1Biotechnology Department, Basic and Applied Sciences Institute, Egypt–Japan University of Science and Technology (E–JUST), Alexandria, Egypt
2Department of Botany and Microbiology, Faculty of Science, Alexandria University, Alexandria, Egypt
3Faculty of Chemical Engineering, University of Chemistry and Technology Prague, 166 28, Prague, Czech Republic
4Nanoscience Department, Basic and Applied Sciences Institute, Egypt–Japan University of Science and Technology (E–JUST), Alexandria, Egypt
5Department of Physics, Faculty of Science, Kafrelsheikh University, Kafrelsheikh, Egypt
6Department of Biochemistry, Faculty of Science, Ain Shams University, Cairo, Egypt
*Corresponding Author E-mail: fatima.Hassouna@vscht.cz
Online published on 31 March, 2026.
Halophilic organisms possess interesting characteristics including the presence of many bioactive products. However, microbial diversity in salt lakes has not been well studied. Luminescent haloarchaeal carotenoids are well known for their biological activity. Furthermore, owing to their photoluminescence and small size, carbon quantum dots (CQDs) are widely utilized in many biomedical and biotechnological applications. We isolated the first culturable halophilic archaeal species, Haloarcula sp. NF1 from the Abu–Sherouf salt–pool, Siwa, Egypt, and reported the conversion of haloarchaeal carotenoids to CQDs. Organic solvent–extracted carotenoids were hydrothermally converted into two CQDs, designated as GCQDs and YCQDs. The extracted carotenoids and CQDs were characterized using fluorescence and UV–visible spectrophotometry, X–ray Photoelectron Spectroscopy (XPS), Fourier–transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). CQDs were found to be of spherical shape with 2.75nm and 3.75nm mean size for YCQDs and GCQDs, respectively, with high dual emission fluorescence energy on a wide range of excitation and emission wavelengths, encompass a Quantum Yield of 13.3% for YCQDs and 6.5% for GCQDs and both CQDs reveals a bi–exponential fluorescence lifetime decay with first decay values of 3.23ns and 3.35ns for YCQDS and GCQDs. Cytotoxicity was assessed as a preliminary method to detect anticancer activity of the prepared species against normal and breast cancer cell lines, L929 and MDA–MB–231, respectively, using the MTT assay and was found to possess cytotoxic activities against MDA–MB–231 cancer cell lines and good biocompatibility against normal cell lines.
Graphical illustration
Carbon Quantum Dots, Nanoparticles, Green synthesis, MDA–MB–231 cytotoxicity, Haloarchaeal Carotenoids, Halophilic archaea, Egyptian salt lakes
