Preparation of nanocellulose and its applications in wound dressing: A review.

Nanocellulose, as a nanoscale polymer material, has garnered significant attention worldwide due to its numerous advantages including excellent biocompatibility, thermal stability, non-toxicity, large specific surface area, and good hydrophilicity. Various methods can be employed for the preparation of nanocellulose. Traditional approaches such as mechanical, chemical, and biological methods possess their own distinct characteristics and limitations. However, with the growing deterioration of our living environment, several green and environmentally friendly preparation techniques have emerged. These novel approaches adopt eco-friendly technologies or employ green reagents to achieve environmental sustainability. Simultaneously, there is a current research focus on optimizing traditional nanocellulose preparation methods while addressing their inherent drawbacks. The combination of mechanical and chemical methods compensates for the limitations associated with using either method alone. Nanocellulose is widely used in wound dressings owing to its exceptional properties, which can accelerate the wound healing process and reduce patient discomfort. In this paper, the principle, advantages and disadvantages of each preparation method of nanocellulose and the research findings in recent years are introduced Moreover, this review provides an overview of the utilization of nanocellulose in wound dressing applications. Finally, the prospective trends in its development alongside corresponding preparation techniques are discussed.

In Vitro Investigation of Gelatin/Polycaprolactone Nanofibers in Modulating Human Gingival Mesenchymal Stromal Cells.

The aesthetic constancy and functional stability of periodontium largely depend on the presence of healthy mucogingival tissue. Soft tissue management is crucial to the success of periodontal surgery. Recently, synthetic substitute materials have been proposed to be used for soft tissue augmentation, but the tissue compatibility of these materials needs to be further investigated. This study aims to assess the in vitro responses of human gingival mesenchymal stromal cells (hG-MSCs) cultured on a Gelatin/Polycaprolactone prototype (GPP) and volume-stable collagen matrix (VSCM). hG-MSCs were cultured onto the GPP, VSCM, or plastic for 3, 7, and 14 days. The proliferation and/or viability were measured by cell counting kit-8 assay and resazurin-based toxicity assay. Cell morphology and adhesion were evaluated by microscopy. The gene expression of collagen type I, alpha1 (COL1A1), α-smooth muscle actin (α-SMA), fibroblast growth factor (FGF-2), vascular endothelial growth factor A (VEGF-A), transforming growth factor beta-1 (TGF-ß1), focal adhesion kinase (FAK), integrin beta-1 (ITG-ß1), and interleukin 8 (IL-8) was investigated by RT-qPCR. The levels of VEGF-A, TGF-ß1, and IL-8 proteins in conditioned media were tested by ELISA. GPP improved both cell proliferation and viability compared to VSCM. The cells grown on GPP exhibited a distinct morphology and attachment performance. COL1A1, α-SMA, VEGF-A, FGF-2, and FAK were positively modulated in hG-MSCs on GPP at different investigation times. GPP increased the gene expression of TGF-ß1 but had no effect on protein production. The level of ITG-ß1 had no significant changes in cells seeded on GPP at 7 days. At 3 days, notable differences in VEGF-A, TGF-ß1, and α-SMA expression levels were observed between cells seeded on GPP and those on VSCM. Meanwhile, GPP showed higher COL1A1 expression compared to VSCM after 14 days, whereas VSCM demonstrated a more significant upregulation in the production of IL-8. Taken together, our data suggest that GPP electrospun nanofibers have great potential as substitutes for soft tissue regeneration in successful periodontal surgery.

Hierarchically Porous Carbon Nanosheets from One-Step Carbonization of Zinc Gluconate for High-Performance Supercapacitors.

Supercapacitors, with high energy density, rapid charge-discharge capabilities, and long cycling ability, have gained favor among many researchers. However, the universality of high-performance carbon-based electrodes is often constrained by their complex fabrication methods. In this study, the common industrial materials, zinc gluconate and ammonium chloride, are uniformly mixed and subjected to a one-step carbonization strategy to prepare three-dimensional hierarchical porous carbon materials with high specific surface area and suitable nitrogen doping. The results show that a specific capacitance of 221 F g-1 is achieved at a current density of 1 A g-1. The assembled symmetrical supercapacitor achieves a high energy density of 17 Wh kg-1, and after 50,000 cycles at a current density of 50 A g-1, it retains 82% of its initial capacitance. Moreover, the operating voltage window of the symmetrical device can be easily expanded to 2.5 V when using Et4NBF4 as the electrolyte, resulting in a maximum energy density of up to 153 Wh kg-1, and retaining 85.03% of the initial specific capacitance after 10,000 cycles. This method, using common industrial materials as raw materials, provides ideas for the simple preparation of high-performance carbon materials and also provides a promising method for the large-scale production of highly porous carbons.

Potential new material for optical fiber: Preparation and characterization of transparent fiber based on natural cellulosic fiber and epoxy.

In order to reduce the dependence on fossil energy products, natural fiber/polymer hybrid composites have been increasingly researched. The high price of the quartz optical fibers and glass optical fibers has greatly inspired researchers to engage in the research on polymer optical fibers. Herein, transparent fibers based on plant fibers were innovatively prepared for the first time by delignification and impregnating epoxy diluted with acetone. The epoxy improved the thermal stability of the fiber without deteriorating its mechanical properties, and also endowed the fiber with the property of transparency. The tensile strength of transparent fibers of three diameters were 34.5, 58.6 and 100.3 MPa, respectively and the corresponding Young's modulus reached 1.1, 1.7 and 2.3 GPa, respectively. In addition, the light-conducting properties of transparent fibers were displayed with a green laser and the fibers displayed good light transmission along the fiber growth direction. Transparent fibers are expected to be used in optical fibers because of their high thermal stability, good mechanical properties and light-conducting properties.

Cyclic tensile strain-induced yes-associated protein activity modulates the response of human periodontal ligament mesenchymal stromal cells to tumor necrosis factor-α.

OBJECTIVES: This study aimed to evaluate the role of yes-associated protein (YAP) in the inflammatory processes induced in human periodontal ligament-derived mesenchymal stromal cells (hPDL-MSCs) by cyclic tensile strain (CTS). DESIGN: hPDL-MSCs from five periodontally healthy individuals were stimulated with 12% CTS and/or TNF-α for 24 h. YAP activity was determined by analyzing the YAP nuclear localization and the target genes expression, using immunofluorescence and qPCR, respectively. Verteporfin was used to inhibit the activation of YAP. The gene expression of interleukin (IL)-6, IL-8, vascular cell adhesion molecule (VCAM)-1, and intercellular adhesion molecule (ICAM)-1 was analyzed by qPCR. RESULTS: In the absence of TNF-α, application of CTS resulted in the nuclear YAP translocation and upregulation of YAP target genes. Verteporfin inhibited the activation of YAP pathway and upregulated the basal expression of IL-6 and IL-8. TNF-α induced the activation of YAP pathway, which was inhibited by verteporfin. However, application of CTS under these conditions diminished TNF-α-induced YAP activation. TNF-α-induced expression of IL-6, VCAM-1, and ICAM-1 was inhibited after the application of CTS. Inhibition of YAP activation by verteporfin diminished TNF-α-induced gene expression of IL-6, VCAM-1, and ICAM-1, and under these conditions no inhibitory effect of CTS on these parameters was observed. CONCLUSIONS: YAP is at least partially involved in the CTS-activated mechanotransduction pathway. The effects of CTS and YAP on the inflammatory responses depend on the inflammatory environment. A better understanding of the inflammatory modulation by mechanical stress may help improve the orthodontic strategies, especially in the patient with periodontitis.

Wood-Derived High-Mass-Loading MnO2 Composite Carbon Electrode Enabling High Energy Density and High-Rate Supercapacitor.

The simple design of a high-energy-density device with high-mass-loading electrode has attracted much attention but is challenging. Manganese oxide (MnO2 ) with its low cost and excellent electrochemical performance shows high potential for practical application in this regard. Hence, the high-mass-loading of the MnO2 electrode with wood-derived carbon (WC) as the current collector is reported through a convenient hydrothermal reaction for high-energy-density devices. Benefiting from the high-mass-loading of the MnO2 electrode (WC@MnO2 -20, ≈14.1 mg cm-2 ) and abundant active sites on the surface of the WC hierarchically porous structure, the WC@MnO2 -20 electrode shows remarkable high-rate performance of areal/specific capacitance ≈1.56 F cm-2 /45 F g-1 , compared to the WC electrode even at the high density of 20 mA cm-2 . Furthermore, the obtained symmetric supercapacitor exhibits high areal/specific capacitances of 3.62 F cm-2 and 87 F g-1 at 1.0 mA cm-2 and high energy densities of 0.502 mWh cm-2 /12.2 Wh kg-1 with capacitance retention of 75.2% after 10 000 long-term cycles at 20 mA cm-2 . This result sheds light on a feasible design strategy for high-energy-density supercapacitors with the appropriate mass loading of active materials and low-tortuosity structural design while also encouraging further investigation into electrochemical storage.

Intertwined carbon networks derived from Polyimide/Cellulose composite as porous electrode for symmetrical supercapacitor.

Designing intertwined porous structure is highly desirable to improve the electrochemical performance of carbon materials for supercapacitor. In this contribution, three-dimensional (3D) carbonized polyimide/cellulose (CPC) composite is fabricated via a facile "one-step" carbonization, in which cellulose as cross-linked agent is capable of modulating the molecular structure of polyamic acid, thus ensuring the formation of intertwined porous networks in the obtained carbon skeleton. Benefitting from the high specific surface area (951 m2 g-1) and uniformly distributed pores, the optimized CPC-5 electrode exhibits an outstanding specific capacitance of 300F g-1 in 6.0 M KOH electrolyte. More impressively, the CPC-5 based symmetrical supercapacitor affords a high energy density of 22.6 Wh kg-1 at power density of 800 W kg-1, as well as an exceptional capacitance retention of 91.4% after 10,000 cycles. This work affords an effective strategy to yield a promising polyimide derived carbon material for high-performance supercapacitors.

Cyclic tensile strain affects the response of human periodontal ligament stromal cells to tumor necrosis factor-α.

OBJECTIVES: Orthodontic treatment in adult patients predisposed to mild or severe periodontal disease is challenging for orthodontists. Orthodontic malpractice or hyper-occlusal forces may aggravate periodontitis-induced destruction of periodontal tissues, but the specific mechanism remains unknown. In the present study, the combined effect of mechanical stress and tumor necrosis factor (TNF)-α on the inflammatory response in human periodontal ligament stromal cells (hPDLSCs) was investigated. MATERIALS AND METHODS: hPDLSCs from 5 healthy donors were treated with TNF-α and/or subjected to cyclic tensile strain (CTS) of 6% or 12% elongation with 0.1 Hz for 6- and 24 h. The gene expression of interleukin (IL)-6, IL-8 and cell adhesion molecules VCAM and ICAM was analyzed by qPCR. The protein levels of IL-6 and IL-8 in conditioned media was measured by ELISA. The surface expression of VCAM-1 and ICAM-1 was quantified by immunostaining followed by flow cytometry analysis. RESULTS: TNF-α-induced IL-6 gene and protein expression was inhibited by CTS, whereas TNF-α-induced IL-8 expression was decreased at mRNA expression level but enhanced at the protein level in a magnitude-dependent manner. CTS downregulated the gene expression of VCAM-1 and ICAM-1 under TNF-α stimulation, but the downregulation of the surface expression analyzed by flow cytometry was observed chiefly for VCAM-1. CONCLUSIONS: Our findings show that mechanical force differentially regulates TNF-α-induced expression of inflammatory mediators and adhesion molecules at the early stage of force application. The effect of cyclic tensile strain is complex and could be either anti-inflammatory or pro-inflammatory depending on the type of pro-inflammatory mediators and force magnitude. CLINICAL RELEVANCE: Orthodontic forces regulate the inflammatory mediators of periodontitis. The underlying mechanism may have significant implications for future strategies of combined periodontal and orthodontic treatment.

Hydrogen-Bonding-Aided Fabrication of Wood Derived Cellulose Scaffold/Aramid Nanofiber into High-Performance Bulk Material.

Preparing a lightweight yet high-strength bio-based structural material with sustainability and recyclability is highly desirable in advanced applications for architecture, new energy vehicles and spacecraft. In this study, we combined cellulose scaffold and aramid nanofiber (ANF) into a high-performance bulk material. Densification of cellulose microfibers containing ANF and hydrogen bonding between cellulose microfibers and ANF played a crucial role in enhanced physical and mechanical properties of the hybrid material. The prepared material showed excellent tensile strength (341.7 MPa vs. 57.0 MPa for natural wood), toughness (4.4 MJ/m3 vs. 0.4 MJ/m3 for natural wood) and Young's modulus (24.7 GPa vs. 7.2 GPa for natural wood). Furthermore, due to low density, this material exhibited a superior specific strength of 285 MPa·cm3·g-1, which is remarkably higher than some traditional building materials, such as concrete, alloys. In addition, the cellulose scaffold was infiltrated with ANFs, which also improved the thermal stability of the hybrid material. The facile and top-down process is effective and scalable, and also allows one to fully utilize cellulose scaffolds to fabricate all kinds of advanced bio-based materials.

Arrangement of boundary electrodes for detection of frontal lobe disease with electrical impedance tomography.

Purpose: Caused by brain trauma or blood vessel abnormality, intracerebral hemorrhage and secondary ischemia have become prevalent and severe neurological diseases. The timely and accurate detection of disease is essential for the recovery of patients. As an emerging visualization technique, electrical impedance tomography (EIT) offers an alternative. It is able to reconstruct the conductivity distribution that reflects the pathological variation of human tissue. Approach: In the EIT-based detection, electrodes are usually in uniform arrangement, which may be not suitable in some conditions. To enhance sensitivity in the region of interest, EIT with a novel offset arrangement of boundary electrodes is proposed to image a simulated frontal lobe hemorrhage and secondary ischemia. To cope with the ill-posed inverse problem, the L1 regularization method is developed during the reconstruction. In addition, the impact of noise with a signal-to-noise ratio of 56 dB is studied. Results: Compared with the traditional uniform electrode arrangement, the results demonstrate that EIT with the proposed offset arrangement of electrodes is more advantageous for imaging frontal lobe disease. Conclusions: The proposed offset arrangement of electrodes is superior to the traditional uniform arrangement in imaging frontal lobe disease, especially under the impact of noise.

Sparse image reconstruction of intracerebral hemorrhage with electrical impedance tomography.

Purpose: Intracerebral hemorrhage (ICH) is a common disease that is known for its high morbidity, high mortality, and high disability. The fast and accurate detection of ICH is essential for the acute care of patients. Electrical impedance tomography (EIT) offers an alternative with which pathological tissues can be detected by reconstructing conductivity variation. Nevertheless, the sensitive field of EIT is greatly affected by medium distribution, which is referred to as soft-field effect. In addition, the image reconstruction is a severely ill-posed inverse problem. Furthermore, due to the low conductivity of skull, the sensitivity in the sensing area is extremely low. Therefore, the reconstruction of ICH with EIT is great challenge. Approach: A sparse image reconstruction method is proposed for EIT to visualize the conductivity variation caused by ICH. To reduce the impact of soft-field effect, the normalization of sensitivity distribution is conducted for monolayer and three-layer head model. In addition, a constrained sparse L 1 -norm minimization model is developed for the image reconstruction. Augmented Lagrangian multiplier method and alternating minimization scheme are adopted to solve the proposed model. Results: The results show that the sensitivity in the sensing area is largely enhanced. Numerical simulation based on monolayer head model and three-layer head model is respectively carried out. Both the reconstructed images and the quantitative evaluations show that image reconstructed by the proposed method is much better than that reconstructed by traditional Tikhonov method. The reconstructions evaluated under the impact of noise also show that the proposed method has superior anti-noise performance. Conclusions: With the proposed method, the quality of the reconstructed image would be greatly improved. It is an effective approach for imaging ICH with EIT technique.