Serap Yalcin

Synthesis of Doxorubicin loaded magnetic chitosan nanoparticles for pH responsive targeted drug delivery

Targeted drug delivery is a promising alternative to overcome the limitations of classical chemotherapy. In an ideal targeted drug delivery system carrier nanoparticles would be directed to the tumor tissue and selectively release therapeutic molecules. As a novel approach, chitosan coated magnetic nanoparticles (CS MNPs) maintain a pH dependent drug delivery which provides targeting of drugs to the tumor site under a magnetic field. Among various materials, chitosan has a great importance as a pH sensitive, natural, biodegradable, biocompatible and bioadhesive polymer. The aim of this study was to obtain an effective targeted delivery system for Doxorubicin, using chitosan coated MNPs. Different sized CS MNPs were produced by in situ synthesis method. The anti-cancer agent Doxorubicin was loaded onto CS MNPs which were characterized previously. Doxorubicin loading was confirmed by FTIR. Drug loading and release characteristics, and stability of the nanoparticles were investigated. Our results showed that the CS MNPs have pH responsive release characteristics. The cellular internalization of Doxorubicin loaded CS MNPs were visualized by fluorescent microscopy. Doxorubicin loaded CS MNPs are efficiently taken up by MCF-7 (MCF-7/S) and Doxorubicin resistant MCF-7 (MCF-7/1 μM) breast cancer cells, which increases the efficacy of drug and also maintains overcoming the resistance of Doxorubicin in MCF-7/Dox cells. Consequently, CS MNPs synthesized at various sizes can be effectively used for the pH dependent release of Doxorubicin in cancer cells. Results of this study can provide new insights in the development of pH responsive targeted drug delivery systems to overcome the side effects of conventional chemotherapy.

Idarubicin-loaded folic acid conjugated magnetic nanoparticles as a targetable drug delivery system for breast cancer.

Conventional cancer chemotherapies cannot differentiate between healthy and cancer cells, and lead to severe side effects and systemic toxicity. Another major problem is the drug resistance development before or during the treatment. In the last decades, different kinds of controlled drug delivery systems have been developed to overcome these shortcomings. The studies aim targeted drug delivery to tumor site. Magnetic nanoparticles (MNP) are potentially important in cancer treatment since they can be targeted to tumor site by an externally applied magnetic field. In this study, MNPs were synthesized, covered with biocompatible polyethylene glycol (PEG) and conjugated with folic acid. Then, anti-cancer drug idarubicin was loaded onto the nanoparticles. Shape, size, crystal and chemical structures, and magnetic properties of synthesized nanoparticles were characterized. The characterization of synthesized nanoparticles was performed by dynamic light scattering (DLS), Fourier transform-infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM) analyses. Internalization and accumulation of MNPs in MCF-7 cells were illustrated by light and confocal microscopy. Empty MNPs did not have any toxicity in the concentration ranges of 0-500μg/mL on MCF-7 cells, while drug-loaded nanoparticles led to significant toxicity in a concentration-dependent manner. Besides, idarubicin-loaded MNPs exhibited higher toxicity compared to free idarubicin. The results are promising for improvement in cancer chemotherapy.

Chitosan magnetic nanoparticles for pH responsive Bortezomib release in cancer therapy.

The use of nanotechnology in cancer treatment offers exciting opportunities, including the possibility of destroying tumors with minimal damage to healthy tissue by novel targeted drug delivery systems. pH differences between healthy and tumor microenvironment provide pH responsive release of drugs at tumor site via smart nanoparticles. In this study, chitosan coated superparamagnetic iron oxide nanoparticles (CS MNPs) were in situ synthesized by ionic crosslinking method as nanocarrier systems and loaded with the drug Bortezomib (Velcade(®)). The drug loading capacity, drug release and stability of CS MNPs were analyzed. CS MNPs were visualized inside the cells by fluorescence microscopy. The cytotoxicity of Bortezomib, CS MNPs and Bortezomib loaded CS MNPs were tested by XTT analyses in vitro. Gene expression analyses revealed that pro-apoptotic PUMA and NOXA genes were upregulated while anti-apoptotic BCL-2, SURVIVIN and cIAP-2 genes were downregulated at Bortezomib loaded CS MNP treated cells. Immunocytochemical analyses demonstrated an increase in p53 tumor suppressor protein levels at treated cells, which supports the upregulation of PUMA and NOXA genes, while Survivin protein level did not significantly change. This study points out that the pH responsive magnetic targeting of Bortezomib is more efficacious than free drug treatment. Moreover, targeted delivery of Bortezomib would reduce the frequency of drug administration by lowering the required amount of drug dose.

Loading of Gemcitabine on chitosan magnetic nanoparticles increases the anti-cancer efficacy of the drug.

Targeted delivery of anti-cancer drugs increase the efficacy, while decreasing adverse effects. Among various delivery systems, chitosan coated iron oxide nanoparticles (CsMNPs) gained attention with their biocompatibility, biodegradability, low toxicity and targetability under magnetic field. This study aimed to increase the cellular uptake and efficacy of Gemcitabine. CsMNPs were synthesized by in situ co-precipitation and Gemcitabine was loaded onto the nanoparticles. Nanoparticle characterization was performed by TEM, FTIR, XPS, and zeta potential. Gemcitabine release and stability was analyzed. The cellular uptake was shown. Cytotoxicity of free-Gemcitabine and Gem-CsMNPs were examined on SKBR and MCF-7 breast cancer cells by XTT assay. Gemcitabine loading was optimized as 30µM by spectrophotometric analyses. Drug release was highest (65%) at pH 4.2, while it was 8% at pH 7.2. This is a desired release characteristic since pH of tumor-tissue and endosomes are acidic, while the blood-stream and healthy-tissues are neutral. Peaks reflecting the presence of Gemcitabine were observed in FTIR and XPS. At neutral pH, zeta potential increased after Gemcitabine loading. TEM images displayed, Gem-CsMNPs were 4nm with uniform size-distribution and have spherical shape. The cellular uptake and targetability of CsMNPs was studied on MCF-7 breast cancer cell lines. IC50 value of Gem-CsMNPs was 1.4 fold and 2.6 fold lower than free-Gem on SKBR-3 and MCF-7 cell lines respectively, indicating the increased efficacy of Gemcitabine when loaded onto nanoparticles. Targetability by magnetic field, stability, size distribution, cellular uptake and toxicity characteristics of CsMNPs in this study provides a useful targeted delivery system for Gemcitabine in cancer therapy.

The relationship of the BRAF(V600E) mutation and the established prognostic factors in papillary thyroid carcinomas.

It has been shown that BRAFV600E mutation in papillary thyroid carcinomas (PTC) is associated both with pathogenesis and poor prognosis. In this study, we aimed to investigate the relationship of the BRAFV600E mutation and the established prognostic factors in a cohort of Turkish patients with PTC. Forty-six cases of papillary thyroid carcinoma have been evaluated for the presence of BRAFV600E mutation. BRAFV600E has been examined by restriction fragment length polymorphism. BRAFV600E mutation status has been compared with well-known histopathological and clinical prognostic parameters such as invasion of thyroid capsule, extrathyroidal extension, and the presence of lymph node and/or distant metastasis. We have found that BRAFV600E mutation was present in the majority of our cases (40/46). Considering the stage of the disease, five of the negative cases were in stage 1 while the remaining one was in stage 2. Only one BRAFV600E negative case has shown extrathyroidal extension and lymph node metastasis. All four patients with distant metastasis had BRAFV600E mutation. Statistical analyses revealed that there are no significant relationship between the BRAFV600E mutation and the established prognostic factors. We found a relatively higher BRAFV600E mutation rate in classical type PTC than in other similar studies. We think that the limited number of our cases may either weaken or mask some potentially important relationship between BRAFV600E mutation and the established prognostic factors.

Half generations magnetic PAMAM dendrimers as an effective system for targeted gemcitabine delivery.

Tumor-specific delivery of anticancer drugs by magnetic nanoparticles will maximize the efficacy of the drug and minimize side effects, and reduce systemic toxicity. The magnetic core of these nanoparticles provides an advantage for selective drug targeting as they can be targeted to the tumor site and accumulated in cancer cells by means of an external magnetic field. Magnetic nanoparticles can be coated with Polyamidoamine (PAMAM) dendrimer and loaded with drugs. However, biomedical applications of PAMAM dendrimers are limited due to their toxicity associated with their multiple cationic charges due to terminal NH2 groups. Modifying the positively charged end groups with negatively charged COOH groups, is a satisfactory strategy for obtaining less toxic PAMAM dendrimers. Gemcitabine being an analogue of deoxycytidine, is an effective anticancer drug. However, clinical benefits of Gemcitabine are limited due to its short biological half-life. The aim of this study was to obtain an effective, less toxic targeted delivery system for Gemcitabine. Half generations, between G4.5 and G7.5, of PAMAM dendrimer coated magnetic nanoparticles (DcMNPs) were synthesized and conjugated with Gemcitabine. TEM images showed nanoscale size (12-14nm) of the nanoparticles. The zeta-potential analysis indicated a decreased negativity of surface charge in drug bound dendrimer compared to the empty nanoparticles. Gemcitabine was effectively conjugated successfully onto the surface of half-generations of PAMAM DcMNPs. It was observed Gemcitabine did not effectively bind to Generations G4 and G5. The highest drug loading was obtained for DcMNPs with Generation 5.5. Empty nanoparticles showed no significant cytotoxicity on SKBR-3 and MCF-7 cells. On the other hand, Gemcitabine loaded nanoparticles were 6.0 fold more toxic on SKBR-3 and 3.0 fold more toxic on MCF-7 cells compared to free Gemcitabine. Gemcitabine loaded on Generation 5.5 DcMNPs showed a higher stability than free Gemcitabine. About 94% of the drug was retained over 6 weeks period, at pH 7.2. Due to their targetability under magnetic field, stability, size distribution, cellular uptake and toxicity characteristics the dendrimeric nanoparticles obtained in this study can be useful a delivery system for Gemcitabine in cancer therapy.

Telomere 1 (POT1) gene expression and its association with telomerase activity in colorectal tumor samples with different pathological features

The ends of chromosoms, telomeres are bound with a number of proteins which protect and stabilize telomeres against degredation, end to end fusion and aberrant recombinations. Telomeric DNA is bound of two groups of proteins, which are double-stranded telomeric DNA bindings proteins, and single stranded telomeric binding proteins. Among telomere binding proteins, protections of telomere 1 protein is a single stranded telomere binding proteins and suggested to be a significant player for telomere elongation and has an association with an enzyme called as telomerase which is an intrinsic reverse transcriptase. Telomerase synthesizes hexameric telomeric repeats onto the chromosomes thereby compansating telomere loss in immortal cells, such as tumor cells, whereas telomeres are shorthened with each division in normal cells. PCR-based TRAP (telomeric repeat amplification protocol) assay is a very sensitive assay for the detection of enzymatic activity of telomerase even if a few numbers of cancerous cells are available. The association between telomerase activity and hPOT1 expression in colorectal cancer is still unclear. Protein extraction was performed from specimens of matched normal and colorectal cancer specimens. Protein concentrations were determined by Bradford assay. Optimized protein concentrations were used for TRAP Assay. TRAP products were seperated by vertical gel electrophoresis on 12.5% polyacrylamide gels and visualized by silver staining. Gene expression of hPOT1 was determined by qPCR analysis. The results demonstrated that all tumor tissues were telomerase positive whereas all corresponding normal tissue was telomerase negative. Among clinicopathological findings, telomerase activity was found to be associated with stage, histology, localization, distant metastasis and lymph node metastasis of tumor in the current study. Although all of the clinicopathological findings differed in the expression of hPOT1 compared to normal tissues, they did not differ from each other significantly, except side of tumor and lymph node metastasis. Telomerase activity and hPOT1 gene expression may serve as a promising tumor marker for colorectal cancer and there is a close association between the enzymatic activty of telomerase and the expression of human protection of telomere 1 gene.

Polyhydroxybutyrate-Coated Magnetic Nanoparticles for Doxorubicin Delivery: Cytotoxic Effect Against Doxorubicin-Resistant Breast Cancer Cell Line

In this study, polyhydroxybutyrate (PHB)-coated magnetic nanoparticles (MNPs) were prepared by coprecipitation of iron salts (Fe2+ and Fe3+) by ammonium hydroxide. Characterizations of PHB-coated MNPs were performed by Fourier transform infrared spectroscopy, x-ray diffraction, dynamic light scattering, thermal gravimetric analysis, vibrating sample magnetometry, and transmission electron microscopy analyses. Doxorubicin was loaded onto PHB-MNPs, and the release efficiencies at different pHs were studied under in vitro conditions. The most efficient drug loading concentration was found about 87% at room temperature in phosphate-buffered saline (pH 7.2). The drug-loaded MNPs were stable up to 2 months in neutral pH for mimicking physiological conditions. The drug release studies were performed with acetate buffer (pH 4.5) that mimics endosomal pH. Doxorubicin (60%) released from PHB-MNPs within 65 hours. Doxorubicin-loaded PHB-MNPs were about 2.5-fold more cytotoxic as compared with free drug on resistant Michigan Cancer Foundation-7 (human breast adenocarcinoma, MCF-7) cell line (1 &mgr;M doxorubicin) in vitro. Therefore, doxorubicin-loaded PHB-MNPs lead to overcome the drug resistance.

Effects of the interleukin-6 (IL-6) polymorphism on toxic metal and trace element levels in placental tissues

The placenta is a crucial organ of fetal origin that functions in providing nutrients to the fetus from the mother. During pregnancy, the need for essential micronutrients, such as Fe and Zn, increases due to the requirements of the growing fetus. Maternal Fe deficiency induces an increase in Cu levels and can also affect cytokine levels in the placenta. On the other hand, Cu deficiency, although not as common, can also have destructive effects on the fetus. Interleukin-6 (IL-6) is a pleiotropic cytokine with a wide range of biological activities, including such as immune responses, acute-phase reactions, and inflammation. The placenta produces a significant amount of IL-6 during pregnancy. The effects of the IL-6 -174 G/C single nucleotide polymorphism (SNP) on IL-6 gene transcription and on plasma cytokine levels were assessed in the present study. We investigated the association between the IL-6 -174 G/C polymorphism and trace element/toxic metal levels in placental tissues. For the purposes of this study, 95 healthy volunteers were evaluated. Presence of the IL-6 polymorphism was determined using the standard polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) technique, and metal levels were analyzed by atomic absorption spectrometry (AAS). Based on our data, there were no significant associations between the IL-6 -174 G/C polymorphism and Pb, Cd, Fe, or Zn levels in the placental tissues (p>0.05), but a statistically significant association was detected between the polymorphism and Cu levels (p=0.016). We determined that the mean Cu levels in the placental tissues from individuals with GG, GC and CC genotypes were 5.62±1.98, 6.22±3.22 and 8.00±1.32 ppm, respectively, whereas the overall mean Cu level from the placental tissues was 5.98±2.51 ppm.

Synthesis and Characterization of Polyhydroxybutyrate Coated Magnetic Nanoparticles: Toxicity Analyses on Different Cell Lines

In this study, polyhydroxybutyrate (PHB) coated magnetic nanoparticles were prepared which are targetable to tumor cells in the presence of a magnetic field. The structural properties, functional groups, size distribution, and magnetic properties of the synthesized PHB coated magnetic nanoparticles were characterized by X-ray diffraction, Fourier transform infrared spectrometer, transmission electron microscopy, dynamic light scattering, vibrating sample magnetometry, and thermogravimetric analysis. PHB coated nanoparticles are efficiently internalized by the cancer cells in culture, without cytotoxicity. The results demonstrated that PHB coated iron oxide nanoparticles are suitable for targeted delivery of drugs such as chemotherapeutics, siRNA, miRNA, or antibodies.