(117c) An Automated Tissue Digester for Pancreatic Islet Production

Lu, Z. - Presenter, Auburn University
Boland, E., Techshot, Inc.
Todd, P. W., Techshot, Inc.
Hanley, T. R., Auburn University

Pancreatic digestion is the primary step in preparing islets of Langerhans for clinical transplantation for restoring euglycemia in Type-1 Diabetes patients.  In 1988, Ricordi et al. developed a semi-automated method in which pancreas fragments and glass balls were placed into a cylindrical vessel to form a closed-loop recirculation and dissociation system, operated by intermittent manual shaking of the vessel.  However, the yield of islets from this technique tends to be variable and depends on several parameters.  Collagenase-containing enzyme blends used for releasing islets from the exocrine tissue also produce variable results and can cause damage to islets.  Operator function (shaking the vessel by hand) also produces variability from case to case.  An automated digestion unit capable of producing reproducible operating parameters is needed for the consistent preparation of islets.

This research focuses on the incorporation of an automated horizontally rotating digester (MDR) consisting of a rotating outer cylindrical shell and a counter-rotating core both with hemispherical baffles.  This configuration is designed to enhance the turbulent effect and contact area between tissue fragments and walls.  In the digestion process, the rotation of the inner core is adjusted for optimum dissociation, and independently the exterior wall rotation is optimized to maintain particles in suspension without centrifuging them.  Rotation speeds are also adjusted as particle size distribution is diminished during digestion.  In addition, a discrete phase model in FLUENT is used to simulate the flow patterns and track the tissue particles in the MDR and Ricordi chamber.  The computational fluid dynamics (CFD) analysis and comparison of flow variable contours indicate that MDR has predictable, controllable fluid shear environment and optimized differential rotation mode at 120 ml/min velocity inlet and 100 rpm rotation speed in opposite directions.  The agreement between experimental and CFD predicted results is shown by analysis of viable islets under a Grasshopper® digital camera with an ultra-fast 800Mb/s digital interface.  Finally, the validation of the model is performed through the comparison of simulation results with experimental data obtained from porcine pancreatic tissue digestion.


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