Tubing Vascular Grafts

Catheters and Tubing Vascular Grafts Membranes Drug delivery... 

The suitable materials for the above mentioned domains are polymers, metals and ceramics. Among these, polymers play an important role. Even the polymers have a lot of remarkable properties that could be used in biomaterials design, the interaction between these artificial materials and tissues and blood could create serious medical problems such as clot formation, activating of platelets, and occlusion of tubes for dialysis or vascular grafts. In the last few years, novel techniques of synthesis have been used to correlate desirable chemical, physical and biological properties of biomaterials. 

Prevention of thrombus formation is important in clinical applications where blood is in contact such as hemodialysis membranes and tubes, artificial heart and heart-lung machines, prosthetic valves, and artificial vascular grafts. In spite of the use of anticoagulants, considerable platelet deposition and thrombus formation take place on the artificial surfaces [Branger, 1990]. 

Fig. 10.7 Examples of biomedical applications of BC are meniscus replacements (pig meniscus on the left, BC meniscus on the right), artificial blood vessels and wound dressing for skin heaiing [76-78], Nanocellulose (bacterial cellulose, BC), such as that produced by Acetobacter xylinum, has shown promising results as a replacement material for small diameter vascular grafts (Fig. 10.8). These BC tubes have been tested in a pig model as an infrarcnal aortic bypass and show promising results for use as vascular grafts in the future...

Backdahl, H., Risbergb, B., Gatenholm, P. Observations on bacterial cellulose tube formation for application as vascular graft. Mater Sci Eng C. 31(1), 14-21 (2011)... 

Polyurethanes Ligament replacements, heart valve prostheses, vascular graft prostheses, breast prosthesis, catheter, cannulae films, tubing... 

Central venous catheters, intraaortic balloon pump balloons (polyurethanes), artificial heart bladders (polyurethanes), carrier for drug-delivery coatings, insulators for pacemaker leads, vascular grafts (e.g., biostable polyurethanes), heart-valve components (silicones), extracorporeal tubing... 

Housings for extracorporeal devices (acrylics, poly(carbonates), poly(methylpentane)], catheters, angioplasty balloons, sutures, vascular grafts (polyester textiles, expanded PTFE), medical tubing oxygenator and hemdi-alysis membranes... 

Eujimoto K, Minato M, Miyamoto S, Kaneko T, Kikuchi H, Sakai K, Okada M, Ikada Y. Porous polyurethane tubes as vascular graft. /. Appl. Biomat. 4 ... 

An example of a pulsatile-flow bioreactor for vascular grafts is shown in Figure 44.3. This design, used in the Laboratory of Cardiovascular Tissue Engineering at the University of Oklahoma, resembles the shell and tube concept of some heat exchangers. Flow circuits are separated into shell-side and tube-side to monitor (and control) system pressure and flow rates independently. Control valves downstream... 

FIGURE 44.3 Shelf-tube bioreactor for vascular grafts. (Courtesy of Dr. P. McFetridge from the School of Chemical Engineering and Materials Science, University of Oklahoma Bioengineering.)... 

In the field of accessories for medical devices, Ortega and Small (2007) studied the effect of a thermally deployable SMP-based adapter for kidney dialysis needles, designed to reduce haemodynamic stress on the arteriovenous grafts. This tube-shaped adapter can be delivered through the needle and thermally deployed upon blood contact. Both computational fluid dynamics simulations and in vitro flow visualization measurements show that the adapter is able to redirect the needle flow so that its impact on the vascular grafts is reduced. 

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