One-pot synthesis of natural amine-modified biocompatible carbon quantum dots with antibacterial activity

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Authors	GAGIC M. KOCIOVA S. SMERKOVA K. MICHALKOVA H. SETKA M. SVEC P. PŘIBYL Jan MASILKO J. BALKOVA R. HEGER Z. RICHTERA L. ADAM V. MILOSAVLJEVIC V.
Year of publication	2020
Type	Article in Periodical
Magazine / Source	Journal of Colloid and Interface Science
MU Faculty or unit	Central European Institute of Technology
Citation
Web	https://www.sciencedirect.com/science/article/pii/S0021979720308766?via%3Dihub
Doi	http://dx.doi.org/10.1016/j.jcis.2020.06.125
Keywords	Carbon quantum dots; Amines; Thermal decomposition; Toxicity; Antibacterial activity; ROS
Description	In the present study, the thermal decomposition of citric acid in the presence of biogenic amine was used to synthesize four different functionalized carbon quantum dots (CQDs), namely, histamine-(HCQDs), putrescine-(PCQDs), cadaverine-(CCQDs) and spermine-(SCQDs). The thermal decomposition of the precursors resulted in a decrease in stability and the formation of surface amides via a cross-linking process between the carboxyl and amine groups. The deposition of biogenic amines was confirmed by a structural characterization of the synthesized CQDs. The resulting CQDs, with a net zero charge, exhibited excellent stability in environments with different pH values. Through a set of different cytotoxicity tests, the absence of gene mutations, apoptosis, necrosis or disruption in cell membranes revealed the high biocompatibility of the CQDs. The antimicrobial activity of the synthesized CQDs was investigated against different bacterial species (Staphylococcus aureus, Escherichia coli, and Klebsiella pneumonia). We determined the growth kinetics, production of reactive oxygen species (ROS), cell viability and changes in membrane integrity by scanning electron microscopy (SEM). The minimal inhibitory concentrations (MICs) for S. aureus ranged from 3.4 to 6.9 mu g/mL. Regarding E. coli and K. pneumonia, all CQD formulations reduced growth, and the MICs were determined for CCQDs and HCQDs (6.9-19.4 mu g/mL). The antibacterial activity mechanism was attributed to the oxidative stress generated after CQD treatment, which resulted in the destabilization of the bacterial membrane. The bacterial permeability to propidium iodide indicated a change in membrane integrity, and the effect of CQDs on the morphology of the bacterial cells was evidenced by SEM. (C) 2020 Elsevier Inc. All rights reserved.
Related projects:	CEITEC 2020 Czech Infrastructure for Integrative Structural Biology