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The in vitro cytotoxicity and in vivo biocompatibility of poly(propylene fumarate-co-ethylene glycol) [P(PF-co-EG)] hydrogels were assessed in order to investigate the influence of poly(ethylene glycol) molecular weight and copolymer composition. These materials have application as injectable cardiovascular implants; cytotoxicity due to leachable products, as well as inflammation caused by the biomaterial itself, may ultimately affect the biocompatibility of the implant. We utilized a 7-day in vitro cytotoxicity assay to quantify cell density and cellular proliferation in the presence of copolymer films. The copolymer films exhibited slight to moderate cytotoxicity toward cultured endothelial cells, showing 20-86% viability relative to controls. Cell viability increased with an increasing weight percent of PEG or, to a lesser extent, the molecular weight of PEG. In vivo biocompatibility was assessed using a cage implantation model over a 21-day time period. This system was used to characterize the local cellular and humoral inflammatory response in the surrounding exudate, as well as the size and density of macrophages adherent to the material itself. All copolymer formulations exhibited excellent biocompatibility relative to controls with no significant differences in total leukocyte count among the different formulations. The in vivo inflammatory reaction displayed normal wound healing over 21 days as shown by a progressive decrease in both leukocyte concentration and enzymatic activity. The surface coverage of the copolymer films remained relatively constant from 7 to 21 days. There were no cells larger than 0.003 mm2, which was previously shown to be the threshold value for foreign-body giant cells. These data suggest that P(PF-co-EG) hydrogels have potential for use as injectable biomaterials.

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The degradation of poly(propylene fumarate-co-ethylene glycol) hydrogels was examined in vitro in phosphate-buffered saline at pH 7.4 and in vivo in a subcutaneous rat model. These hydrogels have potential application as biodegradable, injectable cardiovascular stents, and, as such, their mass loss, dimensional changes, mechanical properties, morphology, and biocompatibility over a 12-week time course were evaluated. Three formulations were fabricated: one base formulation consisting of 25% (w/w) PEG, molecular weight 4,600; one high weight percent PEG formulation with 50% (w/w) PEG; and one high molecular weight PEG formulation, molecular weight 10,500. All three formulations showed significant weight loss (between 40 and 60%) on the first day due to leaching of the uncrosslinked fraction. Further weight loss was observed only for the low weight percent PEG copolymers in the in vivo case, and a slight increase in volume was observed due to degradative swelling. The mechanical properties of the P(PF-co-EG) hydrogels decreased significantly in the first 3 weeks, showing the biphasic pattern typical of bulk degradation. In vitro, the hydrogels showed at least a 20% retention of their initial ultimate tensile stress after 3 weeks. The dynamic mechanical properties showed similar retention, with the in vivo mechanical properties differing from the in vitro properties only after 6 weeks of degradation. Differences in PEG molecular weight appeared to have little effect, but increasing the weight percent PEG decreased the rate of degradation both in vitro and in vivo. The morphology of the copolymer films, based on scanning electron microscopy observation, was not significantly different either among the three formulations or over the time course of the study, suggesting there were no macroscopic structural changes during this time period. The P(PF-co-EG) hydrogels demonstrated good initial biocompatibility, showing responses characteristic of biomaterial implants.

We have compiled the nucleotide sequences and their amino acid translations from a total of 89 Killer Immunoglobulin-like Receptor (KIR) alleles, derived from 17 different KIR genes. The alignments use the KIR3DL2*001 allele as a reference sequence. Each of the KIR sequences included in these alignments has been checked and where discrepancies have arisen between reported sequences, the original authors have been contacted where possible, and necessary amendments to published sequences have been incorporated into this alignment. Future sequencing may identify errors in this list and we would welcome any evidence that helps to maintain the accuracy of this compilation.

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