Current techniques in the field of targeted drug delivery fail to overcome a major barrier in modern medicine – circumvention of the blood-brain barrier. One facet of drug delivery that has not been extensively explored for this application but is known to impact cellular uptake of nanoparticles is modulation of nanoparticle shape. Although previous work has demonstrated the impact of elongated solid nanoparticles on increasing uptake efficiency, drug encapsulation in membrane bound nanoparticles is most attractive, as the polymer composition enables a high degree of tunable properties including release triggers, surface properties, shape, and size. Here, we develop an understanding of the effect of hydrophobicity on bending energies, developing design rules for making prolates of various aspect ratios. The specific aims of this study are to 1) evaluate the effect of varying hydrophobicity on prolate polymersome formation and shape maintenance, 2) determine the effect of osmotic pressure on prolate aspect ratio by varying salts and solvents.
The Blood-Brain Barrier remains a challenge to cross, stunting the development of treatments for brain diseases. Some potential methods have been developed, including microbubble or osmotic diuretic-induced transient barrier disruption. However, they prove to be invasive or have some adverse side effects. The novel method we are developing is a noninvasive approach to cross the blood-brain barrier and deliver a payload of drugs. We propose that through changing the shape of a polymersome, a polymeric nano-vesicle, to create more surface area, a greater amount will be able to be taken up by the endothelial cells and thus be delivered to the brain. Up to this point, our lab has observed a shape change of polymersomes into prolates using one specific block-copolylmer. The shape change was driven by a salt gradient to create an osmotic pressure outside of the formed polymersome, bending the polymersome into a prolate. The research will continue by using increasing concentrations of salt gradients to discern whether we can further increase the surface area of the prolate. We will also research whether we can turn other materials, that have beneficial applications in treatment, into prolates.
Completion of this project will help advance the entire field of drug delivery, by providing a novel way to delivery drugs to the brain. It would prove to be less invasive than methods currently in use, including the use of osmotic diuretics to temporarily open the blood-brain barrier which can put the patient at risk of blood borne pathogens entering the brain. The advancement in research would help change the lives of millions of people suffering from brain illnesses. Not only that, but it would help advance medical science to overcome the blood-brain barrier using a tunable and widely applicable method. Although this proposal only explores the use of biodegradable polyesters, polymersomes can be formed by polymers that respond to many other relevant biologic stimuli, including temperature, enzymes, and hypoxia.
The first objective is to investigate salt concentrations to create prolates from polymersomes of other polymeric materials. We will explore co-polymers other than polyethylene glycol-b-polylactic acid (PEG-PLA), focusing our efforts on biodegradable polyesters including PEG-b-poly(lactic-co-glycolic) acid (PLGA) and PEG-b-polycaprolactone (PCL).
1.The particles will be prepared by dissolving them in DMSO then syringe injecting them into a 2% mannitol solution.
2.The nanoparticles will then be “washed” by dialyzing them against water to dispel extra solvent.
3.Then, particles will be dialyzed against a NaCl solution of increasing concentration (beginning at 50mM).
4.After this is done, the polymersomes polydispersity index (PDI) and size will be measured using DLS. A PDI of greater than 0.1, is a strong indication that prolates have likely formed. This will be confirmed with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). We will measure length and diameter of formed prolates to determine aspect ratios.
5.Then the second objective is to see the varying salt concentration will elongate the prolates. The salt concentration was varied from 50mM, 100mM, and 200mM. This is to see if we can increase the aspect ratio of the prolates.
PEG-PLA “PDI v.s Concentration”
PEG-PLGA “PDI V.S Concentration”
SEM and TEM scan of nanoparticle
Data from DLS
The desired results are that we can prolate the different materials. The other anticipated result would be that we are able to increase the aspect ratio as well as find the optimum compound used for increasing the aspect ratio.
- May be a correlation between shape changing and material
- hydrophobic more likely to prolate
- PEG-PLA seems to be less likely to prolate consistently
- PEG-PLGA more likely to prolate consistently
- more testing needed for optimum material
- more data needed to be analyzed to find if aspect ratio increased.
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