Thermosensitive biodegradable mPEG-PLLA block copolymers : syntheses, characterizations and applications in drug delivery systems; synthesis and properties of novel electrochromic polythienylpyrrole

Mert, Olcay
Syntheses of biodegradable PLLA homopolymers and PLLA-mPEG diblock copolymers for the formation of thermo-sensitive gels were performed. The sol-gel transition temperature of the matrix was adjusted by altering the length of each PEG and LA component. PLLA-mPEG biocompatible copolymers, having appropriate length of each block component, showed sols at around 42-45 oC, suitable for the injection, then a gel with subsequent rapid cooling to body temperature. Topotecan and camptothecin were selected as anti-cancer drugs. Both drugs can easily hydrolyze at physiological conditions (pH=7.4). This causes the loss of its activity, and it turns into inactive toxic carboxylate form from active lactone state. To keep those anti cancer drugs in the lactone form, they were efficiently loaded into PLLA-mPEG gels in different loading ratios. Their stability in gel was fully examined with HPLC and fluorescence spectroscopy. It was found that both drugs were highly stable and in active form in the prepared gels (>95 %). Then, both release profile of drugs at different loading ratios showed prolonged release over weeks. Mechanistic studies on the stabilization of CPT anti cancer drug with PLLA-mPEG gels were carried out using ATR-FTIR, confocal and optic microscopes. The cytotoxic efficacy of TPT in the PLLA-mPEG platform (PLLA-mPEG-TPT) was evaluated on LLC-1 and 4T1 cancer cell lines by MTT assay. In vivo, the administration of PLLA-mPEG-TPT to the mice bearing breast tumours established with 4T1 cells resulted in a significant reduction in tumour size and better survival percentages. Additionally, stabilization of CPT and TPT with gels may find another application on solid tumors in brain via local injection. A novel conducting polymer was successfully synthesized via electropolymerization of 1-(1H-pyrrol-1-yl)-2,5-di(thiophen-2-yl)-1H-pyrrole. The electrochemical and electro-optical properties of the corresponding polymer, which was the first example of polymer containing 1,1’-bipyrrole units, were elaborated using electroanalytical and spectroscopic techniques. Cyclic voltammograms and electrooptical studies showed that the polymer has a stable and well-defined reversible redox process as well as electrochromic behavior. The processable polymer film also possessed a yellowish orange light emitter property.


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Bat, Erhan; Feijen, J. (2008-12-18)
Triblock copolymers of trimethylene carbonate (TMC) and polyethylene glycol (PEG) were synthesized. Their gelation behaviour in water and the properties of the gels were investigated by particle size measurements, the vial tilting method, and dynamic rheology. As the temperature was decreased, the average particle size increased and sol-to-gel transition was observed. The storage modulus of these thermoreversible gels ranged from 220 Pa to 4700 Pa depending on the composition and concentration of the copoly...
Production and characterization of boron containing flame retardant polyamide-6 and polypropylene composites and fibers
Doğan, Mehmet; Bayramlı, Erdal; Department of Polymer Science and Technology (2011)
The main objective of this study was to produce flame retardant polyamide-6 (PA-6) and polypropylene (PP) composites and fibers containing boron compounds. The synergistic effect on flame retardancy of boron compounds (boron silicon containing oligomer (BSi), zinc borate (ZnB), boron phosphate (BPO4), metal oxide doped BPO4 and lanthanum borate (LaB)) with conventional flame retardants were investigated. The synergistic effect of nano-clay with commercial flame retardants was also investigated in order to r...
Thermoluminescence in gallium sesquisulfide single crystals: usual and unusual heating rate dependencies
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Thermoluminescence (TL) experiments were conducted for Ga2S3 crystals to obtain information about trapping parameters. TL measurements were performed from 10 to 300 K with varying heating rates in the range of 0.2-0.8 K/s. Two TL glow peaks centered at 44K (peak A) and 91 K (peak B) were observed at heating rate of beta=0.5 K/s. For peak A, TL intensity decreased whereas that for peak B increased with elevating the heating rates that means anomalous heating rate occurred for peak B. TL glow curves were anal...
Solution Processable Benzotriazole, Benzimidazole and Biphenyl Containing Conjugated Copolymers for Optoelectronic Applications
Kaya Deniz, Tuğba; Çırpan, Ali; Department of Polymer Science and Technology (2012)
The synthesis and optoelectronic properties of biphenyl based conjugated copolymers with varying acceptor units in the polymer backbone were investigated. The well known Donor-Acceptor Theory was used to establish the synthetic pathway for the structural modifications. Solubility issues regarding biphenyl polymer was solved by copolymerizing with soluble units. For this purpose; poly 4-(biphenyl-4-yl)- 4’-tert butylspiro[benzo[d]imidazole-2,1’-cyclohexane] (P1), poly 4-(biphenyl-4-yl)- 2- dodecyl-2H-benzo[d...
BALCI, S; Doğu, Timur; YUCEL, H (American Chemical Society (ACS), 1993-11-01)
Pyrolysis kinetics of almond and hazelnut shells and beech wood were carried out using a thermogravimetric technique. Experiments were repeated for different final pyrolysis temperatures ranging from 300 to 850-degrees-C. Approximately 90% of the pyrolysis reactions were completed up to 450-degrees-C. The initial values of the activation energy of pyrolysis reaction were found to be around 22 kcal/mol for shells of almond and hazelnut. On the other hand, initial activation energy of beech wood pyrolysis was...
Citation Formats
O. Mert, “ Thermosensitive biodegradable mPEG-PLLA block copolymers : syntheses, characterizations and applications in drug delivery systems; synthesis and properties of novel electrochromic polythienylpyrrole,” Ph.D. - Doctoral Program, Middle East Technical University, 2011.