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![Chemical formula of the poly(lactic-co-glycolic acid) (PLGA) bioresorbable polymer developed at the Centre of Polymer and Carbon Materials [27].](profile/Jerzy-Malachowski/publication/340899893/figure/fig1/AS:883890998751232@1587747444610/Chemical-formula-of-the-polylactic-co-glycolic-acid-PLGA-bioresorbable-polymer.png)
Chemical formula of the poly(lactic-co-glycolic acid) (PLGA) bioresorbable polymer developed at the Centre of Polymer and Carbon Materials [27].
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The use of bioresorbable polymers such as poly(lactic-co-glycolic acid) (PLGA) in coronary stents can hypothetically reduce the risk of complications (e.g., restenosis, thrombosis) after percutaneous coronary intervention. However, there is a need for a constitutive modeling strategy that combines the simplicity of implementation with strain rate d...
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... considered material was originally developed at the Centre of Polymer and Carbon Materials (CPCM) of the Institute of the Polish Academy of Sciences [25,26]. It is a copolymer of lactic acid and glycolic acid (the chemical formula is presented in Figure 1, while the basic physical-chemical properties, based on data provided by CPCM, are presented in Table 1) [27]. [27]. ...
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... speed was 0.72 mm/min at a strain rate of 0.0003 1/s and 72.0 mm/min at 0.03 1/s. The results of numerical analyses of the effective strain rates for different variants for the socalled "knee-area," which is the area that undergoes the greatest deformation, are shown in Figure 11. The experimentally recorded radial force and the corresponding numerical results are compared in Figure 12. ...
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... results of numerical analyses of the effective strain rates for different variants for the socalled "knee-area," which is the area that undergoes the greatest deformation, are shown in Figure 11. The experimentally recorded radial force and the corresponding numerical results are compared in Figure 12. The compression radial force was calculated throughout the course of the analysis as the sum of rigid wall normal forces (contact forces between rigid walls and the stent outer surface, Figure 10) [35]. ...
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... experimentally recorded radial force and the corresponding numerical results are compared in Figure 12. The compression radial force was calculated throughout the course of the analysis as the sum of rigid wall normal forces (contact forces between rigid walls and the stent outer surface, Figure 10) [35]. ...
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... three stents were implanted successfully. In coronary angiography stents showed enough radial force to support overstretched vessel ( Figure 13). The OCT has shown good stent apposition and the analysis has shown lumen enlargement post implantation 24% as shown in Figure 13c. ...
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... coronary angiography stents showed enough radial force to support overstretched vessel ( Figure 13). The OCT has shown good stent apposition and the analysis has shown lumen enlargement post implantation 24% as shown in Figure 13c. At 28-day follow-up, all stents were covered with neointima, and struts embedded. ...
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... 28-day follow-up, all stents were covered with neointima, and struts embedded. Interestingly the signs of material hydrolysis were observed thus proving the polymer amorphic properties (Figure 14). ...
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... proposed constitutive modeling approach for the bioresorbable polymer is based on an isotropic elastic-visco-plastic model (Cowper-Symonds). Validation of the methodology based on two separate experimental tests confirmed strain rate dependency (Figure 11) and a plasticity model with hardening, key mechanisms of PLGA behavior. For all considered variants, the obtained force results ( Figure 12) showed an acceptable correlation between the numerical and experimental curves, proving the accuracy of the adopted approach. ...
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... of the methodology based on two separate experimental tests confirmed strain rate dependency (Figure 11) and a plasticity model with hardening, key mechanisms of PLGA behavior. For all considered variants, the obtained force results ( Figure 12) showed an acceptable correlation between the numerical and experimental curves, proving the accuracy of the adopted approach. ...
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... presented constitutive methodology was successfully used in the design process of bioresorbable stents within the Apollo STRATEGMED2 project. An exemplary stent prototype is presented in Figure 15. Author Contributions: Conceptualization, J.B., L.M., and J.M.; data curation, J.B., K.S. and P.P.B.; methodology, J.B., K.S. and L.M.; software, J.B. and L.M.; formal analysis, P.P.B. and J.M.; investigation, J.B., P.P.B and K.S.; resources, J.M. and K.S.; writing-original draft preparation, J.B. and P.P.B.; writing-review and editing, J.M., J.B., P.P.B. and L.M.; supervision, J.M. and K.S.; project administration, P.P.B., J.M. and K.S.; funding acquisition, P.P.B. and J.M.; validation, J.B. and P.P.B.; visualization, J.B. ...
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... The friction coefficient between the plate and the stent body is taken to be 0.8, the friction coefficient between the [7,37]. The stent is compressed in the radial direction, after that the load is removed and the result is recorded after stress relaxation [3]. Only a separate periodic section of the stent will be considered due to the large computational time. ...
... The study examined two different stent designs: a stent with sinusoidal shaped cells and a stent with Z-shaped cells. An important step is the modeling of crimping of a coronary polymer stent [3]. The assembled polymer stent is a structure crimped on a balloon with a conductor. ...
Cardiovascular diseases are one of the main problems in the world in medicine. It ranks first in the list of causes of fatal accidents, in addition, more than a half of cases are a result of ischemic heart diseases. One of the most effective method of treatment is coronary stenting. The main purpose of the study is to outline bioresorbable polymeric coronary stent's behaviour using computational modelling and to demonstrate benefits of application of polymer materials instead of standard metallic alloys. During the research the main stages of coronary stenting that are necessary for general understanding of process were analyzed: the strain after crimping, the shape of angioplasty balloon after deployment and the stress-strain state of vessel and atherosclerotic plaque after coronary stent deployment. PLLA (poly-L-lactic acid) was taken as a material for the research. It allows to create stent construction that will provide the required lumen of the vessel during rehabilitation. Moreover, with the progress of poly-L-lactic acid vasomotor function will restore thereby forming «golden section». The results showed the possibility of use of approaches that were given in this paper for examination of polymer material's behaviour with coronary stenting. It can be concluded that polymer bioresorbable coronary stents in medicine are promising for further application for improvement of quality of invasive coronary operation. © PNRPU
... It is responsible for 17.8 million deaths annually and is the third biggest cause of mortality worldwide [2]. It causes tremendous economic and health impediments in some of the most progressive nations [3]. The narrowing of the artery portrays CAD, the reason being plaque precipitating under the endothelium. ...
One of the prominent reasons for mortality and morbidity worldwide is coronary artery disease (CAD), an ailment that manifests itself by the narrowing of the artery with the deposition of plaque. The definitive mode of action for dealing with this condition is using a medical device known as a stent at the affected location. This extremely important tubular equipment helps tremendously with vessel support. It also helps by keeping the path of blood flow clear for the heart muscle masses, its crucial nutrients, and oxygen supply. Several generations of stents have been continuously developed to improve patient outcomes and reduce side effects post-stent implantation. As we move from bare metal stents (BMSs) to drug-eluting stents (DESs) and, more recently, to bioabsorbable stents, the research area continues to develop. The use of this biomedical device has increased the standard of living in many cases; therefore, it is much needed to work on the possible growth areas in the cardiovascular stents and improve them to such an extent that the patients suffering from cardiovascular ailments get to live a comfortable life. Most articles deal with stents that are available for current use and their various types. They also cover the topic of stent optimization, as it is one of the key factors in enhancing stent usability and plays a prominent role in optimizing stent placement in the vessels of the body. To keep in touch with advances in stent technology over the past few decades, this article reviews advances in the devices, working on how available stents can be optimized to create new stents.
... In addition, the porous feature can facilitate the installation of components inside or be compatible with a variety of drive methods instead of conventional pneumatic drives. For stent implantation, metamaterials intervertebral discs have previously been validated for their potential as lumbar disc stents for replacing damaged intervertebral discs [58][59][60]. The anti-collision filler in the helmet needs to be able to fit the head. ...
Auxetic structures have theoretically superior bending resistance that was previously inaccessible. Compared with the planar two-dimensional (2D) auxetic structures, the three-dimensional (3D) counterparts may exhibit auxetic behaviour in multiple directions. Recently, increasing studies have been devoted to studying the mechanical properties of 3D auxetic structures. In this paper, two 3D honeycomb structures were proposed, namely 3D re-entrant honeycomb and 3D hexagonal honeycomb. Subsequently, the mechanical properties, deformation modes, and deformation mechanisms of these two honeycomb structures under three-point bending were investigated experimentally and numerically. Compared with the 3D non-auxetic hexagonal honeycomb, the 3D auxetic re-entrant honeycomb exhibits higher ductility and fracture resistance. In addition, unlike the conventional honeycomb structure, the mid-span section of the 3D auxetic honeycomb exhibits a trapezoidal deformation mode under bending. Finally, the influence of the number of unit cells and geometric parameters on the mechanical properties of the 3D honeycomb structure were systematically studied by parametric analysis. The excellent bending performance provides a basis for the application of auxetic honeycomb in the fields of biomedicine, soft robots, and buffer devices.
... Scheme showing the strategy of SNAP impregnated polyurethane-based membrane to mimic the inner surface of blood vessels and thus inhibits platelet and bacterial adhesion (C). Reproduced with permission from the cited references[275][276][277]. ...
Implantable drug delivery systems (IDDS) are an attractive alternative to conventional drug administration routes. Oral and injectable drug administration are the most common routes for drug delivery providing peaks of drug concentrations in blood after administration followed by concentration decay after a few hours. Therefore, constant drug administration is required to keep drug levels within the therapeutic window of the drug. Moreover, oral drug delivery presents alternative challenges due to drug degradation within the gastrointestinal tract or first pass metabolism. IDDS can be used to provide sustained drug delivery for prolonged periods of time. The use of this type of systems is especially interesting for the treatment of chronic conditions where patient adherence to conventional treatments can be challenging. These systems are normally used for systemic drug delivery. However, IDDS can be used for localised administration to maximise the amount of drug delivered within the active site while reducing systemic exposure. This review will cover current applications of IDDS focusing on the materials used to prepare this type of systems and the main therapeutic areas of application.
... The recent research problems on endoscopy of arterial stenosis segments are given [17][18][19][20][21][22][23][24]. There are some fruitful research articles [25][26][27][28] should the balloon with stent be placed for an exact placement of stent, the minimizing effect of stenosis through catheter and stent application are all evident through this numerical analysis. A through numerical analysis via simulations is integrated for the cases of hemodynamic mechanism during the stent placement plus catheter insertion and after the stent is placed. ...
... The vessel walls are multilayered and the flow in the stent area is strongly turbulent. That is why such theoretical study case is a limited analysis as compared to the experimental data given in [25][26][27][28]. ...
The blood flow analysis inside an arterial segment of the left main coronary artery having stenosis is mathematically modeled. Numerical simulations are provided for the very first time for two considered cases that cover the thorough process of angioplasty and stent placement inside a coronary artery having symmetric stenosis. Firstly, the numerical simulations are disclosed for the section of a stenosed artery having a catheter placed inside it with a balloon plus stent over it. The second case covers the numerical simulations of blood flow inside the artery after a stent is placed that keeps the artery wide open and minimizes the effect of stenosis. Thus, the prime novelty of this work entertains the thorough mathematical modeling and FVM based numerical simulations for angioplasty of a coronary artery having a symmetric shape of stenosis. The current research work is modeled for the non-Newtonian Casson fluid to consider a more realistic approach of blood flow. This computational fluid dynamics (CFD) analysis is interpreted through the free source CFD C++ toolbox Open-FOAM. Numerical solutions are provided by using Open-FOAM that works on the principle of finite volume method. The detailed graphical results are disclosed for the process of angioplasty in addition to the simulation work obtained after completion of angioplasty and stent placement. The work provided is beneficial for surgical interpretations, detecting location of stenosis, place the balloon and stent at exact location via catheter, minimizing the effect of stenosis by placing a stent inside the artery, reducing the experimental cost by using simulations data. The catheter and balloon is removed after angioplasty, and the stent keeps the artery wide open to normalize the blood flow. Eventually, the coronary artery disease (CAD) is cured through this angioplasty and the risk of a heart attack is eliminated. A more developed and easily passing blood flow is revealed after the placement of stent.
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... In contrast, the unpredictable biodegradability of biocorrosive metal alloys increases the risk for thrombosis and restenosis [12]. Despite the advantages and disadvantages of both materials, it was shown in [13] that bioresorbable polymers are the better choice. Therefore, additional research was performed in the past to analyze the impact of stent geometry change on recoil reduction in bioresorbable scaffolds. ...
... These material models are mainly based on hyperelastic and viscoplastic behavior [12] and generally require a large number of material parameters [20]. A model involving the influence of a strain rate and kinematic/isotropic hardening was introduced in [13,21]. In [22], a new material model for biodegradable polymeric PLLA scaffolds, based on the direct use of experimentally obtained uniaxial tensile stretch-stress curves, was introduced. ...
Stents made by different manufacturers must meet the requirements of standard in vitro mechanical tests performed under different physiological conditions in order to be validated. In addition to in vitro research, there is a need for in silico numerical simulations that can help during the stent prototyping phase. In silico simulations have the ability to give the same stent responses as well as the potential to reduce costs and time needed to carry out experimental tests. The goal of this paper is to show the achievements of the computational platform created as a result of the EU-funded project InSilc, used for numerical testing of most standard tests for validation of preproduction bioresorbable vascular scaffolds (BVSs). Within the platform, an ad hoc simulation protocol has been developed based on the finite element (FE) analysis program PAK and user interface software CAD Field and Solid. Two different designs of two different stents have been numerically simulated using this integrated tool, and the results have been demonstrated. The following standard tests have been performed: longitudinal tensile strength, local compression, kinking, and flex 1-3. Strut thickness and additional pocket holes (slots) in two different scaffolds have been used as representative parameters for comparing the mechanical characteristics of the stents (AB-BVS vs. AB-BVS-thinner and PLLA-prot vs. PLLA-plot-slot). The AB-BVS-thinner prototype shows better overall stress distribution than the AB-BVS, while the PLLA-prot shows better overall stress distribution in comparison to the PLLA-plot-slot. In all cases, the values of the maximum effective stresses are below 220 MPa—the value obtained by in vitro experiment. Despite the presented results, additional considerations should be included before the proposed software can be used as a validation tool for stent prototyping.
... printed thermoplastic materials [59,66]. It could be attributed to the fact that the constitutive model of the material doesn't take into account the effect of loading rate and strain hardening, which may be improved by considering strain hardening theories [71,72]. When designing a polymer-based structures it is really important to understand the effect of the strain rate that the structure will be exposed as it directly impacts the mechanical performance of the part [73]. ...
This research investigates the effectiveness of bio-inspired suture structures in improving the fracture properties of thin 3D-printed plates. Inspired by the interlocked suture joint of the diabolical ironclad beetle, three designs are developed to identify the impact made by variations in size and the number of interlocking points on stabilizing and improving the fracture behaviour of thin, brittle 3D-printed plates. Incorporating a suture joint into a structure helps to control the crack propagation along the suture component, which will be beneficial in predicting the structure’s fracture properties. As the mechanical performance of the joint has a great impact on the properties of a thin-walled structure, utilizing sutures can provide light weight joints without external joining techniques. Among various beetle species, the diabolical ironclad beetle has garnered much attention as it can resist crushing forces twice as great as other beetle species. This suture contains interlocking pieces called blades which are ellipsoidal in shape and make the suture structure tougher than those of terrestrial beetles which have triangular or hemispherical blades. Specimens are printed through fused deposition modelling (FDM) using polylactic acid (PLA). The printed structure is thoroughly assessed by microscope and X-ray CT scan analysis. Experimental results are obtained for three different sizes of the suture structure, and a compact tension test is conducted for further examination of the structure’s behaviour by utilizing digital image correlation (DIC) and numerical simulation to capture the fracture mechanism and deformation of the suture structure.
... Bukala et al. [10] proposed a new approach to model constitutive bioresorbable polymers such as poly(lactic-co-glycolic acid) (PLGA), which is based on an isotropic elasticlow-plastic model (Cowper-Symonds). The use of PLGA in coronary stents can reduce the risk of complications (e.g., restenosis, thrombosis) after percutaneous coronary intervention. ...
The current Special Issue entitled “Processing, structure, dynamics and mechanical properties of polymeric materials” brings together scientists working at universities, research institutes, laboratories and various industries to discuss cutting-edge research on processing new polymeric materials using standard and innovative machines and to understand the structure and properties of these materials [...]
... PLA is stiffer and would provide support, while PCL would add flexibility to the structure. A constitutive modelling strategy for bioresorbable polymers such as PCL/PLA can vary between complex approaches requiring a wide range of material constants and relatively simple approaches with general elastic-plastic material [30,40,41]. A bilinear elastic-plastic material model was used for both polymers in this study. ...
Bioresorbable stents (BRS) are an alternative to existing bare-metal stents (BMS) and drug-eluting stents (DES), aiming to reduce the short- and long-term complications in cardiovascular interventions. A combination of biodegradable polymers in a composite scaffold is a promising solution to improve BRS flexibility and strength, which is currently limited by the material properties of polymers. In this study, a mechanical performance of a composite BRS comprised of two layers with four different combinations of polylactic acid (PLA) and polycaprolactone (PCL) was examined with finite element analysis (FEA). Stent crimping and expansion with the balloon inside an atherosclerotic artery was simulated, and stent performance parameters were evaluated and compared between different composite layer configurations. The single-material PCL stent showed the highest recoil and failed to provide support to the artery, while the stiffer single-material PLA stent experienced significantly lower recoil, but also the highest dogboning during expansion, which could increase arterial wall damage. Nearly identical performance was observed for both mixed-material configurations, with recoil and foreshortening closer to single-material PLA stent and dogboning during expansion between both single-material stents. They showed the highest dogboning after balloon deflation due to a combination of permanent deformation at the ends of the stent and lower stiffness at the middle, which allowed for higher recoil at the middle but not at both ends of the stent. The combination of biodegradable polymers into composite BRS shows potential for targeted stent designs with performance tailored to specific needs.
