Thrombogenic potential of Innovia polymer valves versus Carpentier-Edwards Perimount Magna aortic bioprosthetic valves.

Trileaflet polymeric prosthetic aortic valves (AVs) produce hemodynamic characteristics akin to the natural AV and may be most suitable for applications such as transcatheter implantation and mechanical circulatory support (MCS) devices. Their success has not yet been realized due to problems of calcification, durability, and thrombosis. We address the latter by comparing the platelet activation rates (PARs) of an improved polymer valve design (Innovia LLC) made from poly(styrene-block-isobutylene-block-styrene) (SIBS) with the commercially available Carpentier-Edwards Perimount Magna Aortic Bioprosthetic Valve.

In-vivo assessment of a novel polymer (SIBS) trileaflet heart valve.

Background And Aim Of The Study: A novel trileaflet polymer valve, which is a composite design of a biostable and biocompatible polymer poly(styrene-block-isobutylene-block-styrene) (SIBS) with an embedded reinforcement polyethylene terephthalate (PET) fabric, is being developed with the intention of providing a valve that has low thrombogenicity, high durability and favorable hemodynamic performance. The study aim was to investigate the biocompatibility and performance of this SIBS valve prototype under physiological loading conditions similar to humans, using a large-animal model.

Methods: Four SIBS valves (two with surface modification using dimyristoyl phosphatidylcholine, DMPC), and two commercial Magna tissue valves, were implanted into sheep.

A novel small animal model for biocompatibility assessment of polymeric materials for use in prosthetic heart valves.

A composite polymeric material, poly(styrene-block-isobutylene-block-styrene) (SIBS) with an embedded reinforcement polyethylene terephthalate (PET) fabric, is undergoing investigation for potential use in a novel heart valve. The purpose of this study was to develop and implement a small animal model to assess the biocompatibility of composite samples in a cardiovascular tissue and blood-contacting environment. Composite samples were manufactured using dip coating and solvent casting with two coating thicknesses (25 and 50 microm).

Development and evaluation of a novel artificial catheter-deliverable prosthetic heart valve and method for in vitro testing.

Background: This work presents a novel artificial prosthetic heart valve designed to be catheter or percutaneously deliverable, and a method for in vitro testing of the device. The device is intended to create superior characteristics in comparison to tissue-based percutaneous valves.

Methods: The percutaneous heart valve (PhV) was constructed from state-of-the-art polymers, metals and fabrics.

Comparison of near-wall hemodynamic parameters in stented artery models.

Four commercially available stent designs (two balloon expandable-Bx Velocity and NIR, and two self-expanding-Wallstent and Aurora) were modeled to compare the near-wall flow characteristics of stented arteries using computational fluid dynamics simulations under pulsatile flow conditions. A flat rectangular stented vessel model was constructed and simulations were carried out using rigid walls and sinusoidal velocity input (nominal wall shear stress of 10+/-5 dyn/cm2). Mesh independence was determined from convergence (<10%) of the axial wall shear stress (WSS) along the length of the stented model.

Effects of stent geometry on local flow dynamics and resulting platelet deposition in an in vitro model.

Platelet deposition has been shown previously to depend on convective transport patterns, visualized by the instantaneous streamlines. Previous attempts to quantify hemodynamic studies of platelet deposition have been limited to 2D geometries. This study provides a physiologic assessment of the effects of stent geometry on platelet deposition by using actual 3D stents.

Exploring electron transfer between heme proteins of cytochrome C super family in biosensors: a molecular mechanics study.

Electron transfer between heme proteins with mediators plays an important role in the fabrication of sensitive bio-nano sensors. Heme protein Cytochrome c (pdb code - 1HRC) was chosen as the mediator with Cytochrome c' (pdb code - 1A7V) as the probe protein for our investigation on the electron transfer process. We used the software GRAMM, HEX, and MACRODOX to build the protein complex with further evaluation by GROMACS potential.

A phospholipid-modified polystyrene-polyisobutylene-polystyrene (SIBS) triblock polymer for enhanced hemocompatibility and potential use in artificial heart valves.

Poly(styrene-block-isobutylene-block-styrene) ('SIBS') is selected for a novel tri-leaflet heart valve due to its high resistance to oxidation, hydrolysis, and enzyme attack. SIBS is modified using six different phospholipids and its mechanical properties characterized by tensile stress, peel strength, shear strength, contact angle, and surface energy, and then for hemocompatibility by studying the adhesion of fluorescently labeled platelets in a parallel plate chamber under physiological flow conditions. Phospholipid modification decreases SIBS tensile stress (at 45% strain) by 30% and reduces platelet adhesion by a factor of 10, thereby improving its hemocompatibility and its potential use as a synthetic heart valve.

Large scale motions in a biosensor protein glucose oxidase: a combined approach by QENS, normal mode analysis, and molecular dynamics studies.

The characteristics of the glucose oxidase were studied using a combination of experimental and theoretical techniques. Quasi elastic neutron scattering experiments were used to obtain the vibrational frequencies of the protein. These were compared to theoretical results obtained by normal mode analysis.

Medical applications of poly(styrene-block-isobutylene-block-styrene) ("SIBS").

Poly(Styrene-block-IsoButylene-block-Styrene) ("SIBS") is a biostable thermoplastic elastomer with physical properties that overlap silicone rubber and polyurethane. Initial data collected with SIBS stent-grafts and coatings on metallic stents demonstrate hemocompatibility, biocompatibility and long-term stability in contact with metal. SIBS has been used successfully as the carrier for a drug-eluting coronary stent; specifically Boston Scientific's TAXUS stent, and its uses are being investigated for ophthalmic implants to treat glaucoma, synthetic heart valves to possibly replace tissue valves and other applications.

Effect of fiber orientation on the stress distribution within a leaflet of a polymer composite heart valve in the closed position.

Polymer trileaflet valves offer natural hemodynamics with the potential for better durability than commercially available tissue valves. Strength and durability of polymer-based valves may be increased through fiber reinforcement. A finite element analysis of the mechanics of a statically loaded polymer trileaflet aortic heart valve has been conducted.

A novel polymer for potential use in a trileaflet heart valve.

A novel polyolefin, poly(styrene-b-isobutylene-b-styrene) (Quatromer), is being proposed as a viable polymer for use in trileaflet heart valves because of its oxidative stability. The current study was designed to assess the polymer's hemocompatibility and mechanical durability. Mechanical characterization included static tensile tests and dynamic tension-tension and bending fatigue tests, where the properties of isotropic and composite (polypropylene (PP) embedded) Quatromer specimens were compared with those of a polyurethane (PUR) approved for cardiovascular applications.

Spatial distribution of platelet deposition in stented arterial models under physiologic flow.

This paper presents dynamic flow experiments with fluorescently labeled platelets to allow for spatial observation of wall attachment in inter-strut spacings, to investigate their relationship to flow patterns. Human blood with fluorescently labeled platelets was circulated through an in vitro system that produced physiologic pulsatile flow in a parallel plate flow chamber that contained three different stent designs that feature completely recirculating flow, partially recirculating flow (intermediate strut spacing), and completely reattached flow. Highly resolved spatial distribution of platelets was obtained by imaging fluorescently labeled platelets between the struts.

Flow-induced platelet activation in a St. Jude mechanical heart valve, a trileaflet polymeric heart valve, and a St. Jude tissue valve.

Polymer heart valves have been under investigation since the 1960s, but their success has been hampered by an overall lack of durability mainly due to calcification of the leaflets and a relatively high rate of thromboembolic complications. A new polymer (Quatromer) trileaflet design was tested for its thrombogenic potential and was compared to that of existing prosthetic heart valves routinely implanted in patients: a St. Jude Medical bileaflet mechanical heart valve (MHV) and a St.

Platelet adhesion to simulated stented surfaces.

Purpose: To determine if the protrusion of stent struts into the flow stream, which creates stagnation along the wall dependent on the strut spacing, has an effect on platelet adhesion.

Methods: Three 2-dimensional stents with different strut spacings were placed in a flat-plate flow chamber. Human blood was collected and platelets were labeled with indium 111.