Robust microfluidic construction of hybrid microfibers based on konjac glucomannan and their drug release performance

Advances in the construction and application of konjac glucomannan-based delivery systems

Konjac glucomannan (KGM) has been widely used to deliver bioactive components due to its naturalness, non-toxicity, excellent biodegradability, biocompatibility, and other characteristics. This review presents an overview of konjac glucomannan as a matrix, and the types of konjac glucomannan-based delivery systems (such as hydrogels, food packaging films, microencapsulation, emulsions, nanomicelles) and their construction methods are introduced in detail. Furthermore, taking polyphenol compounds, probiotics, flavor substances, fatty acids, and other components as representatives, the applied research progress of konjac glucomannan-based delivery systems in food are summarized. Finally, the prospects for research directions in konjac glucomannan-based delivery systems are examined, thereby providing a theoretical basis for expanding the application of konjac glucomannan in other industries, such as food and medicine.

Smart and Multifunctional Materials Based on Electroactive Poly(vinylidene fluoride): Recent Advances and Opportunities in Sensors, Actuators, Energy, Environmental, and Biomedical Applications

From scientific and technological points of view, poly(vinylidene fluoride), PVDF, is one of the most exciting polymers due to its overall physicochemical characteristics. This polymer can crystalize into five crystalline phases and can be processed in the form of films, fibers, membranes, and specific microstructures, being the physical properties controllable over a wide range through appropriate chemical modifications. Moreover, PVDF-based materials are characterized by excellent chemical, mechanical, thermal, and radiation resistance, and for their outstanding electroactive properties, including high dielectric, piezoelectric, pyroelectric, and ferroelectric response, being the best among polymer systems and thus noteworthy for an increasing number of technologies. This review summarizes and critically discusses the latest advances in PVDF and its copolymers, composites, and blends, including their main characteristics and processability, together with their tailorability and implementation in areas including sensors, actuators, energy harvesting and storage devices, environmental membranes, microfluidic, tissue engineering, and antimicrobial applications. The main conclusions, challenges and future trends concerning materials and application areas are also presented.

[One-step generation of droplet-filled hydrogel microfibers for 3D cell culture using an all-aqueous microfluidic system]

Hydrogel microfibers, which are characterized by flexible mechanical properties, a uniform spatial distribution, large surface areas, and excellent biocompatibility, hold great potential for various biomedical applications. However, the fabrication of heterogeneous hydrogel microfibers with high cell-loading capacity and the ability to carry multiple components via an environmentally friendly method remains challenging. In this study, we developed a novel pneumatic pump-assisted all-aqueous microfluidic system that enables the one-step fabrication of all-aqueous droplet-filled hydrogel microfibers with unique morphologies and adjustable configurations. By designing a pump-valve cycling system and selecting two immiscible fluids with stable water interfaces (dextran and polyethylene glycol), we successfully fabricated alginate microfibers with equidistantly arranged droplets through the ionotropic gelation reaction between sodium alginate and calcium chloride. The droplet size, interdroplet spacing, and microfiber dimensions could be flexibly controlled by adjusting the flow rates of the inner-phase, middle-phase, and outer-phase inlets. The results showed that the system enabled the high-throughput in situ formation of functional three-dimensional cell spheroids. The generated cell spheroids exhibited excellent cell viability and drug-testing functionality, indicating their potential applications in cell cultures. The developed technique offers strong support for future biomedical research and applications, and provides a new approach for the preparation of multifunctional hydrogel microfibers for materials science, tissue engineering, and drug testing.

Robust microfluidic construction of polyvinyl pyrrolidone microfibers incorporated with W/O emulsions stabilized by amphiphilic konjac glucomannan

In this work, we prepared polyvinyl pyrrolidone (PVP) microfibers incorporated water-in-oil (W/O) emulsions. The W/O emulsions were fabricated by hexadecyl konjac glucomannan (HKGM, emulsifier), corn oil (oil phase) and purple corn anthocyanins (PCAs, water phase). The structures and functions of emulsions and microfibers were characterized by confocal laser scanning (CLSM) and scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), Raman and nuclear magnetic resonance (NMR) spectroscopy. The results showed that W/O emulsions exhibited good storage stability for 30 d. Microfibers presented ordered and uniform arrays. Compared with pure PVP microfiber films, the addition of W/O emulsions with PCAs improved the water resistance (WVP from 1.28 to 0.76 g mm/m² day kPa), mechanical strength (Elongation at break from 18.35 % to 49.83 %), antioxidation (free radical scavenging rate from 2.58 % to 16.37 %), and antibacterial activity (inhibition zone against E. coli: 27.33 mm and inhibition zone against S. aureus: 28.33 mm) of microfiber films. Results showed that microfiber film exhibited controlled release of PCAs in W/O emulsions, and about 32 % of the PCAs were released from the microfiber film after 340 min. The as-prepared microfiber films exhibited potential applications for food packaging.

Recent Trends of Microfluidics in Food Science and Technology: Fabrications and Applications

The development of novel materials with microstructures is now a trend in food science and technology. These microscale materials may be applied across all steps in food manufacturing, from raw materials to the final food products, as well as in the packaging, transport, and storage processes. Microfluidics is an advanced technology for controlling fluids in a microscale channel (1~100 μm), which integrates engineering, physics, chemistry, nanotechnology, etc. This technology allows unit operations to occur in devices that are closer in size to the expected structural elements. Therefore, microfluidics is considered a promising technology to develop micro/nanostructures for delivery purposes to improve the quality and safety of foods. This review concentrates on the recent developments of microfluidic systems and their novel applications in food science and technology, including microfibers/films via microfluidic spinning technology for food packaging, droplet microfluidics for food micro-/nanoemulsifications and encapsulations, etc.

Porous hollow fibers with controllable structures templated from high internal phase emulsions

A technique to fabricate hollow fibers with porous walls via templating from high internal phase emulsions (HIPEs) has been demonstrated. This technique provides an environmentally friendly process alternative to conventional methods for hollow-fiber productions that typically use organic solvents. HIPEs containing acrylate monomers were extruded into an aqueous curing bath. Osmotic pressure effects, manipulated through differences in salt concentration between the curing bath and the aqueous phase within the HIPE were used to control the hollow structures of polyHIPE fibers. The technique was used to produce porous fibers (with millimeter-scale diameters and micronscale pores) having a hollow core (with a diameter of 50%-75% of the fiber diameter). Two potential applications of the hollow fibers were demonstrated. In vitro drug release studies using these hollow fibers show a controlled release profile that is consistent with the microstructure of the porous fiber wall. In addition, the presence of pores in the walls of polyHIPE fibers also enable size-selective loading and separation of functional materials from an external suspension.

A flexible microfluidic strategy to generate grooved microfibers for guiding cell alignment

Hydrogel microfibers are widely applied in tissue engineering and regenerative medicine due to their tunable morphology, componential anisotropy, and good biocompatibility. Specifically, grooved microfibers with unique advantages can facilitate cell alignment for mimicking the microstructures of myobundles. Herein, a microfluidic spinning system is proposed for flexibly generating grooved microfibers relying on the volume change after ionic crosslinking of sodium alginate (NaA) with different concentrations. In the system, multiple parallel channels are integrated into a flow-focusing microchip and NaA with various concentrations is introduced into the respective channels for fabricating well-defined microfibers. The size and shape of the fibers are tuned by the viscosity and concentration of the NaA solution, as well as the flow rates of NaA and calcium chloride (CaCl2) in a controllable manner. Moreover, the grooved fibers with heterogeneous components can be generated via co-spinning gelatin methacrylate (GelMA) and NaA to form interpenetrating polymer networks (IPNs). The microfibers with heterogeneous IPNs are successfully used as anisotropic scaffolds for the 3D culture of muscle cells (C2C12). The muscle cells grown on the microfibers exhibited good viability and ordered alignment, indicating the good biocompatibility and orientational function of the heterogeneous fibers. The proposed approach is flexible and controllable, holding potential in replicating various aligned microstructures in vivo, such as bundles of nerves and blood vessels.

Enhanced functional properties of chitosan films incorporated with curcumin-loaded hollow graphitic carbon nitride nanoparticles for bananas preservation

The exploration of novel functional packaging films is of great scientific and technological interest. Herein, a novel chitosan/hollow g-C₃N₄/curcumin (CS-HCNS-Cur) biocomposite films was successful fabricated with integrated functions of slow release, antimicrobial activity and food freshness preservation. CS-HCNS-Cur films take the advantages of the excellent thermal stability and slow-release ability of HCNS to curcumin. Among the characterizations including scanning electron microscopy, transmission electron microscope, atomic force microscopy, fourier transform infrared spectroscopy, mechanical properties and the rheological properties measurements confirmed the successful fabrication of CS-HCNS-Cur films. The averaged water contact angle and water vapor permeability of this film were 105.83° and 105.03 × 10^-5 g·mm (m²·h·kPa)^-1, respectively. This film showed pH-responsive and slow-release ability. Moreover, this film can effectively store bananas for 10 days. Therefore, CS-HCNS-Cur films have promising potential for applications in functional food packaging.

Visible light responsive, self-activated bionanocomposite films with sustained antimicrobial activity for food packaging

The research on a new type of low-cost, less-loss and adjustable sustained antibacterial activity food packaging films with self-activation ability and great industrialization potentiality is of great scientific and technological interest. Herein, a novel chitosan/negatively charged graphitic carbon nitride self-activation bionanocomposite films was prepared by one-step electrostatic self-assembly. First, the antibacterial efficiency of this film could reach to 99.8 ± 0.26% against E. coli and 99.9 ± 0.04% against S. aureus through self-activated under visible light. Second, this film can effectively extend the shelf life of tangerines to 24 days. Hemolysis and cell experiment test proved that this film was safe and nontoxic. Finally, negatively charged graphitic carbon nitride with low-cost can improve the mechanical, thermal and hydrophobic properties of neat chitosan films. This work can provide a new pathway for the preparation of low-cost packaging films with excellent visible light responsive property and sustainable antibacterial activity.

Enhanced antimicrobial activity of konjac glucomannan nanocomposite films for food packaging

This paper aims at providing a new strategy for developing konjac glucomannan-based antibacterial films with excellent performances. Here, novel nanocomposite films based on photodynamic and photothermal synergism strategy were developed by incorporating graphite carbon nitride nanosheets/MoS₂ nanodots (CNMo) into konjac glucomannan (KGM) matrix. Scanning electron microscope, transmission electron microscope, high resolution transmission, high angle annular dark field and element mapping confirmed the successful fabrication of CNMo. The steady and dynamic rheological behavior as well as the good stability of film-forming solution showed that the intermolecular hydrogen bonding was formed. The influences of CNMo content on the structural, mechanical and thermal properties as well as hydrophobicity of KGM films were investigated. This film has a broad-spectrum antibacterial activity. It could prolong the shelf life of cherry tomatoes. Moreover, hemolysis and cells experiment confirm that this film is safe. This strategy is expected to broaden the application of antibacterial packaging.

Review of microfluidic approaches for fabricating intelligent fiber devices: importance of shape characteristics

Shape characteristics, which include the physical dimensions (scale), apparent morphology, surface features, and structure, are essential factors of fibrous materials and determine many of their properties. Microfluidic technologies have recently been proposed as an approach for producing one-dimensional (1D) fibers with controllable shape characteristics and particle alignment, which impart specific functionality to the fiber. Moreover, superfine 1D fibers with a high surface area and ordered structure have many potential applications as they can be directly braided or woven into textiles, clothes, and tissues with two- or three-dimensional (2D or 3D) structures. Previous reviews of microfluidic spinning have not focus on the importance of the shape characteristic on fiber performance and their use in intelligent fiber design. Here, the latest achievements in microfluidic approaches for fiber-device fabrication are reviewed considering the underlying preparation principles, shape characteristics, and functionalization of the fibers. Additionally, intelligent fiber devices with shapes tailored by microfluidic approaches are discussed, including 1D sensors and actuators, luminous fibers, and devices for encoding, energy harvesting, water collection, and tissue engineering applications. Finally, recent progress, challenges, and future perspectives of the microfluidic approaches for fiber device fabrication are discussed.

Konjac glucomannan/polyvinyl alcohol nanofibers with enhanced skin healing properties by improving fibrinogen adsorption

Skin tissue engineering aims to develop the effective healing strategy to repair the wound by optimizing skin scaffold materials. During the skin wound healing process, fibrin plays an important role due to the specific blood coagulation effect. In this study, the outstanding fibrin capability of konjac glucomannan (KGM) is demonstrated by the molecular dynamics simulation and confirmed by the protein adsorption experiments. A series of konjac glucomannan/polyvinyl alcohol (KGM/PVA) composites with different ratio are fabricated and their role in enhancing the skin repair is tested by in vitro cell culture and in vivo study. The E_ads (adsorption energy) between fibrin and KGM is about 30% larger than that between fibrin and PVA. The fibrinogen adsorption rates of PVA and KGM/PVA (5:5) composites can reach about 20% and 60%, respectively. The results show the blood adsorption capacity of KGM/PVA (5:5) composite can reach about 13 g/g. After 7 days of cell culture, the optical density values of 3T3 fibroblasts on KGM/PVA (5:5) composite could reach 0.8. The mechanical properties of the composites are also verified to meet the practical needs. Thus, we propose a potential wound dressing material strategy based on the materials design and the intrinsic properties of KGM.

Microfluidic spinning of poly (methyl methacrylate)/konjac glucomannan active food packaging films based on hydrophilic/hydrophobic strategy

Here, inspired by the hydrophilic/hydrophobic theory, a novel konjac glucomannan/poly (methyl methacrylate)/chlorogenic acid (KGM/PMMA/CGA) food packaging film was successfully fabricated via microfluidic spinning technology (MST). The results of fourier transform infrared spectroscopy and x-ray diffraction confirmed the formation of hydrogen bonds in the films, which lead to the enhanced mechanical properties. Thermogravimetric analysis and differential scanning calorimetry showed excellent thermal stability of the films. Water vapor permeability (1.47 × 10^-5 ± 0.11 g/(m⋅h⋅kPa)) and water contact angle (89.2°) measurement proved that the films were hydrophobic. The good swelling degree (85.18 ± 15.65%) indicated film's potentials in releasing CGA. More importantly, KGM played a key role in the antibacterial activities against Staphylococcus aureus (8.5 ± 3.5 mm) and Escherichia coli (6.5 ± 2.1 mm) by utilizing its hydrophilicity. Thus, our present work may provide a new idea for constructing active food packaging films with significant performances based on hydrophilic/hydrophobic strategy.