Herein we report on the fabrication and the properties of two highly efficient blue light emitting multilayer polymer light emitting diodes (PLEDs). The first device structure combines a thermally stabilized polymer with a material processed from an orthogonal solvent, allowing for the fabrication of a triple layer structure from solution. The well known poly(9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine) (TFB), which can be stabilized in a bake-out procedure, was used as a hole transporting layer. A novel pyrene – triphenylamine (PPyrTPA) copolymer was used as emissive layer. The stack was finalized by a poly(fluorene) - derivative with polar side-chains, therefore being soluble in a polar solvent which allows for the deposition onto PPyrTPA without redissolving. The resulting PLED showed bright-blue electroluminescence (CIE1931 coordinates x=0.163; y=0.216) with a high efficiency of 1.42 cd/A and a peak luminescence of 16500 cd/m². The second presented device configuration comprises a thermally stabilized indenofluorene – triphenylamine copolymer acting as hole transporter, and an emissive copolymer with building blocks specifically designed for blue light emission, effective charge carrier injection and transport as well as for exciton generation. This multilayer PLED led to deep-blue emission (CIE1931 x=0.144; y=0.129) with a remarkably high device efficiency of 9.7 cd/A. Additionally, atomic force microscopy was carried out to investigate the film morphology of the components of the stack and x-ray photoemission spectroscopy was performed to ensure a full coverage of the materials on top of each other. Ultraviolet photoemission spectroscopy confirmed the desired type-II band level offsets on the individual interfaces.
The effectiveness of photodynamic therapy (PDT) as an adjuvant treatment for diverse malignant tumors has been investigated in numerous studies. The therapeutic success and extent of side effects of PDT is mainly determined by the applied photosensitizer (PS) and laser energy. Adjuvant intraoperative photodynamic therapy (AIOPDT) using the PS mTHPC (meso-Tetrahydroxyphenylchlorin) causes selective tumor cell death when combined with laser irradiation of a PS specific wavelength (652 nm). Our study proved AIOPDT as an efficient modality to significantly increase postoperative recurrence-free survival after R1/R2 resection of a subcutaneously implanted soft tissue sarcoma in mice. We used mTHPC in a dose of (0,3 mg/kg BW) and a laser light energy of 5 Joule (irradiation time: 50 seconds). First results showed an increase of postoperative recurrence-free survival (Median: 103 days) in 5 animals treated with AIOPDT compared to a control group of 7 animals (Median: 20 days). The tissue specific accumulation of mTHPC was determined by point spectrofluorometry and showed a 2.28 higher PS-accumulation in the tumor center, tumor bed (1.5) and overlying skin (3.8) compared to muscle tissue (1.0) as reference parameter. Our first experimental data recommend AIOPDT to be an efficient adjuvant method to prolonge recurrence-free survival after tumor resection.
A clinical problem in the treatment of colorectal cancer is the high rate of local tumor recurrence. Adjuvant therapy methods are necessary to receive a better clinical outcome in minimizing local tumor relapse. Adjuvant intraoperative photodynamic therapy (AIOPDT) seems to be a promising alternative therapy in the treatment of malignant colorectal diseases. IN experimental settings the success of AIOPDT depends on the accumulation of the photosensitizer (PS) in tumor tissue and may be jeopardized by high mortality rates, due to inadequate energy doses. Our study evaluated mortality rates of nude mice after AIOPDT with ALA, Photofrin II and mTHPC using the following various light doses: ALA/Photofrin II: 100J, 50J, 25J; mTHPC: 30J, 15J, 5J generated by an Argon-Dye-laser system. There was a close correlation between laser energy applied for AIOPDT and postoperative mortality rate. Initial high mortality rates were lowered by stepwise reduction of the energy dose. Mortality rates reached a maximum 24 hours after AIOPDT in all groups.
The effectiveness of PDT as an adjuvant alternative therapy method for diverse malignant tumors has been investigated in numerous studies. The therapeutic benefit and extent of side effects is mainly determined by the applied photoactive substance. The second generation photosensitizer (PS) mTHPC is capable of causing selective tumor cell death in colon carcinoma when combined with laser irradiation of a PS specific wavelength. Our study revealed PDT with mTHPC as an efficient adjuvant intraoperative modality after R1/R2 resection of a subcutaneously implanted colon tumor. There was a significant increase of postoperative recurrence-free survival time using PDT compared to a control group in a colon cancer model in nude mice. The accumulation of the PS determined by point spectrometry showed a high tumor-selectivity in the tumor, tumor bed, and overlying skin compared to muscle tissue as reference parameter.
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