Array-based microbial identification upon extracellular aminoglycoside residue sensing.

Sensitive and rapid identification of pathogenic microorganisms is of great importance for clinical diagnosis and treatment. In this study, we developed an ultrasensitive colorimetric sensor array (CSA) based on the interactions between aminoglycoside antibiotics (AMGs) and Ag nanoparticles decorated with ß-cyclodextrin (AgNPs@ß-CD) to discriminate microorganisms quickly and accurately. Microorganisms can absorb different amounts of AMGs after incubation. Upon the addition of AgNPs@ß-CD, the corresponding extracellular AMG residues will bind to AgNPs@ß-CD, leading to color changes due to the modifications in localized surface plasmon resonance. The array was developed using 4 AMGs as sensing elements and AgNPs@ß-CD as the colorimetric probe to generate a unique colorimetric response pattern for each microorganism. Standard chemometric methods indicated excellent discrimination among 20 microorganisms at low concentrations of 2 × 106 CFU/mL. Therefore, this ultrasensitive CSA can be used for microbial discrimination portably and efficiently. Importantly, the concentration of microbial discrimination by our array is much lower than that of prior CSAs. This method of extracellular residue sensing also provided a new strategy to improve the sensitivity of conventional CSA in the discrimination of microorganisms, to measure the amount of intercellular uptake of AMGs by microorganisms, and to screen drugs that can easily be accumulated by the pathogenic microorganisms.

Colorimetric Sensor Array Based on Wulff-Type Boronate Functionalized AgNPs at Various pH for Bacteria Identification.

The efficient identification of bacteria is of considerable significance in clinical diagnosis. Herein, a novel colorimetric sensor array was developed for the detection and identification of bacteria based on the specific affinity and electrostatic interaction between Wulff-type 4-mercaptophenylboronic acid (MPBA)-mercaptoethylamine (MA) cofunctionalized AgNPs (MPBA-MA@AgNPs) and bacteria at various pH. In the neutral and alkaline conditions, AgNPs tended to be dispersed due to the specific affinity between cis-diol residues contained in carbohydrate-rich compositions on the bacterial cell surface and MPBA. Bacterial cells have different carbohydrate compositions on their surface. The differential binding affinity of MPBA on the surface of AgNPs to cis-diol residues of various carbohydrates resulted in a different color change of AgNPs, which could be tuned by pH. On the contrary, AgNPs tended to be aggregated due to the electrostatic interaction between positively charged MA and negatively charged bacteria under acidic conditions. Therefore, using various pH buffer solutions as the sensing elements and MPBA-MA@AgNPs as the indicator, bacteria could be differentiated from each other by their own color response patterns. Moreover, the complex bacteria mixtures could be well discriminated. The method is simple, efficient, and visual and has a potential application in pathogen diagnosis.

A pH-based sensor array for the detection and identification of proteins using CdSe/ZnS quantum dots as an indicator.

Protein identification is very important in the field of clinical medicine and diagnosis. Here, we report a novel and simple sensor array for the detection and identification of proteins using pH buffer solutions as sensing elements. Different proteins in various pH solutions have different net surface charges including positive, negative or no charge. Such differences may allow a pattern recognition-based sensor array for protein identification. When using negatively charged CdSe/ZnS quantum dots as an indicator, the interactions between a charged protein and quantum dots result in fluorescence changes, generating a differential response pattern for the protein. The result shows that proteins with pI > 7, pI = 7 or pI < 7 can be differentiated successfully. Moreover, complex protein mixtures are also able to be identified and the results demonstrate that surface charge may play an important role in protein sensing. The HSA of different concentrations in water and human urine can also be detected by using the sensor array. It is demonstrated that the proposed sensor array has potential applications in clinical diagnosis and proteomics.

Colorimetric Sensor Array Based on Gold Nanoparticles with Diverse Surface Charges for Microorganisms Identification.

We report a simple and novel colorimetric sensor array for rapid identification of microorganisms. In this study, four gold nanoparticles (AuNPs) with diverse surface charges were used as sensing elements. The interactions between AuNPs and microorganisms led to obvious color shifts, which could be observed by the naked eye. A total of 15 microorganisms had their own response patterns and were differentiated by linear discriminant analysis (LDA) successfully. Moreover, microorganism mixtures could also be well discerned. The method is simple, fast (within 5 s), effective, and visual, showing the potential applications in pathogen diagnosis and environmental monitoring.

Colorimetric sensor array with unmodified noble metal nanoparticles for naked-eye detection of proteins and bacteria.

Herein we report a novel strategy for the detection and identification of proteins using unmodified noble metal nanoparticles. Five gold nanoparticles (AuNPs) and two silver nanoparticles (AgNPs) with different sizes were utilized as sensing elements to create a colorimetric sensor array. In the presence of proteins, the UV-vis absorbance of the noble metal nanoparticles changed due to the interactions between the protein and nanoparticles, producing distinct absorbance response patterns which can be visually detected by the naked eye. The color pattern of the array is a unique "fingerprints" for each protein sample, which can be differentiated by linear discriminant analysis (LDA). Ten different proteins at concentrations of 0.5, 5 and 50 µM have be successfully discriminated. Moreover, the array was also able to discriminate different bacteria at a concentration of 0.05 OD in 200 µL, as well as cancer cells at the level of 5000 cells in 200 µL. This work demonstrates that an unmodified noble metal nanoparticle-based protein detection array has potential for applications in medical diagnostics.

Colorimetric Sensor Array for Identification of Proteins and Classification of Metabolic Profiles under Various Osmolyte Conditions.

Rapid and efficient detection and identification of proteins hold great promise in medical diagnostics, treatment of different diseases, and proteomics. Here, we present a simple colorimetric sensor array for the differentiation of proteins in various osmolyte solutions. Osmolytes have different influences on the conformation of proteins, which have differential binding to silver nanoparticles, resulting in color changes. The sensor array shows unique color change patterns for each of the 19 proteins, allowing unambiguous identification. Very interestingly, the differentiation of 19 proteins is related to their molecular weight. Moreover, the sensor array can be used to identify protein mixtures, thermal denaturized proteins, and unknown protein samples. Finally, the sensor array can also analyze the plasma or liver samples of the four groups of salt-sensitive rats fed with different diets, indicating that it has the potential for the classification of metabolic profiles.

Amplified fluorescence detection of mercury(II) ions (Hg2+) using target-induced DNAzyme cascade with catalytic and molecular beacons.

In this work, a fluorescent sensing strategy was developed for the detection of mercury(II) ions (Hg(2+)) in aqueous solution with excellent sensitivity and selectivity using a target-induced DNAzyme cascade with catalytic and molecular beacons (CAMB). In order to construct the biosensor, a Mg(2+)-dependent DNAzyme was elaborately designed and artificially split into two separate oligonucleotide fragments. In the presence of Hg(2+), the specific thymine-Hg(2+)-thymine (T-Hg(2+)-T) interaction induced the two fragments to produce the activated Mg(2+)-dependent DNAzyme, which would hybridize with a hairpin-structured MB substrate to form the CAMB system. Eventually, each target-induced activated DNAzyme could catalyze the cleavage of many MB substrates through true enzymatic multiple turnovers. This would significantly enhance the sensitivity of the Hg(2+) sensing system and push the detection limit down to 0.2 nM within a 20 min assay time, much lower than those of most previously reported fluorescence assays. Owning to the strong coordination of Hg(2+) to the T-T mismatched pairs, this proposed sensing system exhibited excellent selectivity for Hg(2+) detection, even in the presence of 100 times of other interferential metal ions. Furthermore, the applicability of the biosensor for Hg(2+) detection in river water samples was demonstrated with satisfactory results. These advantages endow the sensing strategy with a great potential for the simple, rapid, sensitive, and specific detection of Hg(2+) from a wide range of real samples.

Influence of dissolved organic matter and heavy metals on the utilization of soil-like material mined from different types of MSW landfills.

Soil-like material (SLM) mined from municipal solid waste (MSW) landfills can be used as nursery cultivation soil, landfill cover, and as a building material. However, SLM utilization is restrained by heavy metal (HM) contents whose speciation and migration are influenced by their dissolved organic matter (DOM) content. Therefore, the properties of aged refuse and the correlation between DOM and HM forms were studied using samples from different types of MSW landfills. The dominant components of aged refuse were SLM (18.80%-83.51%) and plastics (11.17%-65.51%). The moisture, organic matter, and pH ranged from 29.55% to 57.92%, 15.70%-57.68%, and 7.84-8.51, respectively. The Zn content was highest (455.48-1379.27 mg/kg) in the SLM, followed by Cu (96.29-428.90 mg/kg), Cr (49.10-236.21 mg/kg), Pb (53.52-222.71 mg/kg), and Ni (20.92-39.10 mg/kg). The SLM cannot be used for agriculture because the HM contamination exceeds the multiple of 0.07-7.99. Zinc in the acid-soluble state and reducible state had the highest mobility in SLM. However, Cu and Pb, mainly in the oxidizable state, and Cr and Ni, in the oxidizable and residual states, were relatively stable. In the sanitary and simple MSW landfills, the average proportion of protein-like materials decreased from 84.44% to 82.61% and from 65.58% to 55.94%, respectively, as the landfill depth increased. Both the acid-soluble and oxidizable HM states and all forms of Zn in the SLM were significantly positively correlated with tyrosine-like materials (r = 0.58*-0.87**). Protein-like materials may enhance the mobility of HMs.

Analysis of 2-propanol in exhaled breath using in situ enrichment and cataluminescence detection.

We report a simple gaseous sensor for the sensitive detection of trace 2-propanol in exhaled breath using in situ enrichment and cataluminescence detection method on the surface of nanomaterials. The influences of heating voltage and absorption time on the CTL intensity were discussed, respectively. In the selected conditions, the linear range of 2-propanol concentration is 60-600 ppbv and the detection of limit is 11 ppbv. Moreover, the lifetime and selectivity of the sensor were also investigated. It has the potential to diagnostic volatile organic compounds in human breath.

Development of pH-responsive nanocomposites with remarkably synergistic antibiofilm activities based on ultrasmall silver nanoparticles in combination with aminoglycoside antibiotics.

Bacterial biofilms are responsible for many chronic infections because antibacterial agents exhibit poor penetration into the dense matrix barrier and cannot easily reach the internal bacteria. Herein, we reported pH-responsive nanocomposites (PDA@Kana-AgNPs) that could penetrate and disperse biofilms, which were synthesized by the combination of ultrasmall silver nanoparticles (AgNPs) and kanamycin, and then coating with polydopamine. Confocal fluorescence imaging indicated that PDA@Kana-AgNPs could respond to the acidic microenvironment of biofilms, leading to biofilm-triggered on- demand drug release in situ. The zone of inhibition test and Resazurin assay showed that the combination of kanamycin and AgNPs had greater antimicrobial activity against test strains (Staphylococcus aureus, Streptococcus pneumoniae, Pseudomonas aeruginosa, and Escherichia coli BL21) than when applied separately. The crystal violet staining test demonstrated that biofilms were effectively dispersed by the proposed nanocomposites. Biocompatibility was also evaluated, which showed that PDA@Kana-AgNPs were non-toxic to mammalian cells. Therefore, the proposed pH-responsive nanocomposites held great potential for efficient antibiotics delivery and showed synergistic antibacterial and antibiofilm activities. This strategy could also be used to encapsulate a variety of antibiotics in combination with other drugs or materials, thereby showing therapeutic potential in preventing biofilm-related infections and realizing fluorescence imaging in situ.

Dual-channel sensing of volatile organic compounds with semiconducting nanoparticles.

Extracting multidimensional information from an individual transducer simultaneously is a promising alternative sensing strategy to traditional sensors. Here, we proposed a novel dual channel sensing method with simultaneously recording conductivity change of sensing material and chemiluminescence emission during catalytic oxidation of volatile organic compounds on tin oxide nanoparticles. The orthogonal and complementary electrical and optical signals have been obtained for each compound, which have been applied to discriminate 20 volatile organic compounds using hierarchical cluster analysis (HCA). Unknown samples from three groups at concentrations of 0.2%, 0.6%, and 1.0% have been successfully classified using linear discriminant analysis (LDA) with accuracies of 98.3%, 96.7%, and 98.3%, respectively. This dual channel sensing mode is a complement of semiconducting type gas sensors and quite promising for the development of chemical sensor arrays with multimode transducing principles.

GMBP1-conjugated manganese oxide nanoplates for in vivo monitoring of gastric cancer MDR using magnetic resonance imaging.

Multidrug resistance (MDR) is a huge challenge for gastric cancer chemotherapy. Therefore, MDR accurate monitoring is of great significance for the treatment of gastric cancer. GMBP1, an extracellular internalization peptide, can target MDR gastric cancer cells through specific binding to GRP78, which is an MDR-related protein that is overexpressed in gastric cancer cells. Herein, we constructed GMBP1 conjugated Mn3O4 nanoplates (Mn3O4@PEG-GMBP1 NPs) for in vivo monitoring of MDR gastric cancer through magnetic resonance imaging (MRI). The generated Mn3O4@PEG-GMBP1 NPs had a size of about 11 nm and exhibited a good colloidal stability in PBS and in 10% FBS medium. Serial in vivo MRI studies in mice demonstrated that the magnetic resonance signal intensity, at the tumor site, reached a peak at 3 h after tail vein injection of Mn3O4@PEG-GMBP1 NPs. The specific targeting ability of MDR gastric cancer cells (SGC7901/ADR) by Mn3O4@PEG-GMBP1 NPs was authenticated in vitro, in vivo and by immunofluorescence analysis experiments. The systematic safety evaluation indicated that the toxicity of Mn3O4@PEG-GMBP1 NPs in mice was negligible. Therefore, the GMBP1 conjugated Mn3O4 nanoplates can be clinically used for accurate imaging and monitoring of MDR gastric cancer.

Construction of Biocompatible Dual-Drug Loaded Complicated Nanoparticles for in vivo Improvement of Synergistic Chemotherapy in Esophageal Cancer.

Combination chemotherapy is a routine treatment for esophageal cancer, but some shortcomings, such as drug toxicity and side effects, greatly limit the clinical application of combination therapy. To overcome these shortcomings, we have developed a mesoporous silica nanoparticle system that was used to load doxorubicin and ß-elemene. ß-elemene was encapsulated in the pore of mesoporous silica nanoparticle and doxorubicin was electrostatically adsorbed on the surface of mesoporous silica nanoparticle by hyaluronic acid to construct dual drugs synergistic nanoparticles (bMED NPs, ~77.15 nm). In vitro studies demonstrated that bMED NPs had a good treatment effect in esophageal cancer cell lines. In vivo fluorescence imaging results demonstrated that bMED NPs could accumulate in tumor sites and achieve in vivo long-term circulation and continuous drug release. In addition, bMED NPs exhibited significant antitumor effects in the esophageal cancer mouse model, which may provide a great platform for esophageal cancer chemotherapy.

Discrimination and identification of flavors with catalytic nanomaterial-based optical chemosensor array.

A cross-reactive chemiluminescence (CL) sensor array based on catalytic nanomaterials was constructed for the discrimination and identification of flavors in cigarettes. A total of 21 nanomaterials, including metal oxides, metal oxides deposited on carbon nanotubes (CNTs), gold nanoparticles deposited on metal oxides, and carbonate, have been carefully selected as sensing elements of the array. Each flavor gives its unique CL pattern from the array, which is able to be employed for the discrimination and identification of flavors. Hierarchical cluster analysis (HCA) and linear discriminant analysis (LDA) were used to analyze the patterns. The obtained CL patterns are temperature dependent, thus additional discrimination power could be provided by changing the working temperature of the array. Quantification of the flavors has been performed according to the emission intensity on the specific sensing element. The linear ranges of the sensor array for the flavors are in the range of 20-2000 ppmv with the limits of detection below 10 ppmv, which vary with the kinds of flavors. Six brands of cigarettes have been discriminated by their CL patterns obtained with the present sensor array. The robust and reversible response of this array, combined with its simple instrumentation, indicates the promise of this array for real world application.

Riboflavin-protected ultrasmall silver nanoclusters with enhanced antibacterial activity and the mechanisms.

Developing silver nanomaterials with efficient antimicrobial properties is of importance for combating bacteria. Here, we report ultrasmall riboflavin-protected silver nanoclusters (RF@AgNCs) that can effectively kill or suppress the growth of Gram-positive S. aureus, Gram-negative E. coli, and fungi C. albicans. Riboflavin (RF) with intrinsic biocompatibility was used as a surface ligand to synthesize silver nanoclusters. TEM revealed that the synthesized RF@AgNCs were ultrasmall (2.4 ± 1.2 nm), spherical and well-dispersed. Antibacterial activity tests showed that RF@AgNCs possessed superior antibacterial efficacy in comparison with RF, AgNPs and mixed RF and AgNPs (RF + AgNPs). The mechanisms of antibacterial activity of RF@AgNCs were studied by fluorescence microscopy-based Live/Dead cell staining assays and ROS measurement. And the results illustrated that the integrity of the bacteria membrane was disrupted and intracellular high level ROS generation was induced by RF@AgNCs. The cytotoxic activities were also assessed and RF@AgNCs were found to be non-toxic to human red blood cells and mammalian cells. With the highly efficient antibacterial activity and acceptable biocompatibility, RF@AgNCs hold great promise in biomedical applications as well as in water sterilization and the textile industry.

Development of a benzaldehyde sensor utilizing chemiluminescence on nanosized Y2O3.

A chemiluminescence sensor has been proposed for sensitive determination of benzaldehyde, with nanosized Y(2)O(3) as the sensing material. Under optimized conditions, the linear range of the CL intensity vs. the concentration of benzaldehyde vapour is 1.8 ng/mL-10.8 microg/mL (r(2) = 0.9996), with a detection limit of 0.90 ng/mL (signal:noise ratio = 3:1). The sensor also exhibits high selectivity to benzaldehyde because no or weak CL signals have been detected when foreign substances are introduced into the sensor. In addition, the sensor also shows good stability and longer lifetime within 100 h. The results indicate that the proposed sensor, which has high sensitivity and selectivity, shows great potential for the detection of benzaldehyde.

On-line concentration and determination of all-trans- and 13-cis- retinoic acids in rabbit serum by application of sweeping technique in micellar electrokinetic chromatography.

A simple and rapid micellar electrokinetic chromatography (MEKC) method with UV detection was developed for the simultaneous separation and determination of all-trans- and 13-cis-retinoic acids in rabbit serum by on-line sweeping concentration technique. The serum sample was simply deproteinized and centrifuged. Various parameters affecting sample enrichment and separation were systematically investigated. Under optimal conditions, the analytes could be well separated within 17min, and the relative standard deviations (RSD) of migration times and peak areas were less than 3.4%. Compared with the conventional MEKC injection method, the 18- and 19-fold improvements in sensitivity were achieved, respectively. The proposed method has been successfully applied to the determination of all-trans- and 13-cis-retinoic acids in serum samples from rabbits and could be feasible for the further pharmacokinetics study of all-trans-retinoic acid.

Highly sensitive fluorescence assay of DNA methyltransferase activity via methylation-sensitive cleavage coupled with nicking enzyme-assisted signal amplification.

Herein, using DNA adenine methylation (Dam) methyltransferase (MTase) as a model analyte, a simple, rapid, and highly sensitive fluorescence sensing platform for monitoring the activity and inhibition of DNA MTase was developed on the basis of methylation-sensitive cleavage and nicking enzyme-assisted signal amplification. In the presence of Dam MTase, an elaborately designed hairpin probe was methylated. With the help of methylation-sensitive restriction endonuclease DpnI, the methylated hairpin probe could be cleaved to release a single-stranded DNA (ssDNA). Subsequently, this released ssDNA would hybridize with the molecular beacon (MB) to open its hairpin structure, resulting in the restoration of fluorescence signal as well as formation of the double-stranded recognition site for nicking enzyme Nt.BbvCI. Eventually, an amplified fluorescence signal was observed through the enzymatic recycling cleavage of MBs. Based on this unique strategy, a very low detection limit down to 0.06 U/mL was achieved within a short assay time (60 min) in one step, which is superior to those of most existing approaches. Owing to the specific site recognition of MTase toward its substrate, the proposed sensing system was able to readily discriminate Dam MTase from other MTase such as M.SssI and even detect the target in complex biological matrix. Furthermore, the application of the proposed sensing strategy for screening Dam MTase inhibitors was also demonstrated with satisfactory results. This novel method not only provides a promising platform for monitoring activity and inhibition of DNA MTases, but also shows great potentials in biological process researches, drugs discovery and clinical diagnostics.

Ultrasensitive and selective detection of nicotinamide adenine dinucleotide by target-triggered ligation-rolling circle amplification.

An ultrasensitive fluorescence assay for nicotinamide adenine dinucleotide (NAD(+)) was developed by target-triggered ligation-rolling circle amplification (L-RCA). This novel approach can detect as low as 1 pM NAD(+), much lower than those of previously reported biosensors, and exhibits high discrimination ability even against 200 times excess of NAD(+) analogs.

A rapid capillary electrophoresis with electrochemiluminescence method for the assay of human urinary proline and hydroxyproline.

A novel simultaneous determination method for free and total proline (Pro) and hydroxyproline (Hyp) in human urine was developed, based on capillary electrophoresis (CE) with electrochemiluminescence (ECL) detection, using tris-(2,2'-bipyridyl) ruthenium(II). Experimental conditions, such as the Ru(bpy)(3)2+ concentration, detection potentials, buffer concentration and pH in CE or in the ECL cell, injection voltage and time were investigated in detail. Under optimized conditions, the linear range, detection limit and sample recoveries for the method were 0.01-2 mmol/L (correlation coefficient, 0.9970), 4 micromol/L and 96.4-101.2% in human urine, respectively. The results show that the method has potential applications in monitoring the level of Pro and Hyp in body fluids from patients with bone disease, tumours or chronic uraemia.