QuatCy-I2 and MHI-I2 in Photodynamic Therapy

Abstract

MHI-I₂ (1) and QuatCy-I₂ (2) were compared in terms of properties important for early-stage photodynamic therapy preclinical candidates. Thus, experiments were performed to monitor dark cytotoxicities, light/dark cytotoxicity ratios, selectivity of localization in tumors over other organs, and clearance from the plasma.

Figure 1

Dark cytotoxicities of compounds A (IC_50-dark = 19.2 ± 0.97 μM), B (>100 μM), 1 (11.4 ± 0.47 μM), and 2 (62.4 ± 9.1 μM) after they were incubated for 48 h with U-87 MG. Data points show mean ± SD (n = 8).

Figure 2

Light and dark cytotoxicities of (a) 1 and (b) 2 on U87-MG cells after incubation for 6 and 24 h in DMEM containing 10% FBS. Cells were washed twice with pH 7.4 PBS, and the medium was changed to pH 7.4 ACAS, followed by irradiation (3.8 mW/cm²) for 20 min and dark incubation for 24 h. Viabilities were determined using AlamarBlue. Data points show mean ± SD (n = 8).

Figure 3

Biodistribution and clearance of compounds 1 and 2 in CD-1 mice (25 nmol of each compound injected iv 4 h prior to imaging). (a) Shown are representative (left) color and (right) NIR fluorescence images of the thoracic cavity, abdominal cavity, and post mortem in resected organs. (b) Signal-to-background ratio (SBR) for resected organs (Or) against muscle (Mu). (c) Percent injected dose (%ID) of compounds in plasma at each time point calculated from fluorescence signal intensities 4 h postadministration (n = 3 or 5, mean ± SD). Abbreviations: Bl, bladder; Du, duodenum; Ga, gall bladder; He, heart; In, intestine; Ki, kidney; Mu, muscle; Li, liver; Lu, lung; Pa, pancreas; Sp, spleen. Excitation was at 760 nm (4 mW/cm²), and emission was at 790–850 nm. All NIR fluorescence images for each fluorophore were normalized identically for all conditions during an experiment.

Figure 4

Tumor targeting and biodistribution of compounds 1 and 2 in NIT-1 tumor-bearing mice. Each compound (35 nmol) was injected iv 4 h prior to imaging. Shown are representative (left) color and (right) NIR fluorescence images of (a) the thoracic cavity, (b) the abdominal cavity, (c) resected organs, (d) neck/axillary, (e) tumor, and (f) resected tumor (Tu) and muscle (Mu). Arrows indicate lymph nodes. The tumor-to-background ratios (TBRs) of 1 and 2 were 6.5 ± 2.55 and 8.98 ± 2.17, respectively. Data points are displayed as mean ± SD, and the p values were evaluated using Student’s t test. Abbreviations: Bl, bladder; BM, bone marrow; Du, duodenum; Ga, gall bladder; He, heart; In, intestine; Ki, kidney; Mu, muscle; Li, liver; Lu, lung; Pa, pancreas; Sp, spleen; Ur, ureter. Excitation was at 760 nm (4 mW/cm²), and emission was at 790–850 nm. All NIR fluorescence images for each fluorophore were normalized identically for all conditions during an experiment.