title: Effect of Moisture on the Thermoresponsive Properties of Binary Mixtures of Monoglycerides for Triggerable Drug Delivery Systems.
abstract: The crystallization behavior and temperature-dependent phase transition of monoglycerides have been utilized to develop thermal-sensitive drug delivery systems. The presence of excess water has been reported to influence the phase transition. The present study investigates the effect of moisture on the thermal behavior of binary blends of monoglycerides. Various compositions (0-100 wt%) of glyceryl monooleate (GMO) and glyceryl monostearate (GMS) were prepared by fusion method, and exposed to varying relative humidity (RH) levels (0-100%). The moisture uptakes, sorption isotherm, and the thermal behavior of GMO-GMS samples were analyzed using differential scanning calorimeter (DSC), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The in vitro nifedipine (NF) release was studied at 37 and 42°C. Samples of GMO-GMS (25:75, 50:50, and 75:25 wt%) stored at 97%RH at 25°C for 3 weeks increased in weight by 14.0, 14.7, and 15.8%, respectively. Despite such high moisture uptake, the GMO-GMS matrices maintained crystalline structure. The melting point (Tm) and heat of fusion (ΔHf) of the samples were reduced as the amount of moisture in the matrices increased. However, the heat of fusion calculated on dry basis remained constant at 139.4 ± 1.25, 102.7 ± 1.14, and 46.7 ± 1.16 J/g for GMO-GMS 25:75, 50:50, and 75:25 wt%, respectively. The comparison of the XRD measurements of the dry samples with those containing 30% water confirmed the preserved crystalline arrangement in the matrices. This study indicates that despite the high moisture uptakes, the GMO-GMS matrices retained their crystalline properties and provided temperature-dependent drug release indicating the potential application for thermoresponsive local drug delivery systems.
authors.affiliation: College of Pharmacy and Health Sciences, Drake University, Des Moines, Iowa, 50311, USA.
authors.forename: Hannah D
authors.initials: HD
authors.lastname: Stonewall
authors.affiliation: College of Pharmacy and Health Sciences, Drake University, Des Moines, Iowa, 50311, USA.
authors.forename: Haley M
authors.initials: HM
authors.lastname: Kessinger
authors.affiliation: College of Pharmacy and Health Sciences, Drake University, Des Moines, Iowa, 50311, USA. abebe.mengesha@drake.edu.
authors.forename: Abebe E
authors.initials: AE
authors.lastname: Mengesha
mesh_terms: D003460:Crystallization; D016503:Drug Delivery Systems; D065546:Drug Liberation; D050178:Monoglycerides / Q000737:chemistry*; D009543:Nifedipine / Q000737:chemistry; D044367:Phase Transition; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D050178:Monoglycerides; D014867:Water; D009543:Nifedipine
keywords: differential scanning calorimeter; monoglycerides; relative humidity; thermoresponsive; x-ray diffraction