Supercritical CO2-assisted preparation of ibuprofen loaded PEG-PVP complexes

Abstract

Stoichiometric ratios of poly (ethylene glycol) (PEG, Mw = 400) with poly(vinylpyrrolidone) (PVP, Mw = ±3.1 x 104 & Mw = 1.25 x 106 Mw) were prepared from ethanol cast solutions and in supercritical CO2. The complex formation was studied via glass transition (Tg) analysis obtained from differential scanning calorimetry (DSC) thermograms. PEG-PVP blends were also loaded with ibuprofen. The molecular dispersion of ibuprofen, mechanism of interaction, the effect of CO2 pressure and temperature and ageing of blends were also analysed with DSC, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and Xray diffraction. Tg analysis indicated that supercritical CO2 can facilitate the formation of stoichiometric PEG-PVP complexes. Processing of PEG-PVP blends with ibuprofen results in the molecular dispersion of ibuprofen mainly bonded to PVP carbonyl groups, without significant disruption of the PEG-PVP complex. Increasing ibuprofen content leads to the disruption of PEG-PVP H-bond interactions and subsequently a breakdown of the PEG-PVP complex. Increasing process pressure results in extraction of some PEG fractions, while temperature increase only leads to increased foaming. Post-processing ATR-FTIR shifts in ibuprofen-PEG-PVP complexes is greater with supercritical CO2 processing. These shifts are mainly attributed to atmospheric moisture absorption, however some evidence of molecular rearrangement is also observed. Altogether, ibuprofen-loaded PEG-PVP complexes can be prepared from supercritical CO2 processing showing similar characteristics to such complexes prepared from solution casting.