Enzymatic degradation of epichlorohydrin crosslinked starch microspheres by alpha-amylase.
OBJECTIVE
The influence of chemical parameters on the sensitivity to enzymatic degradation by alpha-amylase of starch microspheres cross-linked by epichlorohydrin was studied.


METHODS
Starch microspheres were prepared using epichlorohydrin as a crosslinking agent. Their swelling degree, reflecting the number of glycerol diether bridges in the polymeric network, and the number of non-crosslinking monoglycerol ether groups corresponding to a side-reaction of epichlorohydrin with starch were determined. Degradation rates of the microspheres in presence of porcine alpha-amylase were determined by a microvolumetric method.


RESULTS
Degradation by alpha-amylase was surface-controlled and could be modulated by the introduction in the polymeric network of: (i) non-hydrolysable alpha-1,6 bonds related to the presence of amylopectin in the raw starch, (ii) glycerol diether and, (iii) monoether groups, all of these being likely to block the activity of alpha-amylase. In the case of highly cross-linked microspheres, the number of glycerol monoether pendent chains had a predominant effect on the degradation rate which ranged between 10(-2) and 10(-5) min(-1).


CONCLUSIONS
It was possible to modulate simultaneously the swelling degree and the enzymatic degradability of starch microspheres by adjusting the chemical parameters during the crosslinking reaction.
Laboratoire de Pharmacotechnie et Biopharmacie, URA CNRS 1218, Faculté de Pharmacie, Université de Paris-Sud, Châtenay-Malabry, France.
G
G
Hamdi
G
G
Ponchel
D003432:Cross-Linking Reagents; D004811:Epichlorohydrin / Q000737:chemistry / Q000378:metabolism*; D005995:Glyceryl Ethers / Q000737:chemistry; D008863:Microspheres; D013213:Starch / Q000737:chemistry / Q000378:metabolism*; D000516:alpha-Amylases / Q000378:metabolism*
D003432:Cross-Linking Reagents; D005995:Glyceryl Ethers; D004811:Epichlorohydrin; D013213:Starch; D000516:alpha-Amylases