Introduction/Materials & Methods (Kinetic Studies) By:Kristin Ackermann Amanda Rohs Blanca Skelding

Introduction  Biocompatible polymers permit the controlled release of macromolecules  EVAc Polymer systems have a wide variety of applications Chemotactic and growth factor release systems Informational macromolecules Delivery systems for insulin, interferon and antigens

Introduction  Mechanism for macromolecular release has not been explained  Polymers capable of releasing molecules larger than their permeability limit  Incorporating macromolecules into a non- porous matrix results in the formation of an interconnected pore network  Diffusion of molecules through network provides basis for controlled release

Method  BSA, β-lactoglobulin A and lysozyme powders sieved into specific size ranges  Dispersed in a 10% ethylene-vinyl acetate solution  Suspensions cast in flat glass mold at - 80 C  Sheets dried in two 48-hour stages (-20 C and under vaccum at 20 C)

Method  To test kinetics, 9 slabs were prepared: Dimensions: 1cm x 1cm x 1mm Coated on 5 faces using paraffin One 1cm x 1cm face exposed (allowing for diffusion on only one face) Stainless steel autoclips were pressed into the paraffin for anchors when placed in release medium

Method  Release medium Composed of 0.9% NaCl solution Placed in 10mL amounts in 20mL vials  Slabs removed at specified time points Slabs placed in vials containing fresh saline Old solutions were spectrophotometrically analyzed for protein content

Method  Protein particle densities determined using pycnometer with methylene chloride as solvent  Porosity was determined before and after release. Before: dividing protein concentration in slab by protein particle density After: liquid leaching of salicylate

Method  In general, porosity values before and after release agreed to within 5%  Thickness of polymer slabs was also measured using a micrometer  Standard deviation for thickness measurements was less than 4% for each slab