Tanya S. Hauck

Through the use of various layer-by-layer polyelectrolyte (PE) coating schemes, such as the common poly(diallyldimethylammonium chloride)-poly(4-styrenesulfonic acid) (PDADMAC-PSS) system, the mammalian cellular uptake of gold nanorods can be tuned from very high to very low by manipulating the surface charge and functional groups of the PEs. The toxicity of these nanorods is also examined. Since the PE coatings are individually toxic, the toxicity of nanorods coated in these PEs is measured and cells are found to be greater than 90% viable in nearly all cases, even at very high concentrations. This viability assay may not be a complete indicator of toxicity, and thus gene-expression analysis is used to examine the molecular changes of cells exposed to PDADMAC-coated nanorods, which enter cells at the highest concentrations. Indicators of cell stress, such as heat-shock proteins, are not significantly up- or down-regulated following nanorod uptake, which suggests that PDADMAC-coated gold nanorods have negligible impact on cell function. Furthermore, a very low number of genes experience any significant change in expression (0.35% of genes examined). These results indicate that gold nanorods are well suited for therapeutic applications, such as thermal cancer therapy, due to their tunable cell uptake and low toxicity.

Quantum dots have potential in biomedical applications, but concerns persist about their safety. Most toxicology data is derived from in vitro studies and may not reflect in vivo responses. Here, an initial systematic animal toxicity study of CdSe-ZnS core-shell quantum dots in healthy Sprague-Dawley rats is presented. Biodistribution, animal survival, animal mass, hematology, clinical biochemistry, and organ histology are characterized at different concentrations (2.5-15.0 nmol) over short-term (<7 days) and long-term (>80 days) periods. The results show that the quantum dot formulations do not cause appreciable toxicity even after their breakdown in vivo over time. To generalize the toxicity of quantum dots in vivo, further investigations are still required. Some of these investigations include the evaluation of quantum dot composition (e.g., PbS versus CdS), surface chemistry (e.g., functionalization with amines versus carboxylic acids), size (e.g., 2 versus 6 nm), and shape (e.g., spheres versus rods), as well as the effect of contaminants and their byproducts on biodistribution behavior and toxicity. Combining the results from all of these studies will eventually lead to a conclusion regarding the issue of quantum dot toxicity.

The heat produced by optically excited gold nanorods is used to augment the chemotherapeutic agent cisplatin in killing tumor cells. This combined therapy kills 78% more cells than cisplatin alone, suggesting a synergistic interaction between these treatments. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

The COVID-19 pandemic disproportionately disrupts the daily lives of marginalized populations. Persons with substance use disorders are a particularly vulnerable population because of their unique social and health care needs. They face significant harm from both the pandemic itself and its social and economic consequences, including marginalization in health care and social systems. Hence, we discuss: (1) why persons with substance use disorders are at increased risk for infection with COVID-19 and a severe illness course; (2) anticipated adverse consequences of COVID-19 in persons with substance use disorders; (3) challenges to health care delivery and substance use treatment programs during and after the COVID-19 pandemic; and (4) the potential impact on clinical research in substance use disorders. We offer recommendations for clinical, public health, and social policies to mitigate these challenges and to prevent negative outcomes.