Scientific claims should be supported by experimental evidence [3]

In the previous two posts, I have shown that there is no sound Transmission Electron Microscopy evidence for the existence of the stripes and barely any published evidence of the existence of water-soluble stripy nanoparticles 2:1 MUS:OT (one image of one particle).

Here I discuss a claim which has been made in the original Jackson et al, then repeated many times in the literature by those authors and others, with reference to Jackson et al, but for which there is strictly no published experimental evidence.

The last two sentences of the Jackson et al abstract reads:

We demonstrate that the formation of ordered domains depends on the curvature of the underlying substrate, and that novel properties result from this nanostructuring. For example, because the size of the domains is much smaller than the typical dimensions of a protein, these materials are extremely effective in avoiding non-specific adsorption of a variety of proteins.

However, we note in “Stripy Nanoparticles Revisited” that:

Jackson et al. claim that the OT/MPA nanoparticles, because of their nanometer-sized stripes, are resistant to nonspecific protein adsorption and outperform traditional protein-repellent surfaces.[ 1 ] This is repeated in several papers of the series, [ 2a , 2d–f, , 2h–k ] with a reference to Jackson et al., [ 1 ] but to our knowledge no data have been published on the interaction of OT/MPA nanoparticles with proteins. If confirmed by experimental evidence, this observation would be interesting because most protein-repellent materials, e.g., polyethylene glycol (PEG) or dextran, tend to have relatively hydrophilic surfaces, whereas the OT/MPA nanoparticles are not water-soluble.

In the response to “Stripy Nanoparticles Revisited”, there is no response to that point. The claim is simply repeated and no additional data is provided. The only “evidence” which had been provided in 2004 by Jackson et al was a cartoon:

Fig 5 from Jackson et al, Nature Materials, 3, 330 - 336 (2004)

Fig 5 from Jackson et al, Nature Materials, 3, 330 – 336 (2004)

 

 

 

The absence of experimental data to support a claim which is considered important enough to form the conclusion of the article abstract is, in itself, remarkable.

The cartoon, of course, demonstrates nothing. This does not need elaborating. In a later publication (J. Am. Chem. Soc., 2011, 133, 1438; different nanoparticle composition), the authors found that, in fact, stripy nanoparticles could specifically interact with proteins:

specific interactions

Adapted from Fig 3, JACS 2011, 133, 1438

 

 

 

 

 

 

 

 

Jackson, A., Myerson, J., & Stellacci, F. (2004). Spontaneous assembly of subnanometre-ordered domains in the ligand shell of monolayer-protected nanoparticles Nature Materials, 3 (5), 330-336 DOI: 10.1038/nmat1116

Cesbron, Y., Shaw, C., Birchall, J., Free, P., & Lévy, R. (2012). Stripy Nanoparticles Revisited Small DOI: 10.1002/smll.201001465

 
Hung, A., Mwenifumbo, S., Mager, M., Kuna, J., Stellacci, F., Yarovsky, I., & Stevens, M. (2011). Ordering Surfaces on the Nanoscale: Implications for Protein Adsorption Journal of the American Chemical Society, 133 (5), 1438-1450 DOI: 10.1021/ja108285u

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2 comments

  1. Brutal. Why the heck did they not run some sort of binding experiments, with different ligand amounts (100-0, 67-33, 50-50, 33-67, 0-100). While this would not prove or disprove the microstructure, it would at least tell us if something interesting was happening (like a non-linear response of the midpoints, versus the endpoints). Isn’t this like science 101?

    BTW, this is what I expected to learn about in the water post. Not the image discussion, but just if any interesting properties occur for mixed-ligand covered particles.

    I think the failure to ever test this and the reliance on text in the abstract (and cartoons) is what I saw from colloid science (I love call it that, to annoy the nano-types) in the late 90s. This is when FS was trained.

    Like

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