Vascularization and tissue infiltration of a biodegradable polyurethane matrix

Abstract

Urethanes are frequently used in biomedical applications because of their excellent biocompatibility. However, their use has been limited to bioresistant polyurethanes. The aim of this study was to develop a nontoxic biodegradable polyurethane and to test its potential for tissue compatibility. A matrix was synthesized with pentane diisocyanate (PDI) as a hard segment and sucrose as a hydroxyl group donor to obtain a microtextured spongy urethane matrix. The matrix was biodegradable in an aqueous solution at 37°C in vitro as well as in vivo. The polymer was mechanically stable at body temperatures and exhibited a glass transition temperature (Tg) of 67°C. The porosity of the polymer network was between 10 and 2000 µm, with the majority of pores between 100 and 300 µm in diameter. This porosity was found to be adequate to support the adherence and proliferation of bone-marrow stromal cells (BMSC) and chondrocytes in vitro. The degradation products of the polymer were nontoxic to cells in vitro. Subdermal implants of the PDI-sucrose matrix did not exhibit toxicity in vivo and did not induce an acute inflammatory response in the host. However, some foreign-body giant cells did accumulate around the polymer and in its pores, suggesting its degradation is facilitated by hydrolysis as well as by giant cells. More important, subdermal implants of the polymer allowed marked infiltration of vascular and connective tissue, suggesting the free flow of fluids and nutrients in the implants. Because of the flexibility of the mechanical strength that can be obtained in urethanes and because of the ease with which a porous microtexture can be achieved, this matrix may be useful in many tissueengineering applications.

Polyurethane and PTFE membranes for guided bone regeneration: Histopathological and ultrastructural evaluation

“…Foreign-body giant cells did accumulate around the polymer and in its pores, suggesting the degradation is facilitated by hydrolysis as well as by giant cells. More important, subcutaneous implants of the polymer allowed infiltration of vascular and connective tissue, suggesting the free flow of fluids and nutrients in the implants (7,14). The osteogenic tissue presence in the polymer surface and the membrane incorporation in the newly formed bone tissue were related (4,17).…”

“…The PTFE barriers have enough firmness against the soft tissue pressure, an important requirement for bone regeneration. The castor oil polyurethanes present an excellent biological compatibility (12)(13)(14). The observations on the inflammatory infiltrate in the samples treated with polyurethane barrier, showed an initial inflammatory reaction which decreased along the time (4), and the presence of inflammatory multinuclear giant cells (IMGC) (7).…”

Improved growth factor directed vascularization into fibrin constructs through inclusion of additional extracellular molecules

“…Prior studies have reported vascularizaton of tissue engineered constructs using both synthetic and naturally-derived constructs containing growth factors and/or cells (for examples see (Borges et al, 2003a;Borges et al, 2003b;Elcin and Elcin, 2006;Ganta et al, 2003;Kaigler et al, 2006;Murphy et al, 2004;Tanihara et al, 2001;Yao et al, 2004;Zisch et al, 2003)). However, the primary focus of these studies did not address the manner of directed vascular invasion into the matrix, but only upon the end extent of vacularization.…”

Progress and challenges in biomaterials used for bone tissue engineering: bioactive glasses and elastomeric composites

“…Polyol and sebacic acid are both endogenous monomers found in human metabolites (Ellwood [1995]; Natah et al [1997]; Sestoft [1985]); hence, PPSs generally show little toxicity to host tissues (Chen et al [2011a]; Wang et al [2003]). Poly(glycerol sebacate) (PGS) is the most extensively evaluated member of the PPS family, with most in vitro data demonstrating that PGS has a very good biocompatibility (Fidkowski et al [2005a]; Gao et al [2007]; Motlagh et al [2006]; Sundback et al [2005]; Sundback et al [2004]; Wang [2004]). Poly(xylitol sebacate) (PXS) has also been developed using xylitol, a well-studied monomer in terms of biocompatibility and pharmacokinetics in humans (Ellwood [1995]; Natah et al [1997]; Sestoft [1985]; Talke and Maier [1973]).…”