Electrospun Nanofibers for Sensing and Biosensing Applications-A Review

Gum Arabic: A Commodity with Versatile Formulations and Applications

Gum Arabic (GA), or acacia gum, refers to the dried exudate produced by certain Acacia trees. GA is composed mainly of a mixture of polysaccharides and glycoproteins, with proportions that can slightly differ from one species to another. It is commonly utilized in the food and pharmaceutical industries as a stabilizer or an emulsifier owing to its biocompatibility, hydrophilicity, and antibacterial properties. In addition, GA can be manipulated as it possesses many functional groups that can be used in grafting, cross-linking, or chemical modifications to add a new feature to the developed material. In this review, we highlight recent GA-based formulations, including nanoparticles, hydrogels, nanofibers, membranes, or scaffolds, and their possible applications in tissue regeneration, cancer therapy, wound healing, biosensing, bioimaging, food packaging, and antimicrobial and antifouling membranes.

Recent advances in colorimetric and photoluminescent fibrillar devices, photonic crystals and carbon dot-based sensors for mercury (II) ion detection

The escalating environmental contamination with mercury has become a pressing issue, significantly impacting human beings and nature. For instance, small-scale gold mining has led to severe contamination in the Brazilian Yanomami village, highlighting the urgent need for action. The development of fibrillar-based sensors for mercury (II) ions represents an important issue to be considered in the point-of-care and simple detection of contaminants in water. Herein, this review discussed different colorimetric/photoluminescent-based prototypes for Hg2+ ions sensors and corresponding strategies to improve selectivity and sensitivity associated with the regeneration and reuse of the devices. Given these aspects, the electrospinning technique is promising for developing advanced mercury (II) ion sensors.

Surface-functionalized PAN fiber membranes for the sensitive detection of airborne specific markers

PAN fibers are characterized by having a large surface-to-volume ratio and small pores, which are beneficial for applications in filtration and specific molecular detection systems. Naturally, larger items are filtered, and a lower ratio between specific and nonspecific binding is expected since small pores do not allow larger elements to penetrate through membranes; thus, nonspecific binding is enhanced. We prepared and tested fiber membranes (diameter cca 700 nm) functionalized with a specific antibody to prove that even microscopic systems such as bacteria could be specifically identified. In addition, we established a methodology that enabled the effective binding of bacteria in not only an aqueous environment but also air. Our data clearly prove that even large systems such as bacteria could be specifically identified by fiber membranes surface-functionalized with a specific antibody. This research opens the door to the construction of biosensors for the fast, inexpensive, and sensitive identification of airborne bacterial contaminants and other airborne pollutants.

Electrospun Nanofiber-Based Biosensors for Foodborne Bacteria Detection

Food contamination has emerged as a significant global health concern, posing substantial challenges to the food industry. Bacteria are the primary cause of foodborne diseases. Consequently, it is crucial to develop accurate and efficient sensing platforms to detect foodborne bacteria in food products. Among various detection methods, biosensors have emerged as a promising solution due to their portability, affordability, simplicity, selectivity, sensitivity, and rapidity. Electrospun nanofibers have gained increasing popularity in enhancing biosensor performance. These nanofibers possess a distinctive three-dimensional structure, providing a large surface area and ease of preparation. This review provides an overview of the electrospinning technique, nanofibers and nanofiber-based biosensors. It also explores their mechanisms and applications in the detection of foodborne bacteria such as Salmonella, Listeria monocytogenes (L. monocytogenes), Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Pseudomonas putida (P. putida).

Biosensing of arsenic by whole-cell bacterial bioreporter immobilized on polycaprolactone (PCL) electrospun fiber

In recent years, heavy metals derived from several anthropogenic sources have both direct and indirect detrimental effects on the health of the environment and living organisms. Whole-cell bioreporters (WCBs) that can be used to monitor the levels of heavy metals in drinking and natural spring waters are important. In this study, whole-cell arsenic bacterial bioreporters were immobilized using polycaprolactone (PCL) electrospun fibers as the support material. The aim is to determine the properties of this immobilized bioreporter system by evaluating its performance in arsenic detection. Within the scope of the study, different growth media and fiber immobilization times were tested to determine the parameters affecting the fluorescent signals emitted by the immobilized bioreporter system in the presence of two dominant forms of arsenic, namely arsenite (As(III)) and arsenate (As(V)). In addition, the sensitivity, selectivity, response time, and shelf-life of the developed bioreporter system were evaluated. As far as the literature is concerned, this is the first study to investigate the potential of using PCL-electrospun fiber-immobilized fluorescent bacterial bioreporter for arsenic detection. This study will open new avenues in environmental arsenic monitoring.

Nanomaterial-based sensors for microbe detection: a review

Airborne microorganisms pose a significant health threat, causing various illnesses. Traditional detection methods are often slow and complex. This review highlights the potential of nanomaterial-based biosensors, particularly colorimetric sensors, for rapid and on-site detection of airborne microbes. Colorimetric sensors offer real-time visual detection without complex instrumentation. We explore the integration of these sensors with Lab-on-a-Chip technology using PDMS microfluidics. This review also proposes a novel PDMS-based colorimetric biosensor for real-time detection of airborne microbes. The sensor utilizes a color change phenomenon easily observable with the naked eye, simplifying analysis and potentially enabling point-of-care applications.

Advances in graphene-based 2D materials for tendon, nerve, bone/cartilage regeneration and biomedicine

Two-dimensional (2D) materials, especially graphene-based materials, have important implications for tissue regeneration and biomedicine due to their large surface area, transport properties, ease of functionalization, biocompatibility, and adsorption capacity. Despite remarkable progress in the field of tissue regeneration and biomedicine, there are still problems such as unclear long-term stability, lack of in vivo experimental data, and detection accuracy. This paper reviews recent applications of graphene-based materials in tissue regeneration and biomedicine and discusses current issues and prospects for the development of graphene-based materials with respect to promoting the regeneration of tendons, neuronal cells, bone, chondrocytes, blood vessels, and skin, as well as applications in sensing, detection, anti-microbial activity, and targeted drug delivery.

A Color Indicator Based on 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium Bromide (MTT) and a Biodegradable Poly(ester amide) for Detecting Bacterial Contamination

Bacterial contamination is a hazard in many industries, including food, pharmaceuticals, and healthcare. The availability of a rapid and simple method for detecting this type of contamination in sterile areas enables immediate intervention to avoid or reduce detrimental effects. Among these methods, colorimetric indicators are becoming increasingly popular due to their affordability, ease of use, and quick visual interpretation of the signal. In this article, a bacterial contamination indicator system was designed by incorporating MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) into an electrospun PADAS matrix, which is a biodegradable poly(ester amide) synthesized from L-alanine, 1,12-dodecanediol, and sebacic acid. Uniaxial stress testing, thermogravimetric analysis and scanning electron microscopy were used to examine the mechanical properties, thermal stability, and morphology of the mats, respectively. The capacity for bacterial detection was not only analyzed with agar and broth assays but also by replicating important environmental conditions. Among the MTT concentrations tested in this study (0.2%, 2%, and 5%), it was found that only with a 2% MTT content the designed system produced a color response visible to the naked eye with optimal intensity, a sensitivity limit of 104 CFU/mL, and 86% cell viability, which showed the great potential for its use to detect bacterial contamination. In summary, by means of the process described in this work, it was possible to obtain a simple, low-cost and fast-response bacterial contamination indicator that can be used in mask filters, air filters, or protective clothing.

An Updated Review on Functionalized Graphene as Sensitive Materials in Sensing of Pesticides

Numerous chemical pesticides were employed for a long time to manage pests, but their uncontrolled application harmed the health and the environment. Accurately quantifying pesticide residues is essential for risk evaluation and regulatory purposes. Numerous analytical methods have been developed and utilized to achieve sensitive and specific detection of pesticides in intricate sampl es like water, soil, food, and air. Electrochemical sensors based on amperometry, potentiometry, or impedance spectroscopy offer portable, rapid, and sensitive detection suitable for on-site analysis. This study examines the potential of electrochemical sensors for the accurate evaluation of various effects of pesticides. Emphasizing the use of Graphene (GR), Graphene Oxide (GO), Reduced Graphene Oxide (rGO), and Graphdiyne composites, the study highlights their enhanced performance in pesticide sensing by stating the account of many actual sensors that have been made for specific pesticides. Computational studies provide valuable insights into the adsorption kinetics, binding energies, and electronic properties of pesticide-graphene complexes, guiding the design and optimization of graphene-based sensors with improved performance. Furthermore, the discussion extends to the emerging field of biopesticides. While the GR/GO/rGO based sensors hold immense future prospects, and their existing limitations have also been discussed, which need to be solved with future research.

Fibrous Structures: An Overview of Their Responsiveness to External Stimuli towards Intended Application

In recent decades, the interest in responsive fibrous structures has surged, propelling them into diverse applications: from wearable textiles that adapt to their surroundings, to filtration membranes dynamically altering selectivity, these structures showcase remarkable versatility. Various stimuli, including temperature, light, pH, electricity, and chemical compounds, can serve as triggers to unleash physical or chemical changes in response. Processing methodologies such as weaving or knitting using responsive yarns, electrospinning, as well as coating procedures, enable the integration of responsive materials into fibrous structures. They can respond to these stimuli, and comprise shape memory materials, temperature-responsive polymers, chromic materials, phase change materials, photothermal materials, among others. The resulting effects can manifest in a variety of ways, from pore adjustments and altered permeability to shape changing, color changing, and thermal regulation. This review aims to explore the realm of fibrous structures, delving into their responsiveness to external stimuli, with a focus on temperature, light, and pH.

New dimensions of electrospun nanofiber material designs for biotechnological uses

Electrospinning technology has garnered wide attention over the past few decades in various biomedical applications including drug delivery, cell therapy, and tissue engineering. This technology can create nanofibers with tunable fiber diameters and functionalities. However, the 2D membrane nature of the nanofibers, as well as the rigidity and low porosity of electrospun fibers, lower their efficacy in tissue repair and regeneration. Recently, new avenues have been explored to resolve the challenges associated with 2D electrospun nanofiber membranes. This review discusses recent trends in creating different electrospun nanofiber microstructures from 2D nanofiber membranes by using various post-processing methods, as well as their biotechnological applications.

Unveiling the Inner Structure of Micrometric Hollow Polymeric Fibers Using Synchrotron X-Ray Nanotomography

In this study, a novel application of synchrotron X-ray nanotomography based on high-resolution full-field transmission X-ray microscopy for characterizing the structure and morphology of micrometric hollow polymeric fibers is presented. By employing postimage analysis using an open-source software such as Tomviz and ImageJ, various key parameters in fiber morphology, including diameter, wall thickness, wall thickness distribution, pore size, porosity, and surface roughness, were assessed. Electrospun polycaprolactone fibers with micrometric diameters and submicrometric features with induced porosity via gas dissolution foaming were used to this aim. The acquired synchrotron X-ray nanotomography data were analyzed using two approaches: 3D tomographic reconstruction and 2D radiographic projection-based analysis. The results of the combination of both approaches demonstrate unique capabilities of this technique, not achievable by other available techniques, allowing for a full characterization of the internal and external morphology and structure of the fibers as well as to obtain valuable qualitative insights into the overall fiber structure.

A systematic review on green and natural polymeric nanofibers for biomedical applications

Electrospinning is the simplest technique to produce ultrathin nanofibers, which enables the use of nanotechnology in various applications. Nanofibrous materials produced through electrospinning have garnered significant attention in biomedical applications due to their unique properties and versatile potential. In recent years, there has been a growing emphasis on incorporating sustainability principles into material design and production. However, electrospun nanofibers, owing to their reliance on solvents associated with significant drawbacks like toxicity, flammability, and disposal challenges, frequently fall short of meeting environmentally friendly standards. Due to the limited solvent choices and heightened concerns for safety and hygiene in modern living, it becomes imperative to carefully assess the implications of employing electrospun nanofibers in diverse applications and consumer products. This systematic review aims to comprehensively assess the current state of research and development in the field of "green and natural" electrospun polymer nanofibers as well as more fascinating and eco-friendly commercial techniques, solvent preferences, and other green routes that respect social and legal restrictions tailored for biomedical applications. We explore the utilization of biocompatible and biodegradable polymers sourced from renewable feedstocks, eco-friendly processing techniques, and the evaluation of environmental impacts. Our review highlights the potential of green and natural electrospun nanofibers to address sustainability concerns while meeting the demanding requirements of various biomedical applications, including tissue engineering, drug delivery, wound healing, and diagnostic platforms. We analyze the advantages, challenges, and future prospects of these materials, offering insights into the evolving landscape of environmentally responsible nanofiber technology in the biomedical field.

Artificial enzyme innovations in electrochemical devices: advancing wearable and portable sensing technologies

With the rapid evolution of sensing technologies, the integration of nanoscale catalysts, particularly those mimicking enzymatic functions, into electrochemical devices has surfaced as a pivotal advancement. These catalysts, dubbed artificial enzymes, embody a blend of heightened sensitivity, selectivity, and durability, laying the groundwork for innovative applications in real-time health monitoring and environmental detection. This minireview penetrates into the fundamental principles of electrochemical sensing, elucidating the unique attributes that establish artificial enzymes as foundational elements in this field. We spotlight a range of innovations where these catalysts have been proficiently incorporated into wearable and portable platforms. Navigating the pathway of amalgamating these nanoscale wonders into consumer-appealing devices presents a multitude of challenges; nevertheless, the progress made thus far signals a promising trajectory. As the intersection of materials science, biochemistry, and electronics progressively intensifies, a flourishing future seems imminent for artificial enzyme-infused electrochemical devices, with the potential to redefine the landscapes of wearable health diagnostics and portable sensing solutions.

Recent Progress in Fabrication of Electrospun Nanofiber Membranes for Developing Physiological In Vitro Organ/Tissue Models

Nanofiber membranes (NFMs), which have an extracellular matrix-mimicking structure and unique physical properties, have garnered great attention as biomimetic materials for developing physiologically relevant in vitro organ/tissue models. Recent progress in NFM fabrication techniques immensely contributes to the development of NFM-based cell culture platforms for constructing physiological organ/tissue models. However, despite the significance of the NFM fabrication technique, an in-depth discussion of the fabrication technique and its future aspect is insufficient. This review provides an overview of the current state-of-the-art of NFM fabrication techniques from electrospinning techniques to postprocessing techniques for the fabrication of various types of NFM-based cell culture platforms. Moreover, the advantages of the NFM-based culture platforms in the construction of organ/tissue models are discussed especially for tissue barrier models, spheroids/organoids, and biomimetic organ/tissue constructs. Finally, the review concludes with perspectives on challenges and future directions for fabrication and utilization of NFMs.

Non-enzymatic glucose detection with screen-printed chemiresistive sensor using green synthesised silver nanoparticle and multi-walled carbon nanotubes-zinc oxide nanofibers

Non-enzymatic screen-printed chemiresistive interdigitated electrodes (SPCIE) were designed and fabricated using a low-cost screen-printing method for detection of the glucose. The interdigitated electrodes (IDE) pattern was printed using conductive graphene ink on the glossy surface of the photo paper. The proposed glossy photo paper-based SPCIE are functionalized with multi-walled carbon nanotubes-zinc oxide (MWCNTs-ZnO) nanofibers to create the chemiresistive matrix. Further, to bind these nanofibers with the graphene electrode surface, we have used the green synthesized silver nanoparticles (AgNPs) with banana flower stem fluid (BFSF) as a binder solution. AgNPs with BFSF form the conductive porous natural binder layer (CPNBL). It does not allow to increase the resistivity of the deposited material on graphene electrodes and also keeps the nanofibers intact with paper-based SPCIE. The synthesized material of MWCNT-ZnO nanofibers and green synthesized AgNPs with BFSF as a binder were characterized by Ultraviolet-visible spectroscopy (UV-vis), scanning electron microscope (SEM), x-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). The amperometric measurements were performed on the proposed SPCIE sensor to detect the glucose sample directly. The innovative paper-based SPCIE glucose sensor exhibits a linear corelation between current measurements and glucose concentration in the range between 45.22μm and 20 mm, with a regression coefficient (R2) of 0.9902 and a lower limit of detection (LoD) of 45.22μm (n= 5). The sensitivity of the developed SPCIE sensor was 2178.57μAmM-1cm-2, and the sensor's response time determined was approximately equal to 18 s. The proposed sensor was also tested for real blood serum sample, and relative standard deviation (RSD) was found equal to 2.95%.

Non-Invasive Glucose Sensing Technologies and Products: A Comprehensive Review for Researchers and Clinicians

Diabetes Mellitus incidence and its negative outcomes have dramatically increased worldwide and are expected to further increase in the future due to a combination of environmental and social factors. Several methods of measuring glucose concentration in various body compartments have been described in the literature over the years. Continuous advances in technology open the road to novel measuring methods and innovative measurement sites. The aim of this comprehensive review is to report all the methods and products for non-invasive glucose measurement described in the literature over the past five years that have been tested on both human subjects/samples and tissue models. A literature review was performed in the MDPI database, with 243 articles reviewed and 124 included in a narrative summary. Different comparisons of techniques focused on the mechanism of action, measurement site, and machine learning application, outlining the main advantages and disadvantages described/expected so far. This review represents a comprehensive guide for clinicians and industrial designers to sum the most recent results in non-invasive glucose sensing techniques' research and production to aid the progress in this promising field.

Electrospun Nanofibers for Biomedical, Sensing, and Energy Harvesting Functions

The process of electrospinning is over a century old, yet novel material and method achievements, and later the addition of nanomaterials in polymeric solutions, have spurred a significant increase in research innovations with several unique applications. Significant improvements have been achieved in the development of electrospun nanofibrous matrices, which include tailoring compositions of polymers with active agents, surface functionalization with nanoparticles, and encapsulation of functional materials within the nanofibers. Recently, sequentially combining fabrication of nanofibers with 3D printing was reported by our group and the synergistic process offers fiber membrane functionalities having the mechanical strength offered by 3D printed scaffolds. Recent developments in electrospun nanofibers are enumerated here with special emphasis on biomedical technologies, chemical and biological sensing, and energy harvesting aspects in the context of e-textile and tactile sensing. Energy harvesting offers significant advantages in many applications, such as biomedical technologies and critical infrastructure protection by using the concept of finite state machines and edge computing. Many other uses of devices using electrospun nanofibers, either as standalone or conjoined with 3D printed materials, are envisaged. The focus of this review is to highlight selected novel applications in biomedical technologies, chem.-bio sensing, and broadly in energy harvesting for use in internet of things (IoT) devices. The article concludes with a brief projection of the future direction of electrospun nanofibers, limitations, and how synergetic combination of the two processes will open pathways for future discoveries.

Electrospun Nanofibrous Mesh Based on PVA, Chitosan, and Usnic Acid for Applications in Wound Healing

Injuries and diseases of the skin require accurate treatment using nontoxic and noninvasive biomaterials, which aim to mimic the natural structures of the body. There is a strong need to develop biodevices capable of accommodating nutrients and bioactive molecules and generating the process of vascularization. Electrospinning is a robust technique, as it can form fibrous structures for tissue engineering and wound dressings. The best way of forming such meshes for wound healing is to choose two polymers that complement each other regarding their properties. On the one hand, PVA is a water-soluble synthetic polymer widely used for the preparation of hydrogels in the field of biomedicine owing to its biocompatibility, water solubility, nontoxicity, and considerable mechanical properties. PVA is easy to subject to electrospinning and can offer strong mechanical stability of the mesh, but it is necessary to improve its biological properties. On the other hand, CS has good biological properties, including biodegradability, nontoxicity, biocompatibility, and antimicrobial properties. Still, it is harder to electrospin and does not possess as good mechanical properties as PVA. As these structures also allow the incorporation of bioactive agents due to their high surface-area-to-volume ratio, the interesting point was to incorporate usnic acid into the structure as it is a natural and suitable alternative agent for burn wounds treatment which avoids an improper or overuse of antibiotics and other invasive biomolecules. Thus, we report the fabrication of an electrospun nanofibrous mesh based on PVA, chitosan, and usnic acid with applications in wound healing. The obtained nanofibers mesh was physicochemically characterized by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). In vitro biological assays were performed to evaluate the antimicrobial properties of the samples using the MIC (minimum inhibitory concentration) assay and evaluating the influence of fabricated meshes on the Staphylococcus aureus biofilm development, as well as their biocompatibility (demonstrated by fluorescence microscopy results, an XTT assay, and a glutathione (GSH) assay).

Nanomaterial interfaces designed with different biorecognition elements for biosensing of key foodborne pathogens

Foodborne diseases caused by pathogen bacteria are a serious problem toward the safety of human life in a worldwide. Conventional methods for pathogen bacteria detection have several handicaps, including trained personnel requirement, low sensitivity, laborious enrichment steps, low selectivity, and long-term experiments. There is a need for precise and rapid identification and detection of foodborne pathogens. Biosensors are a remarkable alternative for the detection of foodborne bacteria compared to conventional methods. In recent years, there are different strategies for the designing of specific and sensitive biosensors. Researchers activated to develop enhanced biosensors with different transducer and recognition elements. Thus, the aim of this study was to provide a topical and detailed review on aptamer, nanofiber, and metal organic framework-based biosensors for the detection of food pathogens. First, the conventional methods, type of biosensors, common transducer, and recognition element were systematically explained. Then, novel signal amplification materials and nanomaterials were introduced. Last, current shortcomings were emphasized, and future alternatives were discussed.

Light-Driven Energy and Charge Transfer Processes between Additives within Electrospun Nanofibres

Electrospinning is a cost-effective and efficient method of producing polymeric nanofibre films. The resulting nanofibres can be produced in a variety of structures, including monoaxial, coaxial (core@shell), and Janus (side-by-side). The resulting fibres can also act as a matrix for various light-harvesting components such as dye molecules, nanoparticles, and quantum dots. The addition of these light-harvesting materials allows for various photo-driven processes to occur within the films. This review discusses the process of electrospinning as well as the effect of spinning parameters on resulting fibres. Building on this, we discuss energy transfer processes that have been explored in nanofibre films, such as Förster resonance energy transfer (FRET), metal-enhanced fluorescence (MEF), and upconversion. A charge transfer process, photoinduced electron transfer (PET), is also discussed. This review highlights various candidate molecules that have been used for photo-responsive processes in electrospun films.

Fabrication, Microstructures and Sensor Applications of Highly Ordered Electrospun Nanofibers: A Review

The review summarizes the fabrication, microstructures, and sensor applications of highly ordered electrospun nanofibers. In the traditional electrospinning process, electrospun nanofibers usually have disordered or random microstructures due to the chaotic oscillation of the electrospinning jet. Different electrospinning methods can be formed by introducing external forces, such as magnetic, electric, or mechanical forces, and ordered nanofibers can be collected. The microstructures of highly ordered nanofibers can be divided into three categories: uniaxially ordered nanofibers, biaxially ordered nanofibers and ordered scaffolds. The three microstructures are each characterized by being ordered in different dimensions. The regulation and control of the ordered microstructures can promote electrospun nanofibers' mechanical and dielectric strength, surface area and chemical properties. Highly ordered electrospun nanofibers have more comprehensive applications than disordered nanofibers do in effect transistors, gas sensors, reinforced composite materials and tissue engineering. This review also intensively summarizes the applications of highly ordered nanofibers in the sensor field, such as pressure sensors, humidity sensors, strain sensors, gas sensors, and biosensors.

Optical Properties of Electrospun Nanofiber Mats

Electrospun nanofiber mats are usually applied in fields where their high specific surface area and small pore sizes are important, such as biotechnology or filtration. Optically, they are mostly white due to scattering from the irregularly distributed, thin nanofibers. Nevertheless, their optical properties can be modified and become highly important for different applications, e.g., in sensing devices or solar cells, and sometimes for investigating their electronic or mechanical properties. This review gives an overview of typical optical properties of electrospun nanofiber mats, such as absorption and transmission, fluorescence and phosphorescence, scattering, polarized emission, dyeing and bathochromic shift as well as the correlation with dielectric constants and the extinction coefficient, showing which effects may occur and can be measured by which instruments or used for different applications.

Electrospun Magnetic Nanofiber Mats for Magnetic Hyperthermia in Cancer Treatment Applications-Technology, Mechanism, and Materials

The number of cancer patients is rapidly increasing worldwide. Among the leading causes of human death, cancer can be regarded as one of the major threats to humans. Although many new cancer treatment procedures such as chemotherapy, radiotherapy, and surgical methods are nowadays being developed and used for testing purposes, results show limited efficiency and high toxicity, even if they have the potential to damage cancer cells in the process. In contrast, magnetic hyperthermia is a field that originated from the use of magnetic nanomaterials, which, due to their magnetic properties and other characteristics, are used in many clinical trials as one of the solutions for cancer treatment. Magnetic nanomaterials can increase the temperature of nanoparticles located in tumor tissue by applying an alternating magnetic field. A very simple, inexpensive, and environmentally friendly method is the fabrication of various types of functional nanostructures by adding magnetic additives to the spinning solution in the electrospinning process, which can overcome the limitations of this challenging treatment process. Here, we review recently developed electrospun magnetic nanofiber mats and magnetic nanomaterials that support magnetic hyperthermia therapy, targeted drug delivery, diagnostic and therapeutic tools, and techniques for cancer treatment.

Carbon Nanotube-Incorporated Nanofibers for Immunosensor Preparation against CD36

The increased serum concentration of CD36 is significantly associated with atherosclerosis, insulin resistance, and diabetes mellitus. Currently, there is no sensor system used for the detection of CD36 in the clinical field. Therefore, there is a need to develop a sensor system for the detection of CD36. The large surface area/volume ratio and controllable surface conformation of electrospun nanofibers (ENs) make them highly attractive for immunosensor applications. In the present study, PS/MWCNT-PAMAM ENs were produced and used as an immobilization matrix of Anti-CD36. Thus, the electrochemical behavior of the developed nanocomposite-based ENs and their usage potential were investigated for immunosensor applications. First, an oxidized multiwall carbon nanotube (MWCNT-OH) was synthesized and modified with a polyamidoamine generation 3 (PAMAM G3) dendrimer. The synthesized MWCNT-PAMAM nanocomposite was mixed with polystyrene (PS) solutions at different ratios to produce bead-free, smooth, and uniform PS/MWCNT-PAMAM ENs. PS/MWCNT-PAMAM ENs were accumulated on a screen-printed carbon electrode (SPCE) using the electrospinning technique. A biofunctional surface on the PS/MWCNT-PAMAM EN-coated SPCE was created using carbodiimide chemistry by covalent immobilization of Anti-CD36. The analytic performance characteristics of the developed PS/MWCNT-PAMAM/Anti-CD36 immunosensor were determined by performing electrochemical measurements in the presence of the CD36 protein. The linear detection range was found to be from 5 to 40 ng/mL, and the limit of detection was calculated as 3.94 ng/mL for CD36. The developed PS/MWCNT-PAMAM/Anti-CD36 immunosensor also displayed high tolerance to interference substances, good repeatability, and high recovery percent (recovery%) for artificial blood serum analysis.

Water-Resistant Photo-Crosslinked PEO/PEGDA Electrospun Nanofibers for Application in Catalysis

Catalysts are used for producing the vast majority of chemical products. Usually, catalytic membranes are inorganic. However, when dealing with reactions conducted at low temperatures, such as in the production of fine chemicals, polymeric catalytic membranes are preferred due to a more competitive cost and easier tunability compared to inorganic ones. In the present work, nanofibrous mats made of poly(ethylene oxide), PEO, and poly(ethylene glycol) diacrylate, PEGDA, blends with the Au/Pd catalyst are proposed as catalytic membranes for water phase and low-temperature reactions. While PEO is a water-soluble polymer, its blending with PEGDA can be exploited to make the overall PEO/PEGDA blend nanofibers water-resistant upon photo-crosslinking. Thus, after the optimization of the blend solution (PEO molecular weight, PEO/PEGDA ratio, photoinitiator amount), electrospinning process, and UV irradiation time, the resulting nanofibrous mat is able to maintain the nanostructure in water. The addition of the Au₆/Pd₁ catalyst (supported on TiO₂) in the PEO/PEGDA blend allows the production of a catalytic nanofibrous membrane. The reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP), taken as a water phase model reaction, demonstrates the potential usage of PEO-based membranes in catalysis.

Electrohydrodynamic Techniques for the Manufacture and/or Immobilization of Vesicles

The development of accurate drug delivery systems is one of the main challenges in the biomedical field. A huge variety of structures, such as vesicles, nanoparticles, and nanofibers, have been proposed as carriers for bioactive agents, aiming for precision in administration and dosage, safety, and bioavailability. This review covers the use of electrohydrodynamic techniques both for the immobilization and for the synthesis of vesicles in a non-conventional way. The state of the art discusses the most recent advances in this field as well as the advantages and limitations of electrospun and electrosprayed amphiphilic structures as precursor templates for the in situ vesicle self-assembly. Finally, the perspectives and challenges of combined strategies for the development of advanced structures for the delivery of bioactive agents are analyzed.

Photocatalytic degradation of dyes by novel electrospun nanofibers: A review

Textile industry is a significant contributor of wastewater, which contains pollutants including dye and other chemical substances. The release of thousands of tons of dye used in textile processing and finishing into natural streams and aquatic bodies present dire harm to the environment. In response to environmental concerns, a number of research have been done using low-cost technology to produce absorbents that can remove dyes from water bodies. Distinct techniques such as adsorption, enzymatic and photocatalytic degradation, etc. have been employed to remove dyes. In the last few decades, photocatalysis, a simple and green strategy, has emerged as the most valuable and recent principle that deals with wastewater treatment, using uniquely fabricated nanomaterials. Among them, rapid and versatile electrospinning methods have been used for the construction of a large surface area, hierarchical and reusable nanofibers for environmental remediation. As a flexible and fast fabrication method, reviewing the use of electrospun photocatalytic nanofibers, influential parameters in electrospinning and their effectiveness in the generation of oxidizing agents are a promising platform for the fabrication of novel nanomaterials in photocatalytic degradation of dyes. This review discusses techniques for dye removal, electrospun nanofibers, their fabrication and application in photocatalysis; mechanism of photocatalytic degradation, and challenges and suggested remedies for electrospun nanofibers in photocatalysis.

Electrospun Polymer Nanofibers: Processing, Properties, and Applications

Electrospun polymer nanofibers (EPNF) constitute one of the most important nanomaterials with diverse applications. An overall review of EPNF is presented here, starting with an introduction to the most attractive features of these materials, which include the high aspect ratio and area to volume ratio as well as excellent processability through various production techniques. A review of these techniques is featured with a focus on electrospinning, which is the most widely used, with a detailed description and different types of the process. Polymers used in electrospinning are also reviewed with the solvent effect highlighted, followed by a discussion of the parameters of the electrospinning process. The mechanical properties of EPNF are discussed in detail with a focus on tests and techniques used for determining them, followed by a section for other properties including electrical, chemical, and optical properties. The final section is dedicated to the most important applications for EPNF, which constitute the driver for the relentless pursuit of their continuous development and improvement. These applications include biomedical application such as tissue engineering, wound healing and dressing, and drug delivery systems. In addition, sensors and biosensors applications, air filtration, defense applications, and energy devices are reviewed. A brief conclusion is presented at the end with the most important findings and directions for future research.

Is Graphene Always Effective in Reinforcing Composites? The Case of Highly Graphene-Modified Thermoplastic Nanofibers and Their Unfortunate Application in CFRP Laminates

Graphene (G) can effectively enhance polymers' and polymer composites' electric, thermal, and mechanical properties. Nanofibrous mats have been demonstrated to significantly increase the interlaminar fracture toughness of composite laminates, hindering delamination and, consequently, making such materials safer and more sustainable thanks to increased service life. In the present paper, poly(ethylene oxide) (PEO), polycaprolactone (PCL), and Nylon 66 nanofibers, plain or reinforced with G, were integrated into epoxy-matrix Carbon Fiber Reinforced Polymers (CFRPs) to evaluate the effect of polymers and polymers + G on the laminate mechanical properties. The main aim of this work is to compare the reinforcing action of the different nanofibers (polyether, polyester, and polyamide) and to disclose the effect of G addition. The polymers were chosen considering their thermal properties and, consequently, their mechanism of action against delamination. PEO and PCL, displaying a low melting temperature, melt, and mix during the curing cycle, act via matrix toughening; in this context, they are also used as tools to deploy G specifically in the interlaminar region when melting and mixing with epoxy resin. The high extent of modification stems from an attempt to deploy it in the interlaminar layer, thus diluting further in the resin. In contrast, Nylon 66 does not melt and maintain the nanostructure, allowing laminate toughening via nanofiber bridging. The flexural properties of the nanomodifed CFRPs were determined via a three-point bending (3PB) test, while delamination behavior in Mode I and Mode II was carried out using Double Cantilever Beam (DCB) and End-Notched Flexture (ENF) tests, respectively. The lack of a positive contribution of G in this context is an interesting point to raise in the field of nanoreinforced CFRP.

Electrospun Conducting Polymers: Approaches and Applications

Inherently conductive polymers (CPs) can generally be switched between two or more stable oxidation states, giving rise to changes in properties including conductivity, color, and volume. The ability to prepare CP nanofibers could lead to applications including water purification, sensors, separations, nerve regeneration, wound healing, wearable electronic devices, and flexible energy storage. Electrospinning is a relatively inexpensive, simple process that is used to produce polymer nanofibers from solution. The nanofibers have many desirable qualities including high surface area per unit mass, high porosity, and low weight. Unfortunately, the low molecular weight and rigid rod nature of most CPs cannot yield enough chain entanglement for electrospinning, instead yielding polymer nanoparticles via an electrospraying process. Common workarounds include co-extruding with an insulating carrier polymer, coaxial electrospinning, and coating insulating electrospun polymer nanofibers with CPs. This review explores the benefits and drawbacks of these methods, as well as the use of these materials in sensing, biomedical, electronic, separation, purification, and energy conversion and storage applications.

Nanofiber Based on Electrically Conductive Materials for Biosensor Applications

Biosensors are analytical tools that enable the transmission of different signals produced from the target analyte to a transducer for the production of real-time clinical diagnostic devices by obtaining meaningful results. Recent research demonstrates that the production of structured nanofiber through various methods has come to light as a potential platform for enhancing the functionality of biosensing devices. The general trend is towards the use of nanofibers for electrochemical biosensors. However, optical and mechanical biosensors are being developed by functionalization of nanofibers. Such nanofibers exhibit a high surface area to volume ratio, surface porosity, electroconductivity and variable morphology. In addition, nanosized structures have shown to be effective as membranes for immobilizing bioanalytes, offering physiologically active molecules a favorable microenvironment that improves the efficiency of biosensing. Cost effective, wearable biosensors are crucial for point of care diagnostics. This review aims to examine the electrically conductive materials, potential forming methods, and wide-ranging applications of nanofiber-based biosensing platforms, with an emphasis on transducers incorporating mechanical, electrochemical and optical and bioreceptors involving cancer biomarker, urea, DNA, microorganisms, primarily in the last decade. The appealing properties of nanofibers mats and the attributes of the biorecognition components are also stated and explored. Finally, consideration is given to the difficulties now affecting the design of nanofiber-based biosensing platforms as well as their future potential.

Impact of Surface Area on Sensitivity in Autonomously Reporting Sensing Hydrogel Nanomaterials for the Detection of Bacterial Enzymes

The rapid and selective detection of bacterial contaminations and bacterial infections in a non-laboratory setting using advanced sensing materials holds the promise to enable robust point-of-care tests and rapid diagnostics for applications in the medical field as well as food safety. Among the various possible analytes, bacterial enzymes have been targeted successfully in various sensing formats. In this current work, we focus on the systematic investigation of the role of surface area on the sensitivity in micro- and nanostructured autonomously reporting sensing hydrogel materials for the detection of bacterial enzymes. The colorimetric sensing materials for the detection of β-glucuronidase (ß-GUS) from Escherichia coli (E. coli) were fabricated by template replication of crosslinked pullulan acetoacetate (PUAA) and by electrospinning chitosan/polyethylene oxide nanofibers (CS/PEO NFs), both equipped with the chromogenic substrate 5-bromo-4-chloro-3-indolyl-β-D-glucuronide. The investigation of the dependence of the initial reaction rates on surface area unveiled a linear relationship of rate and thereby time to observe a signal for a given concentration of bacterial enzyme. This knowledge was exploited in nanoscale sensing materials made of CS/PEO NFs with diameters of 295 ± 100 nm. Compared to bulk hydrogel slabs, the rate of hydrolysis was significantly enhanced in NFs when exposed to bacteria suspension cultures and thus ensuring a rapid detection of living E. coli that produces the enzyme β-GUS. The findings afford generalized design principles for the improvement of known and novel sensing materials towards rapid detection of bacteria by nanostructuring in medical and food related settings.

Nanoparticles-in-nanofibers composites: Emphasis on some recent biomedical applications

Nanoparticles-in-nanofibers composites comprise an attractive approach for controlling release and delivery of many active molecules for versatile biomedical applications. Incorporation of drug-loaded nanoparticles within these composites can afford the encapsulation of one or more drug with sequential drug release, which can be tuned according to the assigned function. Moreover, existence of nanoparticles within the nanofibrous matrix was found to favor the morphological and mechanical properties of the developed composites. In this review, the latest biomedical advances for nanoparticles-in-nanofibers composites will be highlighted including; tissue regeneration, antimicrobial applications, wound healing, cancer management, cardiovascular disorders, ophthalmic applications, vaginal drug delivery, biosensors and biomedical filters. These composites incorporating multiple types of nanoparticles could be very promising drug delivery platforms.

Bio-nano-composites containing at least two components, chitosan and zein, for food packaging applications: A review of the nano-composites in comparison with the conventional counterparts

Both chitosan and zein are safe industrial biopolymers for the 21St century, respecting environmentally concerns. This review mainly is focused on preparations, properties and applications of a promising food packaging material, chitosan-zein nano-composite (NC). The properties and applications of the NCs were compared with their conventional counterparts. The structure of chitosan- zein composites was proposed. A procedure for preparations of conventional and nano zein-chitosan composites was proposed. The sizes of composites depend on molecular weight of chitosan and zein, the ratio of chitosan/zein, and pH of chitosan-zein solutions. The NCs had superior mechanical, antimicrobial, antioxidant, and barrier properties compared with the conventional ones. The properties of the composites were further improved by introduction of bioactive compounds, fillers or plasticizers. The composites have potential to employ as coatings/packaging materials to protect mushroom, meats, and fresh fruits and vegetables.

A review on Biopolymer-derived Electrospun Nanofibers for Biomedical and Antiviral Applications

Unique aspects of polymer-derived nanofibers provide significant potential in the area of biomedical and health care applications. Much research has demonstrated several plausible nanofibers to overcome the modern-day challenges in...

Optical sensors based on electrospun membranes – principles, applications, and prospects for chemistry and biology

Electrospun membranes are promising substrates for receptor layer immobilization in optical sensors. Either colorimetric, luminescence, or Raman scattering signal can be used to detect the analyte.

A Review on Electrospun Nanofibers Based Advanced Applications: From Health Care to Energy Devices

Electrospun nanofibers have been exploited in multidisciplinary fields with numerous applications for decades. Owing to their interconnected ultrafine fibrous structure, high surface-to-volume ratio, tortuosity, permeability, and miniaturization ability along with the benefits of their lightweight, porous nanofibrous structure, they have been extensively utilized in various research fields for decades. Electrospun nanofiber technologies have paved unprecedented advancements with new innovations and discoveries in several fields of application including energy devices and biomedical and environmental appliances. This review article focused on providing a comprehensive overview related to the recent advancements in health care and energy devices while emphasizing on the importance and uniqueness of utilizing nanofibers. A brief description regarding the effect of electrospinning techniques, setup modifications, and parameters optimization on the nanofiber morphology was also provided. The article is concluded with a short discussion on current research challenges and future perspectives.

Perspective on Nanofiber Electrochemical Sensors: Design of Relative Selectivity Experiments

The use of nanofibers creates the ability for non-enzymatic sensing in various applications and greatly improves the sensitivity, speed, and accuracy of electrochemical sensors for a wide variety of analytes. The high surface area to volume ratio of the fibers as well as their high porosity, even when compared to other common nanostructures, allows for enhanced electrocatalytic, adsorptive, and analyte-specific recognition mechanisms. Nanofibers have the potential to rival and replace materials used in electrochemical sensing. As more types of nanofibers are developed and tested for new applications, more consistent and refined selectivity experiments are needed. We applied this idea in a review of interferant control experiments and real sample analyses. The goal of this review is to provide guidelines for acceptable nanofiber sensor selectivity experiments with considerations for electrocatalytic, adsorptive, and analyte-specific recognition mechanisms. The intended presented review and guidelines will be of particular use to junior researchers designing their first control experiments, but could be used as a reference for anyone designing selectivity experiments for non-enzymatic sensors including nanofibers. We indicate the importance of testing both interferants in complex media and mechanistic interferants in the selectivity analysis of newly developed nanofiber sensor surfaces.

Antimicrobial Properties of Palladium and Platinum Nanoparticles: A New Tool for Combating Food-Borne Pathogens

Although some metallic nanoparticles (NPs) are commonly used in the food processing plants as nanomaterials for food packaging, or as coatings on the food handling equipment, little is known about antimicrobial properties of palladium (PdNPs) and platinum (PtNPs) nanoparticles and their potential use in the food industry. In this study, common food-borne pathogens Salmonella enterica Infantis, Escherichia coli, Listeria monocytogenes and Staphylococcus aureus were tested. Both NPs reduced viable cells with the log₁₀ CFU reduction of 0.3–2.4 (PdNPs) and 0.8–2.0 (PtNPs), average inhibitory rates of 55.2–99% for PdNPs and of 83.8–99% for PtNPs. However, both NPs seemed to be less effective for biofilm formation and its reduction. The most effective concentrations were evaluated to be 22.25–44.5 mg/L for PdNPs and 50.5–101 mg/L for PtNPs. Furthermore, the interactions of tested NPs with bacterial cell were visualized by transmission electron microscopy (TEM). TEM visualization confirmed that NPs entered bacteria and caused direct damage of the cell walls, which resulted in bacterial disruption. The in vitro cytotoxicity of individual NPs was determined in primary human renal tubular epithelial cells (HRTECs), human keratinocytes (HaCat), human dermal fibroblasts (HDFs), human epithelial kidney cells (HEK 293), and primary human coronary artery endothelial cells (HCAECs). Due to their antimicrobial properties on bacterial cells and no acute cytotoxicity, both types of NPs could potentially fight food-borne pathogens.