title: Real-time assessment of cigarette smoke particle deposition in vitro.
abstract: BACKGROUND
  Recently there has been a rapid increase in approaches to assess the effects of cigarette smoke in vitro. Despite a range of gravimetric and chemical methods, there is a requirement to identify simpler and more reliable methods to quantify in vitro whole smoke dose, to support extrapolation and comparisons to human/in vivo dose. We have previously characterised an in vitro exposure system using a Borgwaldt RM20S smoking machine and a chamber exposing cellular cultures to whole smoke at the air-liquid interface. In this study we demonstrate the utility of a quartz crystal microbalance (QCM), using this exposure system, to assess real-time cigarette smoke particulate deposition during a 30 minute smoke exposure. Smoke was generated at various dilutions (1:5-1:400, smoke:air) using two cigarette products, 3R4F Kentucky reference and 1 mg commercially available cigarettes. The QCM, integrated into the chamber, assessed particulate deposition and data generated were compared to traditional chemical spectrofluorometric analysis.
  
  
  RESULTS
  The QCM chamber was able to detect mass differences between the different products within the nanogram range. 3R4F reference cigarette smoke deposition ranged from 25.75 ±2.30 μg/cm2 (1:5) to 0.22 ±0.03 μg/cm2 (1:400). 1 mg cigarette smoke deposition was less and ranged from 1.42 ±0.26 μg/cm2 (1:5), to 0.13 ±0.02 μg/cm2 (1:100). Spectrofluorometric analysis demonstrated statistically significant correlation of particulate deposition with the QCM (p < 0.05), and regression R2 value were 97.4 %. The fitted equation for the linear model which describes the relationship is: QCM = -0.6796 + 0.9744 chemical spectrofluorescence.
  
  
  CONCLUSIONS
  We suggest the QCM is a reliable, effective and simple tool that can be used to quantify smoke particulate deposition in real-time, in vitro and can be used to quantify other aerosols delivered to our chamber for assessment.
authors.affiliation: British American Tobacco, Group R&D, Regents Park Road, Southampton, SO, 15 8TL, UK. Marianna_Gaca@bat.com.
authors.forename: Jason
authors.initials: J
authors.lastname: Adamson
authors.forename: Sophie
authors.initials: S
authors.lastname: Hughes
authors.forename: David
authors.initials: D
authors.lastname: Azzopardi
authors.forename: John
authors.initials: J
authors.lastname: McAughey
authors.forename: Marianna D
authors.initials: MD
authors.lastname: Gaça