Nanoparticles meet electrospinning: recent advances and future prospects

Review on Fabrication of Structurally Colored Fibers by Electrospinning

Structural color derived from the physical interactions of photons, with the specific chromatic mechanism differing from that of dyes and pigments, has brought considerable attention by the conducive virtue of being dye-free and fadeless. This has recently become a research hot-spot. Assemblies of colloidal nanoparticles enable the manufacture of periodic photonic nanostructures. In our review, the mechanism of nanoparticle assemblies into structurally colored structures by the electrospinning method was briefly introduced, followed by a comparatively comprehensive review summarizing the research related to photonic crystals with periodically aligned nanostructures constructed by the assembly of colloidal nanoparticles, and the concrete studies concerning the fabrication of well-aligned electrospun nanofibers incorporating with colloidal nanoparticles based on the investigation of relevant factors such as the sizes of colloidal nanoparticles, the weight ratio between colloidal nanoparticles, and the polymer matrix. Electrospinning is expected to be a deserving technique for the fabrication of structurally colored nanofibers while the colloidal nanoparticles can be well confined into aligned arrangement inside nanofibres during the electrospinning process after the achievement of resolving remaining challenges.

AuNPs-PCL nanocomposite accelerated abdominal wound healing through photothermal effect and improving cell adhesion

Accelerating wound healing with modified biomaterial has been an attracting field in both material science and medicine. Enhanced cell adhesion could be acquired by improving surface hydrophilicity, which contributes to accelerating wound healing. Chemical reaction has been used for surface modification, but this study used a simple and nontoxic method to improve the hydrophilicity. Polycaprolactone (PCL) scaffold has been regarded as promising material for wound healing while its surface is hydrophobic. Our study demonstrated enhanced hydrophilicity of PCL with AuNPs coating. AuNPs has good biocompatibility and excellent photothermal effect. The coating of AuNPs not only improved the cell adhesion, but also gave PCL the ability to inhibit the growth of bacteria. Animal study showed that the nanocomposites decreased lymphocytes and neutrophils, increased neovascularization and accelerated the abdominal wound healing, which was attributed to improved hydrophilicity and the antibacterial ability. In conclusion, we demonstrated that the nanocomposite could be used as a potential scaffold for cell adhesion and wound healing, and the role of AuNPs was highlighted as a kind of outstanding supplement.

Preparation of gentamicin sulfate eluting fiber mats by emulsion and by suspension electrospinning

This work investigates the immobilization of the antibiotic gentamicin sulfate (GS) in electrospun fiber mats composed of poly(lactic acid) (PLA), poly(ε-caprolactone) (PCL) and the copolymer poly(lactic-co-glycolic acid) (PLGA). Since GS is highly water soluble but weakly soluble in the organic solvents commonly used in the electrospinning process, two methods of immobilization were investigated: by suspension electrospinning, in which GS particles were directly dispersed in the polymeric organic solutions, and by emulsion electrospinning, in which GS was solubilized in an aqueous phase that was then dispersed in the organic polymeric solution containing the surfactant SPAN80. Fibers with distinct diameters and morphologies were obtained for the different methods and compositions. Contrary to the fibers prepared by suspension electrospinning, emulsion electrospinning based fibers exhibited an excellent wettability, allegedly due to the effect of the surfactant SPAN80. Despite the differences between both methods the produced mats presented similar GS release profiles, with a considerable burst release in the first 8 h followed by a gradual release of the remaining drug during the next 4-6 days. Finally, all GS loaded fiber mats proved to have an antibacterial effect against the bacterial strain Staphylococcus aureus.

Electrospun amorphous solid dispersions of poorly water-soluble drugs: A review

The development of oral dosage forms for poorly water-soluble active pharmaceutical ingredients (APIs) is a persistent challenge. A range of methods has been explored to address this issue, and amorphous solid dispersions (ASDs) have received increasing attention. ASDs are typically prepared by starting with a liquid precursor (a solution or melt) and applying energy for solidification. Many techniques can be used, with the emergence of electrospinning as a potent option in recent years. This method uses electrical energy to induce changes from liquid to solid. Through the direct applications of electrical energy, electrospinning can generate nanofiber-based ASDs from drug-loaded solutions, melts and melt-solutions. The technique can also be combined with other approaches using the application of mechanical, thermal or other energy sources. Electrospinning has numerous advantages over other approaches to produce ASDs. These advantages include extremely rapid drying speeds, ease of implentation, compatibility with a wide range of active ingredients (including those which are thermally labile), and the generation of products with large surface areas and high porosity. Furthermore, this technique exhibits the potential to create so-called 'fifth-generation' ASDs with nanostructured architectures, such as core/shell or Janus systems and their combinations. These advanced systems can improve dissolution behaviour and provide programmable drug release profiles. Additionally, the fiber components and their spatial distributions can be precisely controlled. Electrospun fiber-based ASDs can maintain an incorporated active ingredient in the amorphous physical form for prolonged periods of time because of their homogeneous drug distribution within the polymer matrix (typically they comprise solid solutions), and ability to inhibit molecular motion. These ASDs can be utilised to generate oral dosage forms for poorly water-soluble drugs, resulting in linear or multiple-phase release of one or more APIs. Electrospun ASDs can also be exploited as templates for manipulating molecular self-assembly, offering a bridge between ASDs and other types of dosage forms. This review addresses the development, advantages and pharmaceutical applications of electrospinning for producing polymeric ASDs. Material preparation and analysis procedures are considered. The mechanisms through which performance has been improved are also discussed.

Electrospun one-dimensional nanostructures: a new horizon for gas sensing materials

Electrospun one-dimensional (1D) nanostructures are rapidly emerging as key enabling components in gas sensing due to their unique electrical, optical, magnetic, thermal, mechanical and chemical properties. 1D nanostructures have found applications in numerous areas, including healthcare, energy storage, biotechnology, environmental monitoring, and defence/security. Their enhanced specific surface area, superior mechanical properties, nanoporosity and improved surface characteristics (in particular, uniformity and stability) have made them important active materials for gas sensing applications. Such highly sensitive and selective elements can be embedded in sensor nodes for internet-of-things applications or in mobile systems for continuous monitoring of air pollutants and greenhouse gases as well as for monitoring the well-being and health in everyday life. Herein, we review recent developments of gas sensors based on electrospun 1D nanostructures in different sensing platforms, including optical, conductometric and acoustic resonators. After explaining the principle of electrospinning, we classify sensors based on the type of materials used as an active sensing layer, including polymers, metal oxide semiconductors, graphene, and their composites or their functionalized forms. The material properties of these electrospun fibers and their sensing performance toward different analytes are explained in detail and correlated to the benefits and limitations for every approach.

Piezoelectric Polyacrylonitrile Nanofiber Film-Based Dual-Function Self-Powered Flexible Sensor

To meet the growing demands in flexible and wearable electronics, various sensors have been designed for detecting and monitoring the physical quantity changes. However, most of these sensors can only detect one certain kind of physical quantity based on a single mechanism. In this paper, we have fabricated a multifunctional sensor made from carbonized electrospun polyacrylonitrile/barium titanate (PAN-C/BTO) nanofiber film. It can detect two physical quantities (pressure and curvature), independently and simultaneously, by integrating piezoresistive, piezoelectric, and triboelectric effects. For flex sensing with the impedance change of PAN-C/BTO nanofiber films during bending, it had a sensitivity of 1.12 deg^-1 from 58.9° to 120.2° and a working range of 28°-150°. For self-powered force sensing, it had a gauge factor of 1.44 V·N^-1 within the range of 0.15-25 N. The sensor had a long stability over 60 000 cycles at both sensing modes. The inclusion of barium titanate nanoparticles (BTO NPs) into the nanofiber film had an over 2.4 times enhancement of sensitivity for pressure sensing because of the synergy of piezoelectric and triboelectric effects. On the basis of multifunction and modularity, a series of potential applications of the sensor were demonstrated, including sensing human's swallowing, walking gaits, finger flexure, and finger-tapping. The self-powered flexible dual-mode sensor has great application potential in human-computer interactive and smart wearable sensing systems.

Electrospun Gelatin Membrane Cross-Linked by a Bis(diarylcarbene) for Oil/Water Separation: A New Strategy To Prepare Porous Organic Polymers

Porous organic polymers (POPs) as absorbing materials have attracted increasing attention. Here, we report a new approach to prepare these polymers for selective oil absorption from oil/water mixtures. Perfluoroalkylbis(diaryldiazomethane) was synthesized and used to modify the surface of an electrospun gelatin membrane by a carbene insertion reaction, not only to immobilize the porous network morphology by cross-linking but also to introduce perfluoroalkyl groups for oil/water separation. The membrane was characterized to show its surface and bulk properties, as well as its performance for absorption capacity, selectivity, and renewability. This approach offers a new horizon in the preparation of POPs for oil/water separation.

Electrospun plant mucilage nanofibers as biocompatible scaffolds for cell proliferation

Electrospun nanofibers (ESNFs) were prepared from mucilage isolated from chan and linaza beans and mozote stem commercially available in Costa Rica. Poly(vinyl alcohol) (PVA) was used as an aiding agent. Mucilage/PVA mixed solutions of different volume ratios (100:0, 80:20, 60:40, 40:60, 20:80 and 0:100) were prepared and adjusted to be similar in viscosity and electrical conductivity suitable for electrospinning. Morphology of the ESNFs was examined using scanning electron microscopy (SEM). Fourier transform infrared spectrometer (FTIR) and differential scanning calorimetry (DSC) studies were used to characterize chemical composition and thermal characteristics of the nanofibers (NFs). The ability of the NFs to support fibroblast cell proliferation was investigated in vitro using the optimized mucilage/PVA solutions. Results show plant mucilage-based ESNFs are well-suited for fibroblast cell growth, significantly better than ESNFs of PVA; and the mucilage of chan beans is better than those of mozote and linaza for supporting cell proliferation.

Electrospun poly(lactic acid) fibers containing novel chlorhexidine particles with sustained antibacterial activity

The treatment of persistent infections often requires a high local drug concentration and sustained release of antimicrobial agents. This paper proposes the use of novel electrospinning of poly(lactic acid) (PLA) fibers containing uncoated and encapsulated chlorhexidine particles. Chlorhexidine particles with a mean (SD) diameter of 17.15 ± 1.99 μm were fabricated by the precipitation of chlorhexidine diacetate with calcium chloride. Layer-by-layer (LbL) encapsulation of the chlorhexidine particles was carried out to produce encapsulated particles. The chlorhexidine particles had a high chlorhexidine content (90%), and when they were electrospun into PLA fibers a bead-in-string structure was obtained. The chlorhexidine content in the fibers could be tuned and a sustained release over 650 h was produced, via chlorhexidine particle encapsulation. Chlorhexidine release was governed by the polyelectrolyte multilayer encapsulation as demonstrated by SEM and confocal imaging. The incorporation of uncoated and encapsulated chlorhexidine particles (0.5% and 1% wt/wt chlorhexidine) into the fibers did not cause toxicity to healthy fibroblasts or affect cell adhesion to the fibers over a period of 5 days. The chlorhexidine-containing fibers also demonstrated sustained antibacterial activity against E. coli via an agar diffusion assay and broth transfer assay. Therefore, the chlorhexidine-containing PLA fibers may be useful in the treatment of persistent infections in medicine and dentistry.

Biomimetic polyurethane/TiO2 nanocomposite scaffolds capable of promoting biomineralization and mesenchymal stem cell proliferation

Scaffolds with extracellular matrix-like fibrous morphology, suitable mechanical properties, biomineralization capability, and excellent cytocompatibility are desired for bone regeneration. In this work, fibrous and degradable poly(ester urethane)urea (PEUU) scaffolds reinforced with titanium dioxide nanoparticles (nTiO2) were fabricated to possess these properties. To increase the interfacial interaction between PEUU and nTiO2, poly(ester urethane) (PEU) was grafted onto the nTiO2. The scaffolds were fabricated by electrospinning and exhibited fiber diameter of <1μm. SEM and EDX mapping results demonstrated that the PEU modified nTiO2 was homogeneously distributed in the fibers. In contrast, severe agglomeration was found in the scaffolds with unmodified nTiO2. PEU modified nTiO2 significantly increased Young's modulus and tensile stress of the PEUU scaffolds while unmodified nTiO2 significantly decreased Young's modulus and tensile stress. The greatest reinforcement effect was observed for the scaffold with 1:1 ratio of PEUU and PEU modified nTiO2. When incubating in the simulated body fluid over an 8-week period, biomineralization was occurred on the fibers. The scaffolds with PEU modified nTiO2 showed the highest Ca and P deposition than pure PEUU scaffold and PEUU scaffold with unmodified nTiO2. To examine scaffold cytocompatibility, bone marrow-derived mesenchymal stem cells were cultured on the scaffold. The PEUU scaffold with PEU modified nTiO2 demonstrated significantly higher cell proliferation compared to pure PEUU scaffold and PEUU scaffold with unmodified nTiO2. The above results demonstrate that the developed fibrous nanocomposite scaffolds have potential for bone tissue regeneration.

Micro and nanotechnologies for bone regeneration: Recent advances and emerging designs

Treatment of critical-size bone defects is a major medical challenge since neither the bone tissue can regenerate nor current regenerative approaches are effective. Emerging progresses in the field of nanotechnology have resulted in the development of new materials, scaffolds and drug delivery strategies to improve or restore the damaged tissues. The current article reviews promising nanomaterials and emerging micro/nano fabrication techniques for targeted delivery of biomolecules for bone tissue regeneration. In addition, recent advances in fabrication of bone graft substitutes with similar properties to normal tissue along with a brief summary of current commercialized bone grafts have been discussed.

Modeling Nanoparticle Dispersion in Electrospun Nanofibers

The quality of nanoparticle dispersion in a polymer matrix significantly influences the macroscopic properties of the composite material. Like general polymer-nanoparticle composites, electrospun nanofiber nanoparticle composites do not have an adopted quantitative model for dispersion throughout the polymer matrix, often relying on a qualitative assessment. Being such an influential property, quantifying dispersion is essential for the process of optimization and understanding the factors influencing dispersion. Here, a simulation model was developed to quantify the effects of nanoparticle volume loading (ϕ) and fiber-to-particle diameter ratios (D/d) on the dispersion in an electrospun nanofiber based on the interparticle distance. A dispersion factor is defined to quantify the dispersion along the polymer fiber. In the dilute regime (ϕ < 20%), three distinct regions of the dispersion factor were defined with the highest quality dispersion shown to occur when geometric constraints limit fiber volume accessibility. This model serves as a standard for comparison for future experimental studies and dispersion models through its comparability with microscopy techniques and as a way to quantify and predict dispersion in electrospinning polymer-nanoparticle systems with a single performance metric.

Plasma-treated electrospun nanofibers as a template for the electrostatic assembly of silver nanoparticles

Silver nanoparticles assembled on a plasma treated electrospun nanofiber membrane could show excellent SERS effect.

Encoding materials for programming a temporal sequence of actions

Materials are usually synthesized to allow a function that is either independent of time or that can be triggered in a specific environment.

Design of functional electrospun nanofibers for cancer cell capture applications

The review reports recent advances in the design of functional electrospun nanofibers for cancer cell capture applications.

A 3D printed wound cooling system incorporated with injectable, adsorbable, swellable and broad spectrum antibacterial scaffolds for rapid hematischesis processing

Uncontrolled hemorrhage remains a leading cause of early death after trauma, and contamination further challenges the wounded.

Flexible Electrodes for Sodium-Ion Batteries: Recent Progress and Perspectives

Sodium-ion batteries (SIBs) are considered as promising alternatives to lithium-ion batteries (LIBs) for large-scale electrical-energy-storage applications due to the wide availability and the low cost of Na resources. Along with the avenues of research on flexible LIBs, flexible SIBs are now being actively developed as one of the most promising power sources for the emerging field of flexible and wearable electronic devices. Here, the recent progress on flexible electrodes based on metal substrates, carbonaceous substrates (i.e., graphene, carbon cloth, and carbon nanofibers), and other materials, as well as their applications in flexible SIBs, are summarized. Also, some future research directions for constructing flexible SIBs are proposed, with the aim of providing inspiration to the further development of advanced flexible SIBs.

Electrospun Polymer Nanofibers Decorated with Noble Metal Nanoparticles for Chemical Sensing

The integration of different noble metal nanostructures, which exhibit desirable plasmonic and/or electrocatalytic properties, with electrospun polymer nanofibers, which display unique mechanical and thermodynamic properties, yields novel hybrid nanoscale systems of synergistic properties and functions. This review summarizes recent advances on how to incorporate noble metal nanoparticles into electrospun polymer nanofibers and illustrates how such integration paves the way towards chemical sensing applications with improved sensitivity, stability, flexibility, compatibility, and selectivity. It is expected that further development of this field will eventually make a wide impact on many areas of research.

Synthesis and Electrochemical Property of LiMn2O4 Porous Hollow Nanofiber as Cathode for Lithium-Ion Batteries

The LiMn2O4 hollow nanofibers with a porous structure have been synthesized by modified electrospinning techniques and subsequent thermal treatment. The precursors were electrospun directly onto the fluorine-doped tin oxide (FTO) glass. The heating rate and FTO as substrate play key roles on preparing porous hollow nanofiber. As cathode materials for lithium-ion batteries (LIBs), LiMn2O4 hollow nanofibers showed the high specific capacity of 125.9 mAh/g at 0.1 C and a stable cycling performance, 105.2 mAh/g after 400 cycles. This unique structure could relieve the structure expansion effectively and provide more reaction sites as well as shorten the diffusion path for Li+ for improving electrochemical performance for LIBs.

Electrospinning onto Insulating Substrates by Controlling Surface Wettability and Humidity

We report a simple method for electrospinning polymers onto flexible, insulating substrates by controlling the wettability of the substrate surface. Water molecules were adsorbed onto the surface of a hydrophilic polymer substrate by increasing the local humidity around the substrate. The adsorbed water was used as the ground electrode for electrospinning. The electrospun fibers were deposited only onto hydrophilic areas of the substrate, allowing for patterning through wettability control. Direct writing of polymer fiber was also possible through near-field electrospinning onto a hydrophilic surface.

Multichannel Discriminative Detection of Explosive Vapors with an Array of Nanofibrous Membranes Loaded with Quantum Dots

The multichannel fluorescent sensor array based on nanofibrous membranes loaded with ZnS quantum dots (QDs) was created and demonstrated for the discriminative detection of explosives. The synergistic effect of the high surface-to-volume ratio of QDs, the good permeability of nanofibrous membranes and the differential response introduced by surface ligands was played by constructing the sensing array using nanofibrous membranes loaded with ZnS QDs featuring several surface ligands. Interestingly, although the fluorescence quenching of the nanofibrous membranes is not linearly related to the exposure time, the fingerprint of each explosive at different times is very similar in shape, and the fingerprints of the three explosives show different shapes. Three saturated vapors of nitroaromatic explosives could be reliably detected and discriminated by the array at room temperature. This work is the first step toward devising a monitoring system for explosives in the field of public security and defense. It could, for example, be coupled with the technology of image recognition and large data analysis for a rapid diagnostic test of explosives. This work further highlights the power of differential, multichannel arrays for the rapid and discriminative detection of a wide range of chemicals.

Monomer: Design of ZnO Nanostructures (Nanobush and Nanowire) and Their Room-Temperature Ethanol Vapor Sensing Signatures

Ethanol serves as a biomarker as well as a chemical reagent for several applications and has been predominantly used as an alternative fuel (E10 and E85). Development of sensors for the detection and monitoring of ethanol vapor at lower operating temperatures has gathered momentum in the recent past. In this work, we reported the synthesis of self-assembled ZnO nanowires using electrospun technique without using any external surfactants or capping agents and their room temperature ethanol sensing properties. An inherent template namely monomer of the polymer poly(vinyl alcohol) (PVA) with two different molecular weights (14 000 and 140 000 g mol^-1) was used along with the precursor zinc acetate dihydrate. The ZnO-PVA nanofibers have been tranformed to ZnO nanospheres and nanowires after calcination. The ratio of zinc precursor concentration to PVA polymer led to the enhanced carrier concentration of the resultant ZnO nanowire that enhanced, in turn, the sensing response toward ethanol vapor. The developed sensing elements have been systematically characterized to correlate their structural, morphological, and electrical properties with the respective room-temperature ethanol-sensing characteristics. The role of grain features and low activation energy of ZnO nanowires in coordination with the low dipole moment of ethanol resulted in the excellent response of 78 toward 100 ppm at room temperature with ultra-sensitive response and recovery times (9 and 12 s, respectively).

Nanofibrous photocatalysts from electrospun nanocapsules

We present the design of multicompartment metal oxide/silica nanofibrous photocatalysts by colloid-electrospinning and subsequent calcination. During the calcination process, silica nanomaterials are cemented to form the fibrous framework and metal oxide precursors are crystallized inside and onto the fibers. This multicompartment nanofibrous structure, constructed with nanoparticles and core-shell nanocapsules, is therefore beneficial for the separation of the materials and the light utilization due to the multiple reflections and scattering of incident light in the cavities. The photocatalytic activity of the fibers was verified by the successful degradation of a model dye rhodamine B. This synthetic methodology is a universal approach for the fabrication of nanomaterials with hierarchical hollow structures, which are emerging in energy and environmental related applications.

Structural Evolution and Formation Mechanism of the Soft Colloidal Arrays in the Core of PAAm Nanofibers by Electrospun Packing

Electrospinning provides a facile and versatile method for generating nanofibers from a large variety of starting materials, including polymers, ceramic, composites, and micro-/nanocolloids. In particular, incorporating functional nanoparticles (NPs) with polymeric materials endows the electrospun fibers/sheets with novel or better performance. This work evaluates the spinnability of polyacrylamide (PAAm) solution containing thermoresponsive poly(N-isopropylacrylamide-co-tert-butyl acrylate) microgel nanospheres (PNTs) prepared by colloid electrospinning. In the presence of a suitable weight ratio (1:4) of PAAm and PNTs, the in-fiber arrangements of PNTs-electrospun fibers will evolve into chain-like arrays and beads-on-string structures by confining of PAAm nanofibers, and then the free amide groups of PAAm can bind amide moieties on the surfaces of PNTs, resulting in the assembling of PNTs in the cores of PAAm fibers. The present work serves as a reference in the fabrication of novel thermoresponsive hybrid fibers involving functional nanospheres via electrospun packing. The prepared nanofibers with chain-like and thermoresponsive colloid arrays in the cores are expected to have potential application in various fields.

Influence of Particle Size and Loading on Particle Accessibility in Electrospun Poly(ethylene oxide) and ZIF-8 Composite Fibers: Experiments and Theory

Developing electrospun nanofiber/nanoparticle composites (ENNCs) is an emerging strategy for immobilizing functional particles for a variety of applications. The radial location of the particle along the fiber, either at the surface or in the bulk, has implication into the resulting properties. To explore particle location along fibers, ZIF-8 impregnated poly(ethylene oxide) (PEO) nanofibers are formed by electrospinning particle suspensions. Fibers impregnated with two different ZIF-8 particle sizes (200 nm and 12.5 μm) were electrospun and shown by nitrogen porosimetry to be nearly completely wrapped by PEO in each case at loadings near 10 wt %. This was favorably compared to developed theory of polymeric membrane encapsulated particles and extended to other electrospun fiber/particle composites through a brief literature review. ENNCs with varying loadings of nanosized ZIF-8 particles were then fabricated and tested with nitrogen porosimetry to find that the particles became available for adsorption at the surface of the fibers starting from 25 wt % (28 vol %) loading. This suggests that the particles are kinetically trapped at this loading level since, if allowed to exhibit random close-packing, the ZIF-8 would be expected to fully imbedded inside the fibers up to 56 vol % loading.

Flexible SiC/Si3N4 Composite Nanofibers with in Situ Embedded Graphite for Highly Efficient Electromagnetic Wave Absorption

SiC/Si₃N₄ composite nanofibers with in situ embedded graphite, which show highly efficient electromagnetic (EM) wave absorption performance in gigahertz frequency, were prepared by electrospinning with subsequent polymer pyrolysis and annealing. By means of incorporating graphite and Si₃N₄ into SiC, the EM wave absorption properties of the nanofibers were improved. The relationship among processing, fiber microstructure, and their superior EM wave absorption performance was systematically investigated. The EM wave absorption capability and effective absorption bandwidth (EAB) of nanofibers can be simply controlled by adjusting annealing atmosphere and temperature. The nanofibers after annealing at 1300 °C in Ar present a minimum reflection loss (RL) of -57.8 dB at 14.6 with 5.5 GHz EAB. The nanofibers annealed in N₂ at 1300 °C exhibit a minimum RL value of -32.3 dB at a thickness of 2.5 mm, and the EAB reaches 6.4 GHz over the range of 11.3-17.7 GHz. The highly efficient EM wave absorption performance of nanofibers are closely related to dielectric loss, which originated from interfacial polarization and dipole polarization. The excellent absorbing performance together with wider EAB endows the composite nanofibers potential to be used as reinforcements in polymers and ceramics (SiC, Si₃N₄, SiO₂, Al₂O₃, etc.) to improve their EM wave absorption performance.

Electrostatic Assembly of Platinum Nanoparticles along Electrospun Polymeric Nanofibers for High Performance Electrochemical Sensors

A novel polyacrylonitrile (PAN) nanofibrous membrane conjugated with platinum nanoparticles (PtNPs) was fabricated by electrospinning and electrostatic assembly techniques. In this procedure, PAN was electrospun with 3-aminopropyltriethoxysilane (APS) together as precursor materials. First, amine groups were introduced onto PAN nanofibers, and then the as-prepared negative-charged platinum nanoparticles (PtNPs) were conjugated onto the surface of the amino-modified PAN nanofibers uniformly by the electrostatic interaction-mediated assembly. The fabricated PAN-PtNPs hybrid nanofibrous membrane was further utilized to modify the glassy carbon electrodes and was used for the fabrication of a non-enzymatic amperometric sensor to detect hydrogen peroxide (H₂O₂). The electrochemical results indicated that, due to the uniform dispersion of PtNPs and the electrostatic interaction between amine groups and PtNPs, the fabricated PAN-PtNPs nanofibrous membrane-based electrochemical sensor showed excellent electrocatalytic activity toward H₂O₂, and the chronoamperometry measurements illustrated that the fabricated sensor had a high sensitivity for detecting H₂O₂. It is anticipated that the strategies used in this work will not only guide the design and fabrication of functional polymeric nanofiber-based biomaterials and nanodevices, but also extend their potential applications in energy storage, cytology, and tissue engineering.

Recent Advances in Electrospun Nanofiber Interfaces for Biosensing Devices

Electrospinning has emerged as a very powerful method combining efficiency, versatility and low cost to elaborate scalable ordered and complex nanofibrous assemblies from a rich variety of polymers. Electrospun nanofibers have demonstrated high potential for a wide spectrum of applications, including drug delivery, tissue engineering, energy conversion and storage, or physical and chemical sensors. The number of works related to biosensing devices integrating electrospun nanofibers has also increased substantially over the last decade. This review provides an overview of the current research activities and new trends in the field. Retaining the bioreceptor functionality is one of the main challenges associated with the production of nanofiber-based biosensing interfaces. The bioreceptors can be immobilized using various strategies, depending on the physical and chemical characteristics of both bioreceptors and nanofiber scaffolds, and on their interfacial interactions. The production of nanobiocomposites constituted by carbon, metal oxide or polymer electrospun nanofibers integrating bioreceptors and conductive nanomaterials (e.g., carbon nanotubes, metal nanoparticles) has been one of the major trends in the last few years. The use of electrospun nanofibers in ELISA-type bioassays, lab-on-a-chip and paper-based point-of-care devices is also highly promising. After a short and general description of electrospinning process, the different strategies to produce electrospun nanofiber biosensing interfaces are discussed.

Multifunctional electrospun polymeric nanofibrous mats for catalytic reduction, photocatalysis and sensing

Fabrication and decoration of flexible Nylon 6,6 polymeric nanofibrous mats for production of multifunctional electrospun material was accomplished via visible light-emitting surface-protected silicon quantum dots (Si QD), ZnO nanoparticles (ZnO NP) and Pd nanocubes (Pd NC). UV-range light was utilized for Si QD production and, after hydrolysis/condensation together with nucleation and growth reactions, amine-modified, fluorescent Si QD were obtained. Additionally, available molecular groups on the Si QD coated onto the polymeric nanofibrous mats provided further attachment of metal oxide and metal NP for various catalytic purposes. Analytical investigations showed that visible-light emission could be maintained on the Nylon 6,6 mats for trinitrotoluene (TNT) sensing. Also, due to consecutive NP decoration, multifunctional, polymeric, flexible nanofibrous mats were obtained. Experiments revealed that fabricated multifunctional mats could reduce molecules such as paranitrophenol effectively or decompose waste dyes such as methylene blue via photocatalytic experiments, and sense the pollutant TNT in aqueous solutions as an all-in-one concept.

Electrospun Nanofibrous Silk Fibroin Membranes Containing Gelatin Nanospheres for Controlled Delivery of Biomolecules

Development of novel and effective drug delivery systems for controlled release of bioactive molecules is of critical importance in the field of regenerative medicine. Here, oppositely charged gelatin nanospheres are incorporated into silk fibroin nanofibers through a colloidal electrospinning technique. A novel fibrous nano-in-nano drug delivery system is fabricated without the use of any organic solvent. The distribution of fluorescently labeled gelatin A and B nanospheres inside the nanofibers can be fine-tuned by simple adjustment of the weight ratio between the nanospheres and the relative feeding rate of core and shell solutions containing nanospheres by using single and coaxial nozzle electrospinning, respectively. Incorporation of vancomycin-loaded gelatin B nanospheres into the silk fibroin nanofibrous membranes results in a more sustained release of vancomycin, compared to the gelatin nanospheres free membranes. In addition, these membranes exhibit excellent and prolonged antibacterial effects against Staphylococcus aureus. Moreover, these membranes support the attachment, spreading, and proliferation of periodontal ligament cells. These results suggest that the beneficial properties of gelatin nanospheres can be exploited to improve the biological functionality of electrospun nanofibrous silk fibroin membranes.

Electrosprayed Janus Particles for Combined Photo-Chemotherapy

This work is a proof of concept study establishing the potential of electrosprayed Janus particles for combined photodynamic therapy-chemotherapy. Sub-micron-sized particles of polyvinylpyrrolidone containing either an anti-cancer drug (carmofur) or a photosensitiser (rose bengal; RB), and Janus particles containing both in separate compartments were prepared. The functional components were present in the amorphous form in all the particles, and infrared spectroscopy indicated that intermolecular interactions formed between the different species. In vitro drug release studies showed that both carmofur and RB were released at approximately the same rate, with dissolution complete after around 250 min. Cytotoxicity studies were undertaken on model human dermal fibroblasts (HDF) and lung cancer (A549) cells, and the influence of light on cell death explored. Formulations containing carmofur as the sole active ingredient were highly toxic to both cell lines, with or without a light treatment. The RB formulations were non-toxic to HDF when no light was applied, and with photo-treatment caused large amounts of cell death for both A549 and HDF cells. The Janus formulation containing both RB and carmofur was non-toxic to HDF without light, and only slightly toxic with the photo-treatment. In contrast, it was hugely toxic to A549 cells when light was applied. The Janus particles are thus highly selective for cancer cells, and it is hence proposed that such electrosprayed particles containing both a chemotherapeutic agent and photosensitiser have great potential in combined chemotherapy/photodynamic therapy.