Role of bovine serum albumin and humic acid in the interaction between SiO2 nanoparticles and model cell membranes

doi:10.1016/j.envpol.2016.09.059

Environmental Pollution

Volume 219, December 2016, Pages 1-8

https://doi.org/10.1016/j.envpol.2016.09.059 Get rights and content

Highlights

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BSA adsorption on SiO2 NPs mitigates the NP-induced membrane disruption.
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BSA-treated SiO2 NPs cause least membrane gelation.
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HA-treated SiO2 NPs cause most serious membrane gelation.

Abstract

Silica nanoparticles (SiO₂ NPs) can cause health hazard after their release into the environment. Adsorption of natural organic matter and biomolecules on SiO₂ NPs alters their surface properties and cytotoxicity. In this study, SiO₂ NPs were treated by bovine serum albumin (BSA) and humic acid (HA) to study their effects on the integrity and fluidity of model cell membranes. Giant and small unilamellar vesicles (GUVs and SUVs) were prepared as model cell membranes in order to avoid the interference of cellular activities. The microscopic observation revealed that the BSA/HA treated (BSA-/HA-) SiO₂ NPs took more time to disrupt membrane than untreated-SiO₂ NPs, because BSA/HA adsorption covered the surface Si single bond OH/SiO^- groups and weakened the interaction between NPs and phospholipids. The deposition of SiO₂ NPs on membrane was monitored by a quartz crystal microbalance with dissipation (QCM-D). Untreated- and HA-SiO₂ NPs quickly disrupted the SUV layer on QCM-D sensor; BSA-SiO₂ NPs attached on the membranes but only caused slow vesicle disruption. Untreated-, BSA- and HA-SiO₂ NPs all caused the gelation of the positively-charged membrane, which was evaluated by the generalized polarity values. HA-SiO₂ NPs caused most serious gelation, and BSA-SiO₂ NPs caused the least. Our results demonstrate that the protein adsorption on SiO₂ NPs decreases the NP-induced membrane damage.

Graphical abstract

Introduction

Silica nanoparticles (SiO₂ NPs) are increasingly used in inorganic paints, semiconductors, drug delivery and medical imaging due to their special physiochemical properties (Lu et al., 2007, Lu et al., 2010, Trewyn et al., 2008). Their application raises the chance of possible exposure to human beings. Studies have reported that the inhale of SiO₂ NPs can cause health problems, such as granuloma formation, silicosis, emphysema and even lung cancer (Attfield and Costello, 2004, Maynard and Kuempel, 2005, Napierska et al., 2010, Pisani et al., 2015).

The knowledge on the interaction between NPs and cell membrane is important to the toxicity mechanisms and the safe applications of SiO₂ NPs. Cell membrane is the first contacting site when cells are exposed to NPs. Oxide NPs have been reported to change the molecular structure of proteins and lipids (Jiang et al., 2010), thus can influence the cell membrane morphology and function. Intact and fluid plasma membrane is essential to maintain cellular physiological activities. The intact membrane isolates the intracellular environment and keeps the normal cell metabolism. NPs can disrupt intact membrane as suggested by the microscopic observation (Laurencin et al., 2010, Olubummo et al., 2013, Liang et al., 2014) or dye diffusion assay (Leroueil et al., 2007). Membrane fluidity is necessary for substance exchange between intra- and extracellular environment, which can be either increased or reduced after NP exposure (Park et al., 2006, Santhosh et al., 2014).

Human beings or other organisms are rarely exposed to bare NPs, because NPs adsorb the widely existent natural organic matter (NOM) after their release into natural waters or soils, and interact with biomolecules in interstitial fluid after the uptake by organisms. The physiochemical properties of SiO₂ NPs with NOM/biomolecular coatings are different from the bare particles in their size, charge, stability, surface functional groups, etc (Schwabe et al., 2013, Yallapu et al., 2015). The cellular uptake and cytotoxicity of NPs are also changed by the adsorption of NOM/biomolecules (Ge et al., 2011, Ruge et al., 2011, Lin et al., 2012). The adsorbed NOM/biomolecules form a physical barrier between NPs and cell surface, which can prevent the NPs from contacting cell surface or producing reactive oxygen species (ROS) (Lin et al., 2012, Yallapu et al., 2015). However, the enhanced NP toxicity after NOM adsorption also has been reported due to the increasing oxidative stress and the release of toxic cations (Wang et al., 2011, Yang et al., 2013). Considering the complicated influences from NOM/biomolecules and the inconsistent toxicity reports, how the NOM/biomolecule-treated SiO₂ NPs interact with cell membrane should be addressed. It is a key step related to both the cellular uptake and cytotoxicity of SiO₂ NPs in the real environment. Up to date, the role of surface coatings on the SiO₂ NP mediated cell membrane damage is largely unknown.

Humic acids (HAs) are widely existent NOM and proteins are the most important group of biomolecules in body fluid. Therefore HA and bovine serum albumin (BSA) are selected to represent the NOM and biomolecules, respectively. This work aims to study the influence of BSA/HA adsorption on the SiO₂ NP-membrane interaction, and on the membrane integrity and fluidity. Phospholipid vesicles are prepared as model membranes to avoid the uncertain influences of cellular physiological activities. This study will provide better understanding on the potential physical mechanism of toxicity.

Section snippets

Materials

Porous type (P single bond SiO₂) and sphere type silica (SSiO₂) NPs were purchased from Zhejiang Hongsheng Material Technology Co., China. The two types of silica NPs are most widely-used industrial nanomaterials but have different surface properties. The phospholipids 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1,2-Dioleoyl-sn-Glycero-3-[Phopho-rac-(1-glycerol)] (Sodium Salt) (DOPG), 1,2-dipalmitoyl-3-trimethylammonium-propane (chloride salt) (16:0 TAP), and fluorescent lipid 1,2-dipalmitoyl-sn

Properties of untreated-, BSA- and HA-SiO₂ NPs

The morphologies of untreated-, BSA- and HA-SiO₂ NPs are imaged by TEM (Fig. S2). The measured single particle diameters are consistent with the reported average diameters of 20 nm by the manufacturer. However, the d_H of SiO₂ NPs measured after 30-min sonication are much larger due to the particle aggregation in suspension (Table S1). The d_H values of untreated SiO₂ NPs increase with time, but BSA and HA treatments slow the particle aggregation (Table S1), resulting in more stable particle

Conclusion

Natural organic matter in the environment and the biomolecules in the body fluid can adhere on the released NPs and affect the interaction between NPs and cell membranes. In this study, BSA-SiO₂ NPs disrupt membrane slower than the untreated-SiO₂ NPs. BSA or HA adsorption shields the large amount of Si single bond OH/SiO^- groups on SiO₂ NP surface, avoids their interaction with membrane, which mitigates the membrane disruption. However, HA contains large amount of functional groups and can interact with

Acknowledgements

This work was supported by the National Natural Science Foundation of China (projects 21377070 and 41303079), the State Kay Laboratory of Pollution Control and Resource Reuse (project PCRRF13010 and PCRRF14010), the Fundamental Research Funds of Shandong University, and the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry of China.

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Role of bovine serum albumin and humic acid in the interaction between SiO2 nanoparticles and model cell membranes☆

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Materials

Properties of untreated-, BSA- and HA-SiO2 NPs

Conclusion

Acknowledgements

Biophys. J.

Eur. J. Pharm. Biopharm.

Environ. Res.

Water Res.

Colloid. Surf. B

Nanomed-Nanotechnol

Chem. Phys. Lipids

Chemosphere

Chem. Eng. J.

J. Hazard. Mater

Biomaterials

Quantitative exposure-response for silica dust and lung cancer in Vermont granite workers

Am. J. Ind. Med.

Multiwalled carbon nanotube deposition on model environmental surfaces

Environ. Sci. Technol.

Quartz crystal microbalance with dissipation monitoring of supported lipid bilayers on various substrates

Nat. Protoc.

The first study of surface modified silica nanoparticles in pressure-decreasing application

RSC Adv.

Monitoring the effect of three humic acids on a model membrane system using 31P NMR

Environ. Sci. Technol.

DSC and Raman study on the effect of lysozyme and bovine serum albumin on phospholipid liposomes

J. Therm. Anal. Calorim.

Visualizing lipid structure and raft domains in living cells with two-photon microscopy

P. Natl. Acad. Sci. U. S. A.

Binding of blood proteins to carbon nanotubes reduces cytotoxicity

P. Natl. Acad. Sci. U. S. A.

Interaction between oxide nanoparticles and biomolecules of the bacterial cell envelope as examined by infrared spectroscopy

Langmuir

Role of bovine serum albumin and humic acid in the interaction between SiO₂ nanoparticles and model cell membranes☆

Properties of untreated-, BSA- and HA-SiO₂ NPs

Monitoring the effect of three humic acids on a model membrane system using ³¹P NMR