Nanoparticles: Properties, applications and toxicities

DLS and zeta potential - What they are and what they are not?

The emergence of publications on extracellular RNA (exRNA) and extracellular vesicles (EV) has highlighted the potential of these molecules and vehicles as biomarkers of disease and therapeutic targets. These findings have created a paradigm shift, most prominently in the field of oncology, prompting expanded interest in the field and dedication of funds for EV research. At the same time, understanding of EV subtypes, biogenesis, cargo and mechanisms of shuttling remains incomplete. The techniques that can be harnessed to address the many gaps in our current knowledge were the subject of a special workshop of the International Society for Extracellular Vesicles (ISEV) in New York City in October 2012. As part of the “ISEV Research Seminar: Analysis and Function of RNA in Extracellular Vesicles (evRNA)”, 6 round-table discussions were held to provide an evidence-based framework for isolation and analysis of EV, purification and analysis of associated RNA molecules, and molecular engineering of EV for therapeutic intervention. This article arises from the discussion of EV isolation and analysis at that meeting. The conclusions of the round table are supplemented with a review of published materials and our experience. Controversies and outstanding questions are identified that may inform future research and funding priorities. While we emphasize the need for standardization of specimen handling, appropriate normative controls, and isolation and analysis techniques to facilitate comparison of results, we also recognize that continual development and evaluation of techniques will be necessary as new knowledge is amassed. On many points, consensus has not yet been achieved and must be built through the reporting of well-controlled experiments. Keywords: extracellular vesicle; exosome; microvesicle; standardization; isolation (Published: 27 May 2013) Citation: Journal of Extracellular Vesicles 2013, 2 : 20360 - http://dx.doi.org/10.3402/jev.v2i0.20360

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Standardization of sample collection, isolation and analysis methods in extracellular vesicle research

Review of bioactive glass: from Hench to hybrids.

Nanomedicine, the application of nanotechnology to medicine, enabled the development of nanoparticle therapeutic carriers. These drug carriers are passively targeted to tumors through the enhanced permeability and retention effect, so they are ideally suited for the delivery of chemotherapeutics in cancer treatment. Indeed, advances in nanomedicine have rapidly translated into clinical practice. To date, there are five clinically approved nanoparticle chemotherapeutics for cancer and many more under clinical investigation. In this review, we discuss the various nanoparticle drug delivery platforms and the important concepts involved in nanoparticle drug delivery. We also review the clinical data on the approved nanoparticle therapeutics as well as the nanotherapeutics under clinical investigation.

Nanoparticle Delivery of Cancer Drugs

Embryonic stem cells (ESC) are both a potential source of cells for tissue replacement therapies and an accessible tool to model early embryonic development. Chemical factors such as soluble growth factors and insoluble components of the extracellular matrix are known to affect the differentiation of murine ESCs. However, there is also evidence to suggest that undifferentiated cells can both sense the mechanical properties of their environment and differentiate accordingly. By growing ESCs on flexible polydimethylsiloxane substrates with varying stiffness, we tested the hypothesis that substrate stiffness can influence ESC differentiation. While cell attachment was unaffected by the stiffness of the growth substrate, cell spreading and cell growth were all increased as a function of substrate stiffness. Similarly, several genes expressed in the primitive streak during gastrulation and implicated in early mesendoderm differentiation, such as Brachyury, Mixl1 and Eomes, were upregulated in cell cultures on stiffer compared to softer substrates. Finally, we demonstrated that osteogenic differentiation of ESCs was enhanced on stiff substrates compared to soft substrates, illustrating that the mechanical environment can play a role in both early and terminal ESC differentiation. Our results suggest a fundamental role for mechanosensing in mammalian development and illustrate that the mechanical environment should be taken into consideration when engineering implantable scaffolds or when producing therapeutically relevant cell populations in vitro.

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Substrate stiffness affects early differentiation events in embryonic stem cells.

Cancer accounted for 13% of all deaths worldwide in 2005. Although early detection is critical for the successful treatment of many cancers, there are sensitivity limitations associated with current detection methodologies. Furthermore, many traditional anticancer drug treatments exhibit limited efficacy and cause high morbidity. The unique physical properties of nanoscale materials can be utilized to produce novel and effective sensors for cancer diagnosis, agents for tumor imaging, and therapeutics for cancer treatment. Functionalizing inorganic nanoparticles with biocompatible polymers and natural or rationally designed biomolecules offers a route towards engineering responsive and multifunctional composite systems. Although only a few such innovations have reached human clinical trial to date, nanocomposite materials based on functionalized metal and semiconductor nanoparticles promise to transform the way cancer is diagnosed and treated. This review summarizes the current state-of-the-art in the development of inorganic nanocomposites for cancer-related applications.

Engineering Nanocomposite Materials for Cancer Therapy

Nature has evolved mechanisms to create a diversity of specialized materials through nanoscale organization. Inspired by nature, hybrid materials are designed with highly tailorable properties, which are achieved through careful control of their nanoscale interactions. These novel materials, based on a silica-gelatin hybrid system, have the potential to serve as a platform technology for human tissue regeneration. Covalent interactions between the inorganic and organic constituents of the hybrid are essential to enable the precise control of mechanical and dissolution properties. Furthermore, hybrid scaffold porosity is found to highly influence mechanical properties, to the extent where scaffolds of particular strength could be specified based on their porosity. The hybrids also demonstrate a non-cytotoxic effect when mesenchymal stem cells are cultured on the material. Cytoskeletal proteins of the cells are imaged using actin and vimentin staining. It is envisaged these hybrid materials will find a diverse application in both hard and soft tissue regenerating scaffolds.

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Silica-gelatin hybrids with tailorable degradation and mechanical properties for tissue regeneration

The accurate characterization of submicrometer and nanometer sized particles presents a major challenge in the diverse applications envisaged for them including cosmetics, biosensors, renewable energy, and electronics. Size is one of the principal parameters for classifying particles and understanding their behavior, with other particle characteristics usually only quantifiable when size is accounted for. We present a comparative study of emerging and established techniques to size submicrometer particles, evaluating their sizing precision and relative resolution, and demonstrating the variety of physical principles upon which they are based, with the aim of developing a framework in which they can be compared. We used in-house synthesized Stober silica particles between 100 and 400 nm in diameter as reference materials for this study. The emerging techniques of scanning ion occlusion sensing (SIOS), differential centrifugal sedimentation (DCS), and nanoparticle tracking analysis (NTA) were compared to the established techniques of transmission electron microscopy (TEM), scanning mobility particle sizing (SMPS), and dynamic light scattering (DLS). The size distributions were described using the mode, arithmetic mean, and standard deviation. Uncertainties associated with the six techniques were evaluated, including the statistical uncertainties in the mean sizes measured by the single-particle counting techniques. Q-Q plots were used to analyze the shapes of the size distributions. Through the use of complementary techniques for particle sizing, a more complete characterization of the particles was achieved, with additional information on their density and porosity attained.

Emerging Techniques for Submicrometer Particle Sizing Applied to Stöber Silica

The contact of nanoparticles with biological fluids such as serum results in rapid adsorption of proteins at the nanoparticle surface in a layer known as the “protein corona”. Protein coatings modify and control the behavior of the nanoparticles potentially altering the aggregation state and cellular response, which may influence their fate and hazard to human health. Cells are likely to interact with the protein interface rather than with bare surface; therefore it is important to study the protein layer and develop appropriate measurement tools. In this study we investigate how adsorbed proteins from serum affect the size and the surface charge of plain and aminated silica nanoparticles. Particle size and size distributions in buffer and serum-based biological media were studied using tunable resistive pulse sensing (TRPS), as well as differential centrifugal sedimentation (DCS) and dynamic light scattering (DLS). Average and single particle ζ-potentials (related to surface charge) were also measured by...

Caterina Minelli

Papers

Substrate stiffness affects early differentiation events in embryonic stem cells.

Engineering Nanocomposite Materials for Cancer Therapy

Silica-gelatin hybrids with tailorable degradation and mechanical properties for tissue regeneration

Emerging Techniques for Submicrometer Particle Sizing Applied to Stöber Silica

Size and ζ-Potential Measurement of Silica Nanoparticles in Serum Using Tunable Resistive Pulse Sensing