Polypropylene (PP) plates have been modified with two different hydrophilic polymeric
materials, poly(N,N-dimethylacrylamide) (poly(DMAAm)) and poly(poly(ethylene glycol)methacrylate)
(poly(PEGMA)) in order to reduce insulin adsorption when the plates were exposed to insulin
aspart (AspB28 insulin). The influence of surface modification on the chemical and physical stability of
AspB28 insulin was evaluated by two chromatographic methods, size exclusion chromatography (SEC)
and reverse phase high pressure liquid chromatography (RP-HPLC) and the Thioflavin T assay. A
clear difference in the stability of AspB28 insulin was observed between the three tested surfaces. PP coated with
poly(DMAAm) resulted in a poor chemical stability and a significantly improved physical stability compared with unmodified
PP. In addition to this a lower phenol concentration was observed for the poly(DMAAm) coating. The results
from the poly(PEGMA) coating looked very promising with respect to the stability of AspB28 insulin in comparison with
the data from unmodified PP and the poly(DMAAm) coating. Two hydrophilic coatings have been tested and surprisingly
a difference in AspB28 insulin stability was observed. Therefore, AspB28 insulin adsorption and stability will be influenced
by more than the hydrophilicity of the surface.
Keywords: Chemical stability, hydrophilic coating, insulin fibrillation, physical stability, surface initiated polymerization.
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