Session: Government Agency Student Posters

Paper Number: 173575

Broad Spectrum Rheology of Hydrogel-Based Contact Lenses for Drug Release 

Drug release via incorporation into contact lens material is viewed as a highly effective method to treat eye diseases. The aim of this study is to investigate the impact that rheological properties have on drug release profiles for contact lenses. A model contact lens material was created with 2-hydroxy ethyl methacrylate (HEMA) and methacryloxypropyltris (TRIS) crosslinked with ethylene glycol dimethacrylate (EGDMA) at various cure times to access a broad complex moduli range. The moduli range obtained using a combination of optical tweezers, dynamic light scattering, and laser speckle imaging were found to be: a) storage modulus  and loss modulus  for curing time of 30 s; b) storage modulus  and loss modulus  for curing time of 40 s and, c) Storage modulus  and Loss modulus  for curing time of 2 mins 30 s.  The rheological properties for the contact lens material was obtained by using intensity data to obtain a mean square displacement.  The Fourier transform of the mean square displacement was then used to obtain the complex moduli, form which storage and loss modulus could be determined.

 

Each technique examined here could access only a limited range depending on the properties of the contact lens material.  Optical tweezers are sensitive to changes in medium refractive index.  Curing times above 30 s promoted additional crosslinking, limiting this technique to materials cured below this cutoff time.  Dynamic light scattering can collect statistics from a larger number of particle ensembles, thus giving this technique the ability to access materials cured for up to 2 min 30 s.  Our experiments demonstrated that laser speckle imaging was the only technique able to exceed this limit, hence giving it the ability to access information for a broad range of moduli.  Using contact lens material drawn from across various stiffnesses, achieved by controlling cure time, we introduced fixed concentrations of 0.01 M Rhodamine B dye to measure the drug release profile over a 12-hour period for the curing time of 6 mins.  Overall, we demonstrated that three different techniques can be used to measure a broad range of viscoelastic properties for cross-linked polymers used in contact lenses. The viscoelastic spectra of the polymer composite obtained from each of the tools agree at all curing times. Our results yield insight into the relationship between viscoelastic properties and drug release profiles.  We expect that this study will help engineer burst release of drugs through step-by-step control of rheology of contact lens.

Presenting Author: Richa Ghosh Iowa State University

Presenting Author Biography: Richa Ghosh is a PhD student at Iowa State University working under the supervision of Prof. Sarah Bentil and Prof. Jaime Juarez. Her research focuses on optical spectroscopic measurements of viscoelastic materials.

Authors:

Richa Ghosh Iowa State University
Sarah Bentil Iowa State University
Jaime Juarez Iowa State University