Name: color spot test as a presumptive tool for the rapid detection of synthetic cathinones
Uploaded: 2018-02-05T14:45:00
Description: Watch this Scientific Journal Video about Color Spot Test As a Presumptive Tool for the Rapid Detection of Synthetic Cathinones at JoVE.com

The authors would like to acknowledge the support provided to Morgan Philp through an Australian Government Research Training Program Scholarship.

1. Preparation of Color Test Reagent Solutions
NOTE: Weigh 0.12 g of copper nitrate trihydrate into a dry 100 mL beaker. Add 30 mL of deionized (DI) water and carefully swirl it at room temperature to dissolve all solids. Pour this solution into a 100 mL volumetric flask and fill up to the calibrated mark with DI water. This prepared solution is reagent 1. 
NOTE: Reagent 1 can be prepared using other copper(II) salts, e.g. copper(II) chloride.
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	<li>Weigh 0.11 g of 2,9-dime...

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E., Gizzi, M. C., Mulligan, C. 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M., Al-Tamrah, S. A., Aly, F. A., Alwarthan, A. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+(S)(&#8722;)-cathinone+by+spectrophotometric+detection.">Determination of (S)(&#8722;)-cathinone by spectrophotometric detection.</a> J Pharmaceut Biomed. 17 (2), 321-326 (1998).</li><li>Namera, A., Kawamura, M., Nakamoto, A., Saito, T., Nagao, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comprehensive+review+of+the+detection+methods+for+synthetic+cannabinoids+and+cathinones.">Comprehensive review of the detection methods for synthetic cannabinoids and cathinones.</a> Forensic Toxicol. 33 (2), 175-194 (2015).</li><li>Isaacs, R. C. 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This color test protocol was adapted from experimental work published by Al-Obaid et al.18 in which the authors demonstrated a color change occurs in the presence of cathinone extracted from the khat plant. Modifications to the published protocol were necessary to foresee its application in presumptive illicit drug detection. The most important consideration was to reduce the scale of the reaction. The protocol described in the present paper is designed to be applied to street samples and...

The illicit drug market operates similarly to a traditional business by continuing to evolve and adapt to a changing marketplace. Advances in modern technology, specifically, the global proliferation of powerful communication has seen increased online purchases via the Dark Net1 and extensive knowledge sharing among users via online forums2. Combined with advances in chemistry, the rapid emergence of new psychoactive substances (NPS) created a serious challenge for international and national drug control.
NPS are potentially dangerous substances of abuse that have similar effects to drugs under international control. Initially marketed as &#34;legal&#34; alternatives, 739 NPS were reported to the United Nations Office on Drugs and Crime (UNODC) between 2009 and 20163. According to the most recent annual report, a record number of NPS were seized at the Australian border, with the majority of those analyzed, further identified as synthetic cathinones4. On a global scale, seizures of synthetic cathinones have been steadily increasing since first reported in 2010, and are one of the most commonly seized NPS5.
The challenges posed by NPS have been a largely published topic of discussion6,7. Forensic laboratories and law enforcement personnel were left at a disadvantage without appropriate methods in place to detect and identify NPS during their rapid emergence. Extensive research into the detection of NPS, including synthetic cathinones, in seized material, has employed gas chromatography-mass spectrometry (GC-MS)8 and liquid chromatography-high resolution mass spectrometry (LC-HRMS)9 for confirmatory analysis. Increasing demand for minimal sample preparation has seen infrared and Raman spectroscopy10 studies as well as ambient ionisation mass spectrometric analyses, such as direct analysis in real time mass spectrometry (DART-MS)11,12. The need for rapid, sensitive analysis in the field has also seen the incorporation of paper spray ionization-mass spectrometry (PSI-MS) into portable devices for use by law enforcement13. Many instrumental techniques offer confirmatory analysis with sensitive detection and quantitative results. However, for high-throughput analysis, they can be time-consuming due to sample preparation, run times, and instrument training and maintenance.
Presumptive color tests are designed to suggest the presence or absence of certain drug classes in a test sample14. The Scientific Working Group for the Analysis of Seized Drugs (SWGDRUG) classifies color testing as the lowest discriminating power technique, alongside ultraviolet spectroscopy and immunoassays15. However, they are still widely employed by law enforcement and other security personnel as a means to provide rapid results at a significantly lower cost compared to other techniques. The main advantage offered by color spot test methods is the ability to perform them in the field using portable test kits.
The selectivity of color tests relies on individual chemical reactions occurring between the test reagent and the drug class of interest to create a color change. Current presumptive testing protocols lack a particular test for detecting synthetic cathinones only; commonly used reagents that lack specificity and contain hazardous substances are often employed. Other recommended reagents have not been screened on a large number of possible synthetic cathinone substances16.
The aim of this work is to present a simple color test protocol that can be easily employed by interested parties for the preliminary screening of synthetic cathinones in illicit substances of unknown composition. Interested parties would include law enforcement, border protection agencies, forensic laboratories, and other relevant security personnel. The proposed methods employ a reduction-oxidation reaction occurring between the electron-accepting copper complex reagent and the electron rich synthetic cathinone drug molecules. Using these chemical methods developed, one can apply them in the form of a presumptive color test to suggest the presence of synthetic cathinones.

color spot test as a presumptive tool for the rapid detection of synthetic cathinones

Synthetic cathinones are a large class of new psychoactive substances (NPS) that are increasingly prevalent in drug seizures made by law enforcement and other border protection agencies globally. Color testing is a presumptive identification technique indicating the presence or absence of a particular drug class using rapid and uncomplicated chemical methods. Owing to their relatively recent emergence, a color test for the specific identification of synthetic cathinones is not currently available. In this study, we introduce a protocol for the presumptive identification of synthetic cathinones, employing three aqueous reagent solutions: copper(II) nitrate, 2,9-dimethyl-1,10-phenanthroline (neocuproine) and sodium acetate. Small pin-head sized amounts (approximately 0.1-0.2 mg) of the suspected drugs are added to the wells of a porcelain spot plate, and each reagent is then added dropwise sequentially before heating on a hotplate. A color change from very light blue to yellow-orange after 10 min indicates the likely presence of synthetic cathinones. The highly stable and specific test reagent has the potential for use in the presumptive screening of unknown samples for synthetic cathinones in a forensic laboratory. However, the nuisance of an added heating step for the color change result limits the test to laboratory application and decreases the likelihood of an easy translation to field testing.

The test protocol has been validated through several studies, the results of which are described in Philp et al.17. The color test method is able to presumptively detect synthetic cathinones in an unknown sample through a color change from light blue to yellow-orange (Figure 1). Yellow and orange color changes occuring after the heating period are considered positive test results and any other color change, including very weak...

Watch this Scientific Journal Video about Color Spot Test As a Presumptive Tool for the Rapid Detection of Synthetic Cathinones at JoVE.com

Color Spot Test As a Presumptive Tool for the Rapid Detection of Synthetic Cathinones

Here we present a simple, inexpensive, and selective chemical spot test protocol for the detection of synthetic cathinones, a class of new psychoactive substances. The protocol is suitable for use in various areas of law enforcement that encounter illicit material.

Synthetic cathinones are a large class of new psychoactive substances (NPS) that are increasingly prevalent in drug seizures made by law enforcement and ...

The overall goal of this procedure is to presumptively determine the presence or absence of a synthetic cathinone within an unknown seized material using color testory agents and associated color changes. This method can help provide law enforcement agencies with rapid, cost-effective and simple suggestions as to whether or not a synthetic cathinone may be present in a seized material. The main advantage of this technique over other color tests available is its high selectivity to other synthetic cathinone class of elicit drugs.To begin, weigh 0.12 grams of copper nitrate trihydrate into a dry, 100mL beaker. Add 30mL of deionized, or DI water, and carefully swirl it at room temperature to dissolve all solids. Pour this solution into a 100mL volumetric flask.Fill the solution up to the calibrate mark with DI water. This prepared solution is Reagent One. Then, weigh 0.11 grams of necuproine hemihydrate into a dry, 100mL beaker.Add 50mL of 0.1 molar hydrochloric acid and use a glass stirring rod to promote dissolution of solids at room temperature. Pour this solution into a 100mL volumetric flask. Fill up the flask to the calibrated mark with 0.1 molar hydrochloric acid.This prepared solution is Reagent Two. Next, weigh 16.4 grams of sodium acetate into a dry, 100mL beaker. Add 50mL of DI water and use a glass stirring rod to promote dissolution of solids at room temperature.Pour this solution into a 100mL volumetric flask. And fill up to the calibrated mark with DI water. This prepared solution is Reagent Three.Using a spatula, place a small, pinhead-sized amount of the unknown sample into three separate wells of a porcelain spot plate. Leave three adjacent wells empty for the blank control And add equal amounts of 4-MMC HCL to another three wells. These wells serve as a positive control, representing a synthetic cathinone reference sample.Using a disposable pipette, add five drops of the copper nitrate solution to each sample well in addition to the blank and positive control wells. Then, using a second disposable pipette, add two drops of the neocuproine solution to each sample well in addition to the blank and positive control wells. Finally, using a third disposable pipette, add two drops of the sodium acetate solution to each sample well in addition to the blank and positive control wells.At this point, the solution turns light blue. Place the porcelain spot plate directly onto an electric hotplate set at 80 degrees Celsius. After heating for 10 minutes, observe the color change by the naked eye using a white background to better visualize the color changes.Make a note or take a photo of the final color change. Representative results of a blank control and 4-MCC HCL as a synthetic cathinone positive control are shown here. In general, a yellow-orange color change after heating is considered a positive result.However, this color can vary in intensity as seen with N, N-dimethylcathinone HCL which is dark colored as well as with 3 4-dimethylmethcathinone HCL which is light colored. Other positive results include 2 4 5-trimethylmethcathinone HCL in a piperazenic analog, a false positive. Conversely, representative compounds producing negative results are shown here.The first is a false negative result produced by MDPBP HCL, while the other three are true negative results of an amino acid, drug precursor, and amphetamine. Although the drug precursor is yellow-orange color, this occurred before the heating step. Finally, reactions with cathinone mixtures are not affected and show positive results.After watching this video, you should have a good understanding of how to perform a simple color test to detect the presence of synthetic cathinones in seized material. While attempting this procedure, it is important to remember that this protocol is intended to be used for presumptive identification. In a forensic context, sophisticated instrumentation, such as mass spectrometry, must be performed in order to confirm any identifications.

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Towards Biomimicking Wood: Fabricated Free-standing Films of Nanocellulose, Lignin, and a Synthetic Polycation

Woody materials are comprised of plant cell walls that contain a layered secondary cell wall composed of structural polymers of polysaccharides and lignin. Layer-by-layer (LbL) assembly process which relies on the assembly of oppositely charged molecules from aqueous solutions was used to build a freestanding composite film of isolated wood polymers of lignin and oxidized nanofibril cellulose (NFC). To facilitate the assembly of these negatively charged polymers, a positively charged polyelectrolyte, poly(diallyldimethylammomium chloride) (PDDA), was used as a linking layer to create this simplified model cell wall. The layered adsorption process was studied quantitatively using quartz crystal microbalance with dissipation monitoring (QCM-D) and ellipsometry. The results showed that layer mass/thickness per adsorbed layer increased as a function of total number of layers. The surface coverage of the adsorbed layers was studied with atomic force microscopy (AFM). Complete coverage of the surface with lignin in all the deposition cycles was found for the system, however, surface coverage by NFC increased with the number of layers. The adsorption process was carried out for 250 cycles (500 bilayers) on a cellulose acetate (CA) substrate. Transparent free-standing LBL assembled nanocomposite films were obtained when the CA substrate was later dissolved in acetone. Scanning electron microscopy (SEM) of the fractured cross-sections showed a lamellar structure, and the thickness per adsorption cycle (PDDA-Lignin-PDDA-NC) was estimated to be 17 nm for two different lignin types used in the study. The data indicates a film with highly controlled architecture where nanocellulose and lignin are spatially deposited on the nanoscale (a polymer-polymer nanocomposites), similar to what is observed in the native cell wall.

The objective of this research was to form synthetic plant cell wall tissue using layer-by-layer assembly of nanocellulose fibrils and isolated lignin assembled from dilute aqueous suspensions.&#160; Surface measurement techniques of quartz crystal microbalance and atomic force microscopy were used to monitor the formation of the polymer-polymer nanocomposite material.

Woody materials are comprised of plant cell walls that contain a layered secondary cell wall composed of structural polymers of polysaccharides and ...

Optimization of Synthetic Proteins: Identification of Interpositional Dependencies Indicating Structurally and/or Functionally Linked Residues

Protein alignments are commonly used to evaluate the similarity of protein residues, and the derived consensus sequence used for identifying functional units (e.g., domains). Traditional consensus-building models fail to account for interpositional dependencies &#8211; functionally required covariation of residues that tend to appear simultaneously throughout evolution and across the phylogentic tree. These relationships can reveal important clues about the processes of protein folding, thermostability, and the formation of functional sites, which in turn can be used to inform the engineering of synthetic proteins. Unfortunately, these relationships essentially form sub-motifs which cannot be predicted by simple &#8220;majority rule&#8221; or even HMM-based consensus models, and the result can be a biologically invalid &#8220;consensus&#8221; which is not only never seen in nature but is less viable than any extant protein. We have developed a visual analytics tool, StickWRLD, which creates an interactive 3D representation of a protein alignment and clearly displays covarying residues. The user has the ability to pan and zoom, as well as dynamically change the statistical threshold underlying the identification of covariants. StickWRLD has previously been successfully used to identify functionally-required covarying residues in proteins such as Adenylate Kinase and in DNA sequences such as endonuclease target sites.

Synthetic protein sequences based on consensus motifs typically ignore co-evolving residues, that imply interpositional dependencies (IPDs). IPDs can be essential to activity, and designs that disregard them may result in suboptimal results. This protocol uses StickWRLD to identify IPDs and help inform rational protein design, resulting in more efficient results.

Protein alignments are commonly used to evaluate the similarity of protein residues, and the derived consensus sequence used for identifying functional ...

A Filter-based Surface Enhanced Raman Spectroscopic Assay for Rapid Detection of Chemical Contaminants

We demonstrate a method to fabricate highly sensitive surface-enhanced Raman spectroscopic (SERS) substrates using a filter syringe system that can be applied to the detection of various chemical contaminants. Silver nanoparticles (Ag NPs) are synthesized via reduction of silver nitrate by sodium citrate. Then the NPs are aggregated by sodium chloride to form nanoclusters that could be trapped in the pores of the filter membrane. A syringe is connected to the filter holder, with a filter membrane inside. By loading the nanoclusters into the syringe and passing through the membrane, the liquid goes through the membrane but not the nanoclusters, forming a SERS-active membrane. When testing the analyte, the liquid sample is loaded into the syringe and flowed through the Ag NPs coated membrane. The analyte binds and concentrates on the Ag NPs coated membrane. Then the membrane is detached from the filter holder, air dried and measured by a Raman instrument. Here we present the study of the volume effect of Ag NPs and sample on the detection sensitivity as well as the detection of 10 ppb ferbam and 1 ppm ampicillin using the developed assay.

A procedure for fabrication and performing the filter-based surface enhanced Raman spectroscopic (SERS) assay for the detection of chemical contaminants (i.e., pesticide ferbam and antibiotic ampicillin) is presented.

We demonstrate a method to fabricate highly sensitive surface-enhanced Raman spectroscopic (SERS) substrates using a filter syringe system that can be ...

HKUST-1 as a Heterogeneous Catalyst for the Synthesis of Vanillin

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately 200 different odorant compounds in addition to vanillin. The natural extraction of vanillin (from the orchid Vanilla planifolia, Vanilla tahitiensis and Vanilla pompon) represents only 1% of the worldwide production and since this process is expensive and very long, the rest of the production of vanillin is synthesized. Many biotechnological approaches can be used for the synthesis of vanillin from lignin, phenolic stilbenes, isoeugenol, eugenol, guaicol, etc., with the disadvantage of harming the environment since these processes use strong oxidizing agents and toxic solvents. Thus, eco-friendly alternatives on the production of vanillin are very desirable and thus, under current investigation. Porous coordination polymers (PCPs) are a new class of highly crystalline materials that recently have been used for catalysis. HKUST-1 (Cu3(BTC)2(H2O)3, BTC = 1,3,5-benzene-tricarboxylate) is a very well known PCP which has been extensively studied as a heterogeneous catalyst. Here, we report a synthetic strategy for the production of vanillin by the oxidation of trans-ferulic acid using HKUST-1 as a catalyst.

The conversion of trans-ferulic acid to vanillin was achieved by heterogeneous catalysis. HKUST-1 was employed in this synthesis and the essential step in the catalytic process was the generation of unsaturated metal sites. Thus, when the catalyst was activated under vacuum, full vanillin conversion (yield of 95%) was obtained.

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately ...

Using Capillary Electrophoresis to Quantify Organic Acids from Plant Tissue: A Test Case Examining Coffea arabica Seeds

Carboxylic acids are organic acids containing one or more terminal carboxyl (COOH) functional groups. Short chain carboxylic acids (SCCAs; carboxylic acids containing three to six carbons), such as malate and citrate, are critical to the proper functioning of many biological systems, where they function in cellular respiration and can serve as indicators of cell health. In foods, organic acid content can have significant impact on taste, with increased SCCA levels resulting in a sour or &#34;acid&#34; taste. Because of this, methods for the rapid analysis of organic acid levels are of particular interest to the food and beverage industries. Unfortunately, however, most methods used for SCCA quantification are dependent on time-consuming protocols requiring the derivatization of samples with hazardous reagents, followed by costly chromatographic and/or mass spectrometric analyses. This method details an alternate method for the detection and quantification of organic acids from plant material and food samples using free zonal capillary electrophoresis (CZE), sometimes simply referred to as capillary electrophoresis (CE). CZE provides a cost-effective method for measuring SCCAs with a low limit of detection (0.005 mg/ml). This article details the extraction and quantification of SCCAs from plant samples. While the method provided focuses on measurement of SCCAs from coffee beans, the method provided can be applied to multiple plant-based food materials.

Using Capillary Electrophoresis to Quantify Organic Acids from Plant Tissue: A Test Case Examining Coffea arabica Seeds

This article presents a method for the detection and quantification of organic acids from plant material using free zonal capillary electrophoresis. An example of the potential application of this method, determining the effects of a secondary fermentation on organic acid levels in coffee seeds, is provided.

Carboxylic acids are organic acids containing one or more terminal carboxyl (COOH) functional groups. Short chain carboxylic acids (SCCAs; carboxylic ...

NMR Spectroscopy as a Robust Tool for the Rapid Evaluation of the Lipid Profile of Fish Oil Supplements

The western diet is poor in n-3 fatty acids, therefore the consumption of fish oil supplements is recommended to increase the intake of these essential nutrients. The objective of this work is to demonstrate the qualitative and quantitative analysis of encapsulated fish oil supplements using high-resolution 1H and 13C NMR spectroscopy utilizing two different NMR instruments; a 500 MHz and an 850 MHz instrument. Both proton (1H) and carbon (13C) NMR spectra can be used for the quantitative determination of the major constituents of fish oil supplements. Quantification of the lipids in fish oil supplements is achieved through integration of the appropriate NMR signals in the relevant 1D spectra. Results obtained by 1H and 13C NMR are in good agreement with each other, despite the difference in resolution and sensitivity between the two nuclei and the two instruments. 1H NMR offers a more rapid analysis compared to 13C NMR, as the spectrum can be recorded in less than 1 min, in contrast to 13C NMR analysis, which lasts from 10 min to one hour. The 13C NMR spectrum, however, is much more informative. It can provide quantitative data for a greater number of individual fatty acids and can be used for determining the positional distribution of fatty acids on the glycerol backbone. Both nuclei can provide quantitative information in just one experiment without the need of purification or separation steps. The strength of the magnetic field mostly affects the 1H NMR spectra due to its lower resolution with respect to 13C NMR, however, even lower cost NMR instruments can be efficiently applied as a standard method by the food industry and quality control laboratories.

Here, high-resolution 1H and 13C Nuclear Magnetic Resonance (NMR) spectroscopy was used as a rapid and reliable tool for quantitative and qualitative analysis of encapsulated fish oil supplements.

The western diet is poor in n-3 fatty acids, therefore the consumption of fish oil supplements is recommended to increase the intake of these essential ...

Coulomb Explosion Imaging as a Tool to Distinguish Between Stereoisomers

This article shows how the COLTRIMS (Cold Target Recoil Ion Momentum Spectroscopy) or the "reaction microscope" technique can be used to distinguish between enantiomers (stereoisomers) of simple chiral species on the level of individual molecules. In this approach, a gaseous molecular jet of the sample expands into a vacuum chamber and intersects with femtosecond (fs) laser pulses. The high intensity of the pulses leads to fast multiple ionization, igniting a so-called Coulomb Explosion that produces several cationic (positively charged) fragments. An electrostatic field guides these cations onto time- and position-sensitive detectors. Similar to a time-of-flight mass spectrometer, the arrival time of each ion yields information on its mass. As a surplus, the electrostatic field is adjusted in a way that the emission direction and the kinetic energy after fragmentation lead to variations in the time-of-flight and in the impact position on the detector.
Each ion impact creates an electronic signal in the detector; this signal is treated by high-frequency electronics and recorded event by event by a computer. The registered data correspond to the impact times and positions. With these data, the energy and the emission direction of each fragment can be calculated. These values are related to structural properties of the molecule under investigation, i.e. to the bond lengths and relative positions of the atoms, allowing to determine molecule by molecule the handedness of simple chiral species and other isomeric features.

For small chiral species, Coulomb Explosion Imaging provides a new approach to determine the handedness of individual molecules.

This article shows how the COLTRIMS (Cold Target Recoil Ion Momentum Spectroscopy) or the "reaction microscope" technique can be used to distinguish ...

Electrochemical Impedance Spectroscopy as a Tool for Electrochemical Rate Constant Estimation

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). In the case of fast reversible electrochemical processes, current is predominantly affected by the rate of diffusion, which is the slowest and limiting stage. EIS is a powerful technique that allows separate analysis of stages of charge transfer that have different AC frequency response. The capability of the method was used to extract the value of charge transfer resistance, which characterizes the rate of charge exchange on the electrode-solution interface. The application of this technique is broad, from biochemistry up to organic electronics. In this work, we are presenting the method of analysis of organic compounds for optoelectronic applications.

Electrochemical impedance spectroscopy (EIS) of species that undergo reversible oxidation or reduction in solution was used for determination of rate constants of oxidation or reduction.

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). ...

An Electrochemical Cholesteric Liquid Crystalline Device for Quick and Low-Voltage Color Modulation

We demonstrate a method for fabricating a prototype reflective display device that contains cholesteric liquid crystal (LC) as an active component. The cholesteric LC is composed of a nematic LC 4&#39;-pentyloxy-4-cyanobiphenyl (5OCB), redox-responsive chiral dopant (FcD), and a supporting electrolyte 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMIm-OTf). The most important component is FcD. This molecule changes its helical twisting power (HTP) value in response to redox reactions. Therefore, in situ electrochemical redox reactions in the LC mixture allow for the device to change its reflection color in response to electrical stimuli. The LC mixture was introduced, by a capillary action, into a sandwich-type ITO glass cell comprising two glass slides with patterned indium tin oxide (ITO) electrodes, one of which was coated with poly(3,4-ethylenedioxythiophene)-co-poly(ethylene glycol) doped with perchlorate (PEDOT+). Upon application of +1.5 V, the reflection color of the device changed from blue (467 nm) to green (485 nm) in 0.4 s. Subsequent application of 0 V made the device recover the original blue color in 2.7 s. This device is characterized by its fastest electrical response and lowest operating voltage among any previously reported cholesteric LC device. This device could pave the way for the development of next generation reflective displays with low energy consumption rates.

A protocol for the fabrication of a reflective cholesteric liquid crystalline display device containing a redox-responsive chiral dopant allowing quick and low-voltage operation is presented.

We demonstrate a method for fabricating a prototype reflective display device that contains cholesteric liquid crystal (LC) as an active component. The ...

Preparation and Application of a New Bacterial Biosensor for the Presumptive Detection of Gunshot Residue

MicRoboCop is a biosensor that has been designed for a unique application in forensic chemistry. MicRoboCop is a system made up of three devices that, when used together, can indicate the presence of gunshot residue (GSR) by producing a fluorescence signal in the presence of three key analytes (antimony, lead, and organic components of GSR). The protocol describes the synthesis of the biosensors using Escherichia coli (E. coli), and the analytical chemistry methods used to evaluate the selectivity and sensitivity of the sensors. The functioning of the system is demonstrated by using GSR collected from the inside of a spent cartridge casing. Once prepared, the biosensors can be stored until needed and can be used as a test for these key analytes. A positive response from all three analytes provides a presumptive positive test for GSR, while each individual device has applications for detecting the analytes in other samples (e.g., a detector for lead contamination in drinking water). The main limitation of the system is the time required for a positive signal; future work may involve studying different organisms to optimize the response time.

A protocol is presented using synthetic biology techniques to synthesize a set of bacterial biosensors for the analysis of gunshot residue, and to test the functioning of the devices for their intended use using fluorescence spectroscopy.

MicRoboCop is a biosensor that has been designed for a unique application in forensic chemistry. MicRoboCop is a system made up of three devices that, ...