Abstract

BackgroundEngineered nanoparticles (NP) are being developed for inhaled drug delivery. This route is non-invasive and the major target; alveolar epithelium provides a large surface area for drug administration and absorption, without first pass metabolism. Understanding the interaction between NPs and target cells is crucial for safe and effective NP-based drug delivery. We explored the differential effect of neutral, cationic and anionic polystyrene latex NPs on the target cells of the human alveolus, using primary human alveolar macrophages (MAC) and primary human alveolar type 2 (AT2) epithelial cells and a unique human alveolar epithelial type I-like cell (TT1). We hypothesized that the bioreactivity of the NPs would relate to their surface chemistry, charge and size as well as the functional role of their interacting cells in vivo.MethodsAmine- (ANP) and carboxyl- surface modified (CNP) and unmodified (UNP) polystyrene NPs, 50 and 100 nm in diameter, were studied. Cells were exposed to 1–100 μg/ml (1.25-125 μg/cm2; 0 μg/ml control) NP for 4 and 24 h at 37 °C with or without the antioxidant, N-acetyl cysteine (NAC). Cells were assessed for cell viability, reactive oxygen species (ROS), oxidised glutathione (GSSG/GSH ratio), mitochondrial integrity, cell morphology and particle uptake (using electron microscopy and laser scanning confocal microscopy).ResultsANP-induced cell death occurred in all cell types, inducing increased oxidative stress, mitochondrial disruption and release of cytochrome C, indicating apoptotic cell death. UNP and CNP exhibited little cytotoxicity or mitochondrial damage, although they induced ROS in AT2 and MACs. Addition of NAC reduced epithelial cell ROS, but not MAC ROS, for up to 4 h. TT1 and MAC cells internalised all NP formats, whereas only a small fraction of AT2 cells internalized ANP (not UNP or CNP). TT1 cells were the most resistant to the effects of UNP and CNP.ConclusionANP induced marked oxidative damage and cell death via apoptosis in all cell types, while UNP and CNP exhibited low cytotoxicity via oxidative stress. MAC and TT1 cell models show strong particle-internalization compared to the AT2 cell model, reflecting their cell function in vivo. The 50 nm NPs induced a higher bioreactivity in epithelial cells, whereas the 100 nm NPs show a stronger effect on phagocytic cells.Electronic supplementary materialThe online version of this article (doi:10.1186/s12989-015-0091-7) contains supplementary material, which is available to authorized users.

Highlights

  • Engineered nanoparticles (NP) are being developed for inhaled drug delivery

  • The data are presented as mean ± standard deviation (SD), n = 3β βNanoparticles were suspended in distilled water and DCCM1 or RPMI at a concentration of 10 μg/ml and bath sonicated for 2 min before measurement

  • An important finding was that amine functionalization caused cytotoxicity in all three cell types, involving a process of induction of oxidative stress, mitochondrial disruption and Cyt C release, and likely leading to apoptotic cell death

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Summary

Introduction

Engineered nanoparticles (NP) are being developed for inhaled drug delivery. This route is non-invasive and the major target; alveolar epithelium provides a large surface area for drug administration and absorption, without first pass metabolism. The emergence of nanotechnology and nanomedicine is of increasing interest, for local and systemic treatment via inhaled drug delivery to the lung [1,2,3,4]; a range of NP-based agents have been developed to improve therapeutic and diagnostic efficiency, and to minimize adverse effects [5,6,7,8] These products have been studied in vivo [9,10,11], and in clinical trials and some have reached the clinic for the treatment of cancer, diabetes, and other lung diseases [6, 8, 12, 13] with varying degrees of success, related to a range of factors, including the unique physicochemical structure of each type of NP and its bioreactivity. All three cell types release proinflammatory mediators and we have demonstrated that interplay between these cells plays a vital role in regulating the pulmonary immune response [20, 21]

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