Drug-eluting stent: a review and update

Drug Eluting Stents Below the Knee: Patency, Amputation-Rate, and Mortality-A Systematic Review of the Literature

BACKGROUND

Numerous meta-analyses and multicenter randomized controlled trials have demonstrated that drug-eluting stents (DES) offer superior outcomes in terms of primary patency and limb salvage compared to other endovascular modalities such as balloon angioplasty and bare metal stents. This review aims to systematically analyze the literature on the clinical outcomes of DES for the treatment of infrapopliteal arterial occlusions.

METHODS

This study is a systematic review. Comprehensive searches were conducted in the MEDLINE, EMBASE, Ovid, Cochrane, DAR, and BVS databases. Eligible studies were those that reported outcomes of DES in the treatment of infrapopliteal arterial disease, with no restrictions on time frame, publication status, or language. The primary outcome assessed was the primary patency of the stent, while secondary outcomes included the rates of re-occlusion and mortality.

RESULTS

A total of 27 studies involving 2470 patients were included in the analysis, in which 1191 patients come from prospective multicenter studies. The mean age of the participants was 73.4 years. Approximately, 50% of the patients had diabetes mellitus and/or chronic renal failure, and 33.3% had heart disease. The fibular artery was the most frequently affected by stenosis, involved in 50.2% of cases, followed by the anterior tibial artery in 34.6% of cases and the posterior tibial artery in 15.2% of cases. The average patency rate following DES treatment was 72.2% at 12 months. The rate of re-occlusion was 21.6%, and the mortality rate was 16.6%. However, due to the heterogeneity of the sample and incomplete data, it was not possible to draw definitive correlations between patency, amputation rates, and mortality.

CONCLUSION

This systematic review and analysis revealed significant limitations due to the heterogeneity of the sample and incomplete data, preventing a comprehensive stratification of the findings. As a result, we are not yet able to fully address the research questions posed. Further studies with extended follow-up periods are needed to standardize the treatment of infrapopliteal arterial occlusions and provide more definitive conclusions.Clinical ImpactThis review assessed the efficacy and safety of drug-eluting stents for below-the-knee lesions, showing promising patency and safety results. Their use in daily practice may aid in treating lesions prone to recoil and dissection after angioplasty. Despite some data inconsistencies, the findings remain encouraging. Drug-eluting stents demonstrated better outcomes than Bare-metal Stent, supporting their consideration in clinical practice for below-the-knee vascular treatment.

Metal-Organic Framework Thin Films as Drug Delivery Systems

Selective metal-organic frameworks (MOFs) have been studied as promising candidates for biomedical applications, especially as drug delivery systems due to their exceptional structural properties. This work reports the detailed methods to prepare an iron-containing MOF, MIL-88B(Fe), on functionalized gold and medical-grade stainless steel surfaces for drug delivery. We present a general procedure for preparing a novel drug carrier that can potentially be used as drug-eluting stent coatings.

AnXplore: a comprehensive fluid-structure interaction study of 101 intracranial aneurysms

Advances in computational fluid dynamics continuously extend the comprehension of aneurysm growth and rupture, intending to assist physicians in devising effective treatment strategies. While most studies have first modelled intracranial aneurysm walls as fully rigid with a focus on understanding blood flow characteristics, some researchers further introduced Fluid-Structure Interaction (FSI) and reported notable haemodynamic alterations for a few aneurysm cases when considering wall compliance. In this work, we explore further this research direction by studying 101 intracranial sidewall aneurysms, emphasizing the differences between rigid and deformable-wall simulations. The proposed dataset along with simulation parameters are shared for the sake of reproducibility. A wide range of haemodynamic patterns has been statistically analyzed with a particular focus on the impact of the wall modelling choice. Notable deviations in flow characteristics and commonly employed risk indicators are reported, particularly with near-dome blood recirculations being significantly impacted by the pulsating dynamics of the walls. This leads to substantial fluctuations in the sac-averaged oscillatory shear index, ranging from -36% to +674% of the standard rigid-wall value. Going a step further, haemodynamics obtained when simulating a flow-diverter stent modelled in conjunction with FSI are showcased for the first time, revealing a 73% increase in systolic sac-average velocity for the compliant-wall setting compared to its rigid counterpart. This last finding demonstrates the decisive impact that FSI modelling can have in predicting treatment outcomes.

Pro-endothelialization of nitinol alloy cardiovascular stents enhanced by the programmed assembly of exosomes and endothelial affinity peptide

Stent implantation is one of the most effective methods for the treatment of atherosclerosis. Nitinol stent is a type of stent with good biocompatibility and relatively mature development; however, it cannot effectively achieve long-term anticoagulation and early endothelialization. In this study, nitinol surfaces with the programmed assembly of heparin, exosomes from endothelial cells, and endothelial affinity peptide (REDV) were fabricated through layer-by-layer assembly technology and click-chemistry, and then exosomes/REDV-modified nitinol interface (ACC-Exo-REDV) was prepared. ACC-Exo-REDV could promote the rapid proliferation and adhesion of endothelial cells and achieve anticoagulant function in the blood. Besides, ACC-Exo-REDV had excellent anti-inflammatory properties and played a positive role in the transformation of macrophage from the pro-inflammatory to anti-inflammatory phenotype. Ex vivo and in vivo experiments demonstrated the effectiveness of ACC-Exo-REDV in preventing thrombosis and hyperplasia formation. Hence, the programmed assembly of exosome interface could contribute to endothelialization and have potential application on the cardiovascular surface modification to prevent stent thrombosis and restenosis.

Future of Endovascular and Surgical Treatments of Atherosclerotic Intracranial Stenosis

Intracranial atherosclerotic disease and resultant intracranial stenosis is a global leading cause of stroke, and poses an ongoing treatment challenge. Among patients with intracranial stenosis, those with hemodynamic compromise are at high risk for recurrent stroke despite medical therapy and risk factor modification. Revascularization of the hypoperfused territory is the most plausible treatment strategy for these high-risk patients, yet surgical and endovascular therapies have not yet shown to be sufficiently safe and effective in randomized controlled trials. Advances in diagnostic and therapeutic technologies have led to a resurgence of interest in surgical and endovascular treatment strategies, with a growing body of evidence to support their further evaluation in the treatment of select patient populations. This review outlines the current and emerging endovascular and surgical treatments and highlights promising future management strategies.

Cardiovascular Tissue Engineering Models for Atherosclerosis Treatment Development

In the early years of tissue engineering, scientists focused on the generation of healthy-like tissues and organs to replace diseased tissue areas with the aim of filling the gap between organ demands and actual organ donations. Over time, the realization has set in that there is an additional large unmet need for suitable disease models to study their progression and to test and refine different treatment approaches. Increasingly, researchers have turned to tissue engineering to address this need for controllable translational disease models. We review existing and potential uses of tissue-engineered disease models in cardiovascular research and suggest guidelines for generating adequate disease models, aimed both at studying disease progression mechanisms and supporting the development of dedicated drug-delivery therapies. This involves the discussion of different requirements for disease models to test drugs, nanoparticles, and drug-eluting devices. In addition to realistic cellular composition, the different mechanical and structural properties that are needed to simulate pathological reality are addressed.

Balloon-mounting stent for intracranial arterial stenosis: A comprehensive and comparative systematic review and meta-analysis

INTRODUCTION

As one of the major causes of acute ischemic stroke, intracranial arterial stenosis necessitates an intervention that ranges from medical treatment to balloon angioplasty and stenting. Self-expandable stents (SES) and balloon-mounted stents (BMS) are two types of stents and their comparative efficacy and safety for intracranial stenosis are not well established.

METHODS

Studies that investigate balloon-mounted stenting for intracranial stenosis were extracted from PubMed, Scopus, and Cochrane library. We sought to gather data on the success rate, change in mean arterial stenosis, and complications such as minor and major stroke and death (MMD), symptomatic intracranial hemorrhage, myocardial infarction, all-cause mortality, and in-stent re-stenosis.

RESULTS

3049 patients from 35 studies were included in this study. 20 studies investigated BMS alone and others compared BMS with SES. BMS was significantly more effective in reducing the degree of stenosis compared to SES (Difference in mean -5.953, CI 95% -7.727 to -4.179), had less complications compared to SES such as MMD (8.5% vs. 11.2%) and less in-stent re-stenosis (18.6% vs. 19.6%), but patients with SES experienced a lower rate of all-cause mortality(1.7% vs. 4.1%).

CONCLUSION

Intracranial stenting with BMS is more effective in reducing the degree of stenosis and has lower rates of complications when compared to SES.

A review on the treatment of intimal hyperplasia with perivascular medical devices: role of mechanical factors and drug release kinetics

INTRODUCTION

Intimal hyperplasia (IH) is a significant factor limiting the success of revascularization surgery for blood flow restoration. IH results from a foreign body response and mechanical disparity that involves complex biochemical reactions resulting in graft failure. The available treatment option utilizes either different pharmacological interventions or mechanical support to the vascular grafts with limited success.

AREAS COVERED

This review explains the pathophysiology of IH, responsible mechanical and biological factors, and treatment options, emphasizing perivascular devices. They are designed to provide mechanical support and pharmacology actions. The perivascular drug delivery concept has successfully demonstrated efficacy in various animal studies. Accurate projections of drug release mechanisms using mathematical modeling could be used to formulate prolonged drug elution devices. Numerical modeling aspects for the prediction of design outcomes have been given due importance that fulfills the unmet clinical need for better patient care.

EXPERT OPINION

IH could be effectively prevented by simultaneous mechanical scaffolding and sustained local drug delivery. Future perivascular medical devices could be designed to integrate these essential features. Numerical modeling for device performance prediction should be utilized in the development of next-generation perivascular devices.

Thirty-Day Outcomes of Resolute Onyx Stent for Symptomatic Intracranial Stenosis: A Multicenter Propensity Score-Matched Comparison With Stenting Versus Aggressive Medical Management for Preventing Recurrent Stroke in Intracranial Stenosis Trial

BACKGROUND

Symptomatic intracranial atherosclerotic disease (sICAD) is estimated to cause 10% of strokes annually in the United States. However, treatment remains a challenge with several different stenting options studied in the past with unfavorable results.

OBJECTIVE

To report the 30-day stroke and/or death rate associated with intracranial stent placement for sICAD using Resolute Onyx Zotarolimus-Eluting Stent (RO-ZES) and provide a comparison with the results of Stenting Versus Aggressive Medical Management for Preventing Recurrent Stroke in Intracranial Stenosis (SAMMPRIS) trial.

METHODS

Prospectively maintained databases across 8 stroke centers were used to identify adult patients treated with RO-ZES for sICAD between January 2019 and December 2021. Primary end point was composite of 30-day stroke, intracerebral hemorrhage, and/or death. Propensity score matching was performed using age, hypertension, lipid disorder, cigarette smoking, and symptomatic target vessel to create a matched group for comparison between RO-ZES and the SAMMPRIS medical management and treatment groups (SAMMPRIS percutaneous angioplasty and stenting [S-PTAS]).

RESULTS

A total of 132 patients met the inclusion criteria for analysis (mean age: 64.2 years). Mean severity of stenosis was 81.4% (±11.4%). A total of 4 (3.03%) stroke and/or deaths were reported within 30 days of treatment in the RO-ZES group compared with 6.6% in the SAMMPRIS medical management group (OR [odds ratio] 2.26, 95% CI 0.7-9.56, P = .22) and 15.6% in the S-PTAS group (OR 5.9, 95% CI 2.04-23.4, P < .001). Propensity score match analysis of 115 patients in each group demonstrated 30-day stroke and/or death rate of 2.6% in the RO-ZES group and 15.6% in the S-PTAS group (OR 6.88, 95% CI 1.92-37.54, P < .001).

CONCLUSION

Patients treated with RO-ZES had a relatively low 30-day stroke and/or death rate compared with the S-PTAS group. Further large-scale prospective studies are warranted to evaluate the safety and efficacy of RO-ZES for the treatment of sICAD.

Evaluation of rs1748195 ANGPTL3 gene polymorphism in patients with angiographic coronary artery disease compared to healthy individuals

SUBJECT

The Angiopoietin-like 3 (ANGPTL3) gene has been reported to be associated with cardiovascular risk. This study is designed to compare the genetic variant (rs1748195) of the ANGPTL3 gene and the presence of a coronary artery occlusion of >50% in Iranian nation.

METHOD

In this study, 184 patients underwent angiography and 317 healthy individuals were evaluated for polymorphism of rs1748195 the ANGPTL3 gene using Tetra-ARMs PCR. Coronary patients who experience angiography were categorized into two groups: 54 patients who had an angiography indication for the first time and coronary occlusion was <50% (Angio-) and 134 patients who formerly underwent coronary stent implanting at least 1 month before with coronary occlusion of ≥50% that again have an angiography indication (Angio+). In addition, individuals with angio+ are categorized in two groups: (1) non-in-stent restenosis (NISR); patient with a patent stent (N = 92). (2) in-stent restenosis (ISR); in-stent stenosis >50% (N = 42).

RESULT

The fundamental of characteristics of our study design population was categorized based on undergoing angiography or not. In the present study, we investigated that the CC genotype, and also the A allele corresponding to rs1748195 at the ANGPTL3 gene loci, was associated with negative angiogram and directly related to the risk of coronary occlusion >50%. In contrast, this result was not significant in genotypes of ANGPTL3 between non-ISR and ISR groups.

CONCLUSION

The outcomes of this study showed that rs1748195 polymorphism at the ANGPTL3 gene loci is associated with an elevated risk for the existence of a coronary occlusion of >50%.

Elimination of enzymes catalysis compartmentalization enhancing taxadiene production in Saccharomyces cerevisiae

Taxadiene is an important precursor in taxol biosynthesis pathway, but its biosynthesis in eukaryotic cell factories is limited, which seriously hinders the biosynthesis of taxol. In this study, it is found that there was the catalysis compartmentalization between two key exogenous enzymes of geranylgeranyl pyrophosphate synthase and taxadiene synthase (TS) for taxadiene synthesis progress, due to their different subcellular localization. Firstly, the enzyme-catalysis compartmentalization was overcome by means of the intracellular relocation strategies of taxadiene synthase, including N-terminal truncation of taxadiene synthase and enzyme fusion of GGPPS-TS. With the help of two strategies for enzyme relocation, the taxadiene yield was increased by 21% and 54% respectively, among them the GGPPS-TS fusion enzyme is more effective. Further, the expression of GGPPS-TS fusion enzyme was improved via the multi-copy plasmid, resulting that the taxadiene titer was increased by 38% to 21.8 mg/L at shake-flask level. Finally, the maximum taxadiene titer of 184.2 mg/L was achieved by optimization of the fed-batch fermentation conditions in 3 L bioreactor, which is the highest reported titer of taxadiene biosynthesis accomplished in eukaryotic microbes. This study provides a successful example for improving biosynthesis of complex natural products by solving the critical problem of multistep enzymes catalysis compartmentalization.

Characteristics of Phospholipid-Immunosuppressant-Antioxidant Mixed Langmuir-Blodgett Films

Hemocompatibility is one of the major criteria for the successful cardiovascular applicability of novel biomaterials. In this context, monolayers of certain biomolecules can be used to improve surface biocompatibility. To this end, biocoatings incorporating a phospholipid (1,2-dioleoyl-sn-glycero-3-phosphocholine, DOPC), an immunosuppressant (cyclosporine A, CsA), and an antioxidant material (lauryl gallate, LG) were fabricated by depositing Langmuir films onto gold or mica substrates using the Langmuir-Blodgett (LB) technique. These LB monolayers were thoroughly characterized by means of quartz crystal microbalance (QCM), atomic force microscopy (AFM), cyclic voltammetry (CV), and contact angle (CA) measurements. The obtained results indicate that the properties of these LB films are modulated by the monolayer composition. The presence of LG in the three-component systems (DOPC-CsA-LG) increases the molecular packing and the surface coverage of the substrate, which affects the wettability of the biocoating. From the different compositions studied here, we conclude that DOPC-CsA-LG monolayers with a DOPC/CsA ratio of 1:1 and LG molar fractions of 0.50 and 0.75 exhibit improved surface biocompatible characteristics. These results open up new perspectives on our knowledge and better understanding of phenomena at the biomaterial/host interface.

Monodispersed Sirolimus-Loaded PLGA Microspheres with a Controlled Degree of Drug–Polymer Phase Separation for Drug-Coated Implantable Medical Devices and Subcutaneous Injection

Monodispersed sirolimus (SRL)-loaded poly(lactic-co-glycolic acid) microspheres with a diameter of 1.8, 3.8, and 8.5 μm were produced by high-throughput microfluidic step emulsification—solvent evaporation using single crystal silicon chips consisted of 540–1710 terraced microchannels with a depth of 2, 4, or 5 μm arranged in 10 parallel arrays. Uniform sized droplets were generated over 25 h across all channels. Nearly 15% of the total drug was released by the initial burst release during an accelerated drug release testing performed at 37 °C using a hydrotropic solution containing 5.8 M N,N-diethylnicotinamide. After 24 h, 71% of the drug was still entrapped in the particles. The internal morphology of microspheres was investigated by fluorescence microscopy using Nile red as a selective fluorescent stain with higher binding affinity toward SRL. By increasing the drug loading from 33 to 50 wt %, the particle morphology evolved from homogeneous microspheres, in which the drug and polymer were perfectly mixed, to patchy particles, with amorphous drug patches embedded within a polymer matrix to anisotropic patchy Janus particles. Janus particles with fully segregated drug and polymer regions were achieved by pre-saturating the aqueous phase with the organic solvent, which decreased the rate of solvent evaporation and allowed enough time for complete phase separation. This approach to manufacturing drug-loaded monodisperse microparticles can enable the development of more effective implantable drug-delivery devices and improved methods for subcutaneous drug administration, which can lead to better therapeutic treatments.

Flexible 3D Nanonetworked Silica Film as a Polymer-Free Drug-Eluting Stent Platform to Effectively Suppress Tissue Hyperplasia in Rat Esophagus

Loading and eluting drugs on self-expandable metallic stents (SEMSs) can be challenging in terms of fabrication, mechanical stability, and therapeutic effects. In this study, a flexible 3D nanonetworked silica film (NSF) capable of withstanding mechanical stress during dynamic expansion is constructed to function as a drug delivery platform on an entire SEMS surface. Despite covering a broad curved area, the synthesized NSF is defect-free and thin enough to increase the stent strut diameter (110 µm) by only 0.4 percent (110.45 µm). The hydrophobic modification of the surface enables loading of 4.7 times the sirolimus (SRL) concentration in NSF than Cypher, polymer-coated commercial stent, which is based on the same thickness of coating layer. Furthermore, SRL-loaded NSF exhibits a twofold delay in release compared to the control group without NSF. The SRL-loaded NSF SEMS significantly suppresses stent-induced tissue hyperplasia than the control SEMS in the rat esophagus (all variables, p < 0.05). Thus, the developed NSF is a promising polymer-free drug delivery platform to efficiently treat esophageal stricture.

Progress in drug-delivery systems in cardiovascular applications: stents, balloons and nanoencapsulation

Drug-delivery systems in cardiovascular applications regularly include the use of drug-eluting stents and drug-coated balloons to ensure sufficient drug transfer and efficacy in the treatment of cardiovascular diseases. In addition to the delivery of antiproliferative drugs, the use of growth factors, genetic materials, hormones and signaling molecules has led to the development of different nanoencapsulation techniques for targeted drug delivery. The review will cover drug delivery and coating mechanisms in current drug-eluting stents and drug-coated balloons, novel innovations in drug-eluting stent technologies and drug encapsulation in nanocarriers for delivery in vascular diseases. Newer technologies and advances in nanoencapsulation techniques, such as the use of liposomes, nanogels and layer-by-layer coating to deliver therapeutics in the cardiovascular space, will be highlighted.

Bioabsorbable metal zinc differentially affects mitochondria in vascular endothelial and smooth muscle cells

Zinc is an essential trace element having various structural, catalytic and regulatory interactions with an estimated 3000 proteins. Zinc has drawn recent attention for its use, both as pure metal and alloyed, in arterial stents due to its biodegradability, biocompatibility, and low corrosion rates. Previous studies have demonstrated that zinc metal implants prevent the development of neointimal hyperplasia, which is a common cause of restenosis following coronary intervention. This suppression appears to be smooth muscle cell-specific, as reendothelization of the neointima is not inhibited. To better understand the basis of zinc's differential effects on rat aortic smooth muscle (RASMC) versus endothelial (RAENDO) cells, we conducted a transcriptomic analysis of both cell types following one-week continuous treatment with 5 µM or 50 µM zinc. This analysis indicated that genes whose protein products regulate mitochondrial functions, including oxidative phosphorylation and fusion/fission, are differentially affected by zinc in the two cell types. To better understand this, we performed Seahorse metabolic flux assays and quantitative imaging of mitochondrial networks in both cell types. Zinc treatment differently affected energy metabolism and mitochondrial structure/function in the two cell types. For example, both basal and maximal oxygen consumption rates were increased by zinc in RASMC but not in RAENDO. Zinc treatment increased apparent mitochondrial fusion in RASMC cells but increased mitochondrial fission in RAENDO cells. These results provide some insight into the mechanisms by which zinc treatment differently affects the two cell types and this information is important for understanding the role of zinc treatment in vascular cells and improving its use in biodegradable metal implants.

Computational analysis of the effects of geometric irregularities on the interaction of an additively manufactured 316L stainless steel stent and a coronary artery

Customized additively manufactured (laser powder bed fused (L-PBF)) stents could improve the treatment of complex lesions by enhancing stent-artery conformity. However, geometric irregularities inherent for L-PBF stents are expected to influence not only their mechanical behavior but also their interaction with the artery. In this study, the influence of geometrical irregularities on stent-artery interaction is evaluated within a numerical framework. Thus, computed arterial stresses induced by a reconstructed L-PBF stent model are compared to those induced by the intended stent model (also representing a stent geometry obtained from conventional manufacturing processes) and a modified CAD stent model that accounts for the increased strut thickness inherent for L-PBF stents. It was found that, similar to conventionally manufactured stents, arterial stresses are initially related to the basic stent design/topology, with the highest stresses occurring at the indentations of the stent struts. Compared to the stent CAD model, the L-PBF stent induces distinctly higher and more maximum volume stresses within the plaque and the arterial wall. In return, the modified CAD model overestimates the arterial stresses induced by the L-PBF stent due to its homogeneously increased strut thickness and thus its homogeneously increased geometric stiffness compared with the L-PBF stent. Therefore, the L-PBF-induced geometric irregularities must be explicitly considered when evaluating the L-PBF stent-induced stresses because the intended stent CAD model underestimates the arterial stresses, whereas the modified CAD model overestimates them. The arterial stresses induced by the L-PBF stent were still within the range of values reported for conventional stents in literature, suggesting that the use of L-PBF stents is conceivable in principle. However, because geometric irregularities, such as protruding features from the stent surface, could potentially damage the artery or lead to premature stent failure, further improvement of L-PBF stents is essential.

The Research Progress of Taxol in Taxus

BACKGROUND

Taxus is a valuable woody species with important medicinal value. The bark of Taxus can produce taxol, a natural antineoplastic drug that is widely used in the treatment of breast, ovarian and lung cancers. However, the low content of taxol in the bark of Taxus can not meet the growing clinical demands, so the current research aims at finding ways to increase taxol production.

OBJECTIVE

In this review, the research progress of taxol including the factors affecting the taxol content, biosynthesis pathway of taxol, production of taxol in vitro and the application of multi-omics approaches in Taxus as well as future research prospects will be discussed.

RESULTS

The taxol content is not only dependent on the species, age and tissues but is also affected by light, moisture levels, temperature, soil fertility and microbes. Most of the enzymes in the taxol biosynthesis pathway have been identified and characterized. Total chemical synthesis, semi-synthesis, plant cell culture and biosynthesis in endophytic fungi have been explored to product taxol. Multi-omics have been used to study Taxus and taxol.

CONCLUSION

Further efforts in the identification of unknown enzymes in the taxol biosynthesis pathway, establishment of the genetic transformation system in Taxus and the regulatory mechanism of taxol biosynthesis and Taxus cell growth will play a significant role in improving the yield of taxol in Taxus cells and plants.

Pharmaceutical Development of 5-Fluorouracil-Eluting Stents for the Potential Treatment of Gastrointestinal Cancers and Related Obstructions

BACKGROUND

Drug-eluting gastrointestinal (GI) stents are emerging as promising platforms for the treatment of GI cancers and provide the combined advantages of mechanical support to prevent lumen occlusion and as a reservoir for localized drug delivery to tumors. Therefore, in this work we present a detailed quality assurance study of 5-fluorouracil (5FU) drug-eluting stents (DESs) as potential candidates for the treatment of obstructive GI cancers.

METHODS

The 5FU DESs were fabricated via a simple two-step sequential dip-coating process of commercial GI self-expanding nitinol stents with a 5FU-loaded polyurethane basecoat and a drug-free protective poly(ethylene-co-vinyl acetate) topcoat. The drug loading, content uniformity and drug stability were determined using a validated high-performance liquid chromatography (HPLC) method, which is also recommended in the United States Pharmacopeia. In vitro drug release studies were performed in phosphate buffered saline to determine the drug releasing properties of the two 5FU-loaded stents. Gas chromatography (GC) and HPLC were employed to determine total residual tetrahydrofuran and N,N-dimethylformamide in the stents remaining from the manufacturing process. Sterilization of the stents was performed using gamma radiation and stability testing was carried out for 3 months.

RESULTS

The drug loading analysis revealed excellent uniformity in the distribution of 5FU between and within individual stents. Determination of drug stability in the biorelevant release media confirmed that 5FU remains stable over 100 d. In vitro drug release studies from the stents revealed sustained release of 5FU across two different time scales (161 and 30 d), and mathematical modeling of drug release profiles revealed a diffusion-controlled mechanism for the sustained 5FU release. GC and HPLC analysis revealed that the daily residual solvent leached from the stents was below the United States (US) Food and Drug Administration (FDA) guidelines, and therefore, unlikely to cause localized/systemic toxicities. Sterilization of the stents with gamma radiation and accelerated stability tests over a period of 3 months revealed no significant effect on the stability or in vitro release of 5FU.

CONCLUSION

Our results demonstrate that the 5FU DESs meet relevant quality standards and display favourable drug release characteristics for the potential treatment of GI cancers and related obstructions.

Polyphosphazenes as Adjuvants for Animal Vaccines and Other Medical Applications

Polyphosphazenes are a class of experimental adjuvants that have shown great versatility as vaccine adjuvants in many animal species ranging from laboratory rodents to large animal species. Their adjuvant activity has shown promising results with numerous viral and bacterial antigens, as well as with crude and purified antigens. Vaccines adjuvanted with polyphosphazenes can be delivered via systemic and mucosal administration including respiratory, oral, rectal, and intravaginal routes. Polyphosphazenes can be used in combination with other adjuvants, further enhancing immune responses to antigens. The mechanisms of action of polyphosphazenes have not fully been defined, but several systematic studies have suggested that they act primarily by activating innate immunity. In the present review, we will highlight progress in the development of polyphosphazenes as adjuvants in animals and their other medical applications.

Comparison of coronary artery bypass graft versus drug-eluting stents in dialysis patients: an updated systemic review and meta-analysis

INTRODUCTION

As percutaneous coronary intervention (PCI) technologies have been far improved, we hence conducted an updated systemic review and meta-analysis to determine the comparability between coronary artery bypass graft (CABG) and PCI with drug-eluting stent (DES) in ESRD patients.

METHODS

We comprehensively searched the databases of MEDLINE, EMBASE, PUBMED and the Cochrane from inception to January 2020. Included studies were published observational studies that compared the risk of cardiovascular outcomes among dialysis patients with CABG and DES. Data from each study were combined using the random-effects, generic inverse variance method of DerSimonian and Laird to calculate risk ratios and 95% confidence intervals. Subgroup analyses and meta-regression were performed to explore heterogeneity.

RESULTS

Thirteen studies were included in this analysis, involving total 56 422 (CABG 21 740 and PCI 34 682). Compared with DES, our study demonstrated CABG had higher 30-day mortality [odds ratio (OR) 3.85, P = 0.009] but lower cardiac mortality (OR 0.78, P < 0.001), myocardial infarction (OR 0.5, P < 0.001) and repeat revascularization (OR 0.35, P < 0.001). No statistical differences were found between CABG and DES for long-term mortality (OR 0.92, P = 0.055), composite outcomes (OR 0.88, P = 0.112) and stroke (OR 1.49, P = 0.457). Meta-regression suggested diabetes and the presence of left main coronary artery disease as an effect modifier of long-term mortality.

CONCLUSION

PCI with DES shared similar long-term mortality, composite outcomes and stroke outcomes to CABG among dialysis patients but still was associated with an improved 30-day survival. However, CABG had better rates of myocardial infarction, repeat revascularization and cardiac mortality.

Characterization of a Sandwich PLGA-Gallic Acid-PLGA Coating on Mg Alloy ZK60 for Bioresorbable Coronary Artery Stents

Absorbable magnesium stents have become alternatives for treating restenosis owing to their better mechanical properties than those of bioabsorbable polymer stents. However, without modification, magnesium alloys cannot provide the proper degradation rate required to match the vascular reform speed. Gallic acid is a phenolic acid with attractive biological functions, including anti-inflammation, promotion of endothelial cell proliferation, and inhibition of smooth muscle cell growth. Thus, in the present work, a small-molecule eluting coating is designed using a sandwich-like configuration with a gallic acid layer enclosed between poly (d,l-lactide-co-glycolide) layers. This coating was deposited on ZK60 substrate, a magnesium alloy that is used to fabricate bioresorbable coronary artery stents. Electrochemical analysis showed that the corrosion rate of the specimen was ~2000 times lower than that of the bare counterpart. The released gallic acid molecules from sandwich coating inhibit oxidation by capturing free radicals, selectively promote the proliferation of endothelial cells, and inhibit smooth muscle cell growth. In a cell migration assay, sandwich coating delayed wound closure in smooth muscle cells. The sandwich coating not only improved the corrosion resistance but also promoted endothelialization, and it thus has great potential for the development of functional vascular stents that prevent late-stent restenosis.

Treatment of a heart base tumor and chylothorax with endovascular stent, stereotactic body radiation therapy, and a tyrosine kinase inhibitor in a dog

An 8-year-old 28-kg male castrated rough collie was evaluated for persistent chylothorax secondary to right atrial mass. Cardiac ultrasound and computed tomography revealed a right atrial intra- and extraluminal mass with partial obstruction of the cranial vena cava and secondary chylothorax. Vascular stent placement was elected to alleviate cranial vena cava obstruction and secondary chylothorax. An 18 mm × 180 mm self-expanding stent was deployed in the region of the stricture, spanning the cranial vena cava and right atrium. An intrathoracic drainage catheter and subcutaneous port were placed within the right hemithorax, and antiplatelet therapy was initiated. Four weeks later, the dog underwent stereotactic body radiation therapy. Three months following treatment, the dog was diagnosed with supraventricular tachycardia and received antiarrhythmic therapy and antiangiogenic/antiproliferative medication (Palladia™). Subsequent evaluations confirmed the resolution of arrhythmia and pleural effusion. Combined vascular stent placement and stereotactic body radiation therapy for the treatment of a right atrial intraluminal and extraluminal mass leading to cranial vena cava compression and subsequent chylothorax may lead to long-term survival. A good outcome was achieved in this patient due to resolution of pleural effusion, as well as cytoreduction and presumably delayed progression of tumor growth.

Drug-Eluting Stents and Balloons-Materials, Structure Designs, and Coating Techniques: A Review

Controlled drug delivery is a matter of interest to numerous scientists from various domains, as well as an essential issue for society as a whole. In the treatment of many diseases, it is crucial to control the dosing of a drug for a long time and thus maintain its optimal concentration in the tissue. Heart diseases are particularly important in this aspect. One such disease is an obstructive arterial disease affecting millions of people around the world. In recent years, stents and balloon catheters have reached a significant position in the treatment of this condition. Balloon catheters are also successfully used to manage tear ducts, paranasal sinuses, or salivary glands disorders. Modern technology is continually striving to improve the results of previous generations of stents and balloon catheters by refining their design, structure, and constituent materials. These advances result in the development of both successive models of drug-eluting stents (DES) and drug-eluting balloons (DEB). This paper presents milestones in the development of DES and DEB, which are a significant option in the treatment of coronary artery diseases. This report reviews the works related to achievements in construction designs and materials, as well as preparation technologies, of DES and DEB. Special attention was paid to the polymeric biodegradable materials used in the production of the above-mentioned devices. Information was also collected on the various methods of producing drug release coatings and their effectiveness in releasing the active substance.

Nanostructured Titanium for Improved Endothelial Biocompatibility and Reduced Platelet Adhesion in Stent Applications

Although coronary stents have improved the early and long-term consequences of arterial lesions, the prevention of restenosis and late stent thrombosis is key to prevent a new obstruction of the vessel. Here we aimed at improving the tissue response to stents through surface modification. For that purpose, we used two different approaches, the use of nanostructuration by electrochemical anodization and the addition of a quercitrin (QR) coating to the Ti surface. Four surfaces (Ti, NN, TiQR and NNQR) were characterized by atomic force microscopy, scanning electronic microscopy and contact angle analysis and QR content was evaluated by fluorescent staining. Cell adhesion, cytotoxicity, metabolic activity and nitric oxide (NO) production was evaluated on primary human umbilical cord endothelial cells (HUVECs). Platelet adhesion, hemolysis rate and Staphylococcus epidermidis CECT 4184 adhesion at 30 min were analyzed. Nanostructuration induced an increase on surface roughness, and QR coating decreased the contact angle. All surfaces were biocompatible, with no hemolysis rate and lower platelet adhesion was found in NN surfaces. Finally, S. epidermidis adhesion was lower on TiQR surfaces compared to Ti. In conclusion, our results suggest that NN structuration could improve biocompatibility of bare metal stents on endothelial cells and reduce platelet adhesion. Moreover, QR coating could reduce bacterial adhesion.

Risk Factors for the Development of Carotid Artery In-Stent Restenosis: Multivariable Analysis

OBJECTIVES

In this study, we evaluated the relationship between certain patient and stent characteristics with regards to their association with the development of restenosis.

BACKGROUND

Carotid artery stenosis is a major cause of stroke. Carotid artery stenting is an FDA approved method for the treatment of carotid artery stenosis. However, carotid artery stenting has been fraught with lumen loss and in-stent restenosis. The literature is limited in regard to variables affecting long term patency after carotid artery stenting.

METHODS

This is a retrospective chart review study investigating the variables affecting the long term patency in patients who underwent carotid artery stenting. The data was analyzed using a Multivariable logistic regression models.

RESULTS

148 patients were included in the study. 123 patients did not develop signs of restenosis after 1 year, while 25 patients developed restenosis defined on annual follow up carotid duplex ultrasound. The odds ratio of developing restenosis for current/former smokers vs. never smokers was 10.1 (p = 0.018), closed vs. open cell design stents was 12.5 (p = 0.008). The odds ratio of developing restenosis decreases by 50.1% for every 1 mm increase in the diameter (p = 0.021). Data was collected and reanalyzed at 3 years to look for any changes in risk factors that become significant which showed that the chance of developing restenosis increases by 11.2% for every 1 mm increase in the length of the stent.

CONCLUSIONS

Our data suggest that the risk of developing restenosis is elevated in those with a history of previous/current tobacco use; those treated with closed-cell as opposed to open-cell design. We also found that restenosis is positively associated with stent length and inversely associated with stent diameter. The aforementioned factors should be considered in the management of carotid artery stenosis.

Management of cardiovascular disease in patients with systemic lupus erythematosus

INTRODUCTION

SLE is increasingly recognized as an important risk factor for cardiovascular disease. Premature CAD and several other cardiac manifestations are resulting in significant morbidity and premature death among young and older adults. There is a considerable unmet need for developing specific guidelines toward the primary and secondary prevention of cardiovascular disease in SLE patients.

AREAS COVERED

The authors describe the prevalence of various cardiovascular manifestations, associated with traditional and lupus-specific risk factors. They summarize the evidence behind various nonpharmacological and pharmacological options such as cardiac medications, antimalarials, anti-inflammatory, and immunosuppressant medications.

EXPERT OPINION

There is considerable literature claiming that the traditional Framingham score used to calculate the risk in the general population would not clearly predict the 10-year risk among SLE patients as they do not include lupus-specific risk factors such as accelerated inflammation, immunometabolic changes, thrombosis, vasospasm, vasculitis, and endothelial dysfunction into account. Identifying potential risk factors among SLE patients and treating hyperlipidemia regardless of their risk scores may be the first step in reducing mortality. Blocking lupus-specific inflammatory pathways by targeting validated biomarkers of pathogenesis has great future potential and more studies are needed on their cardiovascular benefits.

The effect of intrinsic characteristics on mechanical properties of poly(l-lactic acid) bioresorbable vascular stents

Poly(L-lactic acid) (PLLA) is currently the bioresorbable polymer of choice for vascular stents with its superior biocompatibility and mechanical properties. However, it is still difficult to enhance the radial supporting capacity of PLLA stents without increasing the strut thickness. In this study, the performance of laser-cut thin-strut stents from two groups of PLLA tubes are investigated. We considered two groups of PLLA tubes. Group 1 indicates the longitudinally stretched from original 150-μm-thick tubes, and Group 2 indicates the directly thinned from original 150-μm-thick tubes. Three stages of mechanical tests were conducted in this study, which are defined as tensile tests of dog-bone specimens, radial loading tests of tubes and radial loading tests of stents. The results suggest that Group 2 has higher radial supporting capacity than Group 1 with the same wall thickness. This work serves as a basis for manufacturing thin-strut stents with sufficient radial supporting capacity.

Pregnancy and cardiac interventions: What are the optimal management options?

Cardiac disease is the leading cause of maternal mortality in the United Kingdom. Major causes of cardiac death in pregnant women include cardiomyopathies, myocardial infarction, ischemic heart disease, and aortic dissection. Uncorrected congenital heart disease and women who have had corrective or palliative surgery may have complicated pregnancies as well. Some women with significant cardiac disease are unable to meet the increased physiological demands of pregnancy. Of these, those who do not respond to medical treatment may require surgical correction such as coronary artery bypass grafting. The risk of cardiac operations for pregnant women is similar to that for nonpregnant women but the fetal mortality rate remains high. Contributing factors to high fetal mortality rates include timing, urgency of operation, and the fetal/fetoplacental response to cardiopulmonary bypass. The aim of this review is to summarize current evidence in utilizing the different management approaches of cardiac issues during pregnancy.

Combinatorial therapy of sirolimus and heparin by nanocarrier inhibits restenosis after balloon angioplasty ex vivo

Aim: To develop poly(lactide-co-glycolide)-graft-polyethylenimine (PgP) as a dual drug-delivery carrier for sirolimus (SR) and heparin (Hep) to inhibit restenosis after balloon angioplasty. Materials & methods: SR was loaded in the hydrophobic core and negatively charged Hep complexed with the positively charged hydrophilic shell of PgP. SR- and Hep-loaded PgP was tested on rat aortic smooth muscle cells in vitro and injured porcine coronary arteries after balloon angioplasty ex vivo. Results & conclusion: SR and Hep loading efficiency in PgP were approximately 37 and 82%, respectively. SR- and Hep-loaded PgP treatment decreased smooth muscle cell proliferation up to 14 days post-treatment and decreased proliferation, collagen deposition and neointimal thickness and increased patency in porcine coronary arteries after balloon angioplasty ex vivo.

A Review of the Ultrathin Orsiro Biodegradable Polymer Drug-eluting Stent in the Treatment of Coronary Artery Disease

Drug-eluting stents (DES) have revolutionised the treatment of coronary artery disease (CAD) in patients undergoing percutaneous coronary intervention. In recent years, there has been a focus on a new generation of DES, such as biodegradable polymer DES (BP-DES). This novel stent platform was developed with the hope of eliminating the risk of very late stent thrombosis associated with the current gold-standard durable polymer DES (DP-DES). Ultrathin Orsiro BP-DES (Biotronik, Bülach, Switzerland) are based on a cobalt-chromium stent platform that is coated with a bioresorbable polymer coating containing sirolimus. These devices have one of the thinnest struts available in the current market and have the theoretical benefit of reducing a chronic inflammatory response in the vessel wall. In 2019, the United States Food and Drug Administration (FDA) approved the use of Orsiro BP-DES in patients with CAD based on promising results in recent landmark trials, such as BIOFLOW V and BIOSTEMI. The aim of the present review article was to discuss the history of stent technology and the continued opportunities for improvements, focusing on the potential benefits of Orsiro BP-DES.

Is There a Safety Concern for Drug-Coated Balloons in Peripheral Arterial Disease?

PURPOSE OF REVIEW

Drug-coated balloons (DEB) and drug-eluting stents (DES) emerged as a tool to aid in lowering the rates of neointimal hyperplasia and target lesion restenosis following endovascular peripheral arterial disease (PAD) interventions.

RECENT FINDINGS

Although the initial trials comparing these devices with non-drug balloons and stents showed favorable results, more recent data raised concerns regarding the mid to long-term safety of these devices. In this review, we will discuss the evolution of endovascular therapy for PAD, with highlights regarding the recent debates on the long-term safety of the drug-coated devices for treatment of PAD.

Emerging technologies in pediatric gynecology: new paradigms in women's health care

PURPOSE OF REVIEW

The current review highlights the complexity of the pediatric and adolescent gynecology subspecialty as well as the recent and exciting opportunities for innovation within the field.

RECENT FINDINGS

The opportunities for concept, treatment, instrument, and knowledge-transfer innovation to better serve the specific needs of pediatric gynecology patients include novel approaches to neovagina creation using magnets, improving postoperative vaginal wound healing through newly designed and degradable vaginal stents, and complex Mullerian reconstructive surgical planning using virtual reality immersive experiential training.

SUMMARY

There is a significant window of opportunity to address the needs of pediatric, adolescent and adult gynecological patients with new innovative concepts and tools.

Comparison between the Outcomes of Using Biodegradable-Polymer Drug-Eluting Stents and Those of Using Durable-Polymer Drug-Eluting Stents in Acute Coronary Syndrome Patients Undergoing Percutaneous Coronary Intervention

BACKGROUND:

Many randomised control studies showed that percutaneous coronary interventions using biodegradable-polymer drug-eluting stents (DES) offer a safe and effective alternative to durable-polymer DES. However, not many studies have discussed its use in the setting of acute coronary syndromes.

AIM:

We aim to compare the biodegradable-polymer DES with durable-polymer DES when it comes to reducing the incidence of non-ST elevation acute coronary syndrome (NSTEACS) associated with adverse events.

METHODS:

We enrolled 205 patients presenting with NSTEACS and a TIMI risk score ≥ 3 in this study and divided them into two groups, group A and group B. Biodegradable-polymer DESs were exclusively used in group A, while durable-polymer DESs were used in group B. Major adverse events were reported in both groups during the hospital stay and patients were followed-up for 1 year.

RESULTS:

In our patients, we intervened on 390 diseased segments in a total of 360 vessels. After intervention, TIMI 0 was achieved in 0.97%, TIMI 1 in 1.46%, TIMI 2 in 2.45%, and TIMI 3 in 95.12% of the treated segments (P-value= 0.677). We implanted 121 biodegradable-polymer DESs and 146 durable-polymer DESs. Clinical success was achieved in 95.12% of our cases. We had 55 patients who needed repeated coronary angiography within 1 year (15 patients treated with biodegradable-polymer DES and 24 patients treated with durable-polymer DES). Eighteen patients experienced angina pains (8 patients treated with biodegradable-polymer DES and 10 patients treated with durable-polymer DES). Only 5 patients needed TLR (2 patients treated with biodegradable-polymer DES and 3 patients treated with durable -polymer DES) (P-value = 0.591), three of them had a myocardial infarction with documented angiographic evidence of significant in-stent restenosis (1 patient treated with biodegradable-polymer DES and 2 patients treated with durable-polymer DESs).

CONCLUSION:

Biodegradable-polymer DES represents a comparable alternative to durable-polymer DES in the setting of acute coronary syndromes.

Coronary stents with inducible VEGF/HGF-secreting UCB-MSCs reduced restenosis and increased re-endothelialization in a swine model

Atherosclerotic plaques within the vasculature may eventually lead to heart failure. Currently, cardiac stenting is the most effective and least invasive approach to treat this disease. However, in-stent restenosis is a complex chronic side effect of stenting treatment. This study used coronary stents coated with stem cells secreting angiogenic growth factors via an inducible genome-editing system to reduce stent restenosis and induce re-endothelialization within the artery. The characteristics of the cells and their adhesion properties on the stents were confirmed, and the stents were transplanted into a swine model to evaluate restenosis and the potential therapeutic use of stents with stem cells. Restenosis was evaluated using optical coherence tomography (OCT), microcomputed tomography (mCT) and angiography, and re-endothelialization was evaluated by immunostaining after cardiac stent treatment. Compared to a bare metal stent (BMS) or a parental umbilical cord blood-derived mesenchymal stem cell (UCB-MSC)-coated stent, the stents with stem cells capable of the controlled release of hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF) successfully reduced restenosis within the stent and induced natural re-endothelialization. Furthermore, UCB-MSCs exhibited the ability to differentiate into endothelial cells in Matrigel, and HGF and VEGF improved this differentiation. Our study indicates that stents coated with UCB-MSCs secreting VEGF/HGF reduce the restenosis side effects of cardiac stenting with improved re-endothelialization.

Combatting implant-associated biofilms through localized drug synthesis

Bacterial contamination of implantable biomaterials is a significant socioeconomic and healthcare burden. Indeed, bacterial colonization of implants after surgery has a high rate of incidence whereas concurrent prophylaxis using systemic antibiotics has limited clinical success. In this work, we develop enzyme-prodrug therapy (EPT) to prevent and to treat bacteria at interfaces. Towards the overall goal, novel prodrugs for fluoroquinolone antibiotics were developed on a privileged glucuronide scaffold. Whereas carbamoyl prodrugs were not stable and not suitable for EPT, glucuronides containing self-immolative linker between glucuronic acid masking group and the antibiotic were stable in solution and readily underwent bioconversion in the presence of β-glucuronidase. Surface coatings for model biomaterials were engineered using sequential polymer deposition technique. Resulting coatings afforded fast prodrug conversion and mediated antibacterial measures against planktonic species as evidenced by pronounced zone of bacterial growth inhibition around the biomaterial surface. These biomaterials coupled with the glucuronide prodrugs also effectively combatted bacteria within established biofilms and also successfully prevented bacterial colonization of the surface. To our knowledge, this is the first report of EPT engineered to the surface of biomaterials to mediate antibacterial measures.

Undesired Outcomes of the Catania Stent Compared to the Xience Stent in Patients Undergoing Angioplasty: A Double-Blind Randomized Controlled Trial

Background

The present study tries to compare the unintended outcomes of the Catania stent versus Xience stent in patients undergoing angioplasty.

Materials and Methods

In a three month, follow-up, double-blinded, randomized controlled trial, 83 patients undergoing angioplasty, who met the inclusion criteria were entered into the study. After randomization 43 patients were treated with the Xience stent and 40 patients with the Catania stent. Stent-related outcomes such as Cardiac and Non-Cardiovascular Death, Myocardial Infarction (MI), Target Lesion Revascularization (TLR), Stent Thrombosis (ST), Coronary Artery Bypass Grafting (CABG), Peripheral vasculopathy, and Cerebral Vascular Accident (CVA) were compared between the groups.

Results

There was no statistically significant difference in the incidence rate of complications and clinical outcomes between the two treatment groups (P > 0.05). The incidence of MI, TLR, CABG operation, peripheral vasculopathy, or CVA was not observed in any patient and there was no statistically difference in mortality (4.7% vs. 2.5%; P = 0.527) and stent thrombosis (2.3% vs. 2.5%; P = 0.735).

Conclusion

All in all, the present study could not find the significant differences between the Catania stent and Xience stent in terms of clinical outcomes during the follow-up period.

Recent developments in drug eluting devices with tailored interfacial properties

Drug eluting devices have greatly evolved during past years to become fundamental products of great marketing importance in the biomedical field. There is currently a large diversity of highly specialized devices for specific applications, making the development of these devices an exciting field of research. The replacement of the former bare metal devices by devices loaded with drugs allowed the sustained and controlled release of drugs, to achieve the desired local therapeutic concentration of drug. The newer devices have been "engineered" with surfaces containing micro- and nanoscale features in a well-controlled manner, that have shown to significantly affect cellular and subcellular function of various biological systems. For example, the topography can be structured to form an antifouling surface mimicking the defense mechanisms found in nature, like the skin of the shark. In the case of bone implants, well-controlled nanostructured interfaces can promote osteoblast differentiation and matrix production, and enhance short-term and long-term osteointegration. In any case, the goal of current research is to design implants that induce controlled, guided, and rapid healing. This article reviews recent trends in the development of drug eluting devices, as well as recent developments on the micro/nanotechnology scales, and their future challenges. For this purpose medical devices have been divided according to the different systems of the body they are focused to: orthopedic devices, breathing stents, gastrointestinal and urinary systems, devices for cardiovascular diseases, neuronal implants, and wound dressings.

In vitro and in vivo degradation of microfiber bioresorbable coronary scaffold

The degradation of Mirage Bioresorbable Microfiber Scaffold was evaluated in vitro and in vivo. The degradation in polymer molecular weight (MW), strut morphology, and integrity was accessed using gel permeation chromatography (GPC), X‐ray micro‐computed tomography (micro‐CT) evaluation. To simulate the physiological degradation in vitro, scaffolds were deployed in silicone mock vessels connected to a peristaltic pumping system, which pumps 37°C phosphate‐buffered saline (PBS, pH 7.4) at a constant rate. At various time points (30D, 60D, 90D, 180D, 270D, and 360D), the MW of microfibers decreased to 57.3, 49.8, 36.9, 13.9, 6.4, and 5.1% against the baseline. The in vivo degradation study was performed by implanting scaffolds in internal thoracic arteries (ITAs) of mini‐swine. At the scheduled sacrifice time points (30D, 90D, 180D, 270D, 360D, and 540D), the implanted ITAs were excised for GPC analysis; the MW of the implanted scaffolds dropped to 58.5, 34.7, 24.8, 16.1, 12.9, and 7.1, respectively. Mass loss of scaffolds reached 72.4% at 540D of implantation. Two stages of hydrolysis were observed in in vitro and in vivo degradation kinetics, and the statistical analysis suggested a positive correlation between in vivo and in vitro degradation. After 6 months of incubation in animals, significant strut degradation was seen in the micro‐CT evaluation in all sections as strut fragments and separations. The micro‐CT results further confirmed that every sample at 720D had X‐ray transmission similar to surrounding tissue, thereby indicating full degradation within 2 years. © 2017 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1842–1850, 2018.

Programmable Deployment of Tensegrity Structures by Stimulus-Responsive Polymers

Tensegrity structures with detached struts are naturally suitable for deployable applications, both in terrestrial and outer-space structures, as well as morphing devices. Composed of discontinuous struts and continuous cables, such systems are only structurally stable when self-stress is induced; otherwise, they lose the original geometrical configuration (while keeping the topology) and thus can be tightly packed. We exploit this feature by using stimulus responsive polymers to introduce a paradigm for creating actively deployable 3D structures with complex shapes. The shape-change of 3D printed smart materials adds an active dimension to the configurational space of some structural components. Then we achieve dramatic global volume expansion by amplifying component-wise deformations to global configurational change via the inherent deployability of tensegrity. Through modular design, we can generate active tensegrities that are relatively stiff yet resilient with various complexities. Such unique properties enable structural systems that can achieve gigantic shape change, making them ideal as a platform for super light-weight structures, shape-changing soft robots, morphing antenna and RF devices, and biomedical devices.

Stable Titania Nanostructures on Stainless Steel Coronary Stent Surface for Enhanced Corrosion Resistance and Endothelialization

Stainless steel (SS) coronary stents continue to present risk of in-stent restenosis that impact its long term safety and efficacy. The present work focuses on developing a drug-free and polymer-less surface on coronary stents by utilizing a titania (TiO₂ ) nanotexturing approach through hydrothermal processing, that will offer improved stent performance in vivo. Mechanically stable and durable nanotextured coatings are obtained on SS stents that also offer good corrosion resistance. In vitro vascular cell (endothelial and smooth muscle cells) studies on surface modified SS show preferential rapid endothelialization with enhanced nitric oxide production and reduce smooth muscle cell proliferation, in comparison to unmodified SS. In vivo evaluation of the nanotextured stents after subcutaneous implantation in rabbits show reduced irritability and minimal localized inflammatory response. These beneficial effects suggest that the stable, easily scalable titania nanosurface modification strategy on coronary stent surfaces can be a much cheaper alternative to drug eluting stents in addressing in-stent restenosis.

Immediate outcomes of eptifibatide therapy during intracoronary stent implantation

BACKGROUND

The objective of the present study was to assess the major immediate outcomes of eptifibatide therapy during intracoronary stent implantation.

MATERIALS AND METHODS

In an interventional study, patients undergoing percutaneous coronary intervention (PCI) were randomized into either the eptifibatide (n = 100) or the control (n = 107) group. In each group, demographic and clinical characteristics such as cardiac death, stent thrombosis (ST), myocardial infarction (MI), rates of target lesion and vessel revascularization, cerebral vascular accident (CVA), and emergency coronary artery bypass grafting (CABG) were recorded.

RESULTS

The overall rates of major adverse events such as mortality, Stent thrombosis (ST), Myocardial Infarction (MI), target lesion revascularization (TLR), target vessel revascularization (TVR), CVA, and emergency CABG within 24 h after stent implantation were low and comparable between the two groups; P > 0.05 considered significant for all comparisons.

CONCLUSION

There were no statistical differences between the clinical outcomes of groups administered with single-dose intracoronary eptifibatide and control groups among patients undergoing PCI during stent implantation.

Electrosprayed Montelukast/poly (lactic-co-glycolic acid) particle based coating: A new therapeutic approach towards the prevention of in-stent restenosis

Drug-eluting stents (DESs), have shown promising results in prevention of in-stent restenosis after percutaneous coronary intervention (PCI). The elevated level of leukotrienes (LTs) detected in injured arteries after PCI, together with the potential role of LTs in inflammatory cascades and structural alterations in arterial wall provides the rationale for development of therapeutic strategies for prevention of in-stent restenosis using LTs receptor antagonists. Montelukast (MK) is a selective cysLT1 receptor antagonist, with anti-inflammatory and anti-proliferative properties, which has been used for treatment of various diseases. Here, we report on the fabrication of MK/PLGA particles by electrospraying, aiming towards the development of particle based coating of DESs. The electrosprayed particles incorporated with 3% and 6% w/w MK exhibited fairly spherical shape with smooth surfaces and narrow size distribution. Sustained release of MK for up to 40days was obtained for both formulations, with higher initial burst release and drug release rate for the particles with higher drug loading. The LTD4 induced proliferation and migration of human coronary artery smooth muscle cells (HCASMCs) by 35% and 85%, respectively, which was substantially antagonized using MK incorporated particles. Nevertheless, MK antagonism preserved the normal proliferation and migration of human coronary artery endothelial cells (HCAECs). Moreover, MK antagonism inhibited the LTD4 induced phenotypic transition of HCASMCs from contractile to synthetic type. The electrosprayed MK-PLGA particles can be employed as a coating for DESs to inhibit the formation of neointimal hyperplasia responsible for in-stent restenosis, yet preserve the healing rate of the stented vessel.

STATEMENT OF SIGNIFICANT

Montelukast (MK) is a selective cysLT1 receptor antagonist, with anti-inflammatory and anti-proliferative properties. The LTD4 induced proliferation and migration of human coronary artery smooth muscle cells by 35% and 85%, respectively, which was substantially antagonized using MK incorporated particles. MK antagonism preserved the normal proliferation and migration of human coronary artery endothelial cells. The MK antagonism inhibited the phenotypic transition of human coronary artery smooth muscle cells from contractile to synthetic one induced by LTD4. The electrosprayed MK-PLGA particles can be employed as coating for DESs to inhibit formation of neointimal hyperplasia, responsible for in-stent restenosis.

Secreted Matrix Metalloproteinase-9 of Proliferating Smooth Muscle Cells as a Trigger for Drug Release from Stent Surface Polymers in Coronary Arteries

Cardiovascular diseases are the leading causes of death in industrialized countries. Atherosclerotic coronary arteries are commonly treated with percutaneous transluminal coronary intervention followed by stent deployment. This treatment has significantly improved the clinical outcome. However, triggered vascular smooth muscle cell (SMC) proliferation leads to in-stent restenosis in bare metal stents. In addition, stent thrombosis is a severe side effect of drug eluting stents due to inhibition of endothelialization. The aim of this study was to develop and test a stent surface polymer, where cytotoxic drugs are covalently conjugated to the surface and released by proteases selectively secreted by proliferating smooth muscle cells. Resting and proliferating human coronary artery smooth muscle cells (HCASMC) and endothelial cells (HCAEC) were screened to identify an enzyme exclusively released by proliferating HCASMC. Expression analyses and enzyme activity assays verified selective and exclusive activity of the matrix metalloproteinase-9 (MMP-9) in proliferating HCASMC. The principle of drug release exclusively triggered by proliferating HCASMC was tested using the biodegradable stent surface polymer poly-l-lactic acid (PLLA) and the MMP-9 cleavable peptide linkers named SRL and AVR. The specific peptide cleavage by MMP-9 was verified by attachment of the model compound fluorescein. Fluorescein release was observed in the presence of MMP-9 secreting HCASMC but not of proliferating HCAEC. Our findings suggest that cytotoxic drug conjugated polymers can be designed to selectively release the attached compound triggered by MMP-9 secreting smooth muscle cells. This novel concept may be beneficial for stent endothelialization thereby reducing the risk of restenosis and thrombosis.