Lisa A. DeLouise

In Vivo Skin Penetration of Quantum Dot Nanoparticles in the Murine Model: The Effect of UVR

Ultraviolet radiation (UVR) has widespread effects on the biology and integrity of the skin barrier. Research on the mechanisms that drive these changes, as well as their effect on skin barrier function, has been ongoing since the 1980s. However, no studies have examined the impact of UVR on nanoparticle skin penetration. Nanoparticles (NP) are commonly used in sunscreens and other cosmetics, and since consumer use of sunscreen is often applied to sun damaged skin, the effect of UVR on NP skin penetration is a concern due to potential toxicity. In this study, we investigate NP skin penetration by employing an in vivo semiconductor quantum dot nanoparticle (QD) model system. This model system improves NP imaging capabilities and provides additional primary interest due to widespread and expanding use of QD in research applications and manufacturing. In our experiments, carboxylated QD were applied to the skin of SKH-1 mice in a glycerol vehicle with and without UVR exposure. The skin collection and penetration patterns were evaluated 8 and 24 h after QD application using tissue histology, confocal microscopy, and transmission electron microscopy (TEM) with EDAX analysis. Low levels of penetration were seen in both the non-UVR exposed mice and the UVR exposed mice. Qualitatively higher levels of penetration were observable in the UVR exposed mice. These results are the first for in vivo QD skin penetration, and provide important insight into the ability of QD to penetrate intact and UVR compromised skin barrier. Our findings raise concern that NP of similar size and surface chemistry, such as metal oxide NP found in sunscreens, may also penetrate UV damaged skin.

Effect of incidence kinetic energy and surface coverage on the dissociative chemisorption of oxygen on W(110)

The dissociative chemisorption of oxygen on W(110) has been studied using molecular beam techniques. Chemisorption probabilities have been measured as a function of incidence angle, θi, and kinetic energy, Ei, and of surface coverage and temperature. In addition, angular scattering distributions have been measured for a range of conditions and LEED has been used to examine surface structure. The initial (zero coverage limit) sticking probability is found to depend strongly on the incidence energy, scaling with En=Ei cos2 θi. This probability is ∼10% at En =0.1 eV, rising to essentially unity above En =0.4 eV. At half a monolayer coverage of atomic oxygen, the sticking probability is close to zero up to a threshold of ∼0.25 eV, above which it rises to over 50% by 1.3 eV. In most cases, the sticking probability is found to fall roughly linearly with increasing surface coverage. However, a less‐than‐linear fall‐off is observed for En ≥1 eV and for En ≤0.03 eV, the sticking probability actually rises with inc...

Applications of Nanotechnology in Dermatology

What are nanoparticles and why are they important in dermatology? These questions are addressed by highlighting recent developments in the nanotechnology field that have increased the potential for intentional and unintentional nanoparticle skin exposure. The role of environmental factors in the interaction of nanoparticles with skin and the potential mechanisms by which nanoparticles may influence skin response to environmental factors are discussed. Trends emerging from recent literature suggest that the positive benefit of engineered nanoparticles for use in cosmetics and as tools for understanding skin biology and curing skin disease outweigh potential toxicity concerns. Discoveries reported in this journal are highlighted. This review begins with a general introduction to the field of nanotechnology and nanomedicine. This is followed by a discussion of the current state of understanding of nanoparticle skin penetration and their use in three therapeutic applications. Challenges that must be overcome to derive clinical benefit from the application of nanotechnology to skin are discussed last, providing perspective on the significant opportunity that exists for future studies in investigative dermatology.

Adsorption and desorption of no from Rh{111} and Rh{331} surfaces

Abstract The adsorption and desorption chemistry of NO on the clean Rh{111} and Rh{331} single crystal surfaces was followed with SIMS, XPS, and LEED. Results suggest dissociative NO adsorption occurs at step and/or defect sites. At saturation coverage there was ∼ 10 times more dissociated species on the Rh{331} surface at 300 K than on the Rh{111} surface. On both surfaces two molecular states of NOads have been identified as β1, and β2 which possess different chemical reactivity. Under the condition of saturation coverage the β1 and β2 states are populated on the Rh{111} surface in a different proportion than on the Rh{331} surface. Further, their population on both surfaces is coverage and temperature dependent. When the sample is heated to desorb the saturation overlayer formed on the Rh{111} and Rh{331} crystal surfaces, approximately 50% of the overlayer is found to desorb below ≃ 400 K primarily from the β2 state, molecularly as NO(g). Between 300 and 400 K the β1 state dissociates as binding sites necessary to coordinate Nads and Oads are freed by desorption of NO(g).

Surface chemistry on semiconductors studied by molecular-beam reactive scattering

Abstract This Report reviews the use of molecular-beam reactive scattering to study the surface reactions of gas molecules on semiconductors which have relevance to microelectronic technologies. Modern semiconductor fabrication techniques rely heavily on dry processes where gas-surface reactions are the basic premise. This article focuses on the use of supersonic molecular-beam-surface scattering to study the dynamics and kinetics of surface reactions connected with the growth and etching processes on semiconductor surfaces. The discussion on growth processes covers the oxidation of silicon and germanium, the tungsten-hexafluoride-based tungsten deposition, and the organometallic chemical vapor deposition of gallium arsenide. The discussion on etching processes covers the halogen-based etching of gallium arsenide and silicon. An overview of the experimental technique and the underlying principles in surface-reaction dynamics and kinetics is included for readers in the technology area. The potential use of the molecular beams for actual semiconductor materials processing is also discussed.

Continuously perfused microbubble array for 3D tumor spheroid model

Multi-cellular tumor spheroids (MCTSs) have been established as a 3D physiologically relevant tumor model for drug testing in cancer research. However, it is difficult to control the MCTS testing parameters and the entire process is time-consuming and expensive. To overcome these limitations, we developed a simple microfluidic system using polydimethylsiloxane (PDMS) microbubbles to culture tumor spheroids under physiological flow. The flow characteristics such as streamline directions, shear stress profile, and velocity profile inside the microfluidic system were first examined computationally using a COMSOL simulation. Colo205 tumor spheroids were created by a modified hanging drop method and maintained inside PDMS microbubble cavities in perfusion culture. Cell viability inside the microbubbles was examined by live cell staining and confocal imaging. E-selectin mediated cell sorting of Colo205 and MDA-MB-231 cell lines on functionalized microbubble and PDMS surfaces was achieved. Finally, to validate this microfluidic system for drug screening purposes, the toxicity of the anti-cancer drug, doxorubicin, on Colo205 cells in spheroids was tested and compared to cells in 2D culture. Colo205 spheroids cultured in flow showed a threefold increase in resistance to doxorubicin compared to Colo205 monolayer cells cultured under static conditions, consistent with the resistance observed previously in other MCTS models. The advantages presented by our microfluidic system, such as the ability to control the size uniformity of the spheroids and to perform real-time imaging on cells in the growth platform, show potential for high throughput drug screening development.

Physicochemical factors that affect metal and metal oxide nanoparticle passage across epithelial barriers

The diversity of nanomaterials in terms of size, shape, and surface chemistry poses a challenge to those who are trying to characterize the human health and environmental risks associated with incidental and unintentional exposures. There are numerous products that are already commercially available that contain solid metal and metal oxide nanoparticles, either embedded in a matrix or in solution. Exposure assessments for these products are often incomplete or difficult due to technological challenges associated with detection and quantitation of nanoparticles in gaseous or liquid carriers. The main focus of recent research has been on hazard identification. However, risk is a product of hazard and exposure, and one significant knowledge gap is that of the target organ dose following in vivo exposures. In order to reach target organs, nanoparticles must first breach the protective barriers of the respiratory tract, gastrointestinal tract, or skin. The fate of those nanoparticles that reach physiological barriers is in large part determined by the properties of the particles and the barriers themselves. This article reviews the physiological properties of the lung, gut, and skin epithelia, the physicochemical properties of metal and metal oxide nanoparticles that are likely to affect their ability to breach epithelial barriers, and what is known about their fate following in vivo exposures.

Carbon monoxide adsorption and desorption on Rh{111} and Rh{331} surfaces

The combined techniques of X-ray Photoelectron Spectroscopy (XPS) and Secondary Ion Mass Spectrometry (SIMS) were utilized to investigate the adsorption and desorption characteristics of carbon monoxide from the initially clean Rh{111} and Rh{331} surfaces. An effective procedure was established, which reduced the bulk carbon contamination to an undetectable level. The XPS results for saturation exposures show a strong O 1s spectral region; the Rh{111} surface exhibited two peaks with binding energies at 532.1 eV and 530.7 eV, whereas for the Rh{331} surface, the peaks were at 532.1 eV and 531.2 eV. These binding energies are characteristic of molecular species bonded to two different surface binding sites. SIMS results on the CO saturated Rh{111} and Rh{331} surfaces showed strong RhCO+ and Rh2CO+ cluster ion intensities, which further substantiates the conclusion that CO molecularly adsorbs on these Rh surfaces at 300 K. Heating the CO saturated Rh{111} and Rh{331} surfaces to greater than 470 K, thermally desorbed the CO overlayer. SIMS and XPS analysis after heating showed no evidence of molecular CO or its dissociated products. Further results of this study showed that surface carbon and oxide do not diffuse into the Rh crystal bulk below the molecular CO desorption temperature. This eliminated the possibility that any dissociated products of CO had diffused into the bulk and were therefore undetected.

Angle‐resolved supersonic molecular beam study of the Cl2/GaAs{110} thermal etching reaction

Angle‐resolved supersonic molecular beam scattering and time‐of‐flight techniques (TOF) are used to probe the dynamics of the Cl2/GaAs{110} thermal etching reaction. TOF spectra are recorded for the unreacted Cl2 and the GaCl3 reaction product as a function of incident translational energy and surface temperature at various final scattering angles. Our results show that the reaction mechanism is precursor mediated. The weakly bound molecular (Cl2)ads species is a key reaction intermediate through which subsequent reaction steps occur. The reaction probability, determined by angle integration of the unreacted Cl2 flux, increases with surface temperature (Ts) reaching a plateau and decreasing slightly between Ts∼425 K and 525 K before increasing sharply again beyond 525 K. This trend is nearly independent of incident kinetic energy. Detailed analysis of the TOF spectra reveal that the dynamical origin of this effect is due in part to a change in the reaction kinetics in which Cl2 desorption competes with pr...

Label-free porous silicon immunosensor for broad detection of opiates in a blind clinical study and results comparison to commercial analytical chemistry techniques.

In this work, we evaluate for the first time the performance of a label-free porous silicon (PSi) immunosensor assay in a blind clinical study designed to screen authentic patient urine specimens for a broad range of opiates. The PSi opiate immunosensor achieved 96% concordance with liquid chromatography-mass spectrometry/tandem mass spectrometry (LC-MS/MS) results on samples that underwent standard opiate testing (n = 50). In addition, successful detection of a commonly abused opiate, oxycodone, resulted in 100% qualitative agreement between the PSi opiate sensor and LC-MS/MS. In contrast, a commercial broad opiate immunoassay technique (CEDIA) achieved 65% qualitative concordance with LC-MS/MS. Evaluation of important performance attributes including precision, accuracy, and recovery was completed on blank urine specimens spiked with test analytes. Variability of morphine detection as a model opiate target was <9% both within-run and between-day at and above the cutoff limit of 300 ng mL(-1). This study validates the analytical screening capability of label-free PSi opiate immunosensors in authentic patient samples and is the first semiquantitative demonstration of the technologys successful clinical use. These results motivate future development of label-free PSi technology to reduce complexity and cost of diagnostic testing particularly in a point-of-care setting.