Protoporphyrin IX photobleaching of subcellular distributed sites of leukemic HL60 cells based on ALA-PDT <i>in vitro</i>

Abstract

The leukaemia cells HL60, incubated in 10 mM/ml ALA (5-aminolevulinic) for 4 hours, were carried an experimental research with fluorescent probes in photodynamic therapy (PDT) based on ALA by using PDT reaction room (The average fluence rate of the 412 nm source was 5 mW/cm<sup>2</sup>). Cells viability were determined using a Cell Counting Kit-8 (CCK-8) assay, and PpIX Photobleaching of subcellular distributed sites of HL60 cells in vitro were investigated by fluorescence spectra acquired during treatment. The results showed that the fluorescence intensity of mitochondria, lysosomes, endoplasmic reticulum had decreased by 81.5%, 52.3% and 21.0%, respectively, compared with their initial values after a 45-minute light treatment. The rate of PpIX photobleaching in mitochondria was significantly higher than others. Addi-tionally, the change of the activity of HL60 cells was basically characterized by the change fluorescence intensity in mitochondria, which suggest that mitochondria is one of main therapeutic targets of photodynamic therapy

Photobleaching and phototoxicity of KillerRed in tumor spheroids induced by continuous wave and pulsed laser illumination

“…Photoinduced decarboxylation, driven by electron acceptance from a neighboring Glu, has previously been assumed for GFP and DsRed . X‐ray structure analysis of the bleached KillerRed chromophore revealed at least partial breakage of the conjugated π‐system at the methylene bridge .…”

“…Since the lowering of fluorescence results from a direct attack of ROS or singlet oxygen on the photosensitizer molecules, it reflects the efficiency of the photochemical reaction and can potentially predict the outcome of the therapy. The relation between photobleaching, singlet oxygen and the PDT response has been investigated in models in vitro and in vivo for a range of photosensitizers including Photofrin , Photogem , mTHPC , 5‐ALA induced protoporphyrine IX and benzoporphryin‐derivative BPD . In the experiments with mTHPC in vitro Jarvi et al showed that photobleaching can be used as a PDT dose metric, but this approach failed under hypoxic conditions .…”

“…However, many chemical photosensitizers exhibit complicated bleaching mechanisms, which include both 1 O 2 ‐mediated and triplet state‐mediated pathways. As a result, the kinetics of bleaching depend on many factors, such as the initial sensitizer concentration, oxygen concentration and the light fluence rate, demonstrating non‐linear and even multiphase behavior .…”

Mass Spectrometric Analysis of the Photobleaching of Protoporphyrin IX Used in Photodynamic Diagnosis and Therapy of Cancer

“…The use of photodynamic diagnosis and therapy (PDD and PDT) for cancer diagnosis and treatment are becoming more widespread due to its minimally invasive and highly selective nature (1–5). The photodynamic technique utilizes the photochemical reaction of a photosensitizer that is initiated when a specific wavelength of light is absorbed.…”

“…The diagnosis and treatment efficacy of the PDD and PDT is dependent on the monitoring, dosimetry estimation and understanding of the mechanism of the photodynamic (PD) processes. Photobleaching and photoproducts formations are phenomena essential in studying these factors, and the study of these phenomena during the PD processes has been increasing (2,7–9).…”