Scientific claims should be supported by experimental evidence [2]

In the previous post, I have shown that there is no sound Transmission Electron Microscopy evidence that would indicate the existence of the stripes.

In this second example, I discuss the evidence supporting the existence of “water-soluble” stripy nanoparticles. The “water-soluble” stripy nanoparticles were first reported by Uzun et al (Chem Comm 2008, 196). The authors argue that nanoparticles which are capped by a mixture of octane thiol (OT) and 11-mercaptoundecane sulfonate (MUS) are stripy.

The totality of the scanning probe microscopy published experimental evidence is shown below:

Fig 2 from Uzun et al, Chem Comm 2008, 196

Fig 2 from Uzun et al, Chem Comm 2008, 196

For each composition, this amounts to one image of one nanoparticle. Independently of the interpretation of these images (discussed in previous posts and in “stripy revisited”), it is truly remarkable that so little evidence has been accepted as a convincing proof.

I have no doubt that the authors have many more images, but it is the job of the referees to evaluate the results and they cannot do so if the evidence is not included – it could have been done in supporting information since this was a communication with restricted space for results; it is also the job of the scientific journals to ensure that supporting evidence is provided for evaluation by peers beyond the peer review process.

Even more remarkable:

The 2:1 MUS:OT water-soluble nanoparticle (left above) form the basis of the cell uptake study published in Nature Materials the same year (Verma et al). This article contains also one image of one 2:1 MUS:OT water-soluble nanoparticle (right below).

stmVerma

Adapted from Figure 1 of Verma et al; the corresponding figure legend says: “Schematic diagrams of the ligand shell structure of the nanoparticles and representative STM images (scale bars 5 nm)”

and… it is the same image. [update: this has led to a correction at Nature Materials]

There is now one more article on the uptake of those particles in cells, published this year in Biointerphases. Since it has been clearly demonstrated in the previous articles that 2:1 MUS:OT water-soluble nanoparticle are stripy, the authors/referees/editors have not felt the need to include any further experimental evidence: there is no STM images in that latter article.

Uzun, O., Hu, Y., Verma, A., Chen, S., Centrone, A., & Stellacci, F. (2008). Water-soluble amphiphilic gold nanoparticles with structured ligand shells Chemical Communications (2) DOI: 10.1039/b713143g

Carney, R., Carney, T., Mueller, M., & Stellacci, F. (2012). Dynamic Cellular Uptake of Mixed-Monolayer Protected Nanoparticles Biointerphases, 7 (1-4) DOI: 10.1007/s13758-011-0017-3

Verma, A., Uzun, O., Hu, Y., Hu, Y., Han, H., Watson, N., Chen, S., Irvine, D., & Stellacci, F. (2008). Surface-structure-regulated cell-membrane penetration by monolayer-protected nanoparticles Nature Materials, 7 (7), 588-595 DOI: 10.1038/nmat2202

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4 comments

  1. What surprises me is how little comment this posting has raised. Plagiarism (for that is what data re-use is) is not allowed. All journals specifically state this in their Instructions to Authors. Plagiarism is one of the major reasons for papers being retracted and appearing on Retraction Watch. I have posted a rather longer entry on my blog with links, for those who wish to follow this up. For any apologists, how can we stand up in front of undergraduate students and tell them that they will fail if they plagiarise, if we condone it in our professional life?

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    1. Well said. Personally, I have difficulty understanding why this image duplication happened… Like c’mon, really? Didn’t have another STM image?

      One of the rules I have learned early on working on the synthesis of colloidal nanocrystals is the attention to the reproducibility and artefacts. For example, while developing a new synthesis and characterizing the product in TEM, you occasionally see some crazy stuff. It could be awkward shapes or peculiar arrangements of particles, among the main constituent of the sample. And it is easy to start chasing them and take bunch of images, because they are unusual. But unless you are able to control production of those “special ones” it is just an artifact and oh well, you still can color it in photoshop and put on the wall for fun or aesthetic pleasure.

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      1. @ Dmitry Baranov and @ferniglab
        ferniglab raised a super-important question but I have been very busy blogging on the main post about nitty-gritty science.

        Q: ” I have difficulty understanding why this image duplication happened”

        A: It’s another case of cherry-picking data. But let me elaborate on the size of this cherry basket. Every imaging scan is about 100 x 100 nm. Each nano-particle is about 5 nm in size. That gives approximately, lets say 200-400 closely packed nanoparticles. The authors have performed scan-speed-indepencence tests (JACS 2007) and according to their Figures they have at least 5 scans for each image. So thats already 2000 individual nanoparticle images. Yet, they ascertain on many occasions that consecutive scanning gives rise to the same features. So lets say they recorded 10 scans to prove their point. Now thats 20,000 nanoparticle images. And you pick **one** repeatedly in multiple publications. 1 in 20,000.

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  2. The image re-use is damning, but why aren’t you discussing the water solubility? I don’t see how the image duplication has anything to say about the water solubility info.

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