Water-Soluble β-cyclodextrin Polymers as Drug Carriers to Improve Solubility, Thermal Stability and Controlled Release of Nifedipine

Abstract

Two types of water-soluble β-cyclodextrin polymers (β-CD-ECH polymer) were prepared by polymerization of β-cyclodextrin (β-CD) using epichlorohydrin (ECH) as cross-linking agent under basic conditions. These polymers contain 34% and 49% β-CD in structure and their solubilities in water are 563 and 875 g/1000 mL, respectively. The obtained polymers were characterized by DSC, DDSC, TGA, DTG and FT-IR spectroscopy techniques. The drug loading capacities of β-CD-ECH polymer matrices have been evaluated for nifedipine (NIF), which is a poorly water-soluble and highly photosensitive drug. Phase solubility studies showed complexation constants of 145.55 and 198.06 M^–1. In addition, supplementary data from solubility tests demonstrated that solubility of NIF in water was greatly increased through complexation with β-CD-ECH polymer. So, thermal stability of the polymer-encapsulated NIF was considerably improved owing to inclusion complexation with β-CD-ECH polymer. The results of in vitro release studies confirmed that NIF release from β-CD-ECH polymer was pH-dependent. Mathematical modeling using Higuchi and Korsmeyer – Peppas equations suggested Fickian diffusion as the mechanism of NIF release.