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Electrospinning is a well-known technique that produces polymeric nanofibers using an electrically driven jet of a polymer solution. Due to unique properties such as high surface area, porosity, tensile strength and extensibility of the materials produced by electrospinning, several applications of them in protective clothing, space technology, filtration and tissue engineering have been proposed and investigated. In this study; we prepared gelatin nanofibrous scaffolds by using the electrospinning method for tissue engineering applications. The beads-free, smooth and uniform gelatin nanofibers were successfully fabricated. The blend solutions at different weight ratios were prepared by dissolving gelatin in a solvent mixture containing formic acid, dichloromethane and acetic acid. The fabricated nanofibers were chemically crosslinked by glutaraldehyde vapor. The crosslinked nanofibrous scaffolds were characterized by chemical and morphological analysis. The morphology and size distribution curves of nanofibers were determined by Scanning electron microscopy (SEM). The chemical structure of nanofibers was investigated by Fourier transform infrared spectroscopy (FTIR) analysis. The strategy based on electrospinning of gelatin nanofibers can be used to develop new biomimetic materials for tissue engineering applications.

Tissue engineering aims regenerating damaged tissues by using porous scaffolds, cells and bioactive agents. The scaffolds are produced from a variety of natural and synthetic polymers. Collagen is a natural polymer widely used for scaffold production in the late years because of its being the most important component of the connective tissue and biocompatibility. Cryogelation is a relatively simple technique compared to other scaffold production methods, which enables to produce interconnected porous matrices from the frozen reaction mixtures of polymers or monomeric precursors. Considering these, collagen was isolated in this study from fish skin which is a non-commercial waste material, and scaffolds were produced from this collagen by cryogelation method. By SEM analysis, porous structure of collagen, and by UV-Vis analysis protein structure was proven, and by Zeta potential iso-electrical point of the protein was determined, and, Amit A, Amit B, Amit I, Amit II and Amit III characteristical peaks were demonstrated by FTIR analysis. The collagen isolation yield was, 14.53% for acid soluble collagen and 2.42% for pepcin soluble collagen. Scaffolds were produced by crosslinking isolated acid soluble collagen with glutaraldehyde at cryogenic conditions. With FTIR analysis, C=N bond belonging to gluteraldehyde reaction with collagen was found to be at 1655 cm-1. It was demonstrated by SEM analysis that collagen and glutaraldeyhde concentration had significant effects on the pore morphology, diameter and wall thickness of the cryogels, which in turned changed the swelling ratio and degradation profiles of the matrices. In this study, synthesis and characterization results of a fish skin isolated collagen cryogel scaffold that may be potentially used in the regeneration of damaged tissues are presented.

Bolgen, Nimet/0000-0003-3162-0803; Meydanli, E. Elif Guzel/0000-0001-9072-3322; Cetinkaya, Duygu Uckan/0000-0003-3593-6493; KILIC, Emine/0000-0003-2984-7638; Weeks, Jason/0000-0001-5537-6927 WOS: 000463175200003 PubMed: 30942631 Repair of cranial bone defects is an important problem in the clinical area. The use of scaffolds combined with stem cells has become a focus in the reconstruction of critical-sized bone defects. Electrospinning became a very attracting method in the preparation of tissue engineering scaffolds in the last decade, due to the unique nanofibrous structure of the electrospun matrices. However, they have a limitation for three dimensional (3D) applications, due to their two-dimensional structure and pore size which is smaller than a cellular diameter which cannot allow cell migration within the structure. In this study, electrospun poly(epsilon-caprolactone) (PCL) membranes were spirally wounded to prepare 3D matrices composed of nanofibers and macrochannels. Mesenchymal stromal/stem cells were injected inside the scaffolds after the constructs were implanted in the cranial bone defects in rats. New bone formation, vascularisation and intramembranous ossification of the critical size calvarial defect were accelerated by using mesenchymal stem cells combined 3D spiral-wounded electrospun matrices. Turkish Academy of SciencesTurkish Academy of Sciences This study was performed in the context of the EU-FP6-NoE Expertissues Project. Erhan Piskin is supported by Turkish Academy of Sciences as a Honorary Member. This study was a part of PhD thesis of smail Alper isoglu. The thesis was supervised by Erhan Piskin.

Chitosan is a natural polymer synthesized from the chitin of crab, lobster shells, fungal mycelia and shrimp. It has been used for biomedical applications in many different structures including thin film, nanofibrous membrane, sponge, microsphere, hydrogel and cryogel because of its non-toxicity, biodegradability, biocompatibility and antibacterial properties. Cryogelation technique is based on the crosslinking of polymers or crosslinking polymerization of monomers in the presence of crosslinking agents at temperatures below zero. On the other hand, hydrogels are mainly prepared at room temperature. In this study, chitosan gels were prepared at different reaction temperatures (-25, 0 and +25°C). Swelling profiles revealed that with decreasing reaction temperature swelling ratio increased. In addition, the degradation rate of chitosan gels prepared at -25 and +25°C was measured 50.60 and 30.88%, respectively. Results indicate that reaction temperature affects the architecture and characterization results of the gels.

International audience; The temperature-induced structural modifications of poly(N-isopropylacrylamide) hydrogel (pNIPA) were investigated by small-angle X-ray scattering (SAXS) over a broad range of q values (3.5 x 10(-2)-12 nm(-1)) at temperatures ranging between 18 and 37 degrees C. The sample Studied was claborated by cryopolymerization yielding a macroporous gel (cryogel). The pNIPA gel forms the walls (the thickness at 23 degrees C is about 12 mu m). The SAXS curves display an isoscattering (or isosbestic) point located at q(iso) = 3.633 nm(-1) and disappearingabovc 30 degrees C. This feature has never been reported up to now. The SAXS curves obtained at each temperature are well fitted by a sum of four equations describing respectively the scattering resulting from the gel surface (power law), from the solidlike (Guinier equation) and liquidlike (Ornstein - Zernike equation) heterogeneities, and from the chain-chain correlation yielding a broad peak (pseudo-Voigt equation) in the high-q domain. The temperature dependence of the parameters obtained from the fit is analyzed and discussed.

International audience; Two-photon fluorescence microscopy (TPFM) usually used to get 3-D pictures of biological systems has been applied here for the first time to macroporous hydrogels prepared by cryogelation ("cryogels"). Unlike environmental scanning electron microscopy (ESEM) which analyzes the surface of swollen samples, TPFM delivers images of successive planes in the depth of the material allowing a 3-D imaging of its structure. The macroporous hydrogels studied were poly(N-isopropylacrylamide) (pNIPA), poly(Hydroxyethyl Methacrylate-L-Lactide-Dextran) (pHEMA-LLA-D) and various co-polymeric gels of these two ones. A quantification of the macropore size distribution and the wall thickness and their modification with respect to the ratio NIPA/HEMA-LLA-D or to the temperature, in the case of pNIPA, was readily obtained.

Cartmell, Sarah/0000-0001-6864-0846; Bolgen, Nimet/0000-0003-3162-0803; Bolgen, Nimet/0000-0003-3162-0803; Meydanli, E. Elif Guzel/0000-0001-9072-3322; KORKUSUZ, PETEK/0000-0002-7553-3915 WOS: 000268940100019 PubMed: 18671271 Reconstruction of large bone defects is still a major problem. Tissue-engineering approaches have become a focus in regeneration of bone. In particular, critical-sized defects do not ossify spontaneously. The use of electrospinning is attracting increasing attention in the preparation of tissue-engineering scaffolds. Recently, acellular scaffolds carrying bioactive agents have been used as scaffolds in "in situ" tissue engineering for soft and hard tissue repair. Poly(epsilon-caprolactone) (PCL) with two different molecular weights were synthesized, and the blends of these two were electrospun into nonwoven membranes composed of nanofibers/micropores. To stimulate bone formation, an active drug, "simvastatin" was loaded either after the membranes were formed or during electrospinning. The matrices were then spiral-wound to produce scaffolds with 3D-structures having both macro- and microchannels. Eight-millimeter diameter critical size cranial defects were created in rats. Scaffolds with or without simvastatin were then implanted into these defects. Samples from the implant sites were removed after 1, 3, and 6 months postimplantation. Bone regeneration and tissue response were followed by X-ray microcomputed tomography and histological analysis. These in vivo results exhibited osseous tissue integration within the implant and mineralized bone restoration of the calvarium. Both microCT and histological data clearly demonstrated that the more successful results were observed with the "simvastatin-containing PCL scaffolds," in which simvastatin was incorporated into the PCL scaffolds during electrospinning. For these samples, bone mineralization was quite significant when compared with the other groups. (C) 2008 Wiley Periodicals, Inc. J Biomed Mater Res 90A: 1137-1151, 2009 Turkish Scientific and Technological CouncilTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [105T509]; Turkish Academy of Sciences (TUBA)Turkish Academy of Sciences; BiyomedtekHacettepe University Contract grant sponsor: Turkish Scientific and Technological Council (Turkish Scientific and Technological Research Council, TUBITAK, Project: Tissuebiomed); contract grant number: 105T509; Contract grant sponsor: Turkish Academy of Sciences (TUBA); Contract grant sponsor: Biyomedtek

The aim of this study was to prepare non-woven materials from a biodegradable polymer, poly(epsilon-caprolactone) (PCL) by electrospinning. PCL was synthesized by ring-opening polymerization of epsilon-caprolactone in bulk using stannous octoate as the catalyst under nitrogen atmosphere. PCL was then processed into non-woven matrices composed of nanofibers by electrospinning of the polymer from its solution using a high voltage power supply. The effects of PCL concentration, composition of the solvent (a mixture of chloroform and DMF with different DMF content), applied voltage and tip-collector distance on fiber diameter and morphology were investigated. The diameter of fibers increased with the increase in the polymer concentration and decrease in the DMF content significantly. Applied voltage and tip-collector distance were found critical to control 'bead' formation. Elongation-at-break, ultimate strength and Young's modulus were obtained from the mechanical tests, which were all increased by increasing fiber diameter. The fiber diameter significantly influenced both in vitro degradation (performed in Ringer solution) and in vivo biodegradation (conducted in rats) rates. In vivo degradation was found to be faster than in vitro. Electrospun membranes were more hydrophobic than PCL solvent-casted ones; therefore, their degradation was a much slower process.