Light triggered interfacial damage self-healing of poly(p-phenylene benzobisoxazole) fiber composites

Protocol to construct biomimetic carbon fiber composites with improved interfacial strength

Weak interfacial strength restricts the mechanical properties of carbon fiber-reinforced composites. Here, inspired by natural hook-groove microstructure system (HGMS) of black kite (Milvus migrans), we detail the steps to construct a biomimetic HGMS based on dopamine-functionalized carbon fibers (CFs) and zinc oxide nanorods (ZnO NRs) using a two-step modification approach. We describe the fabrication of biomimetic carbon fiber composites using vacuum-assisted contact molding (VACM) and subsequent characterization using standard comprehensive mechanical tests techniques.

For complete details on the use and execution of this protocol, please refer to Wang et al. (2022).

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Investigation of natural HGMS and mechanical interlocking mechanism

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Steps to build a biomimetic HGMS based on functionalized CFs and ZnO NRs

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Vacuum-assisted contact molding used to fabricate biomimetic carbon fiber composites

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Guidance for mechanical performance test of the bioinspired CFRCs

Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.

Interfacial reinforced carbon fiber composites inspired by biological interlocking structure

Weak interfacial activity and poor wettability between fiber and matrix are known to be the two main factors that restrict the mechanical properties of carbon fiber-reinforced composites (CFRCs). Herein, inspired by high strength and toughness characteristics of wing feathers of Black Kite (Milvus migrans), natural hook-groove microstructure system (HGMS) and underlying mechanical interlocking mechanism were carefully investigated. Biomimetic HGMS based on dopamine-functionalized carbon fibers and ZnO nanorods were constructed successfully by a two-step modification method to enhance interfacial adhesion. Further, CFRCs featured with biomimetic HGMS were prepared by a vacuum-assisted contact molding method. Experimental results confirmed that flexural strength and interlaminar shear strength of the bioinspired CFRCs were effectively improved by 40.02 and 101.63%, respectively. The proposed bioinspired design strategy was proved to be flexible and effective and it was anticipated to provide a promising design approach and facile fabrication method for desirable CFRCs with excellent mechanical properties.

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Natural HGMS and mechanical interlocking mechanism were carefully investigated

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Biomimetic HGMS based on functionalized CFs and ZnO NRs was constructed

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Mechanical performance of the bioinspired CFRCs was enhanced significantly

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The interface adhesion between the CFs and EP was proved to be enhanced

Multi-Objective Optimisation of Curing Cycle of Thick Aramid Fibre/Epoxy Composite Laminates

Aramid fibre-reinforced epoxy composites (AF/EP) are promising materials in the aerospace, transportation, and civil fields owing to their high strength, high modulus, and light weight. Thick composite laminates are gradually being applied to large composite structures such as wind turbine blades. During curing, temperature overheating is a common problem in thick composites, which leads to matrix degradation, thermal residual stresses, and uneven curing. This paper proposes a signal-to-noise ratio (SNR) method to optimise the curing cycle of thick AF/EP laminates and reduce the overheating temperature. During curing, the temperature and strain evolution in a thick AF/EP laminate were monitored using fibre Bragg grating sensors. The effects of the curing factors on the overheating temperature of the thick AF/EP laminate were evaluated using the Taguchi method and predicted via the SNR method and analysis of variance. The results indicate that the dwelling temperature is the main factor affecting the overheating temperature. The optimal curing cycle involves an overheating temperature of 192.72 °C, which constitutes an error of 2.58% compared to the SNR method predictions. Additionally, in comparison to the initial curing cycle, the overshoot temperature in the optimised curing cycle was reduced by 58.48 °C, representing a reduction ratio of 23.28%.

Shape-Memory and Self-Healing Polymers Based on Dynamic Covalent Bonds and Dynamic Noncovalent Interactions: Synthesis, Mechanism, and Application

Shape-memory and self-healing polymers have been a hotspot of research in the field of smart polymers in the past decade. Under external stimulation, shape-memory and self-healing polymers can complete programed shape transformation, and they can spontaneously repair damage, thereby extending the life of the materials. In this review, we focus on the progress in polymers with shape-memory and self-healing properties in the past decade. The physical or chemical changes in the materials during the occurrence of shape memory as well as self-healing were analyzed based on the polymer molecular structure. We classified the polymers and discussed the preparation methods for shape-memory and self-healing polymers based on the dynamic interactions which can make the polymers exhibit self-healing properties including dynamic covalent bonds (DA reaction, disulfide exchange reaction, imine exchange reaction, alkoxyamine exchange reaction, and boronic acid ester exchange reaction) and dynamic noncovalent interactions (crystallization, hydrogen bonding, ionic interaction, metal coordination interaction, host-guest interactions, and hydrophobic interactions) and their corresponding triggering conditions. In addition, we discussed the advantages and the mechanism that the shape-memory property promotes self-healing in polymers, as well as the future trends in shape-memory and self-healing polymers.

Challenges and Opportunities of Self-Healing Polymers and Devices for Extreme and Hostile Environments

Engineering materials and devices can be damaged during their service life as a result of mechanical fatigue, punctures, electrical breakdown, and electrochemical corrosion. This damage can lead to unexpected failure during operation, which requires regular inspection, repair, and replacement of the products, resulting in additional energy consumption and cost. During operation in challenging, extreme, or harsh environments, such as those encountered in high or low temperature, nuclear, offshore, space, and deep mining environments, the robustness and stability of materials and devices are extremely important. Over recent decades, significant effort has been invested into improving the robustness and stability of materials through either structural design, the introduction of new chemistry, or improved manufacturing processes. Inspired by natural systems, the creation of self-healing materials has the potential to overcome these challenges and provide a route to achieve dynamic repair during service. Current research on self-healing polymers remains in its infancy, and self-healing behavior under harsh and extreme conditions is a particularly untapped area of research. Here, the self-healing mechanisms and performance of materials under a variety of harsh environments are discussed. An overview of polymer-based devices developed for a range of challenging environments is provided, along with areas for future research.

Facile immobilization of graphene nanosheets onto PBO fibers via MOF-mediated coagulation strategy: Multifunctional interface with self-healing and ultraviolet-resistance performance

The surface of poly (p-phenylene benzobisoxazole) (PBO) fibers with self-healing and ultraviolet (UV)-resistance performance play the key role in prolonging their service lifespan. Although great advances have been made in the single aspect of above two properties, integration of self-healing and anti-UV performance into the surface of PBO fiber is still a challenge. In this study, the coagulation strategy mediated by metal-organic framework (MOF) is proposed to construct the multifunctional surface of PBO fibers. The spindle-like iron (III)-based MOF (MIL-88B-NH₂) nanocrystals are firstly immobilized onto the surface of PBO-COOH through hydrothermal reaction, then serving as the medium layer to further immobilize sufficient graphene oxide (GO) nanosheets. Benefitting from the favorable near-infrared (NIR, 808 nm) photothermal conversion performance of GO nanolayers, the monofilament composite-PBO@Fe-MIL-88B-NH₂-GO-TPU (thermoplastic polyurethane) exhibited a stable and high self-healing efficiency (approximately 80%) within five cycle times. Meanwhile, the cooperative adsorption and shielding weaken effects of MOF-GO nanolayers enabled PBO fibers with excellent anti-UV properties that are superior to much reported literatures after 96 h aging time and eventually increased by 75% compared with untreated PBO fiber. In view of the varieties and multifunctionalities of MOFs and carbon nanomaterials, MOF-mediated coagulation strategy would provide guidance for preparing multifunctional composite materials.

Indocyanine Green Loaded Modified Mesoporous Silica Nanoparticles as an Effective Photothermal Nanoplatform

Photothermal therapy possesses great advantages for the treatment of drug-resistant tumors. Herein, Near Infrared (NIR)-triggered photothermal nanoparticles were developed through loading indocyanine green (ICG), a kind of NIR dye, into amino group-modified silica nanoparticles (SiO₂-NH₂ NPs). SiO₂-NH₂ NPs were prepared with immobilization of the amino groups into the framework of silica nanoparticles (SiO₂ NPs) by employing (3-aminopropyl)-triethoxysilane (APTES). Before and after the modification of the amino group, the particle sizes of SiO₂ NPs showed similar value, around 100 nm. ICG was further adsorbed into SiO₂-NH₂ NPs by electrostatic attraction to enable SiO₂-NH₂@ICG NPs as a kind of photothermal agent. The loading rate of ICG to SiO₂-NH₂ was greatly increased compared to unmodified SiO₂, and the stability of ICG was also improved. Moreover, the SiO₂-NH₂@ICG NPs exhibited efficient photothermal effects due to ICG transforming laser power into local heat through the connected ICG, when NIR laser irradiation turned on for a couple of minutes. Finally, the in vitro antitumor efficacy of SiO₂-NH₂@ICG NPs was investigated by recording cell proliferation rate and further chronicled the apoptotic morphology evidence by a Calcein-AM/PI fluorescent staining assay, indicating the efficient photothermal targeted therapy for the HepG2 tumor cells.

Hydrogen bonding derived self-healing polymer composites reinforced with amidation carbon fibers

Self-healing polymer materials (SHPM) have aroused great interests in recent years. Ideal SHPM should have not only simple operations, but also high elongations at break, tensile strain and self-healing properties at room temperature. Herein, the amidated carbon fibers (CFs) reinforced self-healing polymer composites were designed by hydrogen bonding interaction between functionalized CFs and hyperbranched polymers. The amidated CFs were prepared by transformation of hydroxyl to acylamino through a one-step amidation. By introducing amidated CFs, amidated CFs self-healing polymer composites (called AD-CF) exhibited many desirable characteristics compared to pure polymer composites, such as a better elasticity, lower healing temperatures, and higher self-healing efficiencies. The stress-strain test was selected to carefully study the self-healing property of the AD-CF. The observed same recovery condition, i.e. without any mechanical breakdown after the 10 sequential cycles of cutting and healing indicates no aging of the AD-CF. The ability of AD-CF to exhibit a soft state and rapid self-healing at room temperature makes it possible for much wider applications.

Facile Interface Design Strategy for Improving the Uvioresistant and Self-Healing Properties of Poly(p-phenylene benzobisoxazole) Fibers

Graphene-based coaxial hybrid fibers (CHFs) with a typical core-sheath structure have attracted extensive attention in recent years because of their potentially excellent mechanical performance. However, direct introduction of the micrometer-thick graphene stack structure on the extremely inert fiber surface with little negative effect has barely been reported so far and is still a great challenge. In the present work, a facile and cost-efficient dimensionally confined hydrothermal reduction, static adsorption, and thermal-assisted shrinkage sequential treatment strategy was developed to fabricate one-dimensional CHFs. The large-scale reduced graphene oxide-metal organic framework (RGO-UIO-66) hybrid layer and poly(p-phenylene benzobisoxazole) (PBO) fiber serve as the sheath part and core part, respectively, and the final product is denoted as PGU-CHFs. The experimental results confirmed that the prepared monofilament composite with thermoplastic polyurethane (PGU-CHF-TPU) exhibited an excellent and stable intrinsically self-healing efficiency (about 85%) over 5 cycles and an extraordinary uvioresistant performance (increased by 128%) compared to those of pristine PBO fibers after 288 h UV aging irradiation. Moreover, the anti-ultraviolet (UV) properties of PGU-CHFs at 96 h are basically at the optimum level among most of the reported literatures at present after comparison. The highly near-infrared photothermal conversion ability and stability of micrometer-thick RGO stack structure and the synergism of RGO-UIO-66 hybrid sheath layer including UV adsorption, shielding attenuation, and reflection are responsible for the satisfactorily interfacial self-healing efficiency and UV-resistance properties of PGU-CHFs, respectively. Considering the diversities and versatilities of RGO and MOFs, the proposed fabrication strategy will promisingly endow PBO fibers with great application potential in the other fields such as fiber-based sensors and smart fibers.

Plasmonic Ti3C2Tx MXene Enables Highly Efficient Photothermal Conversion for Healable and Transparent Wearable Device

Skin-mountable and transparent devices are highly desired for next-generation electronic applications but are susceptible to unexpected ruptures or undesired scratches, which can drastically reduce the device lifetime. Developing wearable and transparent materials with healable function that can recover their original functionality after mechanical damage under mild and noninvasive repairing operation is thus imperative. Herein, we demonstrate that the incorporation of ultrasmall quantities of plasmonic silver nanoparticle (AgNP)@MXene nanosheet hybrids to serve as photothermal fillers in waterborne elastic polyurethane enables high transparency as well as effective light-triggered healing capabilities for wearable composite coatings. The AgNP@MXene hybrid functions as a highly effective photon captor, energy transformer, and molecular heater due to the amalgamation of (1) ultrahigh photothermal conversion efficiency, high thermal conductivity, and structural properties of MXene, (2) the outstanding plasmonic effect of AgNPs, and (3) the synergistic effects from their hybrids. The resulting wearable composite coating with ultralow loading of plasmonic AgNP@MXene hybrids (0.08 wt % or 0.024 vol %) can produce a significant temperature increase of ∼111 ± 2.6 °C after the application of 600 mW cm^-2 light irradiation for 5 min, while maintaining a high optical transmittance of ∼83% at a thickness of ∼60 μm. This local temperature increase can rapidly heal the mechanical damage to the composite coating, with a healing efficiency above 97%.

Structural characterization of lignin and its carbohydrate complexes isolated from bamboo (Dendrocalamus sinicus)

Isolation of earth abundant biopolymer, Lignin, from Dendrocalamus sinicus and their structural properties were investigated to achieve its large-scale practical applications in value-added products. Two lignin fractions (MWL, DSL) were isolated with successive treatments of dioxane and dimethylsulfoxide (DMSO) from dewaxed and ball milled bamboo (D. sinicus) sample. The two-step treatments yielded 52.1% lignin based on the total lignin content in the dewaxed bamboo sample. Spectroscopy analyses indicated that the isolated bamboo lignin was a typical grass lignin, consisting of p-hydroxyphenyl, guaiacyl, and syringyl units. The major interunit linkages presented in the obtained bamboo lignin were β-O-4' aryl ether linkages, together with lower amounts of β-β', β-5', and β-1' linkages. The tricin was detected to be linked to lignin polymer through the β-O-4' linkage in the bamboo. In addition, phenyl glycoside and benzyl ether lignin-carbohydrate complexes (LCC) linkages were clearly detected in bamboo (D. sinicus), whereas the γ-ester LCC linkages were ambiguous due to the overlapping NMR signals with other substructures. The detailed structural properties of the obtained lignin fraction together with the light-weight will benefit efficient utilization of natural polymers as a possibly large-scale bio-based precursor for making polymeric materials, biochemicals, functional carbon and biofuels, and multifunctional polymer nanocomposites.

Biomass-derived nitrogen-doped carbon quantum dots: highly selective fluorescent probe for detecting Fe3+ ions and tetracyclines

Nitrogen-doped carbon quantum dots (N-CQDs) were successfully synthesized using rice residue and glycine as carbon and nitrogen sources by one-step hydrothermal method. High quantum yield (23.48%) originated from the effective combination of nitrogen with various functional groups (CO, NH, CN, COOH and COC). The N-CQDs showed a fluorescence with the wavelength varied from 420 to 500 nm and the maximum emission wavelength being at 440 nm. N-CQDs have been importantly applied as probe to detect Fe³⁺ and tetracycline (TCs) antibiotics with remarkable performance. Using the linear relationship between fluorescence intensity and Fe³⁺ concentration, the N-CQDs could be employed as a simple, efficient sensor for ultrasensitive Fe³⁺ detection ranging from 3.32 to 32.26 µM, with a limit of detection (LOD) of 0.7462 µM. The N-CQDs showed the applicability to detect TCs. The detection limits of tetracycline, terramycin and chlortetracycline were 0.2367, 0.3739 and 0.2791 µM, respectively. The results of TC by fluorescence method in real water samples were in good agreement with standard Ultraviolet-visible (UV-vis) method. The N-CQDs have various potential applications including sensitive and selective detection of Fe³⁺ and TCs, and cellular imaging with low cytotoxicity, good biocompatibility and high permeability.

Construction of Anti-Ultraviolet "Shielding Clothes" on Poly( p-phenylene benzobisoxazole) Fibers: Metal Organic Framework-Mediated Absorption Strategy

A metal-organic framework (MOF)-mediated adsorption strategy is first developed for improving the anti-ultraviolet (UV) properties of poly( p-phenylene benzobisoxazole) (PBO) fibers. In this work, UIO-66 was successfully anchored onto the surface of PBO fibers by one-step microwave-assisted heating method. The experimental results showed an obviously enhanced surface energy (91.1%), roughness (268.4%), interfacial shear strength (49.0%), and anti-UV properties (66.7%) compared to pristine PBO fibers. The anti-UV dye (tartrazine) was further immobilized onto the surface of PBO fibers via an adsorption strategy mediated by UIO-66. Interestingly, the PBO@tartrazine fibers demonstrated superior anti-UV performance (further up to 81.5%) compared to PBO@UIO-66 fibers. The extraordinary anti-UV properties of PBO@tartrazine fibers could be rationally ascribed to the synergistic effects of UIO-66 and tartrazine molecules. Considering the diversities and functionalities of MOFs and targeted materials, our work indicates that the MOF-mediated adsorption strategy would promisingly endow PBO fibers with other desired performance and applications such as solar-thermal transition and self-healing abilities.

Quick Heat Dissipation in Absorption-Dominated Microwave Shielding Properties of Flexible Poly(vinylidene fluoride)/Carbon Nanotube/Co Composite Films with Anisotropy-Shaped Co (Flowers or Chains)

The facile fabrication of thin flexible electromagnetic interference (EMI) shielding materials with fast heat dissipation for adaptable tuning in both civil and military applications is in urgent demand. In our work, the flexible poly(vinylidene fluoride) (PVDF)/carbon nanotube (CNT) composite films decorated with anisotropy-shaped Co in flowers or chains were prepared and studied. The results showed that by increasing the Co filler contents, the EC (electrical conductivity), TC (thermal conductivity), and EMI shielding properties of such PVDF/CNT/Co (flowers or chains) flexible films were significantly improved. In contrast, the PVDF/CNT/Co-chain flexible films exhibit higher performance with respect to the EC, TC, and EMI shielding properties. Total shielding of 35.3 and 32.2 dB were, respectively, obtained by the PVDF/CNT/6 wt % Co-chain with an EC of 2.28 S/cm and the PVDF/CNT/6 wt % Co-flower with an EC of 1.94 S/cm at a film thickness of 0.3 mm. Possibly owing to the conductive dissipation, interfacial polarization, magnetic loss, multiple reflections, and scattering of EM waves, such flexible composite films possessed a remarkable absorption-dominated EMI shielding behavior. These new composite films with enhanced TC are easily able to transform microwave energy into Joule heating systems, making themselves greatly potential for effective EMI shielding as well as rapid heat dissipation.

Low-Temperature Cross-Linkable Small Molecules for Fully Solution-Processed OLEDs

Cross-linkable hole-transporting, host, and electron-transporting materials with a new cross-linking group, uracil, are designed and synthesized. These compounds exhibited good solubility in common organic solvents and excellent solvent resistance after cross-linking at a low temperature of 120 °C. The OLED was fabricated by all-solution processing using cross-linkable synthetic compounds, except for the electrodes. This device exhibited a current efficiency of 39.2 cd A^-1 and a power efficiency of 15.3 lm W^-1 .

CuO Nanoparticles-Containing Highly Transparent and Superhydrophobic Coatings with Extremely Low Bacterial Adhesion and Excellent Bactericidal Property

Human health and industrial instruments have been suffering from bacterial colonization on the surface of materials for a long time. Recently, antibacterial coatings are regarded as the new strategy to resist bacterial pathogens. In this work, novel highly transparent and superhydrophobic coatings with extremely low bacterial adhesion and bactericidal performance were prepared by spray-coating hydrophobic silica sol and CuO nanoparticles. The coated glass showed high transmittance in 300-2500 nm with a maximum value of 96.6%. Compared with bare glass, its superhydrophobic characteristics resulted in a reduction in adhesion of bacteria ( Escherichia coli, E. coli) by up to 3.2 log cells/cm². Additionally, the live/dead staining test indicated that the as-prepared coating exhibited excellent bactericidal performance against E. coli. Moreover, the as-prepared coating could maintain their superhydrophobicity after the sand impact test. The proposed method to fabricate such coatings could be applied on various substrates. Therefore, this novel hybrid surface with the abilities to reduce bacterial adhesion and kill attached bacteria make it a promising candidate for biosensors, microfluidics, bio-optical devices, household facilities, lab-on-chips, and touchscreen devices.

Nanocomposite Au NP/TiO2 thin film in the efficient remediation of aqueous solutions contaminated with emerging micro-pollutants

The present communication specifically aims to synthesize novel nanocomposite material Au NPs/TiO₂ in a simple template process using the polyethylene glycol as filler media. The thin film of the nanocomposite material was characterized by the advanced analytical tools. The surface morphology was obtained by the scanning electron microscopic (SEM) and transmission electron microscopic (TEM) images of solids. Similarly, the surface topography and roughness of solid were obtained by the atomic force microscopic (AFM) image of thin film. X-ray diffraction (XRD) data enabled to confirm that the TiO₂ was predominantly present with its anatase phase. The specific surface area and pore size of the solid were obtained using the N₂ adsorption/desorption data. Nanocomposite Au NP/TiO₂ thin film was employed in the photocatalytic removal of sulfamethoxazole and triclosan from aqueous solutions using less harmful UV-A light (λ_max = 330 nm). Various physicochemical parametric studies enabled to deduce the mechanism involved in the degradation process. The degradation kinetics as a function of pH (pH 4.0-10.0) and micro-pollutant concentrations (0.5-15.0 mg/L) was extensively studied. The mineralization of these pollutants was obtained using the non-purgeable organic carbon (NPOC) data. The stability of thin film was assessed by the repeated operations, and presence of several co-existing ions simulates the studies to real matrix treatment. Further, the presence of scavengers enabled to pin point the radical-induced degradation of sulfamethoxazole and triclosan from aqueous solutions.

Effect of the Polyketone Aromatic Pendent Groups on the Electrical Conductivity of the Derived MWCNTs-Based Nanocomposites

Electrically conductive plastics with a stable electric response within a wide temperature range are promising substitutes of conventional inorganic conductive materials. This study examines the preparation of thermoplastic polyketones (PK30) functionalized by the Paal⁻Knorr process with phenyl (PEA), thiophene (TMA), and pyrene (PMA) pendent groups with the aim of optimizing the non-covalent functionalization of multiwalled carbon nanotubes (MWCNTs) through π⁻π interactions. Among all the aromatic functionalities grafted to the PK30 backbone, the extended aromatic nuclei of PMA were found to be particularly effective in preparing well exfoliated and undamaged MWCNTs dispersions with a well-defined conductive percolative network above the 2 wt % of loading and in freshly prepared nanocomposites as well. The efficient and superior π⁻π interactions between PK30PMA and MWCNTs consistently supported the formation of nanocomposites with a highly stable electrical response after thermal solicitations such as temperature annealing at the softening point, IR radiation exposure, as well as several heating/cooling cycles from room temperature to 75 °C.

Solvothermal synthesis, characterization and photocatalytic property of zirconium dioxide doped titanium dioxide spinous hollow microspheres with sunflower pollen as bio-templates

Zirconium dioxide (ZrO₂) doped titanium dioxide (TiO₂) spinous hollow microspheres were successfully prepared through a facile solvothermal method using sunflower pollen as bio-templates. The products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), N₂ adsorption-desorption isotherms and UV-Vis diffuse reflectance spectroscopy. It was found that the products have spinous microsphere morphology with an approximate diameter of 12 μm. The ZrO₂ doped TiO₂ hollow microspheres exhibited a higher photocatalytic activity in the degradation of Rhodamine B (RhB) in aqueous solutions under UV-light irradiation compared with TiO₂ hollow microspheres and ZrO₂-doped TiO₂ particles. In particular, the removal of RhB followed pseudo-first-order kinetics, and 96.3% of RhB was degraded in 60 min under UV-light irradiation when ZrO₂ doped TiO₂ spinous hollow microspheres were used as the photocatalysts. Neutral and alkaline conditions were found to favor over acidic conditions for the photocatalytic degradation of RhB. Furthermore, scavenging experiments indicated that photogenerated holes (h⁺) and radicals (OH and O^-₂) were the main reactive species in the photocatalytic process using ZrO₂ doped TiO₂ hollow microspheres as the catalysts under UV light irradiation.

Gold and gold-silver alloy nanoparticles enhance the myogenic differentiation of myoblasts through p38 MAPK signaling pathway and promote in vivo skeletal muscle regeneration

Under the severe trauma condition, the skeletal muscles regeneration process is inhibited by forming fibrous scar tissues. Understanding the interaction between bioactive nanomaterials and myoblasts perhaps has important effect on the enhanced skeletal muscle tissue regeneration. Herein, we investigate the effect of monodispersed gold and gold-silver nanoparticles (AuNPs and Au-AgNPs) on the proliferation, myogenic differentiation and associated molecular mechanism of myoblasts (C2C12), as well as the in vivo skeletal muscle tissue regeneration. Our results showed that AuNPs and Au-AgNPs could support myoblast attachment and proliferation with negligible cytotoxicity. Under various incubation conditions (normal and differentiation medium), AuNPs and Au-AuNPs significantly enhanced the myogenic differentiation of myoblasts by upregulating the expressions of myosin heavy chain (MHC) protein and myogenic genes (MyoD, MyoG and Tnnt-1). The further analysis demonstrated that AuNPs and Au-AgNPs could activate the p38α mitogen-activated protein kinase pathway (p38α MAPK) signaling pathway and enhance the myogenic differentiation. Additionally, the AuNPs and Au-AgNPs significantly promote the in vivo skeletal muscle regeneration in a tibialis anterior muscle defect model of rat. This study may provide a nanomaterials-based strategy to improve the skeletal muscle repair and regeneration.

Synthesis and evaluation of water soluble pH sensitive poly (vinyl alcohol)-doxorubicin conjugates

The accuracy of spatiotemporal control cargo delivery and release are primordial to enhance the therapeutic efficiency and decrease the undesirable effects, in this context a novel prodrug were developed based on biocompatible polyvinyl alcohol (PVA) substrate. PVA was conjugated to doxorubicin (PVA-DOX) via an acid-labile hydrazone linkage. PVA was first functionalized with acidic groups, then reacted with hydrazine hydrate to form an amide bond. The amine group of PVA hydrazide was linked to carbonyl group (C = O) of DOX to form a pH sensitive hydrazone bond. The molecular structure of the PVA-DOX was confirmed by FTIR, XPS, and ¹H-NMR analysis methods. The degree of grafting were evaluated by TGA and confirmed by XPS, which reveals the successful bond attachment of DOX to PVA. Our findings confirm pH dependent DOX release from PVA-DOX prodrug with faster release rate in acidic environment (pH 5.0, pH 6.0) and slower release rate in neutral pH environment (pH 7.4). Compared to the primary DOX, our synthesized PVA-DOX conjugates could exhibit a promising therapeutic effect, high biocompatibility and zero premature release. The results prove the successful synthesis of PVA-DOX conjugates with high efficiency.