Podcasts about ix ppix

In order to deliver drugs to diseased cells nanoparticles featuring controlled drug release are developed. Controlled release is of particular importance for the delivery of toxic anti-cancer drugs that should not get in contact with healthy tissue. To evaluate the effectivity and controlled drug release ability of nanoparticles in the target cell, live-cell imaging by highly-sensitive fluorescence microscopy is a powerful method. It allows direct real-time observation of nanoparticle uptake into the target cell, intracellular trafficking and drug release. With this knowledge, existing nanoparticles can be evaluated, improved and more effective nanoparticles can be designed. The goal of this work was to study the internalization efficiency, successful drug loading, pore sealing and controlled drug release from colloidal mesoporous silica (CMS) nanoparticles. The entire work was performed in close collaboration with the group of Prof. Thomas Bein (LMU Munich), where the nanoparticles were synthesized. To deliver drugs into a cell, the extracellular membrane has to be crossed. Therefore, in the first part of this work, the internalization efficiency of PEG-shielded CMS nanoparticles into living HeLa cells was examined by a quenching assay. The internalization time scales varied considerably from cell to cell. However, about 67% of PEG-shielded CMS nanoparticles were internalized by the cells within one hour. The time scale is found to be in the range of other nanoparticles (polyplexes, magnetic lipoplexes) that exhibit non-specific uptake. Besides internalization efficiency, successful drug loading and pore sealing are important parameters for drug delivery. To study this, CMS nanoparticles were loaded with the anti-cancer drug colchicine and sealed by a supported lipid bilayer using a solvent exchange method (additional collaboration with the group of Prof. Joachim Rädler, LMU). Spinning disk confocal live-cell imaging revealed that the nanoparticles were taken up into HuH7 cells by endocytosis. As colchicine is known to exhibit toxicity towards microtubules, the microtubule network of the cells was destroyed within 2 h of incubation with the colchicine-loaded lipid bilayer-coated CMS nanoparticles. Although successful drug delivery was shown, it is necessary to develop controlled local release strategies. To achieve controlled drug release, CMS nanoparticles for redox-driven disulfide cleavage were synthesized. The particles contain the ATTO633-labeled amino acid cysteine bound via a disulfide linker to the inner volume. For reduction of the disulfide bond and release of cysteine, the CMS nanoparticles need to get into contact with the cytoplasmic reducing milieu of the target cell. We showed that nanoparticles were taken up by HuH7 cells via endocytosis, but endosomal escape seems to be a bottleneck for this approach. Incubation of the cells with a photosensitizer (TPPS2a) and photoactivation led to endosomal escape and successful release of the drug. In addition, we showed that linkage of ATTO633 at high concentration in the pores of silica nanoparticles results in quenching of the ATTO633 fluorescence. Release of dye from the pores promotes a strong dequenching effect providing an intense fluorescence signal with excellent signal-to-noise ratio for single-particle imaging. With this approach, we were able to control the time of photoactivation and thus the time of endosomal rupture. However, the photosensitizer showed a high toxicity to the cell, due to its presence in the entire cellular membrane. To reduce cell toxicity induced by the photosensitizer and to achieve spatial control on the endosomal escape, the photosensitizer protoporphyrin IX (PpIX) was covalently surface-linked to the CMS nanoparticles and used as an on-board photosensitizer (additional collaboration with the groups of Prof. Joachim Rädler and Prof. Heinrich Leonhardt, both LMU). The nanoparticles were loaded with model drugs and equipped with a supported lipid bilayer as a removable encapsulation. Upon photoactivation, successful drug delivery was observed. The mode of action is proposed as a two step cascade, where the supported lipid bilayer is disintegrated by singlet oxygen in a first step and the endosomal membrane ruptures enabling drug release in a second step. With this system, stimuli-responsive and controlled, localized endosomal escape and drug release is achieved. Taken together, the data presented in this thesis show that real-time fluorescence imaging of CMS nanoparticles on a single-cell level is a powerful method to investigate in great detail the processes associated with drug delivery. Barriers in the internalization and drug delivery are detected and can be bypassed via new nanoparticle designs. These insights are of great importance for improvements in the design of existing and the synthesis of new drug delivery systems.

OBJECTIVE: In order to expand the use of photodynamic therapy (PDT) in the treatment of prostate carcinoma (PCA), the aim of this study was to evaluate PDT by means of 5-aminolevulinic acid (5-ALA)-induced protoporphyrin IX (PPIX) in an in vivo tumor model. METHODS: The model used was the Dunning R3327 tumor. First of all, the pharmacokinetics and the localization of PPIX were obtained using fluorescence measurement techniques. Thereafter, PDT using 150 mg 5-ALA/kg b.w. i.v. was performed by homogenous irradiation of the photosensitized tumor (diode laser lambda = 633 nm). The tumors were resected 2 days post-PDT and the extent of the necrosis was determined histopathologically. RESULTS: The kinetics of PPIX fluorescence revealed a maximum intensity in the tumor tissue within 3 and 4.5 h post-application of 5-ALA. At this time, specific PPIX fluorescence could be localized selectively in the tumor cells. The PDT-induced necrosis (n = 18) was determined to be 94 +/- 12% (range 60-100%), while the necrosis of the controls (n = 12) differs significantly (p < 0.01), being less than 10%. CONCLUSION: These first in vivo results demonstrate the effective potential of 5-ALA-mediated PDT on PCA in an animal model.

Lung cancer is one of the most common malignancies in the world and remains the leading cause of cancer death among men and women in developed countries, accounting for more deaths than breast, prostate and colorectal cancers combined. The cure for lung cancer is low (

Objective: In order to expand the use of photodynamic therapy (PDT) in the treatment of prostate carcinoma (PCA), the aim of this study was to evaluate PDT by means of 5-aminolevulinic acid (5-ALA)-induced protoporphyrin IX ( PPIX) in an in vivo tumor model. Methods: The model used was the Dunning R3327 tumor. First of all, the pharmacokinetics and the localization of PPIX were obtained using fluorescence measurement techniques. Thereafter, PDT using 150 mg 5-ALA/kg b.w.i.v. was performed by homogenous irradiation of the photosensitized tumor (diode laser lambda = 633 nm). The tumors necrosis was determined histopathologically. Results: The kinetics of PPIX fluorescence revealed a maximum intensity in the tumor tissue within 3 and 4.5 h post-application of 5-ALA. At this time, specific PPIX fluorescence could be localized selectively in the tumor cells. The PDT-induced necrosis (n = 18) was determined to be 94 B 12% (range 60-100%), while the necrosis of the controls ( n = 12) differs significantly (p < 0.01), being less than 10%. Conclusion: These first in vivo results demonstrate the effective potential of 5-ALA-mediated PDT on PCA in an animal model. Copyright (C) 2004 S. Karger AG, Basel.

Background: 5-Aminolevulinic acid (5-ALA)-induced protoporphyrin IX (PPIX) fluorescence improves the differentiation of tumor and normal tissue in the bladder, skin and brain. Objective: The kinetics of 5-ALA-induced protoporphyrin IX (PPIX) fluorescence in organ cultures of normal human bronchial epithelium and cocultures of bronchial epithelium and tumor have been studied. Methods: Cultured biopsies of bronchial epithelium were exposed for 5 or 15 min, or continuously to 5-ALA. PPIX fluorescence was quantified for up to 300 min by spectroscopy. Cocultures of normal bronchial epithelium and a non-small-cell lung cancer cell line (EPLC-32M1) were incubated with 5-ALA. Space-resolved fluorescence microscopy was used to quantify PPIX fluorescence kinetics in the tumor and normal epithelium. Results: In cultures of normal epithelium, PPIX fluorescence kinetics were shown to depend on the duration of exposure to 5-ALA. There was a trend to higher fluorescence intensities with longer exposure times. In cocultures of bronchial epithelium and tumor, increases of fluorescence intensity were significantly greater in the tumor. Best tumor/normal tissue fluorescence ratios were found between 110 and 160 min after exposure to 5-ALA. Conclusion: Data obtained in this coculture system of bronchial epithelium and tumor is valuable to optimize modalities of fluorescence bronchoscopy for the diagnosis of early bronchial carcinoma. Copyright (C) 2002 S. Karger AG, Basel.