In-Ho Bae

Thromboresistant and endothelialization effects of dopamine-mediated heparin coating on a stent material surface

Heparinization of surfaces has proven a successful strategy to prevent thrombus formation. Inspired by the composition of adhesive proteins in mussels, the authors used dopamine to immobilize heparin on a stent surface. This study aimed to assess the thromboresistant and endothelialization effects of dopamine-mediated heparin (HPM) coating on a stent material surface. The HPM was synthesized by bonding dopamine and heparin chemically. Cobalt–chromium (Co–Cr) alloy disks were first placed in the HPM solution and applied to surface stability then underwent thromboresistant tests and human umbilical vein endothelial cells (HUVEC) cytotoxicity assays. The results showed not only thromboresistant activity and a stable state of heparin on the surfaces after investigation with toluidine blue and thrombin activation assay but also proliferation of HUVEC in vitro. Studies on animals showed that the HPM-coated stent has no obvious inflammation response and increasing of restenosis rate compared to the bare metal stent (BMS) indicating good biocompatibility as well as safety in its in vivo application. Moreover, improving the endothelial cell (EC) proliferation resulted in a higher strut-covering rate (i.e., endothelialization) with shuttle-shaped EC in the HPM-coated stent group compared to that of the BMS group. These results suggest that this facile coating approach could significantly promote endothelialization and offer greater safety than the BMS for its much improved thromboresistant property. Moreover, it may offer a platform for conjugating secondary drugs such as anti-proliferative drugs.

Single coronary artery originating from the right aortic sinus without a left anterior descending and circumflex artery in conventional swine

Single coronary artery is a rare coronary artery anomaly. Very few previous reports of this anatomical malformation in swine have been found. A 22 kg Yorkshire X Landrace F1 crossbred castrated male swine was presented for enrollment in a coronary stent implantion study. Coronary angiography revealed a single coronary artery arising from the right aortic sinus. The right coronary artery and anomalous left coronary artery were implanted with novel coronary stents without any side effects.

Comparison of dextran‐based sirolimus‐eluting stents and PLA‐based sirolimus‐eluting stents in vitro and in vivo

The aim of this study was to compare dextran and Poly(l-lactide) (PLLA) polymer stent coatings as mediators for sirolimus (SRL) drug elution in a porcine coronary model. The bare metal stent (BMS) surface was first coated with a layer of SRL and then either dextran (DSS, a natural polymer) or PLA (PSS, a synthetic polymer). The release velocity of SRL was slightly faster in DSS than PSS over the first 7 days (78.5% and 62.3%, respectively, n = 10, p < 0.05) and continued to 28 days in both groups. The contact angle was dramatically decreased in DSS (38.7° ± 1.24) compared to BMS and PSS groups (72.7° ± 5.32 and 81.1º ± 1.70, respectively, n = 10, p < 0.05). Smooth muscle cell migration was arrested in both the DSS and PSS-treated groups compared to that in the nontreated group (4.2% ± 0.31, 5.8% ± 0.60, 80.0% ± 4.4, respectively, n = 10, p < 0.05). In the animal study, there were no significant differences in the injury score, the internal elastic lamina, and the lumen area among the groups. However, percent area stenosis was significantly decreased in the SRL-containing group (27.5% ± 2.52 in DSS and 27.9% ± 3.30 in PSS) compared to BMS (35.9% ± 3.51, p < 0.05). The fibrin score was higher in the PSS (2.9 ± 0.31) than BMS (2.1 ± 0.12) and DSS (2.5 ± 0.66). The inflammation score in the DSS (0.7 ± 0.21) was similar to that in the BMS (0.7 ± 0.12), which was dramatically lower than that PSS (1.5 ± 0.18, p < 0.005). Immunofluorescence analysis revealed that endothelialization was increased and inflammation prevented in the DSS. These results suggest that dextran may be useful for the fabrication of drug eluting stent as an alternative existing synthetic polymer.

Prednisolone- and sirolimus-eluting stent: Anti-inflammatory approach for inhibiting in-stent restenosis.

Glucocorticoids are powerful anti-inflammatory, immunosuppressive, and anti-proliferative agents. The aim of this study was to evaluate the effectiveness of a prednisolone- (PDScs) and sirolimus-coated stent (SRLcs) in preventing artery vessel neointimal hyperplasia and inflammatory reactions in vitro and in vivo. PDS, a synthetic glucocorticoid, is a derivative of cortisol, which is used to treat a variety of inflammatory and autoimmune conditions. The stents were fabricated with PDS, SRL, or both agents using a layer-by-layer coating system (designated as PDScs, SRLcs, and PDSRLcs, respectively). The surface morphology of the PDScs showed an evenly dispersed and roughened shape, which was smoothened by the SRL coating. Half of the total drug amounts were released within seven days, followed by an additional release, which continued for up to 28 days. The proliferation of smooth muscle cells was inhibited in the SRLcs group (31.5 ± 4.08%), and this effect was enhanced by PDS addition (PDSRLcs, 46.8 ± 8.11%). Consistently, in the animal study, the restenosis rate was inhibited by the SRLcs and PDSRLcs (18.5 ± 6.23% and 14.5 ± 3.55%, respectively). Especially, fibrin expression and inflammation were suppressed in the PDS-containing group (PDScs, 0.6 ± 0.12 and 1.4 ± 0.33; PDSRLcs, 0.7 ± 0.48 and 1.7 ± 0.12, respectively) compared to PDS non-containing groups (BMS, 1.1 ± 0.12, and 1.8 ± 0.55; SRLcs, 1.6 ± 0.32 and 2.0 ± 0.62, respectively). Moreover, re-endothelialization was enhanced in the PDScs group as determined using immunohistochemistry with a cluster of differentiation (CD)-31 antibodies. These results suggest that the inhibitory effect of SRLcs on anti-restenosis can be accelerated by additional coating with PDS, which has promising properties as a bioactive compound with useful anti-inflammatory effects.

Sirolimus coating on heparinized stents prevents restenosis and thrombosis

The aim of this study was to evaluate the inhibitory effect of sirolimus coating on the occurrence of restenosis and thrombosis with heparinized stents. Heparin and dopamine were conjugated by chemical bonding and anchored on the stent surface by a mussel-inspired adhesion mechanism. Subsequently, sirolimus was coated with poly lactic-glycolic acid on the heparinized stent surface. The heparin was well attached to the surface, and the surface was smooth after sirolimus coating. The smoothness of the surface was maintained after expansion of the stent. The amount of sirolimus released from the stent was 67.3% ± 4.55% within 7 days, followed by continual release up to day 28. The proliferation of smooth muscle cells was successfully arrested (51.3% ± 2.25% at 7 days of culture) by sirolimus released from the stent. Platelet adhesion was clearly prevented in the heparin-coated group (78.0 ± 8.00/1.8 cm2) compared to that in the heparin noncoated group (5.0 ± 1.00/1.8 cm2). Animal studies showed that the heparin and sirolimus-coated stent group had no obvious inflammatory response and no change in the fibrin score compared to those in the other groups. However, restenosis clearly decreased in the heparin and sirolimus-coated group (12.3% ± 3.54%) compared to the bare-metal stent group (27.5% ± 8.52%) and the heparin-coated group (25.3% ± 11.79%). These results suggest that heparinized surface-based sirolimus coating may be a useful approach for the prevention of restenosis and stent thrombosis.

Tacrolimus-eluting stent with biodegradable polymer is more effective than sirolimus- and everolimus-eluting stent in rabbit iliac artery restenosis model

Drug-eluting stents, which are widely used in percutaneous coronary intervention, are fabricated with various considerations, such as drugs, design, polymers, and coating techniques. The aim of this study was to compare tacrolimus-eluting stents (TES), sirolimus-eluting stents (SES) and everolimus-eluting stents (EES) under identical conditions. Poly(lactic-co-glycolic acid) (PLGA) biodegradable polymer was used to coat bare metal stents (Chonnam National University Hospital Stent, CNUH Stent) with the drugs in all fabricating procedures with an ultrasonic stent-coating machine. Surface morphologies of the stents were investigated by scanning electron microscopy. The effect of drugs released from stents on rat smooth muscle and human umbilical vein endothelial cells was examined by MTT assay. The stents were implanted in rabbit iliac arteries randomly, with either TES (n=10), SES (n=10), or EES (n=10). After six weeks of implantation, the stents were isolated and subjected to histopathological analysis. Cell viability decreased in a dose-dependent manner. The surface morphologies of the stents showed a smooth and uniform shape. The release patterns of the stents showed similar profiles over 30 days. There were no significant differences in the injury score, internal elastic lamina, lumenal area, neointimal area, percent area stenosis, and inflammation score among the three groups. However, there was a significant difference in the fibrin score (0.6±0.44 in the TES, vs. 0.8±0.48 in the SES, vs. 0.8±0.61 in the EES, n=10, p<0.05). This study showed that tacrolimus was not inferior to sirolimus (SRL) and everolimus (EVL). Moreover, tacrolimus (TCL) is more effective in decreasing the fibrin score. Therefore, tacrolimus can be a useful alternative drug for fabricating drug-eluting stents.

The Control of Drug Release and Vascular Endothelialization after Hyaluronic Acid-Coated Paclitaxel Multi-Layer Coating Stent Implantation in Porcine Coronary Restenosis Model

Background and Objectives Hyaluronic acid (HA) is highly biocompatible with cells and the extracellular matrix. In contrast to degradation products of a synthetic polymer, degradation products of HA do not acidify the local environment. The aim of this study was to fabricate an HA-coated paclitaxel (PTX)-eluting stent via simple ionic interactions and to evaluate its effects in vitro and in vivo. Materials and Methods HA and catechol were conjugated by means of an activation agent, and then the stent was immersed in this solution (resulting in a HA-coated stent). After that, PTX was immobilized on the HA-coated stent (resulting in a hyaluronic acid-coated paclitaxel-eluting stent [H-PTX stent]). Study groups were divided into 4 groups: bare metal stent (BMS), HA, H-PTX, and poly (L-lactide)-coated paclitaxel-eluting stent (P-PTX). Stents were randomly implanted in a porcine coronary artery. After 4 weeks, vessels surrounding the stents were isolated and subjected to various analyses. Results Smoothness of the surface was maintained after expansion of the stent. In contrast to a previous study on a PTX-eluting stent, in this study, the PTX was effectively released up to 14 days (a half amount of PTX in 4 days). The proliferation of smooth muscle cells was successfully inhibited (by 80.5±12.11% at 7 days of culture as compared to the control) by PTX released from the stent. Animal experiments showed that the H-PTX stent does not induce an obvious inflammatory response. Nevertheless, restenosis was clearly decreased in the H-PTX stent group (9.8±3.25%) compared to the bare-metal stent group (29.7±8.11%). Conclusion A stent was stably coated with PTX via simple ionic interactions with HA. Restenosis was decreased in the H-PTX group. These results suggest that HA, a natural polymer, is suitable for fabrication of drug-eluting stents (without inflammation) as an alternative to a synthetic polymer.

Novel Polymer-Free Everolimus-Eluting Stent Fabricated using Femtosecond Laser Improves Re-endothelialization and Anti-inflammation

The aim of this study was to fabricate a novel polymer-free everolimus-eluting stent with nanostructure using a femtosecond laser (FSL). The stent were coated with everolimus (EVL) using FSL and electrospinning processes. The surface was rendered hydrophobic, which negatively affected both platelet adhesion (82.1%) and smooth muscle cell response. Animal study was performed using a porcine coronary restenosis model. The study groups were divided into 1) bare metal stent (BMS), 2) poly(L-lactide) (PLA)-based EVL drug eluting stent (DES), 3) commercial EVL-eluting DES, and 4) FSL-EVL-DES. After four weeks of stent implantation, various analyses were performed. Quantitative analysis showed that the amount of in-stent restenosis was higher in the BMS group (BMS; 27.8 ± 2.68%, PLA-based DES; 12.2 ± 0.57%, commercial DES; 9.8 ± 0.28%, and FSL-DES; 9.3 ± 0.25%, n = 10, p < 0.05). Specifically, the inflammation score was reduced in the FSL-DES group (1.9 ± 0.39, n = 10, p < 0.05). The increment in re-endothelialization in the FSL-DES group was confirmed by immunofluorescence analysis. Taken together, the novel polymer-free EVL-eluting stent fabricated using FSL can be an innovative DES with reduced risk of ISR, thrombosis, and inflammation.

In vitro and in vivo evaluation of a novel polymer-free everolimus-eluting stent by nitrogen-doped titanium dioxide film deposition

Inflammation and thrombosis are linked to the use of polymer-based drug-eluting stents (DES). The aim of this study was to develop a polymer-free everolimus (EVL)-eluting stent using nitrogen-doped titanium dioxide (N-TiO2) and verify its efficacy by in vitro and in vivo assessment in a porcine coronary model. Various analytical approaches such as scanning electron microscopy and atomic force microscopy, electron spectroscopy, Fourier transform infrared spectrometry and contact angle measurement were employed for the characterization. As a part of biocompatibility assessment, platelet adhesion and smooth muscle cell (SMC) proliferation were examined. Bare metal stent (BMS), N-TiO2 stent, everolimus-eluting N-TiO2 (N-TiO2-EVL) stent, and commercialized EVL-eluting stent (EES) were randomly placed in forty coronary arteries in twenty pigs. After four weeks of implantation, the stents were subjected to histological and quantitative analysis. The N-TiO2 film used in this study was well coated without any cracks or peeling. Surface hydrophilicity (88.8% of angle decrement) could be associated with the decrease in surface roughness post N-TiO2 deposition (37.0%). The platelet adhesion on the N-TiO2 surfaces was less than that on the BMS surface. The proliferation of SMC was suppressed in the N-TiO2-EVL group (30.2%) but not in the BMS group. In the animal study, the percent area restenosis was significantly decreased in the N-TiO2-EVL group compared to that in the BMS group. The results (BMS; 47.0 ± 11.00%, N-TiO2-EVL; 31.7 ± 10.50%, and EES; 29.1 ± 11.21%, n = 10, p < 0.05) were almost at par with those of the commercialized EVL-eluting stent. The introduction of N-TiO2 deposition during fabrication of polymer-free DES may be an efficient accessorial process for preventing in-stent restenosis and thrombosis.

Hydrophilic surface modification of coronary stent using an atmospheric pressure plasma jet for endothelialization

The first two authors contributed equally to this study. Bioactivity and cell adhesion properties are major factors for fabricating medical devices such as coronary stents. The aim of this study was to evaluate the advantages of atmospheric-pressure plasma jet in enhancing the biocompatibility and endothelial cell-favorites. The experimental objects were divided into before and after atmospheric-pressure plasma jet treatment with the ratio of nitrogen:argon = 3:1, which is similar to air. The treated surfaces were basically characterized by means of a contact angle analyzer for the activation property on their surfaces. The effect of atmospheric-pressure plasma jet on cellular response was examined by endothelial cell adhesion and XTT analysis. It was difficult to detect any changeable morphology after atmospheric-pressure plasma jet treatment on the surface. The roughness was increased after atmospheric-pressure plasma jet treatment compared to nonatmospheric-pressure plasma jet treatment (86.781 and 7.964 nm, respectively). The X-ray photoelectron spectroscopy results showed that the surface concentration of the C–O groups increased slightly from 6% to 8% after plasma activation. The contact angle dramatically decreased in the atmospheric-pressure plasma jet treated group (22.6 ± 15.26°) compared to the nonatmospheric-pressure plasma jet treated group (72.4 ± 15.26°) (n = 10, p < 0.05). The effect of the increment in hydrophilicity due to the atmospheric-pressure plasma jet on endothelial cell migration and proliferation was 85.2% ± 12.01% and 34.2% ± 2.68%, respectively, at 7 days, compared to the nonatmospheric-pressure plasma jet treated group (58.2% ± 11.44% in migration, n = 10, p < 0.05). Taken together, the stent surface could easily obtain a hydrophilic property by the atmospheric-pressure plasma jet method. Moreover, the atmospheric-pressure plasma jet might affect re-endothelialization after stenting.