Sonic-spray introduction of liquid samples to hand-held Ion mobility spectrometry analyzers.

Sampling hazardous compounds in the form of solids and liquids is a growing need in the fields of homeland security and forensics. Chemical analysis of particles and droplets under field conditions is crucial for various tasks carried out by counter-terrorism and law enforcement units. The use of simple, small and low cost means to achieve this goal is constantly pursued. In this work, an approach for rapid, continuous generation of vapors from liquid samples using sonic spray (SS) as the sample introduction technique, followed by analysis using hand-held ion mobility spectrometry (IMS) vapor analyzers is presented. Transfer of analytes is demonstrated from liquid state to the gas phase at the inlet of an IMS detector using a sonic spray apparatus that consists of a nebulizer, spraying solution, a source of compressed gas and an unheated transfer line tube to the detector inlet nozzle. This technique does not require any electrical, radiative or thermal energy. Analysis of several narcotic substances including cocaine, methamphetamine and amphetamine, and of an explosive compound, TNT, is demonstrated, using two commercial devices as analyzers. Two sampling configurations are presented: direct sampling of liquid, either from a vial or a spill (SS-IMS) and extraction of a substance collected with a swab by dipping it in the spray solvent (ESS-IMS), being suitable for both drops and particles. Limits of detection of the presented method are comparable to those obtained with thermal desorption sample introduction of the commercial device. Time traces of the IMS signals show a continuous and stable signal with a short rise time. This sampling technique may offer competitive performance to that of common thermal desorption techniques, with the advantages of coupling to simpler, smaller and cheaper vapor detectors, optimized for field use, and of a continuous, pulseless sample or object interrogation.

Explosive vapour/particles detection using SERS substrates and a hand-held Raman detector.

We developed and optimized surface-enhanced Raman spectrometry (SERS) methods for trace analysis of explosive vapour and particles using a hand-held Raman spectrometer in the field. At first, limits of detection (LODs) using SERS methods based on a colloidal suspension of gold nanoparticles were measured under alkaline conditions and are as follows: pentaerythritol tetranitrate (PETN) (1.5 × 10-6 M, 6.9 ng), 1,3,5,7-tetranitro-1,3,5,7-tetrazoctane (HMX), 8.1 × 10-6 M, 35 ng; urea nitrate (UN), 9.2 × 10-4 M, 165 ng; 2,4,6-trinitrotoluene (TNT), 1.1 × 10-7 M, 0.35 ng. We developed SERS substrates that demonstrate the wide applicability of this technique for use in the field for explosive vapour and particles adsorbed on a surface based on Au nanoparticles that were optimal for the detection of the target materials in solution. Au nanoparticles were modified onto quartz fibres or a polyurethane sponge for vapour/particles detection. SERS detection of vapours of 2,4-dinitrotoluene (2,4-DNT) and 1,3-dinitrobenzene (1,3-DNB) was shown by sampling vapours onto Au-modified quartz fibres followed by hand-held Raman analysis with estimated minimum detection levels of 3.6 ng and 54 ng, respectively. The detection of 2,4-DNT using sponge-based SERS decorated with Au nanoparticles was also demonstrated; however, the sensitivity was lower than that observed using quartz fibres. The detection of TNT on a surface was performed by utilizing quartz-fibres precoated with alumina and modified with Au nanoparticles, and the detection of 10 µg (0.53 µg cm-2) of TNT was demonstrated.

Surface-enhanced Raman spectroscopy (SERS) for detection of VX and HD in the gas phase using a hand-held Raman spectrometer.

A sensitive surface-enhanced Raman spectroscopy (SERS) substrate was developed to enable hand-held Raman spectrometers to detect gas-phase VX and HD. The substrate comprised Au nanoparticles modified onto quartz fibres. Limits of detection (LOD) of 0.008 µg L-1 and 0.054 µg L-1 were achieved for VX and HD, respectively. Gas-phase experiments were performed using a homemade gas-phase flow system inside a climatic chamber at 25 °C and 50% relative humidity. Preliminary experiments were conducted using VX and HD in solution with Au and Ag nanoparticle colloidal suspensions. We developed and optimized several SERS methods for detection of VX and HD in solution. Gold nanoparticles were optimal for detection of VX and HD and were modified onto quartz fibres for gas-phase detection. The LODs for HD and VX detection in solution were 1.8 × 10-3 µg mL-1 (1.1 × 10-8 M) and 2.5 × 10-3 µg mL-1 (9.3 × 10-9 M), respectively. This study demonstrates that integration of SERS substrates with hand-held Raman spectrometers expands the applicability of Raman technology to homeland security, as reflected by increased sensitivity and gas-phase detection capabilities.

Gossypol-Capped Mitoxantrone-Loaded Mesoporous SiO2 NPs for the Cooperative Controlled Release of Two Anti-Cancer Drugs.

Mesoporous SiO2 nanoparticles, MP-SiO2 NPs, are functionalized with the boronic acid ligand units. The pores of the MP-SiO2 NPs are loaded with the anticancer drug mitoxantrone, and the pores are capped with the anticancer drug gossypol. The resulting two-drug-functionalized MP-SiO2 NPs provide a potential stimuli-responsive anticancer drug carrier for cooperative chemotherapeutic treatment. In vitro experiments reveal that the MP-SiO2 NPs are unlocked under environmental conditions present in cancer cells, e.g., acidic pH and lactic acid overexpressed in cancer cells. The effective unlocking of the capping units under these conditions is attributed to the acidic hydrolysis of the boronate ester capping units and to the cooperative separation of the boronate ester bridges by the lactate ligand. The gossypol-capped mitoxantrone-loaded MP-SiO2 NPs reveals preferential cytotoxicity toward cancer cells and cooperative chemotherapeutic activities toward the cancer cells. The MCF-10A epithelial breast cells and the malignant MDA-MB-231 breast cancer cells treated with the gossypol-capped mitoxantrone-loaded MP-SiO2 NPs revealed after a time-interval of 5 days a cell death of ca. 8% and 60%, respectively. Also, the gossypol-capped mitoxantrone-loaded MP-SiO2 NPs revealed superior cancer-cell death (ca. 60%) as compared to control carriers consisting of ß-cyclodextrin-capped mitoxantrone-loaded (ca. 40%) under similar loading of the mitoxantrone drug. The drugs-loaded MP-SiO2 NPs reveal impressive long-term stabilities.

Gossypol-cross-linked boronic acid-modified hydrogels: a functional matrix for the controlled release of an anticancer drug.

Anticancer drug gossypol cross-links phenylboronic acid-modified acrylamide copolymer chains to form a hydrogel matrix. The hydrogel is dissociated in an acidic environment (pH 4.5), and its dissociation is enhanced in the presence of lactic acid (an α-hydroxy carboxylic acid) as compared to formic acid. The enhanced dissociation of the hydrogel by lactic acid is attributed to the effective separation of the boronate ester bridging groups through the formation of a stabilized complex between the boronic acid substituent and the lactic acid. Because lactic acid exists in cancer cells in elevated amounts and the cancer cells' environment is acidic, the cross-linked hydrogel represents a stimuli-responsive matrix for the controlled release of gossypol. The functionality is demonstrated and characterized by rheology and other spectroscopic means.

Surface-enhanced Raman spectroscopy of organic molecules adsorbed on metallic nanoparticles.

The improvements in Raman instrumentation have led to the development of -portable, simple to operate, Raman instruments that can be used for on-site analysis of substances relevant for homeland security purposes such as chemical and biological warfare and explosives materials.Raman spectroscopy, however, suffers from limited sensitivity which can be overcome by Surface-Enhanced Raman Spectroscopy (SERS). SERS can enhance the Raman signal of a target molecule by 6-10 orders of magnitude. The increased sensitivity, together with Raman's molecular recognition capabilities and the availability of portable Raman instruments make SERS a powerful analytical tool for on site detection.In this work we studied the effect of target molecules and SERS-active substrate properties on the obtained SERS, using a field portable Raman spectrometer. Also reported herein is the SERS detection of the chemical warfare agent sulfur mustard (HD, 2,2 dichloroethyl sulfide). This study may serve as a basis for the development of SERS platform for homeland security purposes.

Surface-enhanced Raman scattering detection of cholinesterase inhibitors.

A new sensitive surface-enhanced Raman scattering (SERS) assay for detection of cholinesterase inhibitors such as organophosphorous pesticides using silver colloidal nanoparticles was developed and optimized. Acetylcholinesterase (AChE) mediated the hydrolysis of acetylthiocholine to produce thiocholine, which interacted with the silver nanoparticles to give a specific SERS spectrum. Variation in enzyme activity due to inhibition was measured from changes in intensity of a characteristic peak (772 cm(-1)) of the SERS spectrum that was directly correlated with the concentration of produced thiocholine. The method was demonstrated for the detection of paraoxon as reference AChE inhibitor. Limit of detection of paraoxon for 5 min incubation at 25 °C was 1.8×10(-8) M. This assay can be utilized for the detection of trace amounts of any AChE inhibitor.

Application of fluorescent nanocrystals (q-dots) for the detection of pathogenic bacteria by flow-cytometry.

Fluorescent semiconductor nanocrystals (q-dots) benefit from practical features such as high fluorescence intensity, broad excitation band and emission diameter dependency. These unique spectroscopic characterizations make q-dots excellent candidates for new fluorescent labels in multi-chromatic analysis, such as Flow-Cytometry (FCM). In this work we shall present new possibilities of multi-labeling and multiplex analysis of pathogenic bacteria, by Flow-Cytometry (FCM) analysis and new specific IgG-q-dots conjugates. We have prepared specific conjugates against B. anthracis spores (q-dots585-IgGalphaB. anthracis and q-dots655-IgGalphaB.anthracis). These conjugates enabled us to achieve double staining of B. anthracis spores which improve the FCM analysis specificity versus control Bacillus spores. Moreover, multiplexed analysis of B. anthracis spores and Y. pestis bacteria was achieved by using specific antibodies labeled with different q-dots to obtain: q-dots585-IgGalphaB. anthracis and q-dots655-IgGalphaY.pestis, each characterized by its own emission peak as a marker. Specific and sensitive multiplex analysis for both pathogens has been achieved, down to 10(3) bacteria per ml in the sample.

Separation and detection of VX and its methylphosphonic acid degradation products on a microchip using indirect laser-induced fluorescence.

The application of indirect LIF (IDLIF) technique for on-chip electrophoretic separation and detection of the nerve agent O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothiolate (VX) and its major phosphonic degradation products, ethyl methylphosphonic acid (EMPA) and methylphosphonic acid (MPA) was demonstrated. Separation and detection of MPA degradation products of VX and the nerve agent isopropyl methylphosphonofluoridate (GB) are presented. The negatively charged dye eosin was found to be a good fluorescent marker for both the negatively charged phosphonic acids and the positively charged VX, and was chosen as the IDLIF visualization fluorescent dye. Separation and detection of VX, EMPA, and MPA in a simple-cross microchip were completed within less than a minute, and consumed only a 50 pL sample volume. A characteristic system peak that appeared in all IDLIF electropherograms served as an internal standard that increased the reliability of peak identification. The negative peak of both VX and the MPAs is in agreement with indirect detection theory and with previous reports in the literature. The LOD of VX and EMPA by IDLIF was 30 and 37 microM, respectively. Despite the fact that the detection sensitivity is relatively low, the rapid simultaneous on-chip analysis of both VX and its degradation products as well as the separation and detection of the MPA degradation products of both VX and GB, increases detection reliability and may present a choice when sensitivity is not critical compared with speed and simplicity of the assay.

On-chip integrated hydrolysis, fluorescent labeling, and electrophoretic separation utilized for acetylcholinesterase assay.

A sensitive on-chip acetylcholinesterase (AChE) assay that serves as a basis for the development of a fully integrated on-chip AChE-inhibitor detection assay is presented. The sequential steps required for the on-chip analysis process were integrated into a microchip. Transport and mixing of the reagents occurred by a combination of electroosmosis and electrophoresis using computer-controlled electrokinetic transport. AChE-catalyzed hydrolysis of acetylthiocholine to thiocholine was determined by on-chip reaction of thiocholine with eosinmaleimide, and the resulting thioether was electrophoretically separated and detected by laser-induced fluorescence (LIF). Enzyme-substrate mixing and reaction by confluent flow of reagents was compared with electrophoretically mediated microanalysis (EMMA), based on injection of an enzyme plug, and the utilization of differences in electrophoretic mobility as a driving force for efficient mixing and reaction. Both methods yielded similar results, however the EMMA-plug technique is preferable. The EMMA-plug technique was optimized for length and pushing time of enzyme plug, length of dyes mixture plug, acetylthiocholine concentration, and detector location. Detection of O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothiolate (VX) and paraoxon, two AChE inhibitors, was demonstrated by off-chip mixing of the inhibitor and AChE, followed by the on-chip AChE assay. Limit of detection of VX for 5.5 min incubation and of paraoxon for 8 min incubation was 4x10(-10) and 4x10(-7) M, respectively. Utilization of the AChE microchip assay for inhibition kinetics was demonstrated also by evaluation of the inhibitor-enzyme bimolecular reaction constant (k(i)). The evaluated k(i) values for VX and paraoxon for AChE from the electric eel were 3.5 x 10(7) and 1.7 x 10(5) M(-1) min(-1), respectively, conforming well to reported values obtained by bulk methods.

Surface Reconstitution of a De Novo Synthesized Hemoprotein for Bioelectronic Applications.

A molecular rectifier and a bioelectrocatalytic assembly for the reduction of NO3- is provided by reconstitution of a de novo protein with two FeIII -protoporphyrin IX units. The function of the de novo protein can be tuned and tailored within the synthetic protocol.