Physicochemical characterization and in vivo blood tolerability of cast and extruded biomer

Abstract

Solution grade and extruded grade Biomer (SB and EB, respectively) are polyurethanes that have been suggested for use in biomedical applications. The bulk materials were examined by elemental analysis, differential scanning calorimetry, thermomechanical testing, and stress-strain testing. The extruded grade material has a lower soft segment molecular weight (650 g/mol) than the solution grade material (2000 g/mol). As a result of its higher molecular weight, the soft segment phase of SB is semicrystalline in the solid state. The hard segments of the extruded grade material are chain extended with water yielding a lower urea concentration than in the solution grade material in which the hard segments are chain extended with diamines. Chemical structures for the two materials consistent with elemental analysis, urea/urethane ratios and thermal and mechanical data, are proposed. X-ray photoelectron spectroscopy (ESCA) was used to analyze the surfaces of extruded grade Biomer, solution grade Biomer cast on the inner surface of polyethylene tubing, and extruded grade Biomer dissolved in DMA and similarly cast on polyethylene (CB). Soft segment concentrations were highest on the EB surface and lowest on the SB surface. Soft segment concentrations on the EB surface were higher than on the CB surface, indicating that the method of fabrication affected the composition of the surface layer. The three materials were tested for blood tolerance in a canine femoral arteriovenous shunt configuration. Blood compatibility was correlated with increasing concentration of polyether soft segments on the surface.

Polyurethane Shape‐Memory Polymers Demonstrate Functional Biocompatibility In Vitro

“…Variations in PEU blood compatibility has been observed, with improved thromboresistance correlating to more alkylated soft segments, [30] higher soft-segment content on the surface, [31] well developed micro-phase separation, and surface treatment such as grafted sulfonate groups. [32,33] At the same time, there is still some controversy as to whether or not polyurethanes evoke an 'immune' response.…”

Selected topics in biomedical polyurethanes. A review

“…The polymer showed good long-term in vivo stability, good mechanical properties [163], and relatively good longterm blood compatibility [162,164].…”

“…Extruded-Grade Biomer based on MDI:PTMO and water, with good blood compatibility [162] is no longer available commercially.…”

Synthesis and characterization of methoxypolyethyleneglycol and lauric acid grafted novel polyurethanes for controlled release of nifedipine

“…[7][8][9][10] Especially, poly (ether urethanes) have been widely studied due to their excellent physical properties such as flexibility, glass transition temperature (T g ), and degradation characteristics in addition to resistance for infectiousness and superior compatibility. [11][12][13] Polyethylene oxide (PEO) is a well-known and useful hydrophilic biomaterial, which under aqueous physiological conditions, has a high kinetic chain mobility and large thermodynamic steric volume, 14 leading to the repulsion of almost all kinds of foreign adherence and adsorption. A major problem to achieve an effective drug-targeting polymer to the specific sites within the body is the sequestration of intravenously administered colloidal carriers by cells of the mononuclear phagocytic system (MPS).…”