br The change in localization from the cytoplasm to
The change in localization from the cytoplasm to the nucleus by Pc2 after irradiation offers potential insight into the mechanism of cell death. One possibility for the accumulation of Pc2 in the nucleus after irradiation is membrane permeabilization by reactive oxygen species. This process involves dilating the endoplasmic reticulum, poking holes in the nuclear membrane, and allowing Pc2 access to its preferred DNA binding partner. The morphological changes that occur simultaneously with Pc2 re-localization are not mere symptoms of apoptosis but rather post-mortem events that occur, often hours after initiation of apoptosis . However, we can detect morphological changes and re-localiza-tion of Pc2 in as little as 5 min after irradiation. Mitochondrial outer membrane permeabilization occurs in late stage apoptosis and releases
Fig. 9. Visualization of changes in cell morphology (phase contrast - grey), nuclear compaction (DAPI-blue) and DNA damage response (H2AX(P139S)-green) in MCF-7 2763-96-4 in response to treatment with and excitation of Pc1 and Pc2 compounds. Where possible the CY5 channel (red) was used to monitor the phthalocyanine compound.
caspase enzymes into the cytoplasm, essentially committing the cell to death in as little as 10 min . Membrane permeabilization by ROS generation was a mechanism proposed for a silicone phthalocyanine
that is in clinical trial for treating cutaneous neoplasms [71,72]. Rapid ROS production by Pc1 and Pc2 during irradiation leading to mem-brane permeabilization is consistent with the observed cell death
Fig. 10. Live cell imaging of MCF-7 cells treated with Pc2 (A) or Pc1 (B) and irradiated for 1 min, and monitored at time points for 30 min. The Cy5 channel allowed tracking of the Pc2 dye throughout the course of the experiment.
timeline as well as the re-localization of Pc2 after irradiation.
Two cationic zinc phthalocyanine photosensitizers (Pc1 and Pc2) have been tested for DNA binding with three different DNA structures. It has been shown that tetracationic Pc1 is highly aggregated while octacationic Pc2 stays predominantly monomeric in aqueous solution, and both have high binding affinities to SS-DNA, DS-DNA and G4-DNA under physiological conditions. The photodynamic activity of the Pc1 and Pc2 photosensitizers was demonstrated with in vitro experiments, which indicated a strong potential for the use of these photosensitizers in the photodynamic therapy of cancer. It was found that the photo-dynamic action in the in vitro experiments differ significantly from each other as Pc1 is less stable than Pc2. Both Pc1 and Pc2 are mostly present in the cytoplasmic area pre-irradiation; however, only the Pc2 photosensitizer was observed to be localized in the cell nuclei post-ir-radiation, while the Pc1 photosensitizer decayed upon visible light exposure. Both photosensitizers are very efficient in the generation of single oxygen species which results in high phototoxicity and apoptosis of cells.
This work was supported by the Minnesota Supercomputing Institute, NSERC, CFI, University of Manitoba, and WestGrid Canada. We also would like to acknowledge Professor Lukyanets for the samples of Pc1 and Pc2.
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Colloids and Surfaces B: Biointerfaces
journal homepage: www.elsevier.com/locate/colsurfb
Biocompatibility and eﬀectiveness of paclitaxel-encapsulated micelle using T phosphoester compounds as a carrier for cancer treatment
Issei Takeuchia,b, Kimiko Makinoa,b,
a Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641, Yamazaki, Noda, Chiba 278-8510, Japan
b Center for Drug Delivery Research, Tokyo University of Science, 2641, Yamazaki, Noda, Chiba 278-8510, Japan
Phosphoester compounds are promising materials with expected biocompatibility; however, little has been re-ported on the use of phosphoester compounds for micelle formulations. In this study, paclitaxel (PTX)–encapsulated micelles were prepared using four kinds of alkyl di(MePEG-lactate) phosphates. From the results of the determination of critical micelle concentrations and an in vitro stability test, it was shown that a compound to which 1-eicosanol was introduced as a side chain was desirable in the preparation of PTX-en-capsulated micelles (PTX-micelles). The mean volume diameter and PTX content of the micelles were 135.7 ± 52.2 nm and 3.9% ± 0.2%, respectively. in vitro release tests of the micelles were performed at dif-ferent pH levels. Twenty-four hours after the start of the release test, the cumulative PTX release rate of PTX-micelles at pH 5.0 reached 96.2%, which was three times higher than that at pH 7.4. As a result of the de-gradation test of the compound used for the micelle, it was confirmed that this compound degraded faster at pH 5.0 than at pH 7.4. The hemolysis rate of drug-free micelles was 0.8%–1.4%, and the biocompatibility of this micelle as a drug carrier was suggested. In addition, the eﬀectiveness of PTX-micelles in cancer treatment was evaluated via biodistribution study. PTX concentration in the tumor was significantly increased in the group administered PTX-micelles as compared with the group administered PTX solution. These results suggest that phosphoester compounds are useful in preparing biocompatible pH-responsive carriers.