3D-Printed Phenylboronic Acid-Bearing Hydrogels for Glucose-Triggered Drug Release.

Diabetes is a major health concern that the next-generation of on-demand insulin releasing implants may overcome via personalized therapy. Therein, 3D-printed phenylboronic acid-containing implants with on-demand glucose-triggered drug release abilities are produced using high resolution stereolithography technology. To that end, the methacrylation of phenylboronic acid is targeted following a two-step reaction. The resulting photocurable phenylboronic acid derivative is accordingly incorporated within bioinert polyhydroxyethyl methacrylate-based hydrogels at varying loadings. The end result is a sub-centimeter scaled 3D-printed bioinert implant that can be remotely activated with 1,2-diols and 1,3-diols such as glucose for on-demand drug administration such as insulin. As a proof of concept, varying glucose concentration from hypoglycemic to hyperglycemic levels readily allow the release of pinacol, i.e., a 1,2-diol-containing model molecule, at respectively low and high rates. In addition, the results demonstrated that adjusting the geometry and size of the 3D-printed part is a simple and suitable method for tailoring the release behavior and dosage.

Investigation into Influence of Tensile Properties When Varying Print Settings of 3D-Printed Polylactic Acid Parts: Numerical Model and Validation.

Material Extrusion (MEX), particularly Fused Filament Fabrication (FFF), is the most widespread among the additive manufacturing (AM) technologies. To further its development, understanding the influence of the various printing parameters on the manufactured parts is required. The effects of varying the infill percentage, the number of layers of the top and bottom surfaces and the number of layers of the side surfaces on the tensile properties of the printed parts were studied by using a full factorial design. The tensile test results allowed a direct comparison of each of the three parameters' influence on the tensile properties of the parts to be conducted. Yield strength appears to be the most affected by the number of layers of the top and bottom surfaces, which has twice the impact of the number of layers of the side surfaces, which is already twice as impactful as the infill percentage. Young's modulus is the most influenced by the number of layers of the top and bottom surfaces, then by the infill percentage and finally by the number of layers of the side surfaces. Two mathematical models were considered in this work. The first one was a polynomial model, which allowed the yield strength to be calculated as a function of the three parameters mentioned previously. The coefficients of this model were obtained by performing tensile tests on nine groups of printed samples, each with different printing parameters. Each group consisted of three samples. A second simplified model was devised, replacing the numbers of layers on the side and top/bottom surfaces with their fractions of the cross-section surface area of the specimen. This model provided results with a better correlation with the experimental results. Further tests inside and outside the parameter ranges initially chosen for the model were performed. The experimental results aligned well with the predictions and made it possible to assess the accuracy of the model, indicating the latter to be sufficient and reliable. The accuracy of the model was assessed through the R2 value obtained, R2 = 92.47%. This was improved to R2 = 97.32% when discarding material infill as an input parameter.

Highly Crystalline Poly(heptazine imide)-Based Carbonaceous Anodes for Ultralong Lifespan and Low-Temperature Sodium-Ion Batteries.

Carbon nitrides with layered structures and scalable syntheses have emerged as potential anode choices for the commercialization of sodium-ion batteries. However, the low crystallinity of materials synthesized through traditional thermal condensation leads to insufficient conductivity and poor cycling stability, which significantly hamper their practical applications. Herein, a facile salt-covering method was proposed for the synthesis of highly ordered crystalline C3N4-based all-carbon nanocomposites. The sealing environment created by this strategy leads to the formation of poly(heptazine imide) (PHI), the crystalline phase of C3N4, with extended π-conjugation and a fully condensed nanosheet structure. Meanwhile, theoretical calculations reveal the high crystallinity of C3N4 significantly reduces the energy barrier for electron transition and enables the generation of efficient charge transfer channels at the heterogeneous interface between carbon and C3N4. Accordingly, such nanocomposites present ultrastable cycling performances over 5000 cycles, with a high reversible capacity of 245.1 mAh g-1 at 2 A g-1 delivered. More importantly, they also exhibit an outstanding low-temperature capacity of 196.6 mAh g-1 at -20 °C. This work offers opportunities for the energy storage use of C3N4 and provides some clues for developing long-life and high-capacity anodes operated under extreme conditions.

Ionically Modified Gelatin Hydrogels Maintain Murine Myogenic Cell Viability and Fusion Capacity.

For tissue engineering of skeletal muscles, there is a need for biomaterials which do not only allow cell attachment, proliferation, and differentiation, but also support the physiological conditions of the tissue. Next to the chemical nature and structure of the biomaterial, its response to the application of biophysical stimuli, such as mechanical deformation or application of electrical pulses, can impact in vitro tissue culture. In this study, gelatin methacryloyl (GelMA) is modified with hydrophilic 2-acryloxyethyltrimethylammonium chloride (AETA) and 3-sulfopropyl acrylate potassium (SPA) ionic comonomers to obtain a piezoionic hydrogel. Rheology, mass swelling, gel fraction, and mechanical characteristics are determined. The piezoionic properties of the SPA and AETA-modified GelMA are confirmed by a significant increase in ionic conductivity and an electrical response as a function of mechanical stress. Murine myoblasts display a viability of >95% after 1 week on the piezoionic hydrogels, confirming their biocompatibility. The GelMA modifications do not influence the fusion capacity of the seeded myoblasts or myotube width after myotube formation. These results describe a novel functionalization providing new possibilities to exploit piezo-effects in the tissue engineering field.

A dynamic passive thermoregulation fabric using metallic microparticles.

Maintaining comfort using photonic thermal management textiles has a large potential to decrease the energy cost for heating and cooling in residential and office buildings. We propose a thermoregulating fabric using metallic microparticles, which provides a dynamic and passive control of the infrared transmission, by adapting to the ambient temperature and humidity. The fabric is composed of tailored metal microparticles and a stimuli-responsive polymer actuator matrix, in order to benefit from strong scattering effects to control the wideband transmission of thermal radiation and to provide a sharp, dynamic response. The detailed numerical design demonstrates a wide dynamic ambient setpoint temperature window of ∼8 °C, with the wearer staying comfortable in the range between 18 and 26 °C. Its compatibility for large-scale manufacturing, with a safe and strong thermoregulating performance indicates a vital energy-saving potential and paves the way to a more sustainable society.

Interfacial Compatibilization into PLA/Mg Composites for Improved In Vitro Bioactivity and Stem Cell Adhesion.

The present work highlights the crucial role of the interfacial compatibilization on the design of polylactic acid (PLA)/Magnesium (Mg) composites for bone regeneration applications. In this regard, an amphiphilic poly(ethylene oxide-b-L,L-lactide) diblock copolymer with predefined composition was synthesised and used as a new interface to provide physical interactions between the metallic filler and the biopolymer matrix. This strategy allowed (i) overcoming the PLA/Mg interfacial adhesion weakness and (ii) modulating the composite hydrophilicity, bioactivity and biological behaviour. First, a full study of the influence of the copolymer incorporation on the morphological, wettability, thermal, thermo-mechanical and mechanical properties of PLA/Mg was investigated. Subsequently, the bioactivity was assessed during an in vitro degradation in simulated body fluid (SBF). Finally, biological studies with stem cells were carried out. The results showed an increase of the interfacial adhesion by the formation of a new interphase between the hydrophobic PLA matrix and the hydrophilic Mg filler. This interface stabilization was confirmed by a decrease in the damping factor (tanδ) following the copolymer addition. The latter also proves the beneficial effect of the composite hydrophilicity by selective surface localization of the hydrophilic PEO leading to a significant increase in the protein adsorption. Furthermore, hydroxyapatite was formed in bulk after 8 weeks of immersion in the SBF, suggesting that the bioactivity will be noticeably improved by the addition of the diblock copolymer. This ceramic could react as a natural bonding junction between the designed implant and the fractured bone during osteoregeneration. On the other hand, a slight decrease of the composite mechanical performances was noted.

Tough and Three-Dimensional-Printable Poly(2-methoxyethyl acrylate)-Silica Composite Elastomer with Antiplatelet Adhesion Property.

Poly(2-methoxyethyl acrylate) (PMEA) has attracted attention as a biocompatible polymer that is used as an antithrombotic coating agent for medical devices, such as during artificial heart and lung fabrication. However, PMEA is a viscous liquid polymer with low Tg, and its physical strength is poor even if a cross-linker is used, so it is difficult to make tough and freestanding objects from it. Here, we design and fabricate a biocompatible elastomer made of tough, self-supporting PMEA-silica composites. The toughness of the composite elastomer increases as a function of silica particle filling, and its stress at break is improved from 0.3 to 6.7 MPa. The fracture energy of the composite elastomer with 39.5 vol % silica particles is up to 15 times higher than that of the cross-linked PMEA with no silica particles and the material demonstrates stress-strain behavior that is similar to that of biological soft tissue, which exhibits nonlinear elasticity. In addition, the composite elastomer shows the potential to be an antithrombotic property, while the results of the platelet adhesion test of the composite elastomer show that the number of adhered platelets is not significantly affected by the silica addition. As the composite elastomer can be rapidly three-dimensional-printed into complex geometries with high-resolution features, it is expected to contribute to the development of medical devices from readily available materials.

Advances in intrinsic self-healing polyurethanes and related composites.

Fascinating and challenging, the development of repairable materials with long-lasting, sustainable and high-performance properties is a key-parameter to provide new advanced materials. To date, the concept of self-healing includes capsule-based healing systems, vascular healing systems, and intrinsic healing systems. Polyurethanes have emerged as a promising class of polymeric materials in this context due to their ease of synthesis and their outstanding properties. This review thereby focuses on the current research and developments in intrinsic self-healing polyurethanes and related composites. The chronological development of such advanced materials as well as the different strategies employed to confer living-like healing properties are discussed. Particular attention will be paid on chemical reactions utilized for self-healing purposes. Potential applications, challenges and future prospects in self-healing polyurethane fields are also provided.

Mechanistic Insights on Spontaneous Moisture-Driven Healing of Urea-Based Polyurethanes.

Self-healing polymeric materials that can spontaneously repair in a perpetual manner are highly appealing to address safety and restoration issues in different key applications. Usually built from reversible moieties that require to be activated using, for example, temperature, light, or pH changes, most of these self-healing materials rely on energy-demanding processes and/or external interventions to promote self-healing. In this work, we propose to exploit rapid dynamic exchanges between urea-based moieties and moisture as an alternative to promote local and spontaneous healing responses to damage using atmospheric moisture as an external stimulus. Non-hygroscopic urea-based polyurethanes with repetitive moisture-induced healing abilities at different degrees of humidity were thus designed through coupling reactions with non-hygroscopic polypropylene glycol and urea moieties. As supported by density functional theory (DFT) calculations coupled to local FTIR experimental studies, we furthermore established that the healing mechanism is ultimately related to the formation of water-urea clusters. Obviously, this work represents a platform for designing more advanced spontaneous self-healing materials beyond the present study, which hold promise for use in a wide range of technological applications.

Optical stereolithography of antifouling zwitterionic hydrogels.

This paper reports the rapid 3D printing of tough (toughness, UT, up to 141.6 kJ m-3), highly solvated (φwater∼ 60 v/o), and antifouling hybrid hydrogels for potential uses in biomedical, smart materials, and sensor applications, using a zwitterionic photochemistry compatible with stereolithography (SLA). A Design of Experiments (DOE) framework was used for systematically investigating the multivariate photochemistry of SLA generally and, specifically, to determine an aqueous SLA system with an additional zwitterionic acrylate, which significantly increases the gelation rate, and the resilience of the resulting hybrid hydrogels relative to an equivalent non-ionic polyacrylamide hydrogel. Specifically, the resulting zwitterionic hybrid hydrogels (Z-gels) can be tuned over a large range of ultimate strains, ca. 0.5 < γult < 5.0, and elastic moduli, ca. 10 < E < 1000 kPa, while also demonstrating a high resilience under cyclic tensile loading. Importantly, unlike traditional chemistry, increasing the elastic modulus of the Z-gels does not necessarily reduce the ultimate strain. Moreover, the Z-gels can be rapidly printed using a desktop commercial SLA 3D printer, with relatively low photoirradiation dosages of visible light (135 to 675 mJ cm-2 per 50-100 µm layer). Compared with the counterpart polyacrylamide hydrogels, the Z-gels have greater antifouling properties and exhibit 58.2% less absorption of bovine serum albumin.