(302a) Probe Diffusion in Poly(ethylene glycol)-Based Hydrogels Studied by Fluorescence Correlation Spectroscopy

Hydrogels are widely studied due, in large part, to their similarity to biological components.  These materials are composed of hydrophilic polymer network and are capable of taking up large quantities of water.  While the majority of hydrogel-related research has revolved around tissue engineering and drug delivery, a relatively small amount of work has focused on using hydrogels to mimic biological barriers, such as mucus, which covers the surface of a variety of organs inside the body.  In this study, we investigate the use of hydrogels as diffusive barriers to small molecules and examine key parameters in the synthesis that affect the mobility of a fluorescent probe.  Additionally, we assess the ability of these materials to serve as a novel in vitro model for studying transport of small molecules in biological hydrogels such as mucus.  Poly(ethylene glycol) (PEG) hydrogels were prepared through chemically initiated radical polymerization with ammonium persulfate (APS) and tetramethylethylenediamine (TEMED).  Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy was used to confirm the hydrogel composition and to determine the extent of conversion.  Swelling studies were performed in order to calculate the swelling ratio, Q, as well as the theoretical mesh size .  Hydrogels were imbibed with fluorescent probe particles and fluorescence correlation spectroscopy (FCS) was used to study the hindered transport within these gels.  The crosslinking density, molecular weight of crosslinker, and water content during synthesis were all examined for their influence on the mobility of the probe molecule within the hydrogel.  While the mucus barrier is essential in preventing viruses and bacteria from entering our tissues; it also poses a perennial problem for drug delivery, highlighting a significant need for the development of a synthetic in vitro model system to study hindered transport.