24 Polycaprolactone (PCL) is a widely used biodegradable polyester for tissue engineering applications when 25 long-term degradation is preferred. In this article, we focused on the analysis of the hydrolytic degradation of 26 virgin and bioactive poly(sodium styrene sulfonate) (pNaSS) functionalized PCL surfaces under simulated 27 physiological conditions (phosphate buffer saline at 25°C and 37°C) for up to 120 weeks with the aim of 28 applying bioactive PCL for ligament tissue engineering. Techniques used to characterize the bulk and surface 29 degradation indicated that PCL was hydrolyzed by a bulk degradation mode with an accelerated degradation-30 three times increased rate constant-for pNaSS grafted PCL at 37°C when compared to virgin PCL at 25°C. 31 The observed degradation mechanism is due to the pNaSS grafting process (oxidation, radical polymerization) 32 which accelerated the degradation until 48 weeks, when a steady state is reached. The PCL surface was altered 33 by the pNaSS grafting, introducing hydrophilic sulfonate groups that increase the swelling and smoothing of 34 the surface, which facilitated the degradation. After 48 weeks, pNaSS was largely removed from surface and 35 the degradation of virgin and pNaSS grafted surfaces were similar. The cell response of primary fibroblast 36 cells from sheep ligament were consistent with the surface analysis results: a better initial spreading of cells 37 on pNaSS surfaces when compared to virgin surfaces and a tendency to become similar with degradation time. 38 It is worthy to note that during the extended degradation process the surfaces were able to continue inducing 39 better cell spreading plus preserve their cell phenotype as shown by collagen genes expressions. 40 41