Accelerated wound-healing capabilities of a dressing fabricated from silkworm cocoon
Introduction
Regenerated silk fibroin materials have shown much potential for applications in various technological fields because of the material’s properties and production capacity [1], [2]. Silk fibroin has also been recognized as an important biological material owing to its excellent biocompatibility and regenerative performance [3], [4], [5]. Accordingly, silk fibroin has been investigated for use in wound dressings [6], [7], [8], [9]. However, producing these silk fibroin materials (electrospun silk scaffolds or silk fibroin films) requires a series of complex processing steps because silk fibroin cannot be acquired directly but must be extracted by dissolving degummed silk [10].
The dissolution of silk is a critical step in producing higher purity silk fibroin [11], [12]. Native silk has been dissolved in H3PO4-formic acid [13], LiBr (self-dialysis) [10], H3PO4, or ionic liquids [14] for the direct spinning of fibers and forming of film structures [15]; however, although these processes can produce silk fibroin materials, the processes are complicated, and the resulting fibers and film structures perform poorly [16]. A widely used alternative method of dissolving silk utilizes a CaCl2-ethanol-H2O solution; nonetheless, this approach requires self-dialysis, and the process is also complex and time-consuming [17], [18], [19]. These steps include the removal of sericin, the dissolving of silk proteins, and self-dialysis process, as well as the removal of the bioactive functional proteins that remain after the folding process. Following these methods, sericin is wasted in the silk degumming process, which is unfortunate because sericin has long been acknowledged to promote adhesion and the propagation of cells [20], [21], [22], [23].
To address these issues, researchers have given special attention to Bombyx mori cocoons themselves. Cocoons, which consist of twining silk fibers with continuous lengths of approximately 1000 m that are bonded together by sericin glue, are a typical natural fiber composite with hierarchical structures [24], [25], [26]. The compact structure of the silkworm cocoon (SC) provides high mechanical resistance against disturbance, allowing the cocoon to withstand threats from parasites and predators and providing security for pupal growth and development [27], [28]. As such, the protective function of the SC resembles the protection that the skin provides to the human body. This resemblance suggests that the full cocoon structure, including both sericin and fibroin might be beneficial for wound repair. However, there have been few relevant studies on the potential offered by SCs as a defense and survival tool for chrysalis [29], and there is almost no research on natural SCs that have been deployed in the field as a biological material [30], particularly for the purpose of wound healing.
Inspired by the protective functionality of the SC, we have designed a novel and easily implemented technique of directly preparing a SC sol-gel film (SCSF) wound dressing by partially dissolving a large piece of SC in a CaCl2-ethanol-H2O solution instead of indirectly preparing the material from regenerative fibroin films. This paper reports the synthesis of SCSF composites with different SC treatment times in the CaCl2-ethanol-H2O solution, as well as the systematic investigation of their structures, mechanical performances, biocompatibilities, and anti-bacterial activities. The rate of tissue regeneration and wound closure were also measured to evaluate the material’s efficacy for enhancing wound healing in comparison with Mepitel®, a commonly used silicon-coated polyamide net [31].
Section snippets
Materials and animals
The Bombyx mori cocoons used in this study were provided by the State Key Laboratory of Silkworm Genome Biology (Southwest University, Chongqing, China). All chemicals were purchased from Taixin Chemical Reagent Company (Chongqing, China) and used without further purification. All animal experiments and care were in compliance with institutional ethical use protocols and were approved by the National Center of Animal Science Experimental Teaching (ASET) at the College of Animal Science and
Transmittance characterization
Transparent wound dressings offer the advantage of allowing daily visual inspections without dressing removal, and therefore the dressings can typically be changed less frequently [37]. For this reason, Fig. 2 presents the transparency characteristics of the different SCSFs. Fig. 2A shows photographs of the SC and SCSFs. The background is entirely obscured by the SC. However, the SCSFs exhibit different degrees of transparency depending on the treatment time of the SCSF in the CaCl2-ethanol-H2O
Conclusions
SCSFs were successfully constructed by partly dissolving SCs in a solution of CaCl2-ethanol-H2O, and a series of SCSFs were prepared with different treatment times (30, 60, 90, and 120 min). Although the prolonged treatment times reduced the breaking strength of SCSFs, their extensibility was increased. SCSF-90 exhibited marked bacteriostatic capacity against S. aureus and E. coli. Following the demonstration of biocompatibility and efficacy, the results of in vivo experiments confirmed that
Acknowledgments
This work was funded by Hi-Tech Research and Development 863 Program of China Grant (No. 2013AA102507). This work was also supported by The Science and Technology Basic Condition Construction Project of Guangdong province (No. 2015A030303010).
References (56)
- et al.
Acta Biomater.
(2015) - et al.
Prog. Polym. Sci.
(2015) - et al.
Biomaterials
(2009) - et al.
Eur. Polym. J.
(2015) - et al.
Acta Biomater.
(2015) - et al.
Polymer
(2007) - et al.
Prog. Polym. Sci.
(2008) - et al.
Biomaterials
(2003) - et al.
Int. J. Biol. Macromol.
(2014) Biotechnol. Adv.
(2002)
Mater. Sci. Eng. C: Mater. Biol. Appl.
Compar. Biochem. Physiol. Mol. Integr. Physiol.
Mater. Sci. Eng. C: Mater. Biol. Appl.
Polymer
Biomaterials
Toxicol. In Vitro
Carbohydr. Polym.
Biophys. Chem.
Acta Biomater.
Int. J. Biol. Macromol.
Int. J. Biol. Macromol.
Polymer
Polymer
Biochimie
Carbohydr. Polym.
J. Biosci. Bioeng.
Lab. Invest.
Biosci. Biotechnol. Biochem.
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