Indocyanine green (ICG) and laser irradiation induce photooxidation

Abstract

The cellular uptake and subcellular localization of indocyanine green (ICG; absorption band 700-850 nm), and cell survival and ultrastructural changes following ICG-mediated phototherapy were investigated in vitro in four different cell lines derived from human skin (SCL1 and SCL2 squamous cell carcinoma, HaCaT keratinocytes and N1 fibroblasts). The cellular uptake of ICG (1-50 microM, incubation times 1, 4, 24 h) was saturable, highly cumulative and could be inhibited by the addition of 250 microM bromosulphophthalein indicating the involvement of the organic anion transporting polypeptide (OATP). For HaCaT cells, the maximum cellular uptake (Vmax) and the Michaelis constant (K(m)) were 9.9 +/- 1.1 mM and 47 +/- 16 microM, respectively, following a 24-h incubation with ICG. Fluorescence microscopy revealed a cytoplasmic distribution of ICG, probably bound to glutathione S-transferase. Following irradiation with a cw-diode laser (805 nm, 80 mW/cm2) at doses of 24 or 48 J/cm2, the phototoxicity was determined using the MTT assay as a measure of cell viability. For all cell lines, ICG concentrations above 25 microM produced a significant phototoxic effect. The EC50, of ICG for HaCaT cells following irradiation at 24 J/cm2 was 20.1 +/- 3.9 microM. Growth curves showed that even HaCaT cells treated at the EC50 were killed within a week following treatment. Electron microscopy 1 h after ICG-mediated phototherapy revealed cytoplasmic vesiculation, dilation of the rough endoplasmic reticulum, the Golgi complex and the perinuclear cisternae and the beginning of chromatin condensation in the nucleus. These ultrastructural findings are not consistent with a photothermal action of ICG-mediated phototherapy. Taken together with those of previous studies by our group these results support photooxidation as a major cell-killing mechanism.

Morphological Study in B16F10 Murine Melanoma Cells after Photodynamic Hyperthermal Therapy with Indocyanine Green (ICG)

“…ICG and other photosensitizers (PSs) can be uptaked by normal and cancer cells in vitro, followed by photooxidation if irradiated [2,32]. However, in vivo PSs selectively accumulate in the tumor due to the absence of lymphatic drainage and leaky blood vessels from bizarre neovascularization [7].…”

“…Based on this property, many in vivo and in vitro experiments have been performed [8,34]. Hirano et al [17] first demonstrated that ICG could induce singlet oxygen formation in response to light with a wavelength between 600-800 nm, which means that ICG has properties that could make it useful as a photosensitizer during photodynamic therapy (PDT) [2]. We noticed this property of ICG and developed a new cancer therapy based on the properties of ICG and a broad band light source that emits light of 600-800 nm to create a combination modality utilizing both photodynamic therapy (PDT) and hyperthermia.…”

Non-conventional therapeutics for oral infections

“…Answers to all of these questions are not readily available or universally applicable to all bacteria. However, in relation to (1) and (2) it is known that sensitizing agents can give rise to phototoxic effects on keratinocytes and fibroblasts 49 and phototoxic reactions in experimental animal oral tissues have been recorded, although the effect appears to be short lived. 50 The photosensitizer erythrosine has an advantage over some other dyes because it is currently used in dentistry to visualize dental plaque in vivo, and so its lack of direct toxicity on the host is well established.…”

Cancer Therapy Combining Modalities of Hyperthermia and Chemotherapy: in vitro Cellular Response after Rapid Heat Accumulation in the Cancer Cell

“…Most researches are focusing on its photodynamic effect [98,99] which involves the generation of reactive oxygen free radicals (mostly singlet oxygen) to kill cancer cell by photooxidation. ICG is capable of producing both a photodynamic and photothermal effect using a NIR laser, depending on the laser's power density.…”

“…As described before, ICG absorbs laser energy and converts it to heat; therefore, it is reasonable to hypothesize that the intracellular binding site of ICG would be the direct target in the proposed hyperthermia. The transport kinetics and subcellular localization of ICG has been studied extensively by various research groups [98,101]. Both groups showed that ICG is taken up by the cells through a carrier-mediated transport process against a concentration gradient.…”