Assessing vitamin E acetate as a proxy for E-cigarette additives in a realistic pulmonary surfactant model.

Additives in vaping products, such as flavors, preservatives, or thickening agents, are commonly used to enhance user experience. Among these, Vitamin E acetate (VEA) was initially thought to be harmless but has been implicated as the primary cause of e-cigarette or vaping product use-associated lung injury, a serious lung disease. In our study, VEA serves as a proxy for other e-cigarette additives. To explore its harmful effects, we developed an exposure system to subject a pulmonary surfactant (PSurf) model to VEA-rich vapor. Through detailed analysis and atomic-level simulations, we found that VEA tends to cluster into aggregates on the PSurf surface, inducing deformations and weakening its essential elastic properties, critical for respiratory cycle function. Apart from VEA, our experiments also indicate that propylene glycol and vegetable glycerin, widely used in e-liquid mixtures, or their thermal decomposition products, alter surfactant properties. This research provides molecular-level insights into the detrimental impacts of vaping product additives on lung health.

Permeability of triamcinolone acetonide, released from mucoadhesive films, through a buccal mucosa-mimetic barrier: Permeapad™.

OBJECTIVES: The permeability of triamcinolone acetonide (TA), from bilayer mucoadhesive buccal films, through a biomimetic membrane, Permeapad™, was investigated employing Franz diffusion cell. The delivery systems composition and ethyl cellulose (EC) backing layer, on drug permeability, were assessed. METHODS: Three TA-loaded films were tested; hydroxypropyl methylcellulose (HPMC K4M; bilayer [F1] and monolayer), HPMC K4M/Polyvinylpyrrolidone (PVP): 90/10 [F2], and HPMC K15M film [F3]. All films contained propylene glycol (PG-plasticiser). TA solution alone was used as a control. TA permeability via a Permeapad™ barrier, simulating buccal mucosa, was assessed over 8 h using a Franz diffusion cell. TA permeated into the receptor compartment, released in the donor compartment, and located on/within the Permeapad™ barrier were analysed using UV-spectrophotometer. RESULTS: 45.7 % drug retention within the Permeapad™ barrier was delivered from F1 (highest). F1, F2, and F3 significantly improved the TA's permeability through Permeapad™, compared to TA solution alone (e.g., 8.5 % TA-solution, 21.5 %-F1), attributed to the synergy effect of HPMC and propylene glycol acting as penetration enhancers. F1 displayed a significant increase in drug permeability (receptor compartment; 21.5 %) compared to F3 (17.0 %). PVP significantly enhanced drug permeability (27.5 %). Impermeable EC backing layer controlled unidirectional drug release and reduced drug loss into the donor compartment (e.g., ∼28 % for monolayer film to ∼10 % for bilayer film, F1). SIGNIFICANCE: The mucoadhesive films demonstrated improved TA permeability via Permeapad™. The findings suggest that these bilayer mucoadhesive films, particularly F1, hold promise for the effective topical treatment of oral mucosa disorders, such as recurrent aphthous stomatitis and oral lichen planus.

Solubility and thermodynamics properties of salicylic acid in binary mixtures 1-propanol and propylene glycol/ethylene glycol monomethyl ether at different temperatures.

The research aimed to investigate the solubility and thermodynamics of salicylic acid in two binary solvent mixtures of (1-propanol+propylene glycol) and (ethylene glycol monomethyl ether+1-propanol). The study was conducted in the temperature range of 293.2 to 313.2K. To analyze the experimental solubility data, several linear and nonlinear cosolvency models, such as the van't Hoff, Jouyban-Acree, Jouyban-Acree-van't Hoff, mixture response surface, and modified Wilson models were employed. The models' effectiveness was evaluated by comparing the mean relative deviations of the back-calculated solubility data to the experimental values. In addition, the apparent thermodynamic parameters, including Gibbs energy, enthalpy, and entropy, were calculated using the van't Hoff and Gibbs equations. Furthermore, the study measured the density values for salicylic acid-saturated mixtures and represented them mathematically through the Jouyban-Acree model.

Pitfalls in the Detection of Volatiles Associated with Heated Tobacco and e-Vapor Products When Using PTR-TOF-MS.

We investigated the applicability of proton transfer reaction-time-of-flight mass spectrometry (PTR-TOF-MS) for quantitative analysis of mixtures comprising glycerin, acetol, glycidol, acetaldehyde, acetone, and propylene glycol. While PTR-TOF-MS offers real-time simultaneous determination, the method selectivity is limited when analyzing compounds with identical elemental compositions or when labile compounds present in the mixture produce fragments that generate overlapping ions with other matrix components. In this study, we observed significant fragmentation of glycerin, acetol, glycidol, and propylene glycol during protonation via hydronium ions (H3O+). Nevertheless, specific ions generated by glycerin (m/z 93.055) and propylene glycol (m/z 77.060) enabled their selective detection. To thoroughly investigate the selectivity of the method, various mixtures containing both isotope-labeled and unlabeled compounds were utilized. The experimental findings demonstrated that when samples contained high levels of glycerin, it was not feasible to perform time-resolved analysis in H3O+ mode for acetaldehyde, acetol, and glycidol. To overcome the observed selectivity limitations associated with the H3O+ reagent ions, alternative ionization modes were investigated. The ammonium ion mode proved appropriate for analyzing propylene glycol (m/z 94.086) and acetone (m/z 76.076) mixtures. Concerning the nitric oxide mode, specific m/z were identified for acetaldehyde (m/z 43.018), acetone (m/z 88.039), glycidol (m/z 73.028), and propylene glycol (m/z 75.044). It was concluded that considering the presence of multiple product ions and the potential influence of other compounds, it is crucial to conduct a thorough selectivity assessment when employing PTR-TOF-MS as the sole method for analyzing compounds in complex matrices of unknown composition.

Structural and aggregation changes of silver carp myosin induced with alcohols: Effects of ethanol, 1,2-propanediol, and glycerol.

This study investigated the effects of ethanol, 1,2-propanediol, and glycerol on the structure and aggregation behavior of silver carp (Hypophthalmichthys molitrix) myosin. All alcohols induced extensive alteration in the tertiary structure of myosin. Both ethanol and 1,2-propanediol further promoted an increase in the content of ß-sheets in myosin and induced myosin aggregation. While glycerol had almost no impact on the secondary structure of myosin. Molecular dynamics simulations revealed that increasing the concentration of ethanol and 1,2-propanediol affected the overall structural changes in the myosin heavy chain (MHC), while glycerol exerted a more pronounced effect on the MHC tail when compared to the MHC head. Disruption of the hydration layers induced by ethanol and 1,2-propanediol contributed to local structural changes in myosin. Glycerol at a concentration of 20% induced the formation of a larger hydration layer around the MHC tail, which facilitated the stabilization of the protein structure.

In vitro toxicological evaluation of aerosols generated by a 4th generation vaping device using nicotine salts in an air-liquid interface system.

BACKGROUND: Electronic cigarettes (EC) have gained popularity, especially among young people, with the introduction of fourth-generation devices based on e-liquids containing nicotine salts that promise a smoother vaping experience than freebase nicotine. However, the toxicological effects of nicotine salts are still largely unknown, and the chemical diversity of e-liquids limits the comparison between different studies to determine the contribution of each compound to the cytotoxicity of EC aerosols. Therefore, the aim of this study was to evaluate the toxicological profile of controlled composition e-liquid aerosols to accurately determine the effects of each ingredient based on exposure at the air-liquid interface. METHODS: Human lung epithelial cells (A549) were exposed to undiluted aerosols of controlled composition e-liquids containing various ratios of propylene glycol (PG)/vegetable glycerin (VG) solvents, freebase nicotine, organic acids, nicotine salts, and flavoured commercial e-liquids. Exposure of 20 puffs was performed at the air-liquid interface following a standard vaping regimen. Toxicological outcomes, including cytotoxicity, inflammation, and oxidative stress, were assessed 24 h after exposure. RESULTS: PG/VG aerosols elicited a strong cytotoxic response characterised by a 50% decrease in cell viability and a 200% increase in lactate dehydrogenase (LDH) production, but had no effects on inflammation and oxidative stress. These effects occurred only at a ratio of 70/30 PG/VG, suggesting that PG is the major contributor to aerosol cytotoxicity. Both freebase nicotine and organic acids had no greater effect on cell viability and LDH release than at a 70/30 PG/VG ratio, but significantly increased inflammation and oxidative stress. Interestingly, the protonated form of nicotine in salt showed a stronger proinflammatory effect than the freebase nicotine form, while benzoic acid-based nicotine salts also induced significant oxidative stress. Flavoured commercial e-liquids was found to be cytotoxic at a threshold dose of ≈ 330 µg/cm². CONCLUSION: Our results showed that aerosols of e-liquids consisting only of PG/VG solvents can cause severe cytotoxicity depending on the concentration of PG, while nicotine salts elicit a stronger pro-inflammatory response than freebase nicotine. Overall, aerosols from fourth-generation devices can cause different toxicological effects, the nature of which depends on the chemical composition of the e-liquid.

Enhancement of Benzene Emissions in Special Combinations of Electronic Nicotine Delivery System Liquid Mixtures.

Electronic nicotine delivery systems (ENDS) are battery-powered devices introduced to the market as safer alternatives to combustible cigarettes. Upon heating the electronic liquid (e-liquid), aerosols are released, including several toxicants, such as volatile organic compounds (VOCs). Benzene has been given great attention as a major component of the VOCs group as it increases cancer risk upon inhalation. In this study, several basic e-liquids were tested for benzene emissions. The Aerosol Lab Vaping Instrument was used to generate aerosols from ENDS composed of different e-liquid combinations: vegetable glycerin (VG), propylene glycol (PG), nicotine (nic), and benzoic acid (BA). The tested mixtures included PG, PG + nic + BA, VG, VG + nic + BA, 30/70 PG/VG, and 30/70 PG/VG + nic + BA. A carboxen polydimethylsiloxane fiber for a solid-phase microextraction was placed in a gas cell to trap benzene emitted from a Sub-Ohm Minibox C device. Benzene was adsorbed on the fiber during the puffing process and for an extra 15 min until it reached equilibrium, and then it was determined using gas chromatography-mass spectrometry. Benzene was quantified in VG but not in PG or the 30/70 PG/VG mixtures. However, benzene concentration increased in all tested mixtures upon the addition of nicotine benzoate salt. Interestingly, benzene was emitted at the highest concentration when BA was added to PG. However, lower concentrations were found in the 30/70 PG/VG and VG mixtures with BA. Both VG and BA are sources of benzene. Enhanced emissions, however, are mostly noticeable when BA is mixed with PG and not VG.

A Quick Method for the Determination of the Fraction of Freebase Nicotine in Electronic Cigarettes.

Recently, many electronic cigarettes (ECIGs) manufacturers have begun offering e-liquids, known as "nicotine salts". These salts that have started gaining big popularity among users can be formed by adding weak acid to e-liquid mixtures consisting of propylene glycol (PG), vegetable glycerin (VG), flavors, and nicotine. The latter can exist in two forms: monoprotonated (mp) and freebase (fb) based on the pH of the matrix. Over the years, the determination of the fraction of fb was found important to policymakers as the prevalence of this form in ECIGs has been associated with the harshness sensory of inhalable aerosols. Liquid-liquid extraction (LLE), 1H NMR, and Henderson-Hasselback have been developed to deduce the fraction of fb; however, these methods were found to be time-consuming and have shown some challenges mainly due to the presence of a non-aqueous matrix consisting of PG and VG. This paper presents a quick non-aqueous pH measurement-based method that allows a quick determination of the fraction fb by just measuring the pH and the dielectric constant of the e-liquid. Then, by inputting these values into an established mathematical relationship, the fraction fb can be deduced. The relationship between pH, dielectric constant, and fb relies on knowing the values of the acidity dissociation constants of nicotine, which were determined for the first time in various PG/VG mixtures using a non-aqueous potentiometric titration. To validate the proposed method, the fraction fb was determined for commercials and lab-made nicotine salts utilizing the pH and LLE methods. The variation between the two methods was (<8.0%) for commercial e-liquids and lab-made nicotine salts containing lactic acid and salicylic acid. A larger discrepancy of up to 22% was observed for lab-made nicotine salts containing benzoic acid, which can be attributed to the stronger affinity of benzoic acid to toluene in the LLE method.

Quantifying PG : VG ratio and nicotine content in commercially available e-liquids using handheld Raman spectroscopy.

Electronic cigarettes are a popular nicotine consumption product that have risen in popularity as an alternative to cigarettes. However, their recent meteoric rise in market size and various controversies have resulted in the analyses of e-liquid ingredients to be focused on powerful laboratory-based slow methods such as chromatography and mass spectrometry. Here we present a complementary technology based on Raman spectroscopy combined with chemometrics as a fast, inexpensive, and highly portable screening tool to detect and quantify the propylene glycol : glycerol (PG : VG) ratio and nicotine content of e-cigarette liquids. Through this, the PG : VG ratio of 20 out of 23 commercial samples was quantified to within 3% of their stated value, while nicotine was successfully quantified to within 1 mg g-1 for 16 out of 23 samples without the need for accurate knowledge of flavonoid composition. High linearity was also achieved when flavours were kept constant. Finally, the limitations of Raman spectroscopy are discussed, and potential solutions are suggested.

An in vitro evaluation of e-vapor products: The contributions of chemical adulteration, concentration, and device power.

Homemade e-liquids and power-adjustable vaping devices may carry higher risks than commercial formulations and fixed-power devices. This study used human macrophage-like and bronchial epithelial (NHBE) cell cultures to investigate toxicity of homemade e-liquids containing propylene glycol and vegetable glycerin (PG/VG), nicotine, vitamin E acetate (VEA), medium-chain fatty acids (MCFAs), phytol, and cannabidiol (CBD). SmallAir™ organotypic epithelial cultures were exposed to aerosols generated at different power settings (10-50 W). Carbonyl levels were measured, and endpoints reflecting epithelial function (ciliary beating frequency [CBF]), integrity (transepithelial electrical resistance [TEER]), and structure (histology) were investigated. Treatment with nicotine or VEA alone or with PG/VG did not impact cell viability. CBD, phytol, and lauric acid caused cytotoxicity in both culture systems and increased lipid-laden macrophages. Exposure of SmallAir™ organotypic cultures to CBD-containing aerosols resulted in tissue injury and loss of CBF and TEER, while PG/VG alone or with nicotine or VEA did not. Aerosols generated with higher power settings had higher carbonyl concentrations. In conclusion, the presence and concentration of certain chemicals and device power may induce cytotoxicity in vitro. These results raise concerns that power-adjustable devices may generate toxic compounds and suggest that toxicity assessments should be conducted for both e-liquid formulations and their aerosols.

Two Fast GC-MS Methods for the Measurement of Nicotine, Propylene Glycol, Vegetable Glycol, Ethylmaltol, Diacetyl, and Acetylpropionyl in Refill Liquids for E-Cigarettes.

The use of e-cigarettes (ECs) has become increasingly popular worldwide, even though scientific results have not established their safety. Diacetyl (DA) and acetylpropionyl (AP), which can be present in ECs, are linked with lung diseases. Ethyl maltol (EM)-the most commonly used flavoring agent-can be present in toxic concentrations. Until now, there is no methodology for the determination of nicotine, propylene glycol (PG), vegetable glycerin (VG), EM, DA, and acetylpropionyl in e-liquids that can be used as a quality control procedure. Herein, gas chromatography coupled with mass spectrometry (GC-MS) was applied for the development of analytical methodologies for these substances. Two GC-MS methodologies were developed and fully validated, fulfilling the standards for the integration in a routine quality control procedure by manufacturers. As proof of applicability, the methodology was applied for the analysis of several e-liquids. Differences were observed between the labeled and the experimental levels of PG, VG, and nicotine. Three samples contained EM at higher concentrations compared to the other samples, while only one contained DA. These validated methodologies can be used for the quality control analysis of EC liquid samples regarding nicotine, PG, and VG amounts, as well as for the measurement of the EM.

A Wide Range of Flavoring-Carrier Fluid Adducts Form in E-Cigarette Liquids.

A range of flavoring molecules are used in electronic cigarette liquids (e-liquids), some of which have been shown to form cyclic acetal adducts with e-liquid solvent components propylene glycol (PG) and vegetable glycerine (VG). The objective of this study was to identify the range of flavoring molecules which form adducts in e-liquid products. Common e-liquid flavoring molecules (N = 36) from a range of chemical class groups were exposed to PG, VG, or methanol and analyzed by GC-MS over a time frame of 4 weeks to identify possible reaction products. Adduct formation was observed, with 14 of the flavoring molecules reacting with methanol, 10 reacting with PG, and 10 reacting with VG. Furfural PG and VG acetals, valeraldehyde PG and VG acetals, veretraldehyde PG and VG acetals, p-anisaldehyde PG and VG acetals, and piperonal VG acetal were confirmed for the first time. Adducts formed by reaction with ketone-containing flavoring molecules were also observed for the first time. The presence of these acetals was confirmed in 32% of commercial e-liquid products analyzed (N = 142). This study has established a range of flavoring molecules which are able to react with solvent components PG and VG in e-liquids under standard storage conditions. These newly identified adducts need to be further assessed to determine their toxicological safety.

Inhalation toxicity of thermal transformation products formed from e-cigarette vehicle liquid using an in vitro lung model exposed at the Air-Liquid Interface.

The increasing use of electronic nicotine delivery systems (ENDS), also known as e-cigarettes, has raised serious public health concerns, particularly regarding certain vaping product additives. The solvent carrier liquid, which consists of a mixture of propylene glycol (PG) and vegetable glycerine (VG), representing the main constituents of e-liquid formulations, have in contrast received little attention in health evaluations due to their apparent harmlessness when ingested; however, they can develop into potential lung hazards when heated, aerosolised and inhaled from ENDS with a user-defined heating profile. To assess the acute toxicity of the respirable aerosol, an effect-based in vitro testing strategy was applied in dependence of the heating power settings in ENDS. Human alveolar epithelial cells (A549) were exposed to vaping aerosol at the air-liquid interface (ALI), flanked by targeted chemical analyses of reactive carbonyl species. An exploratory, semi-automated in vitro exposure system provided evidence of a positive connection between vaporisation temperature and aerosol toxicity. Thermochemical transformation of the solvent leads to the formation of both cytotoxic and genotoxic substances that may disrupt lung homeostasis. Toxicity is therefore not limited to the presence of additives, as most harmful volatiles originate from the solvent itself, ultimately related to the device power output.

Evidence for the coupling of refill liquids content and new particle formation in electronic cigarette vapors.

The size and chemical content of particles in electronic cigarette vapors (e-vapors) dictate their fate in the human body. Understanding how particles in e-vapors are formed and their size is critical to identifying and mitigating the adverse consequences of vaping. Thermal decomposition and reactions of the refill liquid (e-liquid) components play a key role in new particles formation. Here we report the evolution of particle number concentration in e-vapors over time for variable mixtures of refill e-liquids and operating conditions. Particle with aerodynamic diameter < 300 nm accounted for up to 17% (or 780 µg/m3) of e-vapors particles. Two events of increasing particle number concentration were observed, 2-3 s after puff completion and a second 4-5 s later. The intensity of each event varied by the abundance of propylene glycol, glycerol, and flavorings in e-liquids. Propylene glycol and glycerol were associated with the first event. Flavorings containing aromatic and aliphatic unsaturated functional groups were strongly associated with the second event and to a lesser extent with the first one. The results indicate that particles in e-vapors may be formed through the heteromolecular condensation of propylene glycol, glycerol, and flavorings, including both parent chemicals and/or their thermal decomposition products.

A Lipid-Based In Situ-Forming Hexagonal Phase for Prolonged Retention and Drug Release in the Breast Tissue.

In this study, the addition of monoolein to phosphatidylcholine (PC), tricaprylin, and propylene glycol (PG) mixtures was studied to produce fluid precursor formulations (FIPs) that could transform into hexagonal phase (resistant to aqueous dilution) in vitro and in vivo. The overall goal was to obtain FIPs that could incorporate chemopreventive drugs for subcutaneous administration in the mammary tissue to inhibit the development and/or recurrence of breast cancer. Increasing PG content reduced FIP viscosity up to ~ 2.5-fold, while increases in PC (over monoolein) increased the formation of emulsified systems. The hexagonal phase was observed at 20% of water and higher, with the minimum amount of water necessary for this formation increasing with PG content. The selected FIP formed a depot in vivo after ~ 24 h of administration; its structure was compatible with the hexagonal phase and it remained in the mammary tissue for at least 30 days, prolonging the permanence of a fluorescent probe. In vitro, the release of the synthetic retinoid fenretinide was slow, with ~ 9% of the drug released in 72 h. Consistent with this slow release, fenretinide IC50 in breast cancer cells was ~ 100-fold higher in the selected FIP compared to its solution. The FIP reduced cell migration and presented higher cytotoxicity towards tumor compared to non-tumor cells. Given the limited number of options for pharmacological prevention of breast cancer development and recurrences, this formulation could potentially find applicability to reduce the frequency of administration and improve local concentrations of chemopreventive drugs.

Kinetics of Aldehyde Flavorant-Acetal Formation in E-Liquids with Different E-Cigarette Solvents and Common Additives Studied by 1H NMR Spectroscopy.

Flavorants, nicotine, and organic acids are common additives found in the e-liquid carrier solvent, propylene glycol (PG) and/or glycerol (GL), at various concentrations. Some of the most concentrated and prevalent flavorants in e-liquids include trans-cinnamaldehyde, vanillin, and benzaldehyde. Aldehyde flavorants have been shown to react with PG and GL to form flavorant-PG and -GL acetals that have unique toxicity properties in e-liquids before aerosolization. However, there is still much that remains unknown about the effects of different e-cigarette solvents, water, nicotine, and organic acids on the rate of acetalization in e-liquids. We used 1H NMR spectroscopy to determine the first-order initial rate constant, half-life, and % acetal formed at equilibrium for flavorant-acetal formation in simulated e-liquids. Herein, we report that acetalization generally occurs at a faster rate and produces greater yields in e-liquids with higher ratios of GL (relative to PG). trans-Cinnamaldehyde acetals formed the fastest in 100% PG-simulated e-liquids, followed by benzaldehyde and vanillin based on their half-lives and rate constants. The acetal yield was greatest for benzaldehyde in PG e-liquids, followed by trans-cinnamaldehyde and vanillin. Acetalization in PG e-liquids containing aldehyde flavorants was inhibited by water and nicotine but catalyzed by benzoic acid. Flavorant-PG acetal formation was generally delayed in the presence of nicotine, even if benzoic acid was present at 2-, 4-, or 10-fold the nicotine concentration, as compared to the PG e-liquids with 2.5 mg/mL flavorant. Thus, commercial e-liquids with aldehyde flavorants containing a higher GL ratio (relative to PG), little water, no nicotine, nicotine with excess organic acids, or organic acids without nicotine would undergo acetalization the fastest and with the highest yield. Many commercial e-liquids must therefore contain significant amounts of flavorant acetals.

Propylene Glycol Caprylate-Based Nanoemulsion Formulation of Plumbagin: Development and Characterization of Anticancer Activity.

Plumbagin, a bioactive naphthoquinone, has demonstrated potent antitumor potential. However, plumbagin is a sparingly water-soluble compound; therefore, clinical translation requires and will be facilitated by the development of a new pharmaceutical formulation. We have generated an oil-in-water nanoemulsion formulation of plumbagin using a low-energy spontaneous emulsification process with propylene glycol caprylate (Capryol 90) as an oil phase and Labrasol/Kolliphor RH40 as surfactant and cosurfactant excipients. Formulation studies using Capryol 90/Labrasol/Kolliphor RH40 components, based on pseudoternary diagram and analysis of particle size distribution and polydispersity determined by dynamic light scattering (DLS), identified an optimized composition of excipients for nanoparticle formulation. The nanoemulsion loaded with plumbagin as an active pharmaceutical ingredient had an average hydrodynamic diameter of 30.9 nm with narrow polydispersity. The nanoemulsion exhibited long-term stability, as well as good retention of particle size in simulated physiological environments. Furthermore, plumbagin-loaded nanoemulsion showed an augmented cytotoxicity against prostate cancer cells PTEN-P2 in comparison to free drug. In conclusion, we generated a formulation of plumbagin with high loading drug capacity, robust stability, and scalable production. Novel Capryol 90-based nanoemulsion formulation of plumbagin demonstrated antiproliferative activity against prostate cancer cells, warranting thus further pharmaceutical development.

Quantification and cytotoxicity of degradation products (chloropropanols) in sucralose containing e-liquids with propylene glycol and glycerol as base.

Electronic cigarettes (e-cigarettes) have gained increasing popularity in recent years, mostly because they are supposed to be less harmful than regular cigarettes. Therefore, it is highly imperative to investigate possible noxious effects to protect the consumers. E-liquids consist of propylene glycol, glycerol, aroma compounds and sweeteners. One of these sweeteners is a chlorinated version of sucrose, namely sucralose. The aim of this work was to investigate degradation products of sucralose in the presence of propylene glycol and glycerol at different temperatures of commercially available e-cigarettes. Chemical analysis and biological tests were simultaneously performed on e-liquid aerosol condensates. The results of the chemical analysis, which was executed by employing GC-MS/GC-FID, demonstrated high amounts of various chloropropanols. The most abundant one is extremely toxic, namely 3-chloropropane-1,2-diol, which can be detected at concentrations ranging up to 10,000 mg/kg. Furthermore, a cytotoxicity investigation of the condensates was performed on HUVEC/Tert2 cells in which metabolic activity was determined by means of resazurin assay. The cellular metabolic activity significantly decreased by treatment with e-liquid aerosol condensate. Due to the results of this study, we advise against the use of sucralose as sweetener in e-liquids.

Impact of e-Liquid Composition, Coil Temperature, and Puff Topography on the Aerosol Chemistry of Electronic Cigarettes.

E-cigarette aerosol is a complex mixture of gases and particles with a composition that is dependent on the e-liquid formulation, puffing regimen, and device operational parameters. This work investigated mainstream aerosols from a third generation device, as a function of coil temperature (315-510 °F, or 157-266 °C), puff duration (2-4 s), and the ratio of propylene glycol (PG) to vegetable glycerin (VG) in e-liquid (100:0-0:100). Targeted and untargeted analyses using liquid chromatography high-resolution mass spectrometry, gas chromatography, in situ chemical ionization mass spectrometry, and gravimetry were used for chemical characterizations. PG and VG were found to be the major constituents (>99%) in both phases of the aerosol. Most e-cigarette components were observed to be volatile or semivolatile under the conditions tested. PG was found almost entirely in the gas phase, while VG had a sizable particle component. Nicotine was only observed in the particle phase. The production of aerosol mass and carbonyl degradation products dramatically increased with higher coil temperature and puff duration, but decreased with increasing VG fraction in the e-liquid. An exception is acrolein, which increased with increasing VG. The formation of carbonyls was dominated by the heat-induced dehydration mechanism in the temperature range studied, yet radical reactions also played an important role. The findings from this study identified open questions regarding both pathways. The vaping process consumed PG significantly faster than VG under all tested conditions, suggesting that e-liquids become more enriched in VG and the exposure to acrolein significantly increases as vaping continues. It can be estimated that a 30:70 initial ratio of PG:VG in the e-liquid becomes almost entirely VG when 60-70% of e-liquid remains during the vaping process at 375 °F (191 °C). This work underscores the need for further research on the puffing lifecycle of e-cigarettes.

Skin-specific knockdown of hyaluronan in mice by an optimized topical 4-methylumbelliferone formulation.

Hyaluronan (HA) is abundant in the skin; while HA can be synthesized by the synthases (HAS1-3), HAS2 is the leading contributor. Dysregulation and accumulation of HA is implicated in the pathogenesis of diseases such as keloid scarring, lymphedema and metastatic melanoma. To understand how HA synthesis contributes to skin physiology, and pathologic and fibrotic disorders, we propose the development of skin-specific HA inhibition model, which tests an optimal delivery system of topical 4-methylumbelliferone (4-MU). A design-of-experiments (DOE) approach was employed to develop an optimal 4-MU skin-delivery formulation comprising propylene glycol, ethanol, and water, topically applied to dorsal skin in male and female C57BL/6J wildtype mice to determine the effect on HAS gene expression and HA inhibition. Serum and skin samples were analyzed for HA content along with analysis of expression of HAS1-3, hyaluronidases (HYAL 1-2), and KIAA1199. Using results from DOE and response surface methodology with genetic algorithm optimization, we developed an optimal topical 4-MU formulation to result in ∼70% reduction of HA in dorsal skin, with validation demonstrating ∼50% reduction in HA in dorsal skin. 4-MU topical application resulted in significant decrease in skin HAS2 expression in female mice only. Histology showed thicker dermis in male mice, whereas female mice had thinner dermal layer with more adiposity; and staining for HA-binding protein showed that topical 4-MU resulted in breakdown in HA. Our data suggest a topical 4-MU formulation-based dermal HA inhibition model that would enable elucidating the skin-specific effects of HA in normal and pathologic states.