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The use of microorganisms or toxins as weapons of death and fear is not a novel concept; however, the modes by which these agents of bioterrorism are deployed are increasingly clever and insidious. One mechanism by which biothreats are readily disseminated is through a nation's food supply. Ricin, a toxin derived from the castor bean plant, displays a strong thermostability and remains active at acidic and alkaline pHs. Therefore, the CDC has assigned ricin as a category B reagent since it may be easily amendable as a deliberate food biocontaminate. Current tools for ricin detection utilize enzymatic activity, immunointeractions and presence of castor bean DNA. Many of these tools are confounded by complex food matrices, display a limited dynamic range of detection and/or lack specificity. Aptamers, short RNA and single stranded DNA sequences, have increased affinity to their selected receptors, experience little cross-reactivity to other homologous compounds and are currently being sought after as biosensors for bacterial contaminants in food. This paper describes the selection and characterization of a single, dominant aptamer, designated as SSRA1, against the B-chain of ricin. SSRA1 displays one folding conformation that is stable across 4–63 °C (ΔG= −5.05). SSRA1 is able to concentrate at least 30 ng mL−1of ricin B chain from several liquid food matrices and outcompetes a currently available ELISA kit and ricin aptamer. Furthermore, we show detection of 25 ng mL−1of intact ricin A–B complex using SSRA1 combined with surface enhanced Raman scattering technique. Thus, SSRA1 would serve well as pre-analytical tool for processing of ricin from liquid foods to aid current diagnostics as well as a sensor for direct ricin detection. [ABSTRACT FROM AUTHOR]

Monitoring the levels of pesticides on plant tissues is important for achieving effective protection of crops after application, as well as ensuring low levels of residues during harvest. In this study, a simple, rapid, and fieldable colorimetric method for detecting the pesticide glyphosate (Gly) on the plant tissues in situ using cysteamine-modified gold nanoparticles (AuNPs-Cys) has been developed. The aggregation of AuNPs-Cys in the presence of Gly results in a consequent color change from red to blue (or purple), which could be observed visually on the surface of plant tissues. With the naked eye, we successfully detected Gly spiked on the surface of spinach, apple, and corn leaves in situ. Further verification and quantification were achieved using surface-enhanced Raman spectroscopy (SERS) which uses AuNPs-Cys as the substrate. Moreover, application of this method was demonstrated through the evaluation of the Gly distribution on plant tissues which could greatly facilitate the development of precision agriculture technology. [ABSTRACT FROM AUTHOR]

Herein, a facile solvent mediated silver nanoparticle (AgNP) mirror was introduced as a reproducible and sensitive surface-enhanced Raman scattering (SERS) substrate. The AgNP mirror was fabricated based on commercially available citrate coated AgNPs via a facile and unique water–solvent interface assembly method without using any electrical equipment. By adding 0.2 mg ml−1 citrate coated AgNPs dropwise into a mediating solvent, self-assembled AgNP mirrors were formed instantly and gradually settled down at the bottom. The mediating solvent is the key for this fabrication, which should contain a mixture of a non-polar (e.g. hexane, cyclohexane, and iso-octane) and a polar (e.g., acetonitrile, acetone, methanol, and ethanol) organic solvents that have a lower density than water. The fabricated AgNP mirror showed a uniform monolayer arrangement which produced highly reproducible and sensitive signals. The coefficient of variance (i.e., percentage relative standard deviation) for AgNP mirrors was 7.3% compared to 33.0% for AgNP aggregates. A lower limit of detection (0.008 ppm) and a higher coefficient of determination (0.9981) for the detection of the fonofos pesticide were also obtained from the AgNP mirror compared to that from the AgNP aggregates. The practical application of this nanoscale AgNP mirror sensing substrate was also confirmed by its accurate quantification of 0.5 ppm fonofos in apple juice and green tea (i.e., 105.06% and 106.16% recovery value, respectively). [ABSTRACT FROM AUTHOR]

The table of contents for the September 2016 issue of the journal "Analyst" is presented.

An innovative and ultra-sensitive surface-enhanced Raman spectroscopic (SERS) method that uses a triple-functional surfactant ligand for nanoparticle surface binding, phase transfer and SERS signal reporting was developed for silver nanoparticle (AgNP) detection. The method was able to detect 100 ng L−1 of AgNPs in aqueous samples and 2 μg g−1 AgNPs in wheat plants. [ABSTRACT FROM AUTHOR]

An introduction is presented which discusses various topics within the issue including application of electrochemical hydrogen sulfide biosensors, uses of easy ambient sonic-spray ionization mass spectrometry, and imaging of hydrogen sulfide (H2S) at sub cellular resolution.

Here we presented a simple, rapid and label-free surface-enhanced Raman spectroscopy (SERS) based mapping method for the detection and discrimination of Salmonella enterica and Escherichia coli on silver dendrites. The sample preparation was first optimized to maximize sensitivity. The mapping method was then used to scan through the bacterial cells adsorbed on the surface of silver dendrites. The intrinsic and distinct SERS signals of bacterial cells were used as the basis for label-free detection and discrimination. The results show the developed method is able to detect single bacterial cells adsorbed on the silver dendrites with a limit of detection as low as 104 CFU mL−1, which is two orders of magnitude lower than the traditional SERS method under the same experimental condition. The time needed for collecting a 225 points map was approximately 24 minutes. Moreover, the developed SERS mapping method can realize simultaneous detection and identification of Salmonella enterica subsp. enterica BAA1045 and Escherichia coli BL21 from a mixture sample using principle component analysis. Our results demonstrate the great potential of the label-free SERS mapping method to detect, identify and quantify bacteria and bacterial mixtures simultaneously. [ABSTRACT FROM AUTHOR]

The table of contents for the October 15, 2014 issue of the journal is presented.

Herein, we fabricated amphiphilic gold nanoparticles (GNPs) that can self-assemble at oil–water interfaces. We applied those GNPs for in situ SERS detection of emulsifier molecules within the interfacial region of oil in water (O/W) emulsion systems. [ABSTRACT FROM AUTHOR]

A table of contents for the July 1, 2014 issue of the periodical "Analyst," is presented.

A simple fabrication method for preparing lipophilic gold nanoparticles (AuNPs) suitable for use as substrates in surface-enhanced Raman scattering (SERS) applications of lipids was developed. The AuNPs were shown to be dispersible within lipid phases, where they greatly increased the SERS signals of lipids. [ABSTRACT FROM AUTHOR]

The objective of this study was to develop a simple and rapid method that could detect and discriminate four specific pesticides (isocarbophos, omethoate, phorate, and profenofos) using a single aptamer-based capture procedure followed by Surface Enhanced Raman Spectroscopy (SERS). The aptamer is a single stranded DNA sequence that is specific to capture these four pesticides. The thiolated aptamer was conjugated onto silver (Ag) dendrites, a nanostructure that can enhance the Raman fingerprint of pesticides, through Ag–thiol bonds. It was then backfilled with 6-mercaptohexanol (MH) to prevent nonspecific binding. The modified SERS platform [Ag–(Ap + MH)] was then mixed with each pesticide solution (P) for 20 min. After capturing the pesticides, the Ag–(Ap + MH)–P complex was analyzed under a DXR Raman microscope and TQ Analyst software. The results show that the four pesticides can be captured and detected using principal component analysis based on their distinct fingerprint Raman peaks. The limits of detection (LODs) of isocarbophos, omethoate, phorate, and profenofos were 3.4 μM (1 ppm), 24 μM (5 ppm), 0.4 μM (0.1 ppm), and 14 μM (5 ppm) respectively. This method was also validated successfully in apple juice. These results demonstrated the super capacity of aptamer-based SERS in rapid detection and discrimination of multi-pesticides. This technique can be extended to detect a wide range of pesticides using specific aptamers. [ABSTRACT FROM AUTHOR]

A table of contents for the April 15, 2014 issue of the periodical "Analyst," is presented.

A miniaturized flow-through system consisting of a gold coated silicon substrate based on enhanced Raman spectroscopy has been used to study the detection of vapour from model explosive compounds. The measurements show that the detectability of the vapour molecules at room temperature depends sensitively on the interaction between the molecule and the substrate. The results highlight the capability of a flow system combined with Raman spectroscopy for detecting low vapour pressure compounds with a limit of detection of 0.2 ppb as demonstrated by the detection of bis(2-ethylhexyl)phthalate, a common polymer additive emitted from a commercial polyvinyl chloride (PVC) tubing at room temperature. [ABSTRACT FROM AUTHOR]

A table of contents for the issue is presented.

The feasibility of utilizing a handheld Raman spectrometer for surface-enhanced Raman scattering detection was evaluated on the pesticide ferbam. A layman's “answer box” was established for semi-quantifying the risk level of ferbam. This study advanced the application of a handheld Raman spectrometer to on-site evaluation of trace amounts of analytes. [ABSTRACT FROM AUTHOR]

A table of contents for the March 2013 issue of the journal "Analyst" is presented.

Herein, we developed an innovative label free platform for concentration, detection and discrimination of Bacillus anthracis spores. Based on aptamer capture and surface enhanced Raman scattering detection, we were able to detect 104 CFU spores spiked in orange juice and discriminate between spores B. anthracis and B. mycoides within 40 min. [ABSTRACT FROM AUTHOR]