Authors: Paul FA Wright
The Medical Journal of Australia, June 2016
The applications for engineered nanomaterials and nanotechnology are developing exponentially, along with the awareness in government, industry and public groups of nanosafety issues. There is also growing public concern caused by negative perceptions among some high profile groups that nano-enabled products are proliferating uncontrollably and being released without adequate testing of their safety.
What are the potential risks?
In reality, a one-size-fits-all approach to evaluating the potential risks and benefits of nanotechnology for human health is not possible because it is both impractical and would be misguided. There are many types of engineered nanomaterials, and not all are alike or potential hazards. Many factors should be considered when evaluating the potential risks associated with an engineered nanomaterial: the likelihood of being exposed to nanoparticles (ranging in size from 1 to 100 nanometres, about one-thousandth of the width of a human hair) that may be shed by the nanomaterial; whether there are any hotspots of potential exposure to shed nanoparticles over the whole of the nanomaterial’s life cycle; identifying who or what may be exposed; the eventual fate of the shed nanoparticles; and whether there is a likelihood of adverse biological effects arising from these exposure scenarios.
The intrinsic toxic properties of compounds contained in the nanoparticle are also important, as well as particle size, shape, surface charge and physico-chemical characteristics, as these greatly influence their uptake by cells and the potential for subsequent biological effects. In summary, nanoparticles are more likely to have higher toxicity than bulk material if they are insoluble, penetrate biological membranes, persist in the body, or (where exposure is by inhalation) are long and fibre-like.1 Ideally, nanomaterial development should incorporate a safety-by-design approach, as there is a marketing edge for nano-enabled products with a reduced potential impact on health and the environment.
What are the potential benefits?
Numerous prospective benefits for health and the environment are offered by nanotechnology, with engineered nanomaterials being developed for renewable energy capture and battery storage, water purification, food packaging, environmental sensors and remediation, as well as greener engineering and manufacturing processes. Some examples of the latter include highly efficient, low energy lighting sources, and smart clothing including a layer of piezo-electric crystals in nanomaterials for powering the wearer’s electronic devices.
The field of nanomedicine has also rapidly progressed from specialised drug delivery applications deploying liposomes (while many are not strictly nanoparticle-sized by international standard definitions, they can be engineered at the nano-scale) to nanoshells and transdermal patches, as well as the development of biocompatible nanomaterial prosthetic implants, and the metal-containing functionalised nanoparticles used for both the imaging and treatment of various cancers. Nanotechnology is also being used to develop point-of-care internet-linked diagnostic devices (eg, “doctor-on-a-chip” diagnostic tools). Nanobionics has made advances in solving the problems of interfacing between medical devices or bionic prosthetics and the nervous system; for example, invasive cranial sensing electrodes made of traditional cytotoxic metals are being replaced by more biocompatible surface transistors that can also be coupled with a dosing device.
Some common nano-enabled products currently available contain silver nanoparticles for their antimicrobial effects, including clothing items that require less frequent washing. This was mainly because of the ease of incorporating nanosilver into the surface of such products, but the quality of these products has unfortunately been variable, with some rapidly leaching silver ions. Nanosilver should preferably be reserved for more important applications, such as medical dressings for treating resistant infections that impair wound healing.