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.