Tantalum possesses remarkable chemical and mechanical properties, and thus it is considered to be one of the next generation implant materials. However, the biological properties of tantalum remain to be improved for its use in tissue engineering applications. To enhance its cellular interactions, implants made of tantalum could be modified to obtain nanofeatured surfaces via the electrochemical anodization process. In this study, anodization parameters were adjusted to obtain a nanoporous surface morphology on tantalum surfaces and systematically altered to control the pore sizes from 25 to 65 nm using an aqueous HF:H2SO4 electrolyte. Results indicated the formation of Ta2O5‐based nanoporous surface layers, which had up to 28% more surface area and increased nanophase roughness (more than twofolds) compared to nonporous tantalum upon the anodization. It was observed that the nanoporous tantalum oxide surfaces promoted nearly 25% more fibroblast proliferation at 5 days in vitro and 15.5% more cellular spreading. Thus, nanoporous tantalum oxide surfaces can be used to increase biological interactions of the cells and provide a means of improving bioactivity of tantalum for biomaterial applications.

Tissue engineering applications typically require three-dimensional scaffolds which provide the requisite surface area for cellular functions, while allowing transport of nutrients, waste and oxygen to and from the surrounding tissues. Scaffolds need to ensure sufficient mechanical properties to provide mechanically stable frameworks under physiologically relevant stress levels. Meanwhile, electrically conductive platforms are also desirable for the regeneration of specific tissues, where electrical impulses are transmitted throughout the tissue for proper physiological functioning. Towards this goal, carbon nanofibers (CNFs) were incorporated into silk fibroin (SF) scaffolds whose pore size and porosity were controlled during a salt leaching process. In our methodology, CNFs were dispersed in SF due to the hydrogen bond-forming ability of hexafluoro-2-propanol, a fluoroalcohol used as a solvent for SF. Results showed enhanced electrical conductivity and mechanical properties upon the incorporation of CNFs into the SF scaffolds, while the metabolic activities of cells cultured on SF/CNF nanocomposite scaffolds were significantly improved by optimizing the CNF content, porosity and pore size range of the scaffolds. Specifically, SF/CNF nanocomposite scaffolds with electrical conductivities as high as 0.023 S cm−1, tangent modulus values of 260 ± 30 kPa, a porosity as high as 78% and a pore size of 376 ± 53 µm were fabricated for the first time in the literature. Furthermore, an increase of about 34% in the wettability of SF was achieved by the incorporation of 10% CNF, which provided enhanced fibroblast spreading on scaffold surfaces.

The development of biodegradable polymeric nanofiber scaffolds for a potential effort to repair injured nerve cells is of great interest in nerve tissue engineering applications. Poly (L-lactic acid) (PLLA) has been widely used in nerve conduit studies due to its biocompatibility, easily shaped properties and degradation to low toxic lactic acid. However, its hydrophobicity and lack of binding sites for cellular activities restricts its use as implants. In this regard, this study involves the incorporation of graphene oxide (GO) into PLLA nanofibers for enhancing mechanical properties, electrical conductivity and hydrophilicity of PLLA to make it suitable for a potential peripheral nerve regeneration application. For this purpose, PLLA and PLLA/GO nanofibers were prepared via electrospinning. The processing parameters and solution parameters were optimized to adjust physical and mechanical properties of nanofiber in terms of size, porosity and biologically active affinity for cellular interaction. The morphology and composition of the developed electrospun fibers were characterized via, Scanning Electron Microscopy (SEM), Raman Spectroscopy, tensile testing and contact angle measurements. The morphological results showed that using chloroform/DMF ratio of 8/2 for 7wt% PLLA led to the formation of bead free and thinner PLLA fibers than fibers produced from other concentration of PLLA. Moreover, the addition of the GO resulted in decrease of the average diameter of PLLA fibers from 828 nm to 490 nm and the thinnest nanofiber structure was obtained by addition of 10 v/v % GO. The sonication time of GO highly enhanced the porosity of the nanofibers, namely the porosity of the nanofibers increased with increasing sonication time. Raman Spectroscopy exhibits peaks at bands of 1775, 873 and 1455 cm-1that are attributed to C=O stretching, C-COO stretching and CH3asymmetric deformation respectively for PLLA and 1379 and 1599 cm-1which represent structural imperfections and sp2 domain of carbon atoms respectively for GO. Hence, Raman peaks confirmed that GO was mixed in PLLA nanofibers. The incorporation of GO significantly improved the tensile strength from 2.25 MPa of pure PLLA to 8.13 MPa, 10.44 MPa and 12.93 MPa with 5, 7.5 and 10 v/v% of GO addition, respectively. The results revealed that the addition of GO led to enhanced chemical and physical properties of fibers which is promising for nerve regeneration applications.

Amaç: Periferal sinir hasarı ciddi bir sağlık sorunu olup hastanın hayat kalitesini ciddi olarak etkilemektedir. Periferal sinir hasarı çok yavaş iyileşir ve iki sinir ucu arasında mesafe çoksa, hiç iyileşemez. Bu sebeple, sinir hasarının tedavisi için farklı stratejiler geliştirilmektedir. Bu çalışmalar grafen oksit (GO)/polilaktik asit (PLLA) bazlı sinir iskelelerinin gelişmesini sağlamıştır. Bu iskeleler ile biyomalzemenin fiziksel, kimyasal ve biyolojik özelliklerinin geliştirilmesi hedeflenmiştir. Gereç ve Yöntem: Bu çalışmada, GO PLLA içerisine ilave edilmiştir ve elektroeğirme yöntemiyle matlar üretilmiştir. Daha sonra üretilen malzemelerin mekanik özellikleri ve biyouyumlulukları test edilmiştir. Bulgular: Üretilen GO/PLLA nanofiberler 381 MPa çekme modülüne ve 10 MPa çekme kuvvetine sahiptir. Bu değerler sinir dokusunun mekanik özelliklerine çok yakındır. Biyoyumluluk çalışmaları da üretilen biyomalzemelerin sinir hücresi gelişimine katkı sağladığını göstermiştir. Sonuç: Yapılan çalışmalar GO/PLLA bazlı nanofiberlerin sinir dokusu rejenerasyonu için ümit vaad ettiğini göstermiştir.

No abstract