Safe Nanoparticles: Are We There Yet?

Abstract

The field of nanotechnology has grown over the last two decades and made the transition from the benchtop to applied technologies. Nanoscale-sized particles, or nanoparticles, have emerged as promising tools with broad applications in drug delivery, diagnostics, cosmetics and several other biological and non-biological areas. These advances lead to questions about nanoparticle safety. Despite considerable efforts to understand the toxicity and safety of these nanoparticles, many of these questions are not yet fully answered. Nevertheless, these efforts have identified several approaches to minimize and prevent nanoparticle toxicity to promote safer nanotechnology. This review summarizes our current knowledge on nanoparticles, their toxic effects, their interactions with mammalian cells and finally current approaches to minimizing their toxicity.

Keywords: cellular interactions; drug delivery; nanoparticles; nanotechnology; safe nanoparticles; toxicology.

Figure 1

The number of scientific papers published in the last two decades. Papers were identified in Pubmed database from the year 2000 until 2019 using the key words nanoparticles (green) and safe nanoparticles, toxicity of NPs (nanoparticles), risks of NPs (red).

Figure 2

Routes of exposure to NPs and their distribution to organs in the human body. Exposure to NPs may be through lungs, injection, ingestion or skin absorption. Distribution organs include liver, spleen and kidney. The brain is suggested as a potential target for NP distribution, however direct evidence is still lacking.

Figure 3

Cell–nanoparticle interactions and mechanism of NP toxicity. Following cellular uptake of NPs, NPs go through lysosomal pathways and result into release of reactive oxygen species and/or reactive metal ions causing mitochondrial dysfunction and DNA damage.

Figure 4

Physicochemical properties of nanoparticles that dictate their toxicities. Size, surface modification, surface charge, composition, shape and aggregation state of NPs are key factors in dictating NPs distribution in different organ systems following their exposure.

Figure 5

Strategies for safer nanoparticles. Effective strategies start from choosing the right physicochemical properties of NPs. Once studies show potential risks then alternative strategies may include modifications of the composition or surface functionalities in addition to other strategies discussed in the text.