Dynamic Pluronic F127 Crosslinking Enhancement of Biopolymeric Nanocomposites for Piezo-Triboelectric Single-Hybrid Nanogenerators and Self-Powered Sensors.

Biomechanical and nanomechanical energy harvesting systems have gained a wealth of interest, resulting in a plethora of research into the development of biopolymeric-based devices as sustainable alternatives. Piezoelectric, triboelectric, and hybrid nanogenerator devices for electrical applications are engineered and fabricated using innovative, sustainable, facile-approach flexible composite films with high performance based on bacterial cellulose and BaTiO3 , intrinsically and structurally enhanced by Pluronic F127, a micellar cross-linker. The voltage and current outputs of the modified versions with multiwalled carbon nanotube as a conductivity enhancer and post-poling effect are 38 V and 2.8 µA cm-2 , respectively. The multiconnective devices' power density can approach 10 µW cm-2 . The rectified output power is capable of charging capacitors, driving light-emitting diode lights, powering a digital watch and interfacing with a commercial microcontroller board to operate as a piezoresistive force sensor switch as a proof of concept. Magnetoelectric studies show that the composites have the potential to be incorporated into magnetoelectric systems. The biopolymeric composites prove to be desirable candidates for multifunctional energy harvesters and electronic devices.

MoNP-doped Defective Carbon Fibers with Bark-like Nanosurface as Effective Bifunctional Electrocatalysts for Zn-air Batteries.

The flexible air electrode with high oxygen electrocatalytic performance and outstanding stability under various deformations plays a vital role in high-performance flexible Zn-air batteries (ZABs). Herein, a self-supported Mo, N, and P co-doped carbon cloth (CC) denoted as MoNP@CC with bark-like surface structure is fabricated by a facile two-step approach via a one-pot method and pyrolysis. The surface of the electrode shows a nanoscale "rift valley" and uniformly distributed active sites. Taking advantage of the nano-surface as well as transition metal and heteroatom doping, the self-supported electrocatalysis air electrode exhibits considerable oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) performance in terms of low overpotential (388 mV at 10 mA cm-2) for OER and a much positive potential (0.74 V) at 1.0 mA cm-2 for ORR. Furthermore, MoNP@CC is further used for the flexible ZAB to demonstrate its practical application. The MoNP@CC-based ZAB displays a good cycling performance for 2800 min and an open-circuit voltage of 1.44 V. This work provides a new approach to the construction of a high-performance, self-supported electrocatalysis electrode used for a flexible energy storage device.

Hydrogel transformed from sandcastle-worm-inspired powder for adhering wet adipose surfaces.

Normally, hydrogel adhesives do not perform well on adipose matters that are covered with bodily fluids. Besides, the maintenance of high extensibility and self-healing ability in fully swollen state still remains challenging. Based on these concerns, we reported a sandcastle-worm-inspired powder, which was made of tannic acid-functionalized cellulose nanofiber (TA-CNF), polyacrylic acid (PAA) and polyethyleneimine (PEI). The obtained powder can rapidly absorb diverse bodily fluids and transform into a hydrogel, displaying fast (＜3 s), self-strengthening and repeatable wet adhesion to adipose tissues. Due to the dense physically cross-linked network, the formed hydrogel still showed excellent extensibility (∼14 times) and self-healing ability after being immersed in water. Moreover, excellent hemostasis, antibacterial ability and biocompatibility make it suitable for numerous biomedical applications. With combined advantages of powders and hydrogels, such as good adaptability to irregular sites, efficient drug loading capacity and tissue affinity, the sandcastle-worm-inspired powder offers significant promise as tissue adhesive and repair materials. This work may open new avenues for designing high-performance bioadhesives with efficient and robust wet adhesiveness to adipose tissues.

Scalable functionalized liquid crystal elastomer fiber soft actuators with multi-stimulus responses and photoelectric conversion.

Liquid crystal elastomer (LCE) fibers exhibit large deformation and reversibility, making them an ideal candidate for soft actuators. It is still challenging to develop a scalable strategy and endow fiber actuators with photoelectric functions to achieve tailorable photo-electro-thermal responsiveness and rapid large actuation deformation. Herein, we fabricated a multiresponsive actuator that consists of LCE long fibers obtained by continuous dry spinning and further coated it with polydopamine (PDA)-modified MXene ink. The designed PDA@MXene-integrated LCE fiber is used for shape-deformable and multi-trigger actuators that can be photo- and electro-thermally actuated. The proposed LCE fiber actuator combines an excellent photothermal and long-term electrically conductive PDA@MXene and a shape-morphing LCE fiber, enabling their robust mechanical flexibility, multiple fast responses (∼0.4 s), and stable and large actuation deformation (∼60%). As a proof-of-concept, we present near-infrared light-driven artificial muscle that can lift 1000 times the weight and an intelligent circuit switch with stable controllability and fast responsiveness (∼0.1 s). Importantly, an adaptive smart window system that integrates light-driven energy harvesting/conversion functions is ingeniously constructed by the integration of a propellable curtain woven by the designed fiber and solar cells. This work can provide insights into the development of advanced intelligent materials toward soft robotics, sustainable energy savings and beyond.

Bio-inspired hydrogels with fibrous structure: A review on design and biomedical applications.

Numerous tissues in the human body have fibrous structures, including the extracellular matrix, muscles, and heart, which perform critical biological functions and have exceptional mechanical strength. Due to their high-water content, softness, biocompatibility and elastic nature, hydrogels resemble biological tissues. Traditional hydrogels, on the other hand, have weak mechanical properties and lack tissue-like fibrous structures, limiting their potential applications. Thus, bio-inspired hydrogels with fibrous architectures have piqued the curiosity of biomedical researchers. Here, we review fabrication strategies for fibrous hydrogels and their recent progress in the biomedical fields of wound dressings, drug delivery, tissue engineering scaffolds and bioadhesives. Challenges and future perspectives are also discussed.

Membrane Technological Pathways and Inherent Structure of Bacterial Cellulose Composites for Drug Delivery.

This report summarizes efforts undertaken in the area of drug delivery, with a look at further efforts made in the area of bacterial cellulose (BC) biomedical applications in general. There are many current methodologies (past and present) for the creation of BC membrane composites custom-engineered with drug delivery functionality, with brief consideration for very close applications within the broader category of biomedicine. The most emphasis was placed on the crucial aspects that open the door to the possibility of drug delivery or the potential for use as drug carriers. Additionally, consideration has been given to laboratory explorations as well as already established BC-drug delivery systems (DDS) that are either on the market commercially or have been patented in anticipation of future commercialization. The cellulose producing strains, current synthesis and growth pathways, critical aspects and intrinsic morphological features of BC were given maximum consideration, among other crucial aspects of BC DDS.

Nature-Inspired Hydrogel Network for Efficient Tissue-Specific Underwater Adhesive.

Underwater adhesives with efficient, selective, and repeatable adhesion are urgently needed for biomedical applications. Catechol-containing hydrogel adhesives have aroused much interest, but the design of specific underwater adhesives to biotic surfaces is still a challenge. Here we report a facile way that recapitulates the adhesion mechanism of mussel and sea gooseberry for the development of robust and specific hydrogel adhesives. With an exquisite design of chemical bonding, catechol chemistry, and electrostatic interaction, the hydrogel consisting of poly(acrylic acid) grafted with N-hydroxysuccinimide ester (PAA-NHS ester), tea polyphenol (TP), chitosan (CS), and Al3+ exhibited fast, specific, and repeatable underwater adhesion to various biological tissues, such as porcine skin, intestine, liver, and shrimp. Furthermore, nanofibers-hydrogel composite (NF-HG) was prepared via the wicking effect of curcumin-loaded electrospun nanofibers. The NF-HG exhibited pH-responsive color changing properties, sustained drug release, and good cell viability, which made it suitable as a novel wound healing material. This strategy may provide great inspiration for designing multifunctional specific underwater adhesives.

Mussel-inspired double cross-linked hydrogels with desirable mechanical properties, strong tissue-adhesiveness, self-healing properties and antibacterial properties.

Developing multifunctional hydrogels with good mechanical properties, tissue-adhesiveness, self-healing properties and antioxidant, blood clotting and antibacterial properties is highly desirable for biomedical applications. In this study, a series of multifunctional chitosan-based double cross-linked hydrogels were prepared using a facile method based on quaternized chitosan (QCS) and polyacrylamide (PAM) using polydopamine (PDA) as a novel connecting bridge. Investigation on the content of dopamine (DA) and QCS revealed that the catechol-mediated interactions played an important role in the hydrogel properties. Results showed that the hydrogel exhibited the best mechanical properties when QCS = 12 wt% and DA = 0.4 wt%. Tensile and compressive strength was 13.3 kPa and 67.8 kPa, respectively, and the hydrogel presented strong and repeatable tissue-adhesiveness (27.2 kPa) to porcine skin, as well as good stretchability (1154%). At room temperature, the hydrogel exhibited high self-healing efficiency (90% after 2 h of healing). Antibacterial test results showed that the hydrogel killed 99.99% S. aureus and E. coli. Moreover, the vaccarin-loaded hydrogel exhibited a pH-responsive drug release profile with superior cytocompatibility compared to the pure hydrogel. In summary, this strategy combined double cross-linking and catechol-mediated chemistry to shed new light on the fabrication of novel multifunctional hydrogels with desirable mechanical properties, strong tissue adhesiveness and self-healing abilities.

Bioactive Icariin/ß-CD-IC/Bacterial Cellulose with Enhanced Biomedical Potential.

A "super" bioactive antibacterial hydrogel, Icariin-ß-CD-inclusion complex/Bacterial cellulose and an equally capable counterpart Icariin-Bacterial cellulose (ICBC) were successfully produced with excellent antioxidant properties. The highly porous hydrogels demonstrated very high fluid/liquid absorption capability and were functionally active as Fourier Transform Infrared Spectrometer (FTIR) test confirmed the existence of abundant hydroxyls (-OH stretching), carboxylic acids (-CH2/C-O stretching), Alkyne/nitrile (C≡C/C≡N stretching with triple bonds) and phenol (C-H/N-O symmetric stretching) functional groups. Scanning electron microscope (SEM) and X-ray diffraction (XRD) tests confirmed a successful ß-CD-inclusion complexation with Icariin with a great potential for sustained and controlled drug release. In vitro drug release test results indicated a systemic and controlled release of the drug (Icariin) from the internal cavities of the ß-CD inclusion complex incorporated inside the BC matrix with high Icariin (drug) release rates. Impressive inactivation rates against Gram-negative bacteria Escherichia coli ATCC 8099 and gram-positive bacteria Staphylococcus aureus ATCC 6538; >99.19% and >98.89% respectively were recorded, as the materials proved to be non-toxic on L929 cells in the in vitro cytotoxicity test results. The materials with promising versatile multipurpose administration of Icariin for wound dressing (as wound dressers), can also be executed as implants for tissue regeneration, as well as face-mask for cosmetic purposes.

Carbon quantum dots embedded electrospun nanofibers for efficient antibacterial photodynamic inactivation.

Faced with the emergence and proliferation of antibiotic resistant pathogens, novel nonspecific materials and approaches are required. Herein, we employed electrospinning technology to fabricate nanofibers with antibacterial photodynamic inactivation. This material combines polyacrylonitrile, as a photostable polymer, and biocompatible carbon quantum dots. The resulted nanofibers were successfully characterized by physical and spectroscopic methods. The microbicidal reactive oxygen species (i.e., singlet oxygen) upon illumination was confirmed, and cytotoxicity assay demonstrated that the nanofibers had low cytotoxicity and good biocompatibility. Antibacterial photodynamic inactivation studies demonstrated broad antibacterial efficacy of Gram-negative Escherichia coli ATCC-8099 (99.9999+%, 6 log units inactivation), Gram-negative Pseudomonas aeruginosa CMCC (B) 10104 (99.9999+%, 6 log units inactivation), and Gram-positive Bacillus subtilis CMCC (B) 63501 (99.9999+%, 6 log units inactivation) upon illumination with visible light (Xe lamp, 500 W, 12 cm sample distance, λ ≥ 420 nm, 1.5 h). However modest inactivation results were observed against Gram-positive Staphylococcus aureus ATCC-6538 (98.3%, 1.8 log units inactivation). Owing to the prepared nanofibers exhibiting efficient antibacterial activity against Gram-negative and Gram-positive bacteria, such materials could be potentially used in anti-infective therapy.

Insight into light-driven antibacterial cotton fabrics decorated by in situ growth strategy.

Development of ease-fabricated and effectively self-disinfecting textile materials for antimicrobial and infection prevention has been urgently desired by both consumers and industry. However, some nonresponsive antibacterial agents finished fabrics may be harmful to human. To address this issue, we developed a facile finishing method to endow woven cotton fabrics (WCF) with light-driven antibacterial property. Here in, porphyrinic metal-organic frameworks (PCN-224) were in situ synthesized on WCF (termed PCN-224/WCF) and PCN-224/WCF was proven to be used for antibacterial photodynamic inactivation (aPDI). aPDI studies indicated no difference in bacterial inactivation, the inactivation was 99.9999% of Gram-negative Escherichia coli 8099 and Pseudomonas aeruginosa CMCC (B) 10104 as well as Gram-positive Staphylococcus aureus ATCC-6538 and Bacillus subtilis CMCC (B) 63501 under visible light illumination (500 W, 15 cm vertical distance, λ ≥ 420 nm, 45 min). Cytotoxicity tests revealed PCN-224/WCF had low biological toxicity and good biocompatibility. Mechanism study revealed that singlet oxygen (1O2) was produced by PCN-224/WCF and caused severe damage to bacteria which was observed from the SEM images. This study provided a facile guideline to functionalize cotton fabrics with responsive bactericidal property which showed great potential for new generation of textiles with practical applications.

Hierarchical porous nanofibers containing thymol/beta-cyclodextrin: Physico-chemical characterization and potential biomedical applications.

As an effective natural antibacterial component, the low water solubility of thymol (THY) has stemmed its potential in biomedical application. Here, ß-cyclodextrin (ß-CD) and THY were self-assembled to form water-soluble inclusion complex (IC). The successful formation of IC was confirmed via 1H NMR. As an antibacterial agent, the resultant IC was then incorporated into cellulose acetate (CA) fibrous matrix with hierarchical structure (nanopores on porous fibrous webs) via electrospinning (CA/THY/ß-CD), and the pure THY was also encapsulated into CA for comparison (CA/THY). In vitro dissolution tests demonstrated that CA/THY/ß-CD fibrous membrane exhibited sustained drug release, which abided by non-Fickian diffusion. Besides, the CA/THY/ß-CD fibrous membrane exhibited more effective and long-lasting antibacterial activity against S. aureus. Furthermore, the combination of hierarchical porous structure with sustained drug release endowed the CA/THY/ß-CD fibrous membrane with good cytocompatibility. Taken together, the CA/THY/ß-CD fibrous membrane could be an attractive candidate for wound dressing material.

Synthesized OH-radical rich bacteria cellulosic pockets with photodynamic bacteria inactivation properties against S. ureus and E. coli.

Inulin as an external carbon source was used as the fructose substitute to Gluconacetobacter xylinus (ATCC 10245) bacterial strain in a successful synthesis of cellulosic pockets to be used in drug delivery and storage. It was observed that inulobiose trans conformation was in agreement with ϕ = Ψ = ω = 180° and angular rotation of Ï´ (C1-C2-0-CI''), Ï´ (C2-0-C 1'-C2') and Ï´ (0-C1'-C2'-0') respectively. A bacterial susceptibility test revealed a successful inactivation of Staphylococcus aureus and Escherichia coli in the presence of photons. Fourier Transform Infrared Spectroscopy analysis confirmed an OH absorption was verified at 3423 cm-1. Pocket drug uptake test revealed a highly absorbent structure with the thermal stability directly proportional to the increase in drug uptake, while the increase in the degree of polymerization resulted in the increase in antioxidant activity and rate of bacterial inactivation. HYPOTHESIS: Inulin as an inert polysaccharide is neutral to cellular activity, therefore, could not be an agent for bacteria inactivation.

Synthesis of highly stable bacterial cellulosic pocket for drug storage.

Inulin was introduced to the fructose permeates of Gluconacetobacter xylinus (ATCC 10,245) bacterial strain to successfully synthesize empty cellulosic pockets for possible drug storage. FTIR Spectroscopy analysis confirmed a slight variation in the hydrogen bonds at 2893 cm-1 due to CH and CH2 stretching whiles Conformational analysis revealed that inulobiose extending all-trans conformation corresponded to φ = Ψ = ω = 180°. Fructofuranose moiety, the anomeric carbon was defined as C2. The definition of torsional angles φ = Ï´(C1-C2-0-CI'), Ψ = Ï´ (C2-0-C 1'-C2'), and ω = Ï´(0-C1'-C2'-0') followed the proposed convention. Glycosidic angle C1'0 l'C2' was taken to be 114.0° and both O6 hydroxyl groups in inulobiose were fixed in a trans position, compelling the hydroxyl group to sterically favor comparison with the gauche orientation of sucrose structure. XRD analysis results indicated a typical cellulose type I. DSC and TGA analysis revealed a highly stable pocket until about 260°C.

Sequestration of Pb(II) Ions from Aqueous Systems with Novel Green Bacterial Cellulose Graphene Oxide Composite.

In this study, a novel green adsorbent material prepared by the esterification of bacterial cellulose (BC) and graphene oxide (GO), richly containing hydroxyl, alkyl, and carboxylate groups was characterised by FTIR (Fourier Transform infrared spectroscopy), XRD (X-ray diffraction), SEM (Scanning electron microscopy) and TGA (Thermo-graphimetric analysis). The specific surface area (SSA) and pore size distribution (PSD) analysis of materials were also analysed. Batch experiments⁻adsorption studies confirmed the material to have a very high Pb2+ removal efficiency of over 90% at pH 6⁻8. Kinetic studies showed that the uptake of metal ions was rapid with equilibrium attained after 30 min and fitted well with the pseudo-second-order rate model (PSO). Isotherm results with a maximum adsorption capacity (Qmax) of 303.03 mg/g were well described by Langmuir's model compared to Freundlich. Desorption and re-adsorption experiments realised that both adsorbent and adsorbates could be over 90⁻95% efficiently recovered and reused using 0.1 M HNO3 and 0.1 M HCl.