A Bayesian regression tree approach to identify the effect of nanoparticles' properties on toxicity profiles

We introduce a Bayesian multiple regression tree model to characterize relationships between physico-chemical properties of nanoparticles and their in-vitro toxicity over multiple doses and times of exposure. Unlike conventional models that rely on data summaries, our model solves the low sample size issue and avoids arbitrary loss of information by combining all measurements from a general exposure experiment across doses, times of exposure, and replicates. The proposed technique integrates Bayesian trees for modeling threshold effects and interactions, and penalized B-splines for dose- and time-response surface smoothing. The resulting posterior distribution is sampled by Markov Chain Monte Carlo. This method allows for inference on a number of quantities of potential interest to substantive nanotoxicology, such as the importance of physico-chemical properties and their marginal effect on toxicity. We illustrate the application of our method to the analysis of a library of 24 nano metal oxides.Comment: Published at http://dx.doi.org/10.1214/14-AOAS797 in the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

A Molecular-Rotor Device for Nonvolatile High-Density Memory Applications

A novel memory device based on an electrically driven molecular rotor was fabricated and demonstrated to have bistable switching effects. The device showed an on/off ratio of approximately 10^4, a read window of about 2.5 V, and retention performance of greater than 10^4 s. The analysis of the device I–V characteristics suggests the source of the observed switching effects to be the redox-induced ligand rotation around the copper metal center, which is consistent with the observed temperature dependence of the switching behavior. This organic monolayer device holds a potential for nonvolatile high-density memory applications due to its scalability and reduced cost

Room temperature negative differential resistance of a monolayer molecular rotor device

An electrically driven molecular rotor device comprised of a monolayer of redox-active ligated copper compounds sandwiched between a gold electrode and a highly doped P+Si substrate was fabricated. Current-voltage spectroscopy revealed a temperature-dependent negative differential resistance (NDR) associated with the device. Time-dependent density functional theory suggests the source of the observed NDR to be redox-induced ligand rotation around the copper metal center, an explanation consistent with the proposed energy diagram of the device. An observed temperature dependence of the NDR behavior further supports this hypothesis

Multiply Doped Nanostructured Silicate Sol–Gel Thin Films: Spatial Segregation of Dopants, Energy Transfer, and Distance Measurements

Abstract: Physical and chemical strategies that place designed molecules in spatially separated regions of surfactant-templated mesostructured silicate thin films are used to prepare films containing rhodamine 6G (R6G), lanthanide complexes, and both simultaneously. Fluorescence and photoexcitation spectra of R6G in amorphous and structured thin films show that it is located inside the surfactant micelles of structured thin films. A silylated ligand that binds lanthanides condenses to form part of the silica framework and causes the lanthanide to localize in the silica. Luminescence and photoexcitation spectra show that energy transfer from the metal complex to R6G occurs in the films. R6G quenches Tb emission in a concentrationdependent manner. Energy transfer efficiency is calculated using the Tb luminescence lifetime, and this quantity is used to calculate the distance between Tb and R6G with the aid of Fö rster theory

Enzyme-Responsive Snap-Top Covered Silica Nanocontainers

Mesoporous silica nanoparticles, capable of storing a payload of small molecules and releasing it following specific catalytic activation by an esterase, have been designed and fabricated. The storage and release of the payload is controlled by the presence of [2]rotaxanes, which consist of tri(ethylene glycol) chains threaded by α-cyclodextrin tori, located on the surfaces of the nanoparticles and terminated by a large stoppering group. These modified silica nanoparticles are capable of encapsulating guest molecules when the [2]rotaxanes are present. The bulky stoppers, which serve to hold the tori in place, are stable under physiological conditions but are cleaved by the catalytic action of an enzyme, causing dethreading of the tori and release of the guest molecules from the pores of the nanoparticles. These snap-top covered silica nanocontainers (SCSNs) are prepared by a modular synthetic method, in which the stoppering unit, incorporated in the final step of the synthesis, may be changed at will to target the response of the system to any of a number of hydrolytic enzymes. Here, the design, synthesis, and operation of model SCSNs that open in the presence of porcine liver esterase (PLE) are reported. The empty pores of the silica nanoparticles were loaded with luminescent dye molecules (rhodamine B), and stoppering units that incorporate adamantyl ester moieties were then attached in the presence of α-cyclodextrin using the copper-catalyzed azide−alkyne cycloaddition (CuAAC), closing the SCSNs. The release of rhodamine-B from the pores of the SCSN, following PLE-mediated hydrolysis of the stoppers, was monitored using fluorescence spectroscopy