by Keyword: Polylactic acid

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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

Keremidarska, M., Gugutkov, D., Altankov, G., Krasteva, N., (2015). Impact of electrospun nanofibres orientation on mesenchymal stem cell adhesion and morphology Comptes Rendus de L'Academie Bulgare des Sciences 68, (10), 1271-1276

Electrospun nanofibrous materials mimicking the architecture of native extracellular matrix (ECM) hold great promise as scaffolds in tissue engineering. In order to optimize the properties of nanofibrous scaffolds it is important to understand the impact of fibres’ organization on cell behaviour. Herein, we investigated the effect of nanofibres (NFs) alignment on human adipose-derived mesenchymal stem cells (hAD-MSCs) adhesion and morphology. Electrospun composite fibrinogen/poly-lactic acid (FNG/PLA) NF scaffolds with same composition and comparable fibre size were fabricated into randomly oriented and aligned configuration and stem cells adhesion was characterized by the meaning of overall cell morphology, actin cytoskeleton organization and expression of molecules, involved in the development of focal adhesion complexes. We found that hAD-MSCs altered their morphology, actin cytoskeleton and cell attachment in accordance with nanofibre orientation while cell spreading, focal adhesions and expression of β1 and αNintegrin receptors were not influenced significantly by fibre orientation. These results confirmed that fibre alignment of scaffold guide cellular arrangement and could be beneficial for stem differentiation and therefore for the successful scaffolds development if its contact guidance coincided with the cell shape and cytoskeletal tension.

Keywords: Electrospinning, Fibrinogen/polylactic acid hybrid nanofibres, Human adipose-derived stem cells

Serra, T., Ortiz-Hernandez, M., Engel, E., Planell, J. A., Navarro, M., (2014). Relevance of PEG in PLA-based blends for tissue engineering 3D-printed scaffolds Materials Science and Engineering: C 38, (1), 55-62

Achieving high quality 3D-printed structures requires establishing the right printing conditions. Finding processing conditions that satisfy both the fabrication process and the final required scaffold properties is crucial. This work stresses the importance of studying the outcome of the plasticizing effect of PEG on PLA-based blends used for the fabrication of 3D-direct-printed scaffolds for tissue engineering applications. For this, PLA/PEG blends with 5, 10 and 20% (w/w) of PEG and PLA/PEG/bioactive CaP glass composites were processed in the form of 3D rapid prototyping scaffolds. Surface analysis and differential scanning calorimetry revealed a rearrangement of polymer chains and a topography, wettability and elastic modulus increase of the studied surfaces as PEG was incorporated. Moreover, addition of 10 and 20% PEG led to non-uniform 3D structures with lower mechanical properties. In vitro degradation studies showed that the inclusion of PEG significantly accelerated the degradation rate of the material. Results indicated that the presence of PEG not only improves PLA processing but also leads to relevant surface, geometrical and structural changes including modulation of the degradation rate of PLA-based 3D printed scaffolds.

Keywords: 3D-printing, Polylactic acid, Rapid prototyping, Scaffold, Surface characterization

Álvarez, Zaida, Mateos-Timoneda, Miguel A., Hyrossová, Petra, Castaño, Oscar, Planell, Josep A., Perales, José C., Engel, Elisabeth, Alcántara, Soledad, (2013). The effect of the composition of PLA films and lactate release on glial and neuronal maturation and the maintenance of the neuronal progenitor niche Biomaterials 34, (9), 2221-2233

To develop tissue engineering strategies useful for repairing damage in the central nervous system (CNS) it is essential to design scaffolds that emulate the NSC niche and its tight control of neural cell genesis, growth, and differentiation. In this study we tested two types of poly l/dl lactic acid (PLA95/5 and PLA70/30), a biodegradable material permissive for neural cell adhesion and growth, as materials for nerve regeneration. Both PLA were slightly hydrophobic and negatively charged but differed in crystallinity, stiffness and degradation rate. PLA95/5 films were highly crystalline, stiff (GPa), and did not degrade significantly in the one-month period analyzed in culture. In contrast, PLA70/30 films were more amorphous, softer (MPa) and degraded faster, releasing significant amounts of lactate into the culture medium. PLA70/30 performs better than PLA95/5 for primary cortical neural cell adhesion, proliferation and differentiation, maintaining the pools of neuronal and glial progenitor cells in vitro. l-lactate in the medium recapitulated PLA70/30's maintenance of neuronal restricted progenitors but did not sustain bipotential or glial restricted progenitors in the cultures, as occurred when neural cells were grown on PLA70/30. Our results suggest that PLA70/30 may mimic some of the physical and biochemical characteristics of the NSC niche. Its mechanical and surface properties may act synergistically in the modulation of bipotential and glial restricted progenitor phenotypes, while it is l-lactate, either added to the medium or released by the film that drives the maintenance of neuronal restricted progenitor cell phenotypes.

Keywords: Polylactic acid, Degradation, Neurons, Progenitors, Lactate, Glial cells, NSC niche

Serra, T., Planell, J. A., Navarro, M., (2013). High-resolution PLA-based composite scaffolds via 3-D printing technology Acta Biomaterialia 9, (3), 5521-5530

Fabrication of new biodegradable scaffolds that guide and stimulate tissue regeneration is still a major issue in tissue engineering approaches. Scaffolds that possess adequate biodegradability, pore size, interconnectivity, bioactivity and mechanical properties in accordance with the injured tissue are required. This work aimed to develop and characterize three-dimensional (3-D) scaffolds that fulfill the aforementioned requirements. For this, a nozzle-based rapid prototyping system was used to combine polylactic acid and a bioactive CaP glass to fabricate 3-D biodegradable scaffolds with two patterns (orthogonal and displaced double layer). Scanning electron microscopy and micro-computer tomography showed that 3-D scaffolds had completely interconnected porosity, uniform distribution of the glass particles, and a controlled and repetitive architecture. Surface properties were also assessed, showing that the incorporation of glass particles increased both the roughness and the hydrophilicity of the scaffolds. Mechanical tests indicated that compression strength is dependent on the scaffold geometry and the presence of glass. Preliminary cell response was studied with primary mesenchymal stem cells (MSC) and revealed that CaP glass improved cell adhesion. Overall, the results showed the suitability of the technique/materials combination to develop 3-D porous scaffolds and their initial biocompatibility, both being valuable characteristics for tissue engineering applications.

Keywords: Rapid prototyping, Scaffold, Polylactic acid, Biodegradable, Composite

Navarro, M., Engel, E., Planell, J. A., Amaral, I., Barbosa, M., Ginebra, M. P., (2008). Surface characterization and cell response of a PLA/CaP glass biodegradable composite material Journal of Biomedical Materials Research - Part A 85A, (2), 477-486

Bioabsorbable materials are of great interest for bone regeneration applications, since they are able to degrade gradually as new tissue is formed. In this work, a fully biodegradable composite material containing polylactic acid (PLA) and calcium phosphate (CaP) soluble glass particles has been characterized in terms of surface properties and cell response. Cell cultures were performed in direct contact with the materials and also with their extracts, and were evaluated using the MTT assay, alkaline phosphatase activity, and osteocalcin measurements. The CaP glass and PLA were used as reference materials. No significant differences were observed in cell proliferation with the extracts containing the degradation by-products of the three materials studied. A relation between the materials wettability and the material-cell interactions at the initial stages of contact was observed. The most hydrophilic material (CaP glass) presented the highest cell adhesion values as well as an earlier differentiation, followed by the PLA/glass material. The incorporation of glass particles into the PLA matrix increased surface roughness. SEM images showed that the heterogeneity of the composite material induced morphological changes in the cells cytoskeleton.

Keywords: Glass, Polylactic acid, Surface analysis, Cell culture, In vitro test

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