Hierarchically electrospun nanofibers and their applications: A review

Electrospinning is a popular method for generating long and continuous nanofibers due to its simplicity and versatility. However, conventional electrospun products have weak strength and low availability, which restrict their functionality in complex applications. Hierarchical morphology introduces additional and distinctive structural layers onto electrospun fibers. This requires either an extra fabrication step or controlling electrospinning parameters to achieve the desired morphology. Hierarchical morphology can improve the properties of electrospun nanofibers while also mitigating the undesired characteristics. This review discusses the primary and secondary hierarchical structures of electrospun nanomaterials. Hierarchical structures were found to enhance the functionality of nanomaterials and improve pore connectivity and surface areas of electrospun nanofibers. A further advantage is the ability to impart multiple functionalities on nanostructures. With a better understanding of some of the dominant hierarchical structures, nanomaterials applications in drug delivery, tissue engineering, catalysis, and energy devices industries can be improved

Electrospun nanofiber-based niflumic acid capsules with superior physicochemical properties

The aim of this study was to assess whether nanofibrous drug mats have potential as delivery systems for poorly water-soluble drugs. Amorphous nanofiber mats from a model poorly water-soluble active pharmaceutical ingredient (API), niflumic acid, together with the polymer excipient, polyvinyl pyrrolidine, were prepared by nozzle-free electrospinning. This technique offers a scalable way for drug formulation, and by increasing the surface area of the drug, the dissolution rate and therefore bioavailability of the API can be improved. In this study, both the amount of the dissolved active ingredient and the dissolution kinetics has been improved significantly when the nanofibrous mats were used in the drug formulation. A 15-fold increase in the dissolved amount of the produced amorphous niflumic acid nanofiber was observed compared to the dissolved amount of the raw drug within the first 15 minutes. Capsule formulation was made by mixing the electrospun nanofibers with a microcrystalline cellulose filler agent. When comparing the dissolution rate of the capsule formulation on the market with the nanofibrous capsules, a 14-fold increase was observed in the dissolved drug amount within the first 15 minutes

Ultrafast fabrication of Nanofiber-based 3D Macrostructures by 3D electrospinning

Fabrication of macroscopic three-dimensional (3D) structures made of nanofibers of widely used polymers is reported. 3D structures have several benefits over conventional flat two-dimensional (2D) structures by the added dimension. The structures have been fabricated by the 3D electrospinning technology that can build 3D structures rapidly due to certain additives in the solution and appropriate process conditions. The process parameters of 3D electrospinning have been identified and investigated to better understand the formation mechanism of the 3D build-up for polystyrene (PS), polyacrylonitrile (PAN), and polyvinylpyrrolidone (PVP). Different types of electrodes were inserted in the electrospinning chamber to alter the electric field and have better control over the shape of the 3D structure. The upscalability of this technology was investigated by using a standard electrospinner and a nozzle-free electrospinning setup. It was possible to manufacture 3D structures with these devices, highlighting the versatility of this technology. 3D electrospinning opens the pathway for the facile fabrication of macroscopic 3D structure with microfibrous features on a commercial scale