Academic literature on the topic 'Bioabsorbable stent'

Objective: This study aimed to compare, using optical coherence tomography (OCT), the outcomes of bioabsorbable drug-eluting stent with those of bare metal stent (BMS) following implantation in porcine iliac artery. Methods: After the placement of BMS and bioabsorbable drug-eluting stents, we used OCT and digital subtraction angiography to investigate stent appositions, arterial neointima, evagination, and restenosis at 1 and 3 months. Results: At 1 and 3 months after stent implantation, OCT study was performed to investigate 32 stents and 21 788 struts. Thirty-three malapposed struts were found in the bioabsorbable drug-eluting stent groups and 2 were found in BMS groups. The average neointimal thickness, area, and in-stent stenosis were significantly lower in bioabsorbable drug-eluting stents than in BMS, while the frequency of malapposed struts was higher in the bioresorbable drug-eluting stent groups. Average neointimal thickness was lower in bioabsorbable drug-eluting stents than in BMS at 1 (0.19 ± 0.09 vs 0.67 ± 0.75 mm; P < .001) and 3 months (0.21 ± 0.08 vs 1.52 ± 0.28 mm; P < .001). Conclusion: Our study suggested that bioabsorbable drug-eluting stent is more effective in decreasing arterial restenosis than BMS in animal models.

Transcatheter treatment of children with congenital heart disease such as coarctation of the aorta and pulmonary artery stenosis currently involves the use of metal stents. While these provide good short term results, there are long term complications with their use. Children outgrow metal stents, obligating them to future transcatheter dilations and eventual surgical removal. A bioabsorbable stent, or a stent that goes away with time, would solve this problem. Bioabsorbable stents are being developed for use in coronary arteries, however these are too small for use in pediatric congenital heart disease. A bioabsorbable stent for use in pediatric congenital heart disease needs to be low profile, expandable to a diameter 8 mm, provide sufficient radial strength, and absorb quickly enough to allow vessel growth. Development of absorbable coronary stents has led to a great understanding of the available production techniques and materials such as bioabsorbable polymers and biocorrodable metals. Children with congenital heart disease will hopefully soon benefit from the current generation of bioabsorbable and biocorrodable materials and devices.

Recent stent developments aimed to reduce and eliminate the long-term inflammatory response include thinner struts, modifications to stent design and the development of bioresorbable polymers (BP). We aimed to summarize the main findings and to discuss the established and the potential benefits of the Orsiro BP sirolimus-eluting stents in everyday clinical use. We have reviewed the available evidence on the clinical performance of the Orsiro BP drug-eluting stents. Orsiro BP sirolimus-eluting stents is clinically proven and showed noninferiority against major drug-eluting stents and provides high safety and efficacy profile at long-term follow-up. Furthermore, it may be the preferred treatment option in specific subgroups as acute coronary syndrome, as shown in the BIOFLOW V trial.

IntroductionThe advent of metal flow-diverting stents has provided neurointerventionalists with an option for treating aneurysms without requiring manipulations within the aneurysm sac. The large amount of metal in these stents, however, can lead to early and late thrombotic complications, and thus requires long-term antiplatelet agents. Bioabsorbable stents have been postulated to mitigate the risk of these complications. Here we present early data on the first self-expandable primarily bioabsorbable stent for aneurysms.MethodsBraided stents were developed using poly-L-lactic acid fibers with material surface area similar to metal flow diverters. Crush resistance force, hemolysis, and thrombogenicity were determined and compared with existing commercial devices. Stents were deployed in infra-renal rabbit aortas to determine angiographic side branch patency and to study neointima formation for a 1-month follow-up period.ResultsCrush resistance force was determined to be on the order of existing commercial devices. Hemolytic behavior was similar to existing metal devices, and thrombogenicity was lower than metal flow-diverting stents. A smooth neointimal layer was found over the absorbable stent surface and all covered side branches were patent at follow-up.ConclusionThe design of self-expanding primarily bioabsorbable flow-diverting stents is possible, and preliminary safety data is consistent with a favorable profile in terms of mechanical behavior, hemocompatibility, side branch patency, and histological effects. Additional in vitro and long-term in vivo studies are in progress and will help determine aneurysm occlusion rates and absorption characteristics of the stent.

The aim of this study was to develop a bioabsorbable, degradable stent for drug storage that can be produced rapidly. A stent with a length of 28[Formula: see text]mm and a diameter of 6[Formula: see text]mm was generated by injecting polycaprolactone (PCL) (PubChem CID:6452583) into a mold created using a toggle-type microtool machine. Micropores of 0.5[Formula: see text]mm diameter and 0.6[Formula: see text]mm depth were created on stents. A stent had 54 pores, and each pore had a storage volume of 0.1175[Formula: see text]c3. To determine the optimal PCL concentration for stent construction, stents of three PCL concentrations (20%, 25%, and 30%) were fabricated in the experiment, and the material and chemical properties of the stents were determined. In addition, four proportions of PCL:PLGA (10:0, 8:2, 5:5, 0:10) were tested, and the corresponding pore degradation time was employed as a reference parameter for controlling the amount of drug release in the stent design. With an increase in PCL concentration from 20% to 30%, the load increased from 39.718 to 63.5[Formula: see text]N. The stent with 25% PCL concentration exhibited optimal surface roughness ([Formula: see text][Formula: see text]nm). Finally, scanning electron microscopy indicated that the surface of the material with 25% PCL concentration did not contain any fractures and exhibited planar evenness. The results demonstrate the development of a bioabsorbable, degradable stent that can be applied in vascular surgery.

AbstractEndoscopic biliary stenting is one of the most commonly used palliative procedure in patients with unresectable malignant distal biliary obstruction. Biliary stenting can be performed with either plastic or metallic stents. Stent occlusion and migration are important limitations of currently available stents. Variety of newer stents with varying designs and stent materials like stents with antimigratory properties, antireflux stents, drug-eluting stents, radioactive stents, and bioabsorbable stents are being developed to overcome the limitations of currently available stents. In this article, we are discussing two articles on the newer stent designs (plastic and metal stents) for biliary drainage in patients with unresectable malignant distal biliary obstruction.

Abstract Objectives Bioabsorbable steroid eluting stents may prevent the stenosis of ostia after sinus surgery. We describe a technique utilizing this technology to prevent the reformation of Rathke's cleft cysts (RCC) after transnasal transsphenoidal surgical drainage. Design This study is based on retrospective review. Setting The research took place at Tertiary academic medical center. Participants Patients who underwent endoscopic marsupialization of RCC with stent placement were participated in this study. Main Outcome Measures Demographics, surgical history, outcomes, and complications were primary measures of this study. Results Four patients underwent drainage of a recurrent RCC with subsequent stent placement. All patients consented to off-label use of the stent. The mean age of patients was 42 years old and the number of prior drainage procedures ranged from 1 to 3. The stent was placed directly into the opening of the cyst after drainage with no other tissue placed into the cyst cavity or opening. The stents are bioabsorbable and were not removed after surgery but were evaluated endoscopically at 2 and 6 weeks after surgery. The patients have been followed for a mean of 14 months after surgery with no evidence of recurrence on endoscopic exam or imaging. No patient had cerebrospinal fluid leak during or after the operation or permanent endocrinopathy. Conclusion The use of a bioabsorbable steroid eluting stent had no unanticipated consequences and all drainage pathways of all the RCCs remain patent. The use of this technology may decrease recurrence rates in revision or complex cases where patients have extensive scarring of the operative field from prior drainage procedures. Further follow-up of the current cases and study in a larger cohort are warranted.

Objective. To investigate acute recoil of bioabsorbable poly-L-lactic acid (PLLA) stent.Background. As newly developed coronary stent, bioabsorbable PLLA stent still encountered concern of acute stent recoil.Methods. Sixteen minipigs were enrolled in our study. Eight PLLA XINSORB stents (Weite Biotechnology Co., Ltd., China) and eight metallic stents (EXCEL, Jiwei Co., Ltd. China) were implanted into coronary arteries. Upon quantitative coronary angiography analysis, acute absolute recoil was defined as the difference between mean diameter of inflated balloon (X) and mean lumen diameter of stent immediately after deployment (Y), while acute percent recoil was defined as (X−Y)/Xand expressed as a percentage. Intravascular ultrasound (IVUS) was performed immediately after implantation and 24 hours later to compare cross-sectional area (CSA) between two groups and detect stent malapposition or collapse.Results. Acute absolute recoil in XINSORB and EXCEL was0.02±0.13 mm and −0.08±0.08 mm respectively (P=0.19). Acute percent recoil in XINSORB and EXCEL was0.66±4.32% and −1.40±3.83%, respectively (P=0.45). CSA of XINSORB was similar to that of EXCEL immediately after implantation, so was CSA of XINSORB at 24-hours followup. Within XINSORB group, no difference existed between CSA after implantation and CSA at 24-hours followup. No sign of acute stent malapposition was detected by IVUS.Conclusions. The acute stent recoil of XINSORB is similar to that of EXCEL. No acute stent malapposition or collapse appeared in both kinds of stent. This preclinical study was designed to provide preliminary data for future studies of long-term efficacy and safety of XINSORB stent.

Highlights. Bioabsorbable vascular scaffolds for percutaneous coronary interventions in multivessel coronaryartery disease patients and concomitant type 2 diabetes mellitus may increase the effectiveness of endovascular treatment and improve the long-term prognosis. The review article discusses recent data and evidences on the efficacy and safety of various stent generations for treating patients with coronary artery disease. The main complications commonly occurred following the implantation of drug-eluting stents in the long-term period are summarized, suggesting the rationale for the use of the next generation bioabsorbable vascular scaffolds in routine clinical practice. Bioabsorbable vascular scaffolds for endovascular treatment of patients with coronary artery disease show comparable efficacy compared with conventional drug-eluting stents. Particular attention is paid to the technical approaches of bioabsorbable vascular scaffold implantation, the use of intavascular imaging to control the implantation, as well as the timing of dual antiplatelet therapy in the postoperative period. The final term of the first-generation scaffold absorption, dual antiplatelet therapy, the effectiveness of bioabsorbable vascular scaffold-treated distal lesions and safety in patients with type 2 diabetes are highlighted. Future perspectives of using the next generation bioabsorbable vascular scaffolds that may improve the efficiency of percutaneous coronary interventions are presented.

The main motivation of this work was to analyse the feasibility of the current stent’s manufacturing process to produce the new bioresorbable stents (BRS) as well as study new manufacturing methods. Fibre Laser Cutting (FLC) has been selected because is the current manufacturing process for stents, and 3D-Printing (3DP) because its capability to process different types of materials for medical applications and their economic aspects. Stents have been selected for being one of the most implanted biomedical device in the world. The thesis focuses on improve the bioresorbable stent’s manufacturing processes, establishing relationships between the process parameters and the key stent aspects, namely, precision, mechanical properties, and medical properties, and reduce the costs derived of the manufacturing process
La principal motivació d'aquest treball va ser analitzar la viabilitat del procés de fabricació de stent actual per produir els nous stents bioabsorbibles (SBA), així com estudiar noves maneres de fabricar-los. El tall làser de fibra (TLF) ha estat seleccionat perquè és el procés de fabricació actual per stents i L´impressió 3D (I3D) perquè té la capacitat de processar diferents tipus de materials per a aplicacions mèdiques i els seus aspectes econòmics. Stents ha estat seleccionat per ser un dels dispositius mèdics més implantats del món. La tesi es centra en la millora dels processos de fabricació de stent, establint relacions entre els paràmetres del procés i els aspectes clau de stent, precisió, propietats mecàniques i propietats mèdiques i reduir els costos derivats d'aquest procés de fabricació

i. Poly(L-lactic acid), which is the current gold standard to fabricate bioresorbable stents, was modified by blending, with the aim to prepare a material with lower degradation time and improved mechanical properties. Binary blends of poly(L-lactic) acid (PLLA1: 80428 Da and PLLA2: 201790 Da) and poly(lactide-co-glycolide) (PLGA1) (LA:GA = 50:50 mol:mol; 32030 Da) with various compositions (100/0; 75/25: 50/50; 25/75; 0/100 wt./wt.) were prepared by solution casting. SEM analysis showed a biphasic morphology. Some degree of blend compatibility was suggested by the measured glass transition temperatures of blends with respect to pure components. Tensile mechanical properties evidenced higher compatibility for blends based on PLLA1 and for PLLA2/PLGA1 75/25 composition. Blends containing 75 wt.% PLGA were selected for further characterizations due to their superior mechanical properties. In vitro degradation tests showed PLGA rapid degradation within 2-4 weeks, leading to porous samples. A limited inflammatory reaction resulted from subcutaneous implantation of blend samples in Balb-c mice, suggesting their suitability for biomedical applications. Effect of macrophages adhesion and related cytokines release on endothelial cells (PAOEC) proliferation and migration was evaluated on PLLA2/PLGA1 75/25 blend compared to pure polymers. Slight differences were shown by the macrophages reaction when in contact with PLLA2, PLGA1 or PLLA2/PLGA1 75/25 blend. However, these differences showed to differently enhance endothelial cells behaviour in terms of healing from a wound scratch, in particular PLLA2/PLGA1 75/25 promoted a fast healing. To reduce the blend fast degradation rate, PLGA2 (LA:GA = 50:50 mol:mol, Mw = 77000 – 106000 Da) was used instead of PLGA1, in blends with PLLA1 and PLLA2, as it possesses a lower degradation rate than PLGA1. Binary blends were prepared with different compositions (PLLA1 (or PLLA2)/PLGA2 25/75; 50/50; 75/25). The fractured sections of blend film samples showed the presence of two phases, suggesting immiscibility. However, dispersed domains were of lower size as compared to the corresponding blends containing PLGA1, suggesting a superior compatibility degree with increasing the LA content of poly(lactic acid-co-glycolic acid) phase. The glass transition behaviour of PLLA2/PLGA2 compositions indicated some compatibility between the polymers. Tensile mechanical analysis showed that the maximum tensile strength (max) decreased significantly with increasing the amount of PLGA2 into the blends. The max of blend samples was higher than that predicted by the rule of mixtures for PLLA1/PLGA2 75/25 (max = 26 MPa) and PLLA2/PLGA2 75/25 blend (max = 39 MPa). Young’s modulus (E) behavior as function of amount of PLGA2 into the blends was similar to that of maximum tensile strength. The E of blend samples was higher than that predicted by the rule of mixtures only for PLLA1/PLGA2 75/25 composition (E = 435 MPa). The obtained results led to the selection of PLLA2/PLGA2 75/25 and PLLA1/PLGA2 75/25 blends for further characterisation, due to their superior compatibility and mechanical properties compared to the other blend compositions. To further improve the compatibility between the components in PLLA1/PLGA2 and PLLA2/PLGA2 blends (and consequently to increase the blend mechanical properties), the effect of three different compatibilizers - polycaprolactone (PCL), poly(D,L-lactide-co-caprolactone) (PCL-co-PLA) and poly(D,L-lactide-co-caprolactone) (PLA-co-PCL -co-PGA) – was compared. In compatibilized blends, a reduction of the size of the dispersed phase inclusions (< 1μm) and a less distinct interface between the phases was detected, as compared to uncompatibilised blends with the same weight ratio between the components. The Tg behaviour confirmed the increase of the compatibility between the phases when a compatibilizer was used, in particular the lower ΔTgs between blend components was obtained when 1% PCL was added to PLLA1/PLGA2 75/25 blend (ΔTg = 5.8 °C) and to PLLA2/PLGA2 75/25 (ΔTg = 6.2 °C) . Compatibilized PLLA2/PLGA2 75/25 blends showed better mechanical behavior with respect to compatibilized PLLA1/PLGA2 75/25 blends. Among, compatibilised PLLA2/PLGA2 75/25 blends, some improvements of the mechanical performance over uncompatibilised PLLA2/PLGA2 75/25 (E = 383 MPa; σmax = 40 MPa) blends were obtained for PLLA2/PLGA2 75/25 + 2% PCL (σmax =52.1 MPa, E= 382.5 MPa, ε=31.9%). Due to the small differences in mechanical performance of compatibilised and uncompatibilised PLLA2/PLGA2 75/25 blends, the uncompatibilised PLLA2/PLGA2 75/25 blend was selected as optimal blend composition for the development of bioresorbable stents or coatings for metal stents. In vitro degradation tests showed that the weight of PLLA2/PLGA2 75/25 samples did not vary significantly after 2-8 weeks incubation time in PBS. In vitro cells tests performed on PLLA2/PLGA2 75/25 blend using endothelial cells (PAOEC) for 72h days showed that cells adhered and proliferated well on them as compared to the control. Some preliminary tests were performed for the incorporation of Tacrolimus within PLLA2/PLGA2 75/25 blend, however the drug was not released after 30 days incubation in PBS, suggesting that the method for the incorporation of the drug into the blend must be optimised. Moreover, preliminary experiments were carried out for the fabrication of tubular conduits based on PLLA2/PLGA2 75/25 blend by a solution dipping – rotating mandrel technique, from which it is possible to fabricate stents by laser ablation. As a conclusion, in this thesis work, a suitable polymeric material for stent preparation was selected (PLLA2/PLGA2 75/25 blend). In the future this material will be used to prepare drug eluting stents by laser ablation of tubular constructs or drug eluting coating for stainless steel stents. Additional mechanical tests on model polymer stents will be necessary to assess PLLA2/PLGA2 75/25 blend suitability for stent applications. ii. To achieve the second aim of this thesis work, proper surface modification techniques were developed for both the polymer material and stainless steel substrates. Nanocoatings were obtained by applying the layer-by-layer (LbL) technique to coat PLLA2 and PLLA2/PLGA2 75/25 films and stainless steel plates (kindly purchased from C.I.D. s.r.l.) with the purpose to confer antithrombogenic properties to the selected material for the fabrication of bioabsorbable stents. Two different LbL deposition methods were developed and characterized: (i) method 1 used heparin (HE) and poly(diallyldimethylammonium chloride) (PDDA) as polyanion and polycation, respectively; (ii) method 2 used poly(styrene sulfonate) (PSS) as polyanion, PDDA as polycation and HE as the last deposited polyanion. A surface priming treatment was applied before depositing LbL coating. Heparin was selected because it has the highest negative charge density of any known biological macromolecule and anticoagulant properties; whereas PDDA and PSS were selected because are biocompatible and FDA approved. PLLA2 model films were pre-functionalized through aminolysis by using 1,6-hexamethylenediamine reagent with different parameter sets: reagent concentration (C), aminolysis treatment times (t) and temperatures (T). The optimal treatment parameters for PLLA2 cast films were selected on the basis of contact angle values and surface morphology and were found to be: C = 0.08 g/ml, t = 12 min and T = 37 °C. In details, PLLA2 contact angle decreased from 74 °C to about 65°C after aminolysis under the above parameters, while surface morphology was not altered. The effectiveness of the selected aminolysis treatment was confirmed both by XPS analysis, which showed the appearance of the N1s peak due to the formation of amino groups, and by a colorimetric method for amino groups quantification. The same aminolysis treatment was successfully performed on PLLA2/PLGA 75/25 films, as demonstrated by the obtained wettability (contact angle decreased from 81 °C to 70 °C ) and by amino groups quantification by a colorimetric method (NH2 concentration increased from 3 to 26 ng/mm2). LbL coatings were then deposited on aminolysed PLLA2/PLGA 75/25 film. The surface wettability of blend samples coated according to method 2 was higher compared to that of blend samples coated according to method 1: after the deposition of the 14th layer, static contact angle was around 50° and 67°, for samples modified according to method 2 and method 1,respectively. FTIR-ATR spectra of LbL samples coated according to method 2 demonstrated the presence of PSS/PDDA on the sample surface after the deposition of 14 layers . On the contrary, FTIR-ATR spectra did not vary after LbL deposition performed according to method 1. These results suggested that the treatment according to method 2 resulted in the formation of more homogeneous and thicker LbL coatings compared to method 1. XPS analysis and a colorimetric method employing toluidine blue (indicating the presence of HE and PSS) confirmed the successful deposition of the polyelectrolytes on the blend surface coated by method 2. The stainless steel (SS) plate surface was activated by incubation in an alkaline solution to expose hydroxyl groups and then priming treatment was performed using 3-aminopropyl triethoxysilane (APTES). APTES coating consisted of globular submicrometer domains and autofluorescence of APTES coating was indicative of the multilayered structure of APTES coatings on stainless steel substrates. XPS analysis demonstrated the presence of amino groups on the APTES-functionalised surface. LbL was performed on APTES modified stainless steel samples using both method 1 and method 2. FTIR-ATR spectra of coated samples evidenced the presence of typical absorption peaks of polyelectrolytes, confirming the successful LbL deposition for both methods. Static contact angle measurements showed that method 2 allowed the obtainment of surfaces with increasing hydrophilicity with increasing the layer number: after the deposition of 10 layers, static contact angle was lower than the value of pure polyelectrolytes. On the contrary, surface contact angle of samples modified using method 1 approached the contact angle values of polyelectrolytes after the deposition of 13-14 layers. This result suggested that method 2 allowed the obtainment of a more homogeneous LbL coating. Method 2 was thus selected also for stainless steel functionalisation. XPS analysis confirmed the successful deposition of the polyelectrolytes on the LbL coated sample surface. A colorimetric method employing toluidine blue was also used to detect the polyanion deposition. As a conclusion, in this work specific surface priming methods were developed for prefunctionalisation of stainless steel substrates and PLLA2/PLGA 75/25 samples. Moreover, a LbL method was optimized for the coating of pre-functionalised stainless steel and PLLA2/PLGA 75/25 samples. The aim of developed LbL coatings was that to expose HE to allow the obtainment of samples with anti-thrombogenic properties; moreover, HE could be exploited for the surface functionalisation with bioactive peptides, able to electrostatically interact with this glycosaminoglycan and exposing selective bioactive recognition sequences for interaction with receptors on endothelial cells. As an example, the KKKKKKSGSSGKCRRETAWAC peptide could be employed: CRETTAWAC sequence is able to favor EC adhesion while it hinders platelet attachment, KKKKKK is necessary for electrostatic interaction with HE and SGSSGK is a spacer sequence. This thesis work was focused on materials for cardiovascular applications, with reference to stenting. However, the possible transfer of the materials prepared and the experimental approach developed in vascular tissue engineering and wound healing was investigated. Therefore, model aminolysed PLLA2 films were prepared and coated by the LbL technique with suitable polyelectrolytes. The aim was that to prepare LbL coated PLLA2 substrates to be used in the form of porous tubular conduits for vascular tissue engineering or fibrous substrates for wound healing. For the preparation of fibrous substrates for wound healing, two different techniques were applied: wet-spinning and deposition by Pressure Assisted Microsyringe (PAM). The polyelectrolytes selected for the multilayered nanocoating were: heparin (HE), as polyanion, due to its high negative charge and ability to bind growth factors for wound healing or bioactive peptides favoring endothelisation (depending on the final application), and chitosan (CH), as polycation, due to its antimicrobial properties and biocompatibility. PLLA2 microfibers (50-90 μm) were prepared by the wet-spinning technique, using 7% (wt/v) PLLA2 solution concentration and 6mL/h spin rate. Microstructures were also prepared by PAM technique, extruding a polymeric solution (5% wt/v concentration) through a needle onto a glass slide, fabricating grids with regular geometry and hexagonal pores (diameter = 500 µm). Aminolysis treatment (0.08 g/mL, for 12 min at 37°C) was successfully performed on PLLA2 films and PLLA2 microfibers; however PAM microstructures underwent degradation and fragmentation after aminolysis due to their limited thickness (diameter of 5 μm). For this reason, they could not be used further for LbL coating. After aminolysis, film and microfiber samples were coated with 20 alternate layers of HE and CH. Surface wettability analysis showed alternate values of the contact angles as a function of the layer number, varying between the characteristic HE (40° C) and CH contact angles (60 °C). The presence of the two polyelectrolytes in the multilayer coating was also confirmed by XPS spectra, which showed the presence of the N1s peak, associated with both HE and CH deposition, and S2p peak, due to HE deposition. As a conclusion, HE/CH-LbL coated PLLA2 was found to be suitable for the fabrication of micrometric fibers by wet spinning, which in the future could be used to prepare porous scaffolds of desired shape (flat membranes or tubular constructs) by fiber compression molding in a suitable mold.

博士
中原大學
生物醫學工程研究所
106
Angioplasty is considered the most effective treatment for atherosclerosis. The stent currently used in clinical medicine is divided into a typical vascular stents and an drug-coated stents. Use of typical vascular stents has a high probability of restenosis development. Vascular restenosis occurs within a few months after stent implantation, and patients require surgical intervention. In contrast to such stents, drug-coated stents can effectively inhibit the growth of vascular endothelial tissues on stents. Given the physiological mechanism, drug-coating inhibits tissue growth on the stent, induces the local regulation of tissue inflammation, and triggers an immune response. However, the efficacy of such stents is limited because the metabolites in the blood of the human body rapidly metabolize the drug on the stent. In this study, we developed and examined a stent drug-release system that overcomes the problems in current stent technology. In addition, we designed the drug storage stent. The stent can be used to achieve long-term controlled drug release and to treat cardiovascular-related diseases. Rapid production of brackets through mold forming. The study used a "toggle-type micro-tooling machine" for micro-engraving of the mold, and injected polycaprolactone (PCL) into the designed mold to produce a stent having a length of 28 mm and a diameter of 6 mm. Micropores with a diameter of 0.5 mm and a depth of 0.6 mm were created on the stent. The stent has 54 holes, each of which can store 0.12 c3 of drug. In order to determine the optimal PCL concentration material for the stent, three stents with PCL concentrations (20%, 25%, and 30%) composite material were prepared in the experiment. The AFM results showed that the PCL 25% composite material concentration of the stent had the smallest surface roughness (RA = 1.77E + 02nm) and had the lowest effect on the blood vessels. In the sample with the PCL 25% composite material concentration, the stent surface was smooth and without fractures under 25× magnification , while under 500× magnification, an even surface was observed . In addition, With an increase in PCL composite material concentration from the PCL 20% to 30%, the load increased from 39.718 to 63.5 N. Young’s modulus increased from 31.44±4.1MPa to 33.10±2.7 Mpa. In addition, four proportions of PCL:PLGA (10:0, 8:2, 5:5, 0:10) were tested. After degradation experiments, it was found that when the proportion of PCL of the mixture increased, the PBS exudation rate slowed down. Verify that the molecular weight is changed to control the rate of degradation. The corresponding pore degradation time was employed as a reference parameter for controlling the amount of drug release in the stent design. The results indicated that the hemolysis of vascular stent material was 1.2%. The results of this study indicated no hemolysis, which verified that the biodegradable drug-loaded vascular stent was suitable for application in the bloodstream. The result of Platelet experiment which revealed that surface roughness affected the amount of platelet and fibrinogen adhesion. And less roughness on a stent surface reduced platelet adhesion and blood coagulation. The results of drug release rate showed that the release of everolimus increased with time, and the release amount was the highest at 8 hours, and the release rate was 36.95%. The result of coverage experiments have shown that hyaluronic acid coated everolimus is slowly elevated, and everolimus is slowly infiltrated into hyaluronic acid. This result of the swelling rate experiment, it was found that the degree of swelling containing everolimus was 13 times lower than that of the original hyaluronic acid. Therefore, hyaluronic acid encapsulates everolimus, which does would not block blood vessels. After 120 h, the amount of LDH release did not show any evident increase (p < 0.05). The release rate of LDH in this study was 13–18%, which indicated that the cocultivation of vascular stent material and cells did not cause high levels of cell death or damage, biocompatibility was high, and it was suitable for use in blood vessels. The result of animal experiment was carried out by pig (Lanyu 200), aged from 6~7 month, male and weighed about 50 kg. To verify the biocompatibility between the scaffold and the animal, the results showed that it was initially observed in the animal for 3 months. The material was high compatibility in the blood vessels of the pigs, and there was no toxicity, no rejection, no effect Animal life. The "bioabsorbable composite stent " developed in this study is proved to be suitable for application in blood vessels.

Coronary stent placement is a routine treatment of coronary artery disease, the leading cause of death worldwide. Intravascular Optical Coherence Tomography (IVOCT) is a superior imaging assessment technique in coronary stenting. To characterize IVOCT artifacts, phantom blood vessels were constructed and metallic and bioabsorable coronary stents were deployed with and without phantom neointima. High resolution Micro-CT images of the stent strut were recorded as a gold standard and utilized to create a three-dimensional representation of a strut that was imported into computer optical simulations. Simulated IVOCT images were computed that include the IVOCT catheter, light reflection from stent struts with varying neointimal thickness and scattering in the vessel lumen. The simulation results along with IVOCT images of the phantom vessels were utilized to elucidate the mechanisms underlying the “sunflower effect”, bending of stent struts toward the imaging catheter and “merry-go-round” effect, variable apparent strut size of metallic stents. Atomic force microscopy was used to examine surface properties of metallic and bioabsorbale stents, revealing sources of the distinctive appearance of bioabsorable stents in IVOCT images. The model formed a basis to develop a correction algorithm to remove stent artifacts in clinical IVOCT images.
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Cardiac catheterization and coronary angiography are both key components to routine cardiology practice. This new edition of Cardiac Catheterization and Coronary Intervention has been fully updated since the first edition, with new sections on primary percutaneous coronary intervention, trends in vascular access, bioabsorbable stents, optical coherence tomography, and more. Filled with over 150 clinical images and schematic illustrations, the handbook is an accessible ‘how-to’ guide, designed to demystify complex cardiac catheterization investigations. Expanded to reflect developments in practice, this new edition also introduces a new chapter on the multidisciplinary team and their roles and responsibilities from pre- to post-procedural care and relevant training requirements. It contains detailed instructions on how to perform a comprehensive left and right heart catheterization procedure, choosing the correct catheter for coronary and graft angiography, and how to perform a diagnostic coronary angiogram and interpret the subsequent findings.

In this work, a computational model of PLLA (Poly L-lactic acid) stent was constructed to study the degradation behavior of the bioabsorbable stent in terms of the loss of mechanical integrity. A degradation model was improved based on experimental data from the literature, as well as a finite element (FE) model was constructed based on the model of the degradation behavior of PLLA material. The results showed that the degradation of the PLLA would switch the material property of stent from a uniform model to a heterogeneous model due to the decline of Young’s modulus locally at each location of the stent. Loss of mechanical integrity of the stent showed a bilinear behavior due to the decline of the Young’s modulus and the locale failure of the structure, respectively. The breakdown pieces of stent will stay a relative longer time in lesion after the loss of the mechanical integrity of the stent due to the nonlinear response of the degradation degree to the degradation time and strain in the material.

The bioabsorbable thermoplastic Poly(lactic acid), PLA, is extensively used in many medical applications including surgical sutures, drug delivery systems, internal fixation devices, tissue engineering scaffolds, and drug eluting stents. Frequently, a PLA component is required to withstand mechanical loading for a desired amount of time and then degrade via hydrolysis. In its raw, undegraded form, PLA exhibits a non-linear, viscoplastic mechanical response. Through the degradation process, the modulus, yield stress and flow behavior of PLA changes. Accurate simulations of bioabsorbable implants require a constitutive model that accounts for the viscoplastic nature of the material and its evolution over time. In this work we present the development of a new material model framework for predicting the time-dependent viscoplastic response of PLA. The proposed material model also captures the change in mechanical behavior over time due to hydrolysis. The details of the proposed model are presented, and the model predictions are compared to preliminary experimental data.