Leukocyte interactions with silk sericin proteins for tissue engineering applications

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Copyright: Isahak, Naatasha Binte
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Abstract
This research investigates in vitro leukocyte interactions with sericin proteins from silkworm cocoons of Bombyx mori and Antherea mylitta silkworm species. Sericin from raw silk fibres has been implicated as a cause of inflammation in previous silk suture studies and these findings have hindered development of sericin as a biomaterial. Nonetheless, recent studies involving isolated sericin have suggested that it is antibacterial, UV resistant and able to absorb and release moisture easily. Sericin has also been shown to possess attractive wound healing properties and acceptable production of inflammatory mediators, causing much debate in its use as a biomaterial composite. Ultimately, sericin may be applied to the design of biosynthetic hydrogels for tissue engineering applications. Hence, there is a need to evaluate the role of sericin in the inflammatory response and determine its use as a biomaterial. The results from these in vitro studies will give a preliminary indication of the likelihood of sericin from these species to incite an inflammatory response. Isolated sericin proteins from both species were isolated and modified with methacrylate groups (sericin-MA) to photocrosslink with poly(vinyl alcohol). In vitro studies using leukocytes from whole blood samples and the monocytic cell line, U937, were conducted for investigation of neutrophil activation. Cell surface receptor expression and macrophage differentiation was evaluated by flow cytometry and fluorescence microscopy, and the release of TNF-α was measured by ELISA. Based on the findings of this research, sericin and sericin-MA of both silk species elicited negligible neutrophil activation in blood samples. However, sericin-MA appeared to trigger the early onset of macrophage differentiation and produced significant amounts of TNF-α in blood samples. In contrast, U937 studies exhibited no significant TNF-α released and no apparent impact on macrophage differentiation. Considering that blood samples contain other cofactors that may influence inflammation, unavailable in culture media, blood samples are able to express the effects of sericin methacrylation. In conclusion, this research has demonstrated that sericin does not elicit a positive response by leukocytes and therefore indicates that sericin does not cause inflammation. Further work is required to investigate the effect of sericin-MA in chronic inflammation and in vivo response to silk/PVA hydrogels using mouse models to understand better the interactions between cells and incorporated sericin. This would greatly help in the development of silk/PVA hydrogels for applications in tissue engineering.
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Author(s)
Isahak, Naatasha Binte
Supervisor(s)
Martens, Penny
Poole-Warren, Laura
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Publication Year
2010
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Thesis
Degree Type
Masters Thesis
UNSW Faculty
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