Photodynamic therapy - from dyestuffs to high-tech clinical practice

The In-Vitro Effect of Homeopathically Prepared Rubus idaeus and 680 nm Laser Irradiation on Cervical Cancer Cells

BACKGROUND

 Cervical cancer (CC) is the second leading cancer in women and is the most common in those aged 15 to 44 years. Medicinal plant extracts have been used as homeopathic preparations for health benefits. Rubus idaeus (RI) is used to treat disorders of the female genital tract and produces cytotoxic effects. However, the use of homeopathically prepared RI in combination with low level laser therapy has not previously been explored.

AIM

 The study aims to investigate the in-vitro effects of homeopathically prepared RI alone and in combination as a potential photosensitizer with Low-level laser irradiation (LLLI) at fluencies of 5, 10, and 15 J/cm².

METHODS

 HeLa CC cells were treated with RI (D3, D6, and 30cH homeopathic preparations). Cells were then treated with RI IC₅₀ and 680 nm laser diode at 5, 10, and 15 J/cm² fluencies, and the results compared with untreated control cells. Trypan blue viability, lactate dehydrogenase (LDH) cytotoxicity, and adenosine triphosphate (ATP) proliferation assays were used to analyze the cellular dose-responses along with inverted microscopy, Hoechst staining and Annexin-V/PI staining.

RESULTS

 RI D3 alone demonstrated an ability to reduce cellular viability to 59% and also to reduce ATP levels. The subsequent combined treatment protocol of RI D3 with all fluencies of laser demonstrated an increase in cellular ATP and increased LDH levels compared with the control.

CONCLUSION

 The increased ATP and LDH levels observed in the combined treatment protocol of 680 nm laser and RI D3 at fluencies of 5, 10 and 15 J/cm², show that the Warburg effect might have been induced in the CC cells - an increase in glucose uptake and the preferential production of lactate, even in the presence of oxygen. More research, including work on other cell lines, needs to be conducted to identify if RI and perhaps a different wavelength of laser irradiation could have potential in inducing cell death in cancer cells.

Photophysical characterization and in vitro anti-leishmanial effect of 5,10,15,20-tetrakis(4-fluorophenyl) porphyrin and the metal (Zn(II), Sn(IV), Mn(III) and V(IV)) derivatives

In this report 5 compounds were synthesized and structural and their photophysical characterization was performed (Φ_Δ and Φ_f). Furthermore, in this in vitro study, their biological activity against Leishmania panamensis was evaluated. The photophysical behavior of these compounds was measured and high Φ_Δ and low Φ_f was observed. Besides, DFT quantum calculations on the electronic structures were performed. Finally, the biological activity was determined by means of the compounds capacity to inhibit the viability of parasites using the MTT assay. The inclusion of the metal ions substantially modified the photophysical and biological properties in comparison with the free metal porphyrin (1). In fact, Zn²⁺ porphyrin derivative (2) showed a marked decrease of Φ_f and increase of Φ_Δ. In this sense, using TDDFT approaches, a luminescent process for Sn⁴⁺ derivative (3) was described, where emissive states involve the ML-LCT transition. So, this led to a decrease in the singlet oxygen production (0.82-0.67). Biological results showed that all compounds inhibit the viability of L. panamensis with high efficiency; the decrease in the viability was greater as the concentration of exposure increased. Finally, under light irradiation the IC₅₀ of L. panamensis against the Zn(II)-porphyrin (2) and V(IV)-porphyrin (5) was lower than the IC₅₀ of the Glucantime control (IC₅₀ = 2.2 and 6.95 μM Vs IC₅₀ = 12.7 μM, respectively). We showed that the use of porphyrin and metalloporphyrin-type photosensitizers with exceptional photophysical properties can be successful in photodynamic therapy (PDT) against L. panamensis, being the diamagnetic ion Zn²⁺ a candidate for the preparation of metalloporphyrins with high singlet oxygen production.

Phthalocyanine pigments: general principles

This chapter describes some of the fundamental chemical and structural principles underlying the phthalocyanine system. Historically, phthalocyanines had been isolated as insoluble blue products in the early twentieth century, although the structures were not established at the time. After the serendipitous re-discovery of metal complex phthalocyanines by industry, and the elucidation of their structures, copper phthalocyanine (CuPc) pigments were introduced industrially in the 1930s to become, and remain, by far the most important blue and green organic pigments, finding almost universal use as colorants for paints, printing inks, plastics, and a wide range of other applications. The phthalocyanines have become one of the most extensively studied classes of organic compounds, because of their unique molecular structures, light absorption properties that produce strong, bright colors, and their exceptionally high stability. While their dominant use is as colorants, they are also of interest for a range of other applications, for example in electronic devices, biological applications, and as catalysts.

Synthesis, Photophysical Properties and Application of New Porphyrin Derivatives for Use in Photodynamic Therapy and Cell Imaging

New derivatives of tetrakis(4-carboxyphenyl) porphyrin were designed, synthesized and characterized by IR, proton NMR and mass spectroscopy. The ground and excited state nature of new derivatives were examined using UV-Vis. absorption and fluorescence spectroscopy, fluorescence quantum yield and fluorescence lifetime studies. The singlet oxygen quantum yield of each synthesized derivative of porphyrin was estimated for their further efficacy as potential photosensitizer in biological studies. The significant photophysical data of all synthesized derivatives was supplementary accessed to examine the cell imaging and cytotoxicity against two cancer cell lines viz. MBA-MD-231 and A375. The fluorescence lifetime, fluorescence quantum yield and efficiency of singlet oxygen generation suggests alkyl amine and alkyl hydrazide linked new porphyrin photosensitizers can be useful for PDT agent in cancer treatment.

In Vitro Photodynamic Effect of Phycocyanin against Breast Cancer Cells

C-phycocyanin, a natural blue-colored pigment-protein complex was explored as a novel photosensitizer for use in low-level laser therapy under 625-nm laser illumination. C-phycocyanin produced singlet oxygen radicals and the level of reactive oxygen species (ROS) were raised in extended time of treatment. It did not exhibit any visible toxic effect in the absence of light. Under 625-nm laser irradiation, c-phycocyanin generated cytotoxic stress through ROS induction, which killed MDA-MB-231 breast cancer cells depending on concentrations. Different fluorescent staining of laser-treated cells explored apoptotic cell death characteristics like the shrinking of cells, cytoplasmic condensation, nuclei cleavage, and the formation of apoptotic bodies. In conclusion, phycocyanin is a non-toxic fluorescent pigment that can be used in low-level light therapy.

Developments in PDT Sensitizers for Increased Selectivity and Singlet Oxygen Production

Photodynamic therapy (PDT) is a minimally-invasive procedure that has been clinically approved for treating certain types of cancers. This procedure takes advantage of the cytotoxic activity of singlet oxygen (¹O₂) and other reactive oxygen species (ROS) produced by visible and NIR light irradiation of dye sensitizers following their accumulation in malignant cells. The main two concerns associated with certain clinically-used PDT sensitizers that have been influencing research in this arena are low selectivity toward malignant cells and low levels of ¹O₂ production in aqueous media. Solving the selectivity issue would compensate for photosensitizer concerns such as dark toxicity and aggregation in aqueous media. One main approach to enhancing dye selectivity involves taking advantage of key methods used in pharmaceutical drug delivery. This approach lies at the heart of the recent developments in PDT research and is a point of emphasis in the present review. Of particular interest has been the development of polymeric micelles as nanoparticles for delivering hydrophobic (lipophilic) and amphiphilic photosensitizers to the target cells. This review also covers methods employed to increase ¹O₂ production efficiency, including the design of two-photon absorbing sensitizers and triplet forming cyclometalated Ir(III) complexes.

Dye Sensitizers for Photodynamic Therapy

Photofrin^® was first approved in the 1990s as a sensitizer for use in treating cancer via photodynamic therapy (PDT). Since then a wide variety of dye sensitizers have been developed and a few have been approved for PDT treatment of skin and organ cancers and skin diseases such as acne vulgaris. Porphyrinoid derivatives and precursors have been the most successful in producing requisite singlet oxygen, with Photofrin^® still remaining the most efficient sensitizer (quantum yield = 0.89) and having broad food and drug administration (FDA) approval for treatment of multiple cancer types. Other porphyrinoid compounds that have received approval from US FDA and regulatory authorities in other countries include benzoporphyrin derivative monoacid ring A (BPD-MA), meta-tetra(hydroxyphenyl)chlorin (m-THPC), N-aspartyl chlorin e6 (NPe6), and precursors to endogenous protoporphyrin IX (PpIX): 1,5-aminolevulinic acid (ALA), methyl aminolevulinate (MAL), hexaminolevulinate (HAL). Although no non-porphyrin sensitizer has been approved for PDT applications, a small number of anthraquinone, phenothiazine, xanthene, cyanine, and curcuminoid sensitizers are under consideration and some are being evaluated in clinical trials. This review focuses on the nature of PDT, dye sensitizers that have been approved for use in PDT, and compounds that have entered or completed clinical trials as PDT sensitizers.

It must be green: meeting society’s environmental concerns

Consumers today are increasingly demanding goods which not only conform to the public’s image of being ‘eco‐friendly’ and ‘organic’ but of having been produced ‘ethically’. Meeting such high ideals has a down side, both in higher costs and often in that of having to accept more distant suppliers. Present trends in the coloration of foods with natural dyes rather than synthetic ones, increasing consumption of organic products (including fibres) and energy‐saving trends in dye application methods, fuels and lighting, as well as the means of capturing solar energy, are discussed. The discovery of some interesting and historic green colours, the wider use of green (in both senses of the word) products and green chemistry’s future role in producing them are also reviewed.