0.48 µg L-1 being much lower than the World Health Organization (WHO) recommended threshold value of 10 µg L-1. Furthermore, the as-prepared CFNs-Thiourea exhibited a superb selectivity for As (III) compared to various cations and anions, such as; NO3-, NO2-, F-, Ni2+, Fe3+, Cu2+, Ca2+, Mg2+, Zn2+, Fe2+, Hg2+, Pb2+, F-, Cl-, Mn2+, Cr3+, Co2+, Cd2+, Bi3+, Al3+ and As (V) at 100 folds concentration of As (III). The turn on fluorescence nanosensor was successfully exploited for quantification of arsenic in spiked water samples with acceptable efficiencies.

Understanding the bulk and interfacial structures of ternary and binary deep eutectic solvents with a constant potential method: a molecular dynamics study.

In the last decade, deep eutectic solvents (DESs) have emerged as promising electrolytes in supercapacitors and rechargeable batteries due to their unique properties, wide electrochemical windows, low viscosity, and high ionic conductivity. The molecular structural behavior of these solvents, which plays an important role in their efficiency is not deeply understood. Therefore, in this work, by considering two types of DES electrolytes, we investigate their bulk and interfacial structures at the molecular level using molecular dynamics studies. In this regard, two different DESs-a binary DES including choline chloride and urea in a 1 : 2 molar ratio, and a ternary DES containing choline chloride, urea, and ethylene glycol with a molar ratio of 1 : 1 : 2-are considered. For the bulk phase, the partial site-site and center of mass radial distribution functions (RDFs), the mean square displacement (MSD), and the self-diffusion coefficient of the ternary system are explored. We demonstrate that in deep eutectic solvents, in addition to hydrogen-bonding and long-range and short-range correlations, a variety of neutral species play crucial roles in the properties of the bulk phase. Furthermore, considering two graphene sheets as electrodes on both sides of the DES samples, the profiles of the number density, charge density, orientational order parameter, and electrostatic potentials at different potential conditions near the electrodes are investigated. The results reveal the presence of multilayers of the neutral species in the vicinity of electrodes in addition to the ionic components of both DES systems. Finally, the computed differential capacitances (Cd) for DESs disclose that the positive electrode capacitance is higher than that of the negative electrode, and in the ternary system, the total capacitance is greater than in the binary system. Our findings give a better perspective of a new generation of electrolytes at the molecular level for electric double-layer capacitors.

Carbon dots hybrid for dual fluorescent detection of microRNA-21 integrated bioimaging of MCF-7 using a microfluidic platform.

BACKGROUND: MicroRNAs have short sequences of 20 ~ 25-nucleotides which are similar among family members and play crucial regulatory roles in numerous biological processes, such as in cell development, metabolism, proliferation, differentiation, and apoptosis. RESULTS: We reported a strategy for the construction of a dual-emission fluorescent sensor using carbon dots (CDs) and confirmed their applications for ratiometric microRNA-21 sensing and bioimaging of cancer cells in a microfluidic device. The composition of blue CDs (B-CDs) and yellow CDs (Y-CDs) depicts dual-emission behavior which is centered at 409 and 543 nm under an excitation wavelength of 360 nm. With increasing microRNA-21 concentration, the robust and specific binding of DNA probe functionalized B-CDs to complementary microRNA-21 target induced perturbations of probe structure and led to changing fluorescence intensity in both wavelengths. Consequently, the ratio of turn-on signal to turn-off signal is greatly altered. With monitoring of the inherent ratiometric fluorescence variation (ΔF540nm/ΔF410nm), as-prepared BY-CDs were established as an efficient platform for ratiometric fluorescent microRNA-21 sensing, with a wide linear range of 0.15 fM to 2.46 pM and a detection limit of 50 aM. CONCLUSIONS: Furthermore, the proposed assay was applied for detecting microRNA-21 in dilute human serum samples with satisfactory recovery and also in MCF-7 cell lines in the range 3000 to 45,000 (cell mL-1) with a detection limit (3 cells in 10 µL), demonstrating the potential of the assay for clinic diagnosis of microRNA-associated disease. More importantly, the images revealed that MCF-7 cells well labeled with BY-CDs could exhibit the applicability of the proposed microfluidic system as an effective cell trapping device in bioimaging.

Ultrasensitive molecularly imprinted fluorescence sensor for simultaneous determination of CA125 and CA15-3 in human serum and OVCAR-3 and MCF-7 cells lines using Cd and Ni nanoclusters as new emitters.

In the clinical diagnosis of tumors, a single-marker immunoassay may lead to false results. Thus there is a need for an effective and valid method for the simultaneous measurement of multiple tumor markers. In this work, an efficient fluorescence immunosensor for the simultaneous measurement of CA125 and CA15-3 tumor markers was fabricated by utilizing the high selectivity of magnetic molecularly imprinted polymers (MMIPs) and the high sensitivity of a fluorescence (FL) method. Ni nanoclusters (Ni NCs) and noble Cd nanoclusters (Cd NCs) were introduced as efficient and economic emitters, and magnetic graphene oxide (GO-Fe3O4) was applied as a support material for surface molecularly imprinted polymers. Under the most favorable experimental conditions, the fluorescence intensity of the Cd NCs and Ni NCs gradually increased with increasing concentration of CA125 and CA15-3 antigens at a range of 0.0005-40 U mL-1, respectively, with a limit of detection (LOD) of 50 µU mL-1. The developed method had excellent properties including a broad linear range, good reproducibility, and simple operation for the clinical diagnosis of CA 125 and CA 15-3 tumor markers. This molecularly imprinted fluorescence sensor has the potential to be an effective clinical tool for the timely screening of breast cancer in human serum samples and OVCAR-3 and MCF-7 cell lines, and can be applied in clinical diagnostics.

Multienzymes activity of metals and metal oxide nanomaterials: applications from biotechnology to medicine and environmental engineering.

With the rapid advancement and progress of nanotechnology, nanomaterials with enzyme-like catalytic activity have fascinated the remarkable attention of researchers, due to their low cost, high operational stability, adjustable catalytic activity, and ease of recycling and reuse. Nanozymes can catalyze the same reactions as performed by enzymes in nature. In contrast the intrinsic shortcomings of natural enzymes such as high manufacturing cost, low operational stability, production complexity, harsh catalytic conditions and difficulties of recycling, did not limit their wide applications. The broad interest in enzymatic nanomaterial relies on their outstanding properties such as stability, high activity, and rigidity to harsh environments, long-term storage and easy preparation, which make them a convenient substitute instead of the native enzyme. These abilities make the nanozymes suitable for multiple applications in sensing and imaging, tissue engineering, environmental protection, satisfactory tumor diagnostic and therapeutic, because of distinguished properties compared with other artificial enzymes such as high biocompatibility, low toxicity, size dependent catalytic activities, large surface area for further bioconjugation or modification and also smart response to external stimuli. This review summarizes and highlights latest progress in applications of metal and metal oxide nanomaterials with enzyme/multienzyme mimicking activities. We cover the applications of sensing, cancer therapy, water treatment and anti-bacterial efficacy. We also put forward the current challenges and prospects in this research area, hoping to extension of this emerging field. In addition to therapeutic potential of nanozymes for disease prevention, their practical effects in diagnostics, to monitor the presence of SARS-CoV-2 and related biomarkers for future pandemics will be predicted.

CuO/Cu-MOF nanocomposite for highly sensitive detection of nitric oxide released from living cells using an electrochemical microfluidic device.

The integration of large surface area and high catalytic profiles of Cu-MOF and CuO nanoparticles is described toward electrochemical sensing of nitric oxide (NO) in a microfluidic platform. The CuO/Cu-MOF nanocomposite was prepared through hydrothermal method, and its formation was confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDS). The CuO/Cu-MOF nanostructured modified Au electrodes enabled electrocatalytic NO oxidation at 0.6 V vs. reference electrode, demonstrating linear response over a broad concentration range of 0.03-1 µM and 1-500 µM with a detection limit of 7.8 nM. The interference effect of organic molecules and common ions was negligible, and the sensing system demonstrated excellent stability. Finally, an electrochemical microfluidic NO sensor was developed to detect of NO released from cancer cells, which were stimulated by L-arginine. Furthermore, in the presence of Fe3+, the stressed cells produced more NO. This work offers considerable potential for its practical applications in clinical diagnostics through determination of chemical symptoms in microliter-volume biological samples. Electrochemical microfluidic NO sensor was developed for detection of NO released from cancer cells. This miniaturized device consumes less materials and provides the basis for greener analytical chemistry.

A strategy for visual optical determination of glucose based on a smartphone device using fluorescent boron-doped carbon nanoparticles as a light-up probe.

Boronic acid-doped carbon nanoparticles were prepared and are shown to undergo aggregation induced emission (AIE). The nanoparticle composite is a viable fluorescent probe for glucose determination by using the RGB technique and a smartphone. The structure and the chemical composition of the doped carbon nanoparticles were confirmed by SEM, TEM, FTIR and UV-vis spectroscopy. The combination of 4-carboxyphenylboronic acid with o-phenylenediamine and rhodamine B endowed the hybrid with high fluorescence intensity (quantum yield 46%). Compared with conventional two-step preparation of boronic acid-based fluorescent probes for glucose, the present one step synthesis strategy is simpler and more effective. The addition of glucose causes the formation of covalent bonds between the cis-diols group of glucose molecules and boronic acid moiety. Fluorescent intensity can be quantified using dual wavelengths simultaneously, where both increases, as the target analytes bind to the bronic acid. These variations was monitored by the smartphone camera, and the green channel intensities of the colored images were processed by using the RGB option of a smartphone. The assay works in the 32 µM to 2 mM glucose concentration range and has an 8 µM detection limit. The method was successfully used for the assay of glucose in diluted human serum. Graphical abstractThe fluorometric method was developed for determination of glucose using boron doped carbon nanoparticles (BCNBs). The BCNPs aggregate after covalent binding between the cis-diols of glucose and boronic acid. The green channel of the images is recorded by a smartphone camera.

Functionalized fluorescent carbon nanostructures for targeted imaging of cancer cells: a review.

This short review (with 72 refs.) summarizes the state of the art in fluorometric methods for targeted imaging of cancer cells and tumor tissues in order to differentiate between normal cells and cancer cells. Following an introduction into the field and after presenting an overview on the most commonly used carbon dots and graphene quantum dots, we describe methods based on peptide based targeting, aptamer based targeting, antibody based targeting, and ligand-based targeting. A concluding section summarizes the current state and challenges, and discusses future perspectives. Graphical abstract An overview is given on the applications of carbon dots (CDs) in target-specific imaging and differentiation of cancerous cells from normal cells. Several classes of ligands (including aptamers, peptides, antibodies), especially small molecules (such as FA)) have been reported for functionalizing of CDs.

Ratiometric enhanced fluorometric determination and imaging of intracellular microRNA-155 by using carbon dots, gold nanoparticles and rhodamine B for signal amplification.

An ultrasensitive and highly reliable ratiometric assay is described for the determination of microRNA-155. It works at the attomolar concentration level and has high selectivity which warrants its potential application in cancer biomarker tracking. The excellent performance of this method results from (a) the use of a hybrid conjugate prepared from Rhodamine B (RhB), carbon dots (CDs) and probe-microRNA, and (b) from the measurement of fluorescence resonance energy transfer (FRET) that is observed in the AuNP/target-microRNA system as a result of RNA hybridization. The dye RhB (emission peak at 580 nm) serves as an internal reference. The sensitivity of this assay is increased by about 30% because of the broad emissions of CDs (489 nm and 665 nm) through a sequential FRET phenomenon. RhB-CDs were covalently bio-conjugated to probe microRNA. In the presence of AuNPs, the fluorescence of the CDs is quenched, while in the presence of microRNA-155, the ratio of fluorescences at 489 and 665 nm (I489/I665) is enhanced again. A linear relationship exists between the ratio of fluorescence and the concentration of microRNA-155 in the range from 1 aM to 0.1 µM, and the detection limit is 0.3 aM. The assay was applied to quantitative studies of target microRNA-155 in multiple pathways associated with cancer progression in biological fluids include human serum samples and cancer cells. The nanoprobe also deliver clear signal to microRNA target in fixed and lived MDA-MB-231 cells. Graphical abstract A ratiometric FRET sensing method used for microRNA-155 detection at aM concentration level using CDs and AuNPs as donor-acceptor respectively and Rhodamine B as amplification reagent. The application of assay for imaging of microRNA-155 in fixed and live MDA-MB-231 cells is demonstrated.

A FRET immunosensor for sensitive detection of CA 15-3 tumor marker in human serum sample and breast cancer cells using antibody functionalized luminescent carbon-dots and AuNPs-dendrimer aptamer as donor-acceptor pair.

We proposed a FRET immunosensing for detection of CA15-3 tumor marker by highly biospecific interactions between CA 15-3 antigen and the corresponding antibody and aptamer. In this sandwich type immunoassay, CA15-3 antibody-functionalized carbon dots and AuNPs labeled PAMAM-Dendrimer/aptamer were used as donor/acceptor, respectively. When CA 15-3 Ag was added to homogenous immunoassay, the strong complex interaction between CA15-3 Ab-CA15-3 Ag- aptamer caused in more coming closer carbon dot and AuNPs and more decreasing fluorescence signal. The decreased fluorescence intensity was linear at three ranges including in concentration range 1.1 µUmL-1 to 16 µU mL-1 with regression of R2 = 0.9879, at the concentration range 16 µU mL-1 to 0.163 mU mL-1 with regression of R2 = 0.9944 and at the concentration range 0.163 mU mL-1 to 5.0 mU mL-1 with regression of R2 = 0.9805. The detection limit of the FRET immunoassay was 0.9 µU mL-1. This assay revealed good sensitivity and specificity with MDA-MB-231 breast cancer cells concentrations from 1000 to 40000 cells/mL with correlation coefficient of 0.9955 and detection limit of 300 cells/mL (3 cells in 10 µL of injected sample). In addition, this FRET immunosensing is applicable in diluted human serum. The recovery values were in the range of 95.86-96.97% for CA 15-3 Ag in spiked serum sample with RSD lower than 7.3%. The proposed immunoassay could be a valid model for establishing other immunoassays for detection of different cancer tumor markers with relevant antigens and antibodies.