•Fracture of 3D printed concrete is strongly affected by rheology and printing process.•Increasing printing time interval changes rheology and decreases fracture toughness.•Time effect is stronger on ...fracture characteristics of interlayers than filaments.•Dynamic oscillation sweep method reveals time-dependent storage modulus and viscosity.•Novel fracture experiment using DIC measures and visualizes process zone growth.
Concrete additive manufacturing, also known as 3D printing, opens tremendous opportunities in the construction industry, architectural design, defense and space exploration. As concrete is a quasi-brittle material and prone to fracture, it is crucial to understand the effect of the layer-by-layer manufacturing process, such as the variation in printing time intervals and the introduction of printing interlayers, on the fracture behavior of 3D printed concrete. This study elucidated the effects of early-age material rheology, printing time interval and printing path on the late-age load versus crack mouth opening displacement relation, fracture process zone, fracture toughness and fracture energy of 3D printed concrete materials with notch locations at interlayers vs filaments. A dynamic oscillation stress sweep method was used to reveal the time-dependency of early-age rheological parameters. A novel fracture experiment was designed to integrate a digital image correlation system to enable closed-loop control, measurement, and visualization of crack tip parameters during the rapid fracture processes along the printing interlayers or filaments. The results revealed that the fracture characteristics of 3D printed concrete are strongly influenced by its rheology and time-dependency of rheology, which is fundamentally different from normal cast concrete. Increasing the printing time interval increases the storage modulus, yield stress and complex viscosity of 3D printed concrete materials at different shear stress levels, consequently increasing the likelihood of imperfections, and thus decreasing the maximum process zone size developed at the crack tip, fracture toughness and fracture energy of 3D printed concrete. Such effects were found to be stronger on the fracture characteristics of printing interlayers than filaments.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A cationic star copolymer with a β-cyclodextrin core was developed for nonviral gene transfer to mouse embryonic stem cells (mESCs). The copolymer comprises poly(2-dimethyl aminoethyl methacrylate) ...as the cationic component and poly(2-hydroxyethyl methacrylate) as the non-toxic stealth component. These materials have very low toxicity and show highly efficient transfection to mESC colonies.
Low‐melting liquid metal is a hugely promising material for flexible conductive patterns due to its excellent conductivity and supercompliance, especially low‐cost and environmental liquid processing ...technology. However, the ever‐present fluidity characteristic greatly limits the stable shape and reliability of prepared liquid metal conductive electronics. Herein, a novel solidification strategy of liquid GaIn alloys by Ni doping and heat treatment is first reported, which can efficiently create a solid phase in the liquid metal and provide an effective solution for practical applications. Particularly, the liquid characteristic is preserved for conveniently fabricating different flexible electronic circuits, and then the solidification is carried out on prepared conductive patterns by heat treatment. The solidification mechanism is revealed by the interface chemical reaction between Ni and GaIn, creating the solid phase of intermetallic compound (Ga4Ni3 and InNi3) during heat treatment. Moreover, a biphasic GaInNi can be obtained by regulating the atomic ratio of gallium, indium, and nickel. As a result, the obtained GaInNi possesses extremely low sheet resistance (15 ± 4.5 to 135 ± 2.5 mΩ sq−1) and the variation of ΔR/R0 exhibits low level (0–2) when strained up to 100%, which offers a promising strategy to prepare stretchable and reliable liquid metal electronics.
A novel regulation technique for achieving liquid metal phase state is reported in this work, which is a revolutionary promotion of liquid metal engineering applications, successfully transforming an amorphous GaIn alloy into a biphasic state, while simultaneously having high conductivity, stretchability, long‐term stability, and reliable mechanical performance.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Understanding the mechanisms of chemical reactions, especially catalysis, has been an important and active area of computational organic chemistry, and close collaborations between experimentalists ...and theorists represent a growing trend. This Perspective provides examples of such productive collaborations. The understanding of various reaction mechanisms and the insight gained from these studies are emphasized. The applications of various experimental techniques in elucidation of reaction details as well as the development of various computational techniques to meet the demand of emerging synthetic methods, e.g., C–H activation, organocatalysis, and single electron transfer, are presented along with some conventional developments of mechanistic aspects. Examples of applications are selected to demonstrate the advantages and limitations of these techniques. Some challenges in the mechanistic studies and predictions of reactions are also analyzed.
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The addition of a precisely positioned chiral center in the tether of a constrained peptide is reported, yielding two separable peptide diastereomers with significantly different helicity, as ...supported by circular dichroism (CD) and NMR spectroscopy. Single crystal X‐ray diffraction analysis suggests that the absolute configuration of the in‐tether chiral center in helical form is R, which is in agreement with theoretical simulations. The relationship between the secondary structure of the short peptides and their biochemical/biophysical properties remains elusive, largely because of the lack of proper controls. The present strategy provides the only method for investigating the influence of solely conformational differences upon the biochemical/biophysical properties of peptides. The significant differences in permeability and target binding affinity between the peptide diastereomers demonstrate the importance of helical conformation.
Chirality induced helicity: A precisely positioned in‐tether carbon chiral center was able to modulate the helicity, cell permeability, and target binding affinity of a peptide. This study provides an excellent method for studying the relationship between the conformation and biochemical/biophysical properties of peptides.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Molecular dynamics (MD) simulation is a powerful tool for exploring the conformational energy landscape of proteins, and the reliability of MD results is crucially dependent on the underlying force ...field (FF). An accurate FF capable of producing balanced distributions of diverse conformations at multiple levels has been a long‐sought goal. Towards this, several decades of joint efforts have been made to address FF deficiencies, manifested by conformational biases at different levels (local conformations, secondary structures, and global extendedness of polypeptide chain). We first present the major FF biases, then review the strategies to address them separately. Specifically, both nonresidue‐specific and residue‐specific strategies for torsional parameter optimization have been applied to achieve local conformation and secondary structure balances. Significant improvements can be gained with residue‐specific torsional parameters especially when explicit dihedral couplings are considered. Further, the additional balance between protein–protein and protein–water interactions has been optimized via multiple ways to reproduce the global extendedness of polypeptide chains, especially for unfolded or disordered proteins. This review aims to summarize the most valuable experience and lessons gained from the past, which, we hope, can facilitate further improvements of both classical FFs and more sophisticated models such as polarizable FFs.
This article is categorized under:
Molecular and Statistical Mechanics > Molecular Dynamics and Monte‐Carlo Methods
Molecular and Statistical Mechanics > Molecular Mechanics
Conformational balance of peptides/proteins at different levels.
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BFBNIB, FZAB, GIS, IJS, KILJ, OILJ, SBCE, SBMB, UPUK
Chimeric antigen receptor T (CAR-T) cells have shown promising outcomes in the treatment of hematologic malignancies. However, CAR-T cell therapy in solid tumor treatment has been significantly ...hindered, due to the complex manufacturing process, difficulties in proliferation and infiltration, lack of precision, or poor visualization ability. Fortunately, recent reports have shown that functional biomaterial designs such as nanoparticles, polymers, hydrogels, or implantable scaffolds might have potential to address the above challenges. In this review, we aim to summarize the recent advances in the designs of functional biomaterials for assisting CAR-T cell therapy for potential solid tumor treatments. Firstly, by enabling efficient CAR gene delivery
in vivo
and
in vitro
, functional biomaterials can streamline the difficult process of CAR-T cell therapy manufacturing. Secondly, they might also serve as carriers for drugs and bioactive molecules, promoting the proliferation and infiltration of CAR-T cells. Furthermore, a number of functional biomaterial designs with immunomodulatory properties might modulate the tumor microenvironment, which could provide a platform for combination therapies or improve the efficacy of CAR-T cell therapy through synergistic therapeutic effects. Last but not least, the current challenges with biomaterials-based CAR-T therapies will also be discussed, which might be helpful for the future design of CAR-T therapy in solid tumor treatment.
Advances in functional biomaterial designs for assisting CAR-T therapy against solid tumors.
Bacterial infections remain a leading threat to global health because of the misuse of antibiotics and the rise in drug‐resistant pathogens. Although several strategies such as photothermal therapy ...and magneto‐thermal therapy can suppress bacterial infections, excessive heat often damages host cells and lengthens the healing time. Here, a localized thermal managing strategy, thermal‐disrupting interface induced mitigation (TRIM), is reported, to minimize intercellular cohesion loss for accurate antibacterial therapy. The TRIM dressing film is composed of alternative microscale arrangement of heat‐responsive hydrogel regions and mechanical support regions, which enables the surface microtopography to have a significant effect on disrupting bacterial colonization upon infrared irradiation. The regulation of the interfacial contact to the attached skin confines the produced heat and minimizes the risk of skin damage during thermoablation. Quantitative mechanobiology studies demonstrate the TRIM dressing film with a critical dimension for surface features plays a critical role in maintaining intercellular cohesion of the epidermis during photothermal therapy. Finally, endowing wound dressing with the TRIM effect via in vivo studies in S. aureus infected mice demonstrates a promising strategy for mitigating the side effects of photothermal therapy against a wide spectrum of bacterial infections, promoting future biointerface design for antibacterial therapy.
A localized thermal‐management strategy from thermal‐disrupting interface induced mitigation (TRIM) is developed to maintain intercellular cohesion and reduce function loss of epidermis tissue for topical antibacterial therapy. A dressing film with the TRIM effect inhibits aggregation of bacteria, promotes selective elimination of pathogens, and shortens the healing process.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Nano–bio interfaces are emerging from the convergence of engineered nanomaterials and biological entities. Despite rapid growth, clinical translation of biomedical nanomaterials is heavily ...compromised by the lack of comprehensive understanding of biophysicochemical interactions at nano–bio interfaces. In the past decade, a few investigations have adopted a combinatorial approach toward decoding nano–bio interfaces. Combinatorial nano–bio interfaces comprise the design of nanocombinatorial libraries and high-throughput bioevaluation. In this Perspective, we address challenges in combinatorial nano–bio interfaces and call for multiparametric nanocombinatorics (composition, morphology, mechanics, surface chemistry), multiscale bioevaluation (biomolecules, organelles, cells, tissues/organs), and the recruitment of computational modeling and artificial intelligence. Leveraging combinatorial nano–bio interfaces will shed light on precision nanomedicine and its potential applications.
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This study revealed the relationship among early-age thixotropic behavior, air-phase microstructure, and fracture properties of the interlayer region in additively manufactured (AM) cementitious ...materials. Cementitious materials were designed and characterized to possess distinctive rheological properties and were additively manufactured into cementitious specimens. The effects of thixotropy and printing time interval on the volume, size and aspect ratios of air-phase clusters and on their statistical distributions were analyzed comprehensively through three-dimensional micro-computed tomography. Also determined were the effects of thixotropy and printing time interval on the fracture properties of the interlayer regions. Based on the experimental evidence, the underlying mechanisms of how the time-dependent thixotropic behavior of AM cementitious materials impacts interlayer microstructure and fracture properties were discussed. The results shed light on material design strategies, through tailoring the fresh-state thixotropy of AM cementitious materials, to mitigate the sensitivity of their hardened-state properties to printing parameters.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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