All organic nanomedicine for PDT-PTT combination therapy of cancer cells in hypoxia

Abstract

Photodynamic and photothermal therapies are promising treatments for cancer, dermatological, and ophthalmological conditions. However, photodynamic therapy (PDT) is less effective in oxygen-deficient tumor environments. Combining PDT with photothermal therapy (PTT) can enhance oxygen supply and treatment efficacy. Inorganic PTT agents pose toxicity risks, limiting their clinical use despite their high performance. In this study, we developed a novel nanomedicine integrating an all-organic photothermal agent and an organic photosensitizer, creating a colocalized nanoplatform to enhance phototherapy efficacy in cancer treatment. PTT nanoparticles (NPs) were synthesized through a thermal phase transition of organic chromophores, demonstrating superior photothermal properties and photostability. Utilizing this nanoplatform, we devised 'Combi NPs' for combined PDT-PTT nanomedicine. Tests on A549 cancer cell lines have revealed that Combi NPs exhibit superior cytotoxicity and induce apoptosis in hypoxic conditions, outperforming PTT-only NPs. The all-organic Combi NPs show significant potential for clinical cancer phototherapy in hypoxic microenvironments, potentially mitigating long-term nanomedicine accumulation and associated toxicity.

Keywords: Combination therapy; Hypoxia; Nanomedicine; Photodynamic therapy; Photothermal therapy.

Figure 1

Schematic representation illustrating the preparation of the all organic nanomedicine for PDT-PTT combination therapy (a), and its operational mechanism in synergistic tumor therapy (b). Figure 1 was created using BioRender.com.

Figure 2

Characteristics of PTA NPs. (a) Photographs showcasing the dark blue PcBu4 PTA and dark brown OBNC PTA suspensions. (b) Normalized absorbance spectra of PcBu4 PTA and OBNC PTA suspensions. (c) TEM images of PcBu4 NPs with a scale bar representing 50 nm. (d) Photothermal properties of PcBu4 PTA when illuminated with a 671 nm laser at 6.4 W/cm² for 15 min.

Figure 3

Characteristics of Combi and PTT NPs. (a) TEM image of PTT (left) and Combi (right) NPs. Scale bars represent 100 nm. (b) Results of singlet oxygen detection test upon monochromatic light illumination (635 nm monochromatic Xe lamp (0.2 mW/cm² at 635 nm)). (c) Cell viability assay evaluating material toxicity. Bars represent mean ± SD (n = 5). Statistical significance was determined using One-Way ANOVA; significant differences were observed among 9 groups, F(8,36) = 19.7889, p < 0.05. (d) Hypoxic test with DCFH-DA staining. Bars indicate mean ± SD (n = 4). The statistical significance was analyzed using a Student’s T-test: *p < 0.05.

Figure 4

Phototoxicity test under normoxic (a) and hypoxic (b) conditions. 635 nm monochromatic Xe lamp (0.2 mW/cm² at 635 nm) was illuminated. The light illumination time is represented at the bottom of the graphs. Bars represent mean ± SD (n = 4). Statistical significance was analyzed using a Student’s T-test (*p < 0.10) and One-Way ANOVA; significant differences were observed among the 5 groups, F(4,15) = 12.0497, p < 0.05.

Figure 5

Fluorescence images of A549 cells in hypoxic conditions that were either untreated (labeled as ‘Cell + Media’) or photo-treated with Combi or PTT NPs. For the photo-treatment, a 635 nm monochromatic Xe lamp (0.2 mW/cm² at 635 nm) was illuminated for 5 min. Cells were assayed using the Annexin V kit. Scale bars represent 100 μm.