Dicarboxylic acid-epoxy vitrimers: Influence of off-stoichiometric acid content on cure reactions and thermo-mechanical properties

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Electroresponsive Silk-Based Biohybrid Composites for Electrochemically Controlled Growth Factor Delivery

Stimuli-responsive materials are very attractive candidates for on-demand drug delivery applications. Precise control over therapeutic agents in a local area is particularly enticing to regulate the biological repair process and promote tissue regeneration. Macromolecular therapeutics are difficult to embed for delivery, and achieving controlled release over long-term periods, which is required for tissue repair and regeneration, is challenging. Biohybrid composites incorporating natural biopolymers and electroconductive/active moieties are emerging as functional materials to be used as coatings, implants or scaffolds in regenerative medicine. Here, we report the development of electroresponsive biohybrid composites based on Bombyx mori silkworm fibroin and reduced graphene oxide that are electrostatically loaded with a high-molecular-weight therapeutic (i.e., 26 kDa nerve growth factor-β (NGF-β)). NGF-β-loaded composite films were shown to control the release of the drug over a 10-day period in a pulsatile fashion upon the on/off application of an electrical stimulus. The results shown here pave the way for personalized and biologically responsive scaffolds, coatings and implantable devices to be used in neural tissue engineering applications, and could be translated to other electrically sensitive tissues as well

Electrical modification of aligned electrospun silk fibroin via interpenetrating polymer network of PEDOT:PSS for peripheral nerve regeneration.

Introduction: Over 1 million people worldwide suffer from trauma and peripheral nerve injury (PNI). Electrical stimulation (ES) is a method for peripheral nerve regeneration and nerve conduits are another [2]. ES can be used in therapeutic purposes for the relief of nerve pain, and it can also activate neurite outgrowth of neuronal cells in vitro [3,4]. Therefore, the integration of ES with an electrically conductive nerve conduit may accomplish the regeneration of fully functional nerves post trauma effectively. Here, we describe the development of electroactive composites of silk fibroin (SF) and poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS) as interpenetrating polymer networks (IPNs) of sub-micron fibres as novel peripheral nerve tissue scaffolds. Methods: Materials composed of non-woven mats of sub-micron fibres were fabricated based on double layers of electrospinning SF in formic acid (FA) and calcium chloride (CaCl2). The base layer of electrospun material was composed of randomly aligned fibres, whereas the top layer was aligned fibres, with thicknesses of 100 and 10 µm, respectively. The electrospun SF materials were treated with 80% ethanol (EtOH) to induce β-sheet formation. Next, the EtOH-treated fibres were soaked in a solution of EDOT monomer, PSS and an initiator for 3 days. The concentration ratio between EDOT and PSS (α) was varied from 1.3 to 3.3, to form interpenetrating polymer networks (IPNs). The physical and mechanical properties of these materials were characterized by scanning electron microscopy (SEM), hard X-ray photoelectron microscopy (HAXPES), and tensile testing. Finally, the optimal conditions of PEDOT:PSS modified fibres were coated with laminin, their cytotoxicity and biocompatibility with the neuron-like cell line (NG108-15) were tested. Cell viability, metabolic activity, DNA concentration, and neurite extension length were ascertained for 7 days. Results: The fibre diameter of electrospun materials was 190 ± 50 nm in both layers and no significant difference was observed after treatment with EtOH or chemical modification with PEDOT:PSS. The PEDOT:PSS modified fibres were turned dark blue. Moreover, HAXPES results revealed that there was a significantly higher atomic percentage of Sulphur (S) in the IPNs compared to the unmodified SF fibres. The stain at break and toughness of IPN materials were significantly decreased when α = 2.8 and 3.3. Additionally, there was no toxicity from IPN materials in the conditions of α = 2.3, 2.8, and 3.3. Cell metabolic activity and DNA concentration of NG108-15 cultured on SF and IPN materials were steadily increased from day 1 to day 7. Discussion & conclusion: The sub-micron aligned SF fibre has quite similar diameter to the neurite. These fibres are fragile in the dry state but flexible when hydrated due to plasticization of the SF by water. HAXPES and cytotoxicity results suggest that the electroactive SF:PEDOT:PSS IPNs are biocompatible. Moreover, the electroactive fibres can support neural cell proliferation and also neurite outgrowth when coated with laminin. The electrical conductivity of the fibres and its relation to external electrical stimulation regimes for enhanced neurite extension lengths will be studied in depth in the future

Property and Shape Modulation of Carbon Fibers Using Lasers

An exciting challenge is to create unduloid-reinforcing fibers with tailored dimensions to produce synthetic composites with improved toughness and increased ductility. Continuous carbon fibers, the state-of-the-art reinforcement for structural composites, were modified via controlled laser irradiation to result in expanded outwardly tapered regions, as well as fibers with Q-tip (cotton-bud) end shapes. A pulsed laser treatment was used to introduce damage at the single carbon fiber level, creating expanded regions at predetermined points along the lengths of continuous carbon fibers, while maintaining much of their stiffness. The range of produced shapes was quantified and correlated to single fiber tensile properties. Mapped Raman spectroscopy was used to elucidate the local compositional and structural changes. Irradiation conditions were adjusted to create a swollen weakened region, such that fiber failure occurred in the laser treated region producing two fiber ends with outwardly tapered ends. Loading the tapered fibers allows for viscoelastic energy dissipation during fiber pull-out by enhanced friction as the fibers plough through a matrix. In these tapered fibers, diameters were locally increased up to 53%, forming outward taper angles of up to 1.8°. The tensile strength and strain to failure of the modified fibers were significantly reduced, by 75% and 55%, respectively, ensuring localization of the break in the expanded region; however, the fiber stiffness was only reduced by 17%. Using harsher irradiation conditions, carbon fibers were completely cut, resulting in cotton-bud fiber end shapes. Single fiber pull-out tests performed using these fibers revealed a 6.75-fold increase in work of pull-out compared to pristine carbon fibers. Controlled laser irradiation is a route to modify the shape of continuous carbon fibers along their lengths, as well as to cut them into controlled lengths leaving tapered or cotton-bud shapes

The effect of terminal globular domains on the response of recombinant mini-spidroins to fiber spinning triggers

From Springer Nature via Jisc Publications RouterHistory: received 2020-02-04, accepted 2020-06-11, registration 2020-06-15, pub-electronic 2020-06-30, online 2020-06-30, collection 2020-12Publication status: PublishedFunder: Defence Science and Technology Laboratory; doi: http://dx.doi.org/10.13039/100010418; Grant(s): DSTLX1000101893, DSTLX1000101893, DSTLX1000101893, DSTLX1000101893, DSTLX1000101893Funder: Engineering and Physical Sciences Research Council; doi: http://dx.doi.org/10.13039/501100000266; Grant(s): EP/L014904/1Funder: Biotechnology and Biological Sciences Research Council; doi: http://dx.doi.org/10.13039/501100000268; Grant(s): BB/M017702/1, BB/M017702/1, BB/M017702/1Abstract: Spider silk spidroins consist of long repetitive protein strands, flanked by globular terminal domains. The globular domains are often omitted in recombinant spidroins, but are thought to be essential for the spiders’ natural spinning process. Mimicking this spinning process could be an essential step towards producing strong synthetic spider silk. Here we describe the production of a range of mini-spidroins with both terminal domains, and characterize their response to a number of biomimetic spinning triggers. Our results suggest that mini-spidroins which are able to form protein micelles due to the addition of both terminal domains exhibit shear-thinning, a property which native spidroins also show. Furthermore, our data also suggest that a pH drop alone is insufficient to trigger assembly in a wet-spinning process, and must be combined with salting-out for effective fiber formation. With these insights, we applied these assembly triggers for relatively biomimetic wet spinning. This work adds to the foundation of literature for developing improved biomimetic spinning techniques, which ought to result in synthetic silk that more closely approximates the unique properties of native spider silk

Design and fabrication of recombinant reflectin-based multilayer reflectors: bio-design engineering and photoisomerism induced wavelength modulation

From Springer Nature via Jisc Publications RouterHistory: received 2020-10-03, accepted 2021-06-18, registration 2021-07-07, pub-electronic 2021-07-16, online 2021-07-16, collection 2021-12Publication status: PublishedFunder: Defence Science and Technology Laboratory; doi: http://dx.doi.org/10.13039/100010418Funder: Engineering and Physical Sciences Research Council; doi: http://dx.doi.org/10.13039/501100000266; Grant(s): EP/S01778X/1, EP/S01778X/1, EP/S01778X/1Abstract: The remarkable camouflage capabilities of cephalopods have inspired many to develop dynamic optical materials which exploit certain design principles and/or material properties from cephalopod dermal cells. Here, the angle-dependent optical properties of various single-layer reflectin thin-films on Si wafers are characterized within the UV–Vis–NIR regions. Following this, initial efforts to design, fabricate, and optically characterize a bio-inspired reflectin-based multilayer reflector is described, which was found to conserve the optical properties of single layer films but exhibit reduced angle-dependent visible reflectivity. Finally, we report the integration of phytochrome visible light-induced isomerism into reflectin-based films, which was found to subtly modulate reflectin thin-film reflectivity

Enhancing the hydrophilicity and cell attachment of 3D printed PCL/graphene scaffolds for bone tissue engineering

© 2016 by the author. Scaffolds are physical substrates for cell attachment, proliferation, and differentiation, ultimately leading to the regeneration of tissues. They must be designed according to specific biomechanical requirements, i.e., certain standards in terms of mechanical properties, surface characteristics, porosity, degradability, and biocompatibility. The optimal design of a scaffold for a specific tissue strongly depends on both materials and manufacturing processes, as well as surface treatment. Polymeric scaffolds reinforced with electro-active particles could play a key role in tissue engineering by modulating cell proliferation and differentiation. This paper investigates the use of an extrusion-based additive manufacturing system to produce poly(ε-caprolactone) (PCL)/pristine graphene scaffolds for bone tissue applications and the influence of chemical surface modification on their biological behaviour. Scaffolds with the same architecture but different concentrations of pristine graphene were evaluated from surface property and biological points of view. Results show that the addition of pristine graphene had a positive impact on cell viability and proliferation, and that surface modification leads to improved cell response