Polysaccharide-Based Injectable Hydrogels with Fast Gelation and Self-Strengthening Mechanical Kinetics for Oral Tissue Regeneration.

Oral defects lead to a series of function disorders, severely threatening the patients' health. Although injectable hydrogels are widely studied in tissue regeneration, their mechanical performance is usually stationary after implant, without further self-adaption toward the microenvironment. Herein, an injectable hydrogel with programmed mechanical kinetics of instant gelation and gradual self-strengthening along with outstanding biodegradation ability is developed. The fast gelation is realized through rapid Schiff base reaction between biodegradable chitosan and aldehyde-modified sodium hyaluronate, while self-strengthening is achieved via slow reaction between redundant amino groups on chitosan and epoxy-modified hydroxyapatite. The resultant hydrogel also possesses multiple functions including (1) bio-adhesion, (2) self-healing, (3) bactericidal, (4) hemostasis, and (5) X-ray in situ imaging, which can be effectively used for oral jaw repair. We believe that the strategy illustrated here will provide new insights into dynamic mechanical regulation of injectable hydrogels and promote their application in tissue regeneration.

Copper-catalyzed reaction of benzoxazinanones with sulfilimines: access to 2-ethynyl-benzoimidazoles via an abnormal skeletal rearrangement.

A copper-catalyzed reaction of benzoxazinanones with N-aryl sulfilimines has been developed, providing 2-ethynyl-benzoimidazoles in good to excellent yields (up to 98%) under mild reaction conditions. Importantly, the reaction proceeds via an abnormal skeletal rearrangement and annulation process, rather than an expected (4 + 1) annulation.

Optimum substrate stiffness in coalescence-induced droplet jumping.

When droplets are brought into contact and coalesced on a superhydrophobic surface, the kinetic energy converted from the surface energy enables the merged droplet to jump. Current studies mainly focus on the microstructure of surfaces and the properties of droplets that influence the jumping dynamics. Here, by means of molecular dynamics, we investigate the coalescence-induced jumping of nanodroplets on soft substrates. The optimum stiffness of the substrate is suggested and the mechanism involved is demonstrated through the analysis of the interactions between the droplets and the substrates. The momentum of the droplet is evaluated by integrating the forces from the substrate. The optimum stiffness for jumping velocity is provided by the competition between the impact and the adhesion from the substrate during the process, which are both closely related to the stiffness. The results may inspire fundamental research and applications in a broad scope.

Higher Damping Capacities in Gradient Nanograined Metals.

The capability of damping mechanical energy in polycrystalline metals depends on the activities of defects such as dislocation and grain boundary (GB). However, operating defects has the opposite effect on strength and damping capacity. In the quest for high damping metals, maintaining the level of strength is desirable in practice. In this work, gradient nanograined structure is considered as a candidate for high-damping metals. The atomistic simulations show that the gradient nanograined models exhibit enhanced damping capacities compared with the homogeneous counterparts. The property can be attributed to the long-range order of GB orientations in gradient grains, where shear stresses facilitate GB sliding. Combined with the extraordinary mechanical properties, the gradient structure achieves a strength-ductility-damping synergy. The results provide promising solutions to the conflicts between mechanical properties and damping capacity in polycrystalline metals.

Connective tissue growth factor (CCN2) inhibits TNF-α-induced apoptosis by enhancing autophagy through the Akt and Erk pathways in osteoblasts.

Connective tissue growth factor (CTGF/CCN2) is a secreted protein modulating various biological processes, such as proliferation, differentiation, and survival. Tumor necrosis factor-α (TNF-α), known as a proinflammatory factor, negatively regulates osteoblast differentiation and survival. However, the potential mechanisms of CCN2 in TNF-α-induced osteoblast apoptosis are not fully understood. In the present study, we found that CCN2 was expressed in osteoblasts and downregulated after treatment with TNF-α. Overexpression of CCN2 attenuated TNF-α-induced osteoblast apoptosis. Autophagy, a pro-survival biological behavior, was triggered by TNF-α stimulation, and CCN2 overexpression enhanced this process. Inhibition of autophagy by chloroquine (CQ) affected the anti-apoptotic effect of CCN2. Moreover, the phosphorylation levels of Akt and Erk were upregulated in CCN2-over expressed cells, and LY294002 and U1026 (which inhibited the Akt and Erk signaling pathways, respectively) reversed the effect of CCN2 on autophagy and cell survival enhancement. Our data suggest that CCN2 might be a positive regulator of osteoblast survival in TNF-α stimulation by enhancing autophagy through the Akt and Erk signaling pathways.

Inhibition of JAK2 by AG490 promotes TNF-α-induced apoptosis by inhibiting autophagy in MC3T3-E1 cells.

Tumor necrosis factor-alpha (TNF-α), one of the pro-inflammatory factors in osteoporosis, has a strong enhancement effect on osteoclastogenesis and disruption of osteoblast survival and function. JAK2 participates in a wide range of biological processes, including bone homeostasis, but its function in osteoblast survival in inflammatory environments remains unknown. In this study, flow cytometry and immunofluorescence staining of LC3B were performed under TNF-α stimulation in MC3T3-E1 cells. Apoptosis-related protein Cleaved PARP and autophagy-related protein LC3 were upregulated, meanwhile, p62 was downregulated by TNF-α. JAK2 signaling was also activated in the process. AG490 was used to inhibit JAK2 signaling, which promoted apoptosis and attenuated autophagy induced by TNF-α. Enhancement of autophagy by rapamycin reversed the promotional effect of AG490 on apoptosis, and the autophagy inhibitor chloroquine further enhanced apoptosis. Western blot analysis showed that the STAT3, Akt, and Erk signaling pathways are involved in AG490 treatment. This study demonstrated for the first time that JAK2 inhibition by AG490 may play a crucial role in TNF-α-induced apoptosis by inhibiting autophagy and inhibiting the STAT3, Akt, and Erk signaling pathways.

Late-onset riboflavin-responsive multiple acyl-CoA dehydrogenase deficiency (MADD): case reports and epidemiology of ETFDH gene mutations.

BACKGROUND: Multiple acyl-CoA dehydrogenase deficiency (MADD) is a riboflavin-responsive lipid-storage myopathy caused by mutations in the EFTA, EFTB or ETFDH genes. We report a Chinese family of Southern Min origin with two affected siblings with late-onset riboflavin-responsive MADD due to a homozygous c.250G > A EFTDH mutation and review the genetic epidemiology of the c.250G > A mutation. CASE PRESENTATION: Both siblings presented with exercise-induced myalgia, progressive proximal muscle weakness and high levels of serum muscle enzymes and were initially diagnosed as polymyositis after a muscle biopsy. A repeat biopsy in one sibling subsequently showed features of lipid storage myopathy and genetic analysis identified a homozygous mutation (c.250G > A) in the ETFDH gene in both siblings and carriage of the same mutation by both parents. Glucocorticoid therapy led to improvement in muscle enzyme levels, but little change in muscle symptoms, and only after treatment with riboflavin was there marked improvement in exercise tolerance and muscle strength. The frequency and geographic distribution of the c.250G > A mutation were determined from a literature search for all previously reported cases of MADD with documented mutations. Our study found the c.250G > A mutation is the most common EFTDH mutation in riboflavin-responsive MADD (RR-MADD) and is most prevalent in China and South-East Asia where its epidemiology correlates with the distribution and migration patterns of the southern Min population in Southern China and neighbouring countries. CONCLUSIONS: Mutations in ETFDH should be screened for in individuals with lipid-storage myopathy to identify patients who are responsive to riboflavin. The c.250G > A mutation should be suspected particularly in individuals of southern Min Chinese background.

Strain-Engineered Adhesion and Reversible Transfer Printing of Water Droplets and Nanoparticles.

Transfer printing has been playing a crucial role in the fabrication of various functional devices. In spite of the extensive progress in technology, challenges are remaining, in the aspects of accuracy, efficiency, and adaptivity. Here, we propose a reversible transfer printing technique of tailoring adhesion by selectively stretching the surfaces. Through molecular dynamics simulations, we demonstrate the transfer of nanoscale substances such as water droplets, colloids, and nanoparticles between two graphene surfaces with strains switched on and off. We reveal the mechanism of the dynamic behaviors by analyzing the energies and driving forces of the substances during the process of transfer. The work not only advances the fundamental understanding of adhesion but also can inspire applications in the design of next-generation electronic and biomedical devices.

Ionic interaction-driven switchable bactericidal surfaces.

Bacteria in the external environment inevitably invade the wound and subsequently colonize the wound surface during surgery and biomedical operations, which slows down the process of wound healing and tissue repair; this poses a significant threat to human health. Therefore, the development of an intelligent antibacterial surface has become the focus of research in the field of antimicrobial strategies, which has important social and economic significance. Here, we present a simple approach of producing an ionic interaction-driven anionic activation substratum which is then functionalized with cationic molecules through coulombic interactional immobilization. The switchable multifunctional antibacterial surface can decrease bacterial attachment and inactivate the attached microorganisms, thus overcoming the conventional challenge for antibacterial surfaces. Briefly, poly (3-sulfopropyl methacrylate potassium salt) (PSPMA) brushes were constructed by surface-initiated atom transfer radical polymerization on silicon or cotton fabric substrates, and a positive-charged component, namely lysozyme (LYZ), hexadecyl trimethyl ammonium bromide (CTAB) or chitosan (CS), was loaded on negative-charged sulfonate groups through electrostatic interactions. The resultant brush-grafted surfaces exhibited more than ∼95.5% bactericidal efficacy and ∼92.8% release rate after the introduction of an adequate amount of contra-ions (1.0 M; Na+ & Cl-) against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, thus achieving a regenerated surface through the cyclic process of "assembly-dissociation". Smart cotton fabric (Fabric-PSPMA/LYZ and Fabric-PSPMA/CS) surfaces were constructed, which were found to promote wound epidermal tissue regeneration with a higher efficiency after 7-day in vivo studies. This ionic interaction-driven method used in the present work is simple and can reversibly renew antibacterial surfaces, which will help in the wider utilization of switchable antibacterial materials with a more ecologic and economic significance. STATEMENT OF SIGNIFICANCE: Smart antibacterial surfaces with renewable characteristics have attracted considerable interests over the past few years. Here, we used ionic interaction-driven force to manipulate dynamic conformational changes in PSPMA surface brushes, accompanied by highly switchable bacteria killing and bacteria releasing behaviors. Different cationic molecules were also designed for assembly/dissociation on the PSPMA-modified surfaces, and the essential parameters, including chemical structures, molecular weight, and cationic charge density, were investigated. With the refined structural combinations and the balance of bacteria killing/bacteria releasing behaviors, smart cotton fabrics (e.g., Fabric-PSPMA/lysozyme and Fabric-PSPMA/chitosan) were designed that could promote wound healing and tissue repair. These results contribute to the fundamental understanding of a switchable cationic-anionic pair design and the corresponding practical, renewable, highly antibacterial fabric.

Photo-switchable supramolecular comb-like polymer brush based on host-guest recognition for use as antimicrobial smart surface.

Bacterial infections from biomedical devices pose a great threat to the health of humans and thus place a heavy burden on society. Therefore, developing efficient antibacterial surfaces has attracted much attention. However, it is a challenge to identify or develop a combination that efficiently integrates multiple functions via topological tailoring and on-demand function-switch via non-contact and noninvasive stimuli. To resolve this issue, a highly hydrophilic comb polymer brush was constructed here based on supramolecular host-guest recognition. Azobenzene (azo)-modified antifouling and antibacterial polymers were incorporated into cyclodextrin (CD)-modified antifouling polymer brushes grafted on the surface. The surface thus obtained possessed excellent antifouling performance with a low bacterial density of ∼6.25 × 105 cells per cm2 after 48 h and exhibited a high efficiency of ∼88.2% for killing bacteria. Besides, irradiation with UV light resulted in the desorption of the azo-polymers and a release of ∼85.1% attached bacteria. Irradiating visible light led to the re-adsorption of azo-polymers, which regenerated the fresh surface; the process could be repeated for at least three cycles, and the surface still maintained low bacterial attachments with a cell density of ∼7.10 × 105 cells per cm2, high sterilization efficiency of ∼93.8%, and a bacteria release rate of ∼83.1% in the 3rd cycle. The photo-switchable antibacterial surface presented in this research will provide new insights into the development of smart biomedical surfaces.

Mussel-inspired functionalization of electrospun scaffolds with polydopamine-assisted immobilization of mesenchymal stem cells-derived small extracellular vesicles for enhanced bone regeneration.

Mesenchymal stem cells-derived small extracellular vesicles (MSCs-sEV) have shown promising prospects as a cell-free strategy for bone tissue regeneration. Here, a bioactive MSCs-sEV-loaded electrospun silk fibroin/poly(ε-caprolactone) (SF/PCL) scaffold was synthesized via a mussel-inspired immobilization strategy assisted by polydopamine (pDA). This pDA modification endowed the as-prepared scaffold with high loading efficiency and sustained release profile of sEV. In addition, the fabricated composite scaffold exhibited good physiochemical, mechanical, and biocompatible properties. In vitro cellular experiments indicated that the MSCs-sEV-loaded composite scaffold promoted the adhesion and spreading of preosteoblast and endothelial cells, as well as enhanced osteogenic differentiation and angiogenic activity. In vivo experiments showed that the functionalized electrospun scaffolds promoted bone regeneration in a rat calvarial bone defect model. Results suggest that the developed MSCs-sEV-anchored pDA-modified SF/PCL electrospun scaffolds possess high application potential in bone tissue engineering owing to their powerful pro-angiogenic and -osteogenic capacities, cell-free bioactivity, and cost effectiveness.

Comb-like structural modification stabilizes polyvinylidene fluoride membranes to realize thermal-regulated sustainable transportation efficiency.

Hydrophobic micro-porous membrane such as polyvinylidene fluoride (PVDF) with excellent thermal-/chemical-stability and low surface energy has received extensive attention in industrial water treatment and sustainable energy conversion. However, undesirable contaminants caused by inevitable proteins or microorganisms adhesion may lead to a rapid loss of separation efficiency, which significantly deteriorate their porous structures and eventually limit their practical performance. Herein, we present a scalable approach for fabricating comb-like copolymer modified PVDF membranes (PVDF-PN@AgNPs) that prevent bacteria from proliferating on the surface and temperature-controlled release of adhered contaminants. Comb-like structured copolymers were imparted to a polydopamine (PDA)-treated PVDF membrane by Michael addition reaction, which enabled a covalent binding of comb-like structured copolymers to the membrane. Such unique structural design of grafted copolymer, containing hydrophilic side chain and temperature-responsive chain backbone, stably prevents bacteria adhesion and provides reversible surface wettability. Therefore, the resultant membranes were evaluated to prevent bacterial adhesion, high touch-killing efficiency and temperature-controlled contaminants release (~99% of protein and ~75% of bacteria). Moreover, with the collapse and stretch of grafted copolymer chain backbone, the synthetic membrane further reversibly adjusted inner micro-porous structure and surface wettability, which eventually helped to achieve variable water fluid transport efficiency. This study not only provides a feasible structural design for stably coping with the challenging of antifouling and subsequent contamination adhesion of PVDF membrane, but also potentially answers the significant gap between lab research advances and practical application, particularly in the industrial membrane field.

Host-Guest Interaction-Mediated Photo/Temperature Dual-Controlled Antibacterial Surfaces.

Development of smart switchable surfaces to solve the inevitable bacteria attachment and colonization has attracted much attention; however, it proves very challenging to achieve on-demand regeneration for noncontaminated surfaces. We herein report a smart, host-guest interaction-mediated photo/temperature dual-controlled antibacterial surface, topologically combining stimuli-responsive polymers with nanobactericide. From the point of view of long-chain polymer design, the peculiar hydration layer generated by hydrophilic poly(2-hydroxyethyl methacrylate) (polyHEMA) segments severs the route of initial bacterial attachment and subsequent proliferation, while the synergistic effect on chain conformation transformation poly(N-isopropylacrylamide) (polyNIPAM) and guest complex dissociation azobenzene/cyclodextrin (Azo/CD) complex greatly promotes the on-demand bacterial release in response to the switch of temperature and UV light. Therefore, the resulting surface exhibits triple successive antimicrobial functions simultaneously: (i) resists ∼84.9% of initial bacterial attachment, (ii) kills ∼93.2% of inevitable bacteria attack, and (iii) releases over 94.9% of killed bacteria even after three cycles. The detailed results not only present a potential and promising strategy to develop renewable antibacterial surfaces with successive antimicrobial functions but also contribute a new antimicrobial platform to biomedical or surgical applications.

Cationic peptide-based salt-responsive antibacterial hydrogel dressings for wound healing.

Development of biological dressings has received widespread attentions due to their good breathability, biocompatibility, wettability, and the ability to absorb wound exudate without sticking to the wound. However, current proposed antibacterial hydrogels are limited antibacterial ability, short service life and insufficient biocompatibility, which are still challenging to address intricate practical applications. Here we develop a cationic peptide-based, salt-responsive hydrogel dressing with triple functions of antifouling, bactericidal, and bacterial release by combining ε-poly-l-lysine, poly(ethylene glycol) diglycidyl ether, and poly(DVBAPS-co-GMA) via a one-pot method. These designed hydrogels enabled to further quaternize to enhance antibacterial property due to the presence of amine residues. The resultant hydrogels present good antibacterial activity (>90%), biocompatibility, cell proliferation efficacy (~400%) and adhesiveness. Through in vivo and in vitro antibacterial capability tests, it is also found that hydrogels have good antifouling and sterilization capabilities, and the sterilization rate could reach up to ~96%. In addition, ~94% of the attached bacterial can be released after saline/water switching for several cycles. Taken together, the designed multiple antibacterial dressing prolongs the lifespan relying on reversible salt-responsive release and meet special requirements for wound healing. This work not only provides a platform to highlight its promising potentials in wound management but also gives a custom strategy to biomedical applications.

Proteomic Analysis of Exosomes from Adipose-Derived Mesenchymal Stem Cells: A Novel Therapeutic Strategy for Tissue Injury.

Exosomes are extracellular membranous nanovesicles that mediate local and systemic cell-to-cell communication by transporting functional molecules, such as proteins, into target cells, thereby affecting the behavior of receptor cells. Exosomes originating from adipose-derived mesenchymal stem cells (ADSCs) are considered a multipotent and abundant therapeutic tool for tissue injury. To investigate ADSC-secreted exosomes and their potential function in tissue repair, we isolated exosomes from the supernatants of ADSCs via ultracentrifugation, characterized them via transmission electron microscopy, nanoparticle tracking analysis, and Western blot analysis. Then, we determined their protein profile via proteomic analysis. Results showed that extracellular vesicles, which have an average diameter of 116 nm, exhibit a cup-shaped morphology and express exosomal markers. A total of 1,185 protein groups were identified in the exosomes. Gene Ontology analysis indicated that exosomal proteins are mostly derived from cells mainly involved in protein binding. Protein annotation via the Cluster of Orthologous Groups system indicated that most proteins were involved in general function prediction, posttranslational modification, protein turnover, and chaperoning. Further, pathway analysis revealed that most of the proteins obtained participated in metabolic pathways, focal adhesion, regulation of the actin cytoskeleton, and microbial metabolism. Some tissue repair-related signaling pathways were also discovered. The identified molecules might serve as potential therapeutic targets for future studies.

Low-dose nicotine reduces the homing ability of murine BMSCs during fracture healing.

Wound and fracture healing are affected by exposure to nicotine and other compounds in cigarettes. This study examined the effects of exposure to low-dose nicotine at sub-toxic concentrations on the proliferation, differentiation and migration of bone marrow stem cells (BMSCs) in vitro and their homing to fracture site in C57BL/6 mice. BMSCs were investigated in cells treated with or without nicotine (1 µM to 1 mM). Different concentrations of nicotine exhibited varied effects on BMSCs growth regulation and bone differentiation. CCK8 test significantly increased at a high nicotine concentration of 1 mM while calcium nodule staining with Alizarin red decreased at the same concentration. In vitro scratch test, Transwell tests and in vivo BMSCs homing tests showed negative effects on BMSCs migration at 10 µM to 1 mM nicotine test. Real-time PCR analysis revealed the down-regulation of SDF-1, CXCR4 and CXCR7, which were members of the potent chemotactic signaling system. Western blot analysis indicated the down-regulated expression levels of periostin expressed by nicotine-treated osteoblasts (1 µM to 100 µM). Micro CT results showed that nicotine delayed the fracture healing in mice. Our data suggest that exposure to low-dose nicotine concentrations may affect bone formation by inhibiting the migration and homing of BMSCs, which may be an important risk factor for bone healing delay in smoking patients.