BME PhD Dissertation Defense - Stefan Yohe

Starts:
2:00 pm on Tuesday, November 27, 2012
Ends:
4:00 pm on Tuesday, November 27, 2012
Location:
44 Cummington St, Room 203
Committee:
Mark Grinstaff (Advisor)
Muhammad Zaman (Chair)
Joe Tien
Carol Walsh
Yolonda Colson (BWH)

Title: Superhydrophobic Materials for Drug Delivery

Abstract:
Superhydrophobicity is a property of material surfaces reflecting the ability to maintain air at the solid-liquid interface when in contact with water. These surfaces have characteristically high apparent contact angles, by definition exceeding 150, as a result of the composite material-air surface formed under an applied water droplet. Superhydrophobic surfaces were first discovered on naturally occurring substrates, and have subsequently been fabricated in the last several decades to harness these favorable surface properties for a number of emerging applications, including their use in biomedical settings.
This work describes fabrication and use of 3D superhydrophobic materials. So called 3D superhydrophobicity is distinct from 2D superhydrophobicity in that air is maintained not just at the surface of the material, but also within the bulk. This allows water to infiltrate more slowly and continuously to form a new water-air-material interface as water penetrates into the material, and affords the use of 3D superhydrophobic materials for applications distinct from those currently being considered for simple 2D superhydrophobic surfaces.
We demonstrate the utility of 3D superhydrophobicity as a method for drug delivery. Drug delivery devices are fabricated using the electrospinning technique, and the stability of the entrapped air layer within the superhydrophobic structure is tuned to affect wetting/air displacement to control the rate of drug release. Air controls the rate of drug release both in in vitro release studies and cytotoxicity assays. The wetting rates of 3D superhydrophobic can be directly measured, and a number of physio-chemical techniques are used to probe the stability of the air layer.
After determining that air could be used to control the rate of drug release, 3D superhydrophobic meshes are explored for three applications: first, as a combination reinforcement-drug delivery device for use in resectable colorectal cancer; second, as a device for triggered drug release using the pressure generated from high-intensity focused ultrasound to remove the entrapped air layer; and third, as a biocompatible surface coating on chemically distinct material surfaces. Overall, the use of 3D superhydrophobicity as a method to control drug release rate offers an entirely new strategy for drug delivery, and is promising for the applications considered in this work as well as many others.