M. Kunioka et K. Furusawa, POLY(GAMMA-GLUTAMIC ACID) HYDROGEL PREPARED FROM MICROBIAL POLY(GAMMA-GLUTAMIC ACID) AND ALKANEDIAMINE WITH WATER-SOLUBLE CARBODIIMIDE, Journal of applied polymer science, 65(10), 1997, pp. 1889-1896
Poly(gamma-glutamic acid) (PGA) hydrogels have been prepared from micr
obial PGA produced by Bacillus subtilis F-02-1, water-soluble carbodii
mide (WSC), and alkanediamines such as 1,3-propanediamine (1,3-PD), 1,
4-butanediamine (1,4-BD), and 1,6-hexanediamine (1,6-HD) in aqueous me
dium. The carboxyl groups of PGA were activated by the addition of WSC
in deionized water, and the PGA-WSC adduct was produced. PGA hydrogel
s could be produced after the mixing of PGA-WSC and alkanediamine in d
eionized water. This alkanediamine to which both amino groups reacted
with the carboxyl groups of PGA plays the role of a crosslinking point
. When the amount of PGA was 100 mg, WSC was 50 mg or more, and 1,3-PD
was 25 mu L or more in 2 mt of deionized water, PGA hydrogels could b
e produced. Specific water contents (weight of absorbed water/weight o
f dry gel) ranged from 300 to 1,993 g/g in the case of 1,3-PD. If the
PGA-WSC adduct was freeze-dried, the yield of the PGA hydrogel became
higher than that when PGA-WSC was not freeze-dried. The highest yield
of the PGA. hydrogel from 100 mg of PGA, 100 mg of WSC, and 100 mu L o
f 1,3-PD in 2 mt of deionized water using the freeze-dry method was 39
.9 mg of dry PGA hydrogel with a 650 g/g specific water content. The o
rder of yield was 1,6-HD > 1,4-BD > 1,3-PD from 100 mg of PGA-100 mg o
f WSC in 2 mt of deionized water. The order of the specific water cont
ent was 1,3-PD (462 g/g) > 1,4-BD (234 g/g) > 1,6-HD (199 g/g). This o
rder may be due to the higher reaction probability between the activat
ed carboxyl groups in the PGA-WSC and both amino groups in the alkaned
iamine with longer methylene chains, indicating that the crosslinking
density of the PGA hydrogel is higher and the specific water content i
s lower. (C) 1997 John Wiley & Sons, Inc.