Healing Performance Research Articles

Characterizing the Self‐Healing Asphalt Materials: A Neutron Imaging Study

Given the significant role of asphaltic pavement in surface transportation systems, even minor enhancements in asphalt materials hold the potential for cost savings and reduced environmental impacts. The healing properties of asphalt have drawn interest for sustainability, yet much remains unknown about the causes and influencing factors. To leverage self‐healing for extending pavement life, understanding the mechanisms and conditions that stimulate microcrack healing is essential. This study aims to investigate the dynamic progress of microcrack closure in asphalt mastics. The time‐series evolution of crack closure led by self‐healing is tracked by neutron computed tomography, with image processing facilitating volumetric analysis over a 7 h period. The study examines the healing process in mastic samples with three different sand filler contents (10, 20, and 30%). Results show that for all the investigated samples, the healing rate declines exponentially over time, with 100% recovery not achieved after 7 h at room temperature. Filler content‐influenced healing speed and 20% sand demonstrate the best performance. Meanwhile, the healing performance varies within the 10% and 30% groups, depending on initial crack size. Additionally, the study finds that initial crack size influences healing behavior in the samples.

High‐performance self‐healing epoxy by microencapsulated epoxy‐amine chemistry II: Performance of the system

AbstractThe self‐healing epoxy based on microencapsulated epoxy‐amine chemistry is a system with great potential for practical applications. Herein, microcapsules respectively containing epoxy and polyetheramine were fabricated using a microencapsulation technique via integrating electrospraying and interfacial polymerization (ES‐IP) and self‐healing epoxy based on the dual microcapsules were systematically investigated regarding the microcapsule dispersion, healing performance, failure mode, and mechanical properties. Microcapsules with different sizes were conveniently prepared by adjusting the injection rate. The microcapsules, regardless of the size, can be well dispersed in the epoxy matrix. The effects of the microcapsule size and concentration on the healing performance were studied. While full healing can be obtained for microcapsule >100 μm, high healing efficiency of about 90% and 70% can be achieved for microcapsules in 50 ~ 100 μm and ~ 50 μm, respectively. The healing performance decreases with the decreased microcapsule concentration. However, healing efficiency >70% can still be obtained when 5.0 wt% microcapsule of 50 ~ 100 μm were adopted. Mixed failure modes including adhesive failure, cohesive failure, and matrix failure, were observed, due to the good performance of the selected healant system. While the incorporated microcapsules, especially the small ones, evidently toughens the matrix, they deteriorate the tensile properties of the formulated self‐healing material.

High‐performance self‐healing epoxy by microencapsulated epoxy‐amine chemistry I: Properties of the adopted healant system

AbstractThe adopted healant has a significant impact on the final healing performance of self‐healing materials. Herein, the healant system, bisphenol‐F diglycidyl ether (BFDGE) and polytheramine JEFFAMINE T403, which possesses the capability of fully healing at room temperature (RT) for epoxy, was investigated in depth. The healing potential of this healant system and its healing benchmark after microencapsulation were systematically studied using a manual injecting method. It shows that the maximum and benchmark healing efficiencies respectively reach about 210% and 170% at RT for 48 h. The robustness of the cured healant was checked by studying the mechanical properties of BFDGE/T403. It verified that the tensile properties of the healant are stable after RT curing for 48 h. The curing degree of the healant was further characterized using differential scanning calorimetry by measuring the residual exotherm. It reaches 90% when the maximum healing performance is achieved and stabilizes at 95% thereafter. The results from the manually healing test, the tensile test, and the DSC test, are consistent with each other, which validate the robustness of BFDGE/T403 as healant for self‐healing epoxies.

Injectable Salecan/hyaluronic acid-based hydrogels with antibacterial, rapid self-healing, pH-responsive and controllable drug release capability for infected wound repair

Designing materials for wound dressings with superior therapeutic benefits, self-healing and injectable characteristics is important in clinical practice. Herein, a new self-healing injectable hydrogel was prepared via thermal treatment and dynamic Schiff base reaction by mixing oxidized hyaluronic acid (OHA) and hydrazided Salecan (Sal-ADH). The versatility of the wound dressing was confirmed by studying the inherent rheological properties, high swelling rate, sustained-release behavior of the drug, pH/hyaluronidase-dependent biodegradation, in vitro antimicrobial as well as in vivo wound healing performance. The presence of the antimicrobial drug polyhexamethylene biguanide (PHMB) conferred good antimicrobial properties to the Sal-ADH/OHA/PHMB (SOP) hydrogel, which could effectively prevent wound infection (the width of the inhibition circle of SOP-0.20 hydrogel was 4.97 mm, 5.93 mm for Staphylococcus aureus and Escherichia coli, respectively). The findings suggested that SOP hydrogel exhibited remarkable self-healing and injectability properties, as well as excellent hemostasis and biocompatibility. In vivo experiments indicated that the application of SOP hydrogels would obviously accelerate wound healing and attenuate the inflammatory response while increasing collagen deposition and angiogenesis. Altogether, antibacterial SOP hydrogels with moderate mechanical properties, pH-responsive release, excellent injectability, exceptional self-healing ability and anti-inflammatory effects could expand potential applications of injectable hydrogels in the biomedical field.

Amoxicillin-laded sodium alginate/cellulose nanocrystals/polyvinyl alcohol composite nanonetwork sponges with enhanced wound healing and antibacterial performance

Wound healing is a complex process and reuires a long repair process. Poor healing effect is normally a challenge for wound healing. Designing sponge dressings with drug-assisted therapy, good breathability, and multiple functional structures effectively promotes wound healing. In this work, a flexible amoxicillin-laded (AMX) sodium alginate (SA)/cellulose nanocrystals (CNCs)/ polyvinyl alcoho (PVA) (SA/CNCs/PVA-AMX, SCP-AMX) wound dressing was designed and built with an excellent porous structure, suitable porosity, and anti-bacterial properties for promoting wound tissue reparation. The porous structure of the wound dressing was fabricated by freeze-thawing cyclic and freeze-dried molding process. This wound dressing exhibited a 3D porous structure for soft-tissue-engineering application, including high porosity (84.2%), swelling ratio (1513%), tensile strength (1.79 MPA), and flexibility. With the inhibition zones of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) being 1.96 and4.58 cm, respectively, this wound dressing demonstrated good antibacterial activity against E. coli and S. aureus. More importantly, wound healing assay in vivo indicates that SCP-AMX could inhibit wound infection, promote collagen deposition, reduce inflammation, and accelerate granulation tissue and wound healing. Thus, the reported wounding dressings present excellent biocompatibility, high antibacterial activities, and excellent biosafety with great potential in wound healing applications.

Design of self-healing and anticorrosion epoxy coating with active multiple hydrogen bonds based on grafted polyetheramine

The healing of epoxy coatings in damaged areas significantly influences their service life and protection quality. Intrinsic self-healing coatings, which enable multiple healing cycles without the need for additional functional carriers, have emerged as a promising coating technology. Nevertheless, the cross-linked structure of thermoset epoxy coating system restricts the large-scale migration of molecular chains, posing a significant challenge to achieve intrinsic healing of resin without compromising its mechanical properties. In this study, we report a design scheme for epoxy coating with intrinsic self-healing properties based on active multiple hydrogen bonds. Grafting aminobenzothiazole at the end of polyetheramine D230 chain, the grafted polyetheramine (GD230) was synthesized and served as the auxiliary curing agent, whose accurate molecular structure has been confirmed by different characterizations. The self-healing coating with reversible dynamics network based on hydrogen bonds was prepared by crosslinking through epoxy resin and mixed curing agent of polyetheramine D230 and GD230. Various measurements have been adopted to evaluate the self healing and anticorrosion performance. Results showed that the functional coating with a ratio of 8:2 for D230 to GD230 has satisfied both performances on the steel substrate. After immersion in 3 wt% NaCl solution for 120 days, the impedance value of functional coating still remains about 1010 Ω cm2. After the coating was scratched and immersion for 96 h, the impedance value of functional coating increased by about two orders of magnitude compared to that in blank coating. Mechanical testing and theoretical calculations were used to support dynamic crosslinking model to reveal the self-healing mechanism.

Amine functionalized maleimide grafted MWCNT–CFRP hybrid composites interfacial/matrix healing and mechanical performance through thermally reversible cycloaddition

AbstractRestoration of the structural integrity of damaged CFRP composite through thermally reversible Diels–Alder bonds with the exact interfacial healing between matrix/fiber is extremely desirable for manufacturing of high‐performance self‐healing laminates. This article demonstrates the fabrication of amine‐functionalized maleimide‐grafted MWCNT (with different weight ratios 0.5 wt%, 1.0 wt%, and 1.5 wt%) reinforced thermally reversible self‐healing CFRP composite. The morphological changes, functional elements, elemental groups, and thermal degradation of functionalized‐MWCNTs were characterized by FESEM/HR‐TEM, FTIR, XRD, and TG‐DTA analysis. The results demonstrated that CFRP reinforced with silane/maleimide grafted MWCNT enhanced the dispersion, exhibited 82% healing efficiency and improvement in flexural strength‐67.11%, tensile strength‐64.75% concerning pure‐CFRP. FE‐SEM fractography of composites indicated that nanotube pullout was predominant failure‐criteria in CFRP‐pristine‐MWCNTs whereas strong interfacial adhesion dominated in CFRP‐maleimide‐MWCNTs. The purpose of this article is to investigate matrix/fiber/nanofillers interface healing properties of CFRP‐composite before and after damage. Furthermore, it is intended to reform structural integrity and examines average healing efficiency.Highlights Amine‐functionalized maleimide‐grafted MWCNT, CFRP composite fabrication. Characterized, morphological changes functional elements thermal degradation. Improvement in healing efficiency (82%), flexural strength‐(67.11%). The enthalpy of 0.5 wt% MWCNTBm enhanced to 10.91 J/g. Fractographic examinations show extensive intralaminar/interlaminar deformation.

Multiscale study on fatigue healing performance and molecular healing behavior of self-healing SBS modified bitumen

Self-healing polymer modified bitumen based on dynamic chemical bonds is a potential approach to improve the durability of bitumen pavement and save fossil energy. Herein, a novel self-healing SBS modified bitumen on the basis of dynamic disulfide bonds and hydrogen bonds was prepared. Firstly, an aliphatic disulfide (A-ALD) with disulfide bonds and hydrogen bonds was synthesized. Then A-ALD/SBS modified bitumen (A-ALD/SMB) was prepared by blending A-ALD and SBS modified bitumen. The chemical structure and microstructure of A-ALD/SMB were evaluated. In addition, the self-healing performance of A-ALD/SMB at the macroscopic scale and the self-healing behavior at the molecular scale were investigated by a combination of fatigue healing test and molecular dynamics (MD) simulation. The chemical structure analysis showed the formation of disulfide bonds and hydrogen bonds in A-ALD, and A-ALD was successfully attached to the CC bonds in SBS. Fluorescent images revealed that a better network structure appeared in A-ALD/SMB and formed a two-phase continuous morphology. The optimal dosage of A-ALD in SBS modified bitumen was 0.6 %. The fatigue healing test results indicated that A-ALD markedly enhanced the self-healing ability of SBS modified bitumen, and prolonging resting time and raising healing temperature can increase the self-healing performance of A-ALD/SMB. When the damage degree, healing temperature, and resting time were 30 %, 30 °C, and 60 min, respectively, the healing rate of A-ALD/SMB was 98.5 %, which was 30.2 % higher than SMB. The MD simulation results showed that the A-ALD enhanced the molecular diffusion capacity of SBS modified bitumen, and crack healing time of A-ALD/SMB was earlier than that of SMB under the same conditions. When the healing temperature was 40 °C, the time for the A-ALD/SMB and SMB molecular chain segments to start contacting and healing was 27 ps and 49 ps, respectively, which was improved by 44.9 % for A-ALD/SMB compared to SMB. Furthermore, the self-healing behavior of A-ALD/SMB at the molecular scale was consistent with the self-healing performance at the macroscopic scale under different healing temperatures and damage degrees. This study provided a theoretical basis for exploring the self-healing mechanism of SBS modified bitumen.

Polyvinyl alcohol-chitosan based oleanolic acid nanofibers against bacterial infection: In vitro studies and in vivo evaluation by optical and laser Doppler imaging modalities

The present work focuses on the fabrication of polyvinyl alcohol-chitosan-loaded oleanolic acid-nanofibers (PVA-CS-OLA-NFs) for bacterial infection. The prepared PVA-CS-OLA-NFs were characterized for contact angle, SEM, AFM, XRD, FTIR, and TGA. The solid-state characterization and in vitro performance evaluation of nanofibers reveal consistent interconnection and diameters ranging from 102 ± 9.5 to 386 ± 11.6 nm. The nanofibers have a flat surface topography and exhibit efficient drug entrapment. Moreover, the in vitro release profile of PVA-CS-OLA-NFs was found to be 51.82 ± 1.49 % at 24 h. Furthermore, the hemocompatibility study showed that the developed PVA-CS-OLA-NFs are non-hemolytic to human blood. The PVA-CS-OLA-NFs demonstrate remarkable antibacterial capabilities, as evidenced by their MBC and MIC values, which range from 128 and 32 μg/mL, against the strains of S. aureus. The in-vivo fluorescence optical imaging showed the sustained PVA-CS-OLA-NFs release at the wound site infected with S. aureus for a longer duration of time. Moreover, the PVA-CS-OLA-NFs showed superior wound healing performance against S. aureus infected wounds compared to the marketed formulation. Further, the laser Doppler imaging system improved oxygen saturation, blood supply, and wound healing by providing real-time blood flow and oxygen saturation information.

Strong and Healable Elastomers with Photothermal-Stimulus Dynamic Nanonetworks Enabled by Subnano Ultrafine MoO3-x Nanowires.

One-dimensional nanomaterials have become one of the most available nanoreinforcing agents for developing next-generation high-performance functional self-healing composites owing to their unique structural characteristics and surface electron structure. However, nanoscale control, structural regulation, and crystal growth are still enormous challenges in the synthesis of specific one-dimensional nanomaterials. Here, oxygen-defective MoO3-x nanowires with abundant surface dynamic bonding were successfully synthesized as novel nanofillers and photothermal response agents combined with a polyurethane matrix to construct composite elastomers, thus achieving mechanically enhanced and self-healing properties. Benefiting from the surface plasmon resonance of the MoO3-x nanowires and interfacial multiple dynamic bonding interactions, the composite elastomers demonstrated strong mechanical performance (with a strength of 31.45 MPa and elongation of 1167.73%) and ultrafast photothermal toughness self-healing performance (20 s and an efficiency of 94.34%). The introduction of MoO3-x nanowires allows the construction of unique three-dimensional cross-linked nanonetworks that can move and regulate interfacial dynamic interactions under 808 nm infrared laser stimulation, resulting in controlled mechanical and healing performance. Therefore, such special elastomers with strong photothermal responses and mechanical properties are expected to be useful in next-generation biological antibacterial materials, wearable devices, and artificial muscles.

A polyurea capturing both high strength and rapid self-healing tailored for intelligent barrier anti-corrosion system

The long-term repair of organic coatings in underwater environments is hindered by microcracks and their poor healing performance. In this study, a high-strength and rapidly self-healing polyurea (PU3) coating that combines asymmetric dense stacking of supramolecular units with mismatched rigid and flexible polymer chains was developed. By exploiting the interaction between a 2D sheet-like Ti3C2TX MXene and finely tailored hydrogen-bonded structures of PU3, a smart biomimetic anticorrosion composite coating (PU3-1.0 wt% MXene) was produced. This coating achieved rapid (15 s), specific, and repeatable in situ repair underwater when exposed to near infrared laser light. Electrochemical tests confirmed its excellent anticorrosion capability.

Study on the Factors Affecting the Self-Healing Performance of Graphene-Modified Asphalt Based on Molecular Dynamics Simulation.

To comprehensively understand the impact of various environmental factors on the self-healing process of graphene-modified asphalt, this study employs molecular dynamics simulation methods to investigate the effects of aging degree (unaged, short-term aged, long-term aged), asphalt type (base asphalt, graphene-modified asphalt), healing temperature (20 °C, 25 °C, 30 °C), and damage degree (5 Å, 10 Å, 15 Å) on the self-healing performance of asphalt. The validity of the established asphalt molecular models was verified based on four physical quantities: density, radial distribution function analysis, glass transition temperature, and cohesive energy density. The simulated healing time for the asphalt crack model was set to 200 ps. The following conclusions were drawn based on the changes in density, mean square displacement, and diffusion coefficient during the simulated healing process under different influencing factors: Dehydrogenation and oxidation of asphalt molecules during the aging process hinder molecular migration within the asphalt crack model, resulting in poorer self-healing performance. As the service life increases, the decline in the healing performance of graphene-modified asphalt is slower than that of base asphalt, indicating that graphene-modified asphalt has stronger anti-aging properties. When the vacuum layer in the asphalt crack model is small, the changes in the diffusion coefficient are less pronounced. As the crack width increases, the influence of various factors on the diffusion coefficient of the asphalt crack model becomes more significant. When the crack width is large, the self-healing effect of asphalt is more dependent on these influencing factors. Damage degree and oxidative aging have a more significant impact on the healing ability of graphene-modified asphalt than healing temperature.

Self‐healing reversible network from furfuryl‐functionalized copoly(triazine‐r‐polypropylene glycol‐r‐polydimethylsiloxane)

AbstractNew shape‐memory networks composed of both reversible Diels–Alder covalent crosslinks and the hydrogen and π–π stacking bonds of triazine functional groups, with self‐healing properties as a result of the reversibility of these dynamic bonds were achieved from a furfuryl‐functionalized copoly(triazine‐r‐polypropylene glycol‐r‐polydimethylsiloxane), crosslinked with a maleimide end‐capped polycaprolactone and a long polycaprolactone‐based chain extender. The presence of multiple dynamic bonds, including the Diels–Alder and triazine‐derived π–π stacking and H‐bond interactions as well as the enhanced network mobility arising from polypropylene glycol, polydimethylsiloxane and polycaprolactone segments upon triggering the shape memory effect resulted in a material with high toughness (~200 MPa J−1) and efficient healing ability (with a recoveries of tensile strength and toughness after being cut and healed of 87% and 94%, respectively).Highlights Furfuryl dichlorotriazine was coupled with PPG and PDMS forming a copolymer. The copolymer was crosslinked with PCL‐dimaleimide and PCL‐difuran extender. Multiple dynamic bonds (Diels–Alder, π–π stacking and H‐bond) were present. The network showed high toughness and good healing performance.

Measurement on the fatigue-healing performance of SARAs fractions in bitumen and its characterization by molecular simulations

The objective of this research was to investigate the healing characteristics of bitumen through the assessment of fatigue-healing performance of SARAs fractions and its characterization at the molecular level with SARAs fractions as the intermediate. Firstly, the flow behaviors and fatigue-healing performance of fractions were characterized by rheometer. Then, the diffusion systems were constructed and the diffusion with preset cracks was carried out, the evaluation of which was identified by density distribution, relative concentration in crack region, mean square displacement and interaction effect. The results indicate that aromatics exhibit the closest similarity to original bitumen in flowing behavior, which also reflected in the healing performance. The healing performance of resins and asphaltenes are extremely limited while that of saturates was comparable to fluid. Molecular simulation was further supporting to investigate the healing process. A platform period was found in the healing period when the molecules would move to seek the lowest energy state which was considered as healing in the alternative perspective. During the period, heavy components were more difficult to traverse while weak interaction between light components would shorten the period and identify the lowest energy state more easily, thereby greatly affecting the healing performance of fractions. Furthermore, heavy components are analogous to anchor points, among which resins were more readily aggregated and asphaltenes were relatively dispersed, while light components diffuse flexibly within them. The diffusion has the potential to drive the movement of heavy components which also kept the capture of other components, ultimately resulting in the formation of a stable healing state. The outcome with a discernible interaction effect would be important theoretical significance for the refinement of bitumen of better healing performance and the potential to influence the development of rejuvenators.

The Production of Porous Asphalt Mixtures with Damping Noise Reduction and Self-Healing Properties through the Addition of Rubber Granules and Steel Wool Fibers.

Conventional asphalt roads are noisy. Currently, there are two main types of mainstream noise-reducing pavements: pore acoustic absorption and damping noise reduction. However, a single noise reduction method has limited noise reduction capability, and porous noise-reducing pavements have a shorter service life. Therefore, this paper aimed to improve the noise-damping performance of porous asphalt mixture by adding rubber granules and extending its service life using electromagnetic induction heating self-healing technology. Porosity and permeability coefficient test, Cantabro test, immersion Marshall stability test, freeze-thaw splitting test, a low-temperature three-point bending experiment, and Hamburg wheel-tracking test were conducted to investigate the pavement performance and water permeability coefficients of the mixtures. A tire drop test and the standing-wave tube method were conducted to explore their noise reduction performance. Induction heating installation was carried out to study the heating rate and healing performance. The results indicated that the road performance of the porous asphalt mixture tends to reduce with an increasing dosage of rubber granules. The road performance is not up to the required standard when the dosage of rubber granules reaches 3%. The mixture's performance of damping and noise tends to increase with the increase of rubber granule dosage. Asphalt mixtures with different rubber granule dosages have different noise absorption properties, and the mixture with 2% rubber granules has the best overall performance (a vibration attenuation coefficient of 7.752 and an average absorption factor of 0.457). The optimum healing temperature of the porous asphalt mixture containing rubber granules and steel wool fibers is 120 °C and the healing rate is 74.8% at a 2% rubber granule dosage. This paper provides valuable insights for improving the noise reduction performance and service life of porous asphalt pavements while meeting road performance standards.

Multifunctional nanofibrous scaffolds for enhancing full-thickness wound healing loaded with Bletilla striata polysaccharides

The considerable challenge of wound healing remains. In this study, we fabricated a novel multifunctional core-shell nanofibrous scaffold named EGF@BSP-CeO2/PLGA (EBCP), which is composed of Bletilla striata polysaccharide (BSP), Ceria nanozyme (CeO2) and epidermal growth factor (EGF) as the core and poly(lactic-co-glycolic acid) (PLGA) as the shell via an emulsion electrospinning technique. An increase in the BSP content within the scaffolds corresponded to improved wound healing performance. These scaffolds exhibited increased hydrophilicity and porosity and improved mechanical properties and anti-UV properties. EBCP exhibited sustained release, and the degradation rate was <4 % in PBS for 30 days. The superior biocompatibility was confirmed by the MTT assay, hemolysis, and H&E staining. In addition, the in vitro results revealed that, compared with the other groups, the EBCP group presented excellent antioxidant and antibacterial effects. More importantly, the in vivo results indicated that the wound closure rate of the EBCP group reached 94.0 % on day 10 in the presence of H2O2. The results demonstrated that EBCP could comprehensively regulate the wound microenvironment, possess hemostatic abilities, and significantly promote wound healing. In conclusion, the EBCP is promising for facilitating the treatment of infected wounds and represents a potential material for clinical applications.

In-vitro and in-vivo evaluation of angiogenic potential of a novel lithium chloride loaded silk fibroin / alginate 3D porous scaffold with antibacterial activity, for promoting diabetic wound healing

Healing diabetic ulcers with chronic inflammation is a major challenge for researchers and professionals, necessitating new strategies. To rapidly treat diabetic wounds in rat models, we have fabricated a composite scaffold composed of alginate (Alg) and silk fibroin (SF) as a wound dressing that is laden with molecules of lithium chloride (LC). The physicochemical, bioactivity, and biocompatibility properties of Alg-SF-LC scaffolds were investigated in contrast to those of Alg, SF, and Alg-SF ones. Afterward, full-thickness wounds were ulcerated in diabetic rats in order to evaluate the capacity of LC-laden scaffolds to regenerate skin. The characterization findings demonstrated that the composite scaffolds possessed favorable antibacterial properties, cell compatibility, high swelling, controlled degradability, and good uniformity in the interconnected pore microstructure. Additionally, in terms of wound contraction, re-epithelialization, and angiogenesis improvement, LC-laden scaffolds revealed better performance in diabetic wound healing than the other groups. This research indicates that utilizing lithium chloride molecules loaded in biological materials supports the best diabetic ulcer regeneration in vivo, and produces a skin replacement with a cellular structure comparable to native skin.

Effect of nanocomposite cementitious capillary crystalline waterproofing material on self-healing properties of cementitious composites

There are limited studies about the effect of nanocomposite cementitious capillary crystalline waterproofing material (CCCW) on the self-healing properties of cementitious materials in different environments. Compressive strength recovery ratio(CSRR) test, electrochemical impedance spectroscopy (EIS) test, and macroscopic cracks healing observation test were adopted to study the self-healing properties of pure mortar specimens, mortar specimens mixed with CCCW, and nanocomposite CCCW respectively under three kinds of curing conditions. The self-healing mechanism of nanocomposite CCCW was analyzed using thermogravimetric analysis and differential scanning calorimetry (TG-DSC), mercury intrusion porosimetry (MIP), and scanning electronic microscope and energy dispersive spectroscopy (SEM-EDS) techniques. It was found that the curing condition significantly influenced self-healing performance, with touching water curing condition having the highest impact, followed by soaking water curing condition and natural curing condition. Nanocomposite CCCW promoted the healing performance of damaged specimens and significantly increased the CSRR. Under touching water curing condition, the CSRRs of the mortar groups with 3% nano-SiO2, 3% nano-CaCO3, and 2% nano-MgO were 26.1%, 11.5%, and 8.6%, respectively, higher than the CSRR of the single-doped CCCW group. After 28 days of touching water curing, change in charge transfer resistance before and after specimen healing (∆Rct) of the groups with 3% dosage of nano-SiO2, 3% dosage of nano-CaCO3, and 2% dosage of nano-MgO were 5.2, 1.8, and 2.7 times, respectively, higher than that of the single-doped CCCW mortar group. Throughout the healing process, the addition of the three nanocomposite CCCWs accelerated the hydration reaction to generate C-S-H gel, CaCO3, Aft, etc., improved the internal pore structure, reduced the size of the most probable pore diameter (MPPD) of the mortar specimens, and ultimately promoted the self-healing properties of the cementitious materials.

Shape‐memory thermosets: Tailoring the structure for toughness improvement and scratch healability

AbstractA straightforward but effective approach to fabricate shape‐memory polyurethane thermosets by tailoring the soft phase composition of two‐ and four‐armed polycaprolactone (PCL) polyols is described. As the crystallization of the PCL soft phase has an effect on driving the self‐assembly of H‐bonds, a good balance of tensile performance and thermo‐healability can be achieved by regulating the ratio between PCL‐diol and PCL‐tetrol in the soft phase. The inferior ability of crystallization of the segments near the branching point gives rise to enhancement of the both overall healability and toughness of the network. Healings of punctured holes and cuts are assessed using optical microscopy (OM), field‐emission scanning electron microscopy (FE‐SEM), tensile analysis, and two‐electrode impedence characterization. The obtained network with the best healing behavior has a soft phase composition with the PCL‐diol/PCL‐tetrol molar ratio of 2/1, a tensile toughness of 64 MPa J−1 and a healing efficiency (estimated by recovery of tensile strength) of nearly 80%.Highlights The composition of the soft phase of polyurethane networks was tailored. Two‐ and four‐armed polycaprolactones were used for the network structure. A good balance between mechanical and healing performance was obtained. Healing of complete cuts showed tensile strength recovery of nearly 80%.

A single dose of VEGF-A circular RNA sustains in situ long-term expression of protein to accelerate diabetic wound healing

Diabetic foot ulcer (DFU), which is characterised by damage to minute blood vessels or capillaries around wounds, is one of the most serious and dreaded complications of diabetes. It is challenging to repair chronic non-healing DFU wounds. Vascular endothelial growth factor (VEGF) plays an important role in angiogenesis and promotes wound healing in DFU. However, it is difficult to sustainably deliver VEGF to the wound site owing to its poor stability and easy degradation. To overcome this challenge, lipid nanoparticles (LNP) encapsulating circular RNA (circRNA) encoding VEGF-A have been developed to continuously generate and release VEGF-A and accelerate diabetic wound healing. First, VEGF-A circRNA was synthesized using group I intron autocatalysis strategy and confirmed by enzyme digestion, polymerase chain reaction, and sequencing assay. VEGF-A circRNA was encapsulated in ionizable lipid U-105-derived LNP (U-LNP) using microfluidic technology to fabricate U-LNP/VEGF-A circRNA. For comparison, a commercially ionizable lipid ALC-0315-derived LNP (A-LNP) encapsulating circRNA (A-LNP/circRNA) was used. Dynamic light scattering and transmission electron microscopy characterization indicated that U-LNP/circRNA had spherical structure with an average diameter of 108.5 nm, a polydispersity index of 0.22, and a zeta potential of -3.31 mV. The messenger RNA (mRNA) encapsulation efficiency (EE%) of U-LNP was 87.12%. In vitro transfection data confirmed better stability and long-term VEGF-A expression of circRNA compared with linear mRNA. Assessment of cytotoxicity and innate immunity further revealed that U-LNP/circRNA was biocompatible and induced a weak congenital immune response. Cell scratch and angiogenesis tests demonstrated the bioactivity of U-LNP/VEGF-A circRNA owing to its VEGF-A expression. In situ bioluminescence imaging of firefly luciferase (F-Luc) probe and ELISA demonstrated that circRNA had long-term and strong expression of VEGF-A in the first week, and a gradual decrease in the next week at the wound site and surrounding areas. Finally, a diabetic mouse model was used to validate the healing effect of U-LNP/VEGF-A circRNA formulation. The results showed that a single dose of U-LNP/VEGF-A circRNA administered by dripping resulted in almost complete wound recovery on day 12, which was significantly superior to that of U-LNP/VEGF-A linear mRNA, and it also outperformed recombinant human vascular endothelial growth factor (rhVEGF) injection and A-LNP/circRNA dripping. Histological analysis confirmed the healing efficiency and low toxicity of U-LNP/VEGF-A circRNA formulation. Together, VEGF-A circRNA delivered by U-105-derived LNP showed good performance in wound healing, which was ascribed to the long-term expression and continuous release of VEGF-A, and has potential applications for the treatment of diabetic foot ulcer wounds.