The interplay between the rate of release from polymer grafted liposomes and their fractal morphology

The purposes of this study were to investigate the indomethacin (IND) release profile from dipalmytolphosphatidylcholine:poly(2-methyl-2-oxazoline)-grad-poly(2-phenyl-2-oxazoline (DPPC:MPOx) (in different molar ratios) mixed liposomal nanovectors, to examine the relevance of power law using these experimental release data, and to detect the relationship of the fractal dimension (df) of nanovectors with the fraction of the IND release. The df of the mixed liposomes was determined by Static Light Scattering during the release of IND from the nanocontainers. It is observed that the in vitro release of the drug from the prepared nanostructures is quite fast especially for the nanovectors prepared with the lower ratio of MPOx. The release kinetics was studied by regression analysis of drug concentrations in fractal matrices with respect to time. A power law, a piece-wise power law functions and Weibull distribution were fitted to the release data and the model parameters were estimated. Good fits were observed in all datasets analyzed, while distinct regions of different release rates corresponding to different df values were described. The authors proposed that the fractal morphology of the mixed liposomes affects the drug release and must be taken into account to develop liposomal drug with complete knowledge of their structural properties.