Bitkisel ekstraktlar kullanılarak antibakteriyel nanolif membranların üretimi
Production of antibacterial nanofiber membranes by using natural extracts
Yazar: EMİNE CANBAY GÖKÇE
Danışman: PROF. DR. MAHMUT ERCAN AÇMA
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Metalurji ve Malzeme Mühendisliği Ana Bilim Dalı
Derece: Yüksek Lisans, 2017
Konu: Mikrobiyoloji = Microbiology ; Polimer Bilim ve Teknolojisi = Polymer Science and Technology

Özet:
Nanoliflerin yüksek yüzey alanı, ayarlanabilir gözeneklilik ve eksenel mukavemet gibi özelliklere sahip olması nedeniyle son yıllarda önemi giderek artırmaktadır.  Biyomedikal, filtrasyon, kompozit ve enerji  gibi modern teknoloji  uygulama alanlarında kullanılan nanolifler birçok yöntem ile üretilebilmektedir. Ancak bu yöntemler arasında en yaygın olarak kullanılan elektroüretim (electrospinning) yöntemidir. Nanolif üretiminde elektrostatik alan kullanılması, düşük üretim hızı nedeniyle endüstriyel alanda pek tercih edilmemektedir. Faz ayırma tekniği ise malzeme ve proses güçlükleri nedeniyle ihtiyacı karşılama konusunda yetersiz kalmaktadır.  Bir başka yöntem olan eriyikten üfleme tekniğinin ise en önemli avantajı yüksek üretim hızıdır. Ancak bu yöntemin dezavantajları ise yüksek sıcaklıklarda hava kullanılması ve nano boyutlarda lif üretiminin limitli kalmasıdır.
Hali hazırda kullanılan metodların sınırlamalarını yok edecek tekniklerin geliştirilmesi akademik ve endüstriyel anlamda önemli bir gelişme olacaktır. Bu bağlamda yeni geliştirilen çözeltiden üfleme ve santrifüj eğirme yöntemi yüksek üretim hızına sahip olması ve elektrostatik kuvvetler yerine sırasıyla pnömatik ve merkezkaç kuvvetler vasıtasıyla üretim yapması dolayısıyla nanolif üretim teknikleri içinde önemli bir yere sahip olacaktır. Ancak santrifüj eğirme sisteminin endüstiyel üretime entegrasyonunda toplama yüzeyi gibi bazı zorlukların olduğu kaydedilmektedir. 
Gümüşün çok geniş spektrumlu bir antibiyotik olması, bakteri direncinin bulunmaması ve düşük konsantrasyonlarda toksik olmaması gibi avantajlardan dolayı en çok tercih edilen antibakteriyel malzeme olduğu bilinmektedir. Ancak son yıllarda yapılan araştırmalarda yararlı bakterileri de öldürdüğü ve yüksek miktarda gümüş iyonu içeren yara örtülerinin kullanımında hastalıklara yol açtığı belirtilmektedir. Bunlara ek olarak mikroorganizmaların mevcut antibiyotik ilaçlara karşı direnç kazanmaları nedeniyle araştırmacılar yeni antibakteriyel ajanlar bulma arayışına yönelmişlerdir. Bunun neticesi olarak da yapısındaki ikincil metabolitler sayesinde antibakteriyel etkinlik gösteren bitkiler ile ilgili çalışmalar yapmaya başlamışlardır. Çeşitli ekstraksiyon işlemlerini kullanarak fenolik, alkaloit ve terpenoit bileşenleri elde etmişlerdir. Daha sonra elde edilen bu bileşenler ile yapılan testlerde bunların antibakteriyel  olduğu ispatlanmıştır.
Bu tez çalışmasında yüksek üretim hızı, basit kurulum ve düşük maliyeti sebebiyle çözeltiden üfleme ile termoplastik poliüretan (TPU) nanolif yapıları üretilmiştir. Elde edilen nanolif yapılarının biyomedikal ürün olarak kullanılması için bunlara antibakteriyel özellik kazandırılmıştır.
Antibakteriyel ajan olarak karanfil ve duman ağacı bitkilerinin etkinliği araştırılmıştır. Yapılan çalışmalar neticesinde karanfil ve duman ağacı bitkilerinin antibakteriyel etkinlik gösterdiği gözlemlenmiştir.
Üretilen TPU nanolif yapıları antibakteriyel özütlerle kaplanarak antibakteriyel nanolif üretilmiştir. Nihai ürün yapılarının morfolojisi, antibakteriyel ajanın içeriği ve etkinliği (difüzyon agar ve zaman etkisi), hava geçirgenliği incelenmiş ve test sonuçları uygulamaya yönelik değerlendirilmiştir.

Abstract:
The importance of nanofibers has increased in modern technology such as biomedical, filtration, composite and energy due to their high surface area and scalable porosity. The nanofibers has produced via a lot of methods which are electrospinning, phase seperation, melt blowing, centrifugal spinning and solution blowing. Electrospinning is method that has widely used in nanofiber production. The usage area in industry is pretty limited because of utilization of electric field and low production rate in nanofiber fabrication. The phase seperation technique is inadequate about meeting the requirements due to constraint of material and processing. Although melt blowing has high production rate, it has negative properties such as usage of air at high temperature and limited of fiber production at nano scale. The techniques which annihilate constraint of available methods will be significant improvement. Thus, solution blowing and centrifugal spinning techniques possess a important position within nanofiber production techniques in terms of fabrication via pneumatic and centrifugal forces, respectively. However, centrifugal spinning possess constraint instead of collector for industial integration.
The silver has known the most favourite antibacterial material because it is wide spectrum antibiotic, no bacterial resistance and no toxic at low concentrations. However, studies in recent years have indicated that wound dressings including silver ions cause disase. Also silver kills beneficial bacterias. In addiation, organic synthetic antibacterial agents such as triclosan, which used as disinfectant were prohibited in USA. As a result of the investigations, triclosan was found to cause cancer. On the other hand, microorganisms has been resistance against multidrug. Thus, researchers have needed new area such as plant due to their secondary metabolite being antimicrobial. They obtained components of terpenoid, alkaloid and flavanoid by using different extraction methods. In addiation, they reported their antibacterial, antifungal, anticarcinogenic, antiviral and antioxidant properties. 
In this study, the solution blowing was used due to high production rate, simple setup and low cost. Thermoplastic polyurethane (TPU) was selected as a carrier due to its excellent elastomechanical properties and biocompatibility The 13wt% TPU solution was prepared in N,N dimethylformamid. After that TPU nanofiber was produced by solution blowing technique which was set air pressure of 3 bars, flow rate of 10 ml/h and working distance of 30 cm. 
The clove and smoke tree has been used for many years in the traditional medicine in Anatolia. These plants have been selected in terms of their growth in our country. medicine The clove and smoke tree were investigated as a antibacterial agent. After literature review, clove (30 g) and smoke tree (15 g) were obtained by soxhlet extraction method by using ethanol (450 ml) as a solvent. The solvent was evaporated via rotary evaporator. The gas chromatography mass spectrometry (GC-MS) was performed to determine chemical compounds of clove and smoke tree essential oils.  
To obtain antibacterial membrane, nanofiber were coated with plant extracts in different amount (2 mg/cm2, 5 mg/cm2, 10 mg/cm2) by drop-casting method. The morphology of samples were evaluated via scanning electron microscopy (SEM). Apart from that air permeability of nanofibers were realized via Air Tester according to ASTM D737 standard. In order to determine antibacterial efficiency diffusion agar and time-killing assay were conducted.
In the GC-MS analyses, it was shown that clove oil has eugenol (81.84wt%), eugenol acetate (9.88wt%) and β-caryophylene (6.9wt%) in accordance with literature. But it was observed that smoke tree oil possess pyrogallol (39.09wt%), quinic acid (9.9wt%), linoleic acid (9.27wt%), 3-pentadecyl phenol (9.25wt%), and eugenol (2.3wt%) even though there is limonene and β-caryophylene in the literature. These compounds are antimicrobial, antioxidant, antiinflamatuar. 
According to SEM images, the formation of beaded nanofiber was observed with increase amount of clove oil. It means that there was a physical bond between clove essential oil and TPU nanofiber. Also film structure formation in nanofiber including smoke tree was found with rise in quantity of smoke tree oil. However, presence of clove oil did not affect fiber morphology of E2/TPU, significantly. On the other hand, the results demonstrated that smoke tree was covered the nanofibers with excellent penetration. It is shown that there was a chemical bond between smoke tree essential oil and TPU nanofiber. 
As shown in results of air permeability, the permeability was decreased with increase in amount of essential oil. Especially, air perm values of K10 and D10 are lower than others.
In the results of diffusion agar method, the inhibition zones of samples was increased with rise in quantity of essential oil. K2, K5 and K10 had inhibition diameters of 23 mm, 24 mm, and 25 mm against E.coli and S.aureus, respectively. Moreover D2, D5 and D10 showed that inhibition diameters of 23 mm, 24 mm, and 25 mm against E.coli and S.aureus, respectively. Although coating amount of 2 mg/cm2 was found lower than others, 5 mg/cm2 was optimum value for clove and smoke tree essential oils. To summarize it was effective both against Gram positive (S.aureus) and Gram negative (E.coli) bacterias.
According to results of comparative diffusion agar test with commercial wound dressings (Aquacell Ag®, Mepilex® Border EM ve Chlorhexidine Gauze Dressing B.P. '93®) K10-D10 and Aquacell Ag® and  Chlorhexidine Gauze Dressing B.P. '93® exhibite similar antibacterial efficiency. However, Mepilex® Border EM does not show antibacterial activity because it does not include any antibacterial agent. According to results of these diffusion agar tests, K10 and D10 was found more efficient than Aquacell Ag®  including 12mg/g Ag+ and  Chlorhexidine Gauze Dressing B.P. '93® containing 0.5% (w/w) wound dressings.
The time killing assay showed that colony count of E.coli was decreased more than S.aureus significantly with essential oils within the first 6 hours. Commonly, after 6 hours the number of colony in both samples remained almost constant so no important change in colony count was recorded between 6-24 hours. It is thought that the release of antibacterial extract on the surface is completed within 6 hours. Even though both of them showed  similar values for time killing assay, smoke tree extract had more antibacterial efficiency than clove extract because smoke tree oil was prepared from 15 g of raw material, while clove oil was obtained from 30 g of raw material.
In brief, coating amount of 5 mg/cm2 can be candidate for commercial product such as wound dressing and biocidal air filter due to results of antibacterial and air permeability tests.