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Effect of Electronic Cigarette Liquid pH on Retention of 11C-Nicotine in a Respiratory Tract Model.

Publication ,  Journal Article
Solingapuram Sai, KK; Rose, JE; Mukhin, AG
Published in: Nicotine Tob Res
June 9, 2023

INTRODUCTION: Based on our preliminary 11C-nicotine positron emission tomography (PET) imaging studies in humans, we speculated that greater deposition of nicotine in the respiratory tract from electronic cigarettes compared to combustible cigarettes could result from the alkaline pH of typical aerosol-producing electronic cigarette liquids (e-liquids). To address this hypothesis, we assessed the effect of e-liquid pH on the retention of nicotine in vitro using 11C-nicotine, PET, and a human respiratory tract model of nicotine deposition. AIMS AND METHODS: A single 2-second 35-mL puff was delivered to a human respiratory tract cast from a 2.8-Ohm cartomizer at 4.1 volts. Immediately after the puff, a 2-second 700-mL air wash-in volume was administered. E-liquids (glycerol and propylene glycol 50/50 vol/vol) containing 24 mg/mL nicotine were mixed with 11C-nicotine. Deposition (retention) of nicotine was assessed using a GE Discovery MI DR PET/CT scanner. Eight e-liquids with different pH values (range 5.3-9.6) were investigated. All experiments were performed at room temperature and at a relative humidity of 70%-80%. RESULTS: Retention of nicotine in the respiratory tract cast was pH dependent and the pH-sensitive component of the retention was well described by a sigmoid curve. In total, 50% of the maximal pH-dependent effect was observed at pH 8.0, which is close to the pKa2 of nicotine. CONCLUSIONS: The retention of nicotine in the respiratory tract conducting airways is dependent on the e-liquid pH. Lowering the e-liquid pH reduces retention of nicotine. Nonetheless, reduction of the pH below 7 has little effect, consistent with the pKa2 of protonated nicotine. IMPLICATIONS: Similar to combustible cigarettes, the retention of nicotine in the human respiratory tract from consumption of electronic cigarettes may have some health consequences and affect nicotine dependence. Here we demonstrated that the retention of nicotine in the respiratory tract is dependent on the e-liquid pH, and lowering pH reduces retention of nicotine in conducting airways of the respiratory tract. Therefore, e-cigarettes with low pH values would result in reduced respiratory tract nicotine exposure and faster delivery of nicotine to the central nervous system (CNS). The latter can be associated with e-cigarette abuse liability and the effectiveness of e-cigarettes as substitutes for combustible cigarettes.

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Published In

Nicotine Tob Res

DOI

EISSN

1469-994X

Publication Date

June 9, 2023

Volume

25

Issue

7

Start / End Page

1406 / 1410

Location

England

Related Subject Headings

  • Respiratory System
  • Public Health
  • Positron Emission Tomography Computed Tomography
  • Nicotine
  • Hydrogen-Ion Concentration
  • Humans
  • Electronic Nicotine Delivery Systems
  • Carbon Radioisotopes
  • 4206 Public health
  • 4202 Epidemiology
 

Citation

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Solingapuram Sai, K. K., Rose, J. E., & Mukhin, A. G. (2023). Effect of Electronic Cigarette Liquid pH on Retention of 11C-Nicotine in a Respiratory Tract Model. Nicotine Tob Res, 25(7), 1406–1410. https://doi.org/10.1093/ntr/ntad039
Solingapuram Sai, Kiran K., Jed E. Rose, and Alexey G. Mukhin. “Effect of Electronic Cigarette Liquid pH on Retention of 11C-Nicotine in a Respiratory Tract Model.Nicotine Tob Res 25, no. 7 (June 9, 2023): 1406–10. https://doi.org/10.1093/ntr/ntad039.
Solingapuram Sai KK, Rose JE, Mukhin AG. Effect of Electronic Cigarette Liquid pH on Retention of 11C-Nicotine in a Respiratory Tract Model. Nicotine Tob Res. 2023 Jun 9;25(7):1406–10.
Solingapuram Sai, Kiran K., et al. “Effect of Electronic Cigarette Liquid pH on Retention of 11C-Nicotine in a Respiratory Tract Model.Nicotine Tob Res, vol. 25, no. 7, June 2023, pp. 1406–10. Pubmed, doi:10.1093/ntr/ntad039.
Solingapuram Sai KK, Rose JE, Mukhin AG. Effect of Electronic Cigarette Liquid pH on Retention of 11C-Nicotine in a Respiratory Tract Model. Nicotine Tob Res. 2023 Jun 9;25(7):1406–1410.
Journal cover image

Published In

Nicotine Tob Res

DOI

EISSN

1469-994X

Publication Date

June 9, 2023

Volume

25

Issue

7

Start / End Page

1406 / 1410

Location

England

Related Subject Headings

  • Respiratory System
  • Public Health
  • Positron Emission Tomography Computed Tomography
  • Nicotine
  • Hydrogen-Ion Concentration
  • Humans
  • Electronic Nicotine Delivery Systems
  • Carbon Radioisotopes
  • 4206 Public health
  • 4202 Epidemiology