•Calcium nitrate was found to be a suitable healing agent for autonomous crack-sealing.•The use of microcapsules significantly increased the self-healing efficiency.•The healing products were mainly ...calcium carbonate.•The largest crack width healed was up to 290 µm.
Self-healing concrete through microencapsulated calcium nitrate was evaluated for its crack-sealing efficiency. The evaluated variables in this study were the microcapsule size, concentration (by weight of cement), and capsule shell properties. The production parameters for the microcapsule preparation were adjusted to control the shell properties and mean particle diameter accordingly. The results showed that all microcapsule-containing specimens had significantly higher healing efficiencies than the control groups after 21 and 42 days of healing. As the crack sizes increased, the microcapsule-containing specimens maintained a higher healing efficiency than the control groups.
Human pluripotent stem cell-based in vitro models that reflect human physiology have the potential to reduce the number of drug failures in clinical trials and offer a cost-effective approach for ...assessing chemical safety. Here, human embryonic stem (ES) cell-derived neural progenitor cells, endothelial cells, mesenchymal stem cells, and microglia/macrophage precursors were combined on chemically defined polyethylene glycol hydrogels and cultured in serum-free medium to model cellular interactions within the developing brain. The precursors self-assembled into 3D neural constructs with diverse neuronal and glial populations, interconnected vascular networks, and ramified microglia. Replicate constructs were reproducible by RNA sequencing (RNA-Seq) and expressed neurogenesis, vasculature development, and microglia genes. Linear support vector machines were used to construct a predictive model from RNA-Seq data for 240 neural constructs treated with 34 toxic and 26 nontoxic chemicals. The predictive model was evaluated using two standard hold-out testing methods: a nearly unbiased leave-one-out cross-validation for the 60 training compounds and an unbiased blinded trial using a single hold-out set of 10 additional chemicals. The linear support vector produced an estimate for future data of 0.91 in the cross-validation experiment and correctly classified 9 of 10 chemicals in the blinded trial.
► We prepared blends of chitosan and cellulose by using 1-butyl-3-methylimidazolium acetate as solvent media. ► The addition of chitosan increases the thermal stability of cellulose, slowing down its ...thermal degradation. ► The increased activation energy of the polymeric blends is indicative of enhanced stability reflecting miscibility of the two polymers. ► No apparent phase separation is identified in any of the polymeric blends.
Blends of chitosan and cellulose were successfully produced using 1-butyl-3-methylimidazolium acetate (BMIMAc) as solvent media. Films were prepared from the blends by manually spreading the solution on a flat surface and precipitating the polymers in a mixture of methanol and water. To prevent the shrinkage of films, most of the absorbed water was removed by freeze drying under vacuum. Films prepared from the polymeric solutions were investigated by means of FT-IR, TGA, X-ray diffraction and SEM measurements. The shifting of the bands corresponding to –NH and CO groups of chitosan (FT-IR), the absence of the diffraction peaks at 2θ=10.7 and 14.9° (XRD), the increased Ea for thermal decomposition for all the polymeric blends (MTGA), and the presence of an apparent homogeneous structure with no phase separation of the two polymers (SEM) provide evidence for the miscibility between chitosan and cellulose in the solid state.
Chemical modification of chitosan by introducing quaternary ammonium moieties into the polymer backbone renders excellent antimicrobial activity to the adducts. In the present study, we have ...synthesized 17 derivatives of chitosan consisting of a variety of N-aryl substituents bearing either electron-donating or electron-withdrawing groups. Selective N-arylation of chitosan was performed via Schiff bases formed by the reaction between the 2-amino groups of the glucosamine residue of chitosan with aromatic aldehydes under acidic conditions, followed by reduction of the Schiff base intermediates with sodium cyanoborohydride. Each of the derivatives was further quaternized using N-(3-chloro-2-hydroxypropyl)trimethylammonium chloride (Quat-188) as the quaternizing agent that reacted with either the primary amino or hydroxyl groups of the glucosamine residue of chitosan. The resulting quaternized materials were water soluble at neutral pH. Minimum inhibitory concentration (MIC) antimicrobial studies of these materials were carried out on Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) bacteria in order to explore the impact of the extent of N-substitution (ES) on their biological activities. At ES less than 10%, the presence of the hydrophobic substituent, such as benzyl and thiophenylmethyl, yielded derivatives with lower MIC values than chitosan Quat-188. Derivatives with higher ES exhibited reduced antibacterial activity due to low quaternary ammonium moiety content. At the same degree of quaternization, all quaternized N-aryl chitosan derivatives bearing either electron-donating or electron-withdrawing substituents did not contribute antibacterial activity relative to chitosan Quat-188. Neither the functional group nor its orientation impacted the MIC values significantly.
Blunt renal trauma is relatively common in children. Conservative management has become the mainstay of treatment. A 4-year-old boy presented following a fall onto his right abdomen resulting in ...renal trauma. Initial conservative management was followed by complete embolization of the kidney. The resulting continued hypertension, as well as endothelial disruption, resulted in PRES as manifested by a single instance of generalized seizure. The patient regained normal neurological function following nephrectomy. Better understanding of the potential for acute hypertensive crisis resulting in PRES in the urology community may result in more urgent and effective management in these scenarios.
Abstract Four biomaterial tubes, poly(lactic-co-glycolic acid) (PLGA), poly(caprolactone fumarate) (PCLF), a neutral oligo(polyethylene glycol) fumarate (OPF) hydrogel or a positively charged ...oligo(polyethylene glycol) fumarate (OPF+ ) hydrogel with a PCLF sleeve, have previously been shown to have benefits for nerve repair. However, no direct comparison to identify the optimal material have been made. Herein, these nerve tubes were implanted in a rat sciatic nerve model and nerve regeneration was quantified and compared by using accepted nerve assessment techniques. Using standard statistical methods, no significant differences of individual parameters were apparent between groups despite PCLF showing a tendency to perform better than the others. Using a mean–variance based ranking system of multiple independent parameters, statistical differences became apparent. It was clear that the PLCF tube supported significantly improved nerve regeneration and recovery compared to the other three biomaterial conduits. The ability to simultaneously compare a number of regenerative parameters and elucidate the best material from the combination of these individual parameters is of importance to the nerve regeneration area and has implications for the tissue engineering field. By using this method of comparison, a number of biomaterial constructs may be compared under similar conditions and the optimal construct elucidated using the minimal number of animals and materials.
Blending ground crumb rubber (CR) with the asphalt binder is an economical and sustainable method of binder modification. The objective of this paper was to evaluate the interaction between the ...asphalt binder and the three CR types at 170 and 190 °C. The three CR types, ambiently ground, cryogenically ground, and Ecorphalt (E-rubber), were blended with a Louisiana conventional PG 67-22 asphalt at two temperatures, 170 and 190 °C. The composition of the CR before and after treatment with asphalt was studied using thermogravimetric analysis. Gel permeation chromatography was used to study the molecular weight changes to the asphalt before and after rubber treatment. Fourier transform infrared spectroscopy was used to study the aging characteristics of the CR-modified asphalt binder prepared at the two temperatures. Scanning electron microscopy (SEM) shows the morphology of the rubbers before and after dispersion in the asphalt binder. Performance-grade tests of the CR/asphalt binder blends were used to characterize the rheological properties. E-rubber additive did allow for better dispersion of particles in the asphalt binder at a lower temperature than the other additives evaluated. Ground CR particles were comprised of favorable polyisoprene contents (minimum natural rubber content was 50%) for blending with the asphalt binder. An increase in the blending temperature from 170 to 190 °C resulted in a minimal increase in the favorable polyisoprene contents of CR/asphalt binder blends containing 5 and 10% E-rubber, which is likely to influence performance. Favorable polyisoprene contents of the CR/asphalt blends containing 10% ambiently ground CR did not change with the blending temperature, whereas that of the CR/asphalt blend containing 10% cryogenically ground increased with the blending temperature. The CR particles isolated from asphalt blends prepared at 190 °C were more swollen than those separated from asphalt blends prepared at 170 °C, as measured by SEM. Approximetely 73–87% of the E-rubber particles dissolved in the asphalt binder during blending, confirming that E-rubber had great compatibility with the binder chemistry and, hence, can improve performance.
•This study evaluated the efficiency of the rejuvenator, a heavy resin, to reverse the aging process on asphalt binders and to develop the synthesis procedure for the production of microencapsulation ...of asphalt rejuvenators.•The rejuvenator partially restored the aged binder for binder PG 70-22 and binder PG 76-22.•Increasing the amount of rejuvenator was not effective in totally reversing the aging of asphalt binder.•A procedure to microencapsulate the heavy resin rejuvenator as core material were successfully developed. The capsules were characterized.
Asphalt pavement roads are exposed to traffic loading and natural elements such as rain, sunlight and oxidation, which result in decreasing their relaxation capabilities and the initiation of cracks. Innovative maintenance techniques such as developing microcapsules with rejuvenators have emerged in order to reverse the aging process in asphalt binder. The objectives of this study were to assess the effectiveness of an asphalt rejuvenator to reverse the aging process in asphalt binder and to develop a microencapsulation procedure for the tested asphalt rejuvenator. Properties such as size, shell thickness and morphology of the prepared microcapsules were evaluated by varying the production parameters, i.e. agitation rate, heating temperature, and Ethyl Methyl Acrylate (EMA) concentration. Three binder types were considered in the experimental program, two virgin asphalt binders that were aged in the laboratory and a binder extracted from Reclaimed Asphalt Pavement (RAP). Based on the results of the experimental program, it was concluded that the binder Performance Grade (PG) 70-22 was partially restored at both high and low temperature grades with the use of the rejuvenator. In contrast, the low temperature grade of the binder PG 76-22 and the high temperature grade of the RAP binder were restored with the use of the tested rejuvenator product. Microcapsules containing the rejuvenator were synthesized and a characterization process was conducted based on microcapsule properties such as diameter, shell thickness and morphology of the prepared microcapsules.
The physiological relevance of Matrigel as a cell-culture substrate and in angiogenesis assays is often called into question. Here, we describe an array-based method for the identification of ...synthetic hydrogels that promote the formation of robust
vascular networks for the detection of putative vascular disruptors, and that support human embryonic stem cell expansion and pluripotency. We identified hydrogel substrates that promoted endothelial-network formation by primary human umbilical vein endothelial cells and by endothelial cells derived from human induced pluripotent stem cells, and used the hydrogels with endothelial networks to identify angiogenesis inhibitors. The synthetic hydrogels show superior sensitivity and reproducibility over Matrigel when evaluating known inhibitors, as well as in a blinded screen of a subset of 38 chemicals, selected according to predicted vascular disruption potential, from the Toxicity ForeCaster library of the US Environmental Protection Agency. The identified synthetic hydrogels should be suitable alternatives to Matrigel for common cell-culture applications.
The treatment of peripheral nerve injuries remains a major problem worldwide despite the availability of a number of Food and Drug Administration (FDA) approved devices which fail to match the ...efficacy of autografts. Different strategies are used to improve regeneration and functional recovery using biomaterial nerve conduits. However, there is little investigation of the transcriptomic and proteomic changes which occur as a result of these interventions, particularly regarding transection injuries. This study explores differences between autograft‐mediated repair and conduit‐material‐mediated repair of peripheral nerve injuries to understand fundamental differences in their repair mechanisms at the proteomics level at the proximal, middle, and distal components in the early stages of repair. Pathway analysis demonstrates that each material selectively activates different regenerative pathways and alters different biological functions spatially throughout the biomaterial conduits. The analysis highlights some of the deficiencies in conduit‐mediated repair in comparison to autograft (e.g., recycling of myelin and cholesterol, reduction in reactive oxygen species, and higher expression of regenerative proteins). These findings thus suggest that by supplementing the expression of these proteins on the biomaterial of choice, this study can potentially attain regeneration equivalent to autograft. This approach paves the way for incorporating future biomaterial‐specific functionalities in nerve guidance conduits.
The proteomic changes that occur spatially throughout a natural or synthetic nerve guidance conduit or within an autograft during the treatment of peripheral nerve injuries are investigated in this study. Using pathway analysis tools, this study explores how different materials in conduit‐mediated nerve repair, and how autografts, activate different biological functions during the early stages of regeneration.
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