Membrane Permeability and Stability of Liposomes Suspended in Shear Flow

Biomaterial strategies for improved intra-articular drug delivery

Osteoarthritis (OA) is a joint degenerative disease that has become one of the leading causes of disability in the world. It is estimated that OA affects 50 million adults in the United States. Currently, there are no FDA-approved treatments that slow OA progression and its treatment is limited to pain management strategies and life style changes. Despite the discovery of several disease-modifying OA drugs (DMOADs) and promising results in preclinical studies, their clinical translation has been significantly limited because of poor intra-articular (IA) bioavailability and challenges in delivering these compounds to tissues of interest within the joint. Here, we review current OA treatments and their effectiveness at reducing joint pain, as well as novel targets for OA treatment and the challenges related to their clinical translation. Moreover, we discuss intra-articular (IA) drug delivery as a promising route of administration, describe its inherent challenges, and review recent advances in biomaterial-based IA drug delivery for OA treatment. Finally, we highlight the potential of tissue targeting in the development of effective IA drug delivery systems.

Rapid leakage from PEGylated liposomes triggered by bubbles

Liposomes are applicable to fabrication of colloidal carriers of drugs and proteins. Physicochemical stimuli-triggered leakage from liposomes offers a wide variety of applications in biochemical and biomedical fields. In this work, effects of bubbles on the characteristics of PEGylated liposomes encapsulating 5(6)-carboxyfluorescein were examined. The liposomes were composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1-10 mol% 1,2-distearoyl-sn-glycero-3-phosphoethanolamine conjugated with poly(ethylene glycol) (DSPE-PEG). The mean molecular mass M_r,PEG of the PEG moiety was 550 or 5000. A bubble column was used for generating air bubbles at a superficial gas velocity of 0.58-0.88 cm s^-1. Leakage from the PEGylated liposomes was remarkably accelerated at 25 or 40 °C by introducing air to a liposome suspension at pH 7.4, whereas the dye molecules practically remained encapsulated in the liposomes being suspended in static liquid. The apparent rate constant for the dye release from the liposomes composed of DOPC and 1 mol% DSPE-PEG (M_r,PEG = 5000) being suspended in the gas-liquid flow was 168 times larger than that obtained with respect to the same liposomes in static liquid. Leakage from non-PEGylated liposomes was not pronounced even in the gas-liquid flow. Furthermore, the release rate of the dye from the PEGylated liposomes in liquid shear flow (no bubble) was clearly smaller than that in the gas-liquid flow, meaning that the interaction between bubbles and the liposomes was responsible for the observed rapid leakage. Adsorption of the PEGylated lipids to bubbles was indicated to induce leaky lipid bilayers, which was discussed on the basis of the conformational state of the PEG moiety.

Octadecyl ferulate behavior in 1,2-Dioleoylphosphocholine liposomes

Octadecyl ferulate was prepared using solid acid catalyst, monitored using Supercritical Fluid Chromatography and purified to a 42% yield. Differential scanning calorimetry measurements determined octadecyl ferulate to have melting/solidification phase transitions at 67 and 39°C, respectively. AFM imaging shows that 5-mol% present in a lipid bilayer induced domains to form. Phase behavior measurements confirmed that octadecyl ferulate increased transition temperature of phospholipids. Fluorescence measurements demonstrated that octadecyl ferulate stabilized liposomes against leakage, maintained antioxidant capacity within liposomes, and oriented such that the feruloyl moiety remained in the hydrophilic region of the bilayer. Molecular modeling calculation indicated that antioxidant activity was mostly influenced by interactions within the bilayer.