Studies on the Adsorption and Thermodynamics of Theophylline, Vitamin C and Bovine Serum Albumin on Microporous Corn Starch

Abstract

As a good controlled‐release and sustained‐release adsorption material, microporous starch is likely to become a potential drug carrier with broad market prospects. In this work, the adsorption of three model drugs, theophylline, vitamin C, and bovine serum albumin (BSA), is studied and compared by measuring their adsorption onto raw corn starch, microporous corn starch alone, and microporous corn starch in the presence of 0.015% (g L−1) xanthan gum along with the corresponding thermodynamic data. The results shows that microporous corn starch in the presence of 0.015% xanthan gum is a good drug carrier and that the static saturation adsorption capacities of theophylline, vitamin C, and BSA were 183.1 × 10−3, 292.5 × 10−3, and 0.322 × 10−3 (mol g−1), respectively. These values are approximately two and four times those on microporous corn starch alone and raw corn starch, respectively. All the adsorption data of the three drugs onto corn starch mixtures can be well described by the Langmuir adsorption equation. Additionally, although the adsorption processes of theophylline, vitamin C and BSA are all spontaneous and exothermic, the first two processes are mainly driven by an enthalpy change, while the latter process is mainly driven by an entropy change. The in vitro release of drugs from microporous corn starch is initially rapid, and then, the release mechanism slowed. This work provides useful information regarding the use of microporous corn starch as a novel controlled‐release and sustained‐release drug carrier.