Melissa A. Maurer-Jones

Toxicity of Engineered Nanoparticles in the Environment

While nanoparticles occur naturally in the environment and have been intentionally used for centuries, the production and use of engineered nanoparticles has seen a recent spike, which makes environmental release almost certain. Therefore, recent efforts to characterize the toxicity of engineered nanoparticles have focused on the environmental implications, including exploration of toxicity to organisms from wide-ranging parts of the ecosystem food webs. Herein, we summarize the current understanding of toxicity of engineered nanoparticles to representatives of various trophic levels, including bacteria, plants, and multicellular aquatic/terrestrial organisms, to highlight important challenges within the field of econanotoxicity, challenges that analytical chemists are expertly poised to address.

Assessing Nanoparticle Toxicity

Nanoparticle toxicology, an emergent field, works toward establishing the hazard of nanoparticles, and therefore their potential risk, in light of the increased use and likelihood of exposure. Analytical chemists can provide an essential tool kit for the advancement of this field by exploiting expertise in sample complexity and preparation as well as method and technology development. Herein, we discuss experimental considerations for performing in vitro nanoparticle toxicity studies, with a focus on nanoparticle characterization, relevant model cell systems, and toxicity assay choices. Additionally, we present three case studies (of silver, titanium dioxide, and carbon nanotube toxicity) to highlight the important toxicological considerations of these commonly used nanoparticles.

Toxicity of therapeutic nanoparticles

A total of six nanotherapeutic formulations are already approved for medical use and more are in the approval pipeline currently. Despite the massive research effort in nanotherapeutic materials, there is relatively little information about the toxicity of these materials or the tools needed to assess this toxicity. Recently, the scientific community has begun to respond to the paucity of information by investing in the field of nanoparticle toxicology. This review is intended to provide an overview of the techniques needed to assess toxicity of these therapeutic nanoparticles and to summarize the current state of the field. We begin with background on the toxicological assessment techniques used currently as well as considerations in nanoparticle dosing. The toxicological research overview is divided into the most common applications of therapeutic nanoparticles: drug delivery, photodynamic therapy and bioimaging. We end with a perspective section discussing the current technological gaps and promising research aimed at addressing those gaps.

Impact of TiO2 Nanoparticles on Growth, Biofilm Formation, and Flavin Secretion in Shewanella oneidensis

Understanding of nanoparticle impacts on critical bacteria functions allows us to gain a mechanistic understanding of toxicity and guides us toward design rules for creating safe nanomaterials. Herein, biofilm formation, a general bacteria function, and riboflavin secretion, a species-specific function, were monitored in Shewanella oneidensis, a metal reducing bacterium, following exposure to a variety of TiO2 nanoparticle types (synthesized, Aeroxide P25, and T-Eco). Transmission electron microscopy (TEM) images show that dosed nanoparticles are in close proximity to the bacteria, but they are not internalized. Using quartz crystal microbalance (QCM), it was revealed that S. oneidensis biofilm formation is slowed in the presence of nanoparticles. Though S. oneidensis grows more slowly in the presence of TiO2 nanoparticles, riboflavin secretion, a function related to the S. oneidensis metal reducing capacity, was increased significantly in a nanoparticle dose-dependent manner. Both changes in biofilm formation and riboflavin secretion are supported by changes in gene expression in nanoparticle-exposed S. oneidensis. This broad study of bacterial nanotoxicity, including use of sensitive analytical tools for functional assessments of biofilm formation, riboflavin secretion, and gene expression, has implications for total ecosystem health as the use of engineered nanoparticles grows.

Amperometric assessment of functional changes in nanoparticle-exposed immune cells: varying Au nanoparticle exposure time and concentration

A mast cell/fibroblast co-culture system is used as a model to assess the toxicity of Au nanoparticles over the course of 72 hours of exposure. Cellular uptake of nanoparticles was found to increase over the 72 hr exposure period and the nanoparticles localized within granular bodies of the primary culture mast cells. These granules were found to increase in volume with the addition of nanoparticles. There was no decrease in viability for 24 hr exposed cells but a slight viability decrease was found after 48 and 72 hr exposure. Carbon-fiber amperometry analysis of exocytosis of serotonin from mast cells revealed changing release profiles over the time course of exposure. In early exposure times, granular secretion of serotonin increased with exposure to Au nanoparticles whereas 72 hr exposure showed decreased secretion of serotonin with nanoparticle exposure. The kinetics of this release was also found to be affected by Au colloid exposure where the rate of serotonin expulsion decreased with increasing nanoparticle exposure. These results illustrate the dynamic nature of nanoparticle-cell interactions and the critical changes in cell behavior even when viability is unaffected.

Toward Correlation in In Vivo and In Vitro Nanotoxicology Studies

Nanomaterials have the promise of revolutionizing current treatment and diagnosis of diseases, which has led to 33 nanotherapeutics drugs currently on the market and many more in various stages of clinical trials. With an increasing number of products available and in development, along with the unique, emergent properties of the nanoparticle therapeutics themselves, regulatory agencies are now faced with decisions regarding the regulation of such novel technologies. Regulatory guidance, particularly in pre-clinical stages, has the potential to facilitate quick and safe development of these novel materials, but new regulation beyond what is currently in place must be justified in a clear and distinctive toxic response. Herein, we examine literature that compares and correlates in vivo and in vitro nanotoxicity studies to gain a deeper understanding of the modes of nanoparticle toxicity. Additionally, this comparison aims to identify clear and unique toxicity responses caused by nanoparticles, which informs our perspective on pre-clinical nanotherapeutic oversight.

Platelet membrane variations and their effects on δ-granule secretion kinetics and aggregation spreading among different species

Platelet exocytosis is regulated partially by the granular/cellular membrane lipids and proteins. Some platelets contain a membrane-bound tube, called an open canalicular system (OCS), which assists in granular release events and increases the membrane surface area for greater spreading. The OCS is not found in all species, and variations in membrane composition can cause changes in platelet secretion. Since platelet studies use various animal models, it is important to understand how platelets differ in both their composition and granular release to draw conclusions among various models. The relative phospholipid composition of the platelets with (mouse, rabbit) and without (cow) an OCS was quantified using UPLC-MS/MS. Cholesterol and protein composition was measured using an Amplex Red Assay and BCA Assay. TEM and dark field platelet images were gathered and analyzed with Image J. Granular release was monitored with single cell carbon fiber microelectrode amperometry. Cow platelets contained greater amounts of cholesterol and sphingomyelin. In addition, they yield greater serotonin release and longer δ granule secretion times. Finally, they showed greater spreading area with a greater range of spread. Platelets containing an OCS had more similarities in their membrane composition and secretion kinetics compared to cow platelets. However, cow platelets showed greater fusion pore stability which could be due to extra sphingomyelin and cholesterol, the primary components of lipid rafts. In addition, their greater stability may lead to many granules assisting in spreading. This study highlights fundamental membrane differences and their effects on platelet secretion.