Document Type

Thesis - University Access Only

Award Date

2008

Degree Name

Master of Science (MS)

Department / School

Chemistry and Biochemistry

Abstract

Chitosan, derived from the exoskeleton of naturally occurring chitin, is known for its wound bonding and healing capabilities. Chitosan is a good component for ophthalmologic purposes due to its optical clarity, mechanical stability, gas permeability (particularly towards oxygen), wettability, and immunological compatibility. pH changes are central to the curing of the chitosan based adhesives. This study was designed to determine the pH profile, with respect to time, in the eye using common fluorescent pH dyes. Fluorescein isothiocyanate (FITC) was covalently attached to chitosan and excited at 450 nm and at 490 nm with emission obtained at 520 nm. Ratiometric intensities were variable and a shift in two pKa units was observed. It is believed that the attraction between the free amines of chitosan and the hydroxyl groups of FITC are causing this shift in pKa, Oregon Green 514 (450/490ex, 530em), appealing due to the addition of electron withdrawing fluorines and its slightly larger size, also showed a two unit shift in pK3 . Larger probes, with possible shielding, were studied to improve pH measurement capabilities. Seminaphthorhodafluor (SNARF)-1 (514ex, 580/640em), when covalently attached to bovine serum albumin (BSA) prior to covalent attachment with chitosan, proved to be slightly more promising than FITC and Oregon Green 514 but still showed a one unit shift in pKa. BCECF [2', 7' - Bis (2- Carboxyethyl)- 5- (and 6) - Carboxyfluorescein] (440/490ex, 535em), a common physiological pH dye, showed the largest change in pKa with a 5 unit shift. It appears to be that the more hydroxyl groups available for deprotonation, the greater the shift in pKa. To help overcome this issue, FITC microspheres (450/490ex, 520em) were covalently attached to chitosan and showed much improvement with a minor shift of 0.1 in pKa. This may be overcome with a rougher surfaced microsphere.

Library of Congress Subject Headings

Chitosan

Eye -- Wounds and injuries -- Treatment

Wound healing

Dyes and dyeing

Format

application/pdf

Number of Pages

69

Publisher

South Dakota State University

Download

Share

COinS