Intrinsic antimicrobial properties of silk spun by genetically modified silkworm strains
The domesticated silkworm, Bombyx mori, is a fundamental insect for silk industry. Silk is obtained from cocoons, protective envelopes produced during pupation and composed of single raw silk filaments secreted by the insect silk glands. Currently, silk is used as a textile fibre and to produce new materials for technical and biomedical applications. To enhance the use of both fabrics and silk-based materials, great efforts to obtain silk with antimicrobial properties have been made. In particular, a convincing approach is represented by the enrichment of the textile fibre with antimicrobial peptides, the main effectors of the innate immunity. To this aim, silkworm-based transgenic techniques appear to be cost-effective strategies to obtain cocoons in which antimicrobial peptides are integrated among the silk proteins. Recently, cocoons transgenic for a recombinant silk protein conjugated to the silkworm Cecropin B antimicrobial peptide were obtained and showed enhanced antibacterial properties (Li et al. in Mol Biol Rep 42:19–25, https://doi.org/10.1007/s11033-014-3735-z, 2015a). In this work we used the piggyBac-mediated germline transformation to generate several transgenic B. mori lines able to overexpress Cecropin B or Moricin antimicrobial peptides at the level of the silk gland. The derived cocoons were characterised by increased antimicrobial properties and the resulting silk fibre was able to inhibit the bacterial growth of the Gram-negative Escherichia coli. Our results suggest that the generation of silkworm overexpressing unconjugated antimicrobial peptides in the silk gland might represent an additional strategy to obtain antimicrobial peptide-enriched silk, for the production of new silk-based materials.
KeywordsBombyx mori Transgenesis Silk Antimicrobial peptides
This work was supported by grants from Regione Lombardia to G.T. and G.F. in the framework of the Project ID 30141940 “SILKBIOTECH: biotechnological production of antimicrobial silk” (MIUR-Regione Lombardia 2012–2015) and by grants from the companies and institutions (Ratti srl, Res Pharma srl, Bioengineering laboratories srl, Tintoria Clerici srl, University of Insubria, Innovhub-SSI, Silk Area) participating to the same project as S.C.; from CARIPARO (Progetti di Eccellenza 2011/12) to S.C, F.S. and G.T. and from the Università degli Studi di Padova (CPDA154301) to F.S. A.B. was supported by a postdoctoral fellowship from Università degli Studi di Padova (CPDR100470). We are grateful to NARO (Japan) and EMBL (Germany) for providing the pBacFibH-Gal4/3xP3DsRed and pETM-22 plasmids, respectively. The authors wish to thank Paola D’Antona who participated in early experiments.
Compliance with ethical standards
Conflict of interests
All the authors declared that they have no conflict of interest.
Our study complies with institutional standards on silkworm research.
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