Corrigendum: Augmented COlorimetric NANoplasmonic (CONAN) Method for Grading Purity and Determine Concentration of EV Microliter Volume Solutions
Andrea Zendrini1,2* 
Lucia Paolini3,4* 
Sara Busatto4,5 
Annalisa Radeghieri3,4 
Miriam Romano3,4 
Marca H. M. Wauben6 
Martijn J. C. van Herwijnen6 
Peter Nejsum7 Anne Borup7 Andrea Ridolfi4,8,9 Costanza Montis4,9 Paolo Bergese2,3,4- 1Department of Animal Science, Food and Nutrition-Università Cattolica del Sacro Cuore, Piacenza, Italy
- 2Consorzio Interuniversitario Nazionale per la Scienza e la Tecnologia dei Materiali, Florence, Italy
- 3Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
- 4Consorzio Sistemi a Grande Interfase, Department of Chemistry, University of Florence, Sesto Fiorentino, Italy
- 5Department of Transplantation, Mayo Clinic, Jacksonville, FL, United States
- 6Department of Biochemistry and Cell Biology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, Netherlands
- 7Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark
- 8Istituto per lo Studio dei Materiali Nanostrutturati (CNR-ISMN), Bologna, Italy
- 9Department of Chemistry, University of Florence, Sesto Fiorentino, Italy
A Corrigendum on
Augmented COlorimetric NANoplasmonic (CONAN) Method for Grading Purity and Determine Concentration of EV Microliter Volume Solutions
by Zendrini, A., Paolini, L., Busatto, S., Radeghieri, A., Romano, M., Wauben, M. H. M., et al. (2020). Front. Bioeng. Biotechnol. 7:452. doi: 10.3389/fbioe.2019.00452
In the original article, there was an error. The reported concentration of the trisodium citrate dihydrate solution, “3.5 mM,” used to synthesize gold nanoparticles (AuNPs), was incorrect. This error inevitably leads to failure in gold nanoparticle synthesis. The correct trisodium citrate dehydrate concentration should be “34.0 mM.”
A correction has been made to the Methods section, subsection Preparatory Procedures, paragraph, under the AuNP Synthesis method:
AuNP Synthesis
AuNPs are synthesized through classic Turkevich's citrate reduction method (Turkevich et al., 1951).
• Dissolve trisodium citrate · 2H2O in HPLC grade water to a final concentration of 34.0 mM (1.0% wt).
• Prepare 20 ml of 1 mM HAuCl4 in HPLC grade water.
• Boil the HAuCl4 solution under continuous stirring.
• Inject 2 ml of trisodium citrate · 2H2O 34.0 mM into the boiling solution. Crucial step: trisodium citrate injection speed influences AuNP size and therefore final concentration. A one-shot injection leads to smaller particles (usually around 12–15 nm); slow injection will result in NP aggregation and precipitation.
• Keep stirring and wait for the solution to change color from the original pale yellow to wine red.
• After 10 min, cool the solution in a water-ice bath for 5 min.
• Store the AuNPs at 4°C. Crucial step: 10–20 nM AuNP solutions are metastable and tend to form aggregates and precipitate with time. In our experience they keep their properties with respect to the assay up to 1 month of storage at the above described conditions. Anyhow it is strongly suggested to freshly (re)determine before any usage the key characteristics of the AuNP solution which are relevant for the assay as described in section Determination of AuNP Molar Concentration and Spectral Properties.
The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way. The original article has been updated.
References
Keywords: extracellular vesicles, synthetic vesicles, liposomes, purity, titration, particle number, nanoparticles, nanoplasmonics
Citation: Zendrini A, Paolini L, Busatto S, Radeghieri A, Romano M, Wauben MHM, van Herwijnen MJC, Nejsum P, Borup A, Ridolfi A, Montis C and Bergese P (2021) Corrigendum: Augmented COlorimetric NANoplasmonic (CONAN) Method for Grading Purity and Determine Concentration of EV Microliter Volume Solutions. Front. Bioeng. Biotechnol. 9:674507. doi: 10.3389/fbioe.2021.674507
Received: 01 March 2021; Accepted: 10 March 2021;
Published: 13 April 2021.
Edited and reviewed by: Ilja Kusters, Harvard Medical School, United States
Copyright © 2021 Zendrini, Paolini, Busatto, Radeghieri, Romano, Wauben, van Herwijnen, Nejsum, Borup, Ridolfi, Montis and Bergese. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Andrea Zendrini, andrea.zendrini@unibs.it; Lucia Paolini, lucia.paolini@unibs.it