High Efficiency Fabrication of Chitosan Composite Nanofibers with Uniform Morphology via Centrifugal Spinning

Optimization of the Centrifugal Spinning Parameters to Prepare Poly(butylene succinate) Nanofibers Mats for Aerosol Filter Applications

Air pollution is becoming a serious issue because it negatively impacts the quality of life. One of the first most useful self-defense approaches against air pollution are face masks. Typically made of non-renewable petroleum-based polymers, these masks are harmful to the environment, and they are mostly disposable. Poly(butylene succinate) (PBS) is regarded as one of the most promising materials because of its exceptional processability and regulated biodegradability in a range of applications. In this regard, nanofiber-based face masks are becoming more and more popular because of their small pores, light weight, and excellent filtration capabilities. Centrifugal spinning (CS) provides an alternative method for producing nanofibers from various materials at high speeds and low costs. This current study aimed to investigate the effect of processing parameters on the resultant PBS fiber morphology. Following that, the usability of PBS nonwoven as a filter media was investigated. The effects of solution concentration, rotating speed, and needle size have been examined using a three-factorial Box-Behnken experimental design. The results revealed that PBS concentration had a substantial influence on fiber diameter, with a minimum fiber diameter of 172 nm attained under optimum production conditions compared to the anticipated values of 166 nm. It has been demonstrated that the desired function and the Box-Behnken design are useful instruments for predicting the process parameters involved in the production of PBS nanofibers. PBS filters can achieve an excellent efficiency of more than 98% with a pressure drop of 238 Pa at a flow rate of 85 L/min. The disposable PBS filter media was able to return to nature after use via hydrolysis processes. The speed and cost-effectiveness of the CS process, as well as the environmentally benign characteristics of the PBS polymer, may all contribute considerably to the development of new-age filters.

Alumina Ceramic Nanofibers: An Overview of the Spinning Gel Preparation, Manufacturing Process, and Application

As an important inorganic material, alumina ceramic nanofibers have attracted more and more attention because of their excellent thermal stability, high melting point, low thermal conductivity, and good chemical stability. In this paper, the preparation conditions for alumina spinning gel, such as the experimental raw materials, spin finish aid, aging time, and so on, are briefly introduced. Then, various methods for preparing the alumina ceramic nanofibers are described, such as electrospinning, solution blow spinning, centrifugal spinning, and some other preparation processes. In addition, the application of alumina ceramic nanofibers in thermal insulation, high-temperature filtration, catalysis, energy storage, water restoration, sound absorption, bioengineering, and other fields are described. The wide application prospect of alumina ceramic nanofibers highlights its potential as an advanced functional material with various applications. This paper aims to provide readers with valuable insights into the design of alumina ceramic nanofibers and to explore their potential applications, contributing to the advancement of various technologies in the fields of energy, environment, and materials science.

Large-Scale and Highly Efficient Production of Ultrafine PVA Fibers by Electro-Centrifugal Spinning for NH3 Adsorption

Ultrafine Polyvinyl alcohol (PVA) fibers have an outstanding potential in various applications, especially in absorbing fields. In this manuscript, an electrostatic-field-assisted centrifugal spinning system was designed to improve the production efficiency of ultrafine PVA fibers from PVA aqueous solution for NH₃ adsorption. It was established that the fiber production efficiency using this self-designed system could be about 1000 times higher over traditional electrospinning system. The produced PVA fibers establish high morphology homogeneity. The impact of processing variables of the constructed spinning system including rotation speed, needle size, liquid feeding rate, and voltage on fiber morphology and diameter was systematically investigated by SEM studies. To acquire homogeneous ultrafine PVA fiber membranes, the orthogonal experiment was also conducted to optimize the spinning process parameters. The impact weight of different studied parameters on the spinning performance was thus provided. The experimental results showed that the morphology of micro/nano-fibers can be well controlled by adjusting the spinning process parameters. Ultrafine PVA fibers with the diameter of 2.55 μm were successfully obtained applying the parameters, including rotation speed (6500 rpm), needle size (0.51 mm), feeding rate (3000 mL h^-1), and voltage (20 kV). Furthermore, the obtained ultrafine PVA fiber mat was demonstrated to be capable of selectively adsorbing NH₃ gas relative to CO₂, thus making it promising for NH₃ storage and other environmental purification applications.

High-Speed Centrifugal Spinning Polymer Slip Mechanism and PEO/PVA Composite Fiber Preparation

Composite nanofibers with excellent physical and chemical properties are widely used in new energy, biomedical, environmental, electronic, and other fields. Their preparation methods have been investigated extensively by many experts. High-speed centrifugal spinning is a novel method used to fabricate composite nanofibers. The slip mechanism of polymer solution flows is an important factor affecting the morphology and quality of composite nanofibers prepared by high-speed centrifugal spinning. As the polymer solution flows, the liquid wall slip occurs inside the nozzle, followed by liquid-liquid interface slip and gas-liquid interface slip. The factors affecting polymer slip were investigated by developing a mathematical model in the nozzle. This suggests that the magnitude of the velocity is an important factor that affects polymer slip and determines fiber quality and morphology. Under the same rotational speed, the smaller the nozzle diameter, the greater the concentration of velocity distribution and the smaller the diameter of the produced composite nanofibers. Finally, PEO/PVA composite nanofibers were prepared using high-speed centrifugal spinning equipment at 900-5000 rpm and nozzle diameters of 0.2 mm, 0.4 mm, 0.6 mm, and 0.8 mm. The morphology and quality of the collected PEO/PVA composite nanofibers were analyzed using scanning electron microscopy (SEM) and TG experiments. Then, the optimal parameters for the preparation of PEO/PVA composite nanofibers by high-speed centrifugal spinning were obtained by combining the external environmental factors in the preparation process. Theoretical evaluation and experimental data were provided for the centrifugal composite spinning slip mechanism and for the preparation of composite nanofibers.

Investigation on Centrifugally Spun Fibrous PCL/3-Methyl Mannoside Mats for Wound Healing Application

Fibrous structures, in general, have splendid advantages in different forms of micro- and nanomembranes in various fields, including tissue engineering, filtration, clothing, energy storage, etc. In the present work, we develop a fibrous mat by blending the bioactive extract of Cassia auriculata (CA) with polycaprolactone (PCL) using the centrifugal spinning (c-spinning) technique for tissue-engineered implantable material and wound dressing applications. The fibrous mats were developed at a centrifugal speed of 3500 rpm. The PCL concentration for centrifugal spinning with CA extract was optimized at 15% w/v of PCL to achieve better fiber formation. Increasing the extract concentration by more than 2% resulted in crimping of fibers with irregular morphology. The development of fibrous mats using a dual solvent combination resulted in fine pores on the fiber structure. Scanning electron microscope (SEM) images showed that the surface morphology of the fibers in the produced fiber mats (PCL and PCL-CA) was highly porous. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that the CA extract contained 3-methyl mannoside as the predominant component. The in vitro cell line studies using NIH3T3 fibroblasts demonstrated that the CA-PCL nanofiber mat was highly biocompatible, supporting cell proliferation. Hence, we conclude that the c-spun, CA-incorporating nanofiber mat can be employed as a tissue-engineered construct for wound healing applications.

Cytotoxicity evaluation of poly(ethylene) oxide nanofibre in MCF-7 breast cancer cell line

Biocompatible polymers have received significant interest from researchers for their potential in diagnostic applications. This type of polymer can perform with an appropriate host response or carrier for a specific purpose. The current study aims to fabricate and characterise poly(ethylene) oxide (PEO) nanofibres with different concentrations for cytotoxicity evaluation in human breast cancer cell lines (MCF-7) and to get an optimal PEO nanofibre concentration (permissible limit) as a suitable polymer matrix or carrier with potential use in diagnostic applications. The fabrication of PEO nanofibres was done using electrospinning and was characterised by structure and morphology, surface roughness, chemical bonding and release profiles. The functional effects of PEO nanofibres were evaluated with MTS assay and colony formation assay in MCF-7 cells. The results showed that viscosity plays a vital role in synthesising a polymer solution in electrospinning for producing beadless nanofibrous mats ranging from 4.7 Pa·s to 77.7 Pa·s. As the PEO concentration increases, the nanofibre diameter and thickness will increase, but the surface roughness will be decreased. The average fibre diameter for 5 wt% PEO, 6 wt% PEO and 7 wt% PEO nanofibres were 129 ± 70 nm, 185 ± 55 nm and 192 ± 53 nm, respectively. In addition, the fibre thickness for 4 wt% PEO, 5 wt% PEO, 6 wt% PEO and 7 wt% PEO nanofibres were 269 ± 3 μm, 664 ± 4 μm, 758 ± 7 μm and 1329 ± 44 μm, respectively. Contrarily, the surface roughness for 4 wt% PEO, 5 wt% PEO, 6 wt% PEO and 7 wt% PEO nanofibres were 55.6 ± 9 nm, 42.8 ± 6 nm, 42.7 ± 7 nm and 36.6 ± 1 nm, respectively. PEO nanofibres showed the same burst release pattern and rate due to the same molecular weight of PEO with a stable release rate profile after 15 min. It also demonstrates that the percentage of PEO nanofibre release increased with the increasing PEO concentration due to the fibre diameter and thickness. The findings showed that all PEO nanofibres formulations were non-toxic to MCF-7 cells. It is suggested that 5 wt% PEO nanofibre exhibited non-cytotoxic characteristics by maintaining the cell viability from dose 0-1000 μg/ml and did not induce the number of colonies. Therefore, 5 wt% PEO nanofibre is the optimal nanofibre concentration and was suggested as a suitable base polymer matrix or carrier with potential use for diagnostic purposes. The findings in this study have demonstrated the influence of cell growth and viability, including the effects of PEO nanofibre formulations on cancer progress characteristics to achieve a permissible PEO nanofibre concentration limit that can be a benchmark in medical applications, particularly diagnostic applications.

Rotary Jet Spinning (RJS): A Key Process to Produce Biopolymeric Wound Dressings

Wounds result from different causes (e.g., trauma, surgeries, and diabetic ulcers), requiring even extended periods of intensive care for healing, according to the patient's organism and treatment. Currently, wound dressings generated by polymeric fibers at micro and nanometric scales are promising for healing the injured area. They offer great surface area and porosity, mimicking the fibrous extracellular matrix structure, facilitating cell adhesion, migration, and proliferation, and accelerating the wound healing process. Such properties resulted in countless applications of these materials in biomedical and tissue engineering, also as drug delivery systems for bioactive molecules to help tissue regeneration. The techniques used to engineer these fibers include spinning methods (electro-, rotary jet-), airbrushing, and 3D printing. These techniques have important advantages, such as easy-handle procedure and process parameters variability (type of polymer), but encounter some scalability problems. RJS is described as a simple and low-cost technique resulting in high efficiency and yield for fiber production, also capable of bioactive agents' incorporation to improve the healing potential of RJS wound dressings. This review addresses the use of RJS to produce polymeric fibers, describing the concept, type of configuration, comparison to other spinning techniques, most commonly used polymers, and the relevant parameters that influence the manufacture of the fibers, for the ultimate use in the development of wound dressings.

Polysaccharide-based nanofibers for pharmaceutical and biomedical applications: A review

Nanofibers are fibrous nanocarriers that can be synthesized from natural polymers, synthetic polymers, semiconducting materials, composite materials, and carbon-based materials. Recently, natural polysaccharides-based nanofibers are gaining attention in the field of pharmaceuticals and biomedical as these are biocompatible, biodegradable, non-toxic, and economic. Nanofibers can deliver a significant amount of drug to the targeted site and provide effective interaction of therapeutic agent at the site of action due to a larger surface area. Other important advantages of nanofibers are low density, high porosity, small pore size, high mechanical strength, and low cost. In this review, natural polysaccharides such as alginate, pullulan, hyaluronic acid, dextran, cellulose, chondroitin sulfate, chitosan, xanthan gum, and gellan gum are discussed for their characteristics, pharmaceutical utility, and biomedical applications. The authors have given particular emphasis to the several fabrication processes that utilize these polysaccharides to form nanofibers, and their recent updates in pharmaceutical applications such as drug delivery, tissue engineering, skin disorders, wound-healing dressings, cancer therapy, bioactive molecules delivery, anti-infectives, and solubility enhancement. Despite these many advantages, nanofibers have been explored less for their scale-up and applications in advanced therapeutic delivery.

Oxidized Chitosan-Tobramycin (OCS-TOB) Submicro-Fibers for Biomedical Applications

Chitosan (CS) is a biodegradable, biocompatible, and non-toxic natural amino-poly-saccharide with antibacterial ability, owing to its positively charged amino groups. However, the low charge density leads to poor antibacterial efficiency which cannot meet the biomedical application requirements. In this study, Tobramycin (TOB) was grafted onto the backbone of oxidized chitosan (OCS) to synthesize oxidized chitosan-tobramycin (OCS-TOB). FTIR, ¹H NMR and elemental analysis results demonstrated that OCS-TOB was successfully synthesized. OCS-TOB/PEO composite fibrous materials were produced by a self-made centrifugal spinning machine. In vitro experiments showed that cells proliferated on the submicro-fibrous OCS-TOB/PEO of appropriate concentration, and the antibacterial ability of OCS-TOB was much improved, compared with pristine CS. The results demonstrated that OCS-TOB/PEO nanofibrous materials could potentially be used for biomedical applications.

Solution blow spinning of highly deacetylated chitosan nanofiber scaffolds for dermal wound healing

Biocompatible fibrous scaffolds based on highly deacetylated chitosan were fabricated using high-throughput solution blow spinning. Scanning electron microscopy analysis revealed that the chitosan nanofiber scaffolds had ultrafine and continuous fibers (300-1200 nm) with highly interconnected porous structures (30-75% porosity), mimicking some aspects of the native extracellular matrix in skin tissue. Post-treatment of as-spun nanofibers with aqueous potassium carbonate solution resulted in a fibrous scaffold with a high chitosan content that retained its fibrous structural integrity for cell culture. Analysis of the mechanical properties of the chitosan nanofiber scaffolds in both dry and wet conditions showed that their strength and durability were sufficient for wound dressing applications. Significantly, the wet scaffold underwent remarkable elastic deformation during stretch such that the elongation at break dramatically increased to up to 44% of its original length, showing wavy fiber morphology near the break site. The culture of normal human dermal fibroblast cells onto scaffolds for 1-14 days demonstrated that the scaffolds were highly compatible and a suitable platform for cell adhesion, viability, and proliferation. Secretion profiles of wound healing-related proteins to the cell culture medium demonstrated that chitosan fibers were a promising scaffold for wound healing applications. Overall, the dense fibrous network with high porosity of the chitosan nanofiber scaffold and their mechanical properties indicate that they could be used to design and fabricate new materials that mimic the epidermis layer of natural skin.

Orthogonal Optimization Research on Various Nozzles of High-Speed Centrifugal Spinning

High-speed centrifugal spinning is a burgeoning method of fabricating nanofibers by use of the centrifugal force field. This article studied four different spinning nozzles, which were called stepped nozzle, conical-straight nozzle, conical nozzle, and curved-tube nozzle, to explore the optimal nozzle structures for fabricating nanofibers. According to the principle of centrifugal spinning, the spinning solution flow states within the four nozzles were analyzed, and the solution outlet velocity model was established. Then, the structural parameters of the four kinds of nozzles were optimized with the spinning solution outlet velocity as the test index by combining the orthogonal test and numerical simulation. Based on the orthogonal test results, the influence of nozzle structure parameters on the solution outlet velocity was analyzed, and the best combination of parameters of the centrifugal spinning nozzle structure was obtained. Subsequently, the four kinds of nozzles were used to fabricate nanofibers in the laboratory, under different solution concentration, motor rotation speed, and outlet diameters. Finally, the scanning electron microscope (SEM) was applied to observe the morphology and surface quality of nanofibers. It was found that the surface of nanofibers manufactured by the conical-straight nozzle and curved-tube nozzle was smoother than that by stepped and conical nozzles, and the fiber diameter by the conical-straight nozzle was minimal, followed by curved-tube nozzles, stepped nozzles, and conical nozzles in the diameter distribution of nanofibers.

Fabrication of gelatin nanofiber webs via centrifugal spinning for N95 respiratory filters

Due to the impact of the Covid-19 pandemic, the usage of numerous protective face masks has faced an explosion in demand around the world. Therefore, the need to reduce the environmental pollution caused by disposable single-use face masks has become vital. Recently, alternative raw material solutions have been discussed to eliminate the consumption of single-use plastics. Within this research, gelatin nanofibers were fabricated via centrifugal spinning technique, and filtration media were investigated in terms of air permeability and filtration efficiency. In addition, morphological properties were examined with scanning electron microscopy. Fabricated fibers have a changing average diameter range from 232 to 778 nm, and targeted 95% filtration efficiency was achieved in several compositions. It was proven that biodegradable gelatin nanofibers could be a sustainable alternative for disposable N95 respiratory filters.

Research progress, models and simulation of electrospinning technology: a review

In recent years, nanomaterials have aroused extensive research interest in the world's material science community. Electrospinning has the advantages of wide range of available raw materials, simple process, small fiber diameter and high porosity. Electrospinning as a nanomaterial preparation technology with obvious advantages has been studied, such as its influencing parameters, physical models and computer simulation. In this review, the influencing parameters, simulation and models of electrospinning technology are summarized. In addition, the progresses in applications of the technology in biomedicine, energy and catalysis are reported. This technology has many applications in many fields, such as electrospun polymers in various aspects of biomedical engineering. The latest achievements in recent years are summarized, and the existing problems and development trends are analyzed and discussed.

Recent applications of electrical, centrifugal, and pressurised emerging technologies for fibrous structure engineering in drug delivery, regenerative medicine and theranostics

Advancements in technology and material development in recent years has led to significant breakthroughs in the remit of fiber engineering. Conventional methods such as wet spinning, melt spinning, phase separation and template synthesis have been reported to develop fibrous structures for an array of applications. However, these methods have limitations with respect to processing conditions (e.g. high processing temperatures, shear stresses) and production (e.g. non-continuous fibers). The materials that can be processed using these methods are also limited, deterring their use in practical applications. Producing fibrous structures on a nanometer scale, in sync with the advancements in nanotechnology is another challenge met by these conventional methods. In this review we aim to present a brief overview of conventional methods of fiber fabrication and focus on the emerging fiber engineering techniques namely electrospinning, centrifugal spinning and pressurised gyration. This review will discuss the fundamental principles and factors governing each fabrication method and converge on the applications of the resulting spun fibers; specifically, in the drug delivery remit and in regenerative medicine.

Multi-Functional Core-Shell Nanofibers for Wound Healing

Core-shell nanofibers have great potential for bio-medical applications such as wound healing dressings where multiple drugs and growth factors are expected to be delivered at different healing phases. Compared to monoaxial nanofibers, core-shell nanofibers can control the drug release profile easier, providing sustainable and effective drugs and growth factors for wound healing. However, it is challenging to produce core-shell structured nanofibers with a high production rate at low energy consumption. Co-axial centrifugal spinning is an alternative method to address the above limitations to produce core-shell nanofibers effectively. In this study, a co-axial centrifugal spinning device was designed and assembled to produce core-shell nanofibers for controlling the release rate of ibuprofen and hEGF in inflammation and proliferation phases during the wound healing process. Core-shell structured nanofibers were confirmed by TEM. This work demonstrated that the co-axial centrifugal spinning is a high productivity process that can produce materials with a 3D environment mimicking natural tissue scaffold, and the specific drug can be loaded into different layers to control the drug release rate to improve the drug efficiency and promote wound healing.

Recent Developments in Chitosan-Based Micro/Nanofibers for Sustainable Food Packaging, Smart Textiles, Cosmeceuticals, and Biomedical Applications

Chitosan has many useful intrinsic properties (e.g., non-toxicity, antibacterial properties, and biodegradability) and can be processed into high-surface-area nanofiber constructs for a broad range of sustainable research and commercial applications. These nanofibers can be further functionalized with bioactive agents. In the food industry, for example, edible films can be formed from chitosan-based composite fibers filled with nanoparticles, exhibiting excellent antioxidant and antimicrobial properties for a variety of products. Processing 'pure' chitosan into nanofibers can be challenging due to its cationic nature and high crystallinity; therefore, chitosan is often modified or blended with other materials to improve its processability and tailor its performance to specific needs. Chitosan can be blended with a variety of natural and synthetic polymers and processed into fibers while maintaining many of its intrinsic properties that are important for textile, cosmeceutical, and biomedical applications. The abundance of amine groups in the chemical structure of chitosan allows for facile modification (e.g., into soluble derivatives) and the binding of negatively charged domains. In particular, high-surface-area chitosan nanofibers are effective in binding negatively charged biomolecules. Recent developments of chitosan-based nanofibers with biological activities for various applications in biomedical, food packaging, and textiles are discussed herein.

Advances in Functional Polymer Nanofibers: From Spinning Fabrication Techniques to Recent Biomedical Applications

Functional polymeric micro-/nanofibers have emerged as promising materials for the construction of structures potentially useful in biomedical fields. Among all kinds of technologies to produce polymer fibers, spinning methods have gained considerable attention. Herein, we provide a recent review on advances in the design of micro- and nanofibrous platforms via spinning techniques for biomedical applications. Specifically, we emphasize electrospinning, solution blow spinning, centrifugal spinning, and microfluidic spinning approaches. We first introduce the fundamentals of these spinning methods and then highlight the potential biomedical applications of such micro- and nanostructured fibers for drug delivery, tissue engineering, regenerative medicine, disease modeling, and sensing/biosensing. Finally, we outline the current challenges and future perspectives of spinning techniques for the practical applications of polymer fibers in the biomedical field.

Functional Nanofibrous Biomaterials of Tailored Structures for Drug Delivery-A Critical Review

Nanofibrous biomaterials have huge potential for drug delivery, due to their structural features and functions that are similar to the native extracellular matrix (ECM). A wide range of natural and polymeric materials can be employed to produce nanofibrous biomaterials. This review introduces the major natural and synthetic biomaterials for production of nanofibers that are biocompatible and biodegradable. Different technologies and their corresponding advantages and disadvantages for manufacturing nanofibrous biomaterials for drug delivery were also reported. The morphologies and structures of nanofibers can be tailor-designed and processed by carefully selecting suitable biomaterials and fabrication methods, while the functionality of nanofibrous biomaterials can be improved by modifying the surface. The loading and releasing of drug molecules, which play a significant role in the effectiveness of drug delivery, are also surveyed. This review provides insight into the fabrication of functional polymeric nanofibers for drug delivery.