Computational Analysis of Mechanical Performance for Composite Polymer Biodegradable Stents

Bioresorbable stents (BRS) represent the latest generation of vascular scaffolds used for minimally invasive interventions. They aim to overcome the shortcomings of established bare-metal stents (BMS) and drug-eluting stents (DES). Recent advances in the field of bioprinting offer the possibility of combining biodegradable polymers to produce a composite BRS. Evaluation of the mechanical performance of the novel composite BRS is the focus of this study, based on the idea that they are a promising solution to improve the strength and flexibility performance of single material BRS. Finite element analysis of stent crimping and expansion was performed. Polylactic acid (PLA) and polycaprolactone (PCL) formed a composite stent divided into four layers, resulting in sixteen unique combinations. A comparison of the mechanical performance of the different composite configurations was performed. The resulting stresses, strains, elastic recoil, and foreshortening were evaluated and compared to existing experimental results. Similar behaviour was observed for material configurations that included at least one PLA layer. A pure PCL stent showed significant elastic recoil and less shortening compared to PLA and composite structures. The volumetric ratio of the materials was found to have a more significant effect on recoil and foreshortening than the arrangement of the material layers. Composite BRS offer the possibility of customising the mechanical behaviour of scaffolds. They also have the potential to support the fabrication of personalised or plaque-specific stents.

Poly(L-Lactic Acid) Composite with Surface-Modified Magnesium Hydroxide Nanoparticles by Biodegradable Oligomer for Augmented Mechanical and Biological Properties

Poly(L-lactic acid) (PLLA) has attracted a great deal of attention for its use in biomedical materials such as biodegradable vascular scaffolds due to its high biocompatibility. However, its inherent brittleness and inflammatory responses by acidic by-products of PLLA limit its application in biomedical materials. Magnesium hydroxide (MH) has drawn attention as a potential additive since it has a neutralizing effect. Despite the advantages of MH, the MH can be easily agglomerated, resulting in poor dispersion in the polymer matrix. To overcome this problem, oligo-L-lactide-ε-caprolactone (OLCL) as a flexible character was grafted onto the surface of MH nanoparticles due to its acid-neutralizing effect and was added to the PLLA to obtain PLLA/MH composites. The pH neutralization effect of MH was maintained after surface modification. In an in vitro cell experiment, the PLLA/MH composites including OLCL-grafted MH exhibited lower platelet adhesion, cytotoxicity, and inflammatory responses better than those of the control group. Taken together, these results prove that PLLA/MH composites including OLCL-grafted MH show excellent augmented mechanical and biological properties. This technology can be applied to biomedical materials for vascular devices such as biodegradable vascular scaffolds.

Bioabsorbable vascular scaffolds in routine practice: long-term results

Background Recent publications suggest that bioabsorbable vascular scaffolds (BVS) carry an excess of thrombotic complications. Our goal was to describe the results in real life and in the long term, in a series of patients who received a BVS which is currently off the market. Methods Two hundred and thirteen consecutive patients who received at least 1 BVS between May 2012 and December 2016 were analyzed. The primary objective was the incidence of the compound event “target vessel failure” that included infarction or target vessel revascularization and cardiac death. Results Seventy-five percent of patients were men with a mean age of 61.4 years. They had a high prevalence of dyslipidemia (62.44%) and smoking (65.26%). The most common cause of admission was myocardial infarction without ST elevation (53.52%). A total of 233 coronary lesions were treated, with an average of 1.3±0.3 lesions per patient. The implant was successful in 99.5% of cases. Predilatation was performed in 89.3% and post dilation in 33.5% of cases. The use of intracoronary imaging (Optical Coherence Tomography OCT and/or Intravascular ultrasonography IVUS) to optimize the BVS implant was performed in 86 patients (40.38%). With a mean follow-up of 42.5 months, the incidence of target vessel failure was 6.57% during the first 24 months and 7.98% at the end of the follow-up. Regarding the device, this included 6 cases (2.81%) of thrombosis (definitive, probable or possible) and 10 cases (4.69%) of restenosis. Patients with a history of diabetes mellitus (HR 1.72 95% CI 1.01–2.95 P=0,05) and/or chronic oral anticoagulation (HR 5.71 95% CI 1.12–28.94 P=0.04) had a higher risk of target vessel failure. The use of intracoronary imaging (OCT and/or IVUS) during the BVS implantation had a considerable trend toward significance as a protective factor (HR 0.32 95% CI 0.11–1.03 P=0.06). Conclusions In this series of patients; in real life conditions, the incidence of target vessel failure was comparable to that previously described in randomized clinical trials. The events were more frequent during the first 2 years of follow-up, in the presence of greater cardiovascular comorbidity and in the absence of intracoronary imaging during the implantation. FUNDunding Acknowledgement Type of funding sources: Other. Main funding source(s): European Society of Cardiology KM curve for target vessel failure (TVF) Predictor analysis for TVF

Hyaluronic Acid/Collagen Nanofiber Tubular Scaffolds Support Endothelial Cell Proliferation, Phenotypic Shape and Endothelialization

In this study, we designed and synthetized artificial vascular scaffolds based on nanofibers of collagen functionalized with hyaluronic acid (HA) in order to direct the phenotypic shape, proliferation, and complete endothelization of mouse primary aortic endothelial cells (PAECs). Layered tubular HA/collagen nanofibers were prepared using electrospinning and crosslinking process. The obtained scaffold is composed of a thin inner layer and a thick outer layer that structurally mimic the layer the intima and media layers of the native blood vessels, respectively. Compared with the pure tubular collagen nanofibers, the surface of HA functionalized collagen nanofibers has higher anisotropic wettability and mechanical flexibility. HA/collagen nanofibers can significantly promote the elongation, proliferation and phenotypic shape expression of PAECs. In vitro co-culture of mouse PAECs and their corresponding smooth muscle cells (SMCs) showed that the luminal endothelialization governs the biophysical integrity of the newly formed extracellular matrix (e.g., collagen and elastin fibers) and structural remodeling of SMCs. Furthermore, in vitro hemocompatibility assays indicated that HA/collagen nanofibers have no detectable degree of hemolysis and coagulation, suggesting their promise as engineered vascular implants.

Sex Differences in the Clinical Features and Outcomes of Patients with Acute Coronary Syndrome Treated with Two Generations (Absorb and Magmaris) of Bioresorbable Vascular Scaffolds

Background: Despite the developments in percutaneous coronary interventions (PCI), women are still more likely than men to have unfavorable outcomes after PCI performed in Acute Coronary Syndrome (ACS). The mechanisms of this phenomena are not fully understood. Potential benefits of bioresorbable scaffolds (BRS) may be particularly expressed in the female population. Nevertheless, the data available currently are inconsistent and limited. This study evaluated the gender-related differences in the short-term clinical outcomes in ACS patients treated with implantation of two generations of BRS (first generation, Absorb; second generation, Magmaris). Methods: The study was divided into two arms. To the first one, we qualified 160 patients with ACS treated with PCI who received 210 Absorb scaffolds. The second arm was composed of 193 patients with ACS who underwent PCI with Magmaris implantation. Results: There were no significant sex-related differences in primary endpoints (cardiovascular-death, myocardial infarction, in-stent thrombosis) or principal secondary endpoints (of target-lesion failure, scaffold restenosis, death from any reason, other cardiovascular events) in either generation of BRS in a 1-year follow-up. Conclusions: Both genders tended to have a similar outcome in routine clinical practice following BRS implantation due to ACS. The magnesium bioresorbable scaffold (Magmaris) early outcome seemed to be more favorable in comparison to the Absorb scaffold.

Coatings in Decellularized Vascular Scaffolds for the Establishment of a Functional Endothelium: A Scoping Review of Vascular Graft Refinement

Developments in tissue engineering techniques have allowed for the creation of biocompatible, non-immunogenic alternative vascular grafts through the decellularization of existing tissues. With an ever-growing number of patients requiring life-saving vascular bypass grafting surgeries, the production of functional small diameter decellularized vascular scaffolds has never been more important. However, current implementations of small diameter decellularized vascular grafts face numerous clinical challenges attributed to premature graft failure as a consequence of common failure mechanisms such as acute thrombogenesis and intimal hyperplasia resulting from insufficient endothelial coverage on the graft lumen. This review summarizes some of the surface modifying coating agents currently used to improve the re-endothelialization efficiency and endothelial cell persistence in decellularized vascular scaffolds that could be applied in producing a better patency small diameter vascular graft. A comprehensive search yielding 192 publications was conducted in the PubMed, Scopus, Web of Science, and Ovid electronic databases. Careful screening and removal of unrelated publications and duplicate entries resulted in a total of 16 publications, which were discussed in this review. Selected publications demonstrate that the utilization of surface coating agents can induce endothelial cell adhesion, migration, and proliferation therefore leads to increased re-endothelialization efficiency. Unfortunately, the large variance in methodologies complicates comparison of coating effects between studies. Thus far, coating decellularized tissue gave encouraging results. These developments in re-endothelialization could be incorporated in the fabrication of functional, off-the-shelf alternative small diameter vascular scaffolds.