Editorial: Electrospinning of Bioinspired Materials and Structures for Bioengineering and Advanced Biomedical Applications

The Research Topic “Electrospinning of Bioinspired Materials and Structures for Bioengineering and Advanced Biomedical Applications” includes submissions that relate to the “Biomaterials” and “Bionics and Biomimetics” sections of Frontiers in Bioengineering and Biotechnology. The collection aims to provide an overview of how electrospinning, inspired by nature, can reproduce the hierarchical structure and biomechanical properties of biological tissues, ranging from the nanoscale to the macroscale. The development of such innovative nanofibrous structures requires the improvement of both functionalization and biofabrication strategies, to enhance the scaffold bioactivity and to drive cells in the regeneration of the extracellular matrix (ECM) of the target tissues of interest. Recent technological advances have given rise to the availability of intelligent and smart biomaterials for the regeneration of innovative procedures for manufacturing nanometric structures, and methods for assembling multiscale hierarchical structures. Furthermore, imaging has improved considerably in the last few years, allowing multimodal imaging with nanometric resolution

Plasma-substrate interaction in a dual frequency APPJ

To achieve a uniform argon plasma in an atmospheric pressure jet, we explored the possibility of using dual-frequency excitation in a coaxial dielectric barrier discharge device. Two separate ring-shaped electrodes outside an alumina tube generate the two frequencies. The upstream electrode is powered at low frequency (LF, 17 kHz ), while the downstream electrode is powered at radio frequency (RF, 27 MHz ). To assess the interaction with the substrate, a grounded electrode, covered by a glass substrate, is placed 5 mm from the outlet of the alumina tube. We analyze the device with a fluid model and compare the results with experimental electrical and optical characterization. As the plasma is ignited by the LF, positive streamers develop from the LF electrode and reach the substrate in a few hundred nanoseconds. At this stage, the substrate is charged and a surface discharge propagates on the glass; however, no additional ionization occurs in the jet. As RF is added, the plasma is sustained by modulation in the Ω regime. At the same time, the LF polarization propagates through the plasma, influencing the sheaths on the facing dielectric walls. When the voltage drop in the sheaths exceeds a threshold level, an additional γ mode originates due to the secondary electrons emitted by the surfaces, leading to an increase in power dissipation. This coexistence of the two regimes is observed in the simulation, and it is validated experimentally by time-resolved photoemission measurements. As a result, the dual-frequency plasma exhibits a filamentary structure similar to that of an LF-driven jet. However, RF excitation caused diffused pre-ionization of the gas, which reduced the charge density gradients, resulting in wider microdischarge channels and a lower average electric field. Streamers propagation is therefore limited, while an ion flow to the substrate is maintained and controlled by the LF polarization

Statistical properties and morphology of a 2D gel network at the air/water interface

We report here a detailed characterization of the steps leading to the formation of a bidimensional gel at the air/water interface. The 2D geometry is peculiar in that it allows a continuous and controlled variation of the density of the system over a wide range. The evolution of the statistical properties of the structured network, as a function of the externally controlled density, is related to the corresponding evolution of the mechanical properties. We identified three steps in the gel formation: a first step occurs in the incubation time, in which the individual nm-sized gold nanoparticle aggregate to form quasi 1D structures of typical length of a few microns. The second step occurs in the first stages of the compression, with the growth of the branched structure, finally yielding to the onset of the infinite percolative cluster, which is related to the building of the mechanical elastic modulus. The final step identifies with the homogenization and regularization of the distribution of holes sizes, which relates to the further increase of the elastic modulus upon compression. We speculate that this study should help in the formulation of gels with desired characteristics, such as increased mechanical strength, or increased mobilit

Inmunolocalización temporal y espacial de osteopontina en la reparación de defectos óseos ortopédicos tratados con matriz ósea desmineralizada

Osteopontin (OPN) is the most abundant non-collagen protein in the bone matrix, where it fulfils the function of cellular adhesion and biomineralization. In the present work, the authors report the temporal and spatial localization of OPN during the repair of experimental orthopaedic bone defects treated with demineralized bone matrix (DBM) processed by the authors. 30 rabbits were used, which were given an orthopaedic bone defect of critical size in one of the radiuses, which was filled with DBM. The rabbits were euthanized in groups of 5 individuals at days 7, 15, 21, 30, 60 and 150. Histological cuts were immunomarked to establish the spatial and temporal immunomarcation of OPN. The histological cuts were observed with an optic microscope with which histological images were captured and analysed with the ImageJ software. The image analysis allowed the authors to establish the optic density (OD) and the integrated optic density (IOD). The data was analysed with the ANOVA and Fischer LSD tests. At day 7, the presence of OPN was observed only in the DBM particles, where the OD was 0.08 and the IOD was 1.64; at day 15, OPN marked different sites of collagen condensations and cells contained in the interior of the matrix. In this period the OD was 0.096 and the IOD, 9.26. At days 21 and 30, the OPN immunosignalled osteocytes, osteoblasts, osteoclasts and hypertrophic chondrocytes in the bone trabeculae adjacent   to the ossification zones. At day 21 the OD was 0.17 and IOD 6.22. At day 30, the OD was 0.14 and the IOD 2.52. At days 60 and 150, OPN was evenly distributed in the new bone matrix with an OD: 0.10 and IOD: 0.48, and OD: 0.35 and IOD: 3.80, respectively. The OD and IOD showed significant differences (p<=0.05) between days 7, 15, 21 and 30; and there was no difference at days 60 and 150 (p=0.05). OPN was found in the DBM particles: it increased the optic densities at day 15 and it diminished at day 60, after which it increased the OD and IOD again until day 150. It was established that the OPN immunoexpressed during the repair process in indifferentiated cells, osteoprogenitor chondrocytes and osteoblasts. The variation of OD and IOD allowed the authors to establish that the greatest degree of immunoexpression of OPN was at day 15 after repair initiated. On the other hand, the increase registered between days 60 and 150 post treatment was due to the biomineralization of the bone matrix.La osteopontina (OPN) es la proteína no colágena que más abunda en la matriz ósea, donde cumple funciones de adhesión celular y biomineralización. En el presente trabajo se informa la localización temporal y espacial de la OPN durante la reparación de defectos óseosortopédicos tratados con matriz ósea desmineralizada (MOD). Se emplearon 30 conejos a los que se les practicó un defecto óseo ortopédico de tamaño crítico en uno de sus radios. Los defectos se rellenaron con MOD obtenida según protocolo previamente informado. Los conejosfueron sacrificados en grupos de 5 a los 7, 15, 21, 30, 120 y 150 días de los cuales se recuperaron los defectos para identificar las estructuras histológicas y establecer la inmunomarcación espacial y temporal de OPN. Se realizaron cortes histológicos de los defectos que se tiñeron con hematoxilina y eosina (HE) e inmunomarcaron según técnicainmunohistológica. Los cortes inmunomarcados se observaron en un microscopio óptico de donde se capturaron imágenes histológicas a  20X para analizarlas con el software ImageJ y establecer la densidad óptica (DO) y densidad óptica integrada (DOI). Los datos se analizaron con un test ANOVOA y LSD Fisher. A los 7 días se observó la presencia de OPN solo en las partículas de MOD donde la DO: 0,109 y DOI: 3587,043; a los 15 días OPN marcaba distintos sitios de condensaciones colágenas y células en su interior, en este período DO fue 0,096 y la DOI: 10593,08. A los 21 y 30 días OPN señalaba trabéculas óseas, osteocitos, osteoblastos, osteoclastos y condrocitos hipertróficos inmediatos a las zonas de osificación, la DO fue 0,134 y DOI 14.639,7. A los 120 y 156 días OPN se encontraba uniformemente distribuida por la matriz del hueso nuevo con una DO: 0,0104; DOI: 4160,96 y DO: 0,081 y DOI 8878,9 respectivamente. Las DO y DOI mostraron diferencias significativas (p<=0,05) entre los 7, 15, 21 y 30 días y no existió diferencia a los días 120 y 150 días (p=0,05). OPN se halló presente en las partículas de MOD e incrementó las densidades ópticas a los 15, 21 y 30 días como producto del metabolismo celular posibilitando la adhesión celular y luego interviniendo en la biomineralización

Apoptosis and cell proliferation in porcine placental vascularization

The placenta is a highly vascularized organ, indispensable tothe transfer of nutrients to the growing fetuses. During gestation, there exists an expansion of the placental vascular network through active angiogenesis. The aim of this research was to study cell proliferation and apoptosis through high resolution light microscopy (HRLM) and transmission electron microscopy (TEM) ultrastructure, immunohistochemistry for Ki67and caspase-3, determination of placental vascular area,and TUNEL assay. Crossbred sows placental tissues from approximately 30 ± 2(n =5), 40 ± 2(n =5), 60 ± 2 (n =5), 80 ± 2(n =5), 90 ± 2(n =5) and 114 ± 2(n =5) days of gestation were used. The evaluation of cell proliferation showed the highest%Ki67 values on days 30 ± 2 and 80 ± 2 of pregnancy. Caspase-3 expressed the highest value on day 30 ± 2, while the highest apoptotic indexes were found on days30 ± 2 and 90 ± 2. The placental vascular area was higher on day 80 ± 2 of pregnancy. According to our results, an active vascular cell remodeling by a caspase-3 dependent apoptosis seems to be present in early pregnancy. The increase in the vascular area on day 80 ± 2 would be the result of the intense vascular cell proliferation detected with Ki67. Further studies are needed to understand the complex processes of angiogenesis, cell proliferation and apoptosis that interact in the placenta during porcine gestation.Facultad de Ciencias Veterinaria

MORPHOLOGICALLY BIO-INSPIRED HIERARCHICAL NYLON 6,6 ELECTROSPUN STRUCTURES FOR SOFT-ROBOTICS APPLICATIONS

The last decades have seen an increasing attention on a new, ground-breaking field, soft-robotics [1]. Soft-robotics tries to overcome the limits of classical rigid robots, developing bioinspired structures with compliant and soft materials. Skeletal muscle is a biological, hierarchically arranged fibrous structure (Fig A), suitable to inspire innovative soft actuators. The possibility to mimic muscles and soft tissues has been demonstrated through the use of the electrospinning technique [2]. The aim of the present study was to develop and characterize innovative muscle-inspired, hierarchically arranged electrospun structures made of Nylon 6,6 for soft-robotics applications. In order to mimic skeletal muscle myofibrils [3], mats of aligned Nylon 6,6 nanofibers were electrospun on a rotating drum collector. To reproduce skeletal muscle fibers and fascicles morphology [3], the mats were cut in stripes and wrapped up on the drum, producing bundles of axially aligned nanofibers. The bundles were then pulled out from the drum, obtaining ring-shaped bundles. To mimic a whole skeletal muscle with its epimysium membrane [3], 2-levels hierarchical structure was developed (Fig B). Several bundles were aligned and packed together using a nanofibrous sheath produced through an innovative electrospinning setup [4]. Finally, in order to mimic also the skeletal muscle fascicles and perimysium [3], a 3-levels hierarchical structure was obtained by grouping together three 2-levels hierarchical structures, produced as previously described, with an additional electrospun sheath (Fig C). A morphological investigation of the different electrospun structures was carried out with scanning electron microscopy (SEM) and high-resolution x-ray tomography (XCT). The alignment of the nanofibers of the electrospun sheaths and the internal bundles, was quantified with a previously validated methodology [5]. The bundles and the 2-levels hierarchical structures were also mechanically characterized with a monotonic tensile test. The level of alignment of the nanofibers in the sheaths has proved to be tuneable by modifying the electrospinning parameters. The electrospun sheaths are also capable to tighten the structures wrapped inside, reducing their cross-sectional area and improving the apparent mechanical strength and stiffness. The high-resolution imaging confirmed that the mean diameters of the different hierarchical structures were comparable to the corresponding structures of biological skeletal muscle [3]. The directionality analysis on both bundles and sheaths nanofibers showed comparable levels of alignment with corresponding skeletal muscles fibrous tissues [3]. The mechanical test on the structures revealed a non-linear behaviour typical of soft tissue. The 2- levels hierarchical structures showed mechanical properties roughly proportional to the number of single bundles incorporated (with a possible underestimation of the ultimate strength, due to a stress concentration at the grips). In conclusion, this innovative electrospinning approach to produce hierarchically-arranged structures will be suitable to develop muscle-inspired assemblies. We will explore the possibility of incorporating adequate contracting ability so as to build soft actuators

Patrón de glicosilación glandular y vascular de la placenta porcina

Since porcine placenta is epitheliochorial and non invasive, maternal and fetal blood flows are separated by six tissue layers. Therefore, the interchange of nutrients between mother and fetuses results indispensable for the success of pregnancy. The glycoconjugates participate in several biological processes, nevertheless their involvement in the materno-fetal interchange that takes place in the placenta is still unclear. The objective was to investigate the glycosilated residues of endometrial glands and blood vessels in placentas of different gestational periods. Crossbred swines from slaughterhouses located in Río Cuarto, Argentina, were used. Samples from placentas of: 28 (n=5), 55 (n=5), 60 (n=5), 70 (n=5) and 114 days of pregnancy (n=5) were obtained. Lectin-histochemistry using fluorescein isothiocyanate-conjugated lectins were employed. Sialic acid residues were detected with low intensity in blood vessels and uterine glands. Variable intensity was found for galactosilated residues, with the lowest intensity for ß-gal (1,3) galNAc residues of PNA binding. However, blood vessels staining was higher than that of glands. The highest staining for glucose and mannose was found in vessels with Con-A lectin, and in glands with VFA. The present results indicate that changes in the glycosilation pattern of glandular and vascular epithelia are related with placental remodeling along gestation. Moreover, the saccharide residues found in vascular and glandular secretions would be part of the nutritional substances provided to the embryos/fetuses during pregnancy.Fil: Sanchis, Eva Gabriela. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento de Patología Animal. Área de Microscopia Electrónica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cristofolini, Andrea Lorena. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento de Patología Animal. Área de Microscopia Electrónica; Argentina. Universidad Nacional de Rio Cuarto. Facultad de Agronomia y Veterinaria. Instituto de Ciencias Veterinarias. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Instituto de Ciencias Veterinarias.; ArgentinaFil: Chanique, Analia Maria Luisa. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento de Patología Animal; ArgentinaFil: Merkis, Cecilia Inés. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento de Patología Animal. Área de Microscopia Electrónica; Argentin

Patrón de glicosilación glandular y vascular de la placenta porcina

Since porcine placenta is epitheliochorial and non invasive, maternal and fetal blood flows are separated by six tissue layers. Therefore, the interchange of nutrients between mother and fetuses results indispensable for the success of pregnancy. The glycoconjugates participate in several biological processes, nevertheless their involvement in the materno-fetal interchange that takes place in the placenta is still unclear. The objective was to investigate the glycosilated residues of endometrial glands and blood vessels in placentas of different gestational periods. Crossbred swines from slaughterhouses located in Río Cuarto, Argentina, were used. Samples from placentas of: 28 (n=5), 55 (n=5), 60 (n=5), 70 (n=5) and 114 days of pregnancy (n=5) were obtained. Lectin-histochemistry using fluorescein isothiocyanate-conjugated lectins were employed. Sialic acid residues were detected with low intensity in blood vessels and uterine glands. Variable intensity was found for galactosilated residues, with the lowest intensity for ß-gal (1,3) galNAc residues of PNA binding. However, blood vessels staining was higher than that of glands. The highest staining for glucose and mannose was found in vessels with Con-A lectin, and in glands with VFA. The present results indicate that changes in the glycosilation pattern of glandular and vascular epithelia are related with placental remodeling along gestation. Moreover, the saccharide residues found in vascular and glandular secretions would be part of the nutritional substances provided to the embryos/fetuses during pregnancy.Fil: Sanchis, Eva Gabriela. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento de Patología Animal. Área de Microscopia Electrónica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cristofolini, Andrea Lorena. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento de Patología Animal. Área de Microscopia Electrónica; Argentina. Universidad Nacional de Rio Cuarto. Facultad de Agronomia y Veterinaria. Instituto de Ciencias Veterinarias. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Instituto de Ciencias Veterinarias.; ArgentinaFil: Chanique, Analia Maria Luisa. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento de Patología Animal; ArgentinaFil: Merkis, Cecilia Inés. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento de Patología Animal. Área de Microscopia Electrónica; Argentin