Abstract:
The development of amine-functionalized graphene quantum dots (GQDs) linked to
mycolic acids (MAs) as a potential fluorescent biosensor to detect tuberculosis
(TB) biomarkers is described. GQDs have attractive properties: high fluorescence,
excellent biocompatibility, good water solubility, and low toxicity. MAs are lipids that
are found in the cell wall of Mycobacterium tuberculosis that are antigenic, however,
they are soluble only in chloroform and hexane. Chloroform-soluble MAs were
covalently linked to synthesized water-soluble GQDs using an amide connection to
create a potential fluorescent water-soluble TB biosensor: MA-GQDs. Fluorescence
results showed that GQDs had a narrow emission spectrum with the highest
emission at 440 nm, while MA-GQDs had a broader spectrum with the highest
emission at 470 nm, after exciting at 360 nm. The appearance of the peptide bond
(amide linkage) in the Fourier-transform infrared spectrum of MA-GQDs confirmed
the successful linking of MAs to GQDs. Powder X-ray diffraction exhibited an
increase in the number of peaks for MA-GQDs relative to GQDs, suggesting that
linking MAs to GQDs changed the crystal structure thereof. The linked MA-GQDs
showed good solubility in water, high fluorescence, and visual flow through a
nitrocellulose membrane. These properties are promising for biomedical fluorescence
sensing applications.
