Effect of radio‐opaque filler on biodegradable stent properties

The effect of the addition of a radio‐opaque filler, barium sulfate (BaSO 4 ), on the mechanical properties of a biodegradable amorphous polymer film (poly‐lactic‐co‐glycolic acid, PLGA) was studied, as a function of degradation. With up to about 18% loading (v/v), the modulus of the filled polymer increases; beyond this concentration, agglomerates are formed. The filled systems are also radio‐opaque, over a thickness range of 0.07–0.19 mm in stent form (helicoidal). These stents were then immersed in phosphate buffer pH 7.4 at 37 o C for 2 weeks. The radial strength of stent was measured by using a compression test. It was found that filler‐loaded stent (FS) increased in radial strength by about 4 times (14.95 ± 1.20 N/mm) compared to the unfilled stent (UFS). However, both samples lost radial strength as the polymer degraded in buffer, but FS retained 60% (9.05 ± 0.07 N/mm) of its strength after 2 weeks whereas only 36% (1.39 ± 1.04 N/mm) was retained for UFS. Moreover, UFS lost its helical shape after 3 weeks. The findings have implications for optimization of degradable stent formulations. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006