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

Stoichiometric ratios of poly(ethylene glycol) (PEG, M_w = 400) with poly(vinylpyrrolidone) (PVP, M_w = ±3.1 × 10⁴ and M_w = 1.25 × 10⁶ M_w) were prepared from ethanol cast solutions and in supercritical CO₂. The complex formation was studied via glass transition (T_g) 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 X-ray diffraction (XRD). T_g 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 process pressure results in extraction of some PEG fractions. 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. Overall it was shown that, ibuprofen-loaded PEG-PVP complexes can be prepared from supercritical CO₂ processing showing similar characteristics to such complexes prepared from solution casting.