Studies on the effect of virtual crosslinking on the hydrolytic stability of novel aliphatic polyurethane ureas for blood contact applications

Abstract

The effect of virtual crosslinking on the hydrolytic stability of completely aliphatic novel poly(urethane ureas), HFL9-PU1 (hard-segment content 57.5%) and HFL13-PU2 (hard-segment content 67.9%) based on 4,4'-methylene bis(cyclohexyl isocyanate) (H(12)MDI)-hydroxy-terminated polybutadiene-1,6-hexamethylene diamine, was studied. Fourier transform infrared-attenuated total reflectance and wide-angle X-ray diffraction studies revealed hydrogen-bonding interaction and microphase separation and formation of crystallites by short- and long-range ordering in hard-segment domains. Three-dimensional networks from hydrogen bonding in the present polymers lead to virtually crosslinking and insolubility. These polymers were noncytotoxic to L929 fibroblast cells. The hemolytic potential is below the accepted limit. The studies on in vitro biostability in Ringer's solution, phosphate buffered saline, and papain enzyme revealed no weight loss. The infrared spectral studies revealed changes in the surface, especially on HFL9-PU1 aged in Ringer's solution and phosphate buffered saline, and no changes when aged in papain. The marginal changes noticed in tensile properties were attributed to the changes in degree of hydrogen bonding and associated rearrangement of molecular structure in the bulk. The results revealed that the lesser the crosslinking in virgin polymer, the higher the crosslinking in aged polymer and vice versa. Increased crosslinking during aging provided increased tensile properties in the aged polymer over the virgin polymer and vice versa. For comparison, an aliphatic polyetherurethane urea (HFL16-PU3) was also synthesized using poly(oxy tetra methylene glycol) in addition to the above reactants. Though both HFL9-PU1 and HFL16-PU3 contained the same hard-segment content, the aged sample of the latter showed decreased tensile properties with increased crosslinking during aging in contrast to the former. This was attributed to less microphase separation in the virgin HFL16-PU3 polymer.

A new generation of high flex life polyurethane urea for polymer heart valve—Studies on in vivo biocompatibility and biodurability

“…A novel proprietary segmented polyurethane urea, HFL18‐PU, was synthesized using a cycloaliphatic diisocyanate, 4,4′‐methylene bis(cyclohexyl isocyanate) (H 12 MDI), an aliphatic unsaturated hydrocarbon polyol hydroxyl terminated polybutadiene (HTPBD), and hexamethylene diamine (HDA), toluene‐dimethyl acetamide solvent and dibutyl tin laurate catalayst as reported earlier 9–11. Initially the prepolymer was prepared using HTPBD and H 12 MDI, and the prepolymer was chain extended with HDA.…”

“…The in vitro calcification of candidate polyurethane urea was evaluated using metastable calcium phosphate solution as reported elsewhere 14, 15. Polyurethane urea strips of rectangular shape (0.5 × 5 cm 2 ) were stressed equally by bending the specimens and immersed in calcium phosphate metastable solution in screw capped test tubes.…”

“…The cytotoxicity was assessed by comparing the cell morphology with negative and positive control. Cell viability was evaluated by MTT assay 14, 16. The polymer was extracted (1 cm 2 material/mL) in cell culture medium for 24 h at 37°C and used to interact with the fibroblast cells.…”

Enzymatic hydrolysis of lysine diisocyanate based polyurethanes and segmented polyurethane ureas by various proteases

“…b (Content of solubilized carbon)/(content of carbon in polymer) Â 100, (D/T in Table 3). reported that completely aliphatic poly(urethane urea) based on 4,4 0 -methylene biscyclohexyl isocyanate/hydroxyterminated polybutadiene/1,6-hexamethylene diamine did not degrade by papain after 30 days at 37°C [13]. These facts can be explained by the surface hydrophobic properties of the polymers.…”

“…The enzymatic degradation of segmented polyurethanes and polyurethane ureas has been studied by several groups of researchers in the field of biomedical materials. The enzymes mainly used are chymotrypsin [6][7][8][9], papain [10][11][12][13][14], and cholesterol esterase [15][16][17], to ensure the cleavage of urethane bonds and the structure of the degradation products. Meanwhile, lysine diisocyanate (LDI) based polyurethanes, which are considered to give non-toxic degradation products, are suitable biomaterials for tissue engineering, such as scaffold materials [3,6,9,[18][19][20].…”