Antimicrobial Activity of Minocycline-Loaded Genipin-Crosslinked
Nano-Fibrous Chitosan Mats for Guided Tissue Regeneration
531
rier only) produced zones of inhibition.
4. Discussion
The swelling study demonstrated that membranes have
similar capacity to absorb fluid and any differences in
swelling capacity were not significant. Therefore, the
crosslinked membrane should have similar capacity to
absorb drugs, antibiotics, or growth factor solutions.
Unlike vapor crosslinking and solution crosslinking me-
thods, where materials are exposed to a crosslinking
agent that crosslinks polymer chains primarily on the
surface, in this study, the crosslinking agent is dispersed
within the polymer solution used for scaffold fabrication.
This method creates a more uniformly and thoroughly
crosslinked membrane, which likely contributed to im-
proved antibiotic retention as observed in this study and
more uniform degradation kinetics. A previous examina-
tion using x-ray diffraction showed that crystallinity was
decreased during crosslinking. This may have contrib-
uted to slightly lower swelling volumes, however this
difference was not significant.
In this study, genipin-crosslinked electrospun chitosan
was able to absorb minocycline and release it in an ex-
tended manner that remained bacteriostatic for longer
periods than uncrosslinked membranes (8 days as com-
pared to 4 days). These results are similar to reports by
others who have loaded biodegradable GTR membranes
with antibiotics/antiseptics such as tetracycline, doxycy-
cline or chlorhexidine [15-17]. Delayed degradation ki-
netics (Norowski et al., in review) contributed to the ex-
tended release seen from crosslinked membranes. Thus,
uncrosslinked chitosan membranes degraded faster and
resulted in lower minocycline loading and release levels.
One clinical investigation reported no improvements
in clinical parameters associated with the local applica-
tion of minocycline ointment before GTR therapy, but
this study did not investigate minocycline incorporation
into the GTR membrane itself, and only investigated the
use of type 1 collagen membranes. [18] Other investiga-
tions with a non-membrane local delivery system dem-
onstrated improvement in clinical parameters associated
with the use of minocycline microcapsules (Arestin®).
[19] This microcapsule study also showed that reduction
in periodontal pocket probing depth (improved clinical
outcomes) correlated strongly with the ability to inhibit
red complex bacteria in vitro, a sub-group of periodontal
pathogens that includes P. gingivalis, T. forsythia, and T.
denticola [19].
5. Conclusion
In this study, we have shown the ability of genipin-cross-
linked electrospun chitosan to deliver clinically relevant
levels of minocycline over an 8 day period. The eluted
minocycline was able to inhibit growth of P. gingivalis, a
model periopathogen, in vitro. Crosslinked membranes
released inhibitory levels of minocycline for 8 days while,
uncrosslinked membranes only inhibited growth for 4 days.
This prolonged minocycline elution profile suggests that
genipin-crosslinking improved the drug-carrier properties
of electrospun chitosan.
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