Biofunctionalization of titanium surface with multilayer films modified by heparin-VEGF-fibronectin complex to improve endothelial cell proliferation and blood compatibility.

In-stent restenosis and subsequent thrombosis remain a significant complication following the implantation of coronary stents. Different approaches have been used in developing novel coronary stents to protect against thrombosis and minimize restenosis. In the present study, we designed a biomacromolecular layer-by-layer coating with heparin, vascular endothelial growth factor (VEGF), and fibronectin onto nickel-free titanium surface to improve blood compatibility and endothelial cell proliferation. The multilayer assembling process was monitored by water contact angle and surface plasmon resonance, respectively. With increasing the number of layers, the deposition of polyelectrolyte as self-assembled ultrathin multilayer films showed linear growth of absorbance. In vitro blood compatibility results revealed that the fabricated layers prolonged activated partial thrombin time and prothrombin time, reduced platelets activation and aggregation, and reduced blood hemolysis rate. Cell adhesion and growth results showed that the assembled multilayer films significantly promoted cell attachment and growth, and the endothelialization property of the multilayer films was preferable compared with the untreated titanium disk. In conclusion, these results suggest that titanium surface modification using biofunctional multilayer films composed of heparin, VEGF, and fibronectin may serve as a potential approach to inhibit thrombosis and promote re-endothelialization of cardiovascular stents.

Safe upper limit of intermittent hepatic inflow occlusion for liver resection in cirrhotic rats.

AIM: To evaluate the effects of varying ischemic durations on cirrhotic liver and to determine the safe upper limit of repeated intermittent hepatic inflow occlusion. METHODS: Hepatic ischemia in cirrhotic rats was induced by clamping the common pedicle of left and median lobes after non-ischemic lobes resection. The cirrhotic rats were divided into six groups according to the duration and form of vascular clamping: sham occlusion (SO), intermittent occlusion for 10 (IO-10), 15(IO-15), 20(IO-20) and 30(IO-30) minutes with 5 minutes of reflow and continuous occlusion for 60 minutes (CO-60). All animals received a total duration of 60 minutes of hepatic inflow occlusion. Liver viability was investigated in relation of hepatic adenylate energy charge (EC). Triphenyltetrazollum chloride (TTC) reduction activities were assayed to qualitatively evaluate the degree of irreversible hepatocellular injury. The biochemical and morphological changes were also assessed and a 7-day mortality was observed. RESULTS: At 60 minutes after reperfusion following a total of 60 minutes of hepatic inflow occlusion, EC values in IO-10 (0.749 +/- 0.012) and IO-15 (0.699 +/- 0.002) groups were rapidly restored to that in SO group (0.748 +/- 0.016), TTC reduction activities remained in high levels (0.144 +/- 0.002 mg/mg protein, 0.139 +/- 0.003 mg/mg protein and 0.121 +/- 0.003 mg/mg protein in SO, IO-10 and IO-15 groups, respectively). But in IO-20 and IO-30 groups, EC levels were partly restored (0.457 +/- 0.023 and 0.534 +/- 0.027) accompanying with a significantly decreased TTC reduction activities (0.070 +/- 0.005 mg/mg protein and 0.061 +/- 0.003 mg/mg protein). No recovery in EC values (0.228 +/- 0.004) and a progressive decrease in TTC reduction activities (0.033 +/- 0.002 mg/mg protein) were shown in CO-60 group. Although not significantly different, the activities of the serum aspartate aminotransferase (AST) on the third postoperative day (POD(3)) and POD(7) and of the serum alanine aminotransferase (ALT) on POD(3) in CO-60 group remained higher than that in intermittent occlusion groups. Moreover, a 60% animal mortality rate and more severe morphological alterations were also shown in CO-60 group. CONCLUSION: Hepatic inflow occlusion during 60 minutes for liver resection in cirrhotic rats resulted in less hepatocellular injury when occlusion was intermittent rather than continuous. Each period of 15 minutes was the safe upper limit of repeated intermittent vascular occlusion that the cirrhotic liver could tolerate without undergoing irreversible hepatocellular injury.