Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Research Project Kontrollü salım özelliklerine sahip antimikrobiyel, nanokompozit gıda ambalaj filmlerinin geliştirilmesi(TÜBİTAK - Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, 2013) Alsoy Altınkaya, Sacide; Pekşen Özer, Bahar Başak; Oymacı, Pelin; Uz, Metin; Büyüköz, MeldaAntimikrobiyal gıda ambalaj malzemelerinde aktif maddenin kontrollü salımı kritiktir. Bu çalışmada kontrollü salım antimikrobiyal ajanı nanotanecik içine yükleyerek sağlanmıştır. Doğal bir antimikrobiyal ajan olan lisozim serbest halde ya da poliakrilik asit (PAA) ile tanecik oluşturarak peynir altı suyu izolatı (WPI) filmlerine ilave edilmiştir. Serbest lisozim içeren filmlerden salımın çok hızlı olduğu, 45 dakika gibi kısa bir sürede lisozimin tamamının ortama geçtiği, PAA içine yüklenmesi durumunda ise salım hızının oldukça yavaşladığı gözlenmiştir. PAA’nın molekül ağırlığı ile PAA/LIS oranının lisozimin salım hızı üzerinde oldukça etkili olduğu belirlenmiştir. Her iki parametrenin artması ile daha büyük boyutta tanecikler elde edilmiş ve bu tanecikleri içeren filmlerden lisozimin salım hızı düşmüştür. Film hazırlama esnasında lisozimin aktivitesinde kayıp yaşanmış, ancak salınan aktivite zamanla değişim göstermemiştir. Lisozim hem serbest, hem de PAA/LIS kompleksi içinde filme ilave edildiğinde ortama kontrollü bir şekilde salınarak antimikrobiyal etkisini daha uzun süre koruyabilmiştir. Çalışmada PAA/LIS komplekslerinin yanısıra kitosan nanotanecikler de hazırlanmış, bu taneciklerin WPI filmlerinin mekanik ve bariyer özellikleri üzerine olan etkileri incelenmiştir. %2 oranına kadar kitosan nanotanecik içeren filmlerin mekanik ve bariyer özelliklerinde önemli bir değişiklik olmazken, % 4 nanotanecik ilavesiyle çekme mukavemetinde ani bir artış, % uzama değerinde ve su buharı geçirgenliğinde de azalma gözlenmiştir. Ayrıca, kitosan nanotanecikler WPI filmlere antibakteriyel özellik de kazandırmıştır. Filme ilave edilen nanotanecik miktarının % 6’ya artırılması sonucunda homojen dağılımın sağlanamamasından dolayı mekanik ve bariyer özelliklerindeki iyileşme azalmaya başlamıştır. Bu çalışmada elde edilen sonuçlara dayanarak kitosan nanotaneciklerin WPI filminin mekanik ve bariyer özelliklerinin iyileştirilmesinde, PAA/LIS komplekslerinin de kontrollü salım yapabilen, antimikrobiyal özelliğe sahip WPI filmlerinin hazırlanmasında kullanılabileceği düşünülmektedir.Research Project Nanolifli yapıda, sinir büyüme faktörü yüklü mikro küreleri içeren jalatin bazlı doku iskelelerinin hazırlanması ve karakterizasyonu(TÜBİTAK - Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, 2014) Altınkaya, Sacide; Erdal, Esra; Büyüköz, MeldaIn living organisms most of the tissues have the capability of regeneration; on the other hand, this situation is different in mammalian adult neural cells since they loose their ability of proliferation. Compared to peripheral nervous system, central nervous system has restricted regeneration capability which results in trauma, stroke and neuropathology etc. The first studies for the regeneration of nervous system concentrated on the use of autographs, tissue transplanted from one part of the body to another in the same individual, but it has limitations including short-age. Another type of investigation was allograft, which is transplantation of cells isolated from cadavers to the patient, but this approach is also not suitable because of host immune rejection. A new hope to cure neurodegenerative diseases appeared with biomaterials and tissue engineering studies. In this study, it is aimed to develop a novel, nanofibrous scaffolds with the capability of controlled releasing neural growth factor loaded in microspheres. Nanofibrous and oriented scaffolds were prepared from gelatin by a combination of thermally induced phase separation (TIPS), porogen-leaching and molding techniques while alginate microspheres were produced in oil in water emulsion through cross linking of alginate with calcium ions. The bioactivity of the growth factor released from microspheres was determined using PC12 cell line, derived from rat adrenal medulla and differentiate when treated with nerve growth factor. The scaffolds including connected pores with a high porosity, nanofibrous structure which mimic the extracellular matrix and properties similar to natural brain tissure were produced. Compared to solid walled scaffolds, nanofibrous scaffolds allow attachment of cells without any change in their morphologies. Model protein Į-chemotripsin and bovin serum albumin used for protecting the activity of nerve growth factor were loaded in alginate microspheres with an encapsulation efficiency of 100 %. It was found that NGF loaded into microspheres can maintain its activity and it can even differentiate PC-12 cells in a shorter time compared to NGF directly added into cell culture medium.Article Jelatin Doku İskelesinin Mekanik Özellikleri Üzerine Gözenek Oluşturucu Ajanın Boyutu ve Bağlantı Süresinin Etkileri(Manisa Celâl Bayar Üniversitesi, 2015) Büyüköz, Melda; Alsoy Altınkaya, SacideBu çalışmada, makrogözenekli ve gözenekleri birbirleri ile bağlantılı olarak kalıplama, ısı etkili faz ayrımı ve tanecik uzaklaştırma yöntemleri ile üretilen jelatin bazlı doku iskelelerinde gözenek oluşturucu ajan olan parafin kürelerin boyutu ve bağlantı sürelerinin doku iskelelerinin mekanik özellikleri üzerine olan etkileri incelenmiştir. Sünger formlu ve açık hücreli yapıda olan doku iskelelerinin mekanik özellikleri sıkıştırma testi ile ölçülmüştür. Yapılan ölçümler parafin küre çapındaki artışın doku iskelelerinin sıkıştırma katsayısını istatistiksel olarak anlamlı bir şekilde etkilemediğini göstermiştir. Ancak, parafin kürelerin maruz bırakıldığı ısı etkileşim süresinin 100 dakikadan 400 dakikaya arttırılmasının 250-425 µm çapındaki parafin kürelerle hazırlanan doku iskelesinin elastisite değerini arttırdığı belirlenmiştir (p<0.05). Ayrıca, 425-600 µm çapındaki parafin kürelerle hazırlanan doku iskelelerinde, ısı etkileşim süresi 100 dakikadan 400 dakikaya arttırıldığında sıkıştırma katsayısı anlamlı bir şekilde azalmıştır (p<0.05). Elde edilen sonuçlar, bu tür doku iskelelerinde parafin kürelerin boyutundan çok bağlantı süresinin mekanik özellikler üzerinde etkili olduğunu göstermiştirArticle Citation - WoS: 27Citation - Scopus: 37Nanofibrous Gelatine Scaffolds Integrated With Nerve Growth Factor-Loaded Alginate Microspheres for Brain Tissue Engineering(John Wiley and Sons Inc., 2018) Büyüköz, Melda; Erdal, Esra; Alsoy Altınkaya, SacideNeural regeneration research is designed in part to develop strategies for therapy after nerve damage due to injury or disease. In this study, a new gelatine-based biomimetic scaffold was fabricated for brain tissue engineering applications. A technique combining thermally induced phase separation and porogen leaching was used to create interconnected macropores and nanofibrous structure. To promote tissue regeneration processes, the scaffolds were integrated with nerve growth factor (NGF)-loaded alginate microspheres. The results showed that nanofibrous matrix could only be obtained when gelatine concentration was at least 7.5% (w/v). The scaffold with a modulus value (1.2 kPa) similar to that of brain tissue (0.5–1 kPa) was obtained by optimizing the heat treatment time, macropore size and gelatine concentration. The encapsulation efficiencies of NGF into 0.1% and 1% alginate microspheres were 85% and 100%, respectively. The release rate of NGF from the microspheres was controlled by the alginate concentration and the poly(L-lysine) coating. The immobilization of the microspheres in the scaffold reduced burst release and significantly extended the release period. The nanofibrous architecture and controlled release of NGF from the microspheres induced neurite extension of PC12 cells, demonstrating that the released NGF was in an active form. The results suggest that the scaffolds prepared in this study may have potential applications in brain tissue engineering due to topologic and mechanical properties similar to brain tissue and pore structure suitable for cell growth and differentiation.Article Citation - WoS: 40Citation - Scopus: 47Gelatin-Based 3d Conduits for Transdifferentiation of Mesenchymal Stem Cells Into Schwann Cell-Like Phenotypes(Elsevier Ltd., 2017) Uz, Metin; Büyüköz, Melda; Sharma, Anup D.; Sakaguchi, Donald S.; Alsoy Altınkaya, Sacide; Mallapragada, Surya K.In this study, gelatin-based 3D conduits with three different microstructures (nanofibrous, macroporous and ladder-like) were fabricated for the first time via combined molding and thermally induced phase separation (TIPS) technique for peripheral nerve regeneration. The effects of conduit microstructure and mechanical properties on the transdifferentiation of bone marrow-derived mesenchymal stem cells (MSCs) into Schwann cell (SC) like phenotypes were examined to help facilitate neuroregeneration and understand material-cell interfaces. Results indicated that 3D macroporous and ladder-like structures enhanced MSC attachment, proliferation and spreading, creating interconnected cellular networks with large numbers of viable cells compared to nanofibrous and 2D-tissue culture plate counterparts. 3D-ladder-like conduit structure with complex modulus of ∼0.4 × 106 Pa and pore size of ∼150 μm provided the most favorable microenvironment for MSC transdifferentiation leading to ∼85% immunolabeling of all SC markers. On the other hand, the macroporous conduits with complex modulus of ∼4 × 106 Pa and pore size of ∼100 μm showed slightly lower (∼65% for p75, ∼75% for S100 and ∼85% for S100β markers) immunolabeling. Transdifferentiated MSCs within 3D-ladder-like conduits secreted significant amounts (∼2.5 pg/mL NGF and ∼0.7 pg/mL GDNF per cell) of neurotrophic factors, while MSCs in macroporous conduits released slightly lower (∼1.5 pg/mL NGF and 0.7 pg/mL GDNF per cell) levels. PC12 cells displayed enhanced neurite outgrowth in media conditioned by conduits with transdifferentiated MSCs. Overall, conduits with macroporous and ladder-like 3D structures are promising platforms in transdifferentiation of MSCs for neuroregeneration and should be further tested in vivo. Statement of Significance This manuscript focuses on the effect of microstructure and mechanical properties of gelatin-based 3D conduits on the transdifferentiation of mesenchymal stem cells to Schwann cell-like phenotypes. This work builds on our recently accepted manuscript in Acta Biomaterialia focused on multifunctional 2D films, and focuses on 3D microstructured conduits designed to overcome limitations of current strategies to facilitate peripheral nerve regeneration. The comparison between conduits fabricated with nanofibrous, macroporous and ladder-like microstructures showed that the ladder-like conduits showed the most favorable environment for MSC transdifferentiation to Schwann-cell like phenotypes, as seen by both immunolabeling as well as secretion of neurotrophic factors. This work demonstrates the importance of controlling the 3D microstructure to facilitate tissue engineering strategies involving stem cells that can serve as promising approaches for peripheral nerve regeneration.