Point-of-care testing of melamine via gas pressure readout using polythymine-coated Au@Pt nanoparticles through specific triple hydrogen-bonding recognition.

The adsorption of single-stranded oligonucleotides (ssDNA) on gold nanoparticles (AuNPs) could stabilize AuNPs against aggregation even at high salt concentrations, and similar phenomena have also been observed on Au core/Pt shell nanoparticles (Au@PtNPs). Inspired by the knowledge that thymine can easily recognize melamine by forming triple H-bonds in aqueous medium, in this contribution, using polythymine-coated Au@PtNPs as the probe, we demonstrated that the responsive aggregation of polyT55 stabilized Au@PtNPs could occur and therefore result in the significant inhibition of the catalysed gas-generation reaction, the decomposition of H2O2 to H2O and O2 catalyzed by Au@PtNPs. Consequently, a pressure-based signaling strategy was developed for highly sensitive and specific melamine detection not only in laboratory but also in point-of-care (POC) settings, and the correlation between the pressure change (ΔP) signal and the melamine concentration was found to be linear from 0.025 to 10.0 µM with a limit of detection of 6.4 nM, providing a convenient new alternative and new train of thought for the specific detection of melamine.

A gas pressure and colorimetric signal dual-mode strategy for sensitive detection of spermine using ssDNA-coated Au@Pt nanoparticles as the probe.

The naturally occurring spermine (Spm), as one of the many cationic polyamines, plays a key role in biological processes and is involved in a variety of diseases. The very similar structures among biogenic polyamines present a major challenge to achieve discriminative testing among them. In this contribution, using arbitrary ssDNA-coated Au@PtNPs as the probe, we demonstrated that a dual-mode strategy via a gas pressure and colorimetric signal readout can be used for the sensitive and specific detection of Spm, due to the target-responsive aggregation of the Au@PtNPs leading to the inhibition of the catalyzed gas-generation reaction and the colorimetric change of the Au@PtNP solution. The proposed pressure-based signaling strategy has a detection limit of 9.6 nM, and can be used not only in the laboratory but also in the point-of-care setting. Meanwhile, the colorimetric assay displays the advantage of being easily discerned with the naked eye. Compared with the traditional methods of chromatography and capillary electrophoresis combined with chemical derivatization, the strategy described here would provide a convenient new alternative for the specific detection of Spm in biological samples.

Point-of-Care Testing of Pathogenic Bacteria at the Single-Colony Level via Gas Pressure Readout Using Aptamer-Coated Magnetic CuFe2O4 and Vancomycin-Capped Platinum Nanoparticles.

Pressure measurements are performed everyday with simple devices, and in the field of analytical chemistry the pressure-based signaling strategy offers two important advantages, signal amplification and particular applicability in point-of-care settings. Herein, by using vancomycin (Van)-functionalized platinum nanoparticles (PtNPs@Van) and aptamer-coated magnetic CuFe2O4 nanoprobes dual-recognition units integrated with a catalyzed breakdown of H2O2 for O2 generation, we demonstrated that gas pressure can be used as a readout means for highly sensitive pathogenic bacteria identification and quantification. Using Staphylococcus aureus ( S. aureus) as a test case, integration of the molecular dual-recognition component with the catalyzed gas-generation reaction leads to a significant pressure change (Δ P), and the correlation between the concentration of S. aureus and the Δ P signal was found to be linear from 5.0 to 1.0 × 104 cfu/mL with a detection limit of 1.0 cfu/mL. Other nontarget bacteria show negative results, verifying the high specificity of the present strategy. When employed to assay S. aureus in saliva and milk samples, the approach shows recoveries from 93.3% to 107.1% with relative standard derivation (RSD) less than 8.8%. By the integration of catalyzed gas-generation reaction with the designed molecular recognition event, obviously the pressure-based signaling strategy could facilitate pathogenic bacteria identification and quantification not only in the laboratory but also in point-of-care settings, which could have great potential in the application of food safety and infectious disease diagnosis.

pH-Dependent photoluminescence "switch-on" nanosensors composed of silver nanoparticles and nitrogen and sulphur co-doped carbon dots for discriminative detection of biothiols.

Very close structure and property similarities among biothiols, such as glutathione (GSH), cysteine (Cys), and homocysteine (Hcy), present a major challenge to achieve their discriminative detection. In this contribution, a nanomaterial surface energy transfer (NSET) system was established to discriminate GSH from Cys and Hcy with the photoluminescence (PL) "switch-on" response. The nanosensor was constructed using nitrogen and sulphur co-doped carbon dots (N,S-CDs) and silver nanoparticles (AgNPs) through assembling an energy transfer-based quenching system, featuring the pH-promoted distinct PL "switch-on" response. Under neutral conditions, only Cys and Hcy can encapsulate AgNPs, leaving little chance for N,S-CD binding on the surface of AgNPs, which can lead to PL signal recovery, and the total quantity of Cys and Hcy can be determined. However, at pH 3.0 all three kinds of biothiols can lead to the PL signal recovery and the total quantity of GSH, Cys, and Hcy can be determined, due to the similar slopes and intercepts of their calibration curves. Thus, the concentration of GSH could be further calculated and the strategy was successfully applied for the detection of GSH in human serum, demonstrating its potential in bioanalysis and significance in addressing biological and medicinal requirements.

A photoluminescence "switch-on" nanosensor composed of nitrogen and sulphur co-doped carbon dots and gold nanoparticles for discriminative detection of glutathione.

Biological thiols play a key role in biological processes and are involved in a variety of diseases. The discriminative detection of biological thiols is still challenging. In this contribution, a platform, an energy transfer-based quenching system composed of nitrogen and sulphur co-doped carbon dots (N, S-CDs) and gold nanoparticles (AuNPs), was established to discriminate glutathione (GSH) from other competitive biothiols including cysteine (Cys) and homocysteine (Hcy) based on a photoluminescence (PL) "switch-on" signal readout. The presence of GSH can encapsulate AuNPs in priority because of the strong affinity towards AuNPs and the steric hindrance effect of GSH, leaving little chance for the N, S-CDs binding on the surface of AuNPs and thus resulting in the PL recovery of N, S-CDs. Compared with the nitrogen-doped carbon dots (N-CDs), the N, S-CDs can enhance 10 times sensitivity for the designed PL "switch-on" sensing strategy. The proposed method has a detection limit of 3.6 nM and can be successfully applied for the detection of GSH in human serum.

Optically Active Ultrafine Au-Ag Alloy Nanoparticles Used for Colorimetric Chiral Recognition and Circular Dichroism Sensing of Enantiomers.

Despite a significant surge in the number of investigations into chirality at the nanoscale, especially thiolated chiral molecules capping gold clusters, only limited knowledge is currently available to elaborate the alloying effect on chiroptical behavior of bimetallic nanoparticles (NPs). Also, few successful cases as to the efforts toward the development of chirality-dependent applications on the optically active nanomaterial have been made. Herein, as a positive test case for chiral alloy nanoparticle synthesis, the stable and large chiroptical ultrafine Au-Ag alloy NPs were prepared by reduction of different molar fractions of HAuCl4 and AgNO3 with NaBH4 in the presence of d/l-penicillamine (d/l-Pen). Compared with those of monometallic Au and Ag counterparts with comparable size, the Au-Ag alloy NPs (Ag mole fraction, 70%) obviously displayed the largest optical activities with the maximum g-factors of ∼1.6 × 10-3. Impressively, the Pen-mediated synthesis of chiral Au-Ag alloy NPs possesses a colorimetric self-recognition function and can be used as an incisive circular dichroism (CD) probe toward d- and l-Pen enantiomers. The plasmonic CD signal amplification (ΔICD) shows good linearity with the amount of Pen over the range of 5.0-80.0 µM with a detection limit (3σ) of 1.7 µM for l-Pen and 1.5 µM for d-Pen, respectively. In addition, the sensing system exhibits good selectivity toward d- and l-Pen in the presence of other enantiomers; therefore, it is highly expected that the approach described here would open new opportunities for design of more novel enantioselective analyses of important species related to biological processes.

Porphyrin-loaded liposomes and graphene oxide used for the membrane pore-forming protein assay and inhibitor screening.

The interaction of planar aromatic molecules with the graphene oxide (GO) sheets is often marked by the fluorescence quenching of the former. Here, the α,ß,γ,δ-tetrakis[4-(trimethylammoniumyl)phenyl]porphyrin (TAPP) molecules and the GO, corresponding to the energy donor and the acceptor respectively, are initially separated by encapsulating the TAPP molecules within the liposomes, to obstruct the formation of the self-assembled energy transfer-based quenching system. Upon disruption of the liposome membranes by the PLA2 or the α-toxin, the encapsulated TAPP molecules are released and subsequently result in significant fluorescence changes. Thus, a platform based on the fluorescence signal for monitoring the activity of the membrane pore-forming protein with advantages of high sensitivity and commonality was established. Using this strategy, we can detect the PLA2 and the α-toxin concentrations as low as 200 pM and 9.0 nM, respectively. Furthermore, by taking chlorpromazine and baicalin as the examples, we use the assay to evaluate the prohibition effects on the PLA2 and the α-toxin, and the IC50 values of chlorpromazine toward the PLA2 (9.6 nM) and that of baicalin toward the α-toxin (289.2 nM) were found to be 12.0 ± 0.62 µM and 26.9 ± 2.6 µM, respectively.

New colorimetric and fluorometric sensing strategy based on the anisotropic growth of histidine-mediated synthesis of gold nanoclusters for iodide-specific detection.

Iodide, as a biologically important anion, it remains a worthwhile yet challenging undertaking to find a sensitive and specific approach to provide a technically simple iodide detection. In this article, it was found that no other ions than iodide-induced anisotropic growth of gold nanocrystals (AuNCs) originated from a small molecule, histidine-mediated synthesis of AuNCs, were observed. Simultaneously, it is accompanied by the fluorescence quenching of AuNCs and the naked-eye visible color change. Therefore, a new colorimetric and fluorometric sensing strategy was developed for the iodide-specific detection. Compared with currently reported methods, the present one displays the advantages of the visual detection and simplicity. The quenched fluorescence and enhanced surface plasmon resonance absorbance were found to be proportional to the iodide concentration over the range of 0.8-60 and 1.2-50 µM with a detection limit (3σ) of 118 nM and 215 nM, respectively.

A portable test strip fabricated of luminescent lanthanide-functionalized metal-organic frameworks for rapid and visual detection of tetracycline antibiotics.

Tetracycline antibiotics (TCs) are commonly used antibiotics in the treatment of infections, but their overuse has a negative impact on human health and ecosystems. Thus, the development of a facile and on-site visualization method for TC detection is necessary. Here, we propose the potential of using lanthanide-functionalized metal-organic framework (MOF) composites (Ag+/Tb3+@UiO-66-(COOH)2, ATUC) as a probe for the rapid detection of tetracycline (TC), chlortetracycline (CTC), oxytetracycline (OTC), and doxycycline (DOX) residues, in which UiO-66-(COOH)2 (UC) could be utilized to provide an interaction microenvironment, Tb3+ as recognition units and Ag+ as a fluorescence enhancer. Upon exposure to TCs, significant luminescence quenching of ATUC excited at 255 nm was observed due to the inner filter effect (IFE) and photo-induced electron transfer (PET), and the established strategy has a detection limit (LOD) of 11.0, 20.1, 9.1, and 22.5 nM for TC, CTC, OTC, and DOX, respectively. More importantly, given its portability and conspicuous luminescence color gradation variation, a portable test strip based on ATUC was manufactured and the results could be distinguished immediately by the naked eye and smartphone analysis, allowing for on-site rapid quantitative assay of TCs, not only in the laboratory but also in a point-of-care setting.

Facile synthesis of highly luminescent rod-like terbium-based metal-organic frameworks for sensitive detection of olaquindox.

Olaquindox (OLA), a chemically synthesized antibacterial growth promoter, despite being strictly controlled, is illegally used in feed to improve feed conversion efficiency and increase the rate of weight gain for animals. However, it has become clear that OLA has toxic effects on human beings via the transmission of OLA through the food chain. Here, by employing terbium nitrate to provide metal ions and benzene-1,3,5-tricarboxylic acid (H3BTC) as an organic ligand, a simple, rapid, and easy scale-up synthetic method was presented for the fabrication of water-stable and highly luminescent rod-like metal-organic frameworks (Tb-BTC MOFs). Using the Tb-BTC MOFs as a luminescent probe, the luminescence quenching effect was obviously observed upon the addition of OLA, ascribed to the binding of OLA molecules on the surface of Tb-BTC and the existence of an inner-filter effect (IFE) mechanism. The correlation between the luminescence quenching ΔI and the concentration of OLA was found to be linear from 1.0 to 1000.0 µM with a detection limit of 20.6 nM. Furthermore, a Tb-BTC-loaded fiber paper was prepared and it is highly responsive (30 s) and suitable for visual OLA assay. The method described here can be successfully applied to the detection of OLA in animal feed and edible animal tissue samples.

A cost-effective and rapid quantitative test of polymyxin B sulphate with a simple and portable pressure meter readout.

Any signals, if their intensities have a simple functional relationship with analyte concentration, can be applied for analytical purposes. Among them, pressure measurement as a signalling technique has been extensively utilized to develop portable and quantitative bioanalysis, with the advantages of highly sensitive detection of a variety of biomedical targets. In this contribution, it was found that polymyxin B sulphate (PMB) could significantly inhibit the catalytic ability of platinum nanoparticles (PtNPs) prepared in different protocols in the H2O2 breakdown reaction. By employing sodium citrate as the reducing agent to prepare the platinum nanoparticles (C-PtNPs) as an example and monitoring the pressure signal changes of the C-PtNP catalyzed H2O2 breakdown against the reaction time, a sensitive, cost-effective, rapid and reliable analysis method for PMB is established on the basis of the pressure signal readout. The proposed method has a detection limit of 28.6 nM and can selectively detect PMB in both POLY-MxB powder injection and human urine samples, demonstrating its potential in bioanalysis, which would be significant to address biological, clinical and medicinal requirements.

Probing the Microenvironments in a Polymer-Wrapped Core-Shell Nanoassembly Using Pyrene Chromophores.

The local environments within an amphiphilic polymer shell wrapped around lanthanide-doped upconverting nanoparticles were probed using steady-state and time-resolved fluorescence spectroscopy techniques. Emission lifetime measurements of pyrene chromophores trapped within the polymer shell reveal that there are at least two environments, where the organic pyrene molecules are encapsulated in hydrophobic environments that have lower polarity than in water. The migration of pyrene chromophores from their initial location to another location was also observed, demonstrating that the polymeric shell provides both hydrophobicity and mobility for entrapped molecules. These results offer insight into what outcomes can be expected when chemical reactions are carried out in these nanoassemblies, especially if they are to be used as nanoreactors for synthesis or delivery vehicles for therapeutics.

Optically active red-emitting Cu nanoclusters originating from complexation and redox reaction between copper(ii) and d/l-penicillamine.

Despite a significant surge in the number of investigations into both optically active Au and Ag nanostructures, there is currently only limited knowledge about optically active Cu nanoclusters (CuNCs) and their potential applications. Here, we have succeeded in preparing a pair of optically active red-emitting CuNCs on the basis of complexation and redox reaction between copper(ii) and penicillamine (Pen) enantiomers, in which Pen serves as both a reducing agent and a stabilizing ligand. Significantly, the CuNCs feature unique aggregation induced emission (AIE) characteristics and therefore can serve as pH stimuli-responsive functional materials. Impressively, the ligand chirality plays a dramatic role for the creation of brightly emissive CuNCs, attributed to the conformation of racemic Pen being unfavorable for the electrostatic interaction, and thus suppressing the formation of cluster aggregates. In addition, the clusters display potential toward cytoplasmic staining and labelling due to the high photoluminescence (PL) quantum yields (QYs) and remarkable cellular uptake, in spite that no chirality-dependent effects in autophagy and subcellular localization are observed in the application of chiral cluster enantiomer-based cell imaging.

[Morphological and molecular biological peculiarities of the experimental autoimmune prostatitis rat model].

OBJECTIVE: To observe the morphological and molecular biological peculiarities of the experimental autoimmune prostatitis (EAP) rat model made by SC purified prostate protein twice with immune adjuvant. METHODS: Male rats were intradermally immunized with a saline extract of male rat prostate glands (RPG) in Freund's complete adjuvant (FCA) and Pertussis-Diphtheria-Tetanus vaccine 0.5 ml i.p. at the 0 and 30th day, and the concentrations of the extract were respectively 5 mg/ml, 10 mg/ml and 15 mg/ml. At the 45th day, the rats were sacrificed and the morphological and molecular biological changes of the prostate specimens were observed to determine the effective concentration of RPG for a successful model. RESULTS: The expression of inflammation genes such as TNF-alpha, IL-1beta, IL-2 and iNOS obviously increased in the high-dosage model group; LM, EM and in situ hybridization revealed appearant chronic inflammation response, but this was not the case in the other two dosage groups. CONCLUSION: 15 mg/ml RPG mixed with FCA (1:1) 1.0 ml SC with Pertussis-Diphtheria-Tetanus vaccine 0.5 ml i.p. was an effective dosage for the successful model in our experiment.

Allelopathic effects of Ailanthus altissima extracts on Microcystis aeruginosa growth, physiological changes and microcystins release.

The use of allelochemicals has been proved an environmentally friendly and promising method to control harmful algal blooms. This study was conducted to explore the application potential of Ailanthus altissima (A. altissima) extracts in Microcystis aeruginosa (M. aeruginosa) control for the first time. Four treatments with A. altissima extractions (25mgL(-1), 50mgL(-1), 100mgL(-1), and 200mgL(-1) respectively) and a control group were built to investigate the effects of A. altissima on the growth, cellular microstructure and cell viability, physiological changes, and release of extracellular matters. Results showed that the cell density of M. aeruginosa was effectively inhibited by A. altissima extract, and the inhibition rates were dose-dependent within 5d. Especially for the treatment with 200mgL(-1) of extract, the inhibitory rates remains above 90% after 5d exposure. In addition, A. altissima effectively decreased the amount of extracellular cyanotoxin microcystins and destroyed the photosynthesis-related structure of algae cell during the experimental period. The results demonstrated the A. altissima extracts can be used as an effective and safe algicide to control algal blooms. However, it must be noted that specific compounds responsible for algicidal effect should be isolated and identified to explore inhibition mechanism of A. altissima in future study.

Does phenoloxidase contributed to the resistance? Selection with butane-fipronil enhanced its activities from diamondback moths.

Using microtitration method, the relationship between Phenoloxidase activity and the resistance of the diamondback moth Plutella xylostella (Linnaeus) to the novel insecticide butane-fipronil was determined in vitro. After selection of the tenth-generation by butane-fipronil, the resistance of the fourth instar larvae was increased 83.80-fold as compared to the susceptible strain. Phenoloxidase activity of the resistant strain (PO(r)) was 1.29-fold higher than the susceptible one (PO(s)). However, the Km and optimum pH values were similar in resistant and susceptible strains, which were 1.11 mM and 6.5, respectively. Both PO(r) and PO(s) have maximum stability at pH values less than 7.0, although PO(s) was less stable at lower pH values than PO(r). In addition, the thermal stabilities of the two phenoloxidase were very similar. It is suggested that PO may play an important role in the increasing resistance of pests to pesticides.

Increased inflammatory factors activity in model rats with experimental autoimmune prostatitis.

Male rats were immunized with prostate tissue homogenate supernate (PTHS) of male rats with complete Freund's adjuvant (CFA) intra dermal in the multiple points and simultaneously immunized with 0.5 ml Pertussis-Diphtheria-Tetanus (PDT) vaccine intra peritonea on 0 and 30th day. At the 45th day after first immunization, animals were sacrificed and a series of examinations such as HE stain, assay of TNF-alpha by ELISA and assay of inducible nitric oxide synthase (iNOS) mRNA by in-situ hybridization (ISH) were taken. We observed that there was a remarkable up-regulation of TNF-alpha expression in the high dosage model group. The results of macropathology, histopathology and iNOS ISH also revealed the same tendency. This experimental procedure is effective to induce chronic abacterial prostatitis (CAP).