The use of NMR spectroscopy to study the encapsulation of hydrophobic drugs by Rf-PEG (fluoroalkyl-ended poly(ethylene)glycol) hydrogels

ANYL 74

Errol V. Mathias, emathia@exchange.calstatela.edu1, Yong Ba, yba@calstatela.edu1, and Julia A. Kornfield, jak@cheme.caltech.edu2. (1) Department of Chemistry and Biochemistry, California State University, Los Angeles, 5151 State University Drive, Los Angeles, CA 90032, (2) Division of Chemistry and Chemical Engineering, California Institute of Technology, Mail Code 210-41, Pasadena, CA 91125
The encapsulation and micelle formation of Rf-PEG (fluoroalkyl-ended Poly(ethylene)glycol) hydrogels were studied by PFG (Pulse Field Gradient) diffusion NMR spectroscopy and 19F solid-state EXSY (EXchange SpectroscopY). Micellar size depends on the chain length of the fluoroalkyl and PEG groups. By estimating the size of these micelles and their encapsulation behavior we can thus predict the drug loading capabilities of the Rf-PEG hydrogels. The diffusion characteristics of an anticancer drug, 5-fluorouracil and its methylated analogue, dimethyl 5-fluorouracil were studied for this purpose. It was found that dimethyl 5-fluorouracil, being more hydrophobic, was completely encapsulated by the micelles. From the diffusion coefficient we can estimate the size of the core of the micelle. Dipolar interactions between the fluorine groups of the drug and the Rf-PEG's were evident from its EXSY spectrum proving complete encapsulation by the hydrogel. Our EXSY results also suggest that the hydrophobic drug continues to remain encapsulated even after drying the hydrogel, thus making Rf-PEG's good agents for drug delivery.
 

General Papers
7:00 PM-9:00 PM, Sunday, 10 September 2006 Moscone Center -- Hall D, Poster

Division of Analytical Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006