Correlation of two bioadhesion assays: the everted sac technique and the CAHN microbalance.

This contribution correlates two in vitro methods utilized to determine bioadhesion. One method, the everted intestinal sac technique, is a passive test for bioadhesion involving several polymer microspheres and a section of everted intestinal tissue. The other method, the CAHN microbalance, employs a CAHN dynamic contact angle analyzer with modified software to record the tensile forces measured as a single polymer microsphere is pulled from intestinal tissue. This study demonstrates that CAHN and everted sac experiments yield similar results when used to quantify the bioadhesive nature of polymer microsphere systems. A polymer showing high adhesion in one method also demonstrates high bioadhesion in the other method; polymers that exhibit high fracture strength and tensile work measurements with the CAHN microbalance also yield high binding percentages with the everted sac method. The polymers tested and reported here are poly(caprolactone) and different copolymer ratios of poly(fumaric-co-sebacic anhydride). The results of this correlation demonstrate that each method alone is a valuable indicator of bioadhesion.

Poly(fumaric-co-sebacic anhydride). A degradation study as evaluated by FTIR, DSC, GPC and X-ray diffraction.

The degradation of three poly(fumaric-co-sebacic anhydride) [P(FA:SA)] copolymers is examined in a composition of microspheres made by the hot melt encapsulation process. The emergence of low molecular weight oligomers occurs during degradation of the copolymer microspheres, as evidenced by a variety of characterization methods. Characterization was conducted to determine the extent of degradation of the polyanhydride microspheres using Fourier-transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and X-ray diffraction. It is demonstrated that degradation of P(FA:SA) is greatly accelerated at basic pH, yet there is little difference between degradation in neutral and acidic buffers. A good correlation exists between the results of each characterization method, which allows a better understanding of the degradation process and the resulting formation of low molecular weight oligomers in poly(fumaric-co-sebacic anhydride).