Miriam O. P. Krause

Metamemory adjustments over time in adults with and without traumatic brain injury

Primary objective: This study explored whether adults with and without traumatic brain injury (TBI) adjust their judgements of learning (JOLs) over the course of a verbal learning task. Research design: Regression analyses were performed of JOLs and recall over time, for both group means and individual performance. Procedures: Twenty adults with TBI and 16 healthy controls studied lists of noun-pairs, making Likert scale JOLs for each item during the study phase. Half of the JOLs were made immediately following item study; the other half after several minutes delay. Recall was tested for each list after all JOLs were complete. Outcomes: Analyses revealed significant differences between participants with TBI and controls in how JOLs changed over time. As a group, TBI survivors increased JOLs over the course of the learning experiment in the delayed condition, whereas the control group decreased JOL predictions in the immediate condition. Conclusions: These results support previous work showing that metamemory abilities of adults with TBI are heterogeneous, but show some differences from those of healthy adults. Possible explanations are derived from Koriats findings that, with practice, individuals tend to shift toward basing metamemory predictions on mnemonic cues rather than cues intrinsic to task items.

Research highlights: unveiling the mechanisms underlying nanoparticle-induced ROS generation and oxidative stress

The field of nanotoxicology has a long-tested hypothesis, supported by a significant body of evidence, that nanoparticle-induced reactive oxygen species (ROS) lead to oxidative stress in biological systems. Within this paradigm, it is critical to fundamentally understand the underpinning mechanisms of nanoparticle ROS production and the corresponding oxidative stress they induce. This Highlight is focused on four recent articles on this topic. The first highlighted work investigated ROS generation from various silica nanoparticle surfaces and demonstrated that porosity and surface functionalization are key factors influencing ROS generation and nanoparticle toxicity. The second article demonstrated plasmon-mediated ROS production via hot electron production on gold nanocage surfaces under near-infrared irradiation. The third highlighted work correlated electronic properties of metal oxide nanoparticles to ROS generation, and built a quantitative linear relationship between ROS generation and antibacterial activity. Finally, the fourth study provided insights regarding protein signatures and pathways sensitive to oxidative stress in macrophage cells using a redox proteomic approach. Together, these four reports reveal mechanisms underlying nanoparticle-induced ROS generation and the resulting cellular oxidative stress.

Supporting the literacy skills of adolescents with traumatic brain injury.

Traumatic brain injury (TBI) can affect developmental trajectories as well as language, attention, memory, executive functions, and other cognitive skills related to literacy. Literacy demands change through adolescence and into young adulthood, with academic literacy demands increasing and vocational literacy demands being introduced. Speech-language pathology services must evolve with the literacy needs of each client. This article discusses assessment and treatment approaches designed for adolescents with TBI and recommendations for adapting literacy interventions from the learning disabilities literature. Through proper assessment and intervention, speech-language pathologists can have a meaningful impact on the academic and vocational literacy needs of adolescents with TBI.

Psychometric properties of the college survey for students with brain injury: individuals with and without traumatic brain injury.

Abstract Purpose: The psychometric properties of the college challenges sub-set from The College Survey for Students with Brain Injury (CSS-BI) were investigated with adults with and without traumatic brain injury (TBI). Methods: Adults with and without TBI completed the CSS-BI. A sub-set of participants with TBI were interviewed, intentional and convergent validity were investigated, and the internal structure of the college challenges was analysed with exploratory factor analysis/principle component analysis. Results: Respondents with TBI understood the items describing college challenges with evidence of intentional validity. More individuals with TBI than controls endorsed eight of the 13 college challenges. Those who reported more health issues endorsed more college challenges, demonstrating preliminary convergent validity. Cronbach’s alphas of >0.85 demonstrated acceptable internal reliability. Factor analysis revealed a four-factor model for those with TBI: studying and learning (Factor 1), time management and organization (Factor 2), social (Factor 3) and nervousness/anxiety (Factor 4). This model explained 72% and 69% of the variance for those with and without TBI, respectively. Conclusion: The college challenges sub-set from the CSS-BI identifies challenges that individuals with TBI face when going to college. Some challenges were related to two factors in the model, demonstrating the inter-connections of these experiences.

Research highlights: applications of life-cycle assessment as a tool for characterizing environmental impacts of engineered nanomaterials

The upstream and downstream environmental impacts of engineered nanomaterials (ENMs) are increasingly realized, and have motivated research to advance promising applications while precluding adverse impacts. Life-cycle assessment (LCA) is a comprehensive tool that considers the entire lifetime of a material, product or process—from raw material acquisition to end-of-life—and can be used to characterize these impacts as various environmental and human health categories. The motivation for this highlight stems from the curiosity of experimentalists and theorists researching the environmental and biological impacts that could result from widespread implementation of nanotechnology. In particular, we are motivated to identify how our research on the nano–bio interface can liaise with the nano-LCA community to advance nano-LCA in a safe and sustainable manner. As such, this highlight focuses on four recent nano-LCA publications that survey across several system levels and address the topics of: (i) upstream impacts from nanoparticle synthesis, (ii) extended lifetimes through the incorporation of ENMs in paints, (iii) integration of nano-specific data into existing life-cycle models, and (iv) the establishment of a nano-specific LCA framework.

Research highlights: investigating the role of nanoparticle surface charge in nano–bio interactions

A systematic approach to predicting nanoparticle–cell interactions has become increasingly important due to the great potential that nanoparticles hold for biomedical and environmental applications. However, the quantitative description and accurate characterization of nanomaterial surface chemistry (e.g., ligand distribution and surface charge) is nontrivial due to the sheer complexity of both the nanoparticle mechanisms and the biological environments with which they interact. The authors of this highlight, including both experimental and theoretical chemists, were motivated to explore the current gap in the fundamental knowledge about nanoparticle surface charge-dependent interactions across a variety of biological systems. The highlight focuses on three recent publications that survey the effects of nanoparticle surface charge across several bio-system complexities, addressing: (i) ligand-coated gold nanoparticles traversing a lipid bilayer, (ii) silica nanoparticle uptake into human osteoblast cells, and (iii) the suborgan distribution of gold nanoparticles in mice.

Research highlights: examining the effect of shape on nanoparticle interactions with organisms

There are many variables that influence the toxicity of nanoparticles to organisms, such as nanoparticle size, shape, core composition, and ligand chemistry, composition, and coverage. Assessing the unique effects elicited by each of these parameters has been challenging as they impact each other. It is therefore difficult to change one parameter while keeping all other parameters constant. Here, we highlight three articles in which investigators carefully controlled as many confounding factors as possible while assessing the impacts of nanoparticle shape on their interactions with organisms. One study revealed shape-dependent effects of silver nanoparticles on the annual ryegrass, Lolium multiflorum. Another study identified shape-dependent effects of lanthanide-doped NaYF4 nanoparticles on nanoparticle association with a model cell membrane and on the cellular uptake and toxicity in selected cell lines. Finally, we highlight a study that used a coarse grain computational approach to effectively keep other parameters constant while determining the effect of shape on nanoparticle endocytosis.

Research highlights: speciation and transformations of silver released from Ag NPs in three species

Antimicrobial silver nanoparticles used in consumer products may be released during fabrication, during product use, or after disposal and may reach terrestrial and aquatic ecosystems, prompting concern about their potential to adversely impact the environment (Benn and Westerhoff, Environ. Sci. Technol., 2008, 42, 4133, DOI: 10.1021/es7032718). Although the toxicity of pristine silver nanoparticles is well studied and understood, silver nanoparticles can undergo transformation during release and in engineered and natural environments. The speciation of silver after release must therefore be explored to deepen understanding of the potential impact of these nanoparticles on the environment. Herein, we highlight three articles which use highly sensitive analytical techniques to define, and in some cases map, silver speciation in situ after exposure to organisms of varying size and complexity. First, we highlight research by Leonardo et al. which explores the transformations of silver acted upon by a microalgae species that is a candidate for heavy metal remediation in water. Next, we highlight research by Stegemeier et al. quantifying and mapping the speciation of silver in alfalfa after exposure to several silver sources, including two silver-based nanoparticles. Finally, we discuss work by Wang et al. on silver speciation in human monocyte cells as observed by synchrotron radiation techniques which leads to mechanistic insights on cytotoxicity.

Research highlights: comparing the biological response of nanoparticle solid solutions

Scientific advances in the field of nanotechnology have led to the wide-scale use of engineered nanomaterials, resulting in an increased demand to understand the biological impact of these materials when released to the environment. This demand has led to an evolving field of science focused specifically on interactions at the nano–bio interface, where researchers investigate the biological responses of a wide range of organisms to engineered nanomaterials. The majority of investigations into the nano–bio interface are focused on the biological response of single-phase nanomaterials, yet engineered nanomaterials are often more complex than a single-phase nanomaterial. Many engineered nanomaterials can be described as solid solutions (or alloys) where multiple types of cations (and/or anions) are present in different ratios, and properties such as spin state, valence charge, and lattice constant can be tuned by changing the atomic composition. Research at the nano–bio interface must go beyond investigating the biological response of single-phase nanomaterials and include a systematic approach to predict how the biological interactions of nanomaterial solid solutions can be controlled via systematic changes in chemical composition. In this highlight, we focus on four publications that use a range of experimental methods to delineate the interactions of solid solutions composed of either Au metal or ZnO solid oxide on a variety of organisms. The first highlighted work tunes the composition of Au–Pt nanoparticles for antibacterial activity. The second article investigates the reprotoxicity of Au–Ag nanoparticles. The third highlighted work shows that Fe–ZnO nanoparticles demonstrate a reduced toxicity when compared to ZnO. Finally, the fourth study presents an in silico design strategy for cancer specific Fe–ZnO nanoparticles. Together, these four studies reveal the wide range of chemical compositions that are accessible in nanomaterial solid solutions and demonstrate that careful modifications in compositional phase space can result in selective nano–bio interactions.