Bakır ve çinko içeren biyoaktif cam katkılı nanokompozit yapı iskelesi üretimi
Fabrication of nanocomposite scaffold with copper and zinc doped bioactive glasses
Yazar: ZEYNEP ATASAYAR
Danışman: PROF. DR. SADRİYE OSKAY
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / Kimya Mühendisliği Ana Bilim Dalı / Kimya Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2021
Konu: Biyomühendislik = Bioengineering ; Kimya Mühendisliği = Chemical Engineering

Özet:
Biyomalzemeler, insan vücudundaki canlı dokuların işlevlerini yerine getirmek ya da desteklemek amacıyla kullanılan doğal ya da sentetik malzemelerdir. Biyomalzemeler; metaller, seramikler, polimerler ve kompozit malzemeler kullanılarak üretilebilmektedir. Biyoseramikler biyouyumlulukları yüksek, korozyona dayanıklı fakat düşük mekanik dayanımda, kırılgan, yüksek yoğunluklu olma gibi özellikleriyle dikkat çekmektedirler. Biyoseramikler sınıfında incelenen biyoaktif camlar, SiO2, Na2O, CaO ve P2O5 bileşimlerinden oluşmaktadır.  En az iki farklı malzemenin birleşip bileşenlerinden farklı özellikte başka bir malzeme meydana getirmesiyle oluşan ve homojen özellik göstermesiyle kullanım açısından dezavantajlara sahip olan malzeme gruplarına alternatif olarak ise, kompozit biyomalzemeler geliştirilmiştir.
Bu çalışmada, sol-jel yöntemi kullanılarak nano boyutta olacak şekilde, katkısız ve Cu-Zn katkılı olarak üretilen üçlü SiO2-CaO-Na2O 58S biyoaktif cam sistemi, %25 oranında jelatin-kitosan polimer yapısına dahil edilerek nanokompozit  yapı iskeleleri üretimi amaçlanmıştır. Bu amaçla, karakterizasyon işlemleri yapılmıştır. Üretilen numunelerin, SEM(Taramalı elektron mikroskobu ), XRD (X-ışınları difraksiyonu), DLS (Dinamik ışık saçılım analizörü) cihazları kullanılarak karakterizasyonları yapılmıştır. Ayrıca, numunelerin biyoaktivite özellikleri yapay vücut sıvısı içerisinde bekletilerek belirlenmiştir. Numunelerin antibakteriyel özelliklerinin belirlenmesinde E. Coli bakterileri ve disk difüzyon yöntemi kullanılmıştır. 
Üretilen biyoaktif cam toz numunelerin yüzey karakterizasyonu SEM (Taramalı elektron mikroskobu), ve numunelerin amorf yapısı ise XRD (X-ışınları difraksiyonu) ile incelenmiştir. Buna göre üretilen her iki camın da nano boyutta ve amorf yapıda olduğu görülmüştür.
28 gün yapay vücut sıvısı içerisinde bekletilen yapı iskelelerinin yüzeyinde oluşan, yapının biyoaktif olduğunu gösteren hidroksiapatit tabakası SEM cihazı ile görüntülenmiş ve XRD ile amorf yapı içerisindeki hidroksiapatit pikleri tespit edilmiştir.
Cu-Zn katkılı 58S biyoaktif cam içerikli nanokompozit yapı iskelesi yapay vücut sıvısında belirli sürelerde bekletilmiştir. Bu sürelerin sonunda alınan yapay vücut sıvısındaki Cu ve Zn iyon derişimleri ICP-OES cihazı kullanılarak belirlenmiştir.
Numunelerin antibakteriyel testleri için E. Coli bakterisi kullanılmıştır. Disk difüzyon yöntemiyle bakteri besiyerine yerleştirilen numunelerde antibakteriyel özellik, çap ölçümüne göre yapılmıştır. 
Yapılan çalışmalar sonucunda, üretilen Cu-Zn içerikli biyoaktif cam katkılı nanokompozit yapı iskelesinin biyoaktif ve antibakteriyel özellikleri nedeniyle kemik-doku mühendisliğinde yapı iskelesi olarak kullanımının uygun olduğu sonucuna varılmıştır.

Abstract:
Biomaterials are natural or synthetic materials that are used to perform or support the functions of living tissues in the human body, and they come into contact with body fluids (such as blood) continuously or at regular intervals. Biomaterials can be produced using metals, ceramics, polymers and composite materials. Bioceramics are fragile, high density biomaterials with high biocompatibility, resistant to corrosion but low mechanical strength. Composite biomaterials have been developed as an alternative to material groups that are formed by the combination of at least two different materials to form another material with different properties from their components and have disadvantages in terms of use with their homogeneous properties. 
Examples of biocompatible ceramic materials are aluminum oxide, bioactive glass, carbon and hydroxyapatite. Bioactive glasses consist of SiO2, Na2O, CaO and P2O5 compounds. Sol-gel is a common way to produce bioactive glasses. The sol-gel process is based on inorganic polymerization chemistry. Starting from molecular precursors an oxide is obtained via hydroxylation-condensation reactions.
Nanotechnology is a versatile field to develop, to fabricate and to design materials and processes with nanosize.Nanotechnology is interested in nanomaterials that have considerable biological, chemical, magnetic and physical properties due to their nanoscale size.Nanotechnology have wide range of applications in the field of electronics, agriculture, food industry, biomedical, cosmetics, energy and environment.Application of nanotechnology to tissue engineering is a new and quickly expanding field and allows for the production of nano-sized bioactive glasses. Some techniques to fabricate nanoscale bioactive glasses have emerged; these are: sol-gel, laser spinning, microemulsion and gas-phase synthesis. The nanofeatures created by these techniques possess several novel properties to bioactive glass nano-particles such as, extremely high surface area to volume ratio, improved mechanical properties and bioactivity, and enhanced bone-forming cell adhesion and proliferation. These characteristics nanofeatures of bioactive glass nano-particles would make them promising materials that successfully exploited for a variety of health care applications ranging from drug delivery to biosensors. Nanoscale bioactive glasses have been used in the design of materials for biomedical applications. For example, combination of nanofibers or nanoparticles with a polymeric matrix to produce nanocomposites.
Nanofibers are one-dimensional (1D) nanomaterials with a "high surface-to-volume ratio"  due to nanometer scale and this property helps to increase interactions between the nanofibers and targeted substrates in many application fields especially in biomedical applications. They can be fabricated by various methods which are electrospinning, self assembly or template-assisted growth. Electrospinning method has many advantages in nanofiber production. The structure and size of the fibers produced by the electrospinning method are influenced by the solution, the process and the environmental parameters. The nanofiber mats with high porosity, gas permeability and high surface area produced by the electrospinning process can be used in a variety of biomedical applications such as wound dressings, drug delivery systems and tissue scaffolds. Nanofiber structures play an important role in promoting the proliferation and migration of cells in tissue engineering applications with structural similarity, which is an extracellular matrix (ECM).
In this study, it was aimed to produce nanocomposite scaffolds by incorporating the triple SiO2-CaO-Na2O 58S bioactive glass system without or with the addition of Cu-Zn, which was produced in nano-size by using sol-gel method, into the gelatin-chitosan polymeric structure with a ratio of 25%. For this purpose, characterization processes have been carried out. SEM (Scanning electron microscope), XRD (X-ray diffraction), DLS (Dynamic light scattering analyzer) devices were used for the produced samples. In addition, artificial body fluid was prepared for the determination of the bioactivity properties of the samples and the samples were kept in this fluid for certain periods. E. Coli bacteria and disk diffusion method were used to determine the antibacterial properties of the samples.
Surface characterization of the produced bioactive glass powder samples were examined by SEM (Scanning electron microscope), and the amorphous structure of the samples were examined by XRD (X-ray diffraction). According to SEM resultus, undoped 58S bioactive glasses are in spherical shape, on the other hand, Cu-Zn doped 58S bioactive glasses are not. The morphological features of the bioactive glasses effect the material's mechanical properties. Accordingly, it was observed that both doped and undoped 58S bioactive glasses were in nano-sized and amorphous structure.
The hydroxyapatite layer formed on the surface of the scaffolds kept in simulated body fluid for 28 days which shows it's bioactivity. The hydroxyapatite peaks in the amorphous structure were observed with XRD. Hydroxyapatite layer formed on the surface of the samples was observed by SEM. 
The nanocomposite scaffold containing Cu-Zn and 58S bioactive glass was kept in simulated body fluid for a certain period of time. At the end of these periods, Cu2+ and Zn2+ ion concentrations in the simulated body fluid were determined using ICP-OES device. High Cu2+ ion concentration values were determined than it was expected which means that the Cu-Zn doped bioactive glass nanocomposite scaffold may have cytotoxic efects. On the other hand, presence of Zn2+ ion may reduce the cytotoxic effects of Cu2+ ion. 
E. Coli bacteria was used for antibacterial tests of the samples. Antibacterial property of samples placed in bacterial media was determined according to the zone measurements. It was observed that all samples except gelatin-chitosan nanofiber sample showed antibacterial effect.
It can be seen that the addition of the metal ions improves the features of the scaffolds. The properties' of the nanocomposite scaffolds can be enhanced by changing the percentage of these metal ion containing. It was concluded that the bioactive glass-reinforced nanocomposite scaffold with Cu-Zn content produced within the scope of the study was suitable for use as a scaffold in bone-tissue engineering due to its bioactive and antibacterial properties.