not because of the risks of nanotechnology but because of a broken scientific system.
Last week, I had the privilege of opening, as the first invited speaker, a symposium on ‘Converging technology for nanobio applications’. This was my first slide:
Collage of various images. Credits: top left “Shutterstock”, top right “Cathy Wilcox”, bottom left “Jeremy M. Lange for The New York Times, A scientist at Duke University measures silver nanoparticles”, bottom center “Terminator 3: Rise of the Machines – a vision surely now only decades away. Photograph: Observer”, bottom right “image courtesy of Oregon State University”. See links in the paragraph below for original publication.
I started my talk by asking the audience what these images had in common (I did point out that the one in the top right corner was, in my experience, scientifically accurate). The answer? These pictures had all been used to illustrate nanoparticle news in the previous week.
Exotic Nanomaterials Claimed Their First Major Workplace Injury said Stephen Leahy, writing for Motherboard on Tuesday about a worker injured by nanonickel while working without protection. The same day, Andrew Maynard, in Slate, published a more reasonable viewpoint on this same event. On Thursday, the Sydney Herald Tribune reported that a ‘Green group [had] called for ban of nano-materials in food’. This has been amplified in various outlets and, Andrew Maynard (again!) attempted to correct the record in the Conversation. On Friday, Deborah Blum, writing on the New York Times blog said that “Silver [is] Too Small to See, but Everywhere You Look”. The same day, Ben Baumont-Thomas informed us in the Guardian blog that scientists had created bionic particles ‘inspired by Terminator’. Apparently, the latter piece was tongue in cheek, but it is rather difficult to differentiate the satire from the real thing these days (see for example Salon‘s coverage of the same story here).
While these stories are very different, they all originate in peer reviewed scientific research.
The “inspired by Terminator” piece originally comes from a press release by the University of Michigan. The authors of the article and their PR department were seeking this kind of publicity: the original article (very interesting BTW) uses the word “bionic” and the press release starts with “Inspired by fictional cyborgs like Terminator…”. Good to get coverage but it is highly debatable whether this kind of analogies really help improve the general understanding of science.
Deborah Blum article is measured and well researched – as we would expect from this award-winning science journalist – and based on multiple interviews with scientists. Yet in some ways, it also reflects the deep problems we are facing with establishing solid evidence in support of scientific understanding, and, eventually, policy making.
Deborah Blum article quotes Elisabeth Loboa as saying that “There’s evidence that the particles penetrate into plasma membranes, and they can disrupt cell function” [link in the original article, which is excellent practice!]. The idea that nanoparticles can go through the membrane of cells is so often repeated that it must be true, right? Scientists making those sorts of claim should provide a very high level of proof (unfortunately, this does not happen during peer review) because there are at least two fundamental reasons to be highly skeptical of such claims, one related to evolution, and another one related to physical chemistry and thermodynamics.
Nanoparticles are of similar size to viruses. If viruses could so easily penetrate cells, we would not be here discussing the risk of nanoparticles. Thankfully, during evolution, cells have developed very advanced mechanisms to protect themselves from foreign objects. Viruses too have developed very advanced mechanisms to get in there. Quite simply none of the nanomaterials made in the lab today seriously approach the level of sophistication that viruses use to get access to the interior of the cell (see this movie for an example). The linked article by AshaRani et al provides no evidence of particles penetrating through the plasma membrane (apart from the table of content cartoon). The dose used in this particular study is huge: 200 micrograms of nanomaterials per mL of medium (the equivalent of 100 grams of silver for a 50 kg person). In line with many other studies (including our own work), AshaRani et al show nanoparticles overwhelmingly in endosomes, i.e. in bags inside cells where they are isolated from the cell machinery. Endosomal trapping also remains a major limiting factor to siRNA delivery (even using nanoparticles).
Ignoring now the biology, at the simplest level, the membrane of cells is made of a bilayer of lipids. It has an hydrophobic interior and two hydrophilic surfaces. For an object to diffuse through the membrane, it would need to have no significant repulsive or attractive interactions with any of these components (otherwise it would be repelled and not go through, or attracted and then get stuck). It is hard to imagine any nanoparticle that would fulfill such criteria (see also post and comments here for more details). While it is unclear that any nanoparticle can diffuse through the membrane, many small molecules can. We therefore have this strange situation where the supposed capability of nanoparticles to go through the cell membrane is presented as a reason to be particularly worried even though this is unproven, unlikely for nanomaterials, and common for many smaller compounds (e.g. DAPI).
I am not blaming Deborah Blum nor Elisabeth Loboa for this confusion. Such statements have become the norm. Although a more detailed investigation would be necessary (and I am not qualified to do it though I’d be happy to collaborate), my hypothesis is that the confusion results from a combination of nano hype (both in terms of risks and potential applications – see the Terminator for one striking example), bias towards the publication of positive findings, absence of post-publication peer review and debate, and poor scientific standards in an interdisciplinary area where editors and referees often lack some of the skills to properly evaluate the work (e.g. material scientists with very little understanding of biology, etc).
The situation is however now extremely serious since it has reached the point where it affects understanding of science for both basic scientists and the general public. It is our responsibility to try to fix the system.