UV Imaging Studies on Pluronic F127-based Hydrogel Formulations of Ibuprofen

Purpose
The aim of the project was to prepare Pluronic F127 gel formulations containing ibuprofen and correlate their rheological and
drug release properties. The effects of variation of Pluronic F127 concentration (15%, 20% and 25%) and ibuprofen (1% and
5%) concentration were investigated.
Methods
Pluronic F127 gels containing 1% or 5% w/w ibuprofen were prepared on a weight basis using the cold method at 15%, 20%
and 25% w/w Pluronic concentrations. Propylene glycol was used as a co-solvent. Saturation concentration of ibuprofen in
each gel was determined using an Olympus BH2 microscope fitted with a camera (AxioCam MRc-Zeiss, UK) and
AxioVision vs4.4 software. Viscometry was performed at 32°C to characterise the flow behaviour of the gels, using a
sunblasted stainless steel cone-plate (4°/40 mm) with 150 µm gap size. UV Imaging of ibuprofen diffusion from the gels in
PBS buffer was examined using an Actipix SDI300 dissolution system at 214 nm.
Results
Polarised microscopy confirmed that gels (15%, 20% and 25%) containing 1% ibuprofen were unsaturated. The rate of
ibuprofen release from the gels was found to decrease in response to increasing gel viscosity as the polymer content increased
from 15 to 25% w/w.
The presence of crystals in the 5% w/w ibuprofen (15% w/w) gel indicated that ibuprofen was present above its solubility
limit within the gel matrix. The 5% w/w ibuprofen gel had higher viscosity compared to the 1% w/w ibuprofen (15% w/w)
gel, yet the rate of drug release from the 5% ibuprofen gel was higher when compared to the 1% ibuprofen gel. The effect of
supersaturation seemed to outweigh the effect of gel viscosity in terms of drug release.
Conclusion
Gels where ibuprofen was present below its solubility limit demonstrated a correlation between gel viscosity and drug
release, whereby an increase in gel viscosity retarded ibuprofen release from the gels.