In vivo biocompatibility and biostability of modified polyurethanes

Abstract

Modified segmented polyurethanes were examined for biostability and biocompatibility using an in vivo cage implant system for time intervals of 1, 2, 3, 5, and 10 weeks. Two types of materials were used: polyether polyurethanes and polycarbonate polyurethanes. Two unmodified polyether polyurethanes (PEUU A' and SPU-PRM), one PDMS endcapped polyether polyurethane (SPU-S), and two polycarbonate polyurethanes (SPU-PCU and SPU-C) were investigated in this study. Techniques used to characterize untreated materials were dynamic water contact angle, stress-strain analysis, and gel permeation chromatography. Cellular response was measured by exudate analysis and by macrophage and foreign body giant cell (FBGC) densities. Material characterization, postimplantation, was done by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) in order to quantify biodegradation and scanning electron microscopy (SEM) to qualitatively describe the cellular response and biodegradation. The exudate analysis showed that the acute and chronic inflammatory responses for all materials were similar. Lower FBGC densities and cell coverage on SPU-S were attributed to the hydrophobic surface provided by the PDMS endgroups. The polycarbonate polyurethanes did not show any significant differences in cell coverage or FBGC densities even though the macrophage densities were slightly lower compared to polyether polyurethanes. By 10 weeks, biodegradation in the case of PEUU A' and SPU-PRM was extensive as compared to SPU-S because the PDMS endcaps of SPU-S provided a shield against the oxygen radicals secreted by macrophages and FBGCs and lowered the rate of biodegradation. In the case of polycarbonate polyurethanes, the oxidative stability of the carbonate linkage lowered the rate of biodegradation tremendously as compared to the polyether polyurethanes (including SPU-S). The minor amount of biodegradation seen in polycarbonate polyurethanes at 10 weeks was attributed to hydrolysis of the carbonate linkage.

Foreign body reaction to biomaterials

“…The soft segment of polyether polyurethanes is known to undergo degradation. [86][87][88][89][90][91][92][93][94][95][96][97][98] This phenomenon will be discussed in the next section.…”

“…These polyurethanes have soft segments that are either polyether or polycarbonate but, more importantly, have short chain molecules attached to the polymer chain ends (SME, surface modifying endgroups) such that when fabricated, these adhesion inhibiting molecules are present at the surface of the biomaterial at the tissue/material interface. [97][98][99][100] Significant efforts to molecularly engineer the polyurethanes such that they are biostable and do not undergo biodegradation are being carried out. The excellent biocompatibility and superior mechanical properties of segmented polyurethane elastomers support these efforts to molecularly design non-biodegradable biostable polyurethanes.…”

Segmented poly(esterurethane urea)s from novel urea–diol chain extenders: Synthesis, characterization and in vitro biological properties

“…Having been used in the medical field for almost half a century, segmented polyurethanes (SPU) remain one of the most common groups of biomaterials applied to the fabrication of implantable devices, owing to the possibility of tailoring their physical properties [1]. The development of biodegradable and biocompatible SPU and polyurethane networks with labile moieties susceptible to hydrolysis in the polymer backbone has been a subject of considerable interest in recent years [2][3][4][5].…”

“…In this sense, a careful selection of monomers can lead to a biodegradable SPU whose properties can be tailored to many different biomedical applications. Depending on their mechanical properties, chemical composition and surface characteristics, biodegradable SPU can potentially be used in designing cardiovascular implants, drug delivery devices, non-adhesive barriers in trauma surgery, injectable augmentation materials and tissue adhesives [1,6].…”

Synthesis and Properties of Segmented Poly(urethane-urea)s Containing Phosphorylcholine Moiety in the Side-Chain

“…6 Therefore, several studies of the surface or chemical modification of SPU have been conducted to improve the blood compatibility through reducing the adhesion of cells and proteins. [7][8][9][10][11] On the other hand, 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer has been developed as an excellent blood compatible material, which efficiently reduces the adhesion of cells and proteins on the polymer surface. 12,13 The MPC polymer was designed based on the inspiration from the chemical structure of phospholipids polar group in biomembrane.…”