Novel propylene oxide-treated bovine pericardium as soft tissue repair material and potential scaffold for tissue engineering.

In contrast with autographic or allographic repair materials, the use of a xenographic soft tissue repair material could improve patient outcomes following surgery, since such a material would not require a second surgical site and could reduce the risk of human-to-human disease transmission. Veritas(c) Collagen Matrix (Veritas) is a novel, non-crosslinked soft tissue repair material derived from bovine pericardium. Physical property testing shows this material is strong, malleable, of uniform thickness, and easily sutureable. Biocompatibility testing, as well as viral safety and extractable deoxyribonucleic acid (DNA) studies demonstrate the acellularity, safety, and immunological inertness of the material. Animal studies in pigs and rabbits, in a variety of surgical procedures that include abdominal wall implant, unilateral hysterectomy, urethral sling implant, and dural substitute studies demonstrate Veritas does not adhere readily to tissues of the chest wall or abdomen under conditions that promote adhesions. In addition, these studies show that Veritas is remodelable and, in time, becomes histologically indistinguishable from the host tissue. These findings indicate Veritas is an ideal soft tissue repair material and it may serve as an ideal scaffold for tissue engineering.

Hemocompatibility of materials used in microelectromechanical systems: platelet adhesion and morphology in vitro.

Microelectromechanical systems (MEMS) create an opportunity for the development of smaller, cheaper, and more precise biomedical instrumentation and devices. Little is known, however, about the hemocompatibility of the materials used to fabricate these devices. Because of the potentially harmful consequences of thrombus formation, a better understanding of blood interactions with bioMEMS materials is desirable. This study is an in vitro assessment of the hemocompatibility of silicon (Si), silicon dioxide (SiO2), silicon nitride (Si3N4), low-stress silicon nitride (Si(1.0)N(1.1)), SU-8 photoresist, and parylene thin films. A polycarbonate-based polyurethane, was used as a reference material. Experiments were carried out to detect differences in platelet adhesion or morphology after contact with these materials under static conditions. Platelet adhesion on Si, Si3N4, Si(1.0)N(1.1,) and SU-8 photoresist was significantly greater (P < 0.05) than platelet adhesion on polyurethane. Adhesion on parylene and SiO(2) was not significantly different from on polyurethane (P < 0.05). The median platelet area and circularity were higher on polyurethane than all other materials. Materials that showed higher levels of platelet adhesion tended to have platelets that showed less spreading, except for SiO2, where platelets exhibited relatively low adhesion and spreading. This data suggests that Si, Si3N4, Si(1.0)N(1.1), and SU-8 photoresist may be more reactive to platelets and therefore more thrombogenic than parylene, SiO2, and polyurethane. These results may be helpful in guiding the selection of materials for use in the development of blood-contacting microelectromechanical systems.

Manipulation of remodeling pathways to enhance the mechanical properties of a tissue engineered blood vessel.

There is a current need for a small diameter vascular graft due to the limited supply of autogenous grafts and the failure of synthetic grafts due to thrombosis and/or intimal hyperplasia. The use of living cells and tissues to fabricate a small diameter graft (i.e., tissue engineered blood vessel, TEBV) could be useful given the endothelialization potential and biocompatibility benefits of such a graft. However, while sufficient strength has been attained in a TEBV, coordinate compliance has yet to be fine-tuned. In this study we investigate the effects of biological response modifiers, retinoic acid (RA) and ascorbic acid (AA) on TEBV biomechanics as a function of time and subsequently correlate observed RA/AA induced changes in TEBV mechanics with alterations in smooth muscle cell (SMC) biochemistry. TEBVs were constructed using a fibrillar type I collagen network populated by human aortic smooth muscle cells (AoSMC). Following construction this TEBV was treated with 0.3 mM AA and 0.1 mM RA (concentrations found to induce changes in VSMC phenotype). Ultimate tensile stress (UTS), rate of relaxation (RR) and elastic efficiency (EE) of RA/AA treated and untreated TEBVs were measured following 1, 7, 15, 30, 45, and 60 days of treatment. At corresponding time points, the effect of these treatments on collagen and elastin protein synthesis and mRNA expression was examined. RA/AA treated TEBV strength increased and stiffness decreased compared to controls as a function of time. Relative collagen synthesis in treated TEBVs exceeded control levels by nearly two-fold at 15 and 30 days of incubation. RA/AA treated collagen gene expression followed a similar trend. Relative elastin synthesis was also greater in treated TEBVs as compared to untreated TEBVs at 15 and 30 days of incubation and correspondingly elastin mRNA expression was significantly elevated at 15 days of incubation. These data provide evidence that RA/AA treated TEBVs exhibit mechanical properties which more closely mimic those of a native vessel than their untreated counterparts and that changes in extracellular matrix composition and matrix gene expression in the presence of RA/AA treatment may play an important role in the development of said mechanical properties.