A smart 19F and 1H MRI probe with self‐immolative linker as a versatile tool for detection of enzymes

Here we report on a dual‐modal ¹⁹F and ¹H MRI paramagnetic probe with a self‐immolative linker, Gd–DOMF–Gal. The enzymatic conversion of this probe by β‐galactosidase resulted in a simultaneous turning on of the fluorine signal and changed ability of the Gd³⁺ complex to modulate the ¹H MR signal intensity of the surrounding water molecules. A versatile imaging platform for monitoring a variety of enzymes by ¹⁹F and ¹H MRI using this molecular design is proposed. Copyright © 2012 John Wiley & Sons, Ltd.     

Facile synthesis of size-controlled Fe2O3 nanoparticle-decorated carbon nanotubes for highly sensitive H2S detection

Hydrogen sulfide (H₂S) is one of the most plentiful toxic gases in a real-life and causes a collapse of the nervous system and a disturbance of the cellular respiration. Therefore, highly sensitive and selective H₂S gas sensor systems are becoming increasingly important in environmental monitoring and safety. In this report, we suggest the facile synthesis method of the Fe₂O₃ particles uniformly decorated on carbon nanotubes (Fe₂O₃@CNT) to detect H₂S gas using oxidative co-polymerization (pyrrole and 3-carboxylated pyrrole) and heat treatment. The as prepared Fe₂O₃@CNT-based sensor electrode is highly sensitive (as low as 1 ppm), selective and stable to H₂S gas at 25 °C, which shows promise for operating in medical diagnosis and environment monitoring. Excellent performance of the Fe₂O₃@CNT is due to the unique morphology of the nanocomposites made from uniformly dispersed Fe₂O₃ nanoparticles on the carbon surface without aggregation.

Fe₂O₃ uniformly dispersed on carbon nanotubes are synthesized using facile oxidative co-polymerization of monomers followed by heat treatment to apply electrode materials for a highly sensitive H₂S chemical sensor system.     

A ratiometric fluorescence probe for the selective detection of H2S in serum using a pyrene-DPA–Cd2+ complex

A ratiometric and selective hydrogen sulfide (H₂S) detection probe was proposed based on the pyrene-DPA–Cd²⁺ complex through the metal ion displacement approach (MDA) mechanism. While most MDA-based fluorescence probes with paramagnetic Cu²⁺ have focused on the development of a simple turn-on sensor using the broad spectral range of fluorescence enhancement, this ratiometric probe exhibited unchanged monomer emission as a built-in internal reference with an increase in excimer emission with added H₂S. The demonstrated probe showed a rapid response (within 1 min) and a high sensitivity, with 70 nM as the limit of detection. The selectivity for H₂S over cysteine, homocysteine and glutathione was confirmed, and reliable fluorescence enhancement, which could be monitored by the naked eye, was observed upon irradiation with handheld UV light. In addition, this detection system was successfully applied to detect H₂S in human serum without interference from biological molecules.

The pyrene-DPA–Cd²⁺ complex is demonstrated as a ratiometric fluorescence probe for selective hydrogen sulfide detection in serum based on a metal displacement approach.     

Facile synthesis of carbon nitride quantum dots as a highly selective and sensitive fluorescent sensor for the tetracycline detection

Enhanced blue fluorescent carbon nitride quantum dots (g-C₃N₄QDs) were synthesized by a simple solvothermal “tailoring” process from bulk g-C₃N₄ and analyzed by various characterization methods. The as-obtained g-C₃N₄QDs were successfully applied in the determination of tetracycline (TC) with a good linear relationship in the range of 0.23–202.70 μM. The proposed fluorescent sensor shows excellent stability, good repeatability, high selectivity and outstanding sensitivity to TC with a low detection limit of 0.19 μM. The fluorescence quenching mechanism of g-C₃N₄QDs with TC was mainly governed by static quenching and the inner filter effect. The method was successfully applied to monitor TC in tap water and milk powder samples.

The g-C₃N₄QDs were synthesized by a simple solvothermal “tailoring” process from bulk g-C₃N₄ which have a “strong quenching” behaviour in the presence of TC. The proposed fluorescent sensor has been successfully applied to detect TC in actual samples.     

A novel quinoline derivative as a highly selective and sensitive fluorescent sensor for Fe3+ detection

In this research, a novel selective and sensitive fluorescent sensor for detecting Fe³⁺ was designed and synthesized; it revealed an obvious fluorescence quenching effect upon addition of Fe³⁺, and possessed the quantitative analysis ability on account of the formation of a 1 : 1 metal–ligand complex. Furthermore, the density functional theory calculations were utilized to study the molecular orbitals as well as the spatial structure. Simultaneously, the cell experiments and zebra fish experiments verified the application value of the sensor in the biological field.

A novel selective and sensitive fluorescent sensor for detecting Fe³⁺ was designed and synthesized; it revealed obvious fluorescence quenching effect upon addition of Fe³⁺, and possessed the quantitative analysis ability on account of the formation of a 1 : 1 metal–ligand complex.     

Gum acacia-based silver nanoparticles as a highly selective and sensitive dual nanosensor for Hg(ii) and fluorescence turn-off sensor for S2− and malachite green detection

A facile and green method was adopted to synthesize highly selective gum acacia-mediated silver nanoparticles as dual sensor (fluorescence turn-on and colorimetric) for Hg(ii) and fluorescence turn-off sensor for S²⁻ and malachite green. The mechanism proposed for a dual response towards Hg(ii) is the redox reaction between Ag(0) and Hg(ii), resulting in the formation of Ag(i) and Hg(0) and electron transfer from gum acacia to Ag(i), which further leads to the formation of an Ag@Hg nanoalloy. The enhanced fluorescence signal was quenched selectively by S²⁻ owing to the formation of Ag₂S and HgS. The reported nanosensor was found to be useful for sensing malachite green via the inner filter effect. The linear ranges were 3 nmol L⁻¹ to 13 μmol L⁻¹ for Hg(ii), 3–170 μmol L⁻¹ for S²⁻ and 7–80 μmol L⁻¹ for malachite green, and the corresponding detection limits were 2.1 nmol L⁻¹ for Hg(ii), 1.3 μmol L⁻¹ for S²⁻ and 1.6 μmol L⁻¹ for malachite green.

Gum acacia-stabilized silver nanoparticles for the detection of Hg(ii), S²⁻ and malachite green.     

Bimetallic Au–Pd alloy nanoparticles supported on MIL-101(Cr) as highly efficient catalysts for selective hydrogenation of 1,3-butadiene

Gold–palladium (Au–Pd) bimetallic nanoparticle (NP) catalysts supported on MIL-101(Cr) with Au : Pd mole ratios ranging from 1 : 3 to 3 : 1 were prepared through coimpregnation and H₂ reduction. Au–Pd NPs were homogeneously distributed on the MIL-101(Cr) with mean particle sizes of 5.6 nm. EDS and XPS analyses showed that bimetallic Au–Pd alloys were formed in the Au(2)Pd(1)/MIL-101(Cr). The catalytic performance of the catalysts was explored in the selective 1,3-butadiene hydrogenation at 30–80 °C on a continuous fixed bed flow quartz reactor. The bimetallic Au–Pd alloy particles stabilized by MIL-101(Cr) presented improved catalytic performance. The as-synthesized bimetallic Au(2)Pd(1)/MIL-101(Cr) with 2 : 1 Au : Pd mole ratio showed the best balance between the activity and butene selectivity in the selective 1,3-butadiene hydrogenation. The Au–Pd bimetallic-supported catalysts can be reused in at least three runs. The work affords a reference on the utilization of a MOF and alloy nanoparticles to develop high-efficiency catalysts.

Bimetallic Au–Pd alloy particles stabilized by MIL-101(Cr) showed high activity and butene selectivity for 1,3-butadiene hydrogenation reaction.     

Synthesis of a 2D Cu@TiO2 composite via the design of a 1D Cu-based coordination polymer precursor for efficient and selective photodegradation of dyes

A 2D Cu@TiO₂ composite with a porous and crystalline structure was successfully synthesized via one-step and low-temperature calcination of a 1D Cu-based coordination polymer (Cu-CP), namely [Cu₂(3-dpha)(1,4-NDC)₂(H₂O)₃]_n (3-dpha = N,N′-bis(3-pyridyl)adipamide and 1,4-H₂NDC = 1,4-naphthalenedicarboxylic acid). Moreover, the Cu@TiO₂ membrane was fabricated by a simple filtration of the as-grown Cu@TiO₂ composite. Compared with the benchmark TiO₂ photocatalyst, the Cu@TiO₂ composite material with high specific surface area and reduced photogenerated electron–hole ratio exhibited good photodegradation activity and durability for gentian violet (GV), which could be attributed to the combined effect of co-doping of Cu and TiO₂ structure. Furthermore, the ˙OH and ˙O₂⁻ radicals were predicted to dominate the photocatalytic process. Therefore, this new efficient photocatalyst is a promising candidate for efficient and selective photodegradation of organic pollutants.

A 2D Cu@TiO₂ composite was synthesized via low-temperature calcination of a 1D Cu-CP. Moreover, the Cu@TiO₂ membrane was fabricated by a simple filtration of the Cu@TiO₂ composite which exhibited selective photodegradation activity for GV.     

Amine-functionalized MIL-53(Al) with embedded ruthenium nanoparticles as a highly efficient catalyst for the hydrolytic dehydrogenation of ammonia borane

Well-dispersed ruthenium nanoparticles (Ru NPs) are immobilized within the pores of amine-functionalized MIL-53 via an in situ impregnation-reduction method. The resulting Ru/MIL-53(Al)-NH₂ catalyst exhibits superior catalytic performance for the dehydrogenation of ammonia borane (AB) at ambient temperature relative to the Ru/MIL-53(Al) catalyst; it has a turnover frequency (TOF) of 287 mol H₂ min⁻¹ (mol Ru)⁻¹ and an activation energy (E_a) of 30.5 kJ mol⁻¹. The amine groups present in the MIL-53(Al)-NH₂ framework facilitate the formation and stabilization of ultra-small Ru NPs by preventing their aggregation. Additionally, the Ru/MIL-53(Al)-NH₂ catalyst exhibits satisfactory durability and reusability: 72.4% and 86.3% of the initial catalytic activity was maintained after the fifth successive cycle of the hydrolytic dehydrogenation of AB in the two respective tests.

The performance of Ru-based catalyst for hydrolysis of AB can be significantly enhanced through amine-functionalization of the MOF material.     

Optical projection tomography as a tool for 3D imaging of hydrogels

An Optical Projection Tomography (OPT) system was developed and optimized to image 3D tissue engineered products based in hydrogels. We develop pre-reconstruction algorithms to get the best result from the reconstruction procedure, which include correction of the illumination and determination of sample center of rotation (CoR). Existing methods for CoR determination based on the detection of the maximum variance of reconstructed slices failed, so we develop a new CoR search method based in the detection of the variance sharpest local maximum. We show the capabilities of the system to give quantitative information of different types of hydrogels that may be useful in its characterization.OCIS codes: (100.6890) Three-dimensional image processing, (100.6950) Tomographic image processing, (160.1435) Biomaterials, (170.3010) Image reconstruction techniques     

A highly selective colorimetric fluorescent probe for detection of Hg2+ and its application on test strips

An efficient fluorescent probe Pyr-Rhy based on pyrazole was developed, which can detect Hg²⁺ in water. Its fluorescence properties were studied by UV-vis and fluorescence spectroscopy, and the study results indicated that this probe can selectively detect Hg²⁺via complexation reaction, and then cause a remarkable color change from colorless to pink and a strong fluorescence enhancement can be observed. Furthermore, this probe showed high sensitivity with the detection limit down to 2.07 × 10⁻⁸ M, and its stoichiometric ratio toward Hg²⁺ ions was 1 : 1. The sensing mechanism was investigated by Job''s plot ¹H NMR titrations, and FT-IR spectra analysis, which demonstrated a chelation-enhanced fluorescence (CHEF) mechanism. More importantly, obvious color changes of sensor Pyr-Rhy can be observed when it was impregnated on filter paper testing strips and immersed in Hg²⁺ solution (water as solution), indicating its potential application for trace Hg²⁺ detection in environmental samples.

An efficient fluorescent probe Pyr-Rhy based on pyrazole was developed, which can detect Hg²⁺ in water.     

A highly selective TPE-based AIE fluorescent probe is developed for the detection of Ag+

The detection of Ag⁺ in the environment is very important to determine the level of pollution from silver complexes, which have caused various human health problems. Herein, an aggregation-induced emission (AIE) chromophore (tetraphenylethane, TPE) attached to a benzimidazole group (tetra-benzimidazole, TBI–TPE) is synthesized and utilized to detect Ag⁺ in the environment. The strong chelating effect between the benzimidazole group and Ag⁺ leads to the formation of aggregates, and strong yellow fluorescence signals were observed after adding Ag⁺ into a TBI–TPE solution. The stoichiometry of the complex of TBI–TPE and Ag⁺ was established to be 1 : 2 using photochemical and mass spectra measurements. The detection limit of the Ag⁺ assay is 90 nM with a linear range from 100 nM to 6 μM. This study provides a facile method to determine Ag⁺ in real environmental samples with satisfactory results.

We develop a highly selective TPE-based AIE fluorescent probe containing a benzimidazole group for the detection of Ag⁺.     

The C2N surface as a highly selective sensor for the detection of nitrogen iodide from a mixture of NX3 (X = Cl,Br, I) explosives

Explosives are quite toxic and destructive; therefore, it is necessary to not only detect them but also remove them. The adsorption behavior of NX₃ analytes (NCl₃, NBr₃ and NI₃) over the microporous C₂N surface was evaluated by DFT calculations. The nature of interactions between NX₃ and C₂N was characterized by adsorption energy, NCI, QTAIM, SAPT0, NBO, EDD and FMO analysis. The interaction energies of NX₃ with C₂N are in the range of −10.85 to −16.31 kcal mol⁻¹ and follow the order of NCl₃@C₂N > NBr₃@C₂N > NI₃@C₂N, respectively. The 3D isosurfaces and 2D-RGD graph of NCI analysis qualitatively confirmed the existence of halogen bonding interactions among the studied systems. Halogen bonding was quantified by SAPT0 component energy analysis. The SAPT0 results revealed that ΔE_disp (56.75%) is the dominant contributor towards interaction energy, whereas contributions from ΔE_elst and ΔE_ind are 29.41% and 14.34%, respectively. The QTAIM analysis also confirmed the presence of halogen bonding between atoms of NX₃ and C₂N surface. EDD analysis also validated NCI, QTAIM and NBO analysis. FMO analysis revealed that the adsorption of NI₃ on the C₂N surface caused the highest change in the E_HOMO–LUMO gap (from 5.71 to 4.15 eV), and resulted in high sensitivity and selectivity of the C₂N surface towards NI₃, as compared to other analytes. It is worth mentioning that in all complexes, a significant difference in the E_HOMO–LUMO gap was seen when electronic transitions occurred from the analyte to the C₂N surface.

Explosives are quite toxic and destructive; therefore, it is necessary to not only detect them but also remove them.     

Correction: A highly selective ratiometric fluorescent probe for the cascade detection of Zn2+ and H2PO4− and its application in living cell imaging

Correction for ‘A highly selective ratiometric fluorescent probe for the cascade detection of Zn²⁺ and H₂PO₄⁻ and its application in living cell imaging’ by Kui Du et al., RSC Adv., 2017, 7, 40615–40620.

Affiliation c was incomplete in the original publication; the corrected version is shown below.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.     

Complement factor H as a marker for detection of bladder cancer

BACKGROUND: The BTA TRAK and BTA stat tests for bladder cancer use monoclonal antibodies (mAbs) X13.2 and X52.1 to detect factor H (FH)-related material in urine. The exact ligands remain unknown. METHODS: Western blot analyses of purified FH, recombinant factor H-related protein 1 (FHR-1), and serum and urine samples were used to identify the ligands of X13.2 and X52.1. Recombinant FH constructs were used to identify the target sites of X13.2 and X52.1. To analyze whether natural ligands of FH could compete with its recognition by the capture mAb X52.1, we used surface plasmon resonance analysis. The role of the ligands of X52.1 in the BTA TRAK assay was tested with use of purified proteins and FH-depleted samples. RESULTS: X13.2 bound to domain 3 of FH and FH-like protein 1, whereas X52.1 bound to domain 18 of FH and to FHR-1. Using specific FH depletion from a bladder cancer patient's urine and purified FH, we demonstrated that FH is the ligand recognized by the BTA TRAK test. By contrast, FHR-1 in urine reduced the FH-dependent test signal. CONCLUSIONS: FH is a tumor marker for bladder cancer. To reveal the presence of bladder cancer, the BTA TRAK assay detects FH, whereas FHR-1 is able to partly inhibit this detection. This indicates a special mechanism for a diagnostic immunoassay based on the combined effect of simultaneous positive and negative signals in a single sample.     

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.     

The presence of a single-nucleotide mismatch in linker increases the fluorescence of guanine-enhanced DNA-templated Ag nanoclusters and their application for highly sensitive detection of cyanide

Fluorescence of DNA-templated silver nanoclusters can be enhanced by more than 100-fold by placing the nanoclusters in proximity to guanine-rich DNA sequences after hybridization. We found that the fluorescence of the guanine-enhanced silver nanoclusters is not increased with the guanine-rich DNA sequence closer to the silver nanoclusters. By studying the different numbers of mismatches in the linker sequences, we found that the presence of a single-nucleotide mismatch in the linker increases fluorescence more than the complementary nucleotide. Further study indicated the mismatch position of the linker sequence also affects the fluorescence of the hybridized DNA-Ag NCs. The evidence reported here indicated that the mismatch of the linker sequence affects the fluorescence enhancement of guanine-enhanced silver nanoclusters. We also found that DNA-Ag NCs is an excellent fluorescence sensor for cyanide, as cyanide effectively quenches the fluorescence of NCs at a very low concentration with high selectivity. Cyanide in the range from 0.10 μM to 0.35 μM could be linearly detected, with a detection limit of 25.6 nM.

Single-base mismatched G-rich enhanced DNA-Ag NCs for cyanide detection.     

3H]-[H-D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2] ([3H]CTOP), a potent and highly selective peptide for mu opioid receptors in rat brain

The cyclic, conformationally restricted octapeptide [3H]-[H-D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2] ([3H]CTOP) was synthesized and its binding to mu opioid receptors was characterized in rat brain membrane preparations. Association rates (k+1) of 1.25 x 10(8) M-1 min-1 and 2.49 x 10(8) M-1 min-1 at 25 and 37 degrees C, respectively, were obtained, whereas dissociation rates (k-1) at the same temperatures were 1.93 x 10(-2) min-1 and 1.03 x 10(-1) min-1 at 25 and 37 degrees C, respectively. Saturation isotherms of [3H]CTOP binding to rat brain membranes gave apparent Kd values of 0.16 and 0.41 nM at 25 and 37 degrees C, respectively. Maximal number of binding sites in rat brain membranes were found to be 94 and 81 fmol/mg of protein at 25 and 37 degrees C, respectively. [3H]CTOP binding over a concentration range of 0.1 to 10 nM was best fit by a one site model consistent with binding to a single site. The general effect of different metal ions and guanyl-5'-yl-imidodiphosphate on [3H]CTOP binding was to reduce its affinity. High concentrations (100 mM) of sodium also produced a reduction of the apparent mu receptor density. Utilizing the delta opioid receptor specific peptide [3H]-[D-Pen2,D-Pen5]enkephalin, CTOP appeared to be about 2000-fold more specific for mu vs. delta opioid receptor than naloxone. Specific [3H]CTOP binding was inhibited by a large number of opioid or opiate ligands.(ABSTRACT TRUNCATED AT 250 WORDS)     

A novel and fast responsive turn-on fluorescent probe for the highly selective detection of Cd2+ based on photo-induced electron transfer

A novel, highly sensitive and fast responsive turn-on fluorescence probe, 2,2′-((1E,1′E)-((1,10-phenanthroline-2,9-diyl)bis(methanylylidene)) bis(azanylylidene)) diphenol (ADMPA), for Cd²⁺ was successfully developed based on 2,9-dimethyl-1,10-phenanthroline and o-aminophenol. ADMPA showed a remarkable fluorescence enhancement toward Cd²⁺ against other competing cations, owing to the suppression of the photo-induced electron transfer (PET) and CH N isomerization. A good linear relationship (R² = 0.9960) was obtained between the emission intensity of ADMPA and the concentration of Cd²⁺ (0.25–2.5 μM) with a detection limit of 29.3 nM, which was much lower than that reported in literature. The binding stoichiometry between ADMPA and Cd²⁺ was 2 : 1 as confirmed by the Job''s Plot method, which was further confirmed by a ¹H NMR titration experiment. Moreover, the ADMPA probe was successfully applied to detect Cd²⁺ in real water samples with a quick response time of only 6.6 s, which was about 3–40 times faster than the reported cadmium ion probe.

A novel, highly sensitive and fast responsive turn-on fluorescence probe ADMPA for Cd²⁺ was successfully developed based on 2,9-dimethyl-1,10-phenanthroline and o-aminophenol.