Fishing to Design Inherently Safer Nanoparticles - Zebrafish: Methods for Assessing Drug Safety and Toxicity - page 275

Addressing potential risks of nanoparticles should be a priority concern not only
for regulatory agencies, but also for the researchers and companies producing the
particles. Collaborations between scientific investigators and manufacturers will
preemptively minimize negative consequences and allow for development of the
most environmentally benign nanochemistries and manufacturing methods. Greener
nanotechnology is a practice pioneered at the University of Oregon to include
replacing or minimizing usage of hazardous chemicals. Greener nanoscience also
seeks to alter nanoparticles to render them nontoxic (e.g., via new reaction mechan-
isms, controlling physical properties, or surface functionalization).
It is now clear that rapid, relevant, and efficient testing methods must be
developed to assess emerging nanoparticles. The investigation of nanoparticle
interactions with biological systems must be conducted at multiple levels of biolog-
ical organization (i.e., molecular, cellular, and organismal levels). There are many
models that could be used to assess nano-biological interactions, but due to the rapidly
increasing number of manufactured nano-particles, the ideal model must also offer
high-throughput capabilities. For example, although in vitro techniques (cell-based
systems) are preferred for cost and time efficiency, direct translation to whole
organisms or humans is difficult. Challenges of in vitro studies also include contra-
dictory effects from nano-biological interactions depending on the cell type, organ
system, or developmental stage of the cells being used (Nakamura and Isobe, 2003;
Bosi et al., 2004; Sayes et al., 2005; Isakovic et al., 2006). In vivo models (typically
rodents) are more comprehensive and perhaps predictive, but the cost, labor, time, and
infrastructure required to conduct studies in rodents make these species less than ideal
testing platforms. The embryonic zebrafish model is ideally suited for rapid through-
put nanoparticle testing because this is a genetically tractable vertebrate model, with
rapid generation time, high sensitivity to environmental insult, and relatively low cost.
20.2 APPLICATION OF EMBRYONIC ZEBRAFISH
Numerous advantages have contributed to the rise in use of the zebrafish model over
the past decade (Dodd et al., 2000; Wixon, 2000; Rubinstein, 2003). The embryonic
zebrafish is a powerful model for rapidly evaluating nanoparticle toxicity at multiple
biological levels while also defining structural properties that lead to adverse
biological consequences. The embryonic zebrafish is uniquely sensitive to environ-
mental insult due to the highly complex signaling events that underlie the cellular
differentiation, proliferation, and migration events required to complete the devel-
opmental process (Truong et al., 2008; Usenko et al., 2008; Harper, 2008a, 2008b).
Toxic responses often result from the disruption of these molecular signals.
To fully exploit the embryonic zebrafish model for nanoparticle testing, a three-
tier in vivo approach was devised to define structural properties that lead to adverse
biological consequences (Fig. 20.1). Tier 1 consists of a rapid screening experiment
that assesses embryonic zebrafish for morphological changes caused by structurally
well-characterized nanoparticles. In addition, exposed embryos are analyzed to
determine nanoparticle uptake. All data gathered in each tier are entered into the