3D poly(L-lactic acid) fibrous sponge with interconnected porous structure for bone tissue scaffold.

Large bone defects, often resulting from trauma and disease, present significant clinical challenges. Electrospun fibrous scaffolds closely resembling the morphology and structure of natural ECM are highly interested in bone tissue engineering. However, the traditional electrospun fibrous scaffold has some limitations, including lacking interconnected macropores and behaving as a 2D scaffold. To address these challenges, a sponge-like electrospun poly(L-lactic acid) (PLLA)/polycaprolactone (PCL) fibrous scaffold has been developed by an innovative and convenient method (i.e., electrospinning, homogenization, progen leaching and shaping). The resulting scaffold exhibited a highly porous structure (overall porosity = 85.9 %) with interconnected, regular macropores, mimicking the natural extracellular matrix. Moreover, the incorporation of bioactive glass (BG) particles improved the hydrophilicity (water contact angle = 79.7°) and biocompatibility and promoted osteoblast cell growth. In-vitro 10-day experiment revealed that the scaffolds led to high cell viability. The increment of the proliferation rates was 195.4 % at day 7 and 281.6 % at day 10. More importantly, Saos-2 cells could grow, proliferate, and infiltrate into the scaffold. Therefore, this 3D PLLA/PCL with BG sponge holds great promise for bone defect repair in tissue engineering applications.

Hierarchical porous PLLA/ACP fibrous membrane towards bone tissue scaffold.

Electrospun fibres have emerged as vital components in developing tissue engineering scaffolds. Calcium phosphate-based materials, renowned for their bioactivity and biocompatibility, have garnered considerable attention in biomedical applications. This study focuses on the incorporation of amorphous calcium phosphate (ACP) nanoparticles into poly(L-lactic acid) (PLLA) to produce electrospun PLLA/ACP fibrous membranes. Subsequent treatment with acetone yielded a hierarchical porous structure, boasting an ultra-high surface area of 94.7753 ± 0.3884 m2/g. The ACP nanoparticles, initially encapsulated by PLLA, were exposed on the fibre surface after acetone treatment. Furthermore, the porous PLLA/ACP fibrous membrane exhibited superior mechanical properties (Young's modulus = 0.148 GPa, tensile strength = 3.05 MPa) and enhanced wettability. In a 7-day in vitro cell culture with human osteoblast-like cells, the porous PLLA/ACP fibrous membrane demonstrated a significant improvement in osteoblast adhesion and proliferation, with a proliferation rate increase of 252.0% and 298.7% at day 4 and day 7, respectively. These findings underscore the potential of the porous PLLA/ACP fibrous membrane as a promising candidate for bone tissue scaffolds.

Nanoarchitectonics toward Full Coverage of CdZnS Nanospheres by Layered Double Hydroxides for Enhanced Visible-Light-Driven H2 Evolution.

Nanoarchitectonics of semiconductors shed light on efficient photocatalytic hydrogen evolution by precisely controlling the surface microenvironment of cocatalysts. Taking cadmium zinc sulfide (CZS) nanoparticles as a target, the spontaneous modifications are conducted by interactions between surface Cd2+ /Zn2+ atoms and thiol groups in thioglycolic acid. The capping ligand impacts the semiconductor surface with a negative electronic environment, contributing to the full coverage of CZS by nickel-cobalt hydroxides (NiCo-LDHs) cocatalysts. The obtained core-shell CZS@NiCo-LDHs, possessing a shell thickness of ≈20 nm, exhibits a distinguished topology (SBET  = 87.65m2  g-1 ), long surface carrier lifetime, and efficient charge-hole separation. Further photocatalytic hydrogen evaluation demonstrates an enhanced H2 evolution rate of 18.75 mmol g-1  h-1 with an apparent quantum efficiency of 16.3% at 420 nm. The recorded catalytic performance of the core-shell sample is 44.6 times higher than that of pure CZS nanospheres under visible light irradiation. Further density functional theory simulations indicate that sulfur atoms play the role of charge acceptor and surface Ni/Co atoms are electron donors, as well as a built-in electric field effect can be established. Altogether, this work takes advantage of strong S affinity from surface metal atoms, revealing the interfacial engineering toward improved visible-light-driven photocatalytic hydrogen evolution (PHE) activity.

A Framework for Determining the Optimal Vibratory Frequency of Graded Gravel Fillers Using Hammering Modal Approach and ANN.

To address the uncertainty of optimal vibratory frequency fov of high-speed railway graded gravel (HRGG) and achieve high-precision prediction of the fov, the following research was conducted. Firstly, commencing with vibratory compaction experiments and the hammering modal analysis method, the resonance frequency f0 of HRGG fillers, varying in compactness K, was initially determined. The correlation between f0 and fov was revealed through vibratory compaction experiments conducted at different vibratory frequencies. This correlation was established based on the compaction physical-mechanical properties of HRGG fillers, encompassing maximum dry density ρdmax, stiffness Krd, and bearing capacity coefficient K20. Secondly, the gray relational analysis algorithm was used to determine the key feature influencing the fov based on the quantified relationship between the filler feature and fov. Finally, the key features influencing the fov were used as input parameters to establish the artificial neural network prediction model (ANN-PM) for fov. The predictive performance of ANN-PM was evaluated from the ablation study, prediction accuracy, and prediction error. The results showed that the ρdmax, Krd, and K20 all obtained optimal states when fov was set as f0 for different gradation HRGG fillers. Furthermore, it was found that the key features influencing the fov were determined to be the maximum particle diameter dmax, gradation parameters b and m, flat and elongated particles in coarse aggregate Qe, and the Los Angeles abrasion of coarse aggregate LAA. Among them, the influence of dmax on the ANN-PM predictive performance was the most significant. On the training and testing sets, the goodness-of-fit R2 of ANN-PM all exceeded 0.95, and the prediction errors were small, which indicated that the accuracy of ANN-PM predictions was relatively high. In addition, it was clear that the ANN-PM exhibited excellent robust performance. The research results provide a novel method for determining the fov of subgrade fillers and provide theoretical guidance for the intelligent construction of high-speed railway subgrades.

Simultaneous High Ionic Conductivity and Lithium-Ion Transference Number in Single-Ion Conductor Network Polymer Enabling Fast-Charging Solid-State Lithium Battery.

Developing solid-state electrolyte with sufficient ionic conduction and flexible-intimate interface is vital to advance fast-charging solid-state lithium batteries. Solid polymer electrolyte yields the promise of interfacial compatibility, yet its critical bottleneck is how to simultaneously achieve high ionic conductivity and lithium-ion transference number. Herein, single-ion conducting network polymer electrolyte (SICNP) enabling fast charging is proposed to positively realize fast lithium-ion locomotion with both high ionic conductivity of 1.1 × 10-3 S cm-1 and lithium-ion transference number of 0.92 at room temperature. Experimental characterization and theoretical simulations demonstrate that the construction of polymer network structure for single-ion conductor not only facilitates fast hopping of lithium ions for boosting ionic kinetics, but also enables a high dissociation level of the negative charge for lithium-ion transference number close to unity. As a result, the solid-state lithium batteries constructed by coupling SICNP with lithium anodes and various cathodes (e.g., LiFePO4 , sulfur, and LiCoO2 ) display impressive high-rate cycling performance (e.g., 95% capacity retention at 5 C for 1000 cycles in LiFePO4 |SICNP|lithium cell) and fast-charging capability (e.g., being charged within 6 min and discharged over than 180 min in LiCoO2 |SICNP|lithium cell). Our study provides a prospective direction for solid-state electrolyte that meets the lithium-ion dynamics for practical fast-charging solid-state lithium batteries.

FAPbBr3 Perovskite Nanocrystals Embedded in Poly(L-lactic acid) Nanofibrous Membranes for Enhanced Air and Water Stability.

Formamidinium lead bromide (FAPbBr3) nanocrystals have emerged as a powerful platform for optoelectronic applications due to their pure green photoluminescence (PL). However, their low colloidal stability under storage and operation reduces the potential use of FAPbBr3 perovskite nanocrystals (PeNCs) in various applications. In this study, we prepared the poly(L-lactic acid) (PLLA) nanofibrous membrane embedded with FAPbBr3 perovskite nanocrystals by electrospinning the perovskite and PLLA precursor solution. This is a simple and low-cost technique for the direct confinement of nano-sized functional materials in the continuous polymer nanofibres. PLLA as a polymer matrix provided a high surface framework to fully encapsulate the perovskite NCs. In addition, we found that FAPbBr3 PeNCs crystallize spontaneously inside the PLLA nanofibre. The resultant PLLA-FAPbBr3 nanofibrous membranes were stable and remained in the water for about 45 days without any evident decomposition. The results of this research support the idea of new possibilities for the production of air-stable FAPbBr3 PeNCs by forming a composite with PLLA polymer. The authors believe this study is a new milestone in the development of highly stable metal halide perovskite-based nanofibres, which allow for potential use in lasers, waveguides, and flexible energy harvesters.

Heterogeneous porous PLLA/PCL fibrous scaffold for bone tissue regeneration.

Bone tissue engineering has become one of the most promising therapeutic methods to treat bone defects. A suitable scaffolding material to regenerate new bone tissues should have a high specific surface area, high porosity and a suitable surface structure which benefit cell attachment, proliferation, and differentiation. In this study, an acetone post-treatment strategy was developed to generate heterogeneous structure. After PLLA/PCL nanofibrous membranes were electrospun and collected, they were treated with acetone to generate a highly porous structure. Meanwhile, part of PCL was extracted from the fibre and enriched on the fibre surface. The cell affinity of the nanofibrous membrane was verified by human osteoblast-like cells assay. The proliferation rate of heterogeneous samples increased 190.4 %, 265.5 % and 137.9 % at day 10 compared with pristine samples. These results demonstrated that the heterogeneous PLLA/PCL nanofibrous membranes could enhance osteoblast adhesion and proliferation. With high surface area (average surface area 36.302 m2/g) and good mechanical properties (average Young's modulus 1.65 GPa and average tensile strength 5.1 MPa), the heterogeneous PLLA/PCL membrane should have potential applications in the field of bone regeneration.

Revisable and high-strength wheel-spun alginate/graphene oxide based fibrous rods towards a flexible and biodegradable rib internal fixation system.

The intramedullary splint insertion fixation system is the mainstream clinical solution to severe rib fractures. However, the titanium alloy scaffolds have limitations in biocompatibility, flexibility and complexity of surgeries. Here we present a revisable wheel-spun alginate (Alg)/graphene oxide (GO)-based fibrous rod as a potential alternative for a rib internal fixation system. The reversible fusion and fission capability was obtained by optimized Alg/GO blended spinning and GO coating post-treatment. The mechanical performance of the demonstrated rod samples matches the properties of the human rib. A self-designed cubic matrix was used to conduct in situ cell culture. In vitro evaluation not only confirms the cell viability and migration on the fibers' surface, but also investigated the degradation and fission performance of fibrous rods. With a simple, minimally invasive implantation and controlled swelling, Alg/GO fibrous rods are able to tightly fix the rib fracture wound while maintaining sufficient flexibility.

Electrospun Silk Fibroin/Polylactic-co-glycolic Acid/Black Phosphorus Nanosheets Nanofibrous Membrane with Photothermal Therapy Potential for Cancer.

Photothermal therapy is a promising treating method for cancers since it is safe and easily controllable. Black phosphorus (BP) nanosheets have drawn tremendous attention as a novel biodegradable thermotherapy material, owing to their excellent biocompatibility and photothermal properties. In this study, silk fibroin (SF) was used to exfoliate BP with long-term stability and good solution-processability. Then, the prepared BP@SF was introduced into fibrous membranes by electrospinning, together with SF and polylactic-co-glycolic acid (PLGA). The SF/PLGA/BP@SF membranes had relatively smooth and even fibers and the maximum stress was 2.92 MPa. Most importantly, the SF/PLGA/BP@SF membranes exhibited excellent photothermal properties, which could be controlled by the BP@SF content and near infrared (NIR) light power. The temperature of SF/PLGA/BP@SF composite membrane was increased by 15.26 °C under NIR (808 nm, 2.5 W/cm2) irradiation for 10 min. The photothermal property of SF/PLGA/BP@SF membranes significantly killed the HepG2 cancer cells in vitro, indicating its good potential for application in local treatment of cancer.

Empagliflozin Ameliorates Diabetic Cardiomyopathy via Attenuating Oxidative Stress and Improving Mitochondrial Function.

Diabetic cardiomyopathy (DCM) is considered to be a critical contributor to the development of heart failure. Empagliflozin (EMPA), a sodium-glucose cotransporter 2 inhibitor, has been shown to prevent cardiovascular events and reduce the incidence of heart failure in randomized clinical trials. However, the mechanism of how EMPA prevents DCM is poorly understood. To study the potential mechanisms involved in the therapeutic effects of EMPA, we assessed the protective effects of EMPA on myocardial injury in type 2 diabetic db/db mice and H9C2 cardiomyocytes. 9-10-week-old male db/db mice were treated with EMPA (10 mg/kg) via oral gavage daily for 20 weeks. Afterward, cardiac function of treated mice was evaluated by echocardiography, and pathological changes in heart tissues were determined by histopathological examination and western blot assay. EMPA markedly reduced blood glucose levels, improved insulin tolerance, and enhanced insulin sensitivity of db/db mice. In addition, EMPA significantly prevented cardiac dysfunction, inhibited cardiac hypertrophy and fibrosis, and reduced glycogen deposition in heart tissues. Furthermore, EMPA improved diabetes-induced oxidative stress and mitochondrial dysfunction in both heart tissues of db/db mice and palmitate exposed H9C2 cells. EMPA significantly increased the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and its downstream genetic targets in cardiac tissue of type 2 diabetic db/db mice and H9C2 cells. EMPA also downregulated the expression of mitochondrial fission-related proteins and upregulated the expression of mitochondrial fusion-related proteins. Collectively, these findings indicate that EMPA may prevent DCM via attenuating oxidative stress and improving mitochondrial function in heart tissue.

Tunable Graphene/Nitrocellulose Temperature Alarm Sensors.

Tunable temperature alarm sensors were prepared using multilayer graphene and nitrocellulose (NC) to reliably monitor early high temperature risks. The graphene/NC alarm sensor keeps in a state of electrical insulation, however, turns electrically conductive at high temperatures, such as encountering a flame attack. Its response time is limited to only a few seconds because of a quick chemical reaction of NC. The 90% graphene/NC (wt % ratio 1:9) composite alarm sensor stably remains insulated at an ambient temperature of 200 °C, resulting in a satisfactory responsive temperature (232 °C), instant response time (4.4 s), and sustained working time in the flame below the ignition temperature of most combustibles. Furthermore, the response temperature and time of the alarm sensor can be tuned by graphene/NC ratios to reduce the fire risk of various combustible materials in different fire-prone scenarios and thus has promising applications in both indoor and outdoor environments. The sensor has also proven to work in the form of paint, wallpaper, and other composites due to its superior flame retardancy property, as well as under extreme conditions (i.e., underwater and vacuum).

Functionalized Fiber-Based Strain Sensors: Pathway to Next-Generation Wearable Electronics.

Wearable strain sensors are arousing increasing research interests in recent years on account of their potentials in motion detection, personal and public healthcare, future entertainment, man-machine interaction, artificial intelligence, and so forth. Much research has focused on fiber-based sensors due to the appealing performance of fibers, including processing flexibility, wearing comfortability, outstanding lifetime and serviceability, low-cost and large-scale capacity. Herein, we review the latest advances in functionalization and device fabrication of fiber materials toward applications in fiber-based wearable strain sensors. We describe the approaches for preparing conductive fibers such as spinning, surface modification, and structural transformation. We also introduce the fabrication and sensing mechanisms of state-of-the-art sensors and analyze their merits and demerits. The applications toward motion detection, healthcare, man-machine interaction, future entertainment, and multifunctional sensing are summarized with typical examples. We finally critically analyze tough challenges and future remarks of fiber-based strain sensors, aiming to implement them in real applications.

Ultrasensitive Label-Free DNA Detection Based on Solution-Gated Graphene Transistors Functionalized with Carbon Quantum Dots.

Developing highly sensitive, reliable, cost-effective label-free DNA biosensors is challenging with traditional fluorescence, electrochemical, and other techniques. Most conventional methods require labeling fluorescence, enzymes, or other complex modification. Herein, we fabricate carbon quantum dot (CQD)-functionalized solution-gated graphene transistors for highly sensitive label-free DNA detection. The CQDs are immobilized on the surface of the gate electrode through mercaptoacetic acid with the thiol group. A single-stranded DNA (ssDNA) probe is immobilized on CQDs by strong π-π interactions. The ssDNA probe can hybridize with the ssDNA target and form double-stranded DNA, which led to a shift of Dirac voltage and the channel current response. The limit of detection can reach 1 aM which is 2-5 orders of magnitude lower than those of other methods reported previously. The sensor also exhibits a good linear range from 1 aM to 0.1 nM and has good specificity. It can effectively distinguish one-base mismatched target DNA. The response time is about 326 s for the 1 aM target DNA molecules. This work provides good perspectives on the applications in biosensors.

Hierarchical Porous Recycled PET Nanofibers for High-Efficiency Aerosols and Virus Capturing.

Plastic crisis, especially for poly(ethylene terephthalate) (PET) bottles, has been one of the greatest challenges for the earth and human beings. Processing recycled PET (rPET) into functional materials has the dual significance of both sustainable development and economy. Providing more possibilities for the engineered application of rPET, porous PET fibers can further enhance the high specific surface area of electrospun membranes. Here, we use a two-step strategy of electrospinning and postprocessing to successfully control the surface morphology of rPET fibers. Through a series of optical and thermal characterizations, the porous morphology formation mechanism and crystallinity induced by solvents of rPET fibers were discussed. Then, this work further investigated both PM2.5 air pollutants and protein filtration performance of rPET fibrous membrane. The high capture capability of rPET membrane demonstrated its potential application as an integrated high-efficiency aerosol filtering solution.

Photo-Patternable, High-Speed Electrospun Ultrafine Fibers Fabricated by Intrinsically Negative Photosensitive Polyimide.

This work describes polyimide (PI) ultrafine fibrous membranes (UFMs) with aligned fibrous structures, fabricated via the high-speed electrospinning procedure. Organo-soluble intrinsically photosensitive PI is utilized as the fiber-forming agent. The effects of different rotating speeds on the fiber morphology and properties are studied. The aligned UFMs possess hydrophobicity, favorable optical properties, and improved deformation durability. The extension strength of the UFMs reinforces obviously with the increased rotating speed and reaches the maximum of 9.18 MPa at 2500 rpm. In addition, due to the photo-cross-link nature of the PI resin, the UFMs present lithography capability, which can obtain micro-sized patterns on aluminum substrates, and even part of the fibrous structure was retained after development. This work shows promise in manufacturing fiber-based photolithographic hierarchical structures on flexible substrates, which exhibit potential in achieving multiple functions on fiber-based electronic devices.

Hierarchical porous silk fibroin/poly(L-lactic acid) fibrous membranes towards vascular scaffolds.

Fibrous membranes played an important role to prepare tubular scaffolds for muscular artery regeneration. In this study, a strategy has been developed to combine silk fibroin (SF) with highly porous electrospun poly(L-lactic acid) (PLLA) fibrous membrane towards vascular scaffolds. After PLLA fibres were electrospun and collected, they were immersed into acetone to generate a porous structure with ultra-high surface area. While the pores on PLLA fibres were fulfilled with SF solution and dried, SF was coated uniformly and tightly on PLLA fibres. A multi-layer tubular structure of the tunica media was simulated by winding and stacking a strip of electrospun fibrous membrane. In vitro viability and morphology studies of A7r5 smooth muscle cells were undertaken for up to 14 days. Because the hydrophilicity of SF/PLLA composite fibres were improved dramatically, it had a positive effect on cell adhesion rate (97%) and proliferation (64.4%). Moreover, good cell morphology was observed via a multiphoton laser confocal microscope on SF/PLLA bioactive materials. These results demonstrated that the hierarchical porous SF/PLLA fibrous membranes are promising off-the-shelf scaffolds for muscular artery regeneration.

Polydopamine-assisted grafting of chitosan on porous poly (L-lactic acid) electrospun membranes for adsorption of heavy metal ions.

In this study, a versatile method for the manufacturing of chitosan-grafted porous poly (L-lactic acid) (P-PLLA) nanofibrous membrane by using polydopamine (PDA) as an intermediate layer has been developed. P-PLLA fibres were electrospun and collected as nano/micro fibrous membranes. Highly porous fibres could serve as a substrate for chitosan to adsorb heavy metal ions. Moreover, PDA was used to modify P-PLLA surface to increase the coating uniformity and stability of chitosan. Due to the very high surface area of P-PLLA membranes and abundant amine groups of both PDA and chitosan, the fabricated membranes were utilized as adsorbent for removal of copper (Cu2+) ions from the wastewater. The adsorption capability of Cu2+ ions was examined with respect to the PDA polymerization times, pH, initial metal ion concentration and time. Finally, the equilibrium adsorption data of chitosan-grafted membranes fitted well with the Langmuir isotherm with the maximum adsorption capacity of 270.27 mg/g.

Electrospun highly porous poly(L-lactic acid)-dopamine-SiO2 fibrous membrane for bone regeneration.

Electrospinning has been widely used to fabricate polymer fibrous scaffolds for bone tissue engineering because of their highly porous structures. In order to improve the biocompatibility of polymer scaffolds, some nano particles have been introduced into electrospun fibres. For example, silica nanoparticles (SiNPs), with high surface area and good biocompatibility, have been used for bone tissue engineering for better bone cell attachment. In this work, porous poly(L-lactic acid) (PLLA) fibrous membrane with high surface area was fabricated by electrospinning and post-treatment process. The membrane can serve as substrates of SiNPs for bone tissue engineering. Dopamine (DOP) was applied to modify the surface of PLLA fibres, which improved the coating strength of SiNPs on PLLA fibres. SiNP coating significantly improved the mechanical properties and hydrophilicity of PLLA/DOP/SiNP composite membranes. As a result of SiNPs coating, PLLA/DOP/SiNP membrane exhibited better cellular biocompatibility, more cell attachment and proliferation. These results demonstrate that porous PLLA/DOP/SiNP composite membrane with high surface area has high potential for periosteum in the field of bone regeneration applications.

Ultrafast bone-like apatite formation on highly porous poly(l-lactic acid)-hydroxyapatite fibres.

In order to provide a favourable environment for living bone formation, it is an essential condition to grow bone-like apatite layer at the interface between the tissue-implant and its surrounding tissues. Inspired by the chemical composition and the nano porous structure of natural bones, we developed an ultrafast and accessible route to accelerate effectively the formation of bone-like apatite on the surface of porous poly(l-lactic acid)-hydroxyapatite (PLLA-HA) composite fibres in 5 times simulated body fluid (5SBF). The key of the method lays in successful exposure of HA nanoparticles on the surface of PLLA fibres by acetone treatment of electrospun PLLA-HA nano/micro fibres. The recrystallization of PLLA chains uncovers more HA nanoparticles on the surface of every fibre which provide nucleation sites for calcium and phosphate ions. After only 2 h of immersing in 5SBF, a full layer of apatite completely covered on the surface of porous PLLA-HA fibres. The results indicate that HA nanoparticles on porous fibre surface can accelerate the kinetic deposition of apatite on fibre surface. Biological in vitro cell culture with human osteoblast-like cell for up to 7 days demonstrates that the incorporation of HA nanoparticles on the surface of porous PLLA fibrous membranes leads to significant enhance osteoblast adhesion and proliferation. The route can open avenues for development of fibrous PLLA biomaterials for hard tissue repair and substitution.

Biomimetic Presentation of Cryptic Ligands via Single-Chain Nanogels for Synergistic Regulation of Stem Cells.

Dynamic controlling the nanoscale presentation of synergistic ligands to stem cells by biomimetic single-chain materials can provide critical insights to understand the molecular crosstalk underlying cells and their extracellular matrix. Here, a stimuli-responsive single-chain macromolecular nanoregulator with conformational dynamics is fabricated based on an advanced scale-up single polymeric chain nanogel (SCNG). Such a carefully designed SCNG is capable of mediating a triggered copresentation of the master and cryptic ligands in a single molecule to elicit the synergistic crosstalk between different intracellular signaling pathways, thereby considerably boosting the bioactivity of the presented ligands. This controllable nanoswitching-on of cell-adhesive ligands' presentation allows the regulation of cell adhesion and fate from molecular scale. The modular nature of this synthetic macromolecular nanoregulator makes it a versatile nanomaterial platform to assist basic and fundamental studies in a wide array of research topics.