This thesis is a summary of doctoral work in the area of magnetic cell sorting. Four main topics have been addressed: 1) Proof of concept of the magnetic sorting of porcine islets of Langerhans in a clinical setting; 2) optimization of islet sorting by mathematical models and custom reagents; 3) determination of the sensitivity of porcine islets to physical stress; and 4) model predictions for the potential of nano-scale magnetic separations of biological materials.
The author and his collaborators at the Diabetes Institute have investigated the use of magnetic Dynal® Dynabeads® to preferentially enrich pancreatic islets from enzymatic organ digests. This technique offers the possibility immediately separate labeled islets with a quadrupole magnetic sorter (QMS). Magnetic sorting could replace density gradients as the primary means of purifying islet grafts for type 1 diabetics by increasing yield and minimizing cellular exposure to chemical and physical stress.
Force-balance models were used to ascertain how much labeling would be required to isolate islets from pancreatic tissues via magnetic sorting. A fast and simple technique was developed to synthesized magnetic particles that satisfy the optimal label properties described by the separation models.
A contractional flow device, which subjects cells to well-defined hydrodynamic forces, has been used to assess the vulnerability of porcine Islets of Langerhans to shear stresses that occur in any physical sorting device. This thesis reports on the author’s collaborative work, with the Diabetes Institute, to quantify the upper limit of physical stress endurable by porcine islets. This knowledge is crucial for the optimization of the QMS channels and run conditions.
Magnetic separations are limited by the magnitude of the magnetic field gradient. This may be increased, ceteris paribus, by reducing the length scale of the device. In collaboration with the Cleveland Clinic, miniaturized QMS designs have been modeled to maximize the gradient and uniformity of the magnetic field. This modeling resulted in inexpensive demonstration devices with significantly higher field gradients, useful for probing the versatility of magnetic separation of proteins.