Change in the V/B polymorph ratio and T-1 relaxation of epichlorohydrin crosslinked high amylose starch excipient

High amylose epichlorohydrin crosslinked starch excipient was examined to g ain understanding of the starch polymorph changes as the crosslinking degre e (CLD) increases University, creases. When the crosslinking degree is high , the sample is mostly amorphous, and the V/B ratio decreased. For this sam ple, "humidification" or "water soaking", cannot overcome crystallization r estraint due to the high crosslinking degree. The water soaked 20% CLD samp le show some sharp, low intensity double helix C-13 resonances. This sample is paracrystalline as can be seen from the collapse of the C(1) doublet to a singlet. Relaxation studies show that increasing crosslinking degree inc reases the amorphous content. It is also suggested that crosslinking is not homogeneous and that it is concentrated in the non-crystalline domain. A c orrelation was found between the decrease in content of B-type material and drug release kinetics. With increasing CLD, the reduction in crystalline o rder increases mobility, however, increasing covalent bonds in the excipien t matrix reduces mobility, Differences in relaxation rate of the several ov erlapping resonances in the 70-80 ppm range of the C-13 spectrum are pronou nced and allow tentative bond assignments.