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. 2020 Feb 6;12(2):139.
doi: 10.3390/pharmaceutics12020139.

The Effect of Solvent Vapor Annealing on Drug-Loaded Electrospun Polymer Fibers

Yu-Jing Chiu  1   2   3   4 , Ziwei Zhang  4 , Karolina Dziemidowicz  4 , Christos-Georgios Nikoletopoulos  4 , Ukrit Angkawinitwong  4 , Jiun-Tai Chen  1   2   3 , Gareth R Williams  4
Affiliations

The Effect of Solvent Vapor Annealing on Drug-Loaded Electrospun Polymer Fibers

Yu-Jing Chiu et al. Pharmaceutics. .

Abstract

Electrospinning has emerged as a powerful strategy to develop controlled release drug delivery systems but the effects of post-fabrication solvent vapor annealing on drug-loaded electrospun fibers have not been explored to date. In this work, electrospun poly(ԑ-caprolactone) (PCL) fibers loaded with the hydrophobic small-molecule spironolactone (SPL) were explored. Immediately after fabrication, the fibers are smooth and cylindrical. However, during storage the PCL crystallinity in the fibers is observed to increase, demonstrating a lack of stability. When freshly-prepared fibers are annealed with acetone vapor, the amorphous PCL chains recrystallize, resulting in the fiber surfaces becoming wrinkled and yielding shish-kebab like structures. This effect does not arise after the fibers have been aged. SPL is found to be amorphously dispersed in the PCL matrix both immediately after electrospinning and after annealing. In vitro dissolution studies revealed that while the fresh fibers show a rapid burst of SPL release, after annealing more extended release profiles are observed. Both the rate and extent of release can be varied through changing the annealing time. Further, the annealed formulations are shown to be stable upon storage.

Keywords: annealing; drug delivery system; electrospinning; poly(ԑ-caprolactone); post-treatment.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Chemical structures of PCL and SPL, along with a schematic illustration of the experimental procedures adopted in this work.
Figure 2
Figure 2
SEM images and diameter distributions for the fresh (a,b) PCL and (c,d) SPL-loaded PCL fibers. (e) FT–IR spectra.
Figure 3
Figure 3
(a) Graphical illustration of the solvent vapor annealing process. (b–g) SEM images of (b) PCL-6, (c) PCL-48, (d) PCL-72, (e) PCL-SPL-6, (f) PCL-SPL-48, and (g) PCL-SPL-72.
Figure 4
Figure 4
(a) Graphical illustration of the fibers before and after annealing. (b) XRD patterns. (c) DSC curves (exo up). (d) Plot of percentage crystallinity against the annealing time.
Figure 5
Figure 5
In vitro SPL release profiles. Data are represented as mean ± S.D. from three independent experiments.
Figure 6
Figure 6
(a) Schematic illustration of the transformation process to form shish-kebab structures. (b) XPS spectra of the SPL-loaded fibers.
See this image and copyright information in PMC

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