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1.
Sci Total Environ ; 720: 137604, 2020 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-32143054

RESUMO

In this study, we report an inexpensive, green, and one-pot synthesis method for highly fluorescent carbon quantum dots (CQDs) using mango (Mangifera indica: M. indica) leaves to develop an efficient sensing platform for metal ions. The CQDs synthesized from M. indica leaves via pyrolysis treatment at 300 °C for 3 h were characterized by various spectroscopic and electron microscopy techniques for their structural, morphological, and optical properties. Accordingly, the synthesized CQDs showed an absorption peak at 213 nm to confirm the p-p* transition of the carbon core state, while the CQD particles were spherical with a size less than 10 nm. The prepared CQDs showed excellent fluorescent properties with blue emission spectra (around 525 nm) upon excitation at 435 nm. The synthesized CQDs had the prodigious sensing potential to detect Fe2+ ions in water with a limit of detection of 0.62 ppm. Additionally, their sensing capability was tested using a real sample (e.g., Livogen tablet). Moreover, the synthesized CQDs showed substantial stability over a long period (three months). Thus, this study provides an inexpensive and facile method for CQD-based sensing of Fe2+ ions with a photoluminescence quenching mechanism.

2.
Nutrients ; 12(3)2020 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-32131519

RESUMO

Chronic exposure to cisplatin is associated with irreversible kidney impairment. In this present study, we explored the protective effects of 3-dehydroxyceanothetric acid 2-methyl ester (3DC2ME) isolated from roots of jujube (Ziziphus jujuba, Rhamnaceae) against cisplatin-induced damage in vitro. In kidney epithelial LLC-PK1 cells, western blotting and staining with specific autophagy epifluorescent dye CytoID were used to determine the molecular pathways involving autophagy. Treatment with 3DC2ME reduced the increased Cyto-ID-stained autophagic vesicles and reversed the protein expressions of 5' AMP-activated protein kinase subunit ß-1 (AMPK)/mammalian target of rapamycin (mTOR)-dependent signaling pathway in cisplatin-induced cell death. Additionally, treatment with autophagy inhibitor 3-methyladenine (3-MA) and with or without 3DC2ME attenuated the cisplatin-induced apoptosis. Although further research is necessary to substantiate the effects, we evaluated the potential mechanism of action of 3DC2ME as an adjuvant for cancer patients.

3.
J Nat Prod ; 83(3): 684-692, 2020 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-32118424

RESUMO

Opuntia humifusa, known as the eastern prickly pear cactus and locally called "Cheonnyuncho" in Korea, is cultivated widely on Jeju Island, Korea. Phytochemical analysis of the methanolic extract of the cladodes of O. humifusa, for which previous research is relatively limited, was performed under the guidance of LC/MS-based analysis. As a result, one new megastigmane (1) and four new megastigmane glucosides (2-5) were isolated along with 18 known compounds (6-23). The structures of the new compounds were established by 1D and 2D NMR and HRESIMS, and their absolute configurations were established by chemical reactions, quantum chemical electronic circular dichroism calculations, and DP4+ analysis using the gauge-including atomic orbital NMR chemical shift calculations as well as the application of Snatzke's method. The isolated compounds (1-23) were tested for NO production inhibition in lipopolysaccharide (LPS)-induced RAW 264.7 cells to investigate their anti-inflammatory effects. Compounds 10 and 11 exhibited significant inhibitory effects on LPS-induced NO production in a dose-dependent manner. The potential mechanistic pathway of 10 and 11 was also investigated using Western blotting, indicating that compounds 10 and 11 inhibit NO through iNOS expression.

4.
J Colloid Interface Sci ; 570: 99-108, 2020 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-32145654

RESUMO

In this research, efforts were put to demonstrate synergistic interactions between bioenergy generation and wastewater treatment. The extent of such synergistic effect was assessed against wastewater effluents released from the beverage industry through the operation of a membrane-less truncated conical (TC) microbial fuel cell (MFC). A graphite-based reactor was operated for five cycles in batch mode using beverage industry wastewater as an organic substrate. Maximum bioelectricity produced on the fifth operating cycle corresponded to a voltage of 338 mV and a power of 1.14 mW at 100 Ω. The MFC recorded a higher substrate degradation rate (0.84 kg of chemical oxygen demand [COD]/m3-day) accompanied by the development of an electroactive biofilm and polarization behavior (e.g., a reduction in internal resistance from 323 Ω to 197 Ω over five operation cycles). Cyclic voltammetry showed a maximum performance of the biofilm during the fifth cycle (through its enrichment) as interpreted by oxidation and reduction currents of 2.48 and -2.21 mA, respectively. The performance of the proposed MFC was superior to other designs reported previously in both effluent treatment and bioenergy generation. A maximum treatment efficiency of 84.4% (in 385 h) was seen at an organic load (COD) of 3500 mg/L with the specific power yield (0.504 W/Kg of substrate (COD) removal) and volumetric power yield (15.03 W/m3). Our experimental studies support that the proposed system could be upscaled to realize the commercial operation.

5.
J Colloid Interface Sci ; 570: 411-422, 2020 Mar 03.
Artigo em Inglês | MEDLINE | ID: mdl-32199191

RESUMO

HYPOTHESIS: Oil spills stemming from supertankers, drilling, and natural events represent a serious problem worldwide due to the potential harms to marine ecosystems and aquatic life. To date, various functional absorbents have been developed to treat spilled oil. Among them, carbon nanotube (CNT)-based aerogels and sponges gained attention due to superior performance in uptake and recovery of various types of oil and organic solvents. CNT aerogel/sponge absorbents are demonstrated for a multitude of merits such as: rapid superhydrophobic/superoleophilic absorption (water contact angle > 150°), high capacity (≥100 mg g-1), large surface area (300-400 m2 g-1)), enhanced strength and flexibility (>95% volume reduction and restoration of pristine morphology at <0.25 MPa stress), mesoporous characteristics with high pore density (pore diameter = 80 nm and >99% porosity), recyclability, and easy surface modification. EXPERIMENTS: This review compares CNT sponge-based absorbents with conventional techniques for remediation/recovery of spilled oil. Typically, synthesis of CNT sponges is performed using chemical vapor deposition (CVD) approach in the presence of a catalyst or using sacrificial removal of template. This work summarizes recent progress in strategies for oil-spill treatment based on CNT sponge techniques. The performance of CNT sponges for oil spill removal was evaluated in terms of their adsorption capacity, compressive stressability, and desorption methods (e.g., heat treatment, burning, or squeezing). FINDINGS: CNT sponges were observed to have high performance for removal of oil spills in terms of key performance metrics. This review offers valuable insights into the current state of CNT-mediated oil-spill cleanup technologies and guidance for future research at the same time. This literature survey would help the stakeholders (researchers, scientists, entrepreneurs, and commercial houses) pursue contamination-free water.

6.
Chembiochem ; 2020 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-32212411

RESUMO

Xylaria species are prolific natural product producers. Here, we report the characterization of a new glycosylated incisterol derivative, called xyloneside A ( 1 ) and two known lignans ( 2 and 3 ) from the ascomycetous Xylaria sp. FB. The structure of xyloneside A ( 1 ) was determined by 1D and 2D nuclear magnetic resonance spectra, high-resolution electrospray ionization mass spectrometry and electronic circular dichroism measurements. Xyloneside A ( 1 ) is composed of a 1,2,3,4,5,10,19-heptanorergosterane skeleton and a ß- D-mannopyranose moiety. This is the first report of an incisterol derivative from an Ascomycete. The biological effects of the isolated metabolites on cytotoxicity, autophagy, cell-migration, and angiogenesis were evaluated.

7.
Adv Colloid Interface Sci ; 277: 102108, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32028075

RESUMO

Recently, as a new sub-family of porous coordination polymers (PCPs), porphyrinic-MOFs (Porph-MOFs) with biomimetic features have been developed using porphyrin macrocycles as ligands and/or pillared linkers. The control over the coordination of the porphyrin ligand and its derivatives however remains a challenge for engineering new tunable Porph-MOF frameworks by self-assembly methods. The key challenges exist in the following respects: (i) collapse of the large open pores of Porph-MOFs during synthesis, (ii) deactivation of unsaturated metal-sites (UMCs) by axial coordination, and (iii) the tendency of both coordinated moieties (at peripheral meso- and beta-carbon sites) and the N4-pyridine core to coordinate with metal cations. In this respect, this review covers the advances in the design of Porph-MOFs relative to their counterpart covalent organic frameworks (Porph-COFs). The potential utility of custom-designed porphyrin/metalloporphyrins ligands is highlighted. Synthesis strategies of Porph-MOFs are also illustrated with modular design of hybrid guest@host composites (either Porph@MOFs or guest@Porph-MOFs) with exceptional topologies and stability. This review summarizes the synergistic benefits of coordinated porphyrin ligands and functional guest molecules in Porph-MOF composites for enhanced catalytic performance in various redox applications. This review shed lights on the engineering of new tunable hetero-metals open active sites within (metallo)porphyrin-MOFs as out-of-the-box platforms for enhanced catalytic processes in chemical and biological media.

8.
Biosens Bioelectron ; 153: 112046, 2020 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-32056661

RESUMO

The continuous need for food resources by humans and animals has led to extensive use of antibiotics as essential medicines. However, we are now facing serious environmental contamination of antibiotics and the associated health concerns because of their uncontrolled disposal. In an effort to resolve this problem, nanostructured electrochemical platforms comprising of diverse materials (e.g., carbonaceous nanoparticles, metal nanoparticles, magnetic nanoparticles, metal-organic frameworks, and quantum dots) have been proposed to detect antibiotic residues. Despite the significant progress achieved in such research fields, further efforts are still required to develop advanced electrochemical sensors with the aid of multi-functional nanomaterials and to ensure efficient portability for such sensors with enhaced communicability. Therefore, the present review summarizes an in-depth evaluation of the nanostructured electrochemical sensing system for antibiotics residues in diverse matrices (e.g., human fluids, environmental media, and food/beverages samples). The present review begins with a brief introduction to antibiotics followed by a survey on the existing electroanalytical techniques to highlight the significance of nanomaterial-based electrochemical sensing techniques for antibiotics in diverse matrices. Finally, the review provides an outlook on the future concepts of this research field to help upgrade the sensing techniques for antibiotics.

9.
Sci Total Environ ; 715: 136990, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-32014787

RESUMO

Science of the Total Environment recently discussed how open access and predatory journals affect the flow of scientific knowledge in an unfortunate way. Now, South Korea's Ministry of Education is intervening to establish a system that will help its researchers avoid the growing global number of fake conferences of low academic and scientific merit. Here, we discuss solutions to this problem with respect to what is needed. Particularly, a list similar to that of Beall's for predatory conferences, without restricting researchers' academic freedom.

10.
Artigo em Inglês | MEDLINE | ID: mdl-32041396

RESUMO

Recent research endeavors have established metal-organic frameworks (MOFs) as suitable platforms for the adsorptive removal of various environmental pollutants. In this regard, the sorptive performances of four MOFs (MOF-199, UiO-66, UiO-66-NH2, and Co-CUK-1) were investigated against two gaseous aliphatic ketones (methyl ethyl ketone (MEK) and methyl isobutyl ketone (MiBK)) at a low partial pressure (0.1 Pa). Activated carbon was utilized as a reference commercial sorbent. The 10% breakthrough volume (BTV10) values for MEK decreased in the following order: MOF-199 (4772 L atm g-1) > activated carbon (224 L atm g-1) > UiO-66-NH2 (106 L atm g-1) > UiO-66 (53 L atm g-1) > Co-CUK-1 (16 L atm g-1). In case of MiBK, the relative ordering in BTV10 was consistently maintained while showing noticeable increases in its magnitude: MOF-199 (7659 L atm g-1) > activated carbon (816 L atm g-1) > UiO-66-NH2 (304 L atm g-1) > UiO-66 (150 L atm g-1) > Co-CUK-1 (31 L atm g-1). The superiority of MOF-199 was confirmed toward the adsorptive removal of gaseous aliphatic ketones. For a binary mixture of ketones, the BTV10 values of MOF-199 were reduced considerably for MEK and MiBK (in comparison to single component sorption) such as 1579 and 3969 L atm g-1, respectively, reflecting competitive inhibition of the adsorption process. Theoretical simulations based on density functional theory (DFT) elucidated the involvement of highly favorable coordination between the carbonyl group present in ketone molecules and the uncoordinated Cu(II) sites in the MOF-199 structure (Lewis acidic centers). Interestingly, MOF-199 maintained appreciable performance toward the mixture of ketones up to 5 cycles to support its practical merit.

11.
Chemosphere ; 248: 126043, 2020 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-32007768

RESUMO

A Pt catalyst supported on activated carbon (Pt/AC) was used for an environmentally friendly thermal treatment of food waste under an inert atmosphere (i.e., pyrolysis). This catalyst influenced the amounts of condensable hydrocarbons and noncondensable gases but not that of the solid remaining after the pyrolysis; in particular, it contributed to shifting the carbon distribution from the condensable hydrocarbons to the noncondensable gases for the food waste pyrolysis. Moreover, its use suppressed the generation of harmful chemical compounds, especially at high temperatures. For example, a Pt/AC-catalyzed pyrolysis at 700 °C produced about 4 times fewer benzene derivatives than the same treatment without a catalyst; this probably occurred because the Pt sites catalyzed the decyclization reaction and/or the free radical mechanism, which is dominant in the thermal cracking of carbon-containing feedstock. This study suggests that a Pt/AC-catalyzed pyrolysis would be a more environmentally benign food waste treatment method.

12.
Chemosphere ; 248: 125971, 2020 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-32035380

RESUMO

As reported in Chemosphere by Colles et al. (2020), there are multiple pathways for human exposure to poly- and perfluoroalkyl substances (PFAS). Now, a new chemical formation of C-F bonds in drug delivery lead to concerns for human exposure as these inert chemical formations are resistance to metabolic degradation and excretion.

13.
Environ Res ; 182: 109043, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31896470

RESUMO

Various materials have been investigated for the adsorptive removal of volatile organic compounds (VOCs, such as benzene). However, most materials proposed for the adsorptive removal of gaseous benzene (and other VOCs) perform relatively poorly (e.g., an impractically low-service 10% breakthrough volume [BTV10] at < 100 ppm). The adsorbent uptake rate (mg g-1 min-1) can also be assessed as a function of the gas-stream flow rate (or space velocity). The main aim of this study is to explore the effect of two different gas-stream supply modes - stopped flow (at a fixed stream flow rate of 330 mL atm min-1) vs. continuous flow (a variable-stream flow rate of 100, 200, or 330 mL atm min-1) on the adsorption metrics of gaseous benzene on 5 mg of two types of - II covalent organic polymers (COPs: CBAP-1 [DETA], CD; or CBAP-1 [EDA], CE). The sorbent tube outlet stream was sampled by two respective sampling methods (i.e., a large-volume injector [LVI] for stopped flow vs. syringe injection [SI] for continuous flow) for sample quantitation by gas chromatography flame-ionization detection (GC-FID). The observed BTV10 values in the two sampling modes were similar when tested using 10 ppm benzene, irrespective of sorbents: 56/60 (CD) vs. 620/624 L atm g-1 (CE). BTV10 values increased systematically with decreasing stream-flow rates to reflect the importance of space velocity in adsorptive removal of benzene. The overall assessment of adsorption performance between stopped flow (LVI) and continuous flow (SI) revealed that the performance of the adsorbent is independent of flow mode (e.g., when performance was compared at flow rate of 330 mL min-1).

14.
Bioorg Chem ; 95: 103554, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31911304

RESUMO

Two-spotted cricket Gryllus bimaculatus is one of many cricket species, and it is widely used as a food source for insectivorous animals. Moreover, this species is one of the edible insects approved by the Korea Food and Drug Administration (KFDA). (±)-Kituramides A (1) and B (2), which are pairs of novel enantiomeric dopamine dimers possessing a formamide group, were isolated from the two-spotted cricket, together with four other known biosynthetically related compounds (3-6). The chemical structures of 1 and 2 were elucidated using a combination of 1D and 2D NMR spectroscopic experiments and HR-ESIMS data. Compounds 1 and 2 were identified as racemic mixtures; the enantiomers (+)-1/2 and (-)-1/2 were successfully separated by utilizing a chiral HPLC column. The absolute configurations of (±)-1 and (±)-2 were unambiguously delineated by the application of quantum chemical ECD calculations. Further, these insect-derived substances were evaluated to understand their effects on cytokine expression in adipocytes. Treatment with (-)-1, (+)-2, and (-)-2 during adipocyte differentiation significantly promoted the expression of Leptin and IL-6, which resembles the actions of dopamine.

15.
Arch Pharm Res ; 43(2): 214-223, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31993970

RESUMO

Gymnopilus junonius (Fr.) P. D. Orton (Cortinariaceae) is a hallucinogenic mushroom, a well-known poisonous mushroom that is widely known as "big laughter mushroom" because it causes excessive laughter in those who consume it. Chemical investigation of G. junonius fruiting bodies was performed, resulting in the isolation and structural identification of three sesquiterpenes (1-3), including a new trichothecene sesquiterpene (2) and a new tremulane sesquiterpene (3). Compound 1 was identified from G. junonius for the first time. The chemical structures of the new compounds were established by detailed analysis of 1D and 2D (1H-1H correlated spectroscopy [COSY], heteronuclear single quantum coherence [HSQC], and heteronuclear multiple-bond coherence [HMBC]) nuclear magnetic resonance (NMR) spectra, and high-resolution mass spectrometry (HRMS). In particular, the absolute configurations of compounds 2 and 3 were unambiguously determined by quantum chemical electronic circular dichroism (ECD) calculations. The isolated compounds (1-3) were evaluated for their cytotoxic effects on human lung and prostate cancer cell lines where trichothecene sesquiterpenes (1 and 2) showed remarkable cytotoxicity similar to that of the control drug, i.e., doxorubicin. Our findings provide experimental evidence suggesting the potential anti-cancer effects of trichothecene sesquiterpenes from a poisonous mushroom.

16.
Macromol Rapid Commun ; 41(4): e1900514, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31958190

RESUMO

Despite their capability, sub-10 nm periodic nano-patterns formed by strongly segregating block copolymer (BCP) thin films cannot be easily oriented perpendicular to the substrate due to the huge surface energy differences of the constituent blocks. To produce perpendicular nano-patterns, the interfacial energies of both the substrate and free interfaces should be controlled precisely to induce non-preferential wetting. Unfortunately, high-performance surface modification layers are challenging to design, and different kinds of surface modification methods must be devised respectively for each neutral layer and top coat. Furthermore, conventional approaches, largely based on spin-coating processes, are highly prone to defect formation and may readily cause dewetting at sub-10 nm thickness. To date, these obstacles have hampered the development of high-fidelity, sub-5 nm BCP patterns. Herein, an all-vapor phase deposition approach initiated chemical vapor deposition is demonstrated to form 9-nm-thick, uniform neutral bottom layer and top coat with exquisite control of composition and thickness. These layers are employed in BCP films to produce perpendicular cylinders with a diameter of ≈4 nm that propagate throughout a BCP thickness of up to ≈60 nm, corresponding to five natural domain spacings of the BCP. Such a robust approach will serve as an advancement for the reliable generation of sub-10 nm nano-patterns.

17.
J Nat Prod ; 83(2): 354-361, 2020 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-31990198

RESUMO

The absolute configuration and corrected NMR assignment of 17-hydroxycyclooctatin isolated from Streptomyces sp. M56 recovered from a nest of South African Macrotermes natalensis termites are reported. 17-Hydroxycyclooctatin is a unique tricyclic diterpene (C20) consisting of a fused 5-8-5 ring system, and in this study, its structure was unambiguously determined by a combination of HR-ESIMS and 1D and 2D NMR spectroscopic experiments to produce corrected NMR assignments. The absolute configuration of 17-hydroxycyclooctatin is reported for the first time in the current study using chemical reactions and quantum chemical ECD calculations. The corrected NMR assignments were verified using a gauge-including atomic orbital NMR chemical shifts calculation, followed by DP4 probability. To understand the pharmacological properties of 17-hydroxycyclooctatin, a network pharmacological approach and molecular docking analyses were used, which also predicted its effects on human breast cancer cell lines. Cytotoxicity and antiestrogenic activity of 17-hydroxycyclooctatin were determined, and it was found this compound may be an ERα antagonist.

18.
Adv Colloid Interface Sci ; 275: 102071, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31806151

RESUMO

Petroleum processing wastewater (PPW) is a complex mixture of free, soluble, and emulsive hydrocarbons that often contain heavy metals and/or solid particles. As these hazardous constituents can accumulate in human beings and the environment, exposure to the PPW can have harmful effects in various respects. The use of environmental nanotechnologies (E-Nano) is considered an attractive option to resolve the problems associated with PPW. Among different treatment technologies, E-Nano-based sorption (adsorption/absorption) and membrane filtration approaches have been proven to have outstanding efficacy in remediation of PPW pollutants. It is, however, crucial to determine the appropriate technological option (e.g., low-cost operational conditions) for the practical application of such technologies. In this review, the potential of E-Nano-based sorption and membrane technologies in the treatment of various PPW pollutants is discussed based on their performances in comparison to traditional technologies. Their suitability is evaluated further in relation to their merits/disadvantages and economic feasibility with the goal of constructing a perspective map to efficiently implement the E-Nano technologies.

19.
Environ Res ; 181: 108904, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31806286

RESUMO

In this study, the feasibility of using carbonaceous nanomaterials was explored for adsorptive removal of methylene blue (MB) and methyl orange (MO) dyes from contaminated water under dark conditions. The morphology and crystalline nature of synthesized carbonaceous nanomaterials (e.g., multi-walled carbon nanotubes [MWCNTs], activated carbon [AC], and their nanocomposite) were characterized by different microscopic and spectroscopic techniques. Furthermore, adsorption experiments were carried out by controlling several key parameters including solution pH, adsorbent dosage, dye concentration, contact time, and temperature. First, the adsorptive behavior of MWCNTs was explained with the aid of adsorption isotherms and kinetics. Thereafter, the adsorptive performance of MWCNTs was compared with those of AC and MWCNTs/AC, and the maximum adsorption capacity (mg/g) of MB/MO was in the order of MWCNTs/AC nanocomposite (232.5/196.1) > MWCNTs (185.1/106.3) > AC (161.3/78.7). The improved adsorption performance (e.g., in terms of adsorption capacity and partition coefficient) of the MWCNTs/AC nanocomposite could be attributed to the presence of more active sites on its surface. Furthermore, their reusable efficiency was in the order of MWCNTs/AC nanocomposite (90.2%), MWCNTs (81%), and AC (67%) after the first step of recovery. The performance of these adsorbents was also evaluated for real field samples. In comparison to MWCNTs and AC, the MWCNTs/AC sorbents offered excellent performance in both single and binary systems, i.e., ~99.8% and 98.7% average removal of MB and MO, respectively.

20.
Sci Total Environ ; 703: 134567, 2020 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-31751827

RESUMO

Generally, the liquid used in electronic cigarettes (E-cigarettes), which is also called E-liquid, is composed of propylene glycol (PG), vegetable glycerin (VG), and nicotine, with many other miscellaneous ingredients. E-liquid is consumed mainly in the form of aerosol via inhalation by the e-cigarette user. The amount and composition of the aerosol generated during its consumption depend on various factors. In this study, the three major constituents (PG, VG, and nicotine) of E-cigarettes were analyzed in both liquid and aerosol samples from 50 commercial products. Their concentrations in the liquid (and aerosol at 3.4 V) samples were 538 (4 6 7), 482 (4 4 9), and 8.75 mg g-1 (7.91 mg g-1), respectively. The nicotine levels in the E-liquids measured in this study were normally 1.2 times greater than those specified by the manufacturers. Furthermore, the amount of liquid consumed increased proportionally as the voltage of the E- cigarette increased. The consumption rate of VG increased as the voltage of the E-cigarette increased, whereas that of PG and nicotine decreased. The results of our study confirm that the amounts of PG and VG generated through the use of E-cigarettes are noticeably larger than those from other tobacco products (such as traditional tobaccos and heat-not-burn products), although no such trend was evident in case of nicotine.

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