Switching of the Polarity-Sensitive Aggregation Pattern of a Thiosemicarbazone-Based Anticancer Luminophore and Its Involvement in Cellular Apoptosis of the Human Lung Cancer Cell Line

Abstract

Elucidation of the photophysical and biochemical properties of small molecules can facilitate their applications as prospective therapeutic imaging (theragnostic) agents. Herein, we demonstrate the luminescence behavior of a strategically designed potential therapeutic thiosemicarbazone derivative, (E)-1-(4-(diethylamino)-2-hydroxybenzylidene)-4,4-dimethylthiosemicarbazide (DAHTS), accompanied by the illustration of its solvation and solvation dynamics using spectroscopic techniques and exploring its promising antitumor activities by adopting the necessary biochemical assays. Solvent-dependent photophysical properties, namely UV−vis absorption, fluorescence emission, and excitation profiles, concentrationdependent studies, and time-resolved fluorescence decays, serve as footprints to explain the existence of DAHTS monomers, its excitedstate intramolecular proton transfer (ESIPT) product, and dimeric and aggregated forms. The emission intensity progressively intensifies with increasing polarity and proticity of the solvents up to MeOH, but in water, a sudden dip is seen. Solvent polarity and H-bonding modulate the fluorescence behavior of the primary emission peak and significantly influence the formation of the dimer and DAHTS aggregates. The designed luminophore (DAHTS) exhibits significant antiproliferative activity against the human lung cancer (A549) cell lines with inhibitory concentrations (IC 50 ) of 16.88 and 11.92 μM for 24 and 48 h, respectively. DAHTS effectively reduces the cell viability and induces cytotoxicity with extensive morphological changes in A549 cells in the form of spikes when compared to the normal HEK cell lines. More importantly, it increases the p53 expression at the mRNA level that consolidates its potential therapeutic activity. The effect of DAHTS on apoptotic pathways against the A549 cell line has been investigated to determine its probable mechanism of cell death. Thus, the all-inclusive understanding of the photophysical properties and the necessary biochemical assays put forward important steps toward tailoring the thiosemicarbazone core structure for favorable cancer theragnostic applications in academic and pharmaceutical research.

Photophysical Properties of (E)-1-(4-(Diethyla-mino)-2-hydroxybenzylidene)-4,4-dimethylthiosemicarbazide Compound and Its Triple Fluorescence Emission Mechanism: A Theoretical Perspective

“…According to the research by Ganorkar et al, , they found that DAHTS existed in the dimer conformation in ACN solvent, and the connection mode of the dimer was given by analyzing the crystal structure.…”

“…Interestingly, in their experiment, Ganorkar et al reported that DAHTS exhibited a novel and interesting phenomenon of triple fluorescence emission in nonpolar (CYH) and aprotic polar [acetonitrile (ACN)] solvents. 43 It was speculated that the proton-transfer behavior led to this special phenomenon of fluorescence in the experiment. The internal reason for this fluorescence phenomenon and the proton-transfer mechanism in DAHTS still remain not explicit.…”

“… The molecule could be an excellent probe for the detection of cancer cells. Interestingly, in their experiment, Ganorkar et al reported that DAHTS exhibited a novel and interesting phenomenon of triple fluorescence emission in nonpolar (CYH) and aprotic polar [acetonitrile (ACN)] solvents . It was speculated that the proton-transfer behavior led to this special phenomenon of fluorescence in the experiment.…”

Fluorescence probes for lung carcinoma diagnosis and clinical application

“…[10][11][12] Lung carcinoma is still a challenging problem. [13][14][15][16][17][18][19][20][21][22][23] It is expected that the development of fluorescent probes can serve the clinical work well, so the clinical application strategy of fluorescence-guided surgery (FGS) can be realized. During the surgical procedure, the fluorescent probes are used for the specific visual imaging of the lesion site to detect and discriminate malignant and normal tissues, which can reduce the surgical trauma and improve the prognosis of patients.…”