High sensitivity detection of nanoparticles permeation through polymer membranes: A physico-chemical and nuclear imaging measurement approach.

Diffusion cells are devices made of donor and acceptor compartments (DC and AC), separated by a membrane. They are widely used in pharmaceutical, cosmetic, toxicology, and protective equipment tests (e.g., gloves) to measure the kinetics of permeants (molecules and nanoparticles) across biological membranes as the skin. However, rarely is the concentration of permeants in the AC measured in continuous or in real-time, and this limitation leads to significant discrepancies in the calculations of kinetic parameters that define the permeation mechanisms. In this study, a diffusion cell compatible with positron emission tomography was used to measure the permeation kinetics of nanoparticles across glove membranes. The technology allows for the measurement of nanoparticle concentration in real-time in the two compartments (DC and AC) and at a detection sensitivity several orders of magnitude higher compared with conventional spectroscopies, thus allowing a much more precise extraction of kinetic parameters. Ultra-small (<10 nm) gold nanoparticles were used as a model nanoparticle contaminant. They were radiolabeled, and their diffusion kinetics was measured in continuous through latex and nitrile polymer membranes. Permeation profiles were recorded at sub-nanomolar sensitivity and in real-time, thus allowing the high precision extraction of kinetic permeation parameters. The technology, methodology, and data extraction process developed in this work could be applied to measure in real-time the kinetics of diffusion of a whole range of potentially toxic molecules and nanoparticles across polymer membranes, including glove membranes.

A diffusion cell adapted to nuclear imaging instruments for the measurement of molecular release and pharmacokinetics across membranes.

Diffusion cells are routinely used in pharmacology to measure the permeation of pharmaceutical compounds and contaminants across membranes (biological or synthetic). They can also be used to study drug release from excipients. The device is made of a donor (DC) and an acceptor (AC) compartment, separated by a membrane. Usually, permeation of molecules across membranes is measured by sampling from the AC at different time points. However, this process disturbs the equilibrium of the cell. Furthermore, analytical techniques used in association with diffusion cells sometimes lack either accuracy, sensitivity, or both. This work reports on the development of nuclear imaging - compatible diffusion cells. The cell is made of a polymer transparent to high-energy photons typically detected in positron emission tomography (PET). It was tested in a finite-dose set-up experiment with a pre-clinical PET system. Porous cellulose membranes (3.5, 25 and 300 kDa), a common excipient in pharmacology, as well as for dialysis membranes, were used as test membranes. The radioisotope 89Zr chelated with deferoxamine B (DFO; 0.65 kDa), was used as an imaging probe (7-10 MBq; 0.2-0.3 nMol 89Zr-DFO). In medicine, DFO is also commonly used for iron removal treatments and pharmacological formulations often require the association of this molecule with cellulose. Permeation profiles were obtained by measuring the radioactivity in the DC and AC for up to 2 weeks. The kinetic profiles were used to extract lag time, influx, and diffusion coefficients of DFO across porous cellulose membranes. A sensitivity threshold of 0.005 MBq, or 3.4 fmol of 89Zr-DFO, was revealed. The lag time to permeation (τ) measured in the AC compartment, was found to be 1.33, 0.5, and 0.19 h with 3.5, 25, and 300 kDa membranes, respectively. Diffusion coefficients of 3.65 × 10-6, 8.33 × 10-6, and 4.74 × 10-5 cm2 h-1 where revealed, with maximal pseudo steady-state influx values (Jpss) of 6.55 × 10-6, 1.76 × 10-5, and 1.29 × 10-5 nmol cm-2 h-1. This study confirms the potential of the technology for monitoring molecular diffusion and release processes at low concentrations, high sensitivities, in real time and in a visual manner.

High-Sensitivity Permeation Analysis of Ultrasmall Nanoparticles Across the Skin by Positron Emission Tomography.

Ultrasmall nanoparticles (US-NPs; <20 nm in hydrodynamic size) are now included in a variety of pharmacological and cosmetic products, and new technologies are needed to detect at high sensitivity the passage of small doses of these products across biological barriers such as the skin. In this work, a diffusion cell adapted to positron emission tomography (PET), a highly sensitive imaging technology, was developed to measure the passage of gold NPs (AuNPs) in skin samples in continuous mode. US-AuNPs (3.2 nm diam.; TEM) were functionalized with deferoxamine (DFO) and radiolabeled with 89Zr(IV) (half-life: 3.3 days, matching the timeline of diffusion tests). The physicochemical properties of the functionalized US-AuNPs (US-AuNPs-PEG-DFO) were characterized by FTIR (DFO grafting; hydroxamate peaks: 1629.0 cm-1, 1569.0 cm-1), XPS (presence of the O═C-N C 1s peak of DFO at 287.49 eV), and TGA (organic mass fraction). The passage of US-AuNPs-PEG-DFO-89Zr(IV) in skin samples was measured by PET, and the diffusion parameters were extracted thereby. The signals of radioactive US-AuNPs-PEG-DFO-89Zr(IV) leaving the donor compartment, passing through the skin, and entering the acceptor compartment were detected in continuous at concentrations as low as 2.2 nM of Au. The high-sensitivity acquisitions performed in continuous allowed for the first time to extract the lag time to the start of permeation, the lag time to start of the steady state, the diffusion coefficients, and the influx data for AuNPs permeating into the skin. PET could represent a highly valuable tool for the development of nanoparticle-containing topical formulations of drugs and cosmetics.

Robust Superhydrophobic Cotton Fibers Prepared by Simple Dip-Coating Approach Using Chemical and Plasma-Etching Pretreatments.

The preparation of superhydrophobic textiles with high mechanical and chemical durability is challenging. Here, facile and fluorine-free methods, using alkali and plasma-etching treatments, followed by the addition of silica nanoparticles and tetraethyl orthosilicate (TEOS), were used to prepare superhydrophobic cotton surfaces. With different input variables and etching techniques, superhydrophobic cotton fabrics with high chemical and mechanical durability were successfully prepared, with contact angles up to 173°. A control of the surface architecture at the nanoscale in combination with a homogeneous repellent layer of TEOS in the cotton surface was achieved. The repellent properties of the as-prepared cotton remain stable under accelerated laundering and abrasion test conditions. The etching pretreatment by alkali or plasma plays a key role in obtaining superhydrophobic cotton surfaces.

Filtering performances of 20 protective fabrics against solid aerosols.

Workers can be exposed to solid airborne particles in some occupational environments, and they might be required to wear chemical protective clothing to prevent skin exposure. Dedicated standards exist to certify the protective value of such clothing, but they are not informative enough to identify the main pathways of entry for solid particles nor to compare performances between different chemical protective clothing. In this work, 20 non-woven fabrics used to make chemical protective clothing for solid particle protection were selected to be examined for both filtration and comfort performances. Nine were microporous fabrics (MP), 10 were multilayered nonwoven fibrous media (SMS) and one was a flash spun material (FS). To assess their filtration performances, fabrics were challenged in a benchtop wind tunnel with a 20-3,000 nm diameter sodium chloride aerosol at three low fabric face velocities (0.05, 0.15, 0.3 cm/sec). Airflow resistance and water vapor transmission rate were also measured to provide indications of comfort for the wearer. The penetration results led to the classification of the 20 fabrics into distinct groups of filtration efficiency. The data were analysed based on the porous media characteristics (thickness, fiber diameter, porosity, etc.). MPs were the most efficient fabrics, and SMSs showed a wide range of performances, mostly due to variations in the thickness of the filtering layer as well as to the fabric treatment. Measurements of airflow resistance and water vapor transmission rates revealed major differences between MPs and FSs and SMSs. This highlights the potential of some SMS fabrics to meet a compromise between protection and comfort.

Efficiency of five chemical protective clothing materials against nano and submicron aerosols when submitted to mechanical deformations.

Due to their potential toxicity, the use of nanoparticles in the workplace is a growing concern. Some studies indicate that nanoparticles can penetrate the skin and lead to adverse health effects. Since chemical protective clothing is the last barrier to protect the skin, this study aims to better understand nanoparticle penetration behaviour in dermal protective clothing under mechanical deformation. For this purpose, five of the most common types of fabrics used in protective clothing, one woven and four nonwoven, were chosen and submitted to different simulated exposure conditions. They were tested against polydispersed NaCl aerosols having an electrical-mobility diameter between 14 and 400 nm. A bench-scale exposure setup and a sampling protocol was developed to measure the level of penetration of the aerosols through the material samples of disposable coveralls and lab coat, while subjecting them to mechanical deformations to simulate the conditions of usage in the workplace. Particle size distribution of the aerosol was determined upstream and downstream using a scanning mobility particle sizer (SMPS). The measured efficiencies demonstrated that the performances of nonwoven materials were similar. Three nonwovens had efficiencies above 99%, while the woven fabric was by far, the least effective. Moreover, the results established that mechanical deformations, as simulated for this study, did not have a significant effect on the fabrics' efficiencies.

Analysis of airborne pesticides from different chemical classes adsorbed on Radiello® Tenax® passive tubes by thermal-desorption-GC/MS.

An analytical methodology using automatic thermal desorption (ATD) and GC/MS was developed for the determination of 28 pesticides of different chemical classes (dichlobenil, carbofuran, trifluralin, clopyralid, carbaryl, flazasulfuron, mecoprop-P, dicamba, 2,4-MCPA, dichlorprop, 2,4-D, triclopyr, cyprodinil, bromoxynil, fluroxypyr, oxadiazon, myclobutanil, buprofezin, picloram, trinexapac-p-ethyl, ioxynil, diflufenican, tebuconazole, bifenthrin, isoxaben, alphacypermethrin, fenoxaprop and tau-fluvalinate) commonly used in nonagricultural areas in atmospheric samples. This methodology was developed to evaluate the indoor and outdoor atmospheric contamination by nonagricultural pesticides. Pesticides were sampled passive sampling tubes containing Tenax® adsorbent. Since most of these pesticides are polar (clopyralid, mecoprop-P, dicamba, 2,4-MCPA, dichlorprop, 2,4-D, triclopyr, bromoxynil, fluroxypyr, picloram, trinexapac-p-ethyl and ioxynil), a derivatisation step is required. For this purpose, a silylation step using N-(t-butyldimethylsilyl)-N-methyltrifluoroacetamide (MtBSTFA) was added before thermal desorption. This agent was chosen since it delivers very specific ions on electronic impact (m/z = M-57). This method was established with special consideration for optimal thermal desorption conditions (desorption temperature, desorb flow and duration; trap heating duration and flow; outlet split), linear ranges, limits of quantification and detection which varied from 0.005 to 10 ng and from 0.001 to 2.5 ng, respectively, for an uncertainty varied from 8 to 30 %. The method was applied in situ to the analysis of passive tubes exposed during herbicide application to an industrial site in east of France.

SPME-based air sampling method for inhalation exposure assessment studies: case study on perchlorethylene exposure in dry cleaning.

Exposure to perchlorethylene, especially for dry cleaning workers and for people living near dry cleaning shops, could lead to several diseases and disorders. This study examines the value of solid-phase microextraction (SPME) for sampling perchlorethylene in the atmosphere of dry cleaning shops. Carboxen/polydimethylsiloxane (CAR/PDMS) in 0.5-cm retracted mode was selected. There were no significant differences between sampling rates at different temperatures (range of 20 to 30 °C) and air velocities (2 to 50 cm/s). On the opposite, relative humidity (RH) had a significant effect on sampling rates. Method reproducibility was realized in the laboratory and field conditions and was 6.2 % and 7 to 11 %, respectively. Repeatability was also determined as 8.9 %. Comparison of the results according to the American Industrial Hygiene Association exposure assessment strategy showed the SPME sampler yields more conservative results in comparison with traditional standard method.

Application of XAD-2 resin-based passive samplers and SPME-GC-MS/MS analysis for the monitoring of spatial and temporal variations of atmospheric pesticides in Luxembourg.

Passive air sampling has been shown to be a very interesting alternative to high-volume sampling by overcoming its disadvantages (size, weight, expensiveness). However, to date, only limited data is available about passive air sampling of current-use pesticides. In order to test if passive samplers allow monitoring of spatial and temporal variations of atmospheric pesticide concentrations, five XAD-2-resin based passive air samplers were deployed at five locations in Luxembourg. Samplers were analyzed using accelerated solvent extraction coupled to solid-phase microextraction and gas chromatography with tandem mass spectrometry. Collected data was used to study the spatial and temporal variations of the concentrations of the compounds. Twenty two pesticides were detected between March and October, while no pesticides were detected from November to February. Highest concentrations were measured on the rural sites, suggesting that the used XAD-2 resin-based passive samplers allow the simultaneous monitoring of multiple current-use pesticides and identifying spatial and temporal variations.

Atmospheric concentrations of PCDD/Fs, dl-PCBs and some pesticides in northern Algeria using passive air sampling.

Two monitoring campaigns were conducted in northern Algeria to assess the contamination level of pesticides and persistent organic pollutants (POPs) in ambient air. Six pesticides (α- and γ-hexachlorocyclohexane, fenitrothion, malathion, chlorpyrifos and λ-cyhalothrin) were monitored at two different sampling locations during the first campaign. The passive sampling was performed at a semi urban/industrial site but also in a rural area between July to September 2008. The pesticides levels, analyzed by GC/MS/MS, ranged from 16 pg m(-3) to 11 ng m(-3). The second campaign was carried out from May to November 2009. The polychlorodibenzo-p-dioxins, dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) concentrations were evaluated at an urban/industrial and at an industrial site. The PCDD/Fs and dl-PCBs, analyzed by HRGC/HRMS, ranged from 249 to 923 fg TEQ m(-3). In addition to passive sampling, active sampling using an isokinetic sampler was also performed at an industrial waste incinerator. The PCDD/Fs and dl-PCBs found was 268 pg TEQ m(-3). This paper presents the first measurements of PCDD/Fs, dl-PCBs and pesticides in rural, urban and industrial areas of northern Algeria.

Field application of SPME as a novel tool for occupational exposure assessment with inhalational anesthetics.

Occupational exposure to inhalational anesthetics occurs routinely in operating rooms. It could induce serious health hazards and diseases. This exposure assessment is a crucial step in determining risks. In this study, a pen-shaped holder for solid-phase microextraction (SPME) sampler was successfully applied as a time-weighted average sampling tool for workshift exposure assessment of operation room staff to halothane. It proved to be very convenient for use in occupational environments such as operation rooms. Samples were analyzed by a gas chromatography-mass spectrometry. The validity of the SPME method was checked in real-world conditions with Occupational Safety and Health Administration (OSHA) 103 standard method for the determination of inhalational anesthetics. A good agreement between OSHA 103 and SPME methods was obtained and results demonstrated no statistically significant differences in anesthetic concentrations determined by the two analytical methods (p ≥ 0.05). It is concluded that SPME in retracted mode could successfully be applied in occupational exposure assessment purposes.

Flexibility of solid-phase microextraction for passive sampling of atmospheric pesticides.

For low volatile pesticides, the applications of solid-phase microextraction (SPME) as an air sampler were reported with sampling time chosen in the linear stage of the sorption kinetics because of long equilibrium time. In these pre-equilibrium conditions, sampling rates (SRs) expressed as the volume of air sampled by the SPME sampler per unit of time, were used to estimate analytes concentrations in air. In the present study, to achieve good extraction performance and accurate calibration, the sorption kinetics of several pesticides with SPME were investigated in detail, with a focus on parameters influencing SRs. Linear air velocity was found to be the main parameter affecting SRs. For exposed fibers, with air velocities below 20-25 cms(-1), SRs increased with increasing air velocity. When linear air velocity was equal to or greater than 25-30 cms(-1), it had little effect on SRs. To improve the flexibility of SPME, different configurations of SPME were compared, i.e. different lengths of fibers exposed, retracted fibers, exposed fibers with grids. SRs were linearly proportional to exposed lengths of fibers. Using grids, lower SRs and wider calibration time range were achieved. SRs for retracted fibers were the lowest among the different experimented configurations. The accuracy of calibration was improved and more flexibility of SPME was provided.

Sampling atmospheric pesticides with SPME: Laboratory developments and field study.

To estimate the atmospheric exposure of the greenhouse workers to pesticides, solid phase microextraction (SPME) was used under non-equilibrium conditions. Using Fick's law of diffusion, the concentrations of pesticides in the greenhouse can be calculated using pre-determined sampling rates (SRs). Thus the sampling rates (SRs) of two modes of SPME in the lab and in the field were determined and compared. The SRs for six pesticides in the lab were 20.4-48.3 mL min(-1) for the exposed fiber and 0.166-0.929 mL min(-1) for the retracted fiber. In field sampling, two pesticides, dichlorvos and cyprodinil were detected with exposed SPME. SR with exposed SPME for dichlorvos in the field (32.4 mL min(-1)) was consistent with that in the lab (34.5 mL min(-1)). SR for dichlorvos in the field (32.4 mL min(-1)) was consistent with that in the lab (34.5 mL min(-1)). The trends of temporal concentration and the inhalation exposure were also obtained.

Pesticides in the atmosphere across Canadian agricultural regions.

The Canadian Atmospheric Network for Currently Used Pesticides (CANCUP) was the first comprehensive, nationwide air surveillance study of pesticides in Canada. This paper presentsthe atmospheric occurrence and distribution of pesticides including organochlorine pesticides (OCPs), organophosphate pesticides (OPPs), acid herbicides (AHs), and neutral herbicides (NHs) during the spring to summer of 2004 and 2005 across agricultural regions in Canada. Atmospheric concentrations of pesticides varied within years and time periods, and regional characteristics were observed including the following: (i) highest air concentrations of several herbicides (e.g., mecoprop, triallate, and ethalfluralin) were found at Bratt's Lake, SK, a site in the Canadian Prairies; (ii) the west-coast site at Abbotsford, BC, had the maximum concentrations of diazinon; (iii) the fruit and vegetable growing region in Vineland, ON, showed highest levels for several insecticides including chlorpyrifos, endosulfan, and azinphos-methyl; (iv) high concentrations of atrazine and metolachlor were measured at St. Anicet, QC, a corn-growing region; (v) the Kensington site in PEI, Canada's largest potato-producing province, exhibited highest level of dimethoate. Analysis of particle- and gas-phase fractions of air samples revealed that most pesticides including OCPs, OPPs, and NHs exist mainly in the gas phase, while AHs exhibit more diversity in particle-gas partitioning behavior. This study also demonstrated that stirred up soil dust does not account for pesticides that are detected in the particle phase. The estimated dry and wet deposition fluxes indicate considerable atmospheric inputs for some current-use pesticides (CUPs). This data set represents the first measurements for many pesticides in the atmosphere, precipitation, and soil for given agricultural regions across Canada.

Sources and occurrence of dacthal in the Canadian atmosphere.

Dacthal is a herbicide that can undergo long-range atmospheric transport. Due to limited use in Canada, its occurrence in the Canadian environment is likely associated with transboundary flow from the United States where 100 times more dacthal is used. To investigate its atmospheric distribution and possible sources, two sampling strategies were applied. First, polyurethane foam-disk passive air samplers were deployed across the country from the spring to summer of 2004 and 2005. Results showed highest dacthal concentrations at two sites in southern Ontario (max: 50 pg m(-3)) and much lower concentrations in other agricultural regions across Canada. Second, daily high-volume air samples were collected at a field site in north Toronto (Downsview). Sampling at this site was triggered by real-time meteorological forecast models that indicated when air flow to the site originated in the United States. Two such events, one in late June and one in late September 2005, were sampled. In both cases, elevated dacthal concentrations were captured (e.g., up to 319 pg m(-3) in the June event) and they were well correlated with transboundary flow from the United States. Finally, the octanol--air partition coefficient (K(OA)) of dacthal and other current-use pesticides was measured. K(OA) was used to derive a particle--gas partitioning coefficient (K(p)) for dacthal (Log K(p) = -4.1), indicating that this compound should exist mainly in the gas phase.

Polyurethane foam (PUF) disks passive air samplers: wind effect on sampling rates.

Different passive sampler housings were evaluated for their wind dampening ability and how this might translate to variability in sampler uptake rates. Polyurethane foam (PUF) disk samplers were used as the sampling medium and were exposed to a PCB-contaminated atmosphere in a wind tunnel. The effect of outside wind speed on PUF disk sampling rates was evaluated by exposing polyurethane foam (PUF) disks to a PCB-contaminated air stream in a wind tunnel over air velocities in the range 0 to 1.75 m s-1. PUF disk sampling rates increased gradually over the range 0-0.9 m s-1 at approximately 4.5-14.6 m3 d-1 and then increased sharply to approximately 42 m3 d-1 at approximately 1.75 m s-1 (sum of PCBs). The results indicate that for most field deployments the conventional 'flying saucer' housing adequately dampens the wind effect and will yield approximately time-weighted air concentrations.

A simple calibration procedure for volatile organic compounds sampling in air with adsorptive solid-phase microextraction fibres.

Adsorptive solid-phase microextraction (SPME) fibres have proven to be a reliable means of sampling volatile organic compounds (VOCs) in air. In this work, polydimethylsiloxane/carboxen (PDMS/CAR) fibres were used to test a new approach of air sampling strategy with SPME in the lab which could lighten calibration procedure and enhance the use of this already rapid, simple, convenient and cost effective sampling technique. Indeed, only one curve can be used whatever the extraction time chosen by the analyst under constant conditions of air velocity and temperature. Ficks' law of diffusion was used to model SPME grab sampling when the fibre was totally exposed to the air sample. Experimental sampling rates were then determined by GC-FID for different sampling conditions, i.e. in a flowing air stream of known velocity ("dynamic mode") and in a stagnant air ("static mode"). These sampling rates were found to be 3.50 and 17.80 mL min(-1) for acetone, 4.06 and 21.20 mL min(-1) for 1,2-dichloroethane, 5.10 and 27.80 mL min(-1) for toluene and 5.36 and 30.80 mL min(-1) for butyl acetate, for static and dynamic sampling modes respectively. Deviation from linearity of the calibration curves, indicating that a significant fraction of the adsorption sites are occupied, were determined. They were found to be approximately equal to 0.9, 1.57, 3.82 and 4.37 nmol for acetone, dichloroethane, toluene and butyl acetate, respectively. Experimentally determined sampling rates of these isolated compounds were also valid when a complex equimolar gaseous mixture was investigated, but deviation from linearity appears earlier. Then, for a given application, sampling times should be chosen very carefully to avoid competitive adsorption and hence, bad quantitative analysis results.

Dynamic versus static sampling for the quantitative analysis of volatile organic compounds in air with polydimethylsiloxane-carboxen solid-phase microextraction fibers.

Polydimethylsiloxane-Carboxen solid-phase microextraction fibers are now well known to be very efficient trapping media for the analysis of volatile organic compound (VOC) traces in air. However, competitive adsorption, due to the nature of the coating, considerably limits analyte quantitation. In this contribution, different experimental conditions are investigated to achieve quantitative analysis. Static and dynamic sampling were compared for the analysis of 11 VOCs in a standard gaseous mixture at different extraction times (1, 5, 15 and 45 min). The same experiments were performed with four isolated compounds. Adsorption results from gas mixture and isolated compounds were compared and a common linear range (i.e., where quantitative analysis is conceivable) was determined. When sampling was in the dynamic mode, compounds with lower affinity for the coating showed a very narrow linear range, meaning that competition for adsorption was quickly discriminative. The same experiments in static mode allowed one to obtain wider linear ranges for all compounds, especially for lower-affinity compounds: for a 1 min sampling time, acetone showed a linear adsorption range from 3 to 60 microg m(-3) in the dynamic mode which extended from 5 to 300 microg m(-3) in the static mode.