Preparation and characterization of pullulanase debranched starches and their properties for drug controlled-release

Abstract

Debranched starches (DBSs) with different degrees of debranching (low, L-DBS; moderate, M-DBS; high, H-DBS) were prepared and investigated. After pullulanase modification, the starch granules became more porous and many small particles containing short glucan chains were generated. DBSs adopt a single-helical V-type crystalline structure with low crystallinity. L-DBS samples contained fewer (20.70%) and longer (degree of polymerization, DP: 21.92) linear short glucan chains than their counterparts (M-DBS: 40.92%, 20.05 DP; H-DBS: 55.52%, 18.52 DP). Pullulanase enzymatic hydrolyzate for DBS samples with higher degrees of debranching inclined towards retrogradation at 20 °C. DBSs with higher degrees of debranching could form a hydrogel with higher G′ and G′′ values, indicating these samples formed a stronger gel network. L-DBS could hold more water and its digestibility was higher. The in vitro test showed that DBS is a good candidate to control drug release for over 12 h. Furthermore, the drug release profiles from both DBS-based and HPMC-based tablets showed an anomalous transport mechanism. The drug release from these four matrices was controlled by a combination of drug diffusion and matrix erosion. The drug release properties from DBS-based tablets were considerably influenced by the degree of debranching. The in vitro drug release profile of M-DBS was similar to that of HPMC (f₂ = 60.75), while L-DBS and H-DBS differed from HPMC (f₂ < 50). In summary, DBS is a good hydrogel candidate, and it can be used as an excipient in oral tablets to control drug release.