Fluid Films as Models for Understanding the Impact of Inhaled Particles in Lung Surfactant Layers

Abstract

Pollution is currently a public health problem associated with different cardiovascular and respiratory diseases. These are commonly originated as a result of the pollutant transport to the alveolar cavity after their inhalation. Once pollutants enter the alveolar cavity, they are deposited on the lung surfactant (LS) film, altering their mechanical performance which increases the respiratory work and can induce a premature alveolar collapse. Furthermore, the interactions of pollutants with LS can induce the formation of an LS corona decorating the pollutant surface, favoring their penetration into the bloodstream and distribution along different organs. Therefore, it is necessary to understand the most fundamental aspects of the interaction of particulate pollutants with LS to mitigate their effects, and design therapeutic strategies. However, the use of animal models is often invasive, and requires a careful examination of different bioethics aspects. This makes it necessary to design in vitro models mimicking some physico-chemical aspects with relevance for LS performance, which can be done by exploiting the tools provided by the science and technology of interfaces to shed light on the most fundamental physico-chemical bases governing the interaction between LS and particulate matter. This review provides an updated perspective of the use of fluid films of LS models for shedding light on the potential impact of particulate matter in the performance of LS film. It should be noted that even though the used model systems cannot account for some physiological aspects, it is expected that the information contained in this review can contribute on the understanding of the potential toxicological effects of air pollution.

Lung surfactant as a biophysical assay for inhalation toxicology

“…Adsorption of LS components to particle surfaces is thought to play a role in clearance from the lungs, but particle morphology or surface properties may hinder proper clearance. ( Parra and Perez-Gil, 2015 , Guzmán, 2022 , Guzmán et al, 2022 ).…”

“…As animal models are now considered a last resort, LS bioassays are a promising toxicological model for inhalation exposure with potential for high-throughput screening. ( Guzmán, 2022 , Guzmán et al, 2022 , Da Silva et al, 2021a , Dwivedi et al, 2014 , Sorli et al, 2022 ).…”

“…A study with just carbon nanoparticles also observed changes in surface pressure isotherms, compressibility, and phase transitions in LS ( Hu et al, 2020 ). Another study looked at three different types of carbonaceous soot particles ( Guzmán et al, 2022 , Guzmán, 2022 ). Insertion of the particles into LS films in an LBT was observed to modify interfacial cohesion and packing, resulting in inhibited surface tension.…”

Synchrotron radiation circular dichroism spectroscopy reveals that gold and silver nanoparticles modify the secondary structure of a lung surfactant protein B analogue

“…74 It is accepted that the use of surfactant film model systems are very useful for identifying the potential impact of particulate matter, however, they cannot reflect all physiological aspects of the system. 10 To discover whether any modifications seen in vitro to surfactant model function by NPs translate to physiological effects (i.e. negative impact on breathing) would require the use of in vivo models.…”

“…Such methods monitor surface pressure during changes in surfactant monolayer area designed to mimic surface area changes in the lung during respiration and have been used widely to explore the impact of inhaled particles, including NPs, on lung surfactant model layers. 10 For example, the results of studies using DPPC as a model surfactant have varied with some indicating no or minimal effects of NPs on surface tension behaviour, 11 whilst others provide clear indications of negative changes to surface pressure-area isotherms. [12][13][14][15][16] Similar experiments have also been undertaken using more complete models of pulmonary surfactant for a limited range of nanomaterials and found a deterioration in surface tension behaviour.…”