Novel shish-kebab structured nanofibrous decorating chitosan unidirectional scaffolds to mimic extracellular matrix for tissue engineering.

Electrospun nanofibrous scaffolds are renowned for their ability to mimic the microstructure of the extracellular matrix (ECM). However, they often fail to replicate the geometry of target tissues, and the biocompatibility of these scaffolds those made from synthetic polymers is always limited due to the lack of cell binding sites. To address these issues, we proposed an innovative approach that combined unidirectional freeze-drying and electrospinning. During this process, electrospun polycaprolactone (PCL) nanofibers were chopped into nanofibrils, which range in size up to several hundred micrometers, and were incorporated into the chitosan scaffolds via unidirectional freeze-drying. In these scaffolds, the chitosan phase was responsible for maintaining the structural integrity at the macroscale, while the embedded nanofibers enhanced the surface topography at the microscale. The resulting scaffolds exhibited a high porosity of 90% and an impressive water uptake capacity of 2500%. Furthermore, 3T3 fibroblast cells showed strong interactions with the scaffolds, characterized by high rates of cell proliferation and viability. The cells also displayed significant orientation along the direction of the pores, suggesting that the scaffolds effectively guided cellular growth.

A Flexible Sensor with Excellent Environmental Stability Using Well-Designed Encapsulation Structure.

The hydrogel-based sensors suffer from poor stability and low sensitivity, severely limiting their further development. It is still "a black box" to understand the effect of the encapsulation as well as the electrode on the performance of the hydrogel-based sensors. To address these problems, we prepared an adhesive hydrogel that could robustly adhere to Ecoflex (adhesive strength is 4.7 kPa) as an encapsulation layer and proposed a rational encapsulation model that fully encapsulated the hydrogel within Ecoflex. Owing to the excellent barrier and resilience of Ecoflex, the encapsulated hydrogel-based sensor can still work normally after 30 days, displaying excellent long-term stability. In addition, we performed theoretical and simulation analyses on the contact state between the hydrogel and the electrode. It was surprising to find that the contact state significantly affects the sensitivity of the hydrogel sensors (the maximum difference in sensitivity was 333.6%), indicating that the reasonable design of the encapsulation and electrode are indispensable parts for fabricating successful hydrogel sensors. Therefore, we paved the way for a novel insight to optimize the properties of the hydrogel sensors, which is greatly favorable to developing hydrogel-based sensors to be applied in various fields.

Development and Applications of Hydrogel-Based Triboelectric Nanogenerators: A Mini-Review.

In recent years, with the appearance of the triboelectric nanogenerator (TENG), there has been a wave of research on small energy harvesting devices and self-powered wearable electronics. Hydrogels-as conductive materials with excellent tensile properties-have been widely focused on by researchers, which encouraged the development of the hydrogel-based TENGs (H-TENGs) that use the hydrogel as an electrode. Due to the great feasibility of adjusting the conductivity and mechanical property as well as the microstructure of the hydrogels, many H-TENGs with excellent performance have emerged, some of which are capable of excellent outputting ability with an output voltage of 992 V, and self-healing performance which can spontaneously heal within 1 min without any external stimuli. Although there are numerous studies on H-TENGs with excellent performance, a comprehensive review paper that systematically correlates hydrogels' properties to TENGs is still absent. Therefore, in this review, we aim to provide a panoramic overview of the working principle as well as the preparation strategies that significantly affect the properties of H-TENGs. We review hydrogel classification categories such as their network composition and their potential applications on sensing and energy harvesting, and in biomedical fields. Moreover, the challenges faced by the H-TENGs are also discussed, and relative future development of the H-TENGs are also provided to address them. The booming growth of H-TENGs not only broadens the applications of hydrogels into new areas, but also provides a novel alternative for the sustainable power sources.

Design and Optimization Principles of Cylindrical Sliding Triboelectric Nanogenerators.

Reciprocating motion is a widely existing form of mechanical motion in the natural environment. Triboelectric nanogenerators (TENGs) that work in sliding mode are ideal for harnessing large-distance reciprocating motion, and their energy conversion efficiency could be greatly enhanced by adding springs to them. Herein, we focused on investigating the design and optimization principles of sliding mode TENGs by analyzing the effects of spring parameters and vibration frequency on the triboelectric output performance of typical cylindrical sliding TENGs (CS-TENGs). Experimental study and finite elemental analysis were carried out based on a CS-TENG model assembled using a polytetrafluoroethylene (PTFE) film as the negative layer and an aluminum film as the positive layer. The energy output was found to be mainly affected by the change of relative displacement between the two friction layers, rather than the reactive force applied by the springs or the velocity of the sliding motion. However, the frequency of the output signals could be improved when the stiffness coefficient of the springs and the CS-TENG vibration frequency were increased. This study provides valuable directions for the design and optimization of sliding mode TENGs containing springs, and will motivate in-depth research on the fundamental principles of TENG operation.

Enhancing the Performance of Fabric-Based Triboelectric Nanogenerators by Structural and Chemical Modification.

Fabric-based triboelectric nanogenerators (TENGs) are promising candidates as wearable energy-harvesting devices and self-powered sensors. Booting the power generation performance is an eternal pursuit for TENGs. Herein, an efficient approach was proposed to enhance the triboelectric performance of commercial velvet fabric by enriching the fiber surface with hierarchical structures and amide bonds through chemical grafting of carbon nanotube (CNT) and poly(ethylenimine) (PEI) via a polyamidation reaction. With an optimized modifier concentration, the fabric-based TENG easily achieved over 10 times improvement in output voltage and current at a low modifier content of less than 1 wt %. The modified-fabric-based TENG was fully washable and exhibited excellent robustness and long-term stability. With a maximum power density of 3.2 W/m2 achieved on a 5 × 106 Ω external resistor, the TENG was able to serve as a power source for various small electronics such as pedometer, digital watch, calculator, and digital timer. In addition, the TENG demonstrated capability in self-powered tactile and pressure sensing and promising potential in human-computer interface applications. The approach proposed provides a feasible path for boosting the triboelectric performance of fabric-based TENGs and gives insights into the design of fabric-based nanogenerators and smart textiles.

Enhancing the Performance of a Stretchable and Transparent Triboelectric Nanogenerator by Optimizing the Hydrogel Ionic Electrode Property.

Triboelectric nanogenerators (TENGs) with high transparency and stretchability are desired for invisible and adaptable energy harvesting and sensing. Hydrogel-based TENGs (H-TENG) have shown promising attributes toward flexible and transparent devices. However, the effect of hydrogel property on the triboelectric performance of H-TENG is rarely investigated. Herein, dual-network hydrogels composed of dual-cross-linked poly(vinyl alcohol) (PVA) and sodium alginate (SA) were synthesized and used as ionic electrodes in H-TENGs. The elasticity of the hydrogel was controlled by varying the concentration of SA, and the distinct influence of hydrogel viscoelastic property on H-TENG performance was verified for the first time. By tuning the conductivity and viscoelasticity of PVA/SA hydrogel, the optimum H-TENG exhibited high transparency (over 90%) and stretchability (over 250%) and peak output voltage and current of 203.4 V and 17.6 µA, respectively. A specially designed polydimethylsiloxane (PDMS) bag effectively prevents hydrogel dehydration and maintains a stable output in continuous operation. The H-TENG achieved a power density of 0.98 W/m2 on a 4.7 MΩ external resistor. The H-TENG could easily light 240 green and blue LEDs simultaneously and demonstrated capability to power small electronics, such as a digital timer and pedometer. This study provides insights into the influence of hydrogel property on H-TENG performance and gives guidance for designing and fabricating highly stretchable and transparent TENGs.

The complete mitochondrial genome sequence of the black-capped capuchin (Cebus apella).

The phylogenetic relationships of primates have been extensively investigated, but key issues remain unresolved. Complete mitochondrial genome (mitogenome) data have many advantages in phylogenetic analyses, but such data are available for only 46 primate species. In this work, we determined the complete mitogenome sequence of the black-capped capuchin (Cebus apella). The genome was 16,538 bp in size and consisted of 13 protein-coding genes, 22 tRNAs, two rRNAs and a control region. The genome organization, nucleotide composition and codon usage did not differ significantly from those of other primates. The control region contained several distinct repeat motifs, including a putative termination-associated sequence (TAS) and several conserved sequence blocks (CSB-F, E, D, C, B and 1). Among the protein-coding genes, the COII gene had lower nonsynonymous and synonymous substitutions rates while the ATP8 and ND4 genes had higher rates. A phylogenetic analysis using Maximum likelihood and Bayesian methods and the complete mitogenome data for platyrrhine species confirmed the basal position of the Callicebinae and the sister relationship between Atelinae and Cebidae, as well as the sister relationship between Aotinae (Aotus) and Cebinae (Cebus/Saimiri) in Cebidae. These conclusions agreed with the most recent molecular phylogenetic investigations on primates. This work provides a framework for the use of complete mitogenome information in phylogenetic analyses of the Platyrrhini and primates in general.

Autoinduction of RpoS biosynthesis in the biocontrol strain Pseudomonas sp. M18.

The rpoS gene from Pseudomonas sp. M18, which encodes predicted protein (an alternative sigma factor s, sigma(S), or sigma(38)) with 99.5% sequence identity with RpoS from Pseudomonas aeruginosa PAO1, was first cloned. In order to investigate the mechanism of rpoS expression, an rpoS null mutant, named M18S, was constructed with insertion of aacC1 cassette bearing a gentamycin resistance gene. With introduction of a plasmid containing an rpoS'-'lacZ translational fusion (pMERS) to wild-type strain M18 or M18S, it was first found that beta-galactosidase activity expressed in strain M18S (pMERS) decreased to fourfold of that expressed in the strain M18 (pMERS). When strain M18S (pMERS) was introduced with another plasmid pBBS containing the wild-type rpoS gene, its beta-galactosidase expression level was enhanced and almost restored to that in strain M18 (pMERS). Similarly, expression of beta-galactosidase from a chromosomal fusion of the promoter of the wild-type rpoS gene with lacZ (rpoS-lacZ) was enhanced fivefold in the presence of a plasmid with the wild-type rpoS gene. With these findings, it is suggested that RpoS sigma factor may be involved in autoinducing its own gene expression in Pseudomonas sp. M18.