Therapeutic Ultrasound for Ocular Delivery of Macromolecules

Macromolecules have been shown effective in vision-saving treatments for various ocular diseases such as age-related macular degeneration and diabetic retinopathy. Current delivery of macromolecules requires frequent intraocular injections and carries a risk of serious adverse effects. We aimed to develop a non-invasive method for macromolecule delivery into the cornea and sclera using therapeutic ultrasound. In vitro corneas exposed to a small Ultra-Red Fluorescent Protein (smURFP), with a molecular weight of 32 kDa, were treated with continuous ultrasound at frequencies of 400 or 600 kHz with intensities of 1.0 or 0.8 W/cm2, respectively, for five minutes or sham treated with no ultrasound, as a control. Fluorescence imaging of cornea sections verified the delivery of macromolecules into individual epithelial cells. Forty percent of the sections exposed to smURFP (MW: 32 kDa) solution showed fluorescent delivery into the epithelium with ultrasound and lacked delivery without ultrasound. The safety of ultrasound application was studied through histology analysis which indicated that ultrasound caused no significant corneal damage. The absorbance measurements indicated negligible presence of smURFP macromolecules in the receiver compartment in both sham and ultrasound treatment groups, and smURFP does not cross the entire depth of the cornea in these experiments. Therapeutic ultrasound shows feasibility as a minimally-invasive method for macromolecule delivery to treat various corneal diseases. We have also tested the application of therapeutic ultrasound as a minimally-invasive approach for delivery of Avastin into diseased regions of the eye. Bevacizumab (Avastin), is an anti-VEGF antibody with molecular weight of 149 kDa. We tested the effectiveness and safety of Avastin delivery through the rabbit sclera in vitro using standard diffusion cells model. 400 kHz or 3 MHz ultrasound at an intensity of 1.0 W/cm2 was applied for the first 5 minutes of one-hour Avastin drug exposure. Sham treatments mimicked the ultrasound treatments, but ultrasound was not turned on. Diffusion cell receiver compartments absorbance values were 0.015 0.006 (n = 15) and 0.014 0.006 (n = 13) for 400 kHz ultrasound group and matched sham group, respectively with no statistical difference. However, the absorbance values were statistically significant (p < 0.01) for 3 MHz ultrasound group of 0.004 0.0019 (n = 8) and matched sham group of 0.002 0.0005 (n = 7). There is 2.3 times increase in drug delivery in the 3 MHz ultrasound group when compared to its sham group. Histology studies and gross observation indicated no significant damage in ultrasound-treated scleras of the 400 kHz and 3 MHz ultrasound group. Our results indicated that therapeutic ultrasound at parameters of 3 MHz and 1.0 W/cm2 may be effective in the delivery of Avastin through the sclera. Further, whole eye studies with FITC-dextrans of different sizes (40, 70, 150 kDa) were performed using 3 MHz ultrasound at 1.0 W/cm2 for 5 minutes. 3 MHz ultrasound application enhanced 150 kDa FITC-dextran delivery through the sclera (p < 0.05), while no significant enhancement was observed for 70 and 40 kDa FITC-dextrans. There is 1.5 times increase in 150 kDa FITC-dextran drug delivery in the 3 MHz ultrasound group when compared to its sham group. These findings could open the door for the development of a new minimally-invasive approach for treatment of retinopathies and other vision-threatening diseases. Modeling of temperature increase in the different eye tissues was also studied to determine the safety of ultrasound application. The study modeled the ultrasound effects and thermal loss in a human eye using ultrasound parameters used in our in vitro and ex vivo ocular studies. The proposed ultrasound parameters appear safe and are below the threshold of functional changes in the eye tissues.  

Author

• Almogbil, Hanaa

Language

• en

Date created

• 2022

Type of Work

• Dissertation

License

• All rights reserved

Rights statement

• In Copyright

GW Unit

• Biomedical Engineering

Degree

• Ph.D.

Advisor

• Zderic, Vesna

Committee Member(s)

• Papa, Anne-Laure
• Zhang, Lijie Grace
• Nasarallah, Fadi P.
• Li, Zhenyu

Persistent URL

•  https://scholarspace.library.gwu.edu/etd/2r36tz34g