An improved peel test method for measurement of adhesion to biomaterials.

Adhesion of tissues to biomaterials is desirable to prevent bacterial proliferation and for epithelial/transmucosal sealing of transcutaneous appliances, but can be counter-productive elsewhere, e.g. implants contacting tendons or maxillofacial subcutaneous tissue. It is therefore important to gauge adhesion strength of tissues to biomaterials before clinical use. Peel-testing is widely used for industrial product adhesion monitoring, but has rarely been applied biomedically. Here we describe peel-testing instrumentation designed for testing adherence of soft tissues to biomaterials. It offers the advantage that a 90 degrees angle between peel and substrate is maintained, simplifying determination of applied normal forces separating tissue layers from material surfaces. The device is portable and can be brought directly to the specimen removal site. This minimizes time delays between explantation and testing, maintaining the tissue/biomaterial interface in the freshest possible state closely approximating in vivo conditions, and so avoids measurement artifacts. So far, the instrument has been used to test adhesion of tape to a biomaterial surface (for determining the device's technical performance), assess strength of tissue adhesives, and measure adhesion of subcutaneous tissue to orthopaedic biomaterials. However, its versatility suggests additional applications for the peel-tester where adhesion of soft tissue to biomaterials is of interest.

[Histologic investigations of PTFE-surface acting for direct tissue contact on implants (author's transl)]. / Histologische Untersuchung eines PTFE-Oberflächenbelages zur Erreichung eines direkten Gewebskontaktes am Implantat.

Generally, implants give rise to toxic reactions and favour the formation and propagation of local infections. Adherance of the soft tissue to the implant prevents the development of fluid filled cavities, thus being of particular interest as a prophylactic measure in arresting spread of infections. Teflon cylinders with an etched surface have been investigated by optical and electron microskopic means following subcutane implantation in mice. We were able to demonstrate closed tissue contact. Signs of toxic tissue reactions were completely absent.

[A method of quantitative determination of tissue tolerance in decreased relative movement between implant and tissue]. / Methode zur quantitativen Auswertung der Gewebsverträglichkeit bei verminderter Relativbewegung zwischen Implantat und Gewebe.

A method of testing in vivo tissue tolerance to different implant materials is presented. It aims at reduction of variance due to mechanical irritation at the tissue-implant interface through the use of cylindrical implants with grooves. The special type of histological preparation which is necessary and problems encountered when using these techniques are described. The numerical evaluation of round cells and foreign body giant cells seems to give uniform results with low variance, which could be of interest for standard testing of material.