Engineering better delivery systems for pharmaceutical drugs

Problem Title

Engineering better delivery systems for pharmaceutical drugs

Scientific Title

Understanding the membrane permeability of poly(phosphrylcholine cyclooctene) vesicles (PCVs)

Student: 
Dong Yeop Shin
Major(s): 
Chemical Engineering
iCons Concentration: 
Biomedicine/Biosystems
iCons Class Year: 
Class of 2014
Executive Summary 

Vesicles are extremely useful as carriers due to their ability to encapsulate hydrophilic molecules in the water-filled interior and hydrophobic materials in the membrane. Polymer vesicles, also known as polymersomes, are structurally similar to liposomes formed from lipids, but they take advantage of polymer chemistry for tunable membrane characteristics, such as mechanical stability and permeability. It is important to study the permeability of the vesicles to understand and control the release of cargo.

In this study, the permeability of poly(phosphorylcholine cyclooctene) vesicles (PCVs), formed from a polymer with hydrophilic phosphorylcholine grafts pendent to a hydrophobic backbone, compared with conventional diblock polymersomes, formed from poly(butadiene-block-ethylene oxide), was studied. Osmotic shock experiments were used to determine the permeability of the membranes to salt and fluorescence microscopy was used to determine the permeability of the membranes to a water-soluble dye, rhodamine B (RhB).

The results from the osmotic shock experiments showed that both types of vesicles are extremely resistant to osmotic shock, suggesting their permeability to salt. Rhodamine permeability assays showed that PCVs do not encapsulate RhB, whereas fluorescence microscopy of conventional vesicles clearly showed RhB inside the vesicles following dilution with water. Additionally, fluorescence microscopy experiments demonstrated the permeability of PCVs even to 6 kDa poly(methacryloyoxyethyl phosphorylcholine) (polyMPC) tagged with RhB. These findings show that, in comparison to conventional polymersomes, PCVs are extremely permeable. The large permeability difference between PCVs and polymersomes suggest that polymer chemistry can be used to design polymer vesicles with membrane permeability tunable over wide size ranges.

Problem Keywords: 
drug delivery
Scientific Keywords: 
fluorescence microscopy
osmotic shock experiments
polymersomes