Composite of elastin-based matrix and electrospun poly(L-lactic acid) fibers: A potential smart drug delivery system

Stimuli-responsive hydrogel matrices are inspiring manifold applications in controlled delivery of bioactive compounds. Elastin-derived polypeptides form hydrogel matrices that may release bioactive moieties as a function of local increase of active elastases, as it would occur in several processes like inflammation. In view of the development of a patch for healing wounds, recombinant elastin-based polypeptides were combined with a proteolysis-resistant scaffold, made of electrospun poly-L-lactic acid (PLLA) fibers. The results of this study demonstrated the compatibility of these two components. An efficient procedure to obtain a composite material retaining the main features of each component was established. The release of the elastin moiety was monitored by means of a simple protocol. Our data showed that electrospun PLLA can form a composite with fusion proteins bound to elastin-derived polypeptides. Therefore, our approach allows designing a therapeutic agent delivery platform to realize devices capable of responding and interacting with biological systems at the molecular level

Effect of oxide nanoparticles on thermal and mechanical properties of electrospun separators for lithium-ion batteries

This study reports the fabrication and characterization of poly(ethylene oxide) (PEO) and poly(vinylidenefluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) nanofibrous separators for lithium-ion batteries loaded with different amounts of fumed-silica and tin oxide nanoparticles. Membrane morphological characterization (SEM, TEM) showed the presence of good-quality nanofibres containing nanoparticles. Thermal degradation and membrane mechanical properties were also investigated, and a remarkable effect of nanoparticle addition on membrane mechanical properties was found. In particular, PEO membranes were strengthened by the addition of metal oxide, whereas PVDF-CTFE membranes acquired ductility

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

Hierarchical fibrous structures for muscle-inspired soft-actuators:A review

Inspired by Nature, one of the most ambitious challenge in soft robotics is to design actuators capable of reaching performances comparable to the skeletal muscles. Considering the perfectly balanced features of natural muscular tissue in terms of linear contraction, force‐to‐weight ratio, scalability and morphology, scientists have been working for many years on mimicking this structure. Focusing on the biomimicry, this review investigates the state‐of‐the‐art of synthetic fibrous, muscle‐inspired actuators that, aiming to enhance their mechanical performances, are hierarchically designed from the nanoscale up to the macroscale. In particular, this review focuses on those hierarchical fibrous actuators that enhance their biomimicry employing a linear contraction strategy, closely resembling the skeletal muscles actuation system. The literature analysis shows that bioinspired artificial muscles, developed up to now, only in part comply with skeletal ones. The manipulation and control of the matter at the nanoscale allows to realize ordered structures, such as nanofibers, used as elemental actuators characterized by high strains but moderate force levels. Moreover, it can be foreseen that scaling up the nanostructured materials into micro‐ and macroscale hierarchical structures, it is possible to realize linear actuators characterized by suitable levels of force and displacement

Fast Coprecipitation of Calcium Phosphate Nanoparticles inside Gelatin Nanofibers by Tricoaxial Electrospinning

We present an effective method for fabricating electrospun gelatin nanofibers containing well-dispersed inorganic nanoparticles. The new method encompasses the use of a special triaxial needle where mixing calcium and phosphate aqueous solutions in an intermediate needle yield calcium phosphate (CaP) nanoparticles that immediately after precipitation are dragged by the outer polymeric solution and incorporated directly in the electrospinning jet, before nanofiber formation. Gelatin electrospun mats containing different amounts of CaP nanoparticles were prepared and characterized by SEM, TEM, TGA, and stress-strain measurements. The results demonstrate that CaP particles having diameter of few tens of nanometers were successfully introduced in the gelatin nanofibers during the electrospinning process and that they were well dispersed throughout the fiber length. In addition, the use of the special triaxial needle enabled modulating the CaP amount in the nanofibers

Organogel Coupled with Microstructured Electrospun Polymeric Nonwovens for the Effective Cleaning of Sensitive Surfaces

Hydrogels and organogels are widely used as cleaning materials, especially when a controlled solvent release is necessary to prevent substrate damage. This situation is often encountered in the personal care and electronic components fields and represents a challenge in restoration, where the removal of a thin layer of aged varnish from a painting may compromise the integrity of the painting itself. There is an urgent need for new and effective cleaning materials capable of controlling and limiting the use of solvents, achieving at the same time high cleaning efficacy. In this paper, new sandwich-like composites that fully address these requirements are developed by using an organogel (poly(3-hydroxybutyrate) + \u3b3-valerolactone) in the core and two external layers of electrospun nonwovens made of continuous submicrometric fibers produced by electrospinning (either poly(vinyl alcohol) or polyamide 6,6). The new composite materials exhibit an extremely efficient cleaning action that results in the complete elimination of the varnish layer with a minimal amount of solvent adsorbed by the painting layer after the treatment. This demonstrates that the combined materials exert a superficial action that is of utmost importance to safeguard the painting. Moreover, we found that the electrospun nonwoven layers act as mechanically reinforcement components, greatly improving the bending resistance of organogels and their handling. The characterization of these innovative cleaning materials allowed us to propose a mechanism to explain their action: electrospun fibers play the leading role by slowing down the diffusion of the solvent and by conferring to the entire composite a microstructured rough superficial morphology, enabling to achieve outstanding cleaning performance

A New Type of Thermoalkalophilic Hydrolase of Paucimonas lemoignei with High Specificity for Amorphous Polyesters of Short Chain-length Hydroxyalkanoic Acids

A novel type of hydrolase was purified from culture fluid of Paucimonas (formerly Pseudomonas) lemoignei. Biochemical characterization revealed an unusual substrate specificity of the purified enzyme for amorphous poly((R)-3-hydroxyalkanoates) (PHA) such as native granules of natural poly((R)-3-hydroxybutyrate) (PHB) or poly((R)-3-hydroxyvalerate) (PHV), artificial cholate-coated granules of natural PHB or PHV, atactic poly((R,S)-3-hydroxybutyrate), and oligomers of (R)-3-hydroxybutyrate (3HB) with six or more 3HB units. The enzyme has the unique property to recognize the physical state of the polymeric substrate by discrimination between amorphous PHA (good substrate) and denatured, partially crystalline PHA (no substrate). The pentamers of 3HB or 3HV were identified as the main products of enzymatic hydrolysis of native PHB or PHV, respectively. No activity was found with any denatured PHA, oligomers of (R)-3HB with five or less 3HB units, poly(6-hydroxyhexanoate), substrates of lipases such as tributyrin or triolein, substrates for amidases/nitrilases, DNA, RNA, casein, N-alpha-benzoyl-l-arginine-4-nitranilide, or starch. The purified enzyme (M(r) 36,209) was remarkably stable and active at high temperature (60 degrees C), high pH (up to 12.0), low ionic strength (distilled water), and in solvents (e.g. n-propyl alcohol). The depolymerase contained no essential SH groups or essential disulfide bridges and was insensitive to high concentrations of ionic (SDS) and nonionic (Triton and Tween) detergents. Characterization of the cloned structural gene (phaZ7) and the DNA-deduced amino acid sequence revealed no homologies to any PHB depolymerase or any other sequence of data banks except for a short sequence related to the active site serine of serine hydrolases. A classification of the enzyme into a new family (family 9) of carboxyesterases (Arpigny, J. L., and Jaeger, K.-E. (1999) Biochem. J. 343, 177-183) is suggested

Self-sensing composite material based on piezoelectric nanofibers

Recently, efforts have been made to manufacture self-sensing smart composites by integrating piezoelectric sensors with laminates. However, the interleaving of pressure sensors, such as piezoelectric polymeric films, dramatically reduces the impact resistance of the hosting laminates, and consequently, delamination can occur. This study aimed to fabricate a self-sensing composite material by embedding piezoelectric nanofibers of poly(vinylidenefluoride-trifluoroethylene) (PVDF-TrFE) in a polymeric elastic matrix and carbon black-based electrodes to detect a piezoelectric signal. The mechanical and electrical properties of the self-sensing laminate were maintained after 106 fatigue test cycles. By appropriately tuning the parameters of the acquisition circuit, the sensor could measure not only impulsive loads but also low-frequency loads as low as 0.5 Hz. A piezoelectric model with lumped parameters for the polarization process and piezoelectric response of the nanofibers is proposed and validated by experimental results. As a proof of the model, the piezoelectric nanofiber sensors were embedded in a prosthetic carbon fiber sole, and the piezoelectric signal response closely followed the ground reaction force with a sensitivity of 0.14 mV/N

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

Biofabrication of bundles of poly(lactic acid)-collagen blends mimicking the fascicles of the human Achille tendon

Electrospinning is a promising technique for the production of scaffolds aimed at the regeneration of soft tissues. The aim of this work was to develop electrospun bundles mimicking the architecture and mechanical properties of the fascicles of the human Achille tendon. Two different blends of poly(L-lactic acid) (PLLA) and collagen (Coll) were tested, PLLA/Coll-75/25 and PLLA/Coll-50/50, and compared with bundles of pure PLLA. First, a complete physico-chemical characterization was performed on non-woven mats made of randomly arranged fibers. The presence of collagen in the fibers was assessed by thermogravimetric analysis, differential scanning calorimetry and water contact angle measurements. The collagen release in phosphate buffer solution (PBS) was evaluated for 14 days: results showed that collagen loss was about 50% for PLLA/Coll-75/25 and 70% for PLLA/Coll-50/50. In the bundles, the individual fibers had a diameter of 0.48 ±0.14 μm (PLLA), 0.31 ±0.09 μm (PLLA/Coll-75/25), 0.33 ±0.08 μm (PLLA/Coll-50/50), whereas bundle diameter was in the range 300-500 μm for all samples. Monotonic tensile tests were performed to measure the mechanical properties of PLLA bundles (as-spun) and of PLLA/Coll-75/25 and PLLA/Coll-50/50 bundles (as-spun, and after 48 h, 7 days and 14 days in PBS). The most promising material was the PLLA/Coll-75/25 blend with a Young modulus of 98.6 ±12.4 MPa (as-spun) and 205.1 ±73.0 MPa (after 14 days in PBS). Its failure stress was 14.2 ±0.7 MPa (as-spun) and 6.8 ±0.6 MPa (after 14 days in PBS). Pure PLLA withstood slightly lower stress than the PLLA/Coll-75/25 while PLLA/Coll-50/50 had a brittle behavior. Human-derived tenocytes were used for cellular tests. A good cell adhesion and viability after 14 day culture was observed. This study has therefore demonstrated the feasibility of fabricating electrospun bundles with multiscale structure and mechanical properties similar to the human tendon