Biomedical Engineering Reference
In-Depth Information
visible light is less toxic to tissues than UV light, the system could be
applicable directly for clinical therapy.
We have used this system to provide visible light-curable biosealants.
The aqueous viscous solution of polymer derivative and dye mixture has
been employed as a direct tooth-pulp-capping material in dentistry [76]. In
addition, when the biosealant was used to cover a damaged region of skin
in a mouse model, it signifi cantly enhanced recovery [77, 78]. Considering
these results, this system could be useful as a new type of visible light-
induced crosslinked biosealant.
11.4.1 Gelatin
Furfuryl groups have been incorporated into gelatin using furfuryl isocya-
nate [76]. Subsequently, the modifi ed gelatin was mixed with Rose Bengal
in water and irradiated by visible light to form hydrogels. In addition,
when the solution was cast on a plate, dried, and photoirradiated in the
presence of a photomask, a micropattern was formed that matched that on
the photomask. The gelatin-immobilized regions enhanced cell adhesion.
It was also confi rmed that gelatin incorporating furfuryl and Rose Bengal
had no signifi cant toxicity. This modifi ed gelatin has been employed as a
direct tooth-pulp-capping material in dentistry.
11.4.2 Chitosan
Chitosan employed for preparing UV-reactive chitosan was also utilized
for preparing visible light-curable chitosan. Incorporation of furan groups
was performed by furfuryl glycidyl ether or furfuryl isocyanate as shown
in Figure 11.15. LMW-CS or LMC-O-CMCS was dissolved in water and pH
was adjusted to 11 using NaOH solution at room temperature. Furfuryl
glycidyl ether or furfuryl isocyanate dissolved in dimethylsulfoxide was
added to the chitosan solution under ice and the solution was heated and
stirred. After a suitable reaction time, the solution was neutralized and the
modifi ed chitosan was purifi ed by dialysis.
Micropatterning using photomasking was performed to confi rm the
photoreactivity of a system composed of furfurylated chitosan and Rose
Bengal. Micropatterning is useful to check the photoreactivity because it
allows light-irradiated surfaces to be compared directly with those not
irradiated. The micropattern clearly matched the photomask. This result
showed that solidifi cation occurred only on the visible light-irradiated
area. The surface wettability of the solidifi ed chitosan was investigated
by contact angle measurement, confi rming that solidifi cation of chitosan
derivatives by visible light irradiation produced a hydrophobic surface.
The furfurylated chitosan derivatives were water soluble, but after
crosslinking they became water insoluble. The degree of crosslinking
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