RELEASE OF PROTEIN FROM A POLY(ORTHO ESTER) FILM DURING SURFACE EROSION STUDIED BY IN-SITU ATOMIC-FORCE MICROSCOPY

Insitu atomic force microscopy has recorded the dynamic topographic ch anges occurring as a biodegradable polymer film, containing the protei n bovine serum albumin (BSA), is eroded. An atomic force microscope (A FM) was operated with the scanning probe immersed in an aqueous soluti on allowing the surface morphology of these samples to be analyzed at the polymer/water interface. Control experiments demonstrated that the granular structure of the poly(ortho ester) surface was roughened by the degradation process. The loss of protein particles embedded in a p olymer film was then followed using the AFM. Analysis of the kinetics of the erosion process was undertaken using computational analysis of the three-dimensional AFM data, which enables volume changes occurring during the erosion to be quantified. These methods of volume analysis allow the comparative rates of protein and polymer loss from the erod ing polymer surface to be assessed. This data has implications for the design of surface-eroding controlled drug delivery devices and sugges ts a role for in situ atomic force microscopy in the comprehension of the relationship between polymer biodegradation and protein release.