Back to Journals » International Journal of Nanomedicine » Volume 13

Synergistic photoactivated antimicrobial effects of carbon dots combined with dye photosensitizers

Authors Dong X, Bond AE, Pan N, Coleman M, Tang Y, Sun YP, Yang L

Received 9 August 2018

Accepted for publication 3 October 2018

Published 27 November 2018 Volume 2018:13 Pages 8025—8035


Checked for plagiarism Yes

Review by Single anonymous peer review

Peer reviewer comments 2

Editor who approved publication: Dr Thomas Webster

Xiuli Dong,1 Ambrose E Bond,1 Nengyu Pan,2 Montrez Coleman,2 Yongan Tang,3 Ya-Ping Sun,2 Liju Yang1

1Biomanufacturing Research Institute and Technology Enterprise, Department of Pharmaceutical Sciences, North Carolina Central University, Durham, NC, USA; 2Department of Chemistry, Laboratory for Emerging Materials and Technology, Clemson University, Clemson, SC, USA; 3Department of Mathematics and Physics, North Carolina Central University, Durham, NC, USA

Background: Carbon quantum dots (CDots) have recently been reported as a new class of visible light activated antimicrobial nanomaterials. This study reports the synergistic photoactivated antimicrobial interactions of CDots with photosensitizers on bacterial cells.
Methods: The antimicrobial effects of the CDots with surface passivation molecules 2,2'-(ethylenedioxy)bis(ethylamine) in combination with photosensitizer methylene blue (MB) or toluidine blue (TB) at various concentrations were evaluated against Escherichia coli cells with and without 1-hour visible light illumination. The broth microdilution checkerboard method and isobologram analysis were used for determining if synergistic effect existed between CDots and MB or TB.
Results: The results showed that CDots alone at a concentration of 5 µg/mL did not display antimicrobial effects, 1 µg/mL MB alone only decreased 1.86 log of viable cell numbers, but the combination treatment with 5 µg/mL CDots combined with 1 µg/mL MB completely inhibited bacteria growth, resulted in 6.2 log viable cell number reduction, suggesting synergistic interaction between the two. The antimicrobial effects of CDots/TB combination exhibited similarly synergistic effects on E. coli cells. These synergistic effects between CDots and MB or TB were further confirmed using the checkerboard microdilution methods, where the fractional inhibitory concentration index value (0.5) and the isobologram analyses. The synergistic interactions were also correlated to the increased generation of intracellular reactive oxygen species in E. coli cells upon the combination treatments of CDots/MB or CDots/TB.
Conclusion: The study demonstrated the synergistic photoactivated antimicrobial effects of CDots in combination with other photosensitizers. Such synergistic effect may open new strategies for developing highly effective antimicrobial methods.

Keywords: carbon quantum dots, photosensitizer, methylene blue, toluidine blue, reactive oxygen species, synergistic antimicrobial effect

Creative Commons License This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at and incorporate the Creative Commons Attribution - Non Commercial (unported, v3.0) License. By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms.

Download Article [PDF]  View Full Text [HTML][Machine readable]