Interactions between DPPC as a component of lung surfactant and amorphous silica nanoparticles investigated by HILIC-ESI–MS

The biomolecule corona mediates pulmonary delivery of nanomedicine

Pulmonary delivery of therapeutics (e.g., biologics, antibiotics, and chemotherapies) encapsulated in nanoparticles is desirable for the ability to provide a localised treatment, bypassing the harsh gastrointestinal environment. However, limited understanding of the biological fate of nanoparticles upon administration to the lungs hinders translation of pre-clinical investigations into viable therapies. A key knowledge gap is the impact of the pulmonary biomolecular corona on the functionality of nanoparticles. In this review, opportunities and challenges associated with pulmonary nanoparticle delivery are elucidated, highlighting the impact of the pulmonary biomolecular corona on immune recognition and nanoparticle internalisation in target cells. Recent investigations detailing the influence of proteins, lipids and mucin derived from pulmonary surfactants on nanoparticle behaviour are detailed. In addition, latest approaches in modulating plasma protein corona upon systemic delivery for biodistribution to the lungs are also discussed. Key examples of reengineering nanoparticle structure to mediate formation of biomolecule corona are provided. This review aims to provide a comprehensive understanding on biomolecular corona of nanoparticles for pulmonary delivery, while accentuating their significance for successful translation of newly investigated therapeutics.

Validation of a high-performance liquid chromatography method for determining lysophosphatidylcholine content in bovine pulmonary surfactant medication

Pulmonary surfactant replacement therapy is a promising improvement in neonatal care for infants with respiratory distress syndrome. Lysophosphatidylcholine (LPC) is an undesirable component that can hinder surfactant proteins from enhancing the adsorption of surfactant lipids to balance surface tensions by creating a saturated coating on the interior of the lungs. A novel normal-phase liquid chromatography method utilizing UV detection and non-toxic solvents was developed and validated for the first time to analyze LPC in the complex matrix of pulmonary surfactant medication. The analytical method validation included evaluation of system suitability, repeatability, intermediate precision, linearity, accuracy, limit of detection (LOD), limit of quantification (LOQ), stability and robustness. The method yielded detection and quantification limits of 4.4 and 14.5 μg/ml, respectively. The calibration curve was modified linearly within the LOQ to 1.44 mg/ml range, with a determination coefficient of 0.9999 for standards and 0.9997 for sample solutions. Given the lack of reliable published data on LPC analysis in pulmonary surfactant medications, this newly developed method demonstrates promising results and offers advantages of HPLC methodology, including simplicity, accuracy, specificity, sensitivity and an exceptionally low LOD and LOQ. These attributes contribute to considering this achievement as an innovative method.

Physicochemical properties of nanoparticles affecting their fate and the physiological function of pulmonary surfactants

Pulmonary drug delivery has drawn great attention due to its targeted local lung action, reduced side effects, and ease of administration. However, inhaled nanoparticles (NPs) could adsorb different pulmonary surfactants depending on their physicochemical properties, which may impair the physiological function of the pulmonary surfactants or alter the fate of the NPs. Thus, the objective of this review is to summarize how the physicochemical properties of NPs affecting the physiological function of pulmonary surfactants and their fate. First of all, the composition and characteristics of pulmonary surfactants, methods for studying pulmonary surfactant interaction with NPs are introduced. Thereafter, the influence of physicochemical properties of NPs on hydrophobic protein adsorption and strategies to decrease the interaction of NPs with pulmonary surfactants are discussed. Finally, the influence of physicochemical properties of NPs on lipids and hydrophilic protein adsorption and consequently their fate is described. In conclusion, a better understanding of the interaction of NPs with pulmonary surfactants will promote the faster development of safe and effective nanomedicine for pulmonary drug delivery. STATEMENT OF SIGNIFICANCE: Drug delivery carriers often face complex body fluid components after entering the human body. Pulmonary surfactants diffuse at the lung gas-liquid interface, and particles inevitably interact with pulmonary surfactants after pulmonary nanomedicine delivery. This review presents an overview of how the physicochemical properties of nanoparticles affecting their fate and physiological function of pulmonary surfactants. We believe that the information included in this review can provide important guiding for the development of safe and effective pulmonary delivery nanocarriers.

Interaction between polyene antifungal drug and saturated phospholipid monolayer regulated by calcium ions at the air-water interface

Amphotericin B (AmB) is a polyene antifungal drug, which could directly form pores on the sterol-free phospholipid monolayers. The interaction between AmB and phospholipid can be affected by calcium ions, but the mechanism is still unclear. DPPC is a saturated phospholipid with -PC group, which is often used to simulate the outer cell membrane leaflet. And DPPC is also the main constituent of pulmonary surfactants. In this work, the DPPC monolayer was used as a model membrane to study the effect of calcium ions on the interaction between AmB and phospholipid. The influence of different concentration of calcium ions on the elastic modulus, mean molecular area increment, excess Gibbs free energy and stability of the AmB/DPPC mixed monolayer has been researched at the surface pressure of 7.5 mN/m, 12.5 mN/m and 22.5 mN/m. The AmB/DPPC monolayers at the air-water interface have been observed in real-time by Brewster angle microscope and the microstructure of the Langmuir-Blodgett monolayer films transferred onto the mica have been researched by scanning electron microscope and atomic force microscope. The results showed that calcium ions had a significant influence on the elastic modulus, mean molecular area increment, excess Gibbs free energy, stability and microstructure of the AmB/DPPC monolayer. It has been indicated that the influence of calcium ions on the interaction between AmB and DPPC molecules mainly depended on the effect of calcium ions on the orientation of AmB molecules. The calcium ions could regulate the effect of AmB to the stability of the DPPC monolayer. This regulatory role changed with the different concentrations of calcium ions and the different phase states of the monolayer. This work provides useful information to further understand the influence mechanism of calcium ions on the interaction between AmB and saturated phospholipid with -PC group, which is helpful to find out the effect mechanism of calcium ion on the interaction between AmB and the outer layer of cell membrane or pulmonary surfactants in different phase states and to understand the toxicity mechanism of AmB on the cell membrane or lungs.

Development of Human Lung Induction Models for Air Pollutants' Toxicity Assessment

There is an urgent need for reliable and effective models to study air pollution health effects on human lungs. Here, we report the utilization of human pluripotent stem cell (hPSC) induction models for human lung progenitor cells (hLPs) and alveolar type 2 epithelial cell-like cells (ATLs) for the toxicity assessment of benzo(a)pyrene, nano-carbon black, and nano-SiO₂, as common air pollutants. We induced hPSCs to generate ATLs, which recapitulated key features of human lung type 2 alveolar epithelial cells, and tested the induction models for cellular uptake of nanoparticles and toxicity evaluations. Our findings reveal internalization of nano-carbon black, dose-dependent uptake of nano-SiO₂, and interference with surfactant secretion in ATLs exposed to benzo(a)pyrene/nano-SiO₂. Thus, hLP and ATL induction models could facilitate the evaluation of environmental pollutants potentially affecting the lungs. In conclusion, this is one of the first studies that managed to adopt hPSC pulmonary induction models in toxicology studies.

Multi-walled carbon nanotubes (MWCNTs) transformed THP-1 macrophages into foam cells: Impact of pulmonary surfactant component dipalmitoylphosphatidylcholine

Pulmonary surfactant or its components can function as barriers toward nanomaterials (NMs) entering pulmonary systems. However, since pulmonary surfactant mainly consists of lipids, it may be necessary to investigate the effects of co-exposure to NMs and pulmonary surfactant or its components on lipid metabolism and related signaling pathways. Recently we found that multi-walled carbon nanotubes (MWCNTs) transformed THP-1 macrophages into lipid-laden foam cells via ER stress pathway. Here this study further investigated the impact of pulmonary surfactant component dipalmitoylphosphatidylcholine (DPPC) on this process. Up to 64 μg/mL hydroxylated or carboxylated MWCNTs induced lipid accumulation and IL-6 release in THP-1 macrophages, accompanying with increased oxidative stress and p-chop proteins (biomarker for ER stress). Incubation with 100 μg/mL DPPC led to MWCNT surface coating but did not significantly alter MWCNT internalization, lipid burden or IL-6 release. However, lipidomics indicated that DPPC altered lipid profliles in MWCNT-exposed cells. DPPC also led to a higher level of de novo lipogenesis regulator FASN in cells exposed to hydroxylated MWCNTs, as well as a higher level of p-chop and scavenger receptor MSR1 in cells exposed to carboxylated MWCNTs. Combined, DPPC did not significantly affect MWCNT-induced lipid accumulation but altered lipid components and ER stress in macrophages.

Naringenin-Loaded Dipalmitoylphosphatidylcholine Phytosome Dry Powders for Inhaled Treatment of Acute Lung Injury

Background: Acute lung injury is a severe respiratory disorder characterized by overwhelming lung inflammation. Dipalmitoylphosphatidylcholine (DPPC) is the major lipid component of pulmonary surfactant, which here acts as a carrier delivery system for drugs, while also preserving surface tension in the lung. The clinical development of naringenin (NG) is limited by its low solubility and bioavailability. Methods: Novel NG-loaded DPPC phytosomes for dry powder inhalation (NPDPIs) were prepared by solvent evaporation and a freeze-drying method. The particle size, electric potential, in vitro release, and lung deposition were characterized. A rat model of acute lung injury was established and used for pharmacodynamic evaluations. Results: A mixture of NG/DPPC 1:2 (w/w) formed stable phytosomes with the addition of appropriate ethanol. The phytosomes had high complexation efficiency (92.1% ± 1.87%) with NG, a small mean size (150.8 ± 6.9 nm), and a high zeta potential (20.97 ± 0.55 mV). NPDPIs composed of mannitol/DPPC/NG (4:2:1, w/w/w) presented a satisfactory appearance, good fluidity, quick reconstitution to naringenin phytosomes (NGPs), and small (167.2 nm) reconstituted NGPs. The aerodynamic diameter (12.48 μm) and fine particle fraction (23.90%) were suitable for pulmonary delivery by inhalation. The in vivo NPDPIs demonstrated efficacy in a rat model of acute lung injury. NPDPIs significantly inhibited the phosphorylation of P38 in the mitogen-activated protein kinase pathway and suppressed oxidative stress. Surprisingly, the DPPC vehicle exhibited potential effects against acute lung injury by protecting respiratory function. Conclusions: NPDPIs were developed for sustained drug release, promoting pulmonary bioavailability of drug and protecting against acid-induced acute lung injury in rats by pulmonary delivery. NPDPIs are a promising dry powder inhaler for clinical application in acute lung injury.

Evaluation of in vitro toxicity of silica nanoparticles (NPs) to lung cells: Influence of cell types and pulmonary surfactant component DPPC

Cultured human lung epithelial cells, particularly A549 cells, are commonly used as the in vitro model to evaluate the inhalational toxicity of nanoparticles (NPs). However, A549 cells are cancer cells that might not reflect the response of normal tissues to NP exposure. In addition, the possible influence of pulmonary surfactant also should be considered. This study used silica NPs as model NPs, and evaluated the toxicity of silica NPs to both 16HBE human bronchial epithelial cells and A549 adenocarcinomic cells, with or without the presence of pulmonary surfactant component dipalmitoyl phosphatidylcholine (DPPC). We found that silica NPs induced cytotoxicity at the concentration of 128 μg/mL in 16HBE cells but not A5490 cells, and the cytotoxicity of silica NPs to 16HBE cells was inhibited by DPPC. Intracellular reactive oxygen species (ROS) was only induced in 16HBE cells, accompanying with decreased thiol levels. Moreover, 16HBE cells internalized more silica NPs compared with A549 cells, and the internalization was reduced with the presence of DPPC in both types of cells. The retention of ABC transporter substrate Calcein was only significantly induced by silica NPs at high concentrations in 16HBE cells, and was partially reduced due to the presence of DPPC. In addition, ABC transporter inhibitor MK571 increased the toxicity of silica NPs to both types of cells, with 16HBE cells being more sensitive. Our data revealed that the cell types and pulmonary surfactant components could influence the toxicological consequences of silica NPs to human lung cells. Therefore, it is recommended that in vitro studies should carefully select suitable models to evaluate the inhalational toxicity of NPs.

Toxicity of ZnO nanoparticles (NPs) to A549 cells and A549 epithelium in vitro: Interactions with dipalmitoyl phosphatidylcholine (DPPC)

Once inhaled, nanoparticles (NPs) will first interact with lung surfactant system, which may influence the colloidal aspects of NPs and consequently the toxic potential of NPs to pulmonary cells. In this study, we investigated the effects of dipalmitoyl phosphatidylcholine (DPPC), the major component in lung surfactant, on stability and toxicity of ZnO NPs. The presence of DPPC increased the UV-vis spectra, hydrodynamic size, Zeta potential and dissolution rate of ZnO NPs, which indicates that DPPC might interact with NPs and affect the colloidal stability of NPs. Exposure to ZnO NPs induced cytotoxicity associated with increased intracellular Zn ions but not superoxide in A549 cells. In A549 epithelium model, exposure to ZnO NPs induced cytotoxicity and decreased the release of interleukin 6 (IL-6) without a significant effect on epithelial permeability rate. Co-exposure of A549 cells or A549 epithelium model to DPPC and ZnO NPs induced a higher release of lactate dehydrogenase (LDH) and interleukin-6 (IL-6) compared with the exposure of ZnO NPs alone. We concluded that the presence of DPPC could influence the colloidal stability of ZnO NPs and increase the damage of NPs to membrane probably due to the increased positive surface charge.