Graduation Year

2007

Document Type

Thesis

Degree

M.S.M.E.

Degree Granting Department

Mechanical Engineering

Keywords

Dexamethasone, Dexamethasone 21-phosphate, Diffusion coefficient, Mathematical model, Polylactic-co-glycolic acid (PLGA)

Abstract

Dexamethasone and dexamethasone 21-phosphate were loaded into NDGA-polymerized collagen fibers and release rate studies were performed to calculate their diffusion coefficients. Dexamethasone loaded fibers were placed in a PBS solution for specified time intervals (1, 3, 6, 7, 12, 24, 30, and 48 hours) after which the eluant was removed and analyzed by capillary zone electrophoresis (CZE). CZE is a tool that can be utilized for quantitative analysis of chemical compounds. This data was incorporated into mathematical models to determine the diffusion coefficient. The diffusion coefficient (D) for dexamethasone in NDGA-polymerized collagen fibers is D = 1.86 x 10⁻¹⁴ m²/s. Similarly, dexamethasone 21-phosphate loaded fibers were placed into a PBS solution and analyzed using CZE at these specified intervals (15, 30, 45, 60, and 75 minutes). Applying this data to the mathematical model provided a diffusion coefficient for dexamethasone 21-phosphate in NDGA-polymerized collagen fibers of D = 2.36 x 10⁻¹³ m²/s. In an effort to control drug delivery from these fibers a polylactic-co-glycolic acid (PLGA) coating was applied to the fibers. This coating helped sustain delivery of dexamethasone 21-phosphate for over a 100 day period. CZE experiments were again conducted in conjunction with another mathematical model to characterize release. A semi steady-state diffusion coefficient was estimated to be D = 4.59 x 10⁻¹⁴ m²/s.

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