The preparation, resources, applications, and future trends of nanofibers in active food packaging: a review.

Active packaging is a novel strategy for maintaining the shelf life of products and ensuring their safety, freshness, and integrity that has emerged with the consumer demand for safer, healthier, and higher quality food. Nanofibers have received a lot of attention for the application in active food packaging due to their high specific surface area, high porosity, and high loading capacity of active substances. Three common methods (electrospinning, solution blow spinning, and centrifugal spinning) for the preparation of nanofibers in active food packaging and their influencing parameters are presented, and advantages and disadvantages between these methods are compared. The main natural and synthetic polymeric substrate materials for the nanofiber preparation are discussed; and the application of nanofibers in active packaging is elaborated. The current limitations and future trends are also discussed. There have been many studies on the preparation of nanofibers using substrate materials from different sources for active food packaging. However, most of these studies are still in the laboratory research stage. Solving the issues of preparation efficiency and cost of nanofibers is the key to their application in commercial food packaging.

Electrospinning is the most used method to produce nanofibers for food packagingSolution blow and centrifugal spinning are novel for large-scale nanofiber productionA variety of natural and synthetic polymers have been used for nanofiber productionProgress has been made in the development of antimicrobial and antioxidant nanofibersEthylene removal and moisture removal nanofibers have been successfully produced.

Evaluation of polycaprolactone nanofibers' spinnability using green solvent systems by solution blow spinning (SBS).

Solution blow spinning (SBS) is a promising alternative to produce fibrous matrices for a wide range of applications, such as packaging and biomedical devices. Polycaprolactone (PCL) is a biodegradable polyester commonly used for spinning. The usual choices for producing PCL solutions include chlorinated solvents (CS), such as chloroform. However, the high toxicity of CS makes it difficult for biological and green applications. This work evaluates the influence of two less toxic solvents, acetic acid (AA) and acetone (Acet), and their mixtures (AA/Acet) on the properties of PCL fibers produced by SBS. The results showed that Acet does not cause degradation of the PCL chains, in opposition to AA. Furthermore, adding acetone to the acetic acid tended to preserve the size of PCL chains. It was not possible to produce fibers using PCL in 100% acetone. However, the AA/Acet mixture allowed the efficient production of PCL fibers. The proportion of Acet and AA in the mixture modulated the fiber morphology and orientation, making it possible to use this green solvent system according to the desired application.

Advances in Biomedical Applications of Solution Blow Spinning.

In recent years, Solution Blow Spinning (SBS) has emerged as a new technology for the production of polymeric, nanocomposite, and ceramic materials in the form of nano and microfibers, with similar features to those achieved by other procedures. The advantages of SBS over other spinning methods are the fast generation of fibers and the simplicity of the experimental setup that opens up the possibility of their on-site production. While producing a large number of nanofibers in a short time is a crucial factor in large-scale manufacturing, in situ generation, for example, in the form of sprayable, multifunctional dressings, capable of releasing embedded active agents on wounded tissue, or their use in operating rooms to prevent hemostasis during surgical interventions, open a wide range of possibilities. The interest in this spinning technology is evident from the growing number of patents issued and articles published over the last few years. Our focus in this review is on the biomedicine-oriented applications of SBS for the production of nanofibers based on the collection of the most relevant scientific papers published to date. Drug delivery, 3D culturing, regenerative medicine, and fabrication of biosensors are some of the areas in which SBS has been explored, most frequently at the proof-of-concept level. The promising results obtained demonstrate the potential of this technology in the biomedical and pharmaceutical fields.

Release Profiles of Carvacrol or Chlorhexidine of PLA/Graphene Nanoplatelets Membranes Prepared Using Electrospinning and Solution Blow Spinning: A Comparative Study.

Nanofibrous membranes are often the core components used to produce devices for a controlled release and are frequently prepared by electrospinning (ES). However, ES requires high production times and costs and is not easy to scale. Recently, solution blow spinning (SBS) has been proposed as an alternative technique for the production of nanofibrous membranes. In this study, a comparison between these two techniques is proposed. Poly (lactic acid)-based nanofibrous membranes were produced by electrospinning (ES) and solution blow spinning (SBS) in order to evaluate the different effect of liquid (carvacrol, CRV) or solid (chlorhexidine, CHX) molecules addition on the morphology, structural properties, and release behavior. The outcomes revealed that both ES and SBS nanofibrous mat allowed for obtaining a controlled release up to 500 h. In detail, the lower wettability of the SBS system allowed for slowing down the CRV release kinetics, compared to the one obtained for ES membranes. On the contrary, with SBS, a faster CHX release can be obtained due to its more hydrophilic behavior. Further, the addition of graphene nanoplatelets (GNP) led to a decrease in wettability and allowed for a slowing down of the release kinetics in the whole of the systems.

Fully Fibrous Large-Area Tailorable Triboelectric Nanogenerator Based on Solution Blow Spinning Technology for Energy Harvesting and Self-Powered Sensing.

An all-fibrous large-area (20 × 50 cm2 ) tailorable triboelectric nanogenerator (LT-TENG) is prepared using a one-step solution blow spinning technology, which has the advantages of easy operation, scale-up in the area, and high production efficiency. The prepared LT-TENG is composed of polyvinylidene fluoride (PVDF)/MXene (Ti3 C2 Tx ) nanofibers (NFs) and conductive textile. Benefiting from the fibrous materials and large-area properties, the LT-TENG possesses the merits of good tailorability, breathability, hydrophobicity, and washability. When optimized by mixing the MXene into PVDF NFs, the LT-TENG has a preferable output and sensing property, with a detection range over 16 kPa and a relatively high sensitivity of 12.33 V KPa-1 . At maximum applied pressure, the voltage, current, and charge are 108 V, 38 µA, and 35 nC, respectively. This LT-TENG can serve as a biomechanical energy harvester when used as wearable devices with an output power density of 12.6 mW m-2 at an external load resistance of 500 MΩ, and it also has the ability of self-powered tactile sensing for pressure mapping and slide sensing. Thus, this LT-TENG exhibits great potential prospects in wearable devices, intelligent robots, and human-machine interaction.

Preparation of mango peel-waste pectin-based nanofibers by solution blow spinning (SBS).

An essential prerequisite for successful solution blow spinning (SBS) is the presence of effective molecular entanglements of polymers in the solution. However, the fabrication of biopolymer fibers is not as straightforward as synthetic polymers. Particularly for biopolymers such as pectin, molecular entanglements are essential but insufficient for successful spinning through the SBS production method. Such a challenge is due to the biopolymer's complex nature. However, incorporating an easily spinnable polymer precursor, such as polyacrylonitrile (PAN), to pectin effectively enabled the production of fibers from the SBS process. In this process, PAN-assisted pectin nanofibers are produced with average diameters ranging from 410.75 ± 3.73 to 477.09 ± 6.60 nm using a feed flow rate of 5 ml h-1, air pressure of 3 bars, syringe tip to collector distance at 30 cm, and spinning time of 10 min. PAN in DMSO solvent at different volume ratios (i.e. 35%-55% v/v) was critical in assisting pectin to produce nanofibers. The addition of a high molecular weight polymer, PAN, to pectin also improved the viscoelasticity of the solution, eventually contributing to its successful SBS process. Furthermore, the composite SBS-spun fibers obtained suggest that its formation is concentration-dependent.

Antifungal and antiocratoxigenic potential of Alpinia speciosa and Cymbopogon flexuosus essential oils encapsulated in poly(lactic acid) nanofibres against Aspergillus fungi.

Essential oils encapsulated in a polymeric matrix can be used as an alternative method to control fungi and mycotoxins. The essential oils were extracted by hydrodistillation and characterized by gas chromatography. The nanofibres were produced from poly (acid lactic) (PLA) containing essential oils by the Solution Blow Spinning method. The antifungal and antimicotoxygenic properties were evaluated against Aspergillus ochraceus and Aspergillus westerdijkiae by the fumigation method. Terpinen-4-ol (20·23%), sabinene (20·18%), 1·8-cineole (16·69%) and γ-terpinene (11·03%) were the principal compounds present in the essential oil from Alpinia speciosa, whereas citral (97·67%) was dominant from Cymbopogon flexuosus. Microscopy images showed that the addition of essential oils caused an increase in the diameter of the nanofibres. The infrared spectroscopy results indicated the presence of essential oils in the PLA nanofibres. Differential scanning calorimetry curves also indicated the existence of interactions between the essential oils and polymeric macromolecules through their plasticizing action. The hydrophobic character of nanofibres was revealed by the contact angle technique. An antifungal effect was observed, the mycelial growths (3·25-100%) and the synthesis of ochratoxin A (25·94-100%) were inhibited by the presence of the nanofibres. The results suggest that bioactive nanofibres hold promise for application to control toxigenic fungi.

Antifungal and physicochemical properties of Ocimum essential oil loaded in poly(lactic acid) nanofibers.

Poly(lactic acid) (PLA) nanofibres containing different proportions of the essential oils from Ocimum basilicum L. and Ocimum gratissimum L. were prepared by solution blow spinning method. The essential oils were extracted by hydrodistillation and characterized by gas chromatography. MEV, contact angle, DSC and FTIR were used to characterize the nanofibres. The effect of bioative nanofibres on the growth of the fungus and on the production of ochratoxin A were evaluated using the fumigation test. Linalool, 1·8-cineole and camphor were the principal components of the essential oil from O. basilicum, and eugenol was the principal constituent in the oil from O. gratissimum. An increase in the average diameter of the nanofibres was observed with the addition of the essential oils. The essential oils acted as a plasticizer, resulting in a reduction in the crystallinity of the PLA. The encapsulation of essential oils in PLA nanofibres was verified by FTIR. An effective antifungal and antimicotoxygenic activity against Aspergillus ochraceus and Aspergillus westerdjikiae was observed for the bioative nanofibres. These results confirm the potential of PLA nanofibres containing the essential oils for the control of toxigenic fungi that cause the deterioration of food and are harmful to human health.

High-Speed Blow Spinning of Neat Graphene Fibrous Materials.

Achieving high spinning speed is critical to the production efficiency and viable application of fiber species. Graphene fiber (GF) has recently emerged as a carbonaceous fiber with excellent functionality. However, the extremely low wet spinning speed of GF has limited its applications. We realized high-speed blow spinning of neat GF and fabric by modulating the rheological properties of the graphene oxide (GO) dispersion. We achieved a speed of 556 m min-1, 2 orders of magnitude faster than that for wet spinning. We chose ultrahigh molecular weight polymers as transient additives to circumvent the intrinsic barrier effect of GO and achieve high spinning dope stretchability at low polymer percentages-down to 25 wt %. Minimizing the polymer additive content ensures the high electrical/thermal conductivity of the blow-spun fiber and fabric. This work provides insight into the unique flow properties of 2D sheets and will promote the efficient production of graphene-based fibrous materials.

Chitosan-Enriched Solution Blow Spun Poly(Ethylene Oxide) Nanofibers with Poly(Dimethylsiloxane) Hydrophobic Outer Layer for Skin Healing and Regeneration.

Chitosan (CS)/poly(ethylene oxide) (PEO)-based nanofiber mats have attracted particular attention as advanced materials for medical and pharmaceutical applications. In the scope of present studies, solution blow spinning was applied to produce nanofibers from PEO and CS and physicochemical and biopharmaceutical studies were carried out to investigate their potential as wound nanomaterial for skin healing and regeneration. Additional coating with hydrophobic poly(dimethylsiloxane) was applied to favor removal of nanofibers from the wound surface. Unmodified nanofibers displayed highly porous structure with the presence of uniform, randomly aligned nanofibers, in contrast to coated materials in which almost all the free spaces were filled in with poly(dimethylsiloxane). Infrared spectroscopy indicated that solution blow technique did not influence the molecular nature of native polymers. Obtained nanofibers exhibited sufficient wound exudate absorbency, which appears beneficial to moisturize the wound bed during the healing process. Formulations displayed greater tensile strength as compared to commercial hydrofiber-like dressing materials comprised of carboxymethylcellulose sodium or calcium alginate, which points toward their protective function against mechanical stress. Coating with hydrophobic poly(dimethylsiloxane) (applied to favor nanofiber removal from the wound surface) impacted porosity and decreased both mechanical properties and adherence to excised human skin, though the obtained values were comparable to those attained for commercial hydrofiber-like materials. In vitro cytotoxicity and irritancy studies showed biocompatibility and no skin irritant response of nanofibers in contact with a reconstituted three-dimensional human skin model, while scratch assay using human fibroblast cell line HDFa revealed the valuable potential of CS/PEO nanofibers to promote cell migration at an early stage of injury.

Fibrous Nanoreactors from Microfluidic Blow Spinning for Mass Production of Highly Stable Ligand-Free Perovskite Quantum Dots.

Nano-/micro-reactors have emerged as a powerful platform for chemical synthesis. Here, we develop fiber-spinning chemistry (FSC) based on a microfluidic blow spinning (MBS) technique, allowing the availability of nanoreactors for chemical synthesis with scale-up capacities. Proof-of-concept experiments focus on the utilization of MBS-derived fibrous nanoreactors for large-scale production of ligand-free perovskite quantum dots (PQDs) in one step. Typically, methylammonium lead halide (MAPbX3 , X=Cl, Br, and I) PQDs in situ synthesized at large scale inside polyacrylonitrile (PAN) nanofiber films (size 120 cm ×30 cm per hour), exhibit high photoluminescence (PL) quantum yield (QY) of 71 %, tunable emissive peaks (448-600 nm), and superb PL stability. The PQDs/polymer nanofiber films are potentially useful for CO2 conversion, wide-color-gamut displays and light-emitting diode (LED) devices. These findings may guide the development of nano-/micro-reactor technology for scale-up production of nanomaterials with various potential applications.

Blow-Spinning Enabled Precise Doping and Coating for Improving High-Voltage Lithium Cobalt Oxide Cathode Performance.

Lithium cobalt oxide (LiCoO2) possesses an attractive theoretical specific capacity (274 mAh g-1) and high discharge voltage (∼4.2 V vs Li+/Li). However, only a half of the theoretical capacity of LiCoO2 is available in commercialized lithium ion batteries because of the intrinsic structural instability and detrimental interface of LiCoO2 at the charging voltage over 4.2 V. Here, a facile blow-spinning synthetic method is developed to realize precise doping and simultaneous self-assembly coating of LiCoO2 particles, achieving a record performance among present LiCoO2 cathodes. Owing to the spatial confinement effect of microfibers fabricated by blow-spinning, homogeneously Mn and La doped in the LiCoO2 host and uniformly Li-Ti-O segregated at the LiCoO2 surface can be realized in every batch of samples. It is demonstrated that the Mn and La codoping can suspend the intrinsic instability and increase the Li+ diffusivity of the LiCoO2 host, and the Ti-based coating can stabilize the interface of LiCoO2 particles at the charging voltage up to 4.5 V. As a result, the obtained comodified LiCoO2 cathode shows the best rate performance (1.85 mAh cm-2 at 2C) and longest cycling stability under an areal capacity of 2.04 mAh cm-2 (83% capacity retention over 300 cycles at 0.3C), in comparison to previously reported LiCoO2 cathodes.

A Foldable All-Ceramic Air Filter Paper with High Efficiency and High-Temperature Resistance.

Advanced filter materials with high efficiency, low-pressure drop, and high-temperature resistance are urgently needed in the field of high-temperature gas filtration. Here, an Al2O3-stabilized ZrO2 (ASZ) submicron fiber air filter paper with excellent flexibility and thermal stability (up to 1100 °C) is developed using a cost-effective, scalable solution blow spinning method and subsequent calcination. The ASZ papers demonstrate excellent flexibility and foldability, which can be attributed to the tetragonal phase and small crystallite size of the ASZ fibers due to the presence of Al2O3. In addition, the ASZ papers with an areal density of 56 mg cm-2 show a high filtration efficiency (99.56%) and a low-pressure drop (108 Pa) for 15-615 nm NaCl particles at an airflow velocity of 5.4 cm s-1. We envision that the foldable all-ceramic air filter material will provide a solution for the removal of particulate matter from the high-temperature exhaust gases.

Polydopamine Nanocluster Embedded Nanofibrous Membrane via Blow Spinning for Separation of Oil/Water Emulsions.

Developing a porous separation membrane that can efficiently separate oil-water emulsions still represents a challenge. In this study, nanofiber membranes with polydopamine clusters polymerized and embedded on the surface were successfully constructed using a solution blow-spinning process. The hierarchical surface structure enhanced the selective wettability, superhydrophilicity in air (≈0°), and underwater oleophobicity (≈160.2°) of the membrane. This membrane can effectively separate oil-water emulsions, achieving an excellent permeation flux (1552 Lm-2 h-1) and high separation efficiency (~99.86%) while operating only under the force of gravity. When the external driving pressure was increased to 20 kPa, the separation efficiency hardly changed (99.81%). However, the permeation flux significantly increased to 5894 Lm-2 h-1. These results show that the as-prepared polydopamine nanocluster-embedded nanofiber membrane has an excellent potential for oily wastewater treatment applications.

Evaluation of Sterilization/Disinfection Methods of Fibrous Polyurethane Scaffolds Designed for Tissue Engineering Applications.

Sterilization of a material carries the risk of unwanted changes in physical and chemical structure. The choice of method is a challenge-the process must be efficient, without significantly changing the properties of the material. In the presented studies, we analyzed the effect of selected sterilization/disinfection techniques on the properties of nanofibrous polyurethane biomaterial. Both radiation techniques (UV, gamma, e-beam) and 20 minutes' contact with 70% EtOH were shown not to achieve 100% sterilization efficiency. The agar diffusion test showed higher sterilization efficiency when using an antimicrobial solution (AMS). At the same time, none of the analyzed techniques significantly altered the morphology and distribution of fiber diameters. EtOH and e-beam sterilization resulted in a significant reduction in material porosity together with an increase in the Young's modulus. Similarly, AMS sterilization increased the value of Young's modulus. In most cases, the viability of cells cultured in contact with the sterilized materials was not affected by the sterilization process. Only for UV sterilization, cell viability was significantly lower and reached about 70% of control after 72 h of culture.

Hierarchically Porous Silk/Activated-Carbon Composite Fibres for Adsorption and Repellence of Volatile Organic Compounds.

Fabrics comprised of porous fibres could provide effective passive protection against chemical and biological (CB) threats whilst maintaining high air permeability (breathability). Here, we fabricate hierarchically porous fibres consisting of regenerated silk fibroin (RSF) and activated-carbon (AC) prepared through two fibre spinning techniques in combination with ice-templating-namely cryogenic solution blow spinning (Cryo-SBS) and cryogenic wet-spinning (Cryo-WS). The Cryo-WS RSF fibres had exceptionally small macropores (as low as 0.1 µm) and high specific surface areas (SSAs) of up to 79 m2·g-1. The incorporation of AC could further increase the SSA to 210 m2·g-1 (25 wt.% loading) whilst also increasing adsorption capacity for volatile organic compounds (VOCs).

Fabrication and Characterisation of Stimuli Responsive Piezoelectric PVDF and Hydroxyapatite-Filled PVDF Fibrous Membranes.

Poly(vinylidene fluoride) has attracted interest from the biomaterials community owing to its stimuli responsive piezoelectric property and promising results for application in the field of tissue engineering. Here, solution blow spinning and electrospinning were employed to fabricate PVDF fibres and the variation in resultant fibre properties assessed. The proportion of piezoelectric ß-phase in the solution blow spun fibres was higher than electrospun fibres. Fibre production rate was circa three times higher for solution blow spinning compared to electrospinning for the conditions explored. However, the solution blow spinning method resulted in higher fibre variability between fabricated batches. Fibrous membranes are capable of generating different cellular response depending on fibre diameter. For this reason, electrospun fibres with micron and sub-micron diameters were fabricated, along with successful inclusion of hydroxyapatite particles to fabricate stimuli responsive bioactive fibres.

High-Temperature Particulate Matter Filtration with Resilient Yttria-Stabilized ZrO2 Nanofiber Sponge.

Particulate matter (PM) is a major air pollutant in many regions, jeopardizing ecosystems and public health. Filtration at pollutant source is one of the most important ways to protect the environment, however, considering the high-temperature exhaust gas emissions, effective removal of PM and related pollutants from their sources remains a major challenge. In this study, a resilient, heat-resisting, and high-efficiency PM filter based on yttria-stabilized ZrO2 (YSZ) nanofiber sponge produced with a scalable solution blow spinning process is reported. The porous 3D sponge composed of YSZ nanofibers is lightweight (density of 20 mg cm-3 ) and resilient at both room temperature and high temperatures. At room-temperature conditions, the YSZ nanofiber sponge exhibits 99.4% filtration efficiency for aerosol particles with size in the range of 20-600 nm, associated with a low pressure drop of only 57 Pa under an airflow velocity of 4.8 cm s-1 . At a high temperature of 750 °C, the ceramic sponge maintains a high filtration efficiency of 99.97% for PM0.3-2.5 under a high airflow velocity of 10 cm s-1 . A practical vehicle exhaust filter to capture particles with filtration efficiency of >98.3% is also assembled. Hence, the YSZ nanofiber sponge has enormous potential to be applied in industry.

Direct Blow-Spinning of Nanofibers on a Window Screen for Highly Efficient PM2.5 Removal.

Particulate matter (PM) pollution has caused many serious public health issues. Whereas indoor air protection usually relies on expensive and energy-consuming filtering devices, direct PM filtration by window screens has attracted increasing attention. Recently, electrospun polymer nanofiber networks have been developed as transparent filters for highly efficient PM2.5 removal; however, it remains challenging to uniformly coat the nanofibers on window screens on a large scale and with low cost. Here, we report a blow-spinning technique that is fast, efficient, and free of high voltages for the large-scale direct coating of nanofibers onto window screens for indoor PM pollution protection. We have achieved a transparent air filter of 80% optical transparency with >99% standard removal efficiency level for PM2.5. A test on a real window (1 m × 2 m) in Beijing has proven that the nanofiber transparent air filter acquires excellent PM2.5 removal efficiency of 90.6% over 12 h under extremely hazy air conditions (PM2.5 mass concentration > 708 µg/m3). Moreover, we show that the nanofibers can be readily coated on the window screen for pollution protection and can be easily removed by wiping the screen after hazardous days.

Preparation of Fish Skin Gelatin-Based Nanofibers Incorporating Cinnamaldehyde by Solution Blow Spinning.

Cinnamaldehyde, a natural preservative that can non-specifically deactivate foodborne pathogens, was successfully incorporated into fish skin gelatin (FSG) solutions and blow spun into uniform nanofibers. The effects of cinnamaldehyde ratios (5-30%, w/w FSG) on physicochemical properties of fiber-forming emulsions (FFEs) and their nanofibers were investigated. Higher ratios resulted in higher values in particle size and viscosity of FFEs, as well as higher values in diameter of nanofibers. Loss of cinnamaldehyde was observed during solution blow spinning (SBS) process and cinnamaldehyde was mainly located on the surface of resultant nanofibers. Nanofibers all showed antibacterial activity by direct diffusion and vapor release against Escherichia coli O157:H7, Salmonella typhimurium, and Listeria monocytogenes. Inhibition zones increased as cinnamaldehyde ratio increased. Nanofibers showed larger inhibition effects than films prepared by casting method when S. typhimurium was exposed to the released cinnamaldehyde vapor, although films had higher remaining cinnamaldehyde than nanofibers after preparation. Lower temperature was favorable for cinnamaldehyde retention, and nanofibers added with 10% cinnamaldehyde ratio showed the highest retention over eight-weeks of storage. Results suggest that FSG nanofibers can be prepared by SBS as carriers for antimicrobials.