Novel stents for the prevention of restenosis

Molecular Docking, Computational, and Antithrombotic Studies of Novel 1,3,4-Oxadiazole Derivatives

A new series of 1,3,4-oxadiazoles derivatives was synthesized, characterized, and evaluated for their in vitro and in vivo anti-thrombotic activity. Compounds (3a–3i) exhibited significant clot lysis with respect to reference drug streptokinase (30,000 IU), and enhanced clotting time (CT) values (130–342 s) than heparin (110 s). High affinity towards 1NFY with greater docking score was observed for the compounds (3a, 3i, 3e, 3d, and 3h) than the control ligand RPR200095. In addition, impressive inhibitory potential against factor Xa (F-Xa) was observed with higher docking scores (5612–6270) with Atomic Contact Energy (ACE) values (−189.68 to −352.28 kcal/mol) than the control ligand RPR200095 (Docking score 5192; ACE −197.81 kcal/mol). In vitro, in vivo, and in silico results proposed that these newly synthesized compounds might be used as anticoagulant agents.

Hemocompatibility investigation of the NiTi alloy implanted with tantalum

A composite TiO(2)/Ta(2)O(5) nano-film has been formed on the NiTi shape memory alloy by Ta implantation. The wettability, protein adsorption, platelets adhesion and hemolysis tests are conducted to evaluate the hemocompatibility. The contact angle measurements showed that the surface of the NiTi alloy kept hydrophilic before and after Ta implantation, although the water contact angle increased with the increasing of implantation current. Both of the surface energy and the interfacial tension decreased after Ta implantation. The protein adsorption behavior was investigated by (125)I isotope labeling. The fibrinogen adsorption was enhanced by a high surface roughness or a large interfacial tension, while the albumin adsorption was insensitive to the surface modification. Platelet adhesion and activation were weakened and the hemolysis rate was reduced at least 46% after Ta implantation due to the decreased surface energy and improved corrosion resistance ability, respectively.

Polymer-based sustained-release dosage forms for protein drugs, challenges, and recent advances

While the concept of using polymer-based sustained-release delivery systems to maintain therapeutic concentration of protein drugs for extended periods of time has been well accepted for decades, there has not been a single product in this category successfully commercialized to date despite clinical and market demands. To achieve successful systems, technical difficulties ranging from protein denaturing during formulation process and the course of prolonged in vivo release, burst release, and incomplete release, to low encapsulation efficiency and formulation complexity have to be simultaneously resolved. Based on this updated understanding, formulation strategies attempting to address these aspects comprehensively were reported in recent years. This review article (with 134 citations) aims to summarize recent studies addressing the issues above, especially those targeting practical industrial solutions. Formulation strategies representative of three areas, microsphere technology using degradable hydrophobic polymers, microspheres made of water soluble polymers, and hydrophilic in vivo gelling systems will be selected and introduced. To better understand the observations and conclusions from different studies for different systems and proteins, physicochemical basis of the technical challenges and the pros and cons of the corresponding formulation methods will be discussed.

Finite element analysis of the implantation of a balloon-expandable stent in a stenosed artery

Intracoronary stent implantation (ICSI) has been widely used in interventional procedures. It can induce an even greater increment in intervention effectiveness and in success rate than traditional percutaneous transluminal coronary angioplasty (PTCA). However, owing to the complexities in geometries, material properties and interactions seen in ICSI, analyses of the complete stenting system composed of balloon, stent, plaque and artery are limited. In order to investigate the biomechanical characteristics of ICSI, a three-dimensional model of the complete stenting system and self-defined constitutive models for the plaque and the balloon were developed, which made the simulation well close to the real situation. Finite element method (FEM) was used to simulate the stent implantation under the balloon inflation and deflation. The simulated results show that the distal end of stent, which tilts after expansion, may injure the artery wall. High stress concentrates in the contacting areas between the stent and the plaque. The recoil ratios of the balloon-stent model, the balloon-stent-plaque-artery model (representing ICSI) and the balloon-plaque-artery model (representing PTCA) are 3.1%, 12.3% and 22.9%, respectively. In conclusion, FEM can help illustrate and quantify some biomechanical characteristics of ICSI. And it would be helpful for the general understanding of ICSI.

Local drug delivery in restenosis injury: thermoresponsive co-polymers as potential drug delivery systems

The success of percutaneous transluminal coronary angioplasty in treatment of acute coronary syndromes has been compromised by the incidence of restenosis. The physical insult of balloon insertion can damage or remove the endothelial monolayer, thereby generating a prothrombotic surface. The resulting inappropriate response to injury can also lead to penetration of inflammatory cells, conversion of the underlying media to a synthetic phenotype, deposition of extracellular matrix, constrictive remodeling, and neointimal hyperplasia. While stent implantation at the time of balloon insertion has offset some of these events, inflammatory responses to the implanted biomaterial (stent) and intimal hyperplasia are still prominent features of the procedure, leading in 20-30% of cases to in-stent restenosis within a year. Systemic delivery of drugs designed to offset in-stent restenosis injury has been largely unsuccessful, which has led to the development of strategies for coating stents with drugs for local delivery. Drug-eluting stents constitute an innovative means of further reducing the incidence of restenosis injury and clinical trials have shown encouraging results. This review focuses on properties of a class of environment-sensitive hydrogels, the N-isopropylacrylamide-based thermoresponsive co-polymers, on their potential roles as stent coatings, on their demonstrated ability to incorporate and release drugs that modify vascular endothelial and smooth muscle cell functions, and on issues that still await clarification, prior to their adoption in a clinical setting.