Biomedical Engineering Reference
In-Depth Information
Fig. 3
Delocalized protease activity in response to pro inflammatory implants over the time period.
Fluorescent images were taken at 0, 6 and 48h. The format of implantation was following:
1
Porous
glass implant soaked in dead bacteria,
2
Porous glass implant,
3
Magnesium,
4
Poly-L-lactic acid,
5
Heat killed bacteria and
6
Surgery without implantation.
Dashed circles
represent the site of
implantation
non-inflammatory materials were subcutaneously implanted in mice. A fluorophore
that can be activated by inflammatory proteases (cathepsins) was injected intra-
venously and whole body imaging was performed. The results showed an increase
in fluorescence intensity with time (Fig.
3
). The signal peaks appeared to be delocal-
ized and could not be assigned to individual implants. Furthermore, opaque implants
quenched even the background fluorescence. This phenomenon could be used to
precisely localize the position of the implants (Fig.
3
; implant 3 at 6h and 48h). At
48h, the implant with bacteria showed brighter fluorescence intensity as compared
to biocompatible glass implants (Fig.
3
;48h).
3.3 Imaging Cell Growth Stimulatory Signals
Injury stimulates cell growth and tissue repair processes. Cell growth can be stimu-
lated by lipase signaling [
29
]. Autotaxin is a specific lipase involved in cell growth and
motility signaling. ATX Red is a near infra-red fluorescent precursor molecule that
can act as autotaxin lipase substrate. A fluorescent product is generated by autotaxin
that can be detected by in vivo imaging. Various biocompatible and inflammatory
implant materials were implanted in mice to evaluate this method. After implanta-
tion, mice were injected intravenously with ATX red (Fig.
4
a, b, 0h). To monitor
the basal levels of autotaxin, one mouse without implants was included (Fig.
4
c).
Implants with bacteria induced a higher autotaxin activity as compared to biocom-
patible glass implant (Fig.
4
; implant 2, 48h). A signal peak was obtained 48h after
