Scale-up of electrospinning technology: Applications in the pharmaceutical industry

Electrospinning (ES) was originally reported in 1899 and the technology has been used since for the fabrication of con- tinuous fibers (Cooley, 1899).

Beginning from the 1980s and particularly during the recent decade, the technology has gained increasing attention. Possibly this can be attributed to the surging interest in nanotechnology, as ultrafine micro- or nanofibers or fibrous structures of various polymers or cyclodextrins can easily be fabricated using this process. The applications of electrospun products are expanding, especially in areas relating to drug delivery and tissue engineering (Hu et al., 2014; Sill & von Recum, 2008; Thakkar & Misra, 2017).

Electrospinning is a low-cost technology to generate dried fibers by utilizing the electrostatic forces on a liquid feed to turn it into ultrafine (normally <10 μm; Cramariuc et al., 2013) fiber structures, which can dry instantly at room tem- perature during process operation. The basic technology is called single-needle ES (SNES; Figure 1), during which the fiber-forming excipient (polymer or cyclodextrin, lipid, etc.) is dissolved in a solvent and the solution is fed into a single spinneret at a constant, controlled flow rate. High voltage is applied between the spinneret and the grounded collector, which causes the formation of a Taylor cone. If the electrostatic forces overcome the surface tension, a liquid jet breaks out from the cone (Taylor, 1964) and stabilizes between the nozzle and the collector as a continuous stream. During the process, the jets get elongated gaining a fiber-like structure, and the solvent evaporates instantaneously due to the high surface area, as the fibers are often submicron-sized.

During the last decades, electrospun fibers have become attractive oral drug delivery systems, mostly because they can improve the absorption of poorly soluble drugs by enhancing the dissolution rate of drug molecules through amorphization.

Abstract
Recently, electrospinning (ES) of fibers has been shown to be an attractive strategy for drug delivery. One of the main features of ES is that a wide variety of drugs can be loaded into the fibers to improve their bioavailability, to enhance dissolution, or to achieve controlled release.

Besides, ES is a continuous technology with low energy consumption, which can make it a very economic production alternative to the widely used freeze-drying and spray drying. However, the low production rate of laboratory-scaled ES has limited the industrial application of the technology so far. This article covers the various ES technologies developed for scaled-up fiber production with an emphasis on pharmaceutically relevant examples.

The methods used for increasing the productivity are complied, which is followed by a review of specific examples from literature where these technologies are utilized to produce oral drug delivery systems. The different technologies are compared in terms of their basic principles, advantages, and limitations. Finally, the different downstream processing options to prepare tablets or capsules containing the electrospun drug are covered as well. Continue reading on electrospinning

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