Spider Silk-production and Biomedical Applications - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 153

body reaction were found, indicating in vivo tolerance of the silk (Allmeling et al.,
2008). Another type of spider silk, egg sac silk, has been implanted subcutaneously
in rats (Gellynck et al., 2008a). This study showed that during the first four weeks of
implantation, egg sack silk treated with Proteinase K and/or trypsin evoked the same
degree of inflammation as the widely used suture material Vicryl ® (polyglactin). Egg
sack silk that had not been subjected to enzymatical treatment evoked a severe inflam-
matory reaction, suggesting that the egg sack silk contains an immunogenic coating
and/or was contaminated with agents that was removed by proteolysis. Also, Vollrath
et al. (2002) have shown that both native dragline silk and swathing silk are degraded
with time when implanted subcutaneously in pigs (Vollrath et al., 2002).
For the recombinantly produced spider silks, there are two studies where the in
vitro cytocompatibility has been complemented with in vivo studies (Baoyong et al.,
2010; Fredriksson et al., 2009). In the first one, recombinant spider silk fibers were
implanted subcutaneously in rats (Fredriksson et al., 2009). The fibers did not give rise
to any macroscopic signs of inflammation, and the histological examination revealed
an inflammatory reaction at the same level as observed for the control (silk worm
silk suture, Mersilk ® ). Surprisingly, newly formed capillaries could be detected in the
centre of the recombinant spider silk fiber bundle already after one week of implanta-
tion. This suggests that the recombinant spider silk may have angiogenic properties,
which would be beneficial in example tissue engineering and wound dressings. In line
with this, recombinantly produced spider silk (pNSR-32 and pNSR-16, both contain-
ing the tripeptide RGD) used as dressings of deep burns in rats, have been suggested
to be as efficient in promoting healing as clinically used collagen sponges (Baoyong
et al., 2010).

CoNClusioN
Recombinant spider silk represents an interesting material for cell culture matrices,
implants and other medical devices. Both in vitro and in vivo studies show that the
material is cytocompatible and tolerated when implanted. However, the nature of spi-
der silk proteins still makes them difficult to produce-a problem that must be solved
before the material can be used in any commercial application.

KeyWords

• elastin like peptide

• hexafluoroisopropanol

• lipopolysaccharides

• major ampullate spidroin

• spiders

aCKNoWledGmeNts
We are grateful to prof. Jan Johansson for constructive comments on the manuscript.
This work was financially supported by the Swedish Research Council.