Unveiling Ga(III) phthalocyanine-a different photosensitizer in neuroblastoma cellular model

Abstract

Phthalocyanines (Pc) and their metallated derivatives are strongly considered for photodynamic therapy (PDT) possessing unique properties as possible new photosensitizers (PS). We have used toxicological assessments, real-time monitoring of cellular impedance, and imagistic measurements for assessing the in vitro dark toxicity and PDT efficacy of Ga(III)-Pc in SHSy5Y neuroblastoma cells. We have established the non-toxic concentration range of Ga(III)-Pc, a compound which shows a high intracellular accumulation, with perinuclear distribution in confocal microscopy. By choosing Ga(III)Pc non-toxic dose, we performed in vitro experimental PDT hampering cellular proliferation. Our proposed Ga(III)-Pc could complete a future PS panel for neuroblastoma alternate therapy.

Keywords: gallium(III); neuroblastoma; photodynamic therapy; photosensitizer; proliferation; toxicity; tumour; viability.

Figure 1

(A) Cellular viability assessed as lactate dehydrogenase (LDH) index for SHSy5Y cells incubated with Ga(III)Pc for different time‐points. (B) Cellular proliferation index for SHSy5Y cells incubated with Ga(III)Pc at different time‐points—assessed by MTS reduction in metabolically active cells

Figure 2

Cell index for SHSy5Y cells treated with Ga(III)Pc; 2000 cells/well; red = control (unloaded cells), green = DMSO, dark blue = 2 μg/mL GaPcCl; purple = 10 μg/mL Ga(III)Pc; light blue = 50 μg/mL Ga(III)Pc; black arrow detail—point when compound Ga(III)Pc is added to cells

Figure 3

Cellular index (CI) for cellular impedance measurements—automated CI for 2, 24, 48, 72, and 120 h of SHSy5Y treated with various doses of Ga(III)Pc

Figure 4

Confocal microscopy of SHSy5Y cells treated with Ga(III)Pc, showing the distribution of the compound. (A) Control—SHSy5Y cells without Ga(III)Pc, stained with phalloidin for F‐actin (green) and DAPI (blue). (B) SHSy5Y cells loaded with Ga(III)Pc (red) and stained with phalloidin (green) and DAPI (blue) show similar morphology to control cells. (C) Digital zoom of SHSy5Y cells loaded with Ga(III)Pc (red), showing a cytosolic, predominantely perinuclear distribution of the compound

Figure 5

(A) Lactate dehydrogenase (LDH) release after experimental photodynamic therapy (PDT) of SHSy5Y loaded with 10 μg/mL Ga(III)Pc. (B) Proliferation index after experimental PDT of SHSy5Y loaded with 10 μg/mL Ga(III)Pc

Figure 6

Impedance measurements results—cell index at first 24 h post‐PDT; (A) detail on first 18 h of monitoring; (B) detail on first 2 h of monitoring

Figure 7

Cellular index of irradiated SHSy5Y cells loaded with Ga(III)Pc 10 μg/mL after different time periods cultivation post‐irradiation