Date of Award

Spring 1998

Document Type

Thesis

Degree Name

Master of Science in Biomedical Engineering - (M.S.)

Department

Biomedical Engineering Committee

First Advisor

Shlomo Gabbay

Second Advisor

David S. Kristol

Third Advisor

Angelo J. Perna

Abstract

Shelhigh Inc. (Millburn, NJ) has developed a new heparin binding technique to biological tissues. The technique seems to bind heparin to tissues in a more permanent fashion. Shelhigh's heparinized biological tissues are intended for use in long term implants. This investigation was undertaken to assess whether heparin leaching is prevalent when tissues are quarantine for long shelflife at room temperature, whether tissues maintained thromboresistance properties when in contact with plasma and to estimate heparin content of the tissues.

The study used anti-factor Xa assaying methods: clotting time and chromogenic factor Xa sensitive substrate in order to fulfill the aforementioned objectives. Anti-factor Xa assay was chosen because of its specificity. It characterized the role of heparin in the inactivation of factor Xa. Storage solutions containing heparinized pericardium tissues were mixed with equal volume of plasma in order to assess for heparin leaching. The average clotting time for these solutions was 22+/-.50 seconds. This result was in the range of clotting time of zero unit heparin in plasma. When Shelhigh's heparinized pericardium tissues were exposed to plasma at 37°C, neutralization of clotting factor Xa was accelerated as measured by the clotting time and chromogenic substrate method, and this was attributed to trace amounts of heparin released from the pericardium tissues. This demonstrated that Shelhigh's pericardium tissues have thromboresistance properties when in contact with plasma.

To estimate the heparin content on the pericardial tissues, conventional methods used to estimate heparin content on material surfaces was not applied. In this investigation, heparin is not immobilized on the tissue surfaces. Rather, the heparin is attached onto the matrix of the tissues. Therefore, to estimate heparin content on heparinized pericardium tissues, the tissues had to be dried, ground and incubated in plasma at 37°C . The estimated heparin content measured on tissue samples according to the clotting time and chromogenic substrate was observed to be varying, although all of the tissues were heparinized using standard manufacturing procedures.

The contribution of heparin released from Shelhigh's heparinized biological pericardium tissues stored in storage solution at room temperature was found to be negligible. When the tissues were in contact with plasma, neutralization of clotting factor Xa increased dramatically. Therefore, it can be concluded that heparin from Shelhigh's pericardium tissues markedly improves thromboresistance properties.

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