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.
Hamdi
G
G
Laboratoire de Pharmacotechnie et Biopharmacie, URA CNRS 1218, Faculté de Pharmacie, Université de Paris-Sud, Châtenay-Malabry, France.
Ponchel
G
G
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