Kurtulus Gokduman

Background: Due to the serious side effects and the resistant phenotype acquired by tumors, cisplatin has limited clinical efficacy. The current study aims to investigate the potential of disulfide-bridged phthalocyanines to make breast cancer cells (MCF-7) more sensitive to cisplatin. For this purpose, a novel disulfide-bridged dimeric phthalocyanine complex with a therapeutically active wavelength absorbance value that is activatable in cancer cells was synthesized and encapsulated in liposome nanoparticles. Methods: The synthesized phthalocyanine was characterized using FTIR, UV–visible, and MALDI-TOF-MS techniques; liposome nanoparticles containing the synthesized phthalocyanine were characterized using a particle size analyzer and were tested on MCF-7 breast cancer cell lines using MTT and flow cytometric assays. Results: The results have illustrated that GSH cleavages disulfide bonds of the synthesized disulfide-bridged dimeric phthalocyanine complex with quite favorable characteristics for photodynamic therapy, such as a therapeutically active wavelength absorbance value (685 nm), and disulfide-bridged phthalocyanine (ASG20)-containing liposome nanoparticles have quite favorable characteristics (average size of 167.6 nm and polydispersity index of 0.108) for biomedical applications. As evidenced by MTT and flow cytometric assays, by causing extra decreases in the viability of breast cancer cells (p < 0.01), pre-treatment of the breast cancer cells with photodynamic therapy using the activatable liposome nanoparticles significantly (p < 0.01) enhanced the anticancer activity of cisplatin in high and low doses. Conclusions: In conclusion, the activatable liposome nanoparticles containing disulfide-bridged dimeric phthalocyanine complexes can enable much more effective cisplatin-based therapies for breast cancer by overcoming the handicaps of cisplatin, drug resistance (by decreasing intracellular GSH levels), and serious side effects (by enabling the usage of lower doses of cisplatin in chemotherapy).

Aim: To investigate potential of magnetite iron oxide nanoparticles (MION) to sensitize cisplatin-resistant ovarian cancer cells to cisplatin, which to the best of found knowledge has not been repo...

Aim: To develop a practical microfluidic 3D hepatocyte chip for hepatotoxicity testing of nanoparticles using proof of concept studies providing first results of the potential hepatotoxicity of sup...

Aim: As a first study in literature, to investigate concentration-dependent (0–400 μg/ml) and exposure-dependent (single dosing vs cumulative dosing) effects of superparamagnetic iron oxide nanoparticles (d = 10 nm) on primary rat hepatocytes in a time-dependent manner. Materials & methods: Sandwich-cultured hepatocyte model was used to evaluate viability, hepatocyte specific functions and reactive oxygen species level. Results: In terms of all parameters, generally statistically more significant effects were observed in a concentration- and time-dependent manner. In terms of hepatocyte-specific functions, cumulative dosing caused significantly (p < 0.05) more deleterious effects at 48th hour. Conclusion: A combination of various biomarkers should be employed for the evaluation of the effect of superparamagnetic iron oxide nanoparticles on liver, and each biomarker should be analyzed in a time- and exposure-dependent manner.

Topoisomerase I (Topo I) is a nuclear enzyme engaged in adjustment of DNA topological structure during cell cycle by cleaving and reannealing one of the two strands of the DNA double helix. Inhibition of this enzyme results in DNA strand breaks, ultimately leads to apoptosis and cell death; additionally it is in raised level in solid tumors contrasted with healthy tissues. Consequently, Topo I has a great potential as a target for the treatment of tumors. Although significant anti-tumor activity of first Topo I inhibitor, camptothecin (CPT), was observed on colon, lung, ovarian, breast, liver, pancreas and stomach cancers, CPT and its clinical derivatives (topotecan and irinotecan) have several restrictions. In addition to their low water solubility and cell resistance to CPTs, lactone ring opening causes a reduction in cytotoxic activity and severe side effects in physiological conditions (pH: 7.4, 37°C). Although numerous efficient nano drug delivery systems were developed for CPT and its derivatives to compensate the handicaps of these compounds, none of them has been approved so far. On the other hand, organic non-CPT compounds have been searched; indolocarbazoles, indenoisoquinolines and dibenzonaphthyridines have been applied to clinical development. Especially, indenoisoquinolines and dibenzonaphthyridines have favorable characteristics compared to CPTs: They are chemically stable; they have the ability to overcome cell resistance; they stabilize enzyme-DNA cleavage complexes more persistently. In addition to the approaches based on organic compounds, recently some metal complexes (e.g., platinum, gold, copper, cobalt, zinc, vanadium, ruthenium) have also been reported as inhibitors of Topo I. This review will discuss the whole aspects of strategies targeting Topo I in cancer chemotherapy from past to the recent progresses.

Although Camptothecin (CPT) has significant antitumor activity to lung, ovarian, breast, pancreas, and stomach cancers; lactone ring opening causes a reduction in cytotoxic activity and severe side effects in physiological conditions (pH: 7.4, 37°C) due to decreased cell membrane binding, membrane diffusibility, and intrinsic potency against the topoisomerase target. Taken into consideration the targeted delivery advantage of biocompatible magnetic particles, in order to contribute to the removal of the handicap (lactone ring opening), the current study investigated stability, release, and in vitro bioactivity of CPT in oleic acid (OA)-pluronic F127 (PL) coated iron oxide micro and nanoparticles. CPT encapsulated magnetite micro (~10 μm) and nano (~30 nm) formulations were synthesized without changing their magnetic properties. Analysis of encapsulated CPT illustrated that over 99% of the lactone form was protected in the magnetic particle formulations and release of CPT from the magnetic micro and nanoparticles lasted for 9 and 4 days respectively. In addition, in a representative in vitro cytotoxicity study, CPT encapsulated OA-PL stabilized magnetite microparticles were approximately 65% more effective than free CPT to inhibit 100% cell growth on three different human liver carcinoma cell lines. Therefore, the OA-PL stabilized iron oxide formulation is ideal for achieving targeted and sustained CPT delivery in bioactive lactone form to overcome its handicaps in clinical conditions.

In-office and at-home bleaching techniques are widely used methods for the whitening of teeth. However, the safety of these techniques has not been clarified yet. The aim of the current study is to investigate the in-office- and at-home-bleaching-induced structural and quantitative changes in human enamel and dentin at the molecular level, under in vitro conditions. The Fourier transform mid-infrared (mid-FT-IR) spectroscopic technique was used to monitor bleaching-induced structural changes. Band frequency and intensity values of major absorptions such as amide A, amide I, phosphate (PO₄), and carbonate (CO₃⁻²) bands, for treatment groups and control, were measured and compared. The results revealed that both procedures have negligible effects on dentin constituents. In office-bleached enamel, in addition to demineralization, a decrease in protein and polysaccharide concentrations, mineral-to-protein ratio, and the strength of hydrogen bonds around NH groups, as well as a change in protein secondary structure were observed. The protein structure changed from β-sheet to random coil, which is an indication of protein denaturation. However, no significant variations were observed for at-home bleached enamel. The control, at-home, and in-office bleached enamel samples were differentiated with a high accuracy using cluster analysis based on FT-IR data. This study revealed that office bleaching caused deleterious alterations in the composition and structure of enamel that significantly affected the crystallinity and mineralization of the tissue. Therefore, at-home bleaching seems to be much safer than in-office bleaching in terms of molecular variations.