Fibrin glue has good biocompatibility, but its adhesive strength is relatively low. The modified GRF glue developed in the 1960s appeared to be a viable solution. Further modifications were made in the 1980s because of the continued controversy concerning the possible carcinogenicity and mutagenicity of formaldehyde. These modifications were aimed at replacing the formaldehyde component with aliphatic dialdehydes. Ennker etal.79 studied the use offormaldehyde-free collagen glue in experimental lung gluing. They replaced the formaldehyde component of GRF glue with two less toxic aldehydes, pentanedial and ethanedial. In this manner, two-component glue was produced. The first component, a gelatin-resorcinol condensate, has the viscosity of honey, while the second component, a mixture of dialdehydes, is a watery solution. To evaluate the adhesive strength of this new glue, GR-DIAL, lung incisions in rabbit hybrids were glued together. Each group (n = 5) was examined histologically after two days and one, two, and four weeks. The glue disintegrated gradually with good bioresorption when the incision was closed with a thin layer of glue. The healing process was favourable, indicating good biocom-patibility. Therefore, GR-DIAL glue was capable of enhancing the use of surgical glues in the field of thoracic surgery by enabling surgeons to close larger parenchymal lesions than with fibrin glue.
Among the dialdehydes, pentane-1.5-dial and ethanedial (IUPAC nomenclature for glutardialdehyde and glyoxal) proved to be the most effective in earlier experiments. In vitro trials on lung parenchyma indicated that fibrin glue, which of all the clinically applied glues was currently the most widely used, had the least adhesive strength. In addition to fibrin glue and GRF glue, cyanoacrylate glue and various pentane-1.5-dial/ethaneidal ratios of GR-DIAL were also tested in different experimental settings. These in vitro evaluations indicated that cyanoacrylate glue had the strongest adhesive power, but had the disadvantage of becoming a stiff layer of artificial material with no elastic properties, forming a nearly impenetrable barrier in the region of the elastic lung tissue. Its biocompatibility was poor, and its adhesive power decreased in humid conditions. Therefore, cyanoacrylate glue was ruled out as the optimal adhesive for use in lung parenchyma. After cyanoacrylate glue, GRF glue showed the second-best adhesive power in dry conditions. On humid surfaces, however, GRF glue was surpassed by the adhesive strength of GR-DIAL glue. If pentane-1.5-dial alone was used as the hardening component, the adhesive power of GR-DIAL reduced slightly. In addition, as ethanedial is less toxic than pentane-1.5-dial, itwas not desirable to use only pentane-1.5-dial for the second component. Although these two aldehydes are less toxic than formaldehyde, it was concluded that it would be necessary to perform extensive toxicity studies, including resorption kinetics before clinical use can be sought.
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