Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Author: search.filters.author.Top, AybenSubject: search.filters.subject.Drug delivery systems

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  • Master Thesis
    Development of Peg-Peptide Conjugate Based Curcumin Delivery Systems
    (01. Izmir Institute of Technology, 2022) Aydoğan, Gamze; Top, Ayben
    In this study, a drug delivery system based on Pluronic F127 and a peptide conjugate was proposed. The F127-peptide conjugate was prepared by the reaction between succinimidyl functionalized F127 (SC-F127) and peptide. SC-F127 was synthesized using disuccinimidyl carbonate and DMAP. Folic acid-functionalized F127 (FA-F127) was also prepared to obtain active targeting copolymers. Four peptides containing pH-responsive multiple histidines and endosome disruptive GFWFG domain were synthesized using the Fmoc procedure. H-Gly-2-ClTrt resin and Rink amide MBHA resin were used to synthesize side-chain-protected and deprotected peptides, respectively. 2-chlorotrityl resin failed in synthesizing the high-purity peptides with adjacent histidines in their sequences. Peptide-4 having a sequence of GGH6GFWFG, was prepared with acceptable purity using rink amide MBHA resin and was conjugated to SC-F127. Curcumin was loaded to F127 and F127-peptide using the thin film method with DCM solvent. Almost all curcumin was encapsulated into F127 micelles. However, the entrapment efficiency % of the F127-peptide micelles was ~86% due to the lower solubility of F127-peptide conjugate in DCM. Dynamic light scattering experiments were used to determine the stability and size distribution of the micelles. Number-based size distributions of both micelles indicated that a single peak between 10 and 30 nm was independent of pH. The peak position did not change upon incubating the micelles at 37oC up to a few days. Initially, intensity-based results of both samples indicate bidisperse populations at pH 5.0 and 7.4. Curcumin-loaded F127 micelles aggregated in the three days, as revealed by the formation of the third peak above 1000 nm independent of pH. Curcumin-loaded F127-peptide micelles, on the other hand, retain their stability for up to five days at neutral pH. For this sample, the third peak was observed only at pH 5.0 on days 2 and 5.
  • Master Thesis
    Development of Endosome Disruptive Peptide and Peg Conjugate Based Doxorubicin Delivery System
    (Izmir Institute of Technology, 2019) Özkıyıcı, Selin; Top, Ayben
    In this study, it was aimed to develop a drug carrier system including a TAT-derived cell penetrating peptide in order to provide fast transport of anticancer drugs from endosomal compartments to nucleus. The drug delivery system, denoted as mPEGpeptide- oxime-DOX, was based on polyethylene glycol, endosome disruptive peptide (G2RQR3QR3G2S), and doxorubicin (DOX) conjugate. Control drug delivery system, lack of the peptide (mPEG-oxime-DOX) was also synthesized to assess the effect of the peptide on the physiochemical and drug release properties of the drug carrier. As the first synthesis step, mPEG-OH was converted to mPEG-aldehyde form using DMSO-acetic anhydride oxidation reaction and aldehyde functionalization was determined by using FTIR and NMR spectroscopy. The peptide and mPEG-peptide were synthesized using solid phase synthesis protocol, and their purities were confirmed using HPLC and MALDI-TOF mass spectroscopy analyses. Prior to DOX conjugation, hydroxyl group of serine residue in the mPEG-peptide system was oxidized to aldehyde. The anticancer drug was attached to the carrier molecules via amine-aldehyde reaction forming an acid cleavable oxime bond. Drug release, size distribution, and stability of the PEG-peptideoxime- DOX system were evaluated and compared with those results of the control drug delivery system. For mPEG-oxime-DOX, a pH programmed DOX release with the respective % DOX release values of ~68 % and ~28 % at pH 5.0 and pH 7.4 was observed. For mPEG-peptide-oxime-DOX, on the other hand, quite low DOX release (~10-15 %) was obtained for both pH values suggesting possible interaction between DOX and the peptide. Mean size value of the mPEG-oxime-DOX was measured as ~24 nm. However, mPEG-peptide-oxime-DOX, had quite lower hydrodynamic diameter values (~3nm and ~6 nm at pH 5.0 and pH 7.4, respectively) possibly due to repulsions between the arginines in the peptide domain. Observation of the morphology and evaluation of the cytotoxicity of these drug delivery systems are underway.
  • Master Thesis
    Peg-Peptide Drug Carrier Systems With Enzymatic Degradation Units
    (Izmir Institute of Technology, 2016) Yüksel, Nesligül; Top, Ayben
    In this study, it was aimed to develop drug delivery systems with high drug release rate, capable of overcoming multidrug resistance of cancer cells. The first generation drug delivery system (DDS) denoted as mPEG-AT3-DOX was prepared by methoxy polyethylene glycol (mPEG) and peptide conjugation, and the model anticancer drug, DOX, was attached to the mPEG-peptide carrier system using stable amide linkage. mPEG was used to increase blood circulation time of the DDS. Designed peptide (AT3 = CG3H6R2ALALG3E) controls release of the drug via RRALAL sequence, which is a substrate for a lysosomal enzyme, cathepsin B, overexpressed in most of the tumor cells. pH responsive histidines and reactive amino acids (glutamic acid and cysteine) for drug and mPEG conjugations were also added to the peptide sequence. The peptide synthesized by using Fmoc chemistry was conjugated to mPEG-maleimide via Michael addition reaction. DOX was attached to the carboxylic acid group present in the carrier system (mPEG-AT3) via amide linkage. Mass spectroscopy and HPLC were used to assess the purity of the AT3 and mPEG-AT3. At pH 7.4, mPEG-AT3-DOX exhibited bimodal size (hydrodynamic diameter) distribution at about 15 and 30 nm independent of pH. % DOX release from mPEG-AT3-DOX was observed to be below 10 % at neutral pH and pH 5.0 in the absence of cathepsin B, and increased to 17 ± 2 % in the presence of cathepsin B. Complete degradation of AT3 peptide within three hours in the presence of cathepsin B suggests lower than expected DOX release is due to aggregation tendency of the DDS. Cytotoxicity of the conjugates was evaluated using the lung cancer (A549) and prostate cancer (PC3) cell lines. At the end of 24 hours the absolute IC50 values of free DOX and mPEG-AT3-DOX were obtained as 1.37 ± 0.05 and 1.33 ± 0.11 for the A549 cell line, 1.51 + 0.07 and 1.63 + 0.80 μg equivalent DOX / ml for the PC3 cell line, respectively. Considering, these results, the second generation DDS will be designed to have more pronounced pH sensitive property by increasing the number of histidines in the peptide domain.
  • Master Thesis
    Development of Peg and Peg-Peptide Based Drug Delivery Systems
    (Izmir Institute of Technology, 2016) Balcı, Beste; Top, Ayben
    In this study, two types of drug delivery systems (DDS) were prepared; mPEG (methoxy polyethylene glycol)-HYD (hydrazide)-DOX and mPEG-peptide-(HYD)-DOX. In the design of the conjugates, mPEG was used to increase the blood circulation time. HYD provided an acid cleavable bond between the carrier molecule and DOX, whereas peptide containing histidines imparted pH responsiveness of the molecule. Doxorubicin (DOX) was selected as a model anti-cancer drug. DDS were synthesized using two steps; hydrazide functionalization of carboxylic acid of the carrier molecule followed by DOX conjugation. Hydrazide form of the carrier molecules denoted as HYD1 and HYD2 were obtained using adipic acid dihydrazide (AADH) and carbohydrazide (CH), respectively. To increase DOX conjugation, trifluoroacetic acid (TFA) and DOX amounts were changed and the reactions were carried out at the conditions giving the highest DOX conjugation (mPEG-HYD:DOX:TFA= 2.5mg:2mg:20μL per 1 mL of DMSO). The peptide (AT1=CGGGHHHHHHGGGE) was synthesized using solid phase peptide synthesis (SPPS) and PEGylated using mPEG-maleimide to obtain mPEG-AT1 conjugate. The purity of AT1 and mPEG-AT1 were confirmed using mass spectroscopy and high performance liquid chromatography (HPLC). DOX conjugation percentages were obtained as 62  7, 60  3 and 35 + 3 for mPEG-HYD1-DOX, mPEG-HYD2-DOX and mPEG-AT1-HYD1-DOX, respectively. Drug release studies indicated modest pH responsiveness of the carrier molecules obtained using AADH. On the other hand, mPEG-HYD2-DOX released  13% of drug at the end of the 72h independent of pH. For mPEG-AT1-DOX, drug release percentage values were obtained as  15% and  30% at pH 7.4 and 5.0 respectively. Cytotoxicity of the conjugates of DDS was determined using lung cancer (A-549) cell lines. DOX equivalent IC50 values were determined as 20, 40 and 5 for mPEG-HYD1-DOX, mPEG-HYD2-DOX and mPEG-AT1-DOX respectively.