Newly designed Tissue/cell storage bag for cryopreserved homograft by application of CO2 laser welding technique.

Abstract

Cryopreserved heart valve allografts (homografts) are packed in heat-sealed fluorinated ethylene propylene (FEP) film bag and stored under vapor phase of liquid nitrogen. Supply of those specific storage bags are very limited, and obtained from limited industries. On the other hand, sealing technique by CO2 laser enables secure closure using its high temperature (over 500 °C) beam, gives flexibility in sealing line design (not only straight but also any kind of curve or circle), and wider source of product supply can be expected with reasonable cost. This study is to assess the quality of newly designed tissue / cell storage bag for cryopreservation as domestic products by CO2 laser welding method, which enables drawing any types of sealing line (straight, curve) under any ambient temperature. Using CO2 laser (Firestar V40, Synrad Co. Ltd, USA), we designed homograft storage bag with FEP films (0.1 mm thick) under several sealing conditions (sealing width, laser intensity), with fixed operating speed (5 mm·s-1). We assessed the quality of welding line, and changes in neighboring film condition. Stability of welding was best achieved by laser intensity at 10.5 Watt (W), and acceptable at 13.5 W. Tensile test revealed that the line was stable against 20 Newton when sealing was done with laser intensity more than 10.5 W. We have also assessed structural changes of the sealing line and the neighboring film by polarizing microscope, which revealed fine foam formation at sealing line when laser intensity was high. CO2 laser sealing method is feasible in its stability and strength, and quality of the line was achieved when performed by appropriate laser intensity.