Structure and sedimentation kinetics of dense suspensions of fibroblast cells

We investigate the structure and the dynamics of dense suspensions of NIH 3T3 fibroblast cells. Using two-photon microscopy we obtain three dimensional (3D) images from which the size and the packing structure of the dense cell suspensions can be extracted. In addition, we analyse the global time-dependent behaviour of the suspensions by time-lapse measurements of cell sedimentation. Since cell adhesion is a non-equilibrium living process the interplay can be influenced by cell viability interfering with cell–cell interactions

Dynamic and biocompatible thermo-responsive magnetic hydrogels that respond to an alternating magnetic field

Magnetic thermo-responsive hydrogels are a new class of materials that have recently attracted interest in biomedicine due to their ability to change phase upon magnetic stimulation. They have been used for drug release, magnetic hyperthermia treatment, and can potentially be engineered as stimuli-responsive substrates for cell mechanobiology. In this regard, we propose a series of magnetic thermo-responsive nanocomposite substrates that undergo cyclical swelling and de-swelling phases when actuated by an alternating magnetic field in aqueous environment. The synthetized substrates are obtained with a facile and reproducible method from poly-N- isopropylacrylamide and superparamagnetic iron oxide nanoparticles. Their conformation and the temperature-related, magnetic, and biological behaviors were characterized via scanning electron microscopy, swelling ratio analysis, vibrating sample magnetometry, alternating magnetic field stimulation and indirect viability assays. The nanocomposites showed no cytotoxicity with fibroblast cells, and exhibited swelling/de-swelling behavior near physiological temperatures (around 34 °C). Therefore these magnetic thermo-responsive hydrogels are promising materials as stimuli-responsive substrates allowing the study of cell-behavior by changing the hydrogel properties in situ

Templated assembly of pore-forming peptides in lipid membranes

Pore-forming peptides are of interest due to their antimicrobial activity and ability to form gateways through lipid membranes. Chemical modification of these peptides makes it possible to arrange several peptide monomers into well-defined pore-forming structures using various templating strategies. These templated super-structures can exert antimicrobial activity at significantly lower total peptide concentration than their untemplated equivalents. In addition, the chemical moieties used for templating may be functionalized to interact specifically with targeted membranes such as those of pathogens or cancer cells. A range of molecular templates has been explored, including dimerization of pore-forming monomers, their covalent attachment to cyclodextrin, porphyrin or fullerene scaffolds as well as attachment of amino acid linkers or nucleic acid constructs to generate assemblies of 4 to 26 peptides or proteins. Compared to free peptide monomers, templated pore assemblies showed increased membrane affinity, prolonged open-state lifetimes of the pores and more frequent pore formation due to higher local concentration. These constructs are useful model systems for biophysical studies to understand porin and ion channel proteins and their mechanisms of insertion into lipid membranes. Recently designed DNA- templates are expanding the usefulness of templated pore assemblies beyond applications of cell killing and may include targeted drug delivery and accelerate the emerging field of single-molecule detection and characterization of biomolecules by nanopore-based resistive pulse sensing

Use of EpiAlveolar Lung Model to Predict Fibrotic Potential of Multiwalled Carbon Nanotubes

Expansion in production and commercial use of nanomaterials increases the potential human exposure during the lifecycle of these materials (production, use, and disposal). Inhalation is a primary route of exposure to nanomaterials; therefore it is critical to assess their potential respiratory hazard. Herein, we developed a three-dimensional alveolar model (EpiAlveolar) consisting of human primary alveolar epithelial cells, fibroblasts, and endothelial cells, with or without macrophages for predicting long-term responses to aerosols. Following thorough characterization of the model, proinflammatory and profibrotic responses based on the adverse outcome pathway concept for lung fibrosis were assessed upon repeated subchronic exposures (up to 21 days) to two types of multiwalled carbon nanotubes (MWCNTs) and silica quartz particles. We simulate occupational exposure doses for the MWCNTs (1–30 μg/cm2) using an air–liquid interface exposure device (VITROCELL Cloud) with repeated exposures over 3 weeks. Specific key events leading to lung fibrosis, such as barrier integrity and release of proinflammatory and profibrotic markers, show the responsiveness of the model. Nanocyl induced, in general, a less pronounced reaction than Mitsui-7, and the cultures with human monocyte- derived macrophages (MDMs) showed the proinflammatory response at later time points than those without MDMs. In conclusion, we present a robust alveolar model to predict inflammatory and fibrotic responses upon exposure to MWCNTs

Use of EpiAlveolar Lung Model to Predict Fibrotic Potential of Multiwalled Carbon Nanotubes

Expansion in production and commercial use of nanomaterials increases the potential human exposure during the lifecycle of these materials (production, use, and disposal). Inhalation is a primary route of exposure to nanomaterials; therefore it is critical to assess their potential respiratory hazard. Herein, we developed a three-dimensional alveolar model (EpiAlveolar) consisting of human primary alveolar epithelial cells, fibroblasts, and endothelial cells, with or without macrophages for predicting long-term responses to aerosols. Following thorough characterization of the model, proinflammatory and profibrotic responses based on the adverse outcome pathway concept for lung fibrosis were assessed upon repeated subchronic exposures (up to 21 days) to two types of multiwalled carbon nanotubes (MWCNTs) and silica quartz particles. We simulate occupational exposure doses for the MWCNTs (1–30 μg/cm2) using an air–liquid interface exposure device (VITROCELL Cloud) with repeated exposures over 3 weeks. Specific key events leading to lung fibrosis, such as barrier integrity and release of proinflammatory and profibrotic markers, show the responsiveness of the model. Nanocyl induced, in general, a less pronounced reaction than Mitsui-7, and the cultures with human monocyte- derived macrophages (MDMs) showed the proinflammatory response at later time points than those without MDMs. In conclusion, we present a robust alveolar model to predict inflammatory and fibrotic responses upon exposure to MWCNTs

A hydrofluoric acid-free method to dissolve and quantify silica nanoparticles in aqueous and solid matrices

As the commercial use of synthetic amorphous silica nanomaterials (SiO2-NPs) increases, their effects on the environment and human health have still not been explored in detail. An often-insurmountable obstacle for SiO2-NP fate and hazard research is the challenging analytics of solid particulate silica species, which involves toxic and corrosive hydrofluoric acid (HF). We therefore developed and validated a set of simple hydrofluoric acid-free sample preparation methods for the quantification of amorphous SiO2 micro- and nanoparticles. To circumvent HF, we dissolved the SiO2- NPs by base-catalyzed hydrolysis at room temperature or under microwave irradiation using potassium hydroxide, replacing the stabilizing fluoride ions with OH−, and exploiting the stability of the orthosilicic acid monomer under a strongly basic pH. Inductively coupled plasma – optical emission spectroscopy (ICP-OES) or a colorimetric assay served to quantify silicon. The lowest KOH: SiO2 molar ratio to effectively dissolve and quantify SiO2-NPs was 1.2 for colloidal Stöber SiO2-NPs at a pH >12. Fumed SiO2-NPs (Aerosil®) or food grade SiO2 (E551) containing SiO2-NPs were degradable at higher KOH: SiO2 ratios >8000. Thus, hydrofluoric acid-free SiO2- NP digestion protocols based on KOH present an effective (recoveries of <84%), less hazardous, and easy to implement alternative to current methods

Phase transformation of superparamagnetic iron oxide nanoparticles via thermal annealing: implications for hyperthermia applications

Magnetic hyperthermia has the potential to play an important role in cancer therapy and its efficacy relies on the nanomaterials selected. Superparamagnetic iron oxide nanoparticles (SPIONs) are excellent candidates due to the ability of producing enough heat to kill tumor cells by thermal ablation. However, their heating properties depend strongly on crystalline structure and size, which may not be controlled and tuned during the synthetic process; therefore, a postprocessing is needed. We show how thermal annealing can be simultaneously coupled with ligand exchange to stabilize the SPIONs in polar solvents and to modify their crystal structure, which improves hyperthermia behavior. Using high-resolution transmission electron microscopy, X-ray diffraction, Mössbauer spectroscopy, vibrating sample magnetometry, and lock-in thermography, we systematically investigate the impact of size and ligand exchange procedure on crystallinity, their magnetism, and heating ability. We describe a valid and simple approach to optimize SPIONs for hyperthermia by carefully controlling the size, colloidal stability, and crystallinity

Structure and Sedimentation Kinetics of Dense Suspensions of Fibroblast Cells

Abstract: We investigate the structure and the dynamics of dense suspensions of NIH 3T3 fibroblast cells. Using two-photon microscopy we obtain three dimensional (3D) images from which the size and the packing structure of the dense cell suspensions can be extracted. In addition, we analyse the global time-dependent behaviour of the suspensions by time-lapse measurements of cell sedimentation. Since cell adhesion is a non-equilibrium living process the interplay can be influenced by cell viability interfering with cell–cell interactions

Templated Assembly of Pore-forming Peptides in Lipid Membranes

Abstract: Pore-forming peptides are of interest due to their antimicrobial activity and ability to form gateways through lipid membranes. Chemical modification of these peptides makes it possible to arrange several peptide monomers into well-defined pore-forming structures using various templating strategies. These templated super-structures can exert antimicrobial activity at significantly lower total peptide concentration than their untemplated equivalents. In addition, the chemical moieties used for templating may be functionalized to interact specifically with targeted membranes such as those of pathogens or cancer cells. A range of molecular templates has been explored, including dimerization of pore-forming monomers, their covalent attachment to cyclodextrin, porphyrin or fullerene scaffolds as well as attachment of amino acid linkers or nucleic acid constructs to generate assemblies of 4 to 26 peptides or proteins. Compared to free peptide monomers, templated pore assemblies showed increased membrane affinity, prolonged open-state lifetimes of the pores and more frequent pore formation due to higher local concentration. These constructs are useful model systems for biophysical studies to understand porin and ion channel proteins and their mechanisms of insertion into lipid membranes. Recently designed DNA-templates are expanding the usefulness of templated pore assemblies beyond applications of cell killing and may include targeted drug delivery and accelerate the emerging field of single-molecule detection and characterization of biomolecules by nanopore-based resistive pulse sensing