Fibrous hydrogels by electrospinning: Novel platforms for biomedical applications

Hydrogels, hydrophilic and biocompatible polymeric networks, have been used for numerous biomedical applications because they have exhibited abilities to mimic features of extracellular matrix (ECM). In particular, the hydrogels engineered with electrospinning techniques have shown great performances in biomedical applications. Electrospinning techniques are to generate polymeric micro/nanofibers that can mimic geometries of natural ECM by drawing micro/nanofibers from polymer precursors with electrical forces, followed by structural stabilization of them. By exploiting the electrospinning techniques, the fibrous hydrogels have been fabricated and utilized as 2D/3D cell culture platforms, implantable scaffolds, and wound dressings. In addition, some hydrogels that respond to external stimuli have been used to develop biosensors. For comprehensive understanding, this review covers electrospinning processes, hydrogel precursors used for electrospinning, characteristics of fibrous hydrogels and specific biomedical applications of electrospun fibrous hydrogels and highlight their potential to promote use in biomedical applications.

Scale-up of Electrospinning: Market Overview of Products and Devices for Pharmaceutical and Biomedical Purposes

Recently, the electrospinning (ES) process has been extensively studied due to its potential applications in various fields, particularly pharmaceutical and biomedical purposes. The production rate using typical ES technology is usually around 0.01-1 g/h, which is lower than pharmaceutical industry production requirements. Therefore, different companies have worked to develop electrospinning equipment, technological solutions, and electrospun materials into large-scale production. Different approaches have been explored to scale-up the production mainly by increasing the nanofiber jet through multiple needles, free-surface technologies, and hybrid methods that use an additional energy source. Among them, needleless and centrifugal methods have gained the most attention and applications. Besides, the production rate reached (450 g/h in some cases) makes these methods feasible in the pharmaceutical industry. The present study overviews and compares the most recent ES approaches successfully developed for nanofibers' large-scale production and accompanying challenges with some examples of applied approaches in drug delivery systems. Besides, various types of commercial products and devices released to the markets have been mentioned.

Electrospinning nanofiber technology: a multifaceted paradigm in biomedical applications

This review focuses on the process of preparation of nanofibers via Es, the design and setup of the instrument, critical parameter optimization, preferable polymers, solvents, characterization techniques, and recent development and biomedical applications of nanofibers.

Electrospun fibers based on carbohydrate gum polymers and their multifaceted applications

Electrospinning has garnered significant attention in view of its many advantages such as feasibility for various polymers, scalability required for mass production, and ease of processing. Extensive studies have been devoted to the use of electrospinning to fabricate various electrospun nanofibers derived from carbohydrate gum polymers in combination with synthetic polymers and/or additives of inorganic or organic materials with gums. In view of the versatility and the widespread choice of precursors that can be deployed for electrospinning, various gums from both, the plants and microbial-based gum carbohydrates are holistically and/or partially included in the electrospinning solution for the preparation of functional composite nanofibers. Moreover, our strategy encompasses a combination of natural gums with other polymers/inorganic or nanoparticles to ensue distinct properties. This early established milestone in functional carbohydrate gum polymer-based composite nanofibers may be deployed by specialized researchers in the field of nanoscience and technology, and especially for exploiting electrospinning of natural gums composites for diverse applications.

A Mini-Review: Needleless Electrospinning of Nanofibers for Pharmaceutical and Biomedical Applications

Electrospinning (ES) is a convenient and versatile method for the fabrication of nanofibers and has been utilized in many fields including pharmaceutical and biomedical applications. Conventional ES uses a needle spinneret for the generation of nanofibers and is associated with many limitations and drawbacks (i.e., needle clogging, limited production capacity, and low yield). Needleless electrospinning (NLES) has been proposed to overcome these problems. Within the last two decades (2004–2020), many research articles have been published reporting the use of NLES for the fabrication of polymeric nanofibers intended for drug delivery and biomedical tissue engineering applications. The objective of the present mini-review article is to elucidate the potential of NLES for designing such novel nanofibrous drug delivery systems and tissue engineering constructs. This paper also gives an overview of the key NLES approaches, including the most recently introduced NLES method: ultrasound-enhanced electrospinning (USES). The technologies underlying NLES systems and an evaluation of electrospun nanofibers are presented. Even though NLES is a promising approach for the industrial production of nanofibers, it is a multivariate process, and more research work is needed to elucidate its full potential and limitations.

A Novel Profiled Multi-Pin Electrospinning System for Nanofiber Production and Encapsulation of Nanoparticles into Nanofibers

Electrospinning with various machine configurations is being used to produce polymer nanofibers with different rates of output. The use of polymers with high viscosity and the encapsulation of nanoparticles for achieving functionalities are some of the limitations of the existing methods. A profiled multi-pin electrospinning (PMES) setup is demonstrated in this work that overcomes the limitations in the needle and needleless electrospinning like needle clogging, particle settling, and uncontrolled/uneven Taylor cone formation, the requirement of very high voltage and uncontrolled distribution of nanoparticles in nanofibers. The key feature of the current setup is the use of profiled pin arrangement that aids in the formation of spherical shape polymer droplet and hence ensures uniform Taylor cone formation throughout the fiber production process. With a 10 wt% of Polyvinyl Alcohol (PVA) polymer solution and at an applied voltage of 30 kV, the production rate was observed as 1.690 g/h and average fiber diameter obtained was 160.5 ± 48.9 nm for PVA and 124.9 ± 49.8 nm for Cellulose acetate (CA) respectively. Moreover, the setup also provides the added advantage of using high viscosity polymer solutions in electrospinning. This approach is expected to increase the range of multifunctional electrospun nanofiber applications.

Encapsulation and Release of Functional Nanodroplets Entrapped in Nanofibers

A method is presented for preserving the structural integrity of nanodroplets produced by emulsification. Droplets of different hydrophobic liquids such as essential oils or monomers are produced by the miniemulsion process. The miniemulsions are then electrospun to yield dextran nanofibers entrapping the hydrophobic nanodroplets. The nanodroplets are then successfully redispersed by dissolving the nanofibers in water. Furthermore, it is shown that nanofibers can be used to store a monomer and a catalyst as healing agents for ring-opening metathesis polymerization. After dissolution, the healing agents are released and a self-healing reaction takes place. Embedding, storage, and release of emulsion nanodroplets is a promising method that avoids potential destabilization of droplets by coalescence or Ostwald ripening.