Synthesis of biocompatible BSA-GMA and two-photon polymerization of 3D hydrogels with free radical type I photoinitiator.

Although the development of three-dimensional (3D) printing technology is growing rapidly in the biomedical field, it remains a challenge to achieve arbitrary 3D structures with high resolution and high efficiency. Protein hydrogels fabricated by two- photon polymerization (TPP) have excellent mechanical properties, high precision, and 3D architecture. However, a large number of the amino acid group in bovine serum albumin (BSA) would be consumed when the protein-based hydrogels use dyes of free radical type II photoinitiators. In this study, we use glycidyl methacrylate (GMA) to modify BSA molecules to obtain a series of BSA-GMA materials, allowing the protein material to be two-photon polymerized with a water-soluble free radical type I photoinitiator. The precisely controllable 3D structure of the BSA-GMA hydrogel was fabricated by adjusting the concentration of the precursor solution, the degree of methacrylation, and the processing parameters of the TPP technique. Importantly, BSA-GMA materials are free of acidic hazardous substances. Meanwhile, the water-soluble initiator lithium phenyl (2,4,6-trimethylbenzoyl) phosphite (LAP) allows TPP on the vinyl group of the GMA chain and thus without consuming its amino acid group. The as-prepared BSA-GMA hydrogel structure exhibits excellent autofluorescence imaging, pH responsiveness, and biocompatibility, which would provide new avenues for potential applications in tissue engineering and biomedical fields to meet specific biological requirements.

Tuning the Covalent Coupling Degree between the Cathode and Electrolyte for Optimized Interfacial Resistance in Solid-State Lithium Batteries.

The development of promising solid-state lithium batteries has been a challenging task mainly due to the poor interfacial contact and high interfacial resistance at the electrode/solid-state electrolyte (SSE) interface. Herein, we propose a strategy for introducing a class of covalent interactions with varying covalent coupling degrees at the cathode/SSE interface. This method significantly reduces interfacial impedances by strengthening the interactions between the cathode and SSE. By adjusting the covalent coupling degree from low to high, an optimal interfacial impedance of 33 Ω cm-2 was achieved, which is even lower than the interfacial impedance using liquid electrolytes (39 Ω cm-2). This work offers a fresh perspective on solving the interfacial contact problem in solid-state lithium batteries.

22 nm Resolution Achieved by Femtosecond Laser Two-Photon Polymerization of a Hyaluronic Acid Vinyl Ester Hydrogel.

Three-dimensional (3D) bioinspired hydrogels have played an important role in tissue engineering, owing to their advantage of excellent biocompatibility. Here, the two-photon polymerization (TPP) of a 3D hydrogel with high precision has been investigated, using the precursor with hyaluronic acid vinyl ester (HAVE) as the biocompatibility hydrogel monomer, 3,3'-((((1E,1'E)-(2-oxocyclopentane-1,3-diylidene) bis(methanylylidene)) bis(4,1-phenylene)) bis(methylazanediyl))dipropanoate as the water-soluble initiator, and dl-dithiothreitol (DTT) as the click-chemistry cross-linker. The TPP properties of the HAVE precursors have been comprehensively investigated by adjusting the solubility and the formulation of the photoresist. The feature line width of 22 nm has been obtained at a processing laser threshold of 3.67 mW, and the 3D hydrogel scaffold structures have been fabricated. Furthermore, the average value of Young's modulus is 94 kPa for the 3D hydrogel, and cell biocompatibility has been demonstrated. This study would provide high potential for achieving a 3D hydrogel scaffold with highly precise configuration in tissue engineering and biomedicine.

Wetting of Cell Aggregates on Microdisk Topography Structures Achieved by Maskless Optical Projection Lithography.

Cell aggregates as a 3D culture model can effectively mimic the physiological processes such as embryonic development, immune response, and tissue renewal in vivo. Researches show that the topography of biomaterials plays an important role in regulating cell proliferation, adhesion, and differentiation. It is of great significance to understand how cell aggregates respond to surface topography. Herein, microdisk array structures with the optimized size are used to investigate the wetting of cell aggregates. Cell aggregates exhibit complete wetting with distinct wetting velocities on the microdisk array structures of different diameters. The wetting velocity of cell aggregates reaches a maximum of 293 µm h-1 on microdisk structures with a diameter of 2 µm and is a minimum of 247 µm h-1 on microdisk structures of 20 µm diameter, which suggests that the cell-substrates adhesion energy on the latter is smaller. Actin stress fibers, focal adhesions (FAs), and cell morphology are analyzed to reveal the mechanisms of variation of wetting velocity. Furthermore, it is demonstrated that cell aggregates adopt climb and detour wetting modes on small and large-sized microdisk structures, respectively. This work reveals the response of cell aggregates to micro-scale topography, providing guidance for better understanding of tissue infiltration.

Preparation and characterization of a neutralizing murine monoclonal antibody against tetanus toxin.

After Clostridium tetani infects the human body, it propagates under anaerobic conditions and produces tetanus neurotoxin (TeNT). TeNT can affect the central nervous system, inhibit the release of neurotransmitters, and result in respiratory failure, which are the root causes of death in tetanus patients. Identifying monoclonal antibodies (mAbs) targeting TeNT with neutralizing activity is urgently needed for the prevention and treatment of tetanus infection. In this study, through immunizing BALB/c mice with tetanus toxoid (TT), we obtained six positive hybridoma cell lines (1A7, 2C7, 3A7, 3H4, 4C1, and 4E12). Antibody isotyping showed that the antibodies are all of the IgG1/κ subclass. Ascites fluid was prepared by allogeneic ascites induction and the antibodies were purified through protein G affinity chromatography columns. Purities of the produced murine mAbs were all greater than 95%. All six antibodies bound to linear epitopes, among which 3A7 bound to the TeNT/L domain and the other five antibodies bound to the TeNT/Hc domain. Moreover, the affinity constants of these six antibodies against the antigen were all in the nanomolar range, and the affinity of 4E12 antibody reached the picomolar range. Results from toxin-neutralization assays in mice showed that 2C7 antibody delayed animal death, while 1A7, 3A7, 3H4, and 4E12 antibodies conferred partial protection. Additionally, 4C1 antibody offered complete protection, as 200 µg of 4C1 antibody fully protected against toxin challenge with 10 LD50 of TeNT and had a window period of 1 h. Antibody epitope grouping results revealed that the binding epitopes of 4C1 antibody were different from those of the other five antibodies. When 4C1 antibody was used in combination with another antibody, the neutralizing activities of antibodies were all evidently enhanced. Specifically, 4C1 combined with 3A7 antibody led to the greatest improvement in neutralizing activities, and 20 µg antibodies total (10 + 10 µg) fully protected against toxin challenge with 10 LD50. When 4E12, 3A7, and 4C1 antibodies were used in combination, 18 µg antibodies total (6 + 6 + 6 µg) completely neutralized 10 LD50 toxin. The present study derived murine mAbs with neutralizing activities and laid the foundation for follow-up therapeutic drug development for TeNT poisoning as well as establishment of TeNT detection methods.

Multimodal fusion and human-robot interaction control of an intelligent robot.

Introduction: Small-scaled robotic walkers play an increasingly important role in Activity of Daily Living (ADL) assistance in the face of ever-increasing rehab requirements and existing equipment drawbacks. This paper proposes a Rehabilitation Robotic Walker (RRW) for walking assistance and body weight support (BWS) during gait rehabilitation. Methods: The walker provides the patients with weight offloading and guiding force to mimic a series of the physiotherapist's (PT's) movements, and creates a natural, comfortable, and safe environment. This system consists of an omnidirectional mobile platform, a BWS mechanism, and a pelvic brace to smooth the motions of the pelvis. To recognize the human intentions, four force sensors, two joysticks, and one depth-sensing camera were used to monitor the human-machine information, and a multimodal fusion algorithm for intention recognition was proposed to improve the accuracy. Then the system obtained the heading angle E, the pelvic pose F, and the motion vector H via the camera, the force sensors, and the joysticks respectively, classified the intentions with feature extraction and information fusion, and finally outputted the motor speed control through the robot's kinematics. Results: To validate the validity of the algorithm above, a preliminary test with three volunteers was conducted to study the motion control. The results showed that the average error of the integral square error (ISE) was 2.90 and the minimum error was 1.96. Discussion: The results demonstrated the efficiency of the proposed method, and that the system is capable of providing walking assistance.

Micropattern of Silver/Polyaniline Core-Shell Nanocomposite Achieved by Maskless Optical Projection Lithography.

With the development of device miniaturization, a flexible and fast preparation method is in demand for achieving microstructures with desired patterns. We develop a novel photoreduction-polymerization method for preparing conductive metal-polymer patterns. Ag/polyaniline (PANI) nanocomposites have been successfully synthesized by maskless optical projection lithography (MOPL) technology, which is based on multiphoton absorption and the localized surface plasmon resonance (LSPR) effect. The individualized design and synthesis of the nanocomposite patterns at the micro-nano scale are flexibly realized on a variety of substrates. The surface-enhanced Raman scattering (SERS) effect of Rhodamine 6G (R6G) is demonstrated on the microstructure of a square maze-shaped Ag/PANI nanocomposite. The electrical conductivity of the as-prepared nanocomposite is obtained. The preparation protocol proposed in this study opens up new avenues for the fabrication of micro-nano devices such as sensors and detectors.

A CRISPR/Cas12a-based DNAzyme visualization system for rapid, non-electrically dependent detection of Bacillus anthracis.

As next-generation pathogen detection methods, CRISPR-Cas-based detection methods can perform single-nucleotide polymorphism (SNP) level detection with high sensitivity and good specificity. They do not require any particular equipment, which opens up new possibilities for the accurate detection and identification of Bacillus anthracis. In this study, we developed a complete detection system for B. anthracis based on Cas12a. We used two chromosomally located SNP targets and two plasmid targets to identify B. anthracis with high accuracy. The CR5 target is completely new. The entire detection process can be completed within 90 min without electrical power and with single-copy level sensitivity. We also developed an unaided-eye visualization system based on G4-DNAzyme for use with our CRISPR-Cas12a detection system. This visualization system has good prospects for deployment in field-based point-of-care detection. We used the antisense nucleic acid CatG4R as the detection probe, which showed stronger resistance to interference from components of the solution. CatG4R can also be designed as an RNA molecule for adaptation to Cas13a detection, thereby broadening the scope of the detection system.

Modulation of Cell Behavior by 3D Biocompatible Hydrogel Microscaffolds with Precise Configuration.

Three-dimensional (3D) micronano structures have attracted much attention in tissue engineering since they can better simulate the microenvironment in vivo. Two-photon polymerization (TPP) technique provides a powerful tool for printing arbitrary 3D structures with high precision. Here, the desired 3D biocompatible hydrogel microscaffolds (3D microscaffold) with structure design referring to fibroblasts L929 have been fabricated by TPP technology, particularly considering the relative size of cell seed (cell suspension), spread cell, strut and strut spacing of scaffold. Modulation of the cell behavior has been studied by adjusting the porosity from 69.7% to 89.3%. The cell culture experiment results reveal that the obvious modulation of F-actin can be achieved by using the 3D microscaffold. Moreover, cells on 3D microscaffolds exhibit more lamellipodia than those on 2D substrates, and thus resulting in a more complicated 3D shape of single cell and increased cell surface. 3D distribution can be also achieved by employing the designed 3D microscaffold, which would effectively improve the efficiency of information exchange and material transfer. The proposed protocol enables us to better understand the cell behavior in vivo, which would provide high prospects for the further application in tissue engineering.

Obtaining Specific Sequence Tags for Yersinia pestis and Visually Detecting Them Using the CRISPR-Cas12a System.

Three worldwide historical plague pandemics resulted in millions of deaths. Yersinia pestis, the etiologic agent of plague, is also a potential bioterrorist weapon. Simple, rapid, and specific detection of Y. pestis is important to prevent and control plague. However, the high similarity between Y. pestis and its sister species within the same genus makes detection work problematic. Here, the genome sequence from the Y. pestis CO92 strain was electronically separated into millions of fragments. These fragments were analyzed and compared with the genome sequences of 539 Y. pestis strains and 572 strains of 20 species within the Yersinia genus. Altogether, 97 Y. pestis-specific tags containing two or more single nucleotide polymorphism sites were screened out. These 97 tags efficiently distinguished Y. pestis from all other closely related species. We chose four of these tags to design a Cas12a-based detection system. PCR-fluorescence methodology was used to test the specificity of these tags, and the results showed that the fluorescence intensity produced by Y. pestis was significantly higher than that of non-Y. pestis (p < 0.0001). We then employed recombinase polymerase amplification and lateral flow dipsticks to visualize the results. Our newly developed plasmid-independent, species-specific library of tags completely and effectively screened chromosomal sequences. The detection limit of our four-tag Cas12a system reached picogram levels.

Ionic Carbazole-Based Water-Soluble Two-Photon Photoinitiator and the Fabrication of Biocompatible 3D Hydrogel Scaffold.

Two-photon polymerization of a three-dimensional (3D) hydrogel structure has been widely applied in biological tissue engineering. For improving the biocompatibility of hydrogel structures, a new kind of ionic carbazole water-soluble photoinitiator was prepared to realize the fabrication of a 3D hydrogel structure in aqueous phase. 3,6-Bis[2-(1-methyl-pyridinium)vinyl]-9-methyl-carbazole diiodide (BMVMC) and cucurbit[7]uril (CB7) have been employed to generate a complex with better water solubility by host-guest interactions. The binding ratio of the complex was demonstrated to be 1:1 through the characterization of isothermal titration calorimetry (ITC). The two-photon absorption (TPA) cross section of the complex increases to 2500 GM compared with the 750 GM of the BMVMC molecule. Then, an aqueous-phase photoresist was obtained using the CB7/BMVMC complex as the photoinitiator and poly(ethylene glycol) diacrylate (PEGda) as the hydrogel monomer. Two-photon fabrication capability in aqueous phase has been studied using the as-prepared photoresist. A low laser threshold of 3.7 mW as well as a high resolution of 180 nm are achieved. Benefiting from the fluorescence properties of the photoinitiator, we can achieve the confocal fluorescence images without any assistance of fluorescent probes. Subsequently, a 3D engineered hydrogel scaffold microstructure was fabricated by the two-photon polymerization technology, whose biocompatibility was demonstrated by culturing the structure with living cells of L929. The BMVMC-CB7 complex and the as-prepared photoresist are demonstrated to have good biocompatibility, which is prospective for further application in tissue engineering.

Homogeneous triple-phase interfaces enabling one-pot route to metal compound/carbon composites.

Metal compounds (e.g., metal phosphides/sulfides/selenides) coupled with carbon materials have recently drawn great attraction for boosting the electrochemical performances because of their appealing synergistic effect and valuable structural stability. Despite many examples for their synthesis exist, there is still a need for a simplistic and comprehensive approach to such metal compound/carbon (MC/C) composites. Herein, an effective, facile, yet versatile strategy to produce various types of MC/C composites is presented. Key to this strategy is construction of a homogeneous triple-phase interface, which is realized by utilization of a hybrid assembly integrated with carbon, metal and sulfide (or selenide, phosphide) precursors through coupling metal cations with anion groups of a functional polymer. Such an intimately binding carbon-metal-sulfide (or selenide, phosphide) interface structure enables the successful in situ generation of MC nanoparticles uniformly encapsulated into the carbon matrix just after a one-step carbonization treatment. The present synthetic strategy provides remarkable adjustability, predictability and generality to facilely fabricate a series of MC/C composites, offering sufficient freedom to explore their unique energy storage/conversation properties. As a proof of concept, the as-prepared SnS/C composite exhibits superior lithium ion and potassium ion storage capabilities when used as anode materials for alkali-metal ion batteries. The present work provides impressive insights into the design principles for MC/C composites that are the potential materials in targeted application fields, and opens up an efficacious avenue for their facile synthesis as well.

Facile construction of uniform ultramicropores in porous carbon for advanced sodium-ion battery.

Facile fabrication of anode materials with low cost, good rate capability and high capacity is a critical factor towards developing sodium-ion battery for practical applications. Herein, a N, O co-doped porous carbon with uniform ultramicropores (NOPC-UM), is synthesized by an in-situ ultramicro templating strategy, and demonstrated as a high-performance sodium-ion storage material. Key to this strategy is employment of an inherent KCl as untramicro template, which leads to formation of uniform size of ultramicropores and heteroatoms (i.e., N and O) doping after high-temperature pyrolysis. The as-constructed NOPC-UM delivers a large capacity of 305 mAh g-1, accompanying with a 93% specific capacity below 1.00 V, and superior cycling stability about 100% after 4000 cycles. These attractive electrochemical performances endow NOPC-UM with impressive potential use as anode materials of sodium-ion battery.

Propelling electrochemical kinetics of transition metal oxide for high-rate lithium-ion battery through in situ deoxidation.

To engineer advanced anodes for high-rate lithium-ion battery, rational structural design with insightful understanding of rapid reaction kinetics is important and still highly desirable. In this work, a high-temperature in situ deoxidation strategy is used to propel electrochemical kinetics of NiO through incorporating an intrinsic Ni component. Both theoretical calculation and experimental study demonstrate that the Ni-NiO heterojunction significantly enhances the electronic conductivity and ion diffusion properties. Accordingly, the lithium-ion battery modified with the heterostructured Ni-NiO shows remarkably improved charge transfer efficiency and rate performance, substantially outperforming many reported NiO-based anodes. This work opens up the exploration of heterostructured metal compounds as kinetic regulators for high-rate lithium-ion battery and also enlightens the understanding of defect chemistry in propelling electrochemical reactions.

Production and characterization of a neutralizing antibody against botulinum neurotoxin A.

As a category A toxic, the botulinum toxin(BoNT) is responsible for human botulism with an estimated lethal dose of 1 ng/kg which greatly increases the potential risk of use as bioweapons. Therefore, the development of anti-BoNT antibodies is urgent. In this paper, the HC domain of BoNT/A was purified and immunized with Balb/c mice. Monoclonal antibodies were screened against BoNT/A from 55 stable positive hybridoma cell lines, and one with the strongest neutralizing activity, designated as ML06, was subcloned, sequenced, and classified as IgG1(κ) subclass. The mouse protection assays showed that ML06 can neutralize the toxin of BoNT/A effectively both in vitro and in vivo, in a dose-dependent manner. The therapeutic assays showed that only 20% of mice injected with 4 LD50 BoNT/A can survive another injection of ML06 after 4 h. The prophylaxis assays showed the residual ML06 from mice injected with ML06 two weeks ago can protect mice against 4 LD50 BoNT/A challenge completely. Collectively, our results indicated that ML06 served as a good candidate for further development of immune therapeutics for BoNT/A.

Non-tubular-biomass-derived nitrogen-doped carbon microtubes for ultrahigh-area-capacity lithium-ion batteries.

The ever-increasing electric vehicles and portable electronics make lithium-ion barreries (LIBs) toward high energy density, resulting in long driving range and standby times. Generally, excellent electrochemical performance can be obtained in thin electrode materials with low mass loadings (<1 mg cm-2), but it is difficult to be achieved in commercial electrodes with high mass loadings (>10 mg cm-2). In this work, we report a facile method for fabricating nitrogen doped carbon microtubes (N-CMTs) consisted of crumped carbon nanosheets for high-performance LIBs with ultrahigh mass loading, where non-tubular biomass waste (i.e., peanut dregs) is employed as the precursor. Benefiting from the hollow tubular conductive network, high graphitization, and hierarchical structure, the as-synthesized N-CMTs exhibit ultrahigh area capacity of 6.27 mAh cm-2 at a current density of 1.5 mA cm-2 with a high mass loading of 15 mg cm-2 and superior cycling stability for LIBs. Our approach provides an effective strategy for the preparation of nitrogen-doped carbon microtubes to develope high energy LIBs with high mass loading electrodes.

Facile Synthesis of Core-Shell Structured SiO2@Carbon Composite Nanorods for High-Performance Lithium-Ion Batteries.

Recently, SiO2 has attracted wide attention in lithium-ion batteries owing to its high theoretical capacity and low cost. However, the utilization of SiO2 is impeded by the enormous volume expansion and low electric conductivity. Although constructing SiO2/carbon composite can significantly enhance the electrochemical performance, the skillful preparation of the well-defined SiO2/carbon composite is still a remaining challenge. Here, a facile strategy of in situ coating of polydopamine is applied to synthesis of a series of core-shell structured SiO2@carbon composite nanorods with different thicknesses of carbon shells. The carbon shell uniformly coated on the surface of SiO2 nanorods significantly suppresses the volume expansion to some extent, as well as improves the electric conductivity of SiO2. Therefore, the composite nanorods exhibit a remarkable electrochemical performance as the electrode materials of lithium-ion batteries. For instance, a high and stable reversible capacity at a current density of 100 mA g-1 reaches 690 mAh g-1 and a capacity of 344.9 mAh g-1 can be achieved even at the high current density of 1000 mA g-1. In addition, excellent capacity retention reaches 95% over 100 cycles. These SiO2@carbon composite nanorods with decent electrochemical performances hold great potential for applications in lithium-ion batteries.

Improved ion-diffusion performance by engineering an ordered mesoporous shell in hollow carbon nanospheres.

A new kind of hollow carbon nanosphere with an ordered mesoporous shell structure is prepared and demonstrated to have improved performances in practical application areas involving fast ion transport.

A self-crosslinking procedure to construct yolk-shell Au@microporous carbon nanospheres for lithium-sulfur batteries.

An efficient self-crosslinking procedure to reasonably construct porous shells is reported for the synthesis of yolk-shell Au@microporous carbon nanospheres.

Engineering of nanonetwork-structured carbon to enable high-performance potassium-ion storage.

Potassium-ion batteries (KIBs) have been developed as an emerging electrochemical energy storage device due to the low cost and abundant resource of potassium. However, they suffer insufficient cyclability and poor rate capability caused by the large K+, severely limits their further applications. Herein, a nanonetwork-structured carbon (NNSC) is reported to address the issue. Cycling stability with very low decay rate of 0.004% per cycle over 2000 cycles and excellent rate capability (i.e., 261 mAh g-1 at 100 mA g-1 and 108 mAh g-1 at 5000 mA g-1) are achieved. The superior performance is attributed to the unique structure of NNSC, in which the three-dimensional interconnected hierarchical porous structure with hollow nanosphere as network units not only can effectively alleviate the volume expansion induced by the insertion of large K+, but also can offer fast pathways for K+ diffusion. In addition, the local graphitized carbon shell of NNSC can promote conductivity of material and reduce the resistance to K+ transportation. Thus, the NNSC has great potential in developing stable-structure and high-rate electrodes for next generation KIBs.