Since 2009, the United States (U.S.) Food and Drug Administration (FDA) Center for Tobacco Products (CTP) has had the authority to regulate the manufacturing, distribution, and marketing of tobacco products in order to reduce the death and disease caused by tobacco use. Biomarkers of exposure pertain to actual human exposure to chemicals arising from tobacco use and could play an important role across a number of FDA regulatory activities, including assessing new and modified risk tobacco products and identifying and evaluating potential product standards. On August 3–4, 2015, FDA/CTP hosted a public workshop focused on biomarkers of exposure with participants from government, industry, academia, and other organizations. The workshop was divided into four sessions focused on: 1) approaches to evaluating and selecting biomarkers; 2) biomarkers of exposure and relationship to disease risk; 3) currently-used biomarkers of exposure and biomarkers in development; and 4) biomarkers of exposure and the assessment of smokeless tobacco and electronic nicotine delivery systems (ENDS). This paper synthesizes the main findings from the workshop and highlights research areas that could further strengthen the science around biomarkers of exposure and help determine their application in tobacco product regulation.

ObjectivesFor electronic nicotine delivery systems (ENDS), also commonly called e-cigarettes, coil temperature is a factor in the potential production of toxic chemical constituents. However, data are lacking regarding the temperatures that are achieved in the latest generation of these devices. Fourth-generation ENDS are capable of producing heating coil temperatures well above e-liquid boiling points, and allow the user to monitor and set the heating coil temperature during a puff. In this study, we evaluate the accuracy and consistency of the temperature measurement and control settings for different brands of fourth-generation ENDS.MethodsA study was performed using three commercially available, fourth-generation ENDS. The atomizer coil temperatures were obtained from the device (using the EScribe software) reading and from thermocouples attached to the coils during simulated puffing conditions. In addition, aerosol temperatures were measured inside the atomizer and at the mouthpiece.ResultsMeasured temperatures varied widely across samples taken from the same brand. For example, thermocouple measurements for one unit were 40 Celsius (°C) below the 300 °C set point, while another unit of the same brand exceeded the set point by more than 100 °C. We observed a significant variation in temperature (approximately 100 °C) along the length of the coil in some cases.ConclusionsThe possibility of wide temperature variation across ENDS samples, as well as variations between maximum coil temperatures and internal temperature readings, may have implications for studies that seek to determine correlations between coil temperature and toxin generation.

Current thoracic artificial lungs (TALs) have blood flow impedances greater than the natural lungs, which can result in abnormal pulmonary hemodynamics. This study investigated the impedance and gas transfer performance of a TAL with a compliant housing (cTAL). Fluid-structure interaction (FSI) analysis was performed using ADINA to examine the effect of the inlet and outlet expansion angle, θ, on device impedance and blood flow patterns. Based on the results, the θ=45° model was chosen for prototyping and in vitro testing. Glycerol was pumped through this cTAL at 2, 4, and 6 L/min at 80 and 100 beats/min, and the zeroth and first harmonic impedance moduli, Z0 and Z1, were calculated. Gas transfer testing was conducted at blood flow rates of 3, 5, and 7 L/min. FSI results indicated that the 45° model had an ideal combination of low impedance and even blood flow patterns, and was thus chosen for prototyping. In vitro, Z0=0.53 ± 0.06 mmHg/(L/min) and Z1=0.86 ± 0.08 mmHg/(L/min) at 4 L/min and 100 beats/min. Outlet PO2 and SO2 values were above 200 mmHg and 99.5%, respectively, at each flow rate. Thus, the cTAL had lower impedance than hard-shell TALs and excellent gas transfer.

Various toxicants, drugs and their metabolites carry potential ovarian toxicity. Ovarian follicles, the functional unit of the ovary, are susceptible to this type of damage at all stages of their development. However, despite of the large scale of potential negative impacts, assays that study ovarian toxicity are limited. Exposure of cultured ovarian follicles to toxicants of interest served as an important tool for evaluation of toxic effects for decades. Mouse follicles cultured on the bottom of a culture dish continue to serve an important approach for mechanistic studies. In this paper, we demonstrated the usefulness of a hydrogel based 3-dimensional (3D) mouse ovarian follicle culture as a tool to study ovarian toxicity in a different setup. The 3D in vitro culture, based on fibrin alginate interpenetrating network (FA-IPN), preserves the architecture of the ovarian follicle and physiological structure-function relationship. We applied the novel 3D high-throughput (HTP) in vitro ovarian follicle culture system to study the ovotoxic effects of an anti-cancer drug, Doxorobucin (DXR). The fibrin component in the system is degraded by plasmin and appears as a clear circle around the encapsulated follicle. The degradation area of the follicle is strongly correlated with follicle survival and growth. To analyze fibrin degradation in a high throughput manner, we created a custom MATLAB® code that converts brightfield micrographs of follicles encapsulated in FA-IPN to binary images, followed by image analysis. We did not observe any significant difference between manually processed images to the automated MATLAB® method, thereby confirming that the automated program is suitable to measure fibrin degradation to evaluate follicle health. The cultured follicles were treated with DXR at concentrations ranging from 0.005 nM to 200 nM, corresponding to the therapeutic plasma levels of DXR in patients. Follicles treated with DXR demonstrated decreased survival rate in greater DXR concentrations. We observed partial follicle survival of 35% ± 3% (n = 80) in 0.01nM treatment and 48% ± 2% (n = 92) in 0.005nM, which we identified as the IC50 for secondary follicles. In summary, we established a 3D in vitro ovarian follicle culture system that could be used in an HTP approach to measure toxic effects on ovarian follicles.

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