Mechanical and thermal damage accumulation and recovery in cell and tissue products

A problem presented at the UK MMSG Loughborough 2008.

Presented by:
Dr. Yang Liu (Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University)
Prof David Williams (Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University)
CJW Breward, JR King, Y Liu, CP Please, JP Ward, JAD Wattis, DJ Williams

Problem Description

As cell and tissue products move closer to market increasing attention is being paid to their safe and effective transport to ensure that they are functional when they reach the market and patients. During the shipping process they are likely to encounter both sustained and transient mechanical and thermal stressing.

The study group is asked to develop a modelling framework, taking into account these stresses on tissues, to investigate ways of improving and optimising packaging design in order to maximise the safe transit of tissues products.

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Study Group Report

The variation in oxygen in a tissue stored in a plastic bag has been considered. We have found that at typical temperatures used for such chilled products the distance that oxygen diffuses into tissue before being completely consumed is around 5 cm. Hence for most situations the concentration of oxygen in the tissue will be spatially uniform and that the surrounding fluid in the bag will be at the same concentration. Analytical expressions have been derived that allow the validity of these approximations in any particular situation to be readily assessed.

By considering different types of bag material we have found that impermeable bags will allow thin tissue, about 5mm thick, to retain oxygen for about 2 days (extra fluid is not really necessary) Commercially available permeable bags make oxygen levels in the bag go to a steady state and for typical chilled conditions will ensure oxygen levels stay high for tissue as thick as 5cm.

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