The aim of this study was to prepare and characterize a novel type of starch-coated microparticles (MPs) allowing site-specific delivery of bioactives to the colon. An oral colon-specific controlled-release system was developed in the form of MPs coated with a resistant starch (RS2/RS3) film (RS@MPs) through an aqueous suspension coating process. The RS2 was chosen from a high-amylose cornstarch with 88.5% digestion resistibility. The RS3 was prepared by a high-temperature/pressure (HTP) treatment, with the following of enzymatic debranching, and retrogradation, resulting in a dramatic increase in enzymatic resistance (RS3 content: 76.6%). RS@MPs showed 40.7% of 5-aminosalicylic acid release within 8 h. The in vivo study of fluorescein-loaded RS@MPs indicated the high acidic and enzymatic resistibility of RS@MPs and a restrained release in the upper GIT. Therefore, RS@MPs has revealed to be a high potential system for accurately targeting bioactive compound delivery to the colon.

Highlights

• Film-coated microparticles were developed for colon-specific drug delivery.
• Starch-coated films showed improved acidic and enzymatic resistance in the GI tract.
• Native and retrograded starches were used as binders to reinforce the resistance.
• Suitable molecular mass and high crystallinity of starch are important factors

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