Lung lining liquid modifies PM_2.5 in favor of particle aggregation: a protective mechanism

Abstract

The health effects of particle inhalation including urban air pollution and tobacco smoke comprise a significant public health concern worldwide, although the mechanisms by which inhaled particles cause premature deaths remain undetermined. In this study, we assessed the physicochemical interactions of fine airborne particles (PM(2.5)) and lung lining liquid using scanning electron microscopy, atomic force microscopy, and X-ray photon spectroscopy. We provide experimental evidence to show that lung lining liquid modifies the chemistry and attractive forces at the surface of PM(2.5), which leads to enhanced particle aggregation. We propose that this is an important protective mechanism that aids particle clearance in the lung.

The bio-nano-interface in predicting nanoparticle fate and behaviour in living organisms: towards grouping and categorising nanomaterials and ensuring nanosafety by design

“…The idea of airborne particulates becoming coated with lung surfactant lipid following inhalation was postulated in 1990 [6]. Proteins and lipids in lung lining liquid at the air-liquid (alveolar fluid, hypophase) interface -the first biostructure an inhaled nanoparticle encounters when deposited in the alveoli -were later observed to coat urban nanoparticles in a corona and cause nanoparticle aggregation [7][8][9].…”

“…-conformation changes → blocked or enhanced presentation of active sites and subsequent functional changes [21,22] -conferring a biological identity -altered interaction/uptake and biodistribution [23][24][25] -altered propensity for protein-protein interactions (e.g., fibrillation) [26] -altered surface characteristics and thereby stability and dispersability [8,27] and potentially also dissolution potential (as per environmental macromolecules such as humic acids) although limited literature [28] -oxidative effects -lesions, post-translational effects, etc. [29].…”

“…-reduced surface energy/reactivity [30] (possibly only temporarily) -depletion of medium components which can result in indirect toxicity effects [8,10,31] -masking targeting or other bio-functional elements? (possibly only temporarily) [32] -altered kinetics (distribution, half-life, degradation, etc.)…”

The effects of particulate matter air pollution on respiratory health and on the cardiovascular system

“…And diffusion affects the smallest particles as they are displaced by random gas motion and will principally occur in the small airways and gas exchange regions of the lung. The respiratory tract is lined with a thin liquid layer (ELF), composed of various agents such as antioxidants, lipids and proteins (98). The main component of the ELF is surfactants, which reduce surface tension and displace PM less than 6 μm in diameter (99).…”

Understanding Human Illness and Death Following Exposure to Particulate Matter Air Pollution

“…Particle size has been shown to determine: 1. the location of particle deposition in the airway and lungs, 2. the amount of surface area that can contact tissues, and 3. the rate of particle clearance from the lungs (Kendall et al, 2002;Oberdorster et al, 1994;Sioutas et al, 2005;West et al, 2003).…”