The increased reactivity of nanoparticles is one of their most useful properties and is leveraged in fields such as catalysis, consumer products, and energy storage. However, this high reactivity also means that a nanoparticle in a biological environment may have unintended impacts. For example, many nanoparticles such as silver, copper, and ceria interact with cells to produce
reactive oxygen species or ROS which can cause premature cell death through
apoptosis. Determining the toxicity of a specific nanoparticle requires knowledge of the particle's chemical composition, shape, size and is a field that is growing alongside advances in nanoparticle research. Determining the impact of a nanoparticle on a living system is not straightforward. A multitude of
in vivo and
in vitro studies must be done to fully characterize reactivity. In vivo studies often use whole organisms such as
mice or
zebrafish to infer the interaction of the nanoparticle on a healthy human body. In vitro studies look at how nanoparticles interact with specific cell colonies, typically of human origin. Both types of experiments are needed for a complete understanding of nanoparticle toxicity, especially human toxicity, since no one model has complete human relevance. Few studies have investigated the
ADMET of platinum nanoparticles, and the results demonstrated that they are the ones who persist most in organisms respect to
silver and
gold nanoparticles.
Drug delivery A topic of research within the field of nanoparticles is how to use these small particles for
drug delivery. Depending on particle properties, nanoparticle may move throughout the human body are promising as site-specific vehicles for the transport of medicine. Current research using platinum nanoparticles in drug delivery uses platinum-based carries to move antitumor medicine. In one study, platinum nanoparticles of diameter 58.3 nm were used to transport an anticancer drug to human colon
carcinoma cells, HT-29. Uptake of the nanoparticles by the cell involves compartmentalization of the nanoparticles within
lysosomes. The high acidity environment enables
leaching of platinum ions from the nanoparticle, which the researchers identified as causing the increased effectiveness of the drug. In another study, a Pt nanoparticle of diameter 140 nm was encapsulated within a
PEG nanoparticle to move an antitumor drug, Cisplatin, within a prostate cancer cell (LNCaP/PC3) population. Use of platinum in drug delivery hinges on its ability to not interact in a harmful manner in healthy portions of the body while also being able to release its contents when in the correct environment.
Toxicology Toxicity stemming from platinum nanoparticles can take multiple forms. One possible interaction is
cytotoxicity or the ability of the nanoparticle to cause cell death. A nanoparticle can also interact with the cell's DNA or
genome to cause
genotoxicity. These effects are seen in different levels of gene expression measured through protein levels. Last is the developmental toxicity that can occur as an organism grows. Developmental toxicity looks at the impact the nanoparticle has on the growth of an organism from an embryonic stage to a later set point. Most nanotoxicology research is done on cyto- and genotoxicity as both can easily be done in a cell culture lab. Platinum nanoparticles have the potential to be toxic to living cells. In one case, 2 nm platinum nanoparticles were exposed to two different types of
algae in order to understand how these nanoparticles interact with a living system. In both species of algae tested, the platinum nanoparticles inhibited growth, induced small amounts of membrane damage, and created a large amount of
oxidative stress. In another study, researcher tested the effects of differently sized platinum nanoparticles on primary human
keratinocytes. The authors tested 5.8 and 57.0 nm Pt nanoparticles. The 57 nm nanoparticles had some hazardous effects including decreased cell metabolism, but the effect of the smaller nanoparticles was much more damaging. The 5.8 nm nanoparticles exhibited a more deleterious effect on the DNA stability of the primary keratincoytes than did the larger nanoparticles. The damage to the DNA was measured for individual cells using single-gel electrophoresis via the
comet assay. Researchers have also compared the toxicity of Pt nanoparticles to other commonly used metallic nanoparticles. In one study, the authors compared the impact of different nanoparticle compositions on the
red blood cells found in the human bloodstream. The study showed that 5–10 nm platinum nanoparticles and 20–35 nm gold nanoparticles have very little effect on the red blood cells. In the same study it was found that 5–30 nm silver nanoparticles caused membrane damage, detrimental morphological variation, and
haemagglutination to the red blood cells. In a recent paper published in Nanotoxicology, the authors found that between silver (Ag-NP, d = 5–35 nm), gold (Au-NP, d = 15–35 nm), and Pt (Pt-NP, d = 3–10 nm) nanoparticles, the Pt nanoparticles were the second most toxic in developing
zebrafish embryos, behind only the Ag-NPs. Their conclusions were based on two major observations. First, the authors found that platinum nanoparticles with spherical morphologies and sizes less than 3 nm showed biologically toxic properties; measured in terms of mortality, hatching delay, phenotypic defects and metal accumulation. However, in order for these antioxidative properties to be exploited, the platinum nanoparticles must first enter the cells, so perhaps there is another explanation for this observation of increased bacterial cell growth. Most studies so far have been size based using an in vivo mouse model. In one study, researchers compared the effects of sun 1 nm and 15 nm platinum nanoparticles on mice. The 15 mg/kg dose of sub 1 nm platinum nanoparticles were found to cause liver damage while the larger particles had no effect. A similar study using a singular injection as an exposure source of platinum nanoparticles into the mouse model found necrosis of tubular epithelial cells for particles under 1 nm, but no effect with those particles of 8 nm. These in vivo studies show a trend that the toxicity of the platinum nanoparticles is size dependent, most likely due to the ability of the nanoparticle to get into a high impactful region within the body. A complete study analyzing the effect of varying sized platinum nanoparticles used both in vivo and in vitro models is used to gain a better understanding what impact these nanoparticles could have. Using mice as a model, they found retention of the platinum nanoparticles by the respiratory tract of the mouse. This was accompanied by a minor to mild inflammation of the surrounding lung tissue. However, their in vitro tests using human and lung
epithelial cells found no cytotoxic or oxidative stress effects caused by the platinum nanoparticles despite clear evidence of cellular uptake. == See also ==