Browsing by Subject "Conjugated polymer nanoparticles"
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Item Open Access Conjugated polymer nanoparticles for biomedical applications including bioimaging and drug delivery(Bilkent University, 2013) Ünal, ÖzlemItem Open Access Multifunctional conjugated polymer nanoparticles as an anticancer drug carrier and a fluorescent probe for cell imaging(Bilkent University, 2012) Gezici, ÖzlemThe main motivation of this study is to develop multifunctional nanoparticles which can perform simultaneously the drug delivery and cell imaging tasks. To this end, firstly nanoparticles (Nps) with an average diameter of about 25 nm and based on a green emitting, hydrophobic conjugated polymer, poly[(9,9-bis{propenyl}fluorenyl-2,7- diyl))-co-(1,4-benzo-{2,1,3}-thiodiazole)] (PPFBT) and Nps with an average diameter of about 150 nm and based on a red emitting, hydrophobic conjugated polymer, poly[(9,9-bis{3-azido-propyl}fluorenyl-2,7-divinylene)-co-(1,4-benzo- {2,1,3}-thiodiazole)] (PAPFVBT) were prepared, characterized and their convenience as a fluorescent probe for cell imaging was evaluated via in vitro cell assays. Then, drug loaded nanocapsules in which PPFBT or PAPFVBT acts both as a fluorescent reporter and the main matrix of the nanocapsules accommodating an anticancer drug, camptothecin (CPT), were synthesized through a facile, single step reprecipitation method. CPT is a hydrophobic, water-insoluble drug but the encapsulation improved its water-solubility. The CPT loading efficiency in the nanoparticles has been determined to be 100% when a drug to polymer ratio of 1:25 (w/w) was used. Cell viability of Human hepatocellular carcinoma cell line (Huh7) was investigated in the absence and presence of CPT using Sulforhodamine B (SRB) assay. SRB assay results supported further by the fluorescence microscope cell images clearly confirmed that blank and CPT-loaded PPFBT Nps have been taken up by the cells very efficiently and these nanoparticles were accumulated in the cytoplasm. Time and dose dependent SRB assay results indicate that the blank PPFBT Nps are not toxic to the Huh7 cells up to 25 µM. However, even a very low dose of CPT was found to be sufficient to induce the apoptosis of the cells when it was delivered through nanoparticles. Thus, at the end of 48 h, the half maximal inhibitory concentration (IC50) of free CPT and CPT-loaded PPFBT Nps were calculated to be 0.9 µM and 0.1 µM respectively, corresponding to that CPT-loaded PPFBT Nps are 9 times more effective than free CPT. However, at the end of 72 h, the IC50 of free CPT and CPT-loaded PPFBT Nps decreased to 0.1 µM and 0.008 µM, respectively. In this case, CPT-loaded PPFBT Nps are 12.5 times more effective than free CPT in inducing the apoptosis of Huh7 cells. Although the free drug (CPT) reaches IC50 of 0.1 µM after 72 h, it is possible to achieve this value with CPT-loaded Nps at the end of 48 h. On the other hand, dose dependent SRB assay results indicate that the blank PAPFVBT Nps are not toxic to the Huh7 cells up to 16 µM. At the end of 72 h, IC50 of free CPT and CPTloaded PAPFVBT Nps were calculated to be 0.03 µM and 0.1 µM respectively, corresponding to that CPT-loaded PAPFVBT Nps are 3.3 times less effective than free CPT. Having bigger size (~150 nm) of PAPFVBT Nps is the main reason of not being effective as PPFBT Nps (~25 nm).Item Open Access Synthesis of vertically aligned CNT arrays using liquid based precursors and their functionalization by conjugated polymers(Bilkent University, 2011) Baykal, BerilIn the first part of this work, a new solution based catalyst precursor application method is developed for growing high quality vertically aligned carbon nanotubes arrays (VANTA) through alcohol catalyzed chemical vapor deposition (AC-CVD). For this purpose, various solution based precursor preparation routes are investigated starting from γ-Al2O3 / Fe(NO3)3.9H2O mixtures and ranging to catalyst precursors prepared by mixing aqueous aluminium and iron nitrate solutions. Application of these solutions separately layer by layer on Si(100) substrate resulted in high quality dense vertically aligned CNT arrays. By varying the metal nitrate concentration in the precursor solutions, the dependence of the density and quality of CNT arrays on the catalyst layers are investigated. The CNT array quality and density are characterized by dynamic contact angle measurements using water droplets. Higher density CNT arrays resulted in higher contact angle measurements. The chemical and structural characterizations of CNTs are also done by using TEM, SEM, EDX and Raman spectroscopy. Some of the samples are found to be super hydrophobic even after 30 minutes of exposure to water. In this effort, application of subsequent layers of aqueous aluminium nitrate and iron nitrate on oxidized Si(100) surfaces are found to be most efficient catalyst layer preparation technique resulting in the highest density of CNT arrays. In the second part of this work, functionalization of the synthesized CNT arrays is done for the purpose of achieving good dispersibility of CNTs in aqueous media. To this end, a new approach is used to ensure stability of the CNT-water solution. In this approach, conjugated polymer nanoparticles (CPNs) are successfully used to disperse CNTs through non-covalent functionalization of the sidewalls of CNTs. The attachment of CPNs to CNTs is characterized by SEM, EDX and TEM. Moreover, interactions are investigated by UV-VIS, and Raman spectroscopy. The interaction mechanism of polymer chains with side-walls of CNTs are further scrutinized by follow-up experiments where two different conjugated polymers with brominated-alkyl and bare alkyl groups in THF media are mixed with SWCNTs (commercial), MWCNTs and an-MWCNTs (synthesized in the first part of this study). The results of this investigation suggested a limited number of docking configurations of the polymers with the CNT side-walls. Also, it is found that the defect density of the CNT side-walls play an important role in the nature of the interaction. Overall, in this work a cheap and effective route for application of catalyst is developed for the synthesis of dense, super-hydrophobic CNT arrays using ACCVD. Then, well-dispersion of these CNTs is successfully achieved using CPNs. Finally, the nature of the interaction between conjugate polymers and CNTs sidewalls are investigated using experimental techniques.Item Open Access White-emitting conjugated polymer nanoparticles with cross-linked shell for mechanical stability and controllable photometric properties in color-conversion LED applications(2011) Park, Eun-Ju; Erdem, T.; Ibrahimova, V.; Nizamoglu, S.; Demir, Hilmi Volkan; Tuncel, D.We report on the synthesis and characterization of water-dispersible, mechanically stable conjugated polymer nanoparticles (CPNs) in shelled architecture with tunable emission and controllable photometric properties via cross-linking. Using a reprecipitation method, whiteemitting polymer nanoparticles are prepared in different sizes by varying the concentration of polymer; the emission kinetics are tuned by controlling the shell formation. For this purpose, polyfluorene derivatives containing azide groups are selected that can be decomposed under UV light to generate very reactive species, which opportunely facilitate the inter- and intra-cross-linking of polymer chains to form shells. Nanoparticles before and after UV treatment are characterized by various techniques. Their size and morphologies are determined by using dynamic light scattering (DLS) measurements and imaging techniques including scanning electron microscopy (SEM) and atomic force microscopy (AFM). For optical characterization, UV vis and steady-state and timeresolved fluorescent spectroscopies are performed. Solid-state behaviors of these CPNs are also investigated by forming films through drop-casting. Moreover, the photometric calculations are also performed for films and dispersions to determine the color quality. A device has been constructed to show proof-of-principle white light generation from these nanoparticles. Additionally, mechanical stability studies are performed and demonstrated that these nanoparticles are indeed mechanically stable by removing the solvent after cross-linking using a freeze-dryer and redispersing in water and THF. Optical and imaging data confirm that the redispersed particles preserve their shapes and sizes after cross-linking.