A robotic system for real-time analysis of inhaled submicron and microparticles

Flow Rate and Wall Shear Stress Characterization of a Biomimetic Aerosol Exposure System

Current in vitro emissions and exposure systems lack biomimicry, use unrealistic flow conditions, produce unrealistic dose, and provide inaccurate biomechanical cues to cell cultures, limiting ability to correlate in vitro outcomes with in vivo health effects. A biomimetic in vitro system capable of puffing aerosol and clean air inhalation may empower researchers to investigate complex questions related to lung injury and disease. A biomimetic aerosol exposure system (BAES), including an electronic cigarette adapter, oral cavity module (OCM), and bifurcated exposure chamber (BEC) was designed and manufactured. The fraction of aerosol deposited in transit to a filter pad or lost as volatiles was 0.116±0.021 in a traditional emissions setup versus 0.098 ± 0.015 with the adapter. The observed flowrate was within 5% of programed flowrate for puffing (25 mL/s), puff-associated respiration (450 mL/s), and tidal inhalation (350 mL/s). The maximum flowrate observed in the fabricated BAES was 450 mL/s, exceeding the lower target nominal wall shear stress of 0.025 Pa upstream of the bifurcation and fell below the target of 0.02 Pa downstream. This in vitro system addresses several gaps observed in commercially available systems and may be used to study many inhaled aerosols. The current work illustrates how in silico models may be used to correlate results of an in vitro study to in vivo conditions, rather than attempting to design an in vitro system that performs exactly as the human respiratory tract.

Electronic cigarette menthol flavoring is associated with increased inhaled micro and sub-micron particles and worse lung function in combustion cigarette smokers

Flavored electronic cigarettes (ECs) present a serious health challenge globally. Currently, it is unknown whether the addition of highly popular menthol flavoring to e-liquid is associated with changes in the number of aerosolized particles generated or altered lung function. Here, we first performed preclinical studies using our novel robotic platform Human Vaping Mimetic Real-Time Particle Analyzer (HUMITIPAA). HUMITIPAA generates fresh aerosols for any desired EC in a very controlled and user-definable manner and utilizes an optical sensing system to quantitate and analyze sub-micron and microparticles from every puff over the course of vaping session in real-time while emulating clinically relevant breathing mechanics and vaping topography. We discovered that addition of menthol flavoring to freshly prepared e-liquid base propylene glycol-vegetable glycerin leads to enhanced particle counts in all tested size fractions, similar to the effect of adding vitamin E acetate to e-liquid we previously reported. Similarly, we found that menthol vs. non-menthol (tobacco) flavored pods from commercially available ECs leads to generation of significantly higher quantities of 1-10 µm particles upon inhalation. We then retrospectively analyzed data from the COPDGene study and identified an association between the use of menthol flavored ECs and reduced FEV1% predicted and FEV1/FVC independent of age, gender, race, pack-years of smoking, and use of nicotine or cannabis-containing vaping products. Our results reveal an association between enhanced inhaled particle due to menthol addition to ECs and worse lung function indices. Detailed causal relation remains to be demonstrated in future large-scale prospective clinical studies. Importantly, here we demonstrate utility of the HUMITIPAA as a predictive enabling technology to identify inhalation toxicological potential of emerging ECs as the chemical formulation of e-liquid gets modified.

A multiplex inhalation platform to model in situ like aerosol delivery in a breathing lung-on-chip

Prolonged exposure to environmental respirable toxicants can lead to the development and worsening of severe respiratory diseases such as asthma, chronic obstructive pulmonary disease (COPD) and fibrosis. The limited number of FDA-approved inhaled drugs for these serious lung conditions has led to a shift from in vivo towards the use of alternative in vitro human-relevant models to better predict the toxicity of inhaled particles in preclinical research. While there are several inhalation exposure models for the upper airways, the fragile and dynamic nature of the alveolar microenvironment has limited the development of reproducible exposure models for the distal lung. Here, we present a mechanistic approach using a new generation of exposure systems, the Cloud α AX12. This novel in vitro inhalation tool consists of a cloud-based exposure chamber (VITROCELL) that integrates the breathing ^AXLung-on-chip system (AlveoliX). The ultrathin and porous membrane of the AX12 plate was used to create a complex multicellular model that enables key physiological culture conditions: the air-liquid interface (ALI) and the three-dimensional cyclic stretch (CS). Human-relevant cellular models were established for a) the distal alveolar-capillary interface using primary cell-derived immortalized alveolar epithelial cells (^AXiAECs), macrophages (THP-1) and endothelial (HLMVEC) cells, and b) the upper-airways using Calu3 cells. Primary human alveolar epithelial cells (^AXhAEpCs) were used to validate the toxicity results obtained from the immortalized cell lines. To mimic in vivo relevant aerosol exposures with the Cloud α AX12, three different models were established using: a) titanium dioxide (TiO2) and zinc oxide nanoparticles b) polyhexamethylene guanidine a toxic chemical and c) an anti-inflammatory inhaled corticosteroid, fluticasone propionate (FL). Our results suggest an important synergistic effect on the air-blood barrier sensitivity, cytotoxicity and inflammation, when air-liquid interface and cyclic stretch culture conditions are combined. To the best of our knowledge, this is the first time that an in vitro inhalation exposure system for the distal lung has been described with a breathing lung-on-chip technology. The Cloud α AX12 model thus represents a state-of-the-art pre-clinical tool to study inhalation toxicity risks, drug safety and efficacy.

Protocol for the operation of a breathing and vaping biomimetic robot to delineate real-time inhaled particle profile of electronic cigarettes

We recently developed a robotic human vaping mimetic real-time particle analyzer (HUMITIPAA) to evaluate the impact of change in chemical constituents and breathing profiles of electronic cigarettes (ECs) on potential pulmonary toxicity. Here, we describe the fabrication procedure of EC mouthpiece(s), establishment of sensor saturation curve, and preparation of e-liquid and vaping device(s) for testing. We further detail steps for HUMITIPAA preparation and connection setup, followed by data collection and processing. For complete details on the use and execution of this protocol, please refer to Kaiser et al. (2021).¹.