Kleanthis Fytianos

Fluorescence‐Encoded Gold Nanoparticles: Library Design and Modulation of Cellular Uptake into Dendritic Cells

In order to harness the unique properties of nanoparticles for novel clinical applications and to modulate their uptake into specific immune cells we designed a new library of homo- and hetero-functional fluorescence-encoded gold nanoparticles (Au-NPs) using different poly(vinyl alcohol) and poly(ethylene glycol)-based polymers for particle coating and stabilization. The encoded particles were fully characterized by UV-Vis and fluorescence spectroscopy, zeta potential and dynamic light scattering. The uptake by human monocyte derived dendritic cells in vitro was studied by confocal laser scanning microscopy and quantified by fluorescence-activated cell sorting and inductively coupled plasma atomic emission spectroscopy. We show how the chemical modification of particle surfaces, for instance by attaching fluorescent dyes, can conceal fundamental particle properties and modulate cellular uptake. In order to mask the influence of fluorescent dyes on cellular uptake while still exploiting its fluorescence for detection, we have created hetero-functionalized Au-NPs, which again show typical particle dependent cellular interactions. Our study clearly prove that the thorough characterization of nanoparticles at each modification step in the engineering process is absolutely essential and that it can be necessary to make substantial adjustments of the particles in order to obtain reliable cellular uptake data, which truly reflects particle properties.

Uptake efficiency of surface modified gold nanoparticles does not correlate with functional changes and cytokine secretion in human dendritic cells in vitro

Engineering nanoparticles (NPs) for immune modulation require a thorough understanding of their interaction(s) with cells. Gold NPs (AuNPs) were coated with polyethylene glycol (PEG), polyvinyl alcohol (PVA) or a mixture of both with either positive or negative surface charge to investigate uptake and cell response in monocyte-derived dendritic cells (MDDCs). Inductively coupled plasma optical emission spectrometry and transmission electron microscopy were used to confirm the presence of Au inside MDDCs. Cell viability, (pro-)inflammatory responses, MDDC phenotype, activation markers, antigen uptake and processing were analyzed. Cell death was only observed for PVA-NH2 AuNPs at the highest concentration. MDDCs internalize AuNPs, however, surface modification influenced uptake. Though limited uptake was observed for PEG-COOH AuNPs, a significant tumor necrosis factor-alpha release was induced. In contrast, (PEG+PVA)-NH2 and PVA-NH2 AuNPs were internalized to a higher extent and caused interleukin-1beta secretion. None of the AuNPs caused changes in MDDC phenotype, activation or immunological properties. From the clinical editor: This team of authors investigated the influence of gold nano-particles with different surface modifications on immunological properties in monocyte-derived dendritic cells. AuNPs triggered responses in these cells that has to be further investigated in terms of development of novel vaccine carriers.

Interaction of biomedical nanoparticles with the pulmonary immune system

Engineered nanoparticles (NPs) offer site-specific delivery, deposition and cellular uptake due to their unique physicochemical properties and were shown to modulate immune responses. The respiratory tract with its vast surface area is an attractive target organ for innovative immunomodulatory therapeutic applications by pulmonary administration of such NPs, enabling interactions with resident antigen-presenting cells (APCs), such as dendritic cells and macrophages. Depending on the respiratory tract compartment, e.g. conducting airways, lung parenchyma, or lung draining lymph nodes, APCs extensively vary in their number, morphology, phenotype, and function. Unique characteristics and plasticity render APC populations ideal targets for inhaled specific immunomodulators. Modulation of immune responses may operate in different steps of the immune cell-antigen interaction, i.e. antigen uptake, trafficking, processing, and presentation to T cells. Meticulous analysis of the immunomodulatory potential, as well as pharmacologic and biocompatibility testing of inhalable NPs is required to develop novel strategies for the treatment of respiratory disorders such as allergic asthma. The safe-by-design and characterization of such NPs requires well coordinated interdisciplinary research uniting engineers, chemists biologists and respiratory physicians. In this review we will focus on in vivo data available to facilitate the design of nanocarrier-based strategies using NPs to modulate pulmonary immune responses.

Current in vitro approaches to assess nanoparticle interactions with lung cells

The respiratory tract is in constant contact with inhaled antigens from the external environment. In order to shape its line of defense, it is populated by various types of immune cells. Taking into account the scientific breakthroughs of nanomedicine and nanoparticle drug delivery, we can think of the respiratory tract as an ideal target organ to study and develop nanocarrier-based vaccines to treat respiratory tract disorders. Nanoparticles have been proven capable of specific cell targeting and, when suitably engineered, are able to induce an immunomodulatory effect. The aim of this review is to highlight in vitro approaches to the study of nanoparticle-lung immune cell interactions and recent advances in the targeting of immune cells using nanoparticle-based systems.

Aerosol Delivery of Functionalized Gold Nanoparticles Target and Activate Dendritic Cells in a 3D Lung Cellular Model

Nanocarrier design combined with pulmonary drug delivery holds great promise for the treatment of respiratory tract disorders. In particular, targeting of dendritic cells that are key immune cells to enhance or suppress an immune response in the lung is a promising approach for the treatment of allergic diseases. Fluorescently encoded poly(vinyl alcohol) (PVA)-coated gold nanoparticles, functionalized with either negative (-COO-) or positive (-NH3+) surface charges, were functionalized with a DC-SIGN antibody on the particle surface, enabling binding to a dendritic cell surface receptor. A 3D coculture model consisting of epithelial and immune cells (macrophages and dendritic cells) mimicking the human lung epithelial tissue barrier was employed to assess the effects of aerosolized AuNPs. PVA-NH2 AuNPs showed higher uptake compared to that of their -COOH counterparts, with the highest uptake recorded in macrophages, as shown by flow cytometry. None of the AuNPs induced cytotoxicity or necrosis or increased cytokine secretion, whereas only PVA-NH2 AuNPs induced higher apoptosis levels. DC-SIGN AuNPs showed significantly increased uptake by monocyte-derived dendritic cells (MDDCs) with subsequent activation compared to non-antibody-conjugated control AuNPs, independent of surface charge. Our results show that DC-SIGN conjugation to the AuNPs enhanced MDDC targeting and activation in a complex 3D lung cell model. These findings highlight the potential of immunoengineering approaches to the targeting and activation of immune cells in the lung by nanocarriers.

A novel technique to determine the cell type specific response within an in vitro co-culture model via multi-colour flow cytometry

Determination of the cell type specific response is essential towards understanding the cellular mechanisms associated with disease states as well as assessing cell-based targeting of effective therapeutic agents. Recently, there have been increased calls for advanced in vitro multi-cellular models that provide reliable and valuable tools correlative to in vivo. In this pursuit the ability to assess the cell type specific response is imperative. Herein, we report a novel approach towards resolving each specific cell type of a multi-cellular model representing the human lung epithelial tissue barrier via multi-colour flow cytometry (FACS). We proved via ≤ five-colour FACS that the manipulation of this in vitro model allowed each cell type to be resolved with no impact upon cell viability. Subsequently, four-colour FACS verified the ability to determine the biochemical effect (e.g. oxidative stress) of each specific cell type. This technique will be vital in gaining information upon cellular mechanics when using next-level, multi-cellular in vitro strategies.

Cellular uptake and cell-to-cell transfer of polyelectrolyte microcapsules within a triple co-culture system representing parts of the respiratory tract

Abstract Polyelectrolyte multilayer microcapsules around 3.4 micrometers in diameter were added to epithelial cells, monocyte-derived macrophages, and dendritic cells in vitro and their uptake kinetics were quantified. All three cell types were combined in a triple co-culture model, mimicking the human epithelial alveolar barrier. Hereby, macrophages were separated in a three-dimensional model from dendritic cells by a monolayer of epithelial cells. While passing of small nanoparticles has been demonstrated from macrophages to dendritic cells across the epithelial barrier in previous studies, for the micrometer-sized capsules, this process could not be observed in a significant amount. Thus, this barrier is a limiting factor for cell-to-cell transfer of micrometer-sized particles.

Culture of human alveolar epithelial type II cells by sprouting

BackgroundType II alveolar epithelial cells (AT2) play a pivotal role in maintaining the integrity and function of the alveoli. Only recently, the role of impaired epithelial repair mechanisms after injury in the pathogenesis of idiopathic pulmonary fibrosis has been demonstrated, and has shifted the AT2 cell in the focus of interest. Therefore, using primary human AT2 cells instead of cell lines for in vitro experiments has become desirable. Several groups have developed methods to isolate human AT2 cells applying tissue digestion and consecutive filtration in their protocols. Here we present a technique to isolate primary human AT2 cells by sprouting directly from peripheral human lung tissue.MethodsEpithelial cell cultures were established from lung tissue obtained from patients undergoing diagnostic or therapeutic video-assisted thoracoscopic surgery or undergoing flexible bronchoscopy with transbronchial biopsy.Lung tissue was cut into small pieces and those were placed into cell culture flasks containing supplemented epithelial growth medium for cell sprouting. Cells were characterized by immunofluorescence stainings for E-cadherin, pan-cytokeratin, surfactant protein C (SP-C), and for lysotracker; fluorescent surfactant associated protein B (SP-B) uptake and secretion was assessed by live cell imaging; RNA levels of SP-A, SP-B, SP-C, and SP-D were determined by real-time PCR; Electron microscopy was used to search for the presence of lamellar bodies.ResultsSprouting of cells started two to four days after the start of culture. Epithelial differentiation was confirmed by positive staining for E-cadherin and pan-cytokeratin. Further characterization demonstrated positivity for the AT2 cell marker SP-C and for lysotracker which selectively labels lamellar bodies in cultured AT2 cells. The up-take and release of SP-B, a mechanism described for AT2 cells only, was demonstrated by live cell imaging. Real-time RT-PCR showed mRNA expression of all four surfactant proteins with highest levels for SP-B. The presence of lamellar bodies was demonstrated by electron microscopy.ConclusionsThis study describes a novel method for isolating AT2 cells from human adult lung tissue by sprouting. The characterization of the cultured AT2 cells complies with current criteria for an alveolar type 2 cell phenotype. Compared to current protocols for the culture of AT2 cells, isolating the cells by sprouting is simple, avoids proteolytic tissue digestion, and has the advantage to be successful even from as few tissue as attained from a transbronchial forceps biopsy.