Generation of Electronic Cigarette Aerosol by a Third-Generation Machine-Vaping Device: Application to Toxicological Studies

Electronic-cigarette (e-cig) devices use heat to produce an inhalable aerosol from a liquid (e-liquid) composed mainly of humectants, nicotine, and ...

Louisiana State University

Particulate matter (PM) is emitted during thermal decomposition of waste. During this process, aromatic compounds chemisorb to the surface of metal-oxide-containing PM, forming a surface-stabilized environmentally persistent free radical (EPFR). We hypothesized that EPFR-containing PM redox cycle to produce ROS and that this redox cycle is maintained in biological environments. To test our hypothesis, we incubated model EPFRs with the fluorescent probe dihydrorhodamine (DHR). Marked increases in DHR fluorescence were observed. Using a more specific assay, hydroxyl radicals ((•)OH) were also detected, and their level was further increased by cotreatment with thiols or ascorbic acid (AA), known components of epithelial lining fluid. Next, we incubated our model EPFR in bronchoalveolar lavage fluid (BALF) or serum. Detection of EPFRs and (•)OH verified that PM generate ROS in biological fluids. Moreover, incubation of pulmonary epithelial cells with EPFR-containing PM increased (•)OH levels compared to those in PM lacking EPFRs. Finally, measurements of oxidant injury in neonatal rats exposed to EPFRs by inhalation suggested that EPFRs induce an oxidant injury within the lung lining fluid and that the lung responds by increasing antioxidant levels. In summary, our EPFR-containing PM redox cycle to produce ROS, and these ROS are maintained in biological fluids and environments. Moreover, these ROS may modulate toxic responses of PM in biological tissues such as the lung. 

Model combustion-generated particulate matter containing persistent free radicals redox cycle to produce reactive oxygen species.

Combustion processes generate particulate matter that affects human health. When incineration fuels include components that are highly enriched in aromatic hydrocarbons (especially halogenated varieties) and redox-active metals, ultrafine particulate matter containing air-stable, environmentally persistent free radicals (EPFRs) is generated. The exposure to fine EPFRs (less than 2.5 μm in diameter) has been shown to negatively influence pulmonary and cardiovascular functions in living organisms. The goal of this study was to determine if these EPFRs have a direct effect on cytochrome P450 function. This was accomplished by direct addition of the EPFRs to rat liver microsomal preparations and measurement of several P450 activities using form-selective substrates. The EPFRs used in this study were formed by heating vapors from an organic compound (either monochlorophenol (MCP230) or 1,2-dichlorobenzene (DCB230)) and 5% copper oxide supported on silica (approximately 0.2 μm in diameter) to 230°C under vacuum. Both types of EPFRs (but not silica, physisorbed silica, or silica impregnated with copper oxide) dramatically inhibited the activities of CYP1A, CYP2B, CYP2E1, CYP2D2 and CYP3A when incubated at concentrations less than 0.1 mg/ml with microsomes and NADPH. Interestingly, at the same concentrations, the EPFRs did not inhibit HO-1 activity or the reduction of cytochrome c by NADPH-cytochrome P450 reductase. CYP2D2-selective metabolism by rat liver microsomes was examined in more detail. The inhibition of CYP2D2-selective metabolism by both DCB230- and MCP230-EPFRs appeared to be largely noncompetitive and was attenuated in the presence of catalase suggesting that reactive oxygen species may be involved in the mechanism of inhibition.

Environmentally persistent free radicals inhibit cytochrome P450 activity in rat liver microsomes.

A novel pH sensitive, colorimetric ionic liquid nanosensor based on phosphonium salts of fluorescein is reported. Herein, fluorescein salts of various stoichiometries were synthesized by use of a trihexyltetradecylphosphonium cation [TTP] in combination with dianionic [FL] and monoanionic [FL] fluorescein. Nanomaterials derived from these two compounds yielded contrasting colorimetric responses in neutral and acidic environments. Variations in fluorescence spectra as a function of pH were also observed. Examination of TEM and DLS data revealed significant expansion in the diameter of [TTP][FL] nanodroplets in acidic environments of variable pHs. A similar trend was also observed for [TTP][FL] nanoparticles. The pH dependent colorimetric and other optical properties of these nanomaterials are attributed to alterations in molecular orientations and stacking as suggested by measuring the absorption, fluorescence, and zeta potential. Since the pH is an important indicator for many diseases, including cancer, these nanosensors are considered to be potential candidates for biomedical applications.

Ionic Liquid-Based Fluorescein Colorimetric pH Nanosensors.

Electronic cigarettes (E-cigs) have experienced sharp increases in popularity over the past five years due to many factors, including aggressive marketing, increased restrictions on conventional cigarettes, and a perception that E-cigs are healthy alternatives to cigarettes. Despite this perception, studies on health effects in humans are extremely limited and in vivo animal models have not been generated. Presently, we determined that E-cig vapor contains 7 x 10(11) free radicals per puff. To determine whether E-cig exposure impacts pulmonary responses in mice, we developed an inhalation chamber for E-cig exposure. Mice that were exposed to E-cig vapor contained serum cotinine concentrations that are comparable to human E-cig users. E-cig exposure for 2 weeks produced a significant increase in oxidative stress and moderate macrophage-mediated inflammation. Since, COPD patients are susceptible to bacterial and viral infections, we tested effects of E-cigs on immune response. Mice that were exposed to E-cig vapor showed significantly impaired pulmonary bacterial clearance, compared to air-exposed mice, following an intranasal infection with Streptococcus pneumonia. This defective bacterial clearance was partially due to reduced phagocytosis by alveolar macrophages from E-cig exposed mice. In response to Influenza A virus infection, E-cig exposed mice displayed increased lung viral titers and enhanced virus-induced illness and mortality. In summary, this study reports a murine model of E-cig exposure and demonstrates that E-cig exposure elicits impaired pulmonary anti-microbial defenses. Hence, E-cig exposure as an alternative to cigarette smoking must be rigorously tested in users for their effects on immune response and susceptibility to bacterial and viral infections.

Exposure to electronic cigarettes impairs pulmonary anti-bacterial and anti-viral defenses in a mouse model.

Molecularly imprinted polymers (MIPs) are an important class of selective materials for molecular specific sensors and separations. Molecular imprinting using non-covalent interactions in aqueous conditions still remains a difficult challenge due to interruption of hydrogen-bonding or electrostatic interactions water. Newly developed crosslinking ionic liquids are demonstrated herein to overcome problems of synthesizing aqueous MIPs, adding to previous examples of ionic liquids used as monomers in non-aqueous conditions or used as MIP solvents. Vinylimidazole ionic liquid crosslinkers were synthesized and subsequently explored as matrix supports for fabrication of molecularly imprinted polymeric nanoGUMBOS (nanoparticles derived from a group of uniform materials based on organic salts). Each of the four crosslinkers incorporated a unique functional spacer between the vinylimidazole groups, and the performance of the corresponding molecularly imprinted polymers was evaluated using chiral recognition as the diagnostic. High uptake values for l-tryptophan were found in the 13-87μmol/g range; and chiral recognition was determined via binding ratios of l-tryptophan over d-tryptophan that ranged from 5:1 to 13:1 for polymers made using different crosslinkers. Not only are these materials good for chiral recognition, but the results highlight the utility of these materials for imprinting aqueous templates such as biological targets for theranostic agents. 

Ionic liquid crosslinkers for chiral imprinted nanoGUMBOS.

Cationic ionic liquids-based surfactants (ILS), such as 4-methyl pyridinium bromide (CPBr, where n=4,6,8), were used in preparation of polyacrylamide gels, sample buffer, and running buffer for cationic ILS polyacrylamide gel electrophoresis (ILS-PAGE). These ILS are liquids in the pure state and were selected for improved separation of ribonuclease b (Rib b) glycoforms in a single step and a protein mixture containing bovine serum albumin (BSA, pI-4.8, 66.5kDa), ovalbumin (Ova, pI-4.6, 44.3kDa), α-chymotrypsinogen (α-Chy, pI-8.8, 25.7kDa), myoglobin (Myo, pI-6.8, 16.9kDa), and cytochrome c (Cyt c, pI-10.0, 12.3kDa). Results acquired for Rib b glycoform separation by use of ILS were compared with conventional non-ILS surfactants-PAGE: sodium dodecylsulfate (SDS)-PAGE, cetyltrimethylammonium bromide (CTAB)-PAGE, and benzyldimethyl-n-hexadecylammonium chloride (16-BAC)-PAGE. A single protein band was observed with relatively short migration time in all the conventional PAGE techniques tested. In contrast, ILS-PAGE showed multiple bands with two distinct bands for Rib b protein. The two distinct bands of Rib b from ILS-PAGE were further analyzed using MALDI-MS. Examination of MALDI-MS spectral data revealed the presence of Rib b glycoforms. Furthermore, a two-dimensional isoelectric focusing (IEF)/SDS-PAGE map of Rib b protein revealed negative charge heterogeneity on the protein, which is a common observation for glycoproteins. This overall discovery greatly enhances the capability of using cationic ILS-PAGE for Rib b protein separation. Among all ILS tested, excellent protein separations were observed using CPBr ILS at concentrations of 0.05% (w/v) in polyacrylamide gels, 0.01% (w/v) in protein sample buffer, and 0.1% (w/v) in running buffer. Under these optimum conditions, all other tested proteins were separated as sharp bands with good resolution.

Cationic ionic liquid surfactant-polyacrylamide gel electrophoresis for enhanced separation of acidic and basic proteins with single-step ribonuclease b glycoforms separation.

Farhana Hasan

Department of Environmental Sciences,
College of the Coast & Environment,
Department of Environmental Sciences, College of the Coast & Environment

Louisiana State University

Generation of Electronic Cigarette Aerosol by a Third-Generation Machine-Vaping Device: Application to Toxicological Studies

Farhana Hasan

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Environmental Sciences,College of the Coast & Environment,Department of Environmental Sciences, College of the Coast & Environment

Louisiana State University

Generation of Electronic Cigarette Aerosol by a Third-Generation Machine-Vaping Device: Application to Toxicological Studies

Department of Environmental Sciences,
College of the Coast & Environment,
Department of Environmental Sciences, College of the Coast & Environment