Browsing by Author "Ozturk, S."
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Item Open Access Angiogenic heparin-mimetic peptide nanofiber gel improves regenerative healing of acute wounds(American Chemical Society, 2017) Uzunalli, G.; Mammadov R.; Yesildal, F.; Alhan, D.; Ozturk, S.; Ozgurtas, T.; Güler, Mustafa O.; Tekinay, A. B.Wound repair in adult mammals typically ends with the formation of a scar, which prevents full restoration of the function of the healthy tissue, although most of the wounded skin heals. Rapid and functional recovery of major wound injuries requires therapeutic approaches that can enhance the healing process via overcoming mechanical and biochemical problems. In this study, we showed that self-assembled heparin-mimetic peptide nanofiber gel was an effective bioactive wound dressing for the rapid and functional repair of full-thickness excisional wounds in the rat model. The bioactive gel-treated wounds exhibited increased angiogenesis (p < 0.05), re-epithelization (p < 0.05), skin appendage formation, and granulation tissue organization (p < 0.05) compared to sucrose-treated samples. Increased blood vessel numbers in the gel-treated wounds on day 7 suggest that angiogenesis played a key role in improvement of tissue healing in bioactive gel-treated wounds. Overall, the angiogenic heparin-mimetic peptide nanofiber gel is a promising platform for enhancing the scar-free recovery of acute wounds.Item Open Access Design of a high-resolution microfluidic microwave MEMS phase shifter(Wiley, 2011) Ozbey, B.; Ozturk, S.; Aktas, O.In this article, a novel microwave microelectromechanical phase shifter based on a microfluidic design is proposed and demonstrated. The design principles, the fabrication process, and experimental results (S-parameters and phase shift plots) are presented. The proposed system has a high bandwidth, high-power handling capacity, and a high-resolution along with a small settling time.Item Open Access Ethical issues in health communication: health-related news sourcing practices(Elsevier, 2018-10) Çaplı, Bülent; Ozaydin, S. K.; Ozturk, S.Item Open Access Expanded bodipy dyes: anion sensing using a bodipy analog with an additional difluoroboron bridge(American Chemical Society, 2012) Guliyev, R.; Ozturk, S.; Sahin, E.; Akkaya, E. U.Oxalyl-tethered pyrroles can be doubly bridged with two difluoroboron chelating units to yield bright orange dyes. Interestingly, in polar organic solvents, the addition of fluoride and cyanide result in reversible detachment of the otherwise stable difluoroboron bridges, resulting in sharp changes in color. Thus, this novel compound behaves as a highly selective chromogenic sensor for fluoride and cyanide ions.Item Open Access From virtual to physical: Integration of chemical logic gates(2011) Guliyev, R.; Ozturk, S.; Kostereli, Z.; Akkaya, E. U.Integration by parts: Advanced information processing at the molecular level requires integrated logic gates, which has to date been possible only virtually. Now, two independently working AND molecular logic gates are brought together by "click" chemistry to form integrated logic gates which respond exactly as predicted from such an integration scheme (see picture, EET=excitation energy transfer).Item Open Access Low leakage current operation of carbon nanotube network thin-film transistors at 100 degree celsius(2011) Ozturk, S.; Aktas O.In this work we present the elevated temperature operation of carbon nanotube thin film transistors up to 100 °C in air ambient. It is demonstrated that for semiconducting nanotubes the OFF current leakage does not increase and the high ON/OFF ratio of transistors consisting of semiconducting nanotubes is preserved up to 100 °C. In addition, we investigate the factors affecting the operation of carbon nanotube transistors at high temperature for a range of source-to-drain spacing and metallic tube contents. The influence of change in tube-tube and tube-metal contact resistance on the device characteristics at high temperature is demonstrated. © 2011 American Scientific Publishers.Item Open Access Mutations in RAD21 disrupt regulation of apob in patients with chronic intestinal pseudo-obstruction(W.B. Saunders, 2015) Bonora, E.; Bianco, F.; Cordeddu, L.; Bamshad, M.; Francescatto, L.; Dowless, D.; Stanghellini, V.; Cogliandro, R. F.; Lindberg, G.; Mungan, Z.; Cefle, K.; Ozcelik, T.; Palanduz, S.; Ozturk, S.; Gedikbasi, A.; Gori, A.; Pippucci, T.; Graziano, C.; Volta, U.; Caio, G.; Barbara, G.; D'Amato, M.; Seri, M.; Katsanis, N.; Romeo, G.; De Giorgio, R.Background Aims Chronic intestinal pseudo-obstruction (CIPO) is characterized by severe intestinal dysmotility that mimics a mechanical subocclusion with no evidence of gut obstruction. We searched for genetic variants associated with CIPO to increase our understanding of its pathogenesis and to identify potential biomarkers. Methods We performed whole-exome sequencing of genomic DNA from patients with familial CIPO syndrome. Blood and lymphoblastoid cells were collected from patients and controls (individuals without CIPO); levels of messenger RNA (mRNA) and proteins were analyzed by quantitative reverse-transcription polymerase chain reaction, immunoblot, and mobility shift assays. Complementary DNAs were transfected into HEK293 cells. Expression of rad21 was suppressed in zebrafish embryos using a splice-blocking morpholino (rad21a). Gut tissues were collected and analyzed. Results We identified a homozygous mutation (p.622, encodes Ala>Thr) in RAD21 in patients from a consanguineous family with CIPO. Expression of RUNX1, a target of RAD21, was reduced in cells from patients with CIPO compared with controls. In zebrafish, suppression of rad21a reduced expression of runx1; this phenotype was corrected by injection of human RAD21 mRNA, but not with the mRNA from the mutated p.622 allele. rad21a Morpholino zebrafish had delayed intestinal transit and greatly reduced numbers of enteric neurons, similar to patients with CIPO. This defect was greater in zebrafish with suppressed expression of ret and rad21, indicating their interaction in the regulation of gut neurogenesis. The promoter region of APOB bound RAD21 but not RAD21 p.622 Ala>Thr; expression of wild-type RAD21 in HEK293 cells repressed expression of APOB, compared with control vector. The gut-specific isoform of APOB (APOB48) is overexpressed in sera from patients with CIPO who carry the RAD21 mutation. APOB48 also is overexpressed in sporadic CIPO in sera and gut biopsy specimens. Conclusions Some patients with CIPO carry mutations in RAD21 that disrupt the ability of its product to regulate genes such as RUNX1 and APOB. Reduced expression of rad21 in zebrafish, and dysregulation of these target genes, disrupts intestinal transit and the development of enteric neurons.Item Open Access Sciatic nerve regeneration induced by glycosaminoglycan and laminin mimetic peptide nanofiber gels(Royal Society of Chemistry, 2016) Mammadov, B.; Sever, M.; Gecer, M.; Zor, F.; Ozturk, S.; Akgun, H.; Ulas, U. H.; Orhan, Z.; Güler, Mustafa O.; Tekinay, A. B.In the USA, 20 million patients suffer from neuropathy caused by peripheral nerve injuries, which costs approximately 150 billion annually. For longer nerve gaps and multiple injury sites, it is essential to use nerve guidance conduits for healthy pathfinding of regenerating axons. Here, extracellular matrix mimetic peptide nanofiber hydrogels were used for functionalizing guidance conduits to enhance neuronal regeneration in the distal stump of full transaction sciatic nerve injury in rats with functional repair. Conduits filled with heparan sulfate and laminin mimetic peptide nanofibers significantly improved electromyography response and promoted neuronal regeneration in a rat model of sciatic nerve defect. In addition, Schwann cells cultured on these nanofibers showed increased viability and significantly enhanced nerve growth factor (NGF) release. Overall, these results suggest that extracellular matrix mimetic peptide nanofibers present a promising treatment option for peripheral nerve injuries.