Vascular application

The most robust of observations to date by multiple investigators is the finding that AVI-4126 is safe and effective in vascular application in a number of species. Different methods for local delivery have also been tested, but these observations fall short of proof that AVI-4126 will be effective in the treatment of human restenosis. Efficacy in animal models has also been encouraging. Furthermore, all these studies with AVI-4126 indicated that the agent is safe. 

Being used in several forms of orthopedic devices Making inroads in a number of new vascular applications... 

Trudel, J., Shalaby, S. W., Massia, S. and LaBerge, M., Cytocompatibility of an absorbable gel-forming sealant candidate for vascular applications, Trans. Soc. Biomater., 22, 162, 1999. 

Abstract This chapter focuses on the vascular applications of injectable biomatetials. Two clinically relevant vascular conditions, cerebral arteriovenous malformations and intracranial aneurysm, will be discussed in terms of endovascular embolization. This chapter then outlines available embolic materials used to treat each condition, as well as highlighting new injectable biomaterials developed for embolization purposes. 

Shape memory polymers make up another class of injectable biomaterials for vascular applications, yet are relatively new in the field of endovascular embolization. Shape memory polymers are chemically structured so that they are able to reversibly take on a different physical shape in response to some stimuli (Small et al, 2007). Usually these different shapes include a compact form and an expanded form of the polymer. In the case of endovascular embolization, the expanded polymer can be pre-formed to fit specific contours of an individual aneurysm (Ortega et al, 2007). Upon interacting with some type of stimuli, such as heat or cold, the material is compacted into a shape that can be delivered through a microcatheter. The process of using shape memory polymers to embolize an aneurysm is shown in Fig. 7.5, along with samples of expanded SMPs (Ortega et al, 2007). 

Hermetic seals for pacemakers, enhanced cell adhesion, limited vascular applications, experimental heart-valve components. 

Silicone elastomers have a long history of use in the medical field. They have been applied to cannulas, catheters, drainage tubes, balloon catheters, finger and toe joints, pacemaker lead wire insulation, components of artificial heart valves, breast implants, intraocular lenses, contraceptive devices, burn dressings and a variety of associated medical devices. A silicone reference material has been made available by the National Institutes of Health to equate the blood compatibility of different surfaces for vascular applications. This material is available as a silica-free sheet. Contact the Artificial Heart Program, NHBLI, NIH, Bethesda, Md. for further information. 

The fabrics used in these devices also differ. Polyester is a commonly used polymer in medical applications. This polymer is used in the ASO, the BCSO, the CS/SF and the DAW devices. The GHSO device, on the other hand, is composed of ePTFE. Both of these polymers are known to be reasonably inert, flexible, durable and resistant to degradation. Additionally, their creep resistance is acceptable and they are therefore used in vascular applications where the fabric s creep behavior is an important consideration. The fabric construction of the ASO device is unknown, but it appears to be a nonwoven. This specific construction provides a mesh, in which pore sizes can easily be controlled. This is of importance when considering tissue in-growth. Additionally, if the fabric is made with very small pores, it... 

Among the various synthetic materials that were initially tested such as nylon, Orion , Ivalon , only PTFE (Teflon ) and PET (Daaon ) have been shown to resist biodegradation in the body. i- Other synthetic and natural polymers, such as polyurethanes and silk fibroin, are also discussed in this chapter as they remain potential alternatives for certain current and future vascular applications. 

Study of PET ageing in vascular applications shows that mass erosion is predominant compared to surface erosion, although manufacturing processes of these pros-theses could lead to more or less pronounced surface defaults that encourage surface ageing. 

Soletti L, Nieponice A, Hong Y, Ye SH, Stankus JJ, Wagner WR, et al. In vivo performance of a phospholipid-coated bioerodable elastomeric graft for small-diameter vascular applications. J Biomed Mater Res A 2011 96(2) 436-48. 

Natural polymers such as collagen, elastin, and fibrin make up much of the body s native extracellular matrix (ECM), and they were explored as platforms for tissue engineered constructs [34,47 9]. Polysaccharides such as chitosan, starch, alginate, and dextran were also studied for these purposes. Simultaneously, silk fibroin was widely explored for vascular applications due to its higher mechanical properties in comparison to other natural polymers, such as fibrin [48]. The utilization of natural polymers to create tissue-engineered scaffolds has yielded promising results, both in vitro and in vivo, due in part to the enhanced bioactivity provided by materials normally found within the human body [50]. However, their mechanical response is usually below the required values therefore, synthetic polymers have been explored to achieve the desired properties. 

Belcaro G, Maquart FX, Scoccianti M, Hosoi M, Cesarone MR, Luzzi R, Comelli U, Ledda A, Feragalli B (2011) TECA (Titrated Extract of Centella Asiatica) new microcirculatory, biomolecular, and vascular application in preventive and clinical medicine. A status paper. Panminerva Med 53 105-118... 

---