Combining analytical techniques to assess the translocation of diesel particles across an alveolar tissue barrier in vitro.
Level 5 - mechanism / opinion, no new human data
In vitro laboratory study evaluating particle translocation across cell cultures (bench research).
PubMed 38778339 · doi:10.1186/s12989-024-00585-7
What was done
Researchers developed an analytical methodology combining transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-VIS), and lock-in thermography (LIT) to evaluate the translocation of diesel exhaust particles (DEPs). Methods were first validated on acellular polyethylene terephthalate (PET) inserts across 0.4, 1, and 3 μm pore sizes. Human alveolar epithelial type II cells (A549) grown on 3 μm pore membranes were then exposed to DEPs at concentrations from 0 to 80 µg/mL (0 to 44 µg/cm²) for 24 hours, with or without EDTA, and the translocated fraction in the basal compartment was quantified.
What was found
Without cells, DEP translocation across 3 μm pore membranes was measured at approximately 37% by UV-VIS (limit of detection [LOD]: 1.92 µg/mL) and 75% by LIT (LOD: 0.20 µg/cm²). In the presence of A549 cells, particle translocation across the barrier was approximately 1% at 20 and 40 µg/mL (11 and 22 µg/cm²), with no particles detected at lower or higher concentrations. Co-exposure with EDTA increased DEP translocation into the basal compartment.
Why it matters
This study provides a quantitative, multi-technique framework to measure fine particle translocation across cellular barriers in vitro, supporting findings that a small fraction of inhaled diesel exhaust can cross the alveolar epithelium.
Limits
The study relies on an in vitro monoculture model using A549 cells, which lacks physiological co-factors such as macrophages, pulmonary surfactant, mucus, endothelial layers, and microvascular flow. Large discrepancies between UV-VIS (37%) and LIT (75%) in acellular controls highlight analytical variability, and the assay could not detect particle translocation at low or high concentration extremes.
Cited by
- supports Inhaled PM2.5 particulate matter and associated chemicals pass directly across the lungs into the bloodstream.