Targeted Bioimaging of Cancer Cells Using Free Folic Acid-Sensitive Molybdenum Disulfide Quantum Dots through Fluorescence "Turn-Off".

Abstract

In the present study, a proficient way for targeted bioimaging of folate receptor (FR)-positive cancer cells using free folic acid (FA)- and MoS2 QD-based nanoprobes is discussed along with its advantages over the preparation of orthodox direct FA-nanoprobe bioconjugates for the imaging. The water-soluble MoS2 QDs of size 4-5 nm with cysteine functionalization are synthesized by a simplistic bottom-up hydrothermal method. The as-prepared MoS2 QDs exhibit the blue emission with the highest emission intensity at 444 nm upon excitation of 370 nm. The MoS2 QDs are too sensitive toward FA to produce an effective and stable nanofiber structure through supramolecular interaction, which demonstrates ∼97% quenching of fluorescence. Moreover, the high selectivity and sensitivity of MoS2 QDs toward FA make the MoS2 QD-based nanoprobe an appropriate candidate for FA-targeted "turn-off" imaging probes for in vivo study of FA-pretreated FR-overexpressed cancer cells. It is obvious from the confocal microscopy images that the FA-pretreated B16F10 cancer cells show higher population of dimmed fluorescence compared to untreated cancer cells and HEK-293 normal cells. The flow cytometry study quantitatively reveals the significant difference of the geometric mean of fluorescence between FA-pretreated and untreated B16F10 cancer cells. Hence, these MoS2 QD-based nanoprobes can be applied as potential nanoprobes for the prediagnosis of cancer through targeted bioimaging.