Patterned Electrospinning: A Method of Generating Defined Fibrous Constructs Influencing Cell Adhesion and Retention.

A critical component of tissue engineering is the ability to functionally replace native tissue stroma. Electrospinning is a technique capable of forming fibrous constructs with a high surface area for increased cell-material interaction and enhanced biocompatibility. However, physical and biological properties of electrospun scaffolds are limited by design controllability on a macroscale.

The Influence of Polymer Processing Methods on Polymer Film Physical Properties and Vascular Cell Responsiveness.

Implantable vascular devices typically interface with blood and vascular tissues. Physical properties of device materials and coatings, independent of chemical composition, can significantly influence cell responses and implant success. Here, we analyzed the effect of various polymer processing regimes, using a single implant polymer - poly(ε-caprolactone) (PCL), on vascular endothelial cell (EC), smooth muscle cell (SMC), and platelet response.

Design Effect of Metallic (Durable) and Polymeric (Resorbable) Stents on Blood Flow and Platelet Activation.

Bioresorbable vascular scaffolds (BVS) provide transient vessel support for occluded coronary arteries while resorbing over time, potentially allowing vessel restoration approximating the native, healthy state. Clinical trials indicate that the Absorb BVS (Abbott Vascular, Santa Clara, CA) performance was similar to that of the Xience metallic drug-eluting stent (DES), with low long-term complications rates. However, when under-deployed in very small vessels (diameter < 2.

Acute thrombogenicity of fluoropolymer-coated versus biodegradable and polymer-free stents.

Aims: Durable fluoropolymer-coated everolimus-eluting stents (FP-EES) have shown lower rates of stent thrombosis (ST) versus bare metal stents (BMS) and first-generation bioabsorbable polymer (BP) DES. The aim of the study was to evaluate the specific role of the FP in thromboresistance.

Methods And Results: A total of 57 stents were assessed in three separate ex vivo swine arteriovenous shunt model experiments (first shunt experiment, custom-made fluoropolymer-coated BMS [FP-only] vs.

Evaluation of chemical stability of polymers of XIENCE everolimus-eluting coronary stents in vivo by pyrolysis-gas chromatography/mass spectrometry.

The polymers poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and poly(n-butyl methacrylate) (PBMA) are employed in manufacturing the XIENCE family of coronary stents. PBMA serves as a primer and adheres to both the stent and the drug coating. PVDF-HFP is employed in the drug matrix layer to hold the drug everolimus on the stent and control its release.

Blood compatibility assessment of polymers used in drug eluting stent coatings.

Differences in thrombosis rates have been observed clinically between different drug eluting stents. Such differences have been attributed to numerous factors, including stent design, injury created by the catheter delivery system, coating application technologies, and the degree of thrombogenicity of the polymer. The relative contributions of these factors are generally unknown.

Technology limitations of BRS in bifurcations.

Recommended techniques for bifurcation stenting continue to be revised with specific attention to bioresorbable scaffolds (BRS). Optimal procedural success and long-term outcomes with BRS can perhaps be improved with careful attention to implantation techniques. Good vessel preparation is imperative for optimal expansion of the scaffold, and proper vessel sizing is necessary to ensure compliance with scaffold expansion limits and preservation of proper scaffold function.

Polymeric trileaflet prosthetic heart valves: evolution and path to clinical reality.

Present prosthetic heart valves, while hemodynamically effective, remain limited by progressive structural deterioration of tissue valves or the burden of chronic anticoagulation for mechanical valves. An idealized valve prosthesis would eliminate these limitations. Polymeric heart valves (PHVs), fabricated from advanced polymeric materials, offer the potential of durability and hemocompatibility.

Assessment of material by-product fate from bioresorbable vascular scaffolds.

Fully bioresorbable vascular scaffolds (BVS) are attractive platforms for the treatment of ischemic artery disease owing to their intrinsic ability to uncage the treated vessel after the initial scaffolding phase, thereby allowing for the physiological conditioning that is essential to cellular function and vessel healing. Although scaffold erosion confers distinct advantages over permanent endovascular devices, high transient by-product concentrations within the arterial wall could induce inflammatory and immune responses. To better understand these risks, we developed in this study an integrated computational model that characterizes the bulk degradation and by-product fate for a representative BVS composed of poly(L-lactide) (PLLA).

A theoretical model to characterize the drug release behavior of drug-eluting stents with durable polymer matrix coating.

The time-dependent local drug delivery from drug-eluting stents (DES) plays a critical role in reducing restenosis in intravascular stenting. To better understand the basic mechanism of drug release for certain polymer-drug-coated DES platforms, a cylindrical diffusion model was applied successfully to quantitatively describe the experimental drug release data of Dynalink-E in vitro and in vivo. The results showed that the profiles of Dynalink-E everolimus release could be controlled by such characteristic parameters as coating thickness and diffusion coefficient.

Surface characterization of poly(lactic acid)/everolimus and poly(ethylene vinyl alcohol)/everolimus stents.

Two model drug eluting stents of poly(lactic acid) (PLA)/everolimus and poly(ethylene vinyl alcohol) copolymer (EVAL)/everolimus have been investigated using complementary surface analysis techniques including AFM, XPS, and ATR-IR to assess their structure and its relation to drug release. Different surface morphologies were observed for these stents, with phase separation evident on the PLA coating and a homogeneous system for the EVAL-based coating. This indicates a potentially different drug distribution for the different stents, although both showed a surface enrichment of the drug compared to the bulk.

Design principles and performance of bioresorbable polymeric vascular scaffolds.

Aims: Bioresorbable polymeric vascular scaffolds may spawn a fourth revolution in percutaneous coronary intervention (PCI) and a novel treatment termed vascular restoration therapy. The principal design considerations for bioresorbable scaffolds are discussed in the context of physiological behaviour using the Bioabsorbable Vascular Solutions (BVS) ABSORB Cohort B scaffold (Abbott Vascular) as an example.

Methods And Results: The lifecycle of a bioresorbable scaffold is divided into three phases: (1) revascularisation; (2) restoration; and (3) resorption.

Nanoscale mechanical measurement determination of the glass transition temperature of poly(lactic acid)/everolimus coated stents in air and dissolution media.

Localized atomic force microscopy (AFM) force analysis on poly(lactic acid) (PLA) and poly(lactic acid)/everolimus coated stents has been performed under ambient conditions. Similar Young's modulus were derived from both PLA and PLA/everolimus stent surface, namely 2.25+/-0.

A mathematical model for predicting drug release from a biodurable drug-eluting stent coating.

Drug-eluting stents (DESs) are drug-device combination products that have been commercialized and demonstrated to be safe and efficacious in treating coronary artery disease. They have been very effective in reducing the extent of neointimal hyperplasia and therefore in preventing or minimizing the occurrence of in-stent restenosis. In order to develop a successful DES, it is imperative that the coating be designed so as to deliver, after stent implantation, a therapeutic dose of the drug for the desired time duration at the site of the arterial blockage.

Modeling of degradation and drug release from a biodegradable stent coating.

Biodegradable polymeric coatings on cardiovascular stents can be used for local delivery of therapeutic agents to diseased coronary arteries after stenting procedures. This can minimize the occurrence of clinically adverse events such as restenosis after stent implantation. A validated mathematical model can be a very important tool in the design and development of such coatings for drug delivery.

Therapy considerations in drug-eluting stents.

Approximately 12 million Americans have coronary artery disease, and almost one in five deaths in the United States can be attributed to this disease. In addition, 1.2 million Americans undergo cardiac catheterization and over one-half million receive a percutaneous coronary intervention such as balloon angioplasty, atherectomy, or stent implantation annually.