Synergistic photoactivated antimicrobial effects of carbon dots combined with dye photosensitizers

• Published in: International journal of nanomedicine Vol. 13; pp. 8025 - 8035
• Main Authors: Dong, Xiuli, Bond, Ambrose E, Pan, Nengyu, Coleman, Montrez, Tang, Yongan, Sun, Ya-Ping, Yang, Liju
• Format: Journal Article
• Language: English
• Published: New Zealand Dove Medical Press Limited 01.01.2018; Taylor & Francis Ltd; Dove Medical Press
• Subjects: Analysis; Anti-Bacterial Agents - pharmacology; Anti-Infective Agents - pharmacology; Antibiotics; Antimicrobial agents; Bacteria; Bacterial infections; Cancer therapies; Carbon; Carbon - pharmacology; carbon quantum dots; Coloring Agents - pharmacology; Cytotoxicity; Displays (Marketing); Drug resistance; Escherichia coli; Escherichia coli - drug effects; Escherichia coli - ultrastructure; Fluorescence; Graphene; Laboratories; Light; Methylene blue; Methylene Blue - pharmacology; Microbial Sensitivity Tests; Microbial Viability - drug effects; Nanomaterials; Nanoparticles; Nanotechnology; Original Research; Permeability; Photodynamic therapy; photosensitizer; Photosensitizing Agents - pharmacology; Public health; Quantum dots; Quantum Dots - chemistry; reactive oxygen species; Reactive Oxygen Species - metabolism; Staphylococcus infections; synergistic antimicrobial effect; Tolonium Chloride - pharmacology; toluidine blue; North Carolina; United States > US; methylene blue; synergistic antimicrobial effect; toluidine blue; carbon quantum dots; reactive oxygen species; photosensitizer
• ISSN: 1178-2013; 1176-9114; 1178-2013
• DOI: 10.2147/IJN.S183086

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. 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 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. 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 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 cells upon the combination treatments of CDots/MB or CDots/TB. 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.