Nanoparticles: Properties, applications and toxicities

s, and 360 patents, and edited 12 books. He has also received over 80 major awards including the Gairdner Foundation International Award, Lemelson-MIT prize, ACS’s Applied Polymer Science and Polymer Chemistry Awards, AICHE’s Professional Progress, Bioengineering, Walker and Stine Materials Science and Engineering Awards. In 1989, Dr. Langer was elected to the Institute of Medicine of the National Academy of Sciences, and in 1992 he was elected to both the National Academy of Engineering and the National Academy of Sciences. He is the only active member of all three National Academies. Kevin Shakesheff was born in Ashington, Northumberland, U.K., in 1969. He received his Bacheclor of Pharmacy degree from the University of Nottingham in 1991 and a Ph.D. from the same institution in 1995. In 1996 he became a NATO Postdoctoral Fellow at MIT, Department of Chemical Engineering. He is currently an EPSRC Advanced Fellow at the School of Pharmaceutical Sciences, The University of Nottingham. His research group investigates new methods of engineering polymer surfaces and the application of these engineered materials in drug delivery and tissue engineering. 3182 Chemical Reviews, 1999, Vol. 99, No. 11 Uhrich et al.

Polymeric Systems for Controlled Drug Release

1: Magnetic Particles: Preparation, Properties and Applications: M. Ozaki. 2: Maghemite (gamma-Fe2O3): A Versatile Magnetic Colloidal Material C.J. Serna, M.P. Morales. 3: Dynamics of Adsorption and Oxidation of Organic Molecules on Illuminated Titanium Dioxide Particles Immersed in Water M.A. Blesa, R.J. Candal, S.A. Bilmes. 4: Colloidal Aggregation in Two-Dimensions A. Moncho-Jorda, F. Martinez-Lopez, M.A. Cabrerizo-Vilchez, R. Hidalgo Alvarez, M. Quesada-PMerez. 5: Kinetics of Particle and Protein Adsorption Z. Adamczyk.

Surface and Colloid Science

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

X-ray photoelectron spectroscopy: Towards reliable binding energy referencing

The aim of this paper is twofold: first to report on the lateral and vertical characterisation of a surface chemical gradient of carboxylic-acid functionality and second, to demonstrate the use of said gradient to probe the passive adsorption of immunoglobulin G (IgG) as a function of the density of surface carboxylic-acid groups. A surface chemical gradient of carboxylic-acid functionality was fabricated by the plasma copolymerisation of octadiene (OD) and acrylic acid (AA). The plasma-polymerised gradient was over 12 mm, with 2 mm of plasma-polymerised OD at one end and 2 mm of plasma-polymerised AA at the other. By means of linescan angle resolved x-ray photoelectron spectroscopy (ARXPS) it is shown precisely how acid functionality varies from the 2 mm position (OD end) on the gradient to the 10 mm position (AA end). By recording data from 16 angles at each of the 25 sampling points along the gradient, it is shown that the surface gradient also changes vertically, most notably in the thickness of the plasma polymer. At the OD end the plasma-polymerised layer is 6.3 nm thick, while at the AA end the plasma-polymerised layer is 5 nm. More subtle changes in chemistry through the plasma-polymerised layer are shown at the 7.5 and 10 mm points. An identical gradient is used to probe IgG adsorption along the length of the gradient. ARXPS is used to monitor the nitrogen Is (N1s) signal at 25 points, the N1s signal being unique to adsorbed IgG. It is demonstrated that IgG adsorbs in far greater amount (IgG per unit area) at the OD end, and the amount of adsorbed IgG decreases along the length of the gradient. It is estimated that >200 ng/cm 2 adsorbed at the OD, while at the AA the amount adsorbed was <20 ng/cm 2 .

ARXPS characterisation of plasma polymerised surface chemical gradients

We study thin films of semi-crystalline regioregular poly(3-hexylthiophene) (RR-P3HT) and amorphous regiorandom P3HT (RRa-P3HT) in blends with [6,6]-phenyl C61 butyric acid methyl ester (PCBM). Ultraviolet and (angle-resolved) X-ray photoelectron spectroscopy techniques together with absorption, photoluminescence and optical microscopy were used to measure electronic energy levels, vertical chemical compositions and optical properties of these films. We find that ordering the P3HT chains raises the highest occupied molecular orbital (HOMO) energy level of P3HT thin films (reducing ionization potential) and that the ordering of P3HT chains occurs preferentially at the film−air interface in RR-P3HT:PCBM thin films. This leads to a vertical phase separation between P3HT and PCBM molecules, which may be undesirable for conventional P3HT:PCBM solar cells.

Effect of Crystallization on the Electronic Energy Levels and Thin Film Morphology of P3HT:PCBM Blends

XPS and AFM surface studies of solvent-cast PS/PMMA blends

A simple approach to estimating the detection limits of XPS for any element in any elemental matrix is presented, using the intensity of the background at the expected position for the photoelectron peak to be detected. The approach has been extended to estimate the detection limit for all elements from lithium to bismuth in a similar range of elemental matrices. Using a number of assumptions, it is possible to obtain a reasonable estimate the background intensity at any electron kinetic energy in the XPS spectrum of an element. Therefore a detection limit for an arbitrary element in that matrix can be estimated. The results show that, although most elements are detectable at about the 1 at.% to 0.1 at.% level, for heavy elements in a light element matrix the detection limit can be better than 0.01 at.%, whereas for light elements in a heavy element matrix, detection limits above 10 at.% are not uncommon. Two charts detailing the detection limits for all combinations of trace and matrix elements from lithium (Z = 3) to bismuth (Z = 83) are provided for Al K and Mg K X-ray sources using a typical hemispherical analyser instrument which provides 106 counts eV for the Ag 3d5/2 peak from pure silver. These detection limits can be scaled to estimate the detection limits for any given instrument and operating conditions if the intensity of the Ag 3d5/2 peak from pure silver is known.

Detection limits in XPS for more than 6000 binary systems using Al and Mg Kα X‐rays

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.

Alexander G. Shard

Papers

ARXPS characterisation of plasma polymerised surface chemical gradients

Effect of Crystallization on the Electronic Energy Levels and Thin Film Morphology of P3HT:PCBM Blends

XPS and AFM surface studies of solvent-cast PS/PMMA blends

Detection limits in XPS for more than 6000 binary systems using Al and Mg Kα X‐rays

Emerging Techniques for Submicrometer Particle Sizing Applied to Stöber Silica