Chitosan/polyethylene glycol fumarate blend film: Physical and antibacterial properties

Lightweight, ultra-compressed, and environmentally friendly wood/TPU aerogel sensor based on optimized performance of dynamic 3D pore structure

Although bio-based sensing materials have a wide range of applications in the field of pressure detection, they still need to improve their sensitivity, detection limit and hysteresis. This paper studied the relationship between the 3D pore structure and sensing performance under dynamics. Using Balsa wood as the substrate, CWA/TPU aerogel and its sensor were prepared with lightweight, compressibility, highly sensitivity, wide-detection, and low-hysteresis. Meanwhile, the brittleness problem of the carbonized aerogel was solved by uniformly attaching TPU to the aerogel interface. In this paper, the 3D structure of CWA/TPU aerogel during compression was reconstructed by Micro-XCT technology, and the results show that the sensitivity of the bio-based carbonized material is directly proportional to the porosity and inversely proportional to the aspect ratio. This CWA/TPU aerogel pressure sensor has a high sensitivity of 76.18 kPa-1 in a wide detection limit of 0.6 Pa-100 kPa, 90 % supercompression strain, ±7.4 % low hysteresis and outstanding stability over 10,000 cycles. And the sensor can detect different ranges of pressure strains and has great potential for future applications in physiological signal monitoring, action recognition, and sports training.

Films based on TEMPO-oxidized chitosan nanoparticles: Obtaining and potential application as wound dressings

A series of novel films based on TEMPO-oxidized chitosan nanoparticles were prepared by casting method. Fourier transform infrared spectroscopy (FTIR) was employed to ascertain the chemical structure of TEMPO-oxidized chitosan. The surface morphology of the TEMPO-oxidized chitosan nanoparticles was analyzed by atomic force microscopy (AFM). The physicochemical (area density, thickness, iodine sorption, roughness), functional (moisture sorption, liquid absorption capacity, weight loss upon contact with the liquid, and water vapor transmission rate), antibacterial, and antioxidant properties of films based on TEMPO-oxidized chitosan nanoparticles were also investigated. The physicochemical properties of the films varied widely: area density ranged from 77.83 ± 0.06 to184.46 ± 0.05 mg/cm2, thickness varied between 80.5 ± 1.6 and 200.5 ± 1.6 μm, iodine sorption spanned from 333.7 ± 2.1 to166.4 ± 2.2 mg I2/g, and roughness ranged from 4.1 ± 0.2 to 5.6 ± 0.3 nm. Similarly, the functional properties also varied significantly: moisture sorption ranged from 4.76 ± 0.03 to 9.62 ± 0.11 %, liquid absorption capacity was between 129.04 ± 0.24 and 159.33 ± 0.73 % after 24 h, weight loss upon contact with the liquid varied between 31.06 ± 0.35 and 45.88 ± 0.58 % after 24 h and water vapor transmission rate ranged from 1220.10 ± 2.91to1407.77 ± 5.22 g/m2 day. Despite the wide variations in physicochemical and functional properties, all films showed maximum bacterial reduction of Staphylococcus aureus and Escherichia coli, although they exhibited low antioxidant activity. The results suggest that the films could be effectively utilized as antibacterial wound dressings.

Insect cuticle-inspired design of sustainably sourced composite bioplastics with enhanced strength, toughness and stretch-strengthening behavior

Insect cuticles that are mainly made of chitin, chitosan and proteins provide insects with rigid, stretchable and robust skins to defend harsh external environment. The insect cuticle therefore provides inspiration for engineering biomaterials with outstanding mechanical properties but also sustainability and biocompatibility. We herein propose a design of high-performance and sustainable bioplastics via introducing CPAP3-A1, a major structural protein in insect cuticles, to specifically bind to chitosan. Simply mixing 10w/w% bioengineered CPAP3-A1 protein with chitosan enables the formation of plastics-like, sustainably sourced chitosan/CPAP3-A1 composites with significantly enhanced strength (∼90 MPa) and toughness (∼20 MJ m -3), outperforming previous chitosan-based composites and most synthetic petroleum-based plastics. Remarkably, these bioplastics exhibit a stretch-strengthening behavior similar to the training living muscles. Mechanistic investigation reveals that the introduction of CPAP3-A1 induce chitosan chains to assemble into a more coarsened fibrous network with increased crystallinity and reinforcement effect, but also enable energy dissipation via reversible chitosan-protein interactions. Further uniaxial stretch facilitates network re-orientation and increases chitosan crystallinity and mechanical anisotropy, thereby resulting in stretch-strengthening behavior. In general, this study provides an insect-cuticle inspired design of high-performance bioplastics that may serve as sustainable and bio-friendly materials for a wide range of engineering and biomedical application potentials.

Effect of polyethylene glycol on polysaccharides: From molecular modification, composite matrixes, synergetic properties to embeddable application in food fields

Polyethylene glycol (PEG) is a flexible, water-soluble, non-immunogenic, as well as biocompatible polymer, and it could synergize with polysaccharides for food applications. The molecular modification strategies, including covalent bond interactions (amino groups, carboxyl groups, aldehyde groups, tosylate groups, etc.), and non-covalent bond interactions (hydrogen bonding, electrostatic interactions, etc.) on PEG molecular chains are discussed. Its versatile structure, group modifiability, and amphiphilic block buildability could improve the functions of polysaccharides (e.g., chitosan, cellulose, starch, alginate, etc.) and adjust the properties of combined PEG/polysaccharides with outstanding chain tunability and matrix processability owing to plasticizing effects, compatibilizing effects, steric stabilizing effects and excluded volume effects by PEG, for achieving the diverse performance targets. The synergetic properties of PEG/polysaccharides with remarkable architecture were summarized, including mechanical properties, antibacterial activity, antioxidant performance, self-healing properties, carrier and delivery characteristics. The PEG/polysaccharides with excellent combined properties and embeddable merits illustrate potential applications including food packaging, food intelligent indication/detection, food 3D printing and nutraceutical food absorption. Additionally, prospects (like food innovation and preferable nutrient utilization) and key challenges (like structure-effectiveness-applicability relationship) for PEG/polysaccharides are proposed and addressed for food fields.

Bacterial Cellulose-Based Bandages with Integrated Antibacteria and Electrical Stimulation for Advanced Wound Management

Bandages for daily wounds are the most common medical supplies, but there are still ingrained defects in their appearance, comfort, functions, as well as environmental pollution. Here, novel bandages based on bacterial cellulose (BC) membrane for wound monitoring and advanced wound management are developed. The BC membrane is combined with silver nanowires (AgNWs) by using vacuum filtration method to achieve transparent, ultrathin (≈7 µm), breathable (389.98-547.79 g m-2  d-1 ), and sandwich-structured BC/AgNWs bandages with superior mechanical properties (108.45-202.35 MPa), antibacterial activities against Escherichia coli and Staphylococcus aureus, biocompatibility, and conductivity (9.8 × 103 -2.0 × 105  S m-1 ). Significantly, the BC/AgNWs bandage is used in the electrical stimulation (direct current, 600  microamperes for 1 h every other day) treatment of full-thickness skin defect in rats, which obviously promotes wound healing by increasing the secretion of vascular endothelial growth factor (VEGF). The BC bandage is used for monitoring wounds and achieve a high accuracy of 94.7% in classifying wound healing stages of hemostasis, inflammation, proliferation, and remodeling, by using a convolutional neural network. The outcomes of this study not only provide two BC-based bandages as multifunctional wound management, but also demonstrate a new strategy for the development of the next generation of smart bandage.

PEGylated curcumin-loaded poly(vinyl alcohol)/Zwitterionic poly(sulfobetaine vinylimidazole)-grafted chitosan nanofiber as a second-degree burn wound dressing

Burn injuries damage skin function and increased the risk of infection. Using natural-inspired antibiotic-free nanofibrous in wound healing has attracted increasing attention. Here, mPEG-Curcumin (mPEG-CUR) was synthesized through a novel, cheap, and high-efficiency method, and incorporated onto poly(vinyl alcohol) (PVA)/zwitterionic poly(sulfobetaine vinylimidazole)-grafted chitosan (CS-g-PNVIS) nanofiber. Due to the lack of electrospinning capability of CS-g-PNVIS and its brittleness, to obtain nanofibers with uniform and bead-free morphology, PVA was used as an electrospinning aid polymer, so that the prepared nanofibers have suitable mechanical properties with an average diameter between 115 ± 18-157 ± 39 nm. The heat-treated nanofibers have adequate swelling and dimensional stability. Time-killing assay proved the antibacterial activity of the mPEG-CUR-loaded nanofibers towards Gram-positive and Gram-negative bacterium. The MTT investigation illustrated the non-cytotoxicity and biocompatibility of the nanofibers. In vivo studies exhibited significant improvement in the mean wound area closure by applying mPEG-CUR nanofibers. The mPEG-CUR-loaded nanofibers showed the highest antioxidant (86 %) power after 40 min. Moreover, nanofibers possess a desirable WVT rate (3.4 ± 0.24-5.5 ± 0.3 kg/m2.d) and good breathability and had the potential to supply a suitable moist environment in the wounded area. This approach can be the beginning of a new path in designing a new generation of nanofiber mats for wound healing applications.

In Vitro Evaluation of Biphasic Calcium Phosphate Scaffolds Derived from Cuttlefish Bone Coated with Poly(ester urea) for Bone Tissue Regeneration

This study investigates the osteogenic differentiation of umbilical-cord-derived human mesenchymal stromal cells (hUC-MSCs) on biphasic calcium phosphate (BCP) scaffolds derived from cuttlefish bone doped with metal ions and coated with polymers. First, the in vitro cytocompatibility of the undoped and ion-doped (Sr²⁺, Mg²⁺ and/or Zn²⁺) BCP scaffolds was evaluated for 72 h using Live/Dead staining and viability assays. From these tests, the most promising composition was found to be the BCP scaffold doped with strontium (Sr²⁺), magnesium (Mg²⁺) and zinc (Zn²⁺) (BCP-6Sr2Mg2Zn). Then, samples from the BCP-6Sr2Mg2Zn were coated with poly(ԑ-caprolactone) (PCL) or poly(ester urea) (PEU). The results showed that hUC-MSCs can differentiate into osteoblasts, and hUC-MSCs seeded on the PEU-coated scaffolds proliferated well, adhered to the scaffold surfaces, and enhanced their differentiation capabilities without negative effects on cell proliferation under in vitro conditions. Overall, these results suggest that PEU-coated scaffolds are an alternative to PCL for use in bone regeneration, providing a suitable environment to maximally induce osteogenesis.

Bio-Multifunctional Sponges Containing Alginate/Chitosan/Sargassum Polysaccharides Promote the Healing of Full-Thickness Wounds

Creation of bio-multifunctional wound dressings with potent hemostatic, antibacterial, anti-inflammatory, and angiogenesis features for bolstering the healing of full-thickness wounds is sought after for clinical applications. We created bio-multifunctional composite sponges by coupling alginate and chitosan with Sargassum pallidum polysaccharides through electrostatic interactions, calcium ion (Ca2+) crosslinking, and lyophilization. Alginate/chitosan (AC) sponges with different concentrations of Sargassum pallidum polysaccharides were obtained and termed AC, ACS-1%, ACS-2.5%, and ACS-5%. ACS-1% and ACS-2.5% sponges exhibited uniform porosity, high water vapor transmission rate, high water absorption, as well as good hemostatic and antibacterial abilities. ACS-2.5% sponges facilitated wound closure and promoted angiogenesis and re-epithelialization in the dermis. These data suggest that ACS sponges containing a certain amount of Sargassum pallidum polysaccharides could be employed for treatment of full-thickness skin wounds.

Essential Oils as Antimicrobial Active Substances in Wound Dressings

Wound dressings for skin lesions, such as bedsores or pressure ulcers, are widely used for many patients, both during hospitalization and in subsequent treatment at home. To improve the treatment and shorten the healing time and, therefore, the cost, numerous types of wound dressings have been developed by manufacturers. Considering certain inconveniences related to the intolerance of some patients to antibiotics and the antimicrobial, antioxidant, and curative properties of certain essential oils, we conducted research by incorporating these oils, based on polyvinyl alcohol/ polyvinyl pyrrolidone (PVA/PVP) biopolymers, into dressings. The objective of this study was to study the potential of a polymeric matrix for wound healing, with polyvinyl alcohol as the main material and polyvinyl pyrrolidone and hydroxypropyl methylcellulose (HPMC) as secondary materials, together with additives (plasticizers poly(ethylene glycol) (PEG) and glycerol), stabilizers (Zn stearate), antioxidants (vitamin A and vitamin E), and four types of essential oils (fennel, peppermint, pine, and thyme essential oils). For all the studied samples, the combining compatibility, antimicrobial, and cytotoxicity properties were investigated. The obtained results demonstrated a uniform morphology for almost all the samples and adequate barrier properties for contact with suppurating wounds. The results show that the obtained samples containing essential oils have a good inhibitory effect on, or antimicrobial properties against, Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and Candida albicans ATCC 10231. The MTT assay showed that the tested samples were not toxic and did not lead to cell death. The results showed that the essential oils used provide an effective solution as active substances in wound dressings.

All electrospun fabrics based piezoelectric tactile sensor

Tactile sensors have been widely used in the areas of health monitoring and intelligent human-machine interface. Flexible tactile sensors based on nanofiber mats made by electrospinning can meet the requirements of comfortability and breathability for wearing the body very well. Here, we developed a flexible and self-powered tactile sensor that was sandwich assembled by electrospun organic electrodes and a piezoelectric layer. The metal-free organic electrodes of thermal plastic polyurethane (PU) nanofibers decorated with multi-walled carbon nanotubes were fabricated by electrospinning followed by ultrasonication treatment. The electrospun polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) mat was utilized as the piezoelectric layer, and it was found that the piezoelectric performance of PVDF-TrFE nanofiber mat added with barium titanate (BaTiO₃) nanoparticles was enhanced about 187% than that of the pure PVDF-TrFE nanofiber mat. For practical application, the as-prepared piezoelectric tactile sensor exhibited an approximative linear relationship between the external force and the electrical output. Then the array of fabricated sensors was attached to the fingertips of a glove to grab a cup of water for tactile sensing, and the mass of water can be directly estimated according to the outputs of the sensor array. Attributed to the integrated merits of good flexibility, enhanced piezoelectric performance, light weight, and efficient gas permeability, the developed tactile sensor could be widely used as wearable devices for robot execution end or prosthesis for tactile feedback.

Polymeric biomaterials for wound healing applications: a comprehensive review

Chronic wounds have been a global health threat over the past few decades, requiring urgent medical and research attention. The factors delaying the wound-healing process include obesity, stress, microbial infection, aging, edema, inadequate nutrition, poor oxygenation, diabetes, and implant complications. Biomaterials are being developed and fabricated to accelerate the healing of chronic wounds, including hydrogels, nanofibrous, composite, foam, spongy, bilayered, and trilayered scaffolds. Some recent advances in biomaterials development for healing both chronic and acute wounds are extensively compiled here. In addition, various properties of biomaterials for wound-healing applications and how they affect their performance are reviewed. Based on the recent literature, trilayered constructs appear to be a convincing candidate for the healing of chronic wounds and complete skin regeneration because they mimic the full thickness of skin: epidermis, dermis, and the hypodermis. This type of scaffold provides a dense superficial layer, a bioactive middle layer, and a porous lower layer to aid the wound-healing process. The hydrophilicity of scaffolds aids cell attachment, cell proliferation, and protein adhesion. Other scaffold characteristics such as porosity, biodegradability, mechanical properties, and gas permeability help with cell accommodation, proliferation, migration, differentiation, and the release of bioactive factors.

Breathable and Wearable Strain Sensors Based on Synergistic Conductive Carbon Nanotubes/Cotton Fabrics for Multi-directional Motion Detection

Flexible strain-sensitive sensors have been receiving intensive attention in many aspects ranging from human motion capture to health-related signal monitoring. However, the fabric strain sensor with multi-directional sensing capability, besides having a wide strain range and high response sensitivity, is still very challenging and deserves further exploration. Here, we have prepared a wearable cotton fabric strain sensor uniformly decorated with single-walled carbon nanotubes through a facile solution process. The unique hierarchical architecture of the cotton fabric woven from twisted yarns combined with the conductive carbon nanotube network endows the fabric strain sensors with attractive performance, including low detection limit, large workable strain range, fascinating stability and durability, excellent direction-dependent strain response, and good air permeability. The strain sensor without polymer encapsulation can not only monitor subtle and large multi-directional motions but also fit well to the human body with satisfactory comfort, demonstrating its potential application in wearable electronics and intelligent clothing.

A Review on Antibacterial Biomaterials in Biomedical Applications: From Materials Perspective to Bioinks Design

In tissue engineering, three-dimensional (3D) printing is an emerging approach to producing functioning tissue constructs to repair wounds and repair or replace sick tissue/organs. It allows for precise control of materials and other components in the tissue constructs in an automated way, potentially permitting great throughput production. An ink made using one or multiple biomaterials can be 3D printed into tissue constructs by the printing process; though promising in tissue engineering, the printed constructs have also been reported to have the ability to lead to the emergence of unforeseen illnesses and failure due to biomaterial-related infections. Numerous approaches and/or strategies have been developed to combat biomaterial-related infections, and among them, natural biomaterials, surface treatment of biomaterials, and incorporating inorganic agents have been widely employed for the construct fabrication by 3D printing. Despite various attempts to synthesize and/or optimize the inks for 3D printing, the incidence of infection in the implanted tissue constructs remains one of the most significant issues. For the first time, here we present an overview of inks with antibacterial properties for 3D printing, focusing on the principles and strategies to accomplish biomaterials with anti-infective properties, and the synthesis of metallic ion-containing ink, chitosan-containing inks, and other antibacterial inks. Related discussions regarding the mechanics of biofilm formation and antibacterial performance are also presented, along with future perspectives of the importance of developing printable inks.

High antibacterial activity of chitosan films with covalent organic frameworks immobilized silver nanoparticles

In this study, chitosan (CS) film containing covalent organic frameworks (COFs) immobilized silver nanoparticles (AgNPs) were developed for food packaging with improved antibacterial activities and film properties. COFs-AgNPs were fabricated via in-situ synthesis of immobilizing AgNPs on COFs. Transmission electron microscope, Zeta potential, X-ray diffraction, element mapping and Fourier transform infrared spectroscopy confirmed the successful fabrication of COFs-AgNPs, and COFs-AgNPs showed superior antibacterial activity against S. aureus and E. coli. Furthermore, the as-prepared COFs-AgNPs composite was further used to fabricate CS composite films (CS/COFs-AgNPs) by a solution casting method. The findings showed that the tensile strength of the nanocomposite films enhanced dramatically with the increase of the COFs-AgNPs content, while the UV-visible light barrier property, water swelling and solubility properties, and water vapor permeability (WVP) decreased significantly. Not only that, the CS/COFs-AgNPs nanocomposite films also showed outstanding antibacterial activity and effectively prolonged the storage time of white crucian carp (Carassius auratus). As a result, CS/COFs-AgNPs nanocomposite films show great potential in active food packaging.

Breathable Strain/Temperature Sensor Based on Fibrous Networks of Ionogels Capable of Monitoring Human Motion, Respiration, and Proximity

Wearable strain and temperature sensors are desired for human-machine interfaces, health monitoring, and human motion monitoring. Herein, the fibrous mat with aligned nanofibers of ionic liquid (IL)/thermoplastic polyurethane (TPU) ionogels is fabricated via an electrospinning technique. The resultant fibrous mat is cut into a rectangle specimen and electrodes are loaded along the direction perpendicular to the nanofiber orientation to design a high-performance multimodal sensor based on an ionic conducting mechanism. As a strain sensor, the obtained sensor exhibits a wide strain working range (0-200%), a fast response and recovery (119 ms), a low detection limit (0.1%), and good reproducibility because of the reversible and deformable ionic conductive pathways of the sensor. Moreover, the sensor also exhibits excellent temperature-sensing behaviors, including a monotonic thermal response, high sensitivity (2.75% °C^-1), high accuracy (0.1 °C), a fast response time (2.46 s), and remarkable repeatability, attributable to the negative temperature coefficient behavior of the IL/TPU fibrous mat. More interestingly, the IL/TPU fibrous sensor possesses good breathability, which is desired for wearable electronics. Because of these excellent sensing capabilities in strain and temperature, the sensor can not only monitor tiny and large human motions but also detect respiration and proximity, exhibiting enormous potential in wearable electronics.

Sustainable Chitosan-Dialdehyde Cellulose Nanocrystal Film

In this study, we incorporated 2,3-dialdehyde nanocrystalline cellulose (DANC) into chitosan as a reinforcing agent and manufactured biodegradable films with enhanced gas barrier properties. DANC generated via periodate oxidation of cellulose nanocrystal (CNC) was blended at various concentrations with chitosan, and bionanocomposite films were prepared via casting and characterized systematically. The results showed that DANC developed Schiff based bond with chitosan that improved its properties significantly. The addition of DANC dramatically improved the gas barrier performance of the composite film, with water vapor permeability (WVP) value decreasing from 62.94 g·mm·m-2·atm-1·day-1 to 27.97 g·mm·m-2·atm-1·day-1 and oxygen permeability (OP) value decreasing from 0.14 cm3·mm·m-2·day-1·atm-1 to 0.026 cm3·mm·m-2·day-1·atm-1. Meanwhile, the maximum decomposition temperature (Tdmax) of the film increased from 286 °C to 354 °C, and the tensile strength of the film was increased from 23.60 MPa to 41.12 MPa when incorporating 25 wt.% of DANC. In addition, the chitosan/DANC (75/25, wt/wt) films exhibited superior thermal stability, gas barrier, and mechanical strength compared to the chitosan/CNC (75/25, wt/wt) film. These results confirm that the DANC and chitosan induced films with improved gas barrier, mechanical, and thermal properties for possible use in film packaging.

Silk sericin/fibroin electrospinning dressings: a method for preparing a dressing material with high moisture vapor transmission rate

The current study focuses on the preparation of sericin and silk fibroin blend electrostatic spinning fiber film dressing. The surface morphology of the fiber films was observed by scanning electron microscope, and the hydrophilicity and swelling property of the fiber membrane dressing were analyzed. The biocompatibility of the four dressings was verified by the CCK-8 method and confocal laser microscopy. This experiment showed that the dressing group with the ratio of sericin to silk fibroin of 3:7 had better performance, offering fine and uniform fiber structure, good surface hydrophilicity, high water vapor transmission rate. The swelling rate of it was 822.77 ± 62.78%, and the tensile properties reached the requirements of dressing materials and had an excellent ability to promote cell adhesion and proliferation. This paper provides a possible method for producing of dressing materials with good hydrophilicity and high moisture vapor transmission rate.

Chitosan/Hyaluronic acid/Alginate and an assorted polymers loaded with honey, plant, and marine compounds for progressive wound healing-Know-how

Biomaterials are being extensively used in regenerative medicine including tissue engineering applications, as these enhance tissue development, repair, and help in the process of angiogenesis. Wound healing is a crucial biological process of regeneration of ruptured tissue after getting injury to the skin and other soft tissue in humans and animals. Besides, the accumulation of microbial biofilms around the wound surface can increase the risk and physically obstruct the wound healing activity, and may even lead to amputation. Hence, in both acute and chronic wounds, prominent biomaterials are required for wound healing along with antimicrobial agents. This review comprehensively addresses the antimicrobial and wound healing effects of chitosan, chitin, cellulose acetate, hyaluronic acid, pullulan, bacterial cellulose, fibrin, alginate, etc. based wound dressing biomaterials fabricated with natural resources such as honey, plant bioactive compounds, and marine-based polymers. Due to their excellent biocompatibility and biodegradability, bioactive compounds derived from honey, plants, and marine resources are commonly used in biomedical and tissue engineering applications. Different types of polymer-based biomaterials including hydrogel, film, scaffold, nanofiber, and sponge dressings fabricated with bioactive agents including honey, curcumin, tannin, quercetin, andrographolide, gelatin, carrageenan, etc., can exhibit significant wound healing process in, diabetic wounds, diabetic ulcers, and burns, and help in cartilage repair along with good biocompatibility and antimicrobial effects. Among the reviewed biomaterials, carbohydrate polymers such as chitosan-based biomaterials are prominent and widely used for wound healing applications followed by hyaluronic acid and alginate-based biomaterials loaded with honey, plant, and marine compounds. This review first provides an overview of the vast natural resources used to formulate different biomaterials for the treatment of antimicrobial, acute, and chronic wound healing processes.

High-Performance Foam-Shaped Strain Sensor Based on Carbon Nanotubes and Ti3C2Tx MXene for the Monitoring of Human Activities

The flexible strain sensor is of significant importance in wearable electronics, since it can help monitor the physical signals from the human body. Among various strain sensors, the foam-shaped ones have received widespread attention owing to their light weight and gas permeability. However, the working range of these sensors is still not large enough, and the sensitivity needs to be further improved. In this work, we develop a high-performance foam-shaped strain sensor composed of Ti₃C₂T_x MXene, multiwalled carbon nanotubes (MWCNTs), and thermoplastic polyurethane (TPU). MXene sheets are adsorbed on the surface of a composite foam of MWCNTs and TPU (referred to as TPU/MWCNTs foam), which is prefabricated by using a salt-templating method. The obtained TPU/MWCNTs@MXene foam works effectively as a lightweight, easily processable, and sensitive strain sensor. The TPU/MWCNTs@MXene device can deliver a wide working strain range of ∼100% and an outstanding sensitivity as high as 363 simultaneously, superior to the state-of-the-art foam-shaped strain sensors. Moreover, the composite foam shows an excellent gas permeability and suitable elastic modulus close to those of skin, indicating its being highly comfortable as a wearable sensor. Owing to these advantages, the sensor works effectively in detecting both subtle and large human movements, such as joint motion, finger motion, and vocal cord vibration. In addition, the sensor can be used for gesture recognition, demonstrating its perspective in human-machine interaction. Because of the high sensitivity, wide working range, gas permeability, and suitable modulus, our foam-shaped composite strain sensor may have great potential in the field of flexible and wearable electronics in the near future.

Superclear, Porous Cellulose Membranes with Chitosan-Coated Nanofibers for Visualized Cutaneous Wound Healing Dressing

Easy and rapid continuous large-scale industrial production of transparent visualized cutaneous wound healing dressing from natural polymers is very worth studying in medical natural polymer materials and multifunction gauze dressing design fields. In this work, superclear, porous cellulose membranes (CMs) with chitosan-coated nanofibers were fabricated using a simple, one-step electrostatic spinning technology and evaluated as potential wound dressings. First, the pure CMs were dissolved by a simple physical method, and then, the membranes were regenerated in an acidic coagulation bath by the casting method. The chitosan solution was polarized into nanofibers and formed a continuous fiber mat on CMs because of the charge repulsion between molecules. The prepared chitosan-coated CMs (CM-CS) were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, tensile tests, and so forth. The results indicated that CM-CS showed high wettability, hydrophilicity, and gas permeability, in addition to excellent light transmittance and mechanical compliance. Cell cytotoxicity and morphology assay and antibacterial activity against Escherichia coli and Staphylococcus aureus were also studied. They exhibited good biocompatibility and antibacterial activity of CM-CS. Moreover, evaluation of an in vivo wound healing model in mice revealed that CM-CS had a good effect in promoting wound healing. This work provided an easy and rapid continuous large-scale industrial design strategy for natural bioresource-based wound dressing materials, which could act as potential wound dressings for clinical use.

Chitosan/gum tragacanth/PVA hybrid nanofibrous scaffold for tissue engineering applications

In this paper, preparation and characterization of a nanofibrous scaffold comprising both chitosan (CS) and gum tragacanth (GT) are reported for the first time. CS and GT were separately blended with poly(vinyl alcohol) (PVA) and simultaneously electrospun by a double-nozzle electrospinning apparatus, and the resulting nanofibrous mats were compared with CS/PVA and GT/PVA electrospun ones. Scanning electron microscopy images showed uniform bead-free nanofibers with some merging areas and an average fiber diameter of ∼273 nm for CS-PVA/GT-PVA. The ultimate tensile strength and strain at break of the hybrid nanofibers were ∼20 MPa and ∼9%, respectively, which were significantly higher than those of the CS/PVA and GT/PVA nanofibers. The CS-PVA/GT-PVA nanofibrous mats also showed a water droplet contact angle value (∼31°) between those of the CS/PVA and GT/PVA nanofibrous mats. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay using L929 fibroblast cells indicated more biocompatibility of the CS-PVA/GT-PVA hybrid nanofibers compared with the CS/PVA and GT/PVA ones. The obtained results showed that the CS-PVA/GT-PVA hybrid nanofibrous scaffold might be useful for tissue engineering applications.

A Smart Drug Delivery System Based on Biodegradable Chitosan/Poly(allylamine hydrochloride) Blend Films

The amalgamation of natural polysaccharides with synthetic polymers often produces fruitful results in the area of drug delivery due to their biodegradable and biocompatible nature. In this study, a series of blend films composed of chitosan (CS)/poly(allylamine hydrochloride) (PAH) in different compositions were prepared as smart drug delivery matrices. The properties of these polymeric films were then explored. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) analysis confirmed an intermolecular hydrogen bonding between CS and PAH. Atomic force microscopy (AFM) revealed improvements in surface morphology as the percentage of PAH in the blend films increased up to 60% (w/w). Water contact angle (WCA) ranged between 97° to 115°, exhibiting the hydrophobic nature of the films. Two films were selected, CTH-1 (90% CS and 10% PAH) and CTH-2 (80% CS and 20% PAH), to test for in vitro cumulative drug release (%) at 37 ± 0.5 °C as a function of time. It was revealed that for simulated gastric fluid (SGF) with pH 1.2, the cumulative drug release (CDR) for CTH-1 and CTH-2 was around 88% and 85% in 50 min, respectively. Both films converted into gel-like material after 30 min. On the other hand, in pH 7.4 phosphate buffer saline (PBS) solution, the maximum CDR for CTH-1 and CTH-2 was 93% in 90 min and 98% in 120 min, respectively. After 120 min, these films became fragments. Sustained drug release was observed in PBS, as compared to SGF, because of the poor stability of the films in the latter. These results demonstrate the excellent potential of blend films in sustained-release drug delivery systems for hydrophilic or unstable drugs.

Laser-Processed Nature-Inspired Deformable Structures for Breathable and Reusable Electrophysiological Sensors toward Controllable Home Electronic Appliances and Psychophysiological Stress Monitoring

Physiological monitoring through skin patch stretchable devices has received extensive attention because of their significant findings in many human-machine interaction applications. In this paper, we present novel nature-inspired, kiri-spider, serpentine structural designs to sustain mechanical deformations under complex stress environments. Strain-free mechanical structures involving stable high areal coverage (spiderweb), three-dimensional out-of-plane deformations (kirigami), and two-dimensional (2D) stretchable (2D spring) electrodes demonstrated high levels of mechanical loading under various strains, which were verified through theoretical and experimental studies. Alternative to conventional microfabrication procedures, sensors fabricated by a facile and rapid benchtop programmable laser machine enabled the realization of low-cost, high-throughput manufacture, followed by transferring procedures with a nearly 100% yield. For the first time, we demonstrated laser-processed thin (∼10 μm) flexible filamentary patterns embedded within the solution-processed polyimide to make it compatible with current flexible printed circuit board electronics. A patch-based sensor with thin, breathable, and sticky nature exhibited remarkable water permeability >20 g h^-1 m^-2 at a thickness of 250 μm. Moreover, the reusability of the sensor patch demonstrated the significance of our patch-based electrophysiological sensor. Furthermore, this wearable sensor was successfully implemented to control human-machine interfaces to operate home electronic appliances and monitor mental stress in a pilot study. These advances in novel mechanical architectures with good sensing performances provide new opportunities in wearable smart sensors.

Engineering Sustainable Antimicrobial Release in Silica-Cellulose Membrane with CaCO3-Aided Processing for Wound Dressing Application

The sustained release of antimicrobial therapeutics for wound dressing has become an attractive design strategy for prolonging the timespan of wound dressings and for reducing the risk of chronic wound infection. Recently, cellulose-based membrane has become a preferred option of wound dressings for the treatment of burn wounds and skin ulcers. In this work, novel cellulose membrane incorporated with mesoporous silica particles (SBA-15) was developed as an antimicrobial wound dressing with desirable sustained release functionality for targeting persistent bacterial pathogens. Attributed to a coated layer of calcium carbonate (CaCO₃), SBA-15 particles were free from corrosion in alkaline condition during the preparation of cellulose-based composite membranes. SEM, TEM and BET results showed that the morphology, specific surface area, pore size and pore volume of pristine SBA-15 were preserved after the incorporation of CaCO₃-coated SBA-15 into the cellulose matrix, while the mesoporous structure of SBA-15 was significantly disrupted without the use of CaCO₃ coating. The resultant composite membranes containing 30 wt% SBA-15 (denoted as CM-Ca2-SBA(30%)) achieved 3.6 wt% of antimicrobial drug loading. Interestingly, CM-Ca2-SBA(30%) demonstrated the sustained release property of chloramphenicol for 270 h, driven by a two-stage drug release processes of SBA-15/cellulose. The water vapor permeability (WVTR) and swelling properties of composite membranes were shown to have complied with the primary requirements of wound dressing. Antibacterial assays revealed that strong antibacterial activities (144 h) of the composite membranes against Staphylococcus aureus and Eschericia coli were achieved. All results displayed that the strategy of coating silica with CaCO₃ helps to obtain cellulose–silica composite membranes with desirable sustained release profiles and strong antibacterial activities. The antibacterial SBA-15/cellulose composite membranes show potential for the application of wound dressing.

Freeze-thaw-induced cross-linked PVA/chitosan for oxytetracycline-loaded wound dressing: the experimental design and optimization

Oxytetracycline is an antibiotic for the treatment of the infections caused by Gram-positive and Gram-negative microorganisms. Among novel formulations applied for damaged skin, hydrogels have shown to be superior as they can provide a moist environment for the wound. The purpose of this study was to prepare and evaluate the hydrogels of oxytetracycline consisted of polyvinyl alcohol (PVA) and chitosan polymers. A study design based on 4 factors and 3 levels was used for the preparation and evaluation of hydrogels formed by freeze-thaw (F-T) cycle using PVA and chitosan as a matrix-based wound dressing system. Furthermore, an experimental design was employed in order to study the effect of independent variables, namely drug amount (X₁, 500-1000 mg), the amount of PVA (X₂, 3.33-7.5%), the amount of chitosan (X₃, 0.5-1%), and F-T cycle (X₄, 3-7 cycles) on the dependent variables, including encapsulation efficiency, swelling index, adsorption of protein onto hydrogel surface, and skin permeation. The interaction of formulation variables had a significant effect on both physicochemical properties and permeation. Hydrogel microbial tests with sequential dilution method in Muller-Hinton broth medium were also carried out. The selected hydrogel (F6) containing 5% PVA, 0.75% chitosan, 1000 mg drug, and 3 F-T cycles was found to have increased encapsulation efficiency, gel strength, and higher skin permeation suitable for faster healing of wounds. Results showed the biological stability of oxytetracycline HCl in the hydrogel formulation with a lower dilution of the pure drug. Thus, oxytetracycline-loaded hydrogel could be a potential candidate to be used as a wound dressing system.

Biopharmaceutical Activities Related to Ellagic Acid, Chitosan, and Zein and Their Improvement by Association

Ellagic acid (EA) has demonstrated several biological properties, such as antioxidant, antimicrobial, and enzymatic inhibition. Zein and chitosan (CHI) are natural polymers whose biological potential has also gained attention. Therefore, this paper aimed to evaluate the antimicrobial, antioxidant, anticollagenase, and antielastase properties of EA, zein, and chitosan isolated or in combination. The microdilution method was used to assess the minimum inhibitory and bactericide concentrations. The antioxidant activity was determined using the 2,2-diphenyl-1-picryl-hydrazila free radical scavenging method. The anticollagenase and antielastase activities were evaluated by specific colorimetric tests. EA has shown inhibitory activity against Staphylococcus aureus and Pseudomonas aeruginosa together with an antioxidant IC₅₀ of 0.079 mg/mL. EA also showed significant collagenase and elastase inhibition. Zein has shown antimicrobial and antioxidant activities itself and enhanced sinergically the antioxidant activity and the antimicrobial activity against P. aeruginosa when combined with EA. CHI increased sinergically the inhibitory activity of EA against both bacterial strains, while showed itself an acceptable antimicrobial activity. ¹ H saturation transfer-difference nuclear magnetic resonance experiment confirmed the formation of a complex between EA and zein that could be related with the improvement on its biological performance over the individual compounds, while no chemical interaction was detected between CHI and EA. PRACTICAL APPLICATION: The results reinforce the potential of ellagic acid in combination with zein and/or chitosan as an antimicrobial, antienzimatic, and antioxidant agent. Those findings reinforce the use of these substances, protecting this bioactive from degradation and/or improving the functional characteristics and biopharmaceutical properties.

Coatings as the useful drug delivery system for the prevention of implant-related infections

Implant-related infections (IRIs) which led to a large amount of medical expenditure were caused by bacteria and fungi that involve the implants in the operation or in ward. Traditional treatments of IRIs were comprised of repeated radical debridement, replacement of internal fixators, and intravenous antibiotics. It needed a long time and numbers of surgeries to cure, which meant a catastrophe to patients. So how to prevent it was more important than to cure it. As an excellent local release system, coating is a good idea by its local drug infusion and barrier effect on resisting biofilms which were the main cause of IRIs. So in this review, materials used for coatings and evidences of prevention were elaborated.

Preparation and Properties of Sodium Carboxymethyl Cellulose/Sodium Alginate/Chitosan Composite Film

A sodium alginate/chitosan solution was prepared by dissolving sodium alginate, chitosan, and glycerol in an acetic acid solution. This solution was then combined with a sodium carboxymethyl cellulose solution and the mixture was cast onto a glass plate and dried at a constant temperature of 60 °C. Then, a carboxymethyl cellulose/sodium alginate/chitosan composite film was obtained by immersing the film in a solution of a cross-linking agent, CaCl2, and air-drying the resulting material. First, the most advantageous contents of the three precursors in the casting solution were determined by a completely random design test method. Thereafter, a comprehensive orthogonal experimental design was applied to select the optimal mass ratio of the three precursors. The composite film obtained with sodium alginate, sodium carboxymethyl cellulose, and chitosan contents of 1.5%, 0.5%, and 1.5%, respectively, in the casting solution displayed excellent tensile strength, water vapor transmission rate, and elongation after fracture. Moreover, the presence of chitosan successfully inhibited the growth and reproduction of microorganisms. The composite film exhibited antibacterial rates of 95.7% ± 5.4% and 93.4% ± 4.7% against Escherichia coli and Staphylococcus aureus, respectively. Therefore, the composite film is promising for antibacterial food packaging applications.

Biopolymers: Applications in wound healing and skin tissue engineering

Wound is a growing healthcare challenge affecting several million worldwide. Lifestyle disorders such as diabetes increases the risk of wound complications. Effective management of wound is often difficult due to the complexity in the healing process. Addition to the conventional wound care practices, the bioactive polymers are gaining increased importance in wound care. Biopolymers are naturally occurring biomolecules synthesized by microbes, plants and animals with highest degree of biocompatibility. The bioactive properties such as antimicrobial, immune-modulatory, cell proliferative and angiogenic of the polymers create a microenvironment favorable for the healing process. The versatile properties of the biopolymers such as cellulose, alginate, hyaluronic acid, collagen, chitosan etc have been exploited in the current wound care market. With the technological advances in material science, regenerative medicine, nanotechnology, and bioengineering; the functional and structural characteristics of biopolymers can be improved to suit the current wound care demands such as tissue repair, restoration of lost tissue integrity and scarless healing. In this review we highlight on the sources, mechanism of action and bioengineering approaches adapted for commercial exploitation.