Triplex hairpin oligosensor for ultrasensitive determination of miRNA-155 as a cancer marker using Si quantum dots and Au nanoparticles.

In this study, a new triplex hairpin oligosensor was developed for the determination of a breast cancer biomarker using silicon quantum dots (Si QD) (λex = 370 nm, λem = 482 nm) as donor and gold nanoparticles (GNP) as an acceptor in a FRET (fluorescence resonance energy transfer) mechanism. In the triplex hairpin oligosensor, a triplex-forming oligonucleotide (TFO) labeled with Si QD and a single-strand DNA labeled with GNP form a hairpin shape with a triplex structure at the hairpin stem. In a turn-on mechanism, the triplex hairpin stem is opened in the presence of sequence-specific miRNA-155 which leads to the release of the Si QD-labeled TFO probe and recovery of the fluorescence signal. About 80 % of the fluorescence intensity of the Si QD-TFO is quenched in the triplex hairpin structure of the oligosensor and in the presence of 800 pM miRNA-155, the fluorescence signal recovered to 57.7 % of its initial value. The LOD of about 10 pM was obtained. The designed triplex-based biosensor can discriminate concentrations of breast cancer biomarkers with high selectivity.

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.

Potential Energy Surfaces of Vinylogous Wolff Rearrangement: NBO Analysis and Molecular Dynamic Simulation.

The potential energy surfaces of the Vinylogous Wolff Rearrangement, an alternative process for the Wolff Rearrangement that takes place ß,γ-unsaturated diazoketones have been fully explored employing M062X model chemistry and in a complementary task by means of the CASSCF method. The NBO analysis has been invoked to reveal the alternations of orbital occupancies and their stabilization energies through some of the critical structures located on the pathways. The calculations establish a two steps process for each pathway involving a second higher energy transition state that seems likely to be the rate determining step in agreement with experimental results. Energy analysis indicates more feasibility of the pathway including diradical intermediate. The most striking feature of the study concerns the finding out a transition state providing a channel in between two pathways through interconversion of the two keys bicyclo[2.1.0]pentanone and diradical intermediates.

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.

Biodegradation of Alprazolam in Pharmaceutical Wastewater Using Mesoporous Nanoparticles-Adhered Pseudomonas stutzeri.

The release of pharmaceutical wastewaters in the environment is of great concern due to the presence of persistent organic pollutants with toxic effects on environment and human health. Treatment of these wastewaters with microorganisms has gained increasing attention, as they can efficiently biodegrade and remove contaminants from the aqueous environments. In this respect, bacterial immobilization with inorganic nanoparticles provides a number of advantages, in terms of ease of processing, increased concentration of the pollutant in proximity of the cell surface, and long-term reusability. In the present study, MCM-41 mesoporous silica nanoparticles (MSN) were immobilized on a selected bacterial strain to remove alprazolam, a persistent pharmaceutical compound, from contaminated water. First, biodegrading microorganisms were collected from pharmaceutical wastewater, and Pseudomonas stutzeri was isolated as a bacterial strain showing high ability to tolerate and consume alprazolam as the only source for carbon and energy. Then, the ability of MSN-adhered Pseudomonas stutzeri bacteria was assessed to biodegrade alprazolam using quantitative HPLC analysis. The results indicated that after 20 days in optimum conditions, MSN-adhered bacterial cells achieved 96% biodegradation efficiency in comparison to the 87% biodegradation ability of Pseudomonas stutzeri freely suspended cells. Kinetic study showed that the degradation process obeys a first order reaction. In addition, the kinetic constants for the MSN-adhered bacteria were higher than those of the bacteria alone.

Selective aptamer conjugation to silver-coated magnetite nanoparticles for magnetic solid-phase extraction of trace amounts of Pb2+ ions.

Herein, a novel aptamer-functionalized magnetic adsorbent was developed and combined with magnetic solid-phase extraction (MSPE) for the specific enrichment of Pb2+ ions prior to flame atomic absorption spectrometric detection. First, silver-coated magnetite core-shell nanoparticles (Fe3O4@Ag MNPs) were synthesized by the chemical reduction of silver ions on the surface of magnetite nanoparticles. After that, the selective DNA aptamer against Pb2+ was conjugated on the surface of the synthesized nanoparticles to form aptamer-modified magnetic nanoparticles (Fe3O4@Ag-APT). The characterization of the prepared adsorbent was performed through SEM imaging, XRD, FT-IR, EDX, and DRS instruments. The influence of the various experimental parameters on the adsorption and desorption steps in MSPE was investigated via Taguchi experimental design to optimize different parameters. Under the optimized conditions, the Pb2+ calibration graph was linear in the range of 33-1000 µg L-1. The relative standard deviation (RSD%) of the method for six replicates containing 100 µg L-1 of Pb2+ ions was 0.34%. Furthermore, the limit of detection (LOD) and the limit of quantification (LOQ) were 10 µg L-1 and 33.3 µg L-1, respectively. Finally, the applicability of the proposed method was successfully confirmed by preconcentration and determination of trace amounts of Pb2+ ions in tap and seawater samples. We showed a proof of concept for Fe3O4@Ag-APT as an efficient bio-adsorbent, offering a promising strategy for the specific binding/removal of toxic heavy metal ions.

A label-free photoelectrochemical DNA biosensor using a quantum dot-dendrimer nanocomposite.

A novel label-free photoelectrochemical biosensing method for highly sensitive and specific detection of DNA hybridization using a CdS quantum dot (QD)-dendrimer nanocomposite is presented. A molecular beacon (MB) was assembled on a gold-nanoparticle-modified indium tin oxide electrode surface. Hybridization to a complementary target DNA disrupts the stem-loop structure of the MB, which was afterward labeled with the QD-dendrimer nanocomposite. The modified indium tin oxide electrode showed a stable anodic photocurrent response at 300 mV (vs Ag/AgCl) to light excitation at 410 nm in the presence of 0.1 M ascorbic acid as an electron donor. The protocol developed integrates the specificity of an MB for molecular recognition and the advantages of gold nanoparticles for increasing the loading capacity of the MB on the electrode surface and accelerating the electron transfer. Moreover, the photocurrent was greatly enhanced because of the high loading of QDs by the dendrimer, which eliminated the surface defects of CdS QDs and prevented recombination of their photogenerated electron-hole pairs. Under the optimal conditions, a linear relationship between the increase of photocurrent and target DNA concentration was obtained in the range from 1 fM to 0.1 nM, with a detection limit of 0.5 fM. The sequence-specificity experiment showed that one or three mismatches of DNA bases could be discriminated. This photoelectrochemical method is a prospective technique for DNA hybridization detection because of its great advantages: label-free, high sensitivity and specificity, low cost, and easy fabrication. This could create a new platform for the application of CdS QD-dendrimer nanocomposites in photoelectrochemical bioanalysis. Graphical abstract.

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.

Synthesis of Functionalized Magnetite Titanium Dioxide Nanocomposite for Removal of Acid Fuchsine Dye.

OBJECTIVE: In this research, a novel magnetite titanium dioxide nanocomposite functionalized by amine groups (Fe3O4@SiO2@TiO2-NH2) was synthesized and its ability for efficient removal of Acid Fuchsine as an anionic dye from aqueous solutions was investigated. METHOD: The core-shell structure of Fe3O4@SiO2@TiO2 was prepared using Fe3O4 as magnetic core, tetra ethyl orthosilicate as silica and tetra butyl titanate as titanium source for shell. The synthesized nanocomposites (particle size lower than 44 nm) were characterized by FT-IR, XRD, DRS, SEM and TGA instruments. The various experimental parameters affecting dye removal efficiency were investigated and optimized using Taguchi fractional factorial design. RESULTS: The synthesized adsorbent showed the highest removal efficiency of Acid Fuchsine (99 %) at pH= 3.5, without salt addition and during stirring at contact times less than 10 minutes. The study of kinetic models at two concentration levels showed the fast dye sorption on the surface of proposed nanocomposites with pseudo second order kinetic model (R2=1). Also, the fitting of Acid Fuchsine sorption data to Freundlich, Langmuir and Temkin isotherms suggested that Freundlich model gave a better fitting than other models (R2=0.9936, n=2). CONCLUSION: Good chemical stability, excellent magnetic properties, very fast adsorption kinetics and high removal efficiency make the synthesized nanocomposite as a proper recoverable sorbent for removal of Acid Fuchsine dye from wastewaters.

Comparison of adsorption and photo-Fenton processes for phenol and paracetamol removing from aqueous solutions: single and binary systems.

In the present study, adsorption and photo-Fenton processes have been compared for the removal of phenol and paracetamol from aqueous solutions in a single and binary systems. NaX nanozeolites and cobalt ferrite nanoparticles were used during adsorption and photo-Fenton processes, respectively. Both nanoparticles were synthesized using microwave heating method. The synthesized nanoparticles were characterized using powder X-ray diffraction (XRD) and scanning electronic microscopy (SEM) analysis. Based on results, more than 99% removing percentages of phenol and paracetamol were obtained during photo-Fenton process at initial concentrations of 10, 20, 50, 100 and 200 mg/L of phenol and paracetamol. Moreover, the complete removing of phenol and paracetamol was only achieved at lower initial concentrations than 10 mg/L for phenol and paracetamol during adsorption process. The results showed a significant dependence of the phenol and paracetamol removing on the initial concentrations of phenol and paracetamol for selection of process. The photo-Fenton process could be considered an alternative method in higher initial concentrations of phenol and paracetamol. However, the adsorption process due to economical issue was preferred for phenol and paracetamol removing at lower initial concentrations. The kinetic data of photo-Fenton and adsorption processes were well described using first-order and pseudo-second-order kinetic models. The results of phenol and paracetamol removing in a binary system confirmed the obtained results of single removing of phenol and paracetamol in selection of process.

Electrochemiluminescence detection of near single DNA molecules by using quantum dots-dendrimer nanocomposites for signal amplification.

An ultrasensitive electrochemiluminescent biosensor was developed for detection of near single DNA molecules with a linear range of 7 orders of magnitude by combining the specific recognition of a molecular beacon with signal amplification of quantum dots-dendrimer nanocomposites.

Potentiometric detection of mercury(II) ions using a carbon paste electrode modified with substituted thiourea-functionalized highly ordered nanoporous silica.

A potentiometric sensor is reported for the mercury(II) detection, which uses substituted thiourea-functionalized nanoporous silica (FTU-LUS-1) as the sensitive material. Substituted thiourea (FTU) and FTU-LUS-1 were first prepared and then characterized by 1H NMR, 19F NMR, 13C NMR, FTIR, XRD, TG and CNS elemental analysis. The electrodes with FTU-LUS-1 proportion of 10.0 wt% demonstrated very stable potentials. The prepared electrodes exhibit a Nernstian slope of 28.4 +/- 1.0 mV decade(-1) for mercury(II) ion over a wide concentration range of 1.0 x 10(-7) to 1.0 x 10(-1) mol dm(-3). The electrode exhibited a detection limit of 7.0 x 10(-8) mol dm(-3). Moreover, the selectivity coefficient, response time, performance, sensitivity and stability of the modified electrode were investigated. The electrode presented a response time of about 35 s, a high performance and sensitivity in a wide range of cation activities as well as good long term stability (more than 9 months). The method was satisfactory and could also be used to monitor the mercury(II) ion concentration in waste water and fish samples.