Application of magnetic particle tracking velocimetry to quadrupole magnetic sorting of porcine pancreatic islets

Abstract

Magnetic isolation is a promising method for separating and concentrating pancreatic islets of Langerhans for transplantation in Type 1 Diabetes patients. We are developing a continuous magnetic islet sorter to overcome the restrictions of current purification methods that result in limited yield and viability. In Quadrupole Magnetic Sorting (QMS) islets are magnetized by infusing superparamagnetic microbeads into islets’ vasculature via arteries that serve the pancreas. The performance of the islet sorter depends on the resulting speed of the islets in an applied magnetic field, a property known as magnetophoretic mobility. Essential to the design and successful operation of the QMS is a method to measure the magnetophoretic mobilities of magnetically infused islets. We have adapted a Magnetic Particle Tracking Velocimeter (MPTV) to measure the magnetophoretic mobility of particles up to 1000 microns in diameter. Velocity measurements are performed in a well-characterized uniform magnetic energy gradient using video imaging followed by analysis of the video images with a computer algorithm that produces a histogram of absolute mobilities. MPTV was validated using magnetic agarose beads serving as islet surrogates and subjecting them to QMS. Mobility distributions of labeled porcine islets indicated that magnetized islets have sufficient mobility to be captured by the proposed sorting method, with this result confirmed in test isolations of magnetized islets.

Magnetic particle characterization—magnetophoretic mobility and particle size

“…In conclusion, a method has been researched for the simultaneous determination of particle count, particle diameter, and magnetophoretic mobility using dark-field videomicroscope velocimetry with image storage, processing, and analysis software using the commercial Hyperflux particletracking velocimeter (30). This study has demonstrated an available capability to analyze magnetic particles and cells that has been heretofore limited to only a handful of laboratories (15,18,24,(31)(32)(33)(34) with one-of-a-kind instruments. With correct operator-based settings, measurements of magnetophoretic mobility and particle count are robust, and diameter can be determined on the basis of calibration.…”

“…Noncommercial instrumentation has been applied by specific investigators to the measurement of magnetophoretic mobility of individual particles and magnetically labeled cells by particle tracking velocimetry (17)(18)(19)(20). In certain cases, these measurements are directly applied to the establishment of parameters for the enrichment of magnetically labeled cells in flowing devices (21)(22)(23)(24) or to the quantification of cell surface markers (25,26).…”

Continuous Quadrupole Magnetic Separation of Islets during Digestion Improves Purified Porcine Islet Viability

“…The QMS inlet flow rate (out of the buffer bag) was matched with the flow rate of tissue leaving the digest chamber to maintain a continuous purification process. The mechanism for the QMS process using this system is described in detail by Kennedy et al and others [15, 40, 54]. Briefly, as the tissue flow stream entered the QMS separator column, it is met with a parallel fresh stream of HBSS solution.…”

Magnetic separation of encapsulated islet cells labeled with superparamagnetic iron oxide nano particles

“…A specifically designed cell sorter capable of purifying cells labeled with magnetic nanoparticles is already available . This method has been described in the literature as quadruple magnetic sorting and has been successfully applied to several separation and purification applications for particles up to a size of 350 μm . To enable quadruple magnetic sorting for magnetic separation of encapsulated islets, the device must be adapted to work with a maximum particle size of 600 μm.…”