Abstract
The objective of this proof-of-concept study was to develop a platform for controlled drug delivery based on silk fibroin (SF) and to explore the feasibility of using SF in oral drug delivery. The SF-containing matrixes were prepared via spray-drying and film casting, and the release profile of the model drug naproxen sodium was evaluated. Attenuated total reflectance Fourier transform infrared spectroscopy (FTIR) has been used to observe conformational changes in SF- and drug-containing compositions. SF-based films, spray-dried microparticles, and matrixes loaded with naproxen were prepared. Both FTIR spectra and in vitro dissolution data demonstrated that SF β-sheet conformation regulates the release profile of naproxen. The controlled release characteristics of the SF-containing compositions were evaluated as a function of SF concentration, temperature, and exposure to dehydrating solvents. The results suggest that SF may be an attractive polymer for use in controlled drug delivery systems.
Highlights
Silk fibroin (SF) is a natural polymer produced by a variety of insects and spiders
Bombyx mori silk is composed of a filament core protein, silk fibroin, and a glue-like coating consisting of a nonfilamentous protein, sericin
We investigated the effect of dehydrating solvents on formation of β-sheets in SF/gelatin blends and demonstrated that the treatment with glycerin is effective for the transformation of silk I to II which is in agreement with the literature data [32]
Summary
Silk fibroin (SF) is a natural polymer produced by a variety of insects and spiders. The best characterized silks are the dragline silk from the spider Nephila clavipes and the cocoon silk from the domesticated silkworm Bombyx mori, which has been used in textile production clinical sutures, and more recently as a scaffold for tissue regeneration [1,2,3]. Bombyx mori silk is composed of a filament core protein, silk fibroin, and a glue-like coating consisting of a nonfilamentous protein, sericin. The primary structure of Bombyx mori SF protein is characterized by the presence of three amino acids in a roughly 3 : 2 : 1 ratio: glycine (45%), alanine (30%), and serine (12%); and the sequence is dominated by [Gly-Ala-Gly-Ala-Gly-Ser]n. The repetitive sequence in hydrophobic residues dominates the βsheet structure, forming crystalline regions in SF fibers and films. The formation of these β-sheets results in insolubility in water. Hydrophobic regions of silk fibroin in aqueous solution assemble physically by hydrophobic interactions and eventually organize into hydrogels
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