by Keyword: Nanofibers

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Sachot, N., Roguska, A., Planell, J. P., Lewandowska, M., Engel, E., Castaño, O., (2017). Fast-degrading PLA/ORMOGLASS fibrous composite scaffold leads to a calcium-rich angiogenic environment International Journal of Nanomedicine 12, 4901-4919

The success of scaffold implantation in acellular tissue engineering approaches relies on the ability of the material to interact properly with the biological environment. This behavior mainly depends on the design of the graft surface and, more precisely, on its capacity to biodegrade in a well-defined manner (nature of ions released, surface-to-volume ratio, dissolution profile of this release, rate of material resorption, and preservation of mechanical properties). The assessment of the biological behavior of temporary templates is therefore very important in tissue engineering, especially for composites, which usually exhibit complicated degradation behavior. Here, blended polylactic acid (PLA) calcium phosphate ORMOGLASS (organically modified glass) nanofibrous mats have been incubated up to 4 weeks in physiological simulated conditions, and their morphological, topographical, and chemical changes have been investigated. The results showed that a significant loss of inorganic phase occurred at the beginning of the immersion and the ORMOGLASS maintained a stable composition afterward throughout the degradation period. As a whole, the nanostructured scaffolds underwent fast and heterogeneous degradation. This study reveals that an angiogenic calcium-rich environment can be achieved through fast-degrading ORMOGLASS/PLA blended fibers, which seems to be an excellent alternative for guided bone regeneration.

Keywords: Angiogenesis, Calcium release, Electrospinning, Fast degradation, Nanofibers, ORMOGLASSES

Gugutkov, D., Gustavsson, J., Cantini, M., Salmeron-Sánchez, M., Altankov, G., (2017). Electrospun fibrinogen-PLA nanofibres for vascular tissue engineering Journal of Tissue Engineering and Regenerative Medicine

Here we report on the development of a new type of hybrid fibrinogen-polylactic acid (FBG-PLA) nanofibres (NFs) with improved stiffness, combining the good mechanical properties of PLA with the excellent cell recognition properties of native FBG. We were particularly interested in the dorsal and ventral cell response to the nanofibres' organization (random or aligned), using human umbilical endothelial cells (HUVECs) as a model system. Upon ventral contact with random NFs, the cells developed a stellate-like morphology with multiple projections. The well-developed focal adhesion complexes suggested a successful cellular interaction. However, time-lapse analysis shows significantly lowered cell movements, resulting in the cells traversing a relatively short distance in multiple directions. Conversely, an elongated cell shape and significantly increased cell mobility were observed in aligned NFs. To follow the dorsal cell response, artificial wounds were created on confluent cell layers previously grown on glass slides and covered with either random or aligned NFs. Time-lapse analysis showed significantly faster wound coverage (within 12 h) of HUVECs on aligned samples vs. almost absent directional migration on random ones. However, nitric oxide (NO) release shows that endothelial cells possess lowered functionality on aligned NFs compared to random ones, where significantly higher NO production was found. Collectively, our studies show that randomly organized NFs could support the endothelization of implants while aligned NFs would rather direct cell locomotion for guided neovascularization.

Keywords: Electrospun nanofibers, Endothelial cells, Fibrinogen, Guided cellular behavior, Polylactic acid, Vascular tissue engineering

Gugutkov, D., Awaja, F., Belemezova, K., Keremidarska, M., Krasteva, N., Kuyrkchiev, S., GallegoFerrer, G., Seker, S., Elcin, A. E., Elcin, Y. M., Altankov, G., (2017). Osteogenic differentiation of mesenchymal stem cells using hybrid nanofibers with different configurations and dimensionality Journal of Biomedical Materials Research - Part A 105, (7), 2065-2074

Novel hybrid, fibrinogen/polylactic acid (FBG/PLA) nanofibers with different configuration (random vs. aligned) and dimensionality (2D vs.3D environment) were used to control the overall behaviour and the osteogenic differentiation of human Adipose Derived Mesenchymal Stem Cells (ADMSCs). Aligned nanofibers in both the 2D and 3D configurations are proved to be favoured for osteo-differentiation. Morphologically we found that on randomly configured nanofibers, the cells developed a stellate-like morphology with multiple projections, however, time-lapse analysis showed significantly diminished cell movements. Conversely, an elongated cell shape with advanced cell spreading and extended actin cytoskeleton accompanied with significantly increased cell mobility were observed when cells attached on aligned nanofibers. Moreover, a clear tendency for higher alkaline phosphatase activity was also found on aligned fibres when ADMSCs were switched to osteogenic induction medium. The strongest accumulation of Alizarin red (AR) and von Kossa stain at 21 day of culture in osteogenic medium were found on 3D aligned constructs while the rest showed lower and rather undistinguishable activity. Quantitative reverse transcription-polymerase chain reaction analysis for Osteopontin (OSP) and RUNX 2 generally confirmed this trend showing favourable expression of osteogenic genes activity in 3D environment particularly in aligned configuration.

Keywords: Mesenchymal stem cells, Nanofibers, Osteogenic, Fibrinogen, Cell movements

Forget, J., Awaja, F., Gugutkov, D., Gustavsson, J., Gallego Ferrer, G., Coelho-Sampaio, T., Hochman-Mendez, C., Salmeron-Sánchez, M., Altankov, G., (2016). Differentiation of human mesenchymal stem cells toward quality cartilage using fibrinogen-based nanofibers Macromolecular Bioscience 16, (9), 1348-1359

Mimicking the complex intricacies of the extra cellular matrix including 3D configurations and aligned fibrous structures were traditionally perused for producing cartilage tissue from stem cells. This study shows that human adipose derived mesenchymal stem cells (hADMSCs) establishes significant chondrogenic differentiation and may generate quality cartilage when cultured on 2D and randomly oriented fibrinogen/poly-lactic acid nanofibers compared to 3D sandwich-like environments. The adhering cells show well-developed focal adhesion complexes and actin cytoskeleton arrangements confirming the proper cellular interaction with either random or aligned nanofibers. However, quantitative reverse transcription-polymerase chain reaction analysis for Collagen 2 and Collagen 10 genes expression confirms favorable chondrogenic response of hADMSCs on random nanofibers and shows substantially higher efficacy of their differentiation in 2D configuration versus 3D constructs. These findings introduce a new direction for cartilage tissue engineering through providing a simple platform for the routine generation of transplantable stem cells derived articular cartilage replacement that might improve joint function.

Keywords: Cartilage, Chondrogenic response, Collagen, FBG/PLA nanofibers, Mesenchymal stem cells

Álvarez, Z., Castaño, O., Castells, A. A., Mateos-Timoneda, M. A., Planell, J. A., Engel, E., Alcántara, S., (2014). Neurogenesis and vascularization of the damaged brain using a lactate-releasing biomimetic scaffold Biomaterials 35, (17), 4769-4781

Regenerative medicine strategies to promote recovery following traumatic brain injuries are currently focused on the use of biomaterials as delivery systems for cells or bioactive molecules. This study shows that cell-free biomimetic scaffolds consisting of radially aligned electrospun poly-l/dl lactic acid (PLA70/30) nanofibers release l-lactate and reproduce the 3D organization and supportive function of radial glia embryonic neural stem cells. The topology of PLA nanofibers supports neuronal migration while l-lactate released during PLA degradation acts as an alternative fuel for neurons and is required for progenitor maintenance. Radial scaffolds implanted into cavities made in the postnatal mouse brain fostered complete implant vascularization, sustained neurogenesis, and allowed the long-term survival and integration of the newly generated neurons. Our results suggest that the endogenous central nervous system is capable of regeneration through the invivo dedifferentiation induced by biophysical and metabolic cues, with no need for exogenous cells, growth factors, or genetic manipulation.

Keywords: Lactate, Nanofibers, Neural stem cells, Neurogenesis, Regeneration, Vascularization

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