Evaluation of Ruthenium-Based Assemblies as Carriers of Photosensitizers to Treat Rheumatoid Arthritis by Photodynamic Therapy

Abstract

For the first time, ruthenium-based assemblies have been used as carriers for photosensitizers in the treatment of rheumatoid arthritis by photodynamic therapy (PDT). These metallacages are totally soluble in physiological media and can transport photosensitizers (PS) in their cavity. After an incubation period, the PS is released in the cytoplasm and irradiation can take place. This strategy allows photosensitizers with low or null solubility in biological media to be evaluated as PDT agents in rheumatoid arthritis. The systems in which 21H,23H-porphine and 29H,31H-phthalocyanine are encapsulated show excellent photocytotoxicity and no toxicity in the dark. On the other hand, systems in which metalated derivatives such as Mg(II)-porphine and Zn(II)-phthalocyanine are used show good photocytotoxicity, but to a lesser extent than the previous two. Furthermore, the presence of Zn(II)-phthalocyanine significantly increases the toxicity of the system. Overall, fifteen different host-guest systems have been evaluated, and based on the results obtained, they show high potential for treating rheumatoid arthritis by PDT.

Keywords: COX-2; arene ruthenium complexes; drug delivery; host–guest system; photodynamic therapy; photosensitizer; rheumatoid arthritis.

Figure 1

Typical ruthenium-based assemblies used as PS carrier for cellular internalization and subsequent activation of PS by irradiation, giving rise to ROS.

Figure 2

Photosensitizers used in this work. From left to right, 21H,23H-porphine (G1), Mg(II)-porphine (G2), 29H,31H-phthalocyanine (G3) and Zn(II)-phthalocyanine (G4).

Figure 3

Structures of ruthenium(II) metallacages used in this work. The photosensitizer is represented by a sphere (PS), 21H,23H-porphine (G1) was inserted in M1–M6, Mg(II)-porphine (G2) in M1, M4, and M6, 29H,31H-phthalocyanine (G3) and Zn(II)-phthalocyanine (G4) in M4–M6.

Figure 4

Emission spectra of M5 with G3 or G4 (left) and M6 with G1 or G2 (right), in DMSO at 25 °C (10 nM concentration).

Figure 5

MTT assays of G3⊂M6 (black) and G4⊂M6 (red), in the dark (dashed line) and after irradiation (solid line). Statistical significance determined by the two-tailed unpaired Student’s t-test, p-value < 0.001 (***).

Figure 6

Effects of the systems tested on COX-2 expression after PDT. The numbers correspond to the entries in Table 1. Cells (2 × 10⁶) were cultured in DMEM medium (FBS 10%, L-glutamine 1%, penicillin 100 U/mL, Streptomycin 100 µg/mL) for 24 h and treated with the corresponding system G⊂M. After 24 h, the medium was replaced by a DMEM medium without red phenol, and then irradiated (RI) or not (NI) by 630 nm irradiation (40 mW/cm², 30 min). After 18 h, LPS (1 µg/mL) was added to the medium to stimulate the expression of COX-2, and 4 h later the trypsination was carried out. COX-2 expression was determined by Western Blot and β-actin was used as a protein loading control. All experiments were done in triplicate.