Amelioration of Blood Compatibility and Endothelialization of Polycaprolactone Substrates by Surface-Initiated Atom Transfer Radical Polymerization - Advances in Biomaterials Science and Biomedical Applications - page 196

normal range of the clinical reference, and no significant differences in the coagulant activi‐
ties were observed on the endothelialized PCL substrates as compared to the bare PCL sub‐
strates. The results also revealed that the ECs cultured on the pristine PCL and
functionalized PCL surfaces remained unactivated and did not exhibit procoagulation phe‐
notypes. Hence, it could be concluded that the presence of the monolayer of ECs had no ef‐
fect on the intrinsic or the extrinsic coagulation pathways.
3.5.3. Nitric Oxide (NO) production
Nitric oxide (NO) is an important regulator of vascular tone and platelet adhesion and the
continuous NO release by ECs prevents thrombogenesis [53]. In this study, the NO secretion
of the ECs on the pristine PCL and functionalized PCL surfaces were measured. As shown
in Fig. 12, the amount of NO secreted by ECs on the gelatin-immobilized PCL surfaces was
significantly higher than those on the pristine PCL, aminolyzed and P(GMA)-grafted PCL
surfaces. The amount of NO production of the ECs seeded on the PCL- g -P(GMA)2- c -gelatin
surface was around 2-fold higher than that on the PCL- g -P(GMA)1- c -gelatin surfaces, indi‐
cating that the improved NO production observed for ECs grown on the gelatin-immobi‐
lized PCL surface may be positively correlated to the amount of covalently immobilized
gelatin. The above results suggest that a high density of immobilized gelatin led to the en‐
hancement in NO secretion.
Figure 12. The amount of NO production for the ECs seeded on the pristine and functionalized PCL substrates. Data
presented as means ± SD, n=3. *p< 0.05 and **p< 0.01 corresponds to statistically significant difference as compared to
the pristine PCL.
3.5.4. Platelet activation on the bare and endothelialized PCL substrates
Apart from coagulation pathways, platelet activation is considered another important crite‐
rion in assessing blood compatibility of the biomaterial surface. The activation of attached
platelet results in platelet aggregation and the formation of a thrombus [54]. The subendo‐