Open Access Article
This Open Access Article is licensed under a Creative Commons Attribution 3.0 Unported Licence
Expression of concern: The effect of metal ions on endogenous melanin nanoparticles used as magnetic resonance imaging contrast agents
Anqi Chenab,
Jinghua Sunab,
Shijie Liub,
Liping Lib,
Xiaoyang Pengb,
Lixin Ma*cd and
Ruiping Zhang*ab
aImaging Department, The Affiliated Da Yi Hospital of Shanxi Medical University, Taiyuan 030000, China. E-mail: zrp_7142@sxmu.edu.cn
bShanxi Medical University, Taiyuan 030001, China
cDepartment of Radiology, University of Missouri, Columbia, MO, USA
dHarry S. Truman Memorial Veterans’ Hospital, Columbia, MO 65201, USA. E-mail: mal@health.missouri.edu
First published on 4th August 2025
Abstract
Expression of Concern for ‘The effect of metal ions on endogenous melanin nanoparticles used as magnetic resonance imaging contrast agents’ by Anqi Chen et al., Biomater. Sci., 2020, 8, 379–390, https://doi.org/10.1039/C9BM01580A.
The Royal Society of Chemistry is publishing this expression of concern in order to alert readers to concerns with Fig. 3 and 5.
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Fig. 1 Comparison study of MRI performance in vitro. (a) T1-Weighted phantom images and relaxivity measurements of Gd-DTPA and MNP-PEG-Gd with different Gd3+![[thin space (1/6-em)]](https://www.rsc.org/images/entities/char_2009.gif) :MNP mass ratios. (b) T1-Weighted phantom images and relaxivity measurements of MNP-PEG-Mn with different Mn2+:MNP mass ratios. (c) T1-Weighted phantom images and relaxivity measurements of MNP-PEG-Fe with different Fe3+:MNP mass ratios. (d) T1-Weighted phantom images and relaxivity measurements of MNP-PEG-Cu with different Cu2+:MNP mass ratios. The paramagnetic metal ion concentrations are indicated as 0.4, 0.2, 0.1, 0.5, 0.25 and 0 mM. | ||
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| Fig. 2 (g) Images of H&E-stained major organs (heart, liver, spleen, lung and kidney) from healthy control mice and MNP-PEG-M-injected mice at 24 h. The scale bar of the images of H&E-stained organs are 200 μm. | ||
The T1-weighted phantom images in Fig. 3a, b and d contain duplicated images. The authors have explained that the process of moving, collection, and organisation for these approximate 150 images caused some of them to be duplicated, and have checked and provided a revised image here.
An independent expert has viewed the raw data and had concerns as the response indicated that some wells were diluted incorrectly due to operator error, and had concerns over the cropping and alignment of the images. The expert suggested that the authors repeat this analysis, however the authors have indicated that this may not possible due to the time elapsed.
The images of H&E-stained organs in Fig. 5g contains partial duplications in the heart, spleen, lung and kidney images. The authors have explained that during the experiment, they carried out continuous field of view observation and acquisition of all H&E sections in the experimental group and the control group to ensure the in vivo safety of MNP-PEG-M injection on experimental animal tissue, and the experimental results proved that MNP-PEG-M was safe in vivo. The process of moving, collecting, and organising lots of images caused some of them to be duplicated. The authors have provided a revised Fig. 5g here, which has been reviewed by an independent expert.
An expression of concern will continue to be associated with the article until the authors are able to repeat the experiment in Fig. 3.
Maria Southall
22nd July 2025
Executive Editor, Biomaterials Sciences
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