Nikhil Sethia’s research while affiliated with University of Minnesota, Duluth and other places

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Publications (5)


Figure 3. Sorting SC-β cell clusters by size. (a) The SC-β cell cluster (∼220 μm in diameter), highlighted with a dashed red circle, traversed inside the sorting device. The cluster was smaller than the cutoff size (250 μm) for sorting. (b) The smaller cluster traversed in a straight line toward the channel exit. No TSAW pulse was generated to actuate the smaller cluster. Another SC-β cell cluster (∼300 μm in diameter), highlighted with a dashed green circle, also entered the device. This newly entered cluster was larger than the size cutoff for sorting. (c) The smaller cluster exited the microchannel through outlet O1. (d) A 54 ms duration TSAW pulse selectively acted upon the larger cluster. (e) The larger cluster was pushed transverse to the main flow direction. (f) The larger cluster exited the microchannel through outlet O2. Arrows on the images represent the velocity of each cluster. Inlet flow rates for inlets I1−I3 were 66, 40, and 150 μL/min, respectively. The TSAW input power was 36.5 dBm. The scale bar is 250 μm.
Figure 4. Sorting of a clump of SC-β cell clusters from a discrete SC-β cell cluster. (a) The SC-β cell cluster sample had discrete SC-β cell clusters (highlighted by a dashed red circle) as well as clumps of SC-β cell clusters (highlighted by a dashed green circle). (b) The discrete cluster (∼240 μm) was smaller than the cutoff size of 250 μm and therefore not actuated. (c) The clump of clusters was identified as a single cluster that was >250 μm in size and therefore pushed transverse to the main flow direction. The smaller discrete cluster exited the microchannel through outlet O1. (d) The clump of clusters exited the microchannel through outlet O2. The scale bar is 250 μm.
On Chip Sorting of Stem Cell-Derived β Cell Clusters Using Traveling Surface Acoustic Waves
  • Article
  • Full-text available

February 2024

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39 Reads

Langmuir

Nikhil Sethia

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There is a critical need for sorting complex materials, such as pancreatic islets of Langerhans, exocrine acinar tissues, and embryoid bodies. These materials are cell clusters, which have highly heterogeneous physical properties (such as size, shape, morphology, and deformability). Selecting such materials on the basis of specific properties can improve clinical outcomes and help advance biomedical research. In this work, we focused on sorting one such complex material, human stem cell-derived β cell clusters (SC-β cell clusters), by size. For this purpose, we developed a microfluidic device in which an image detection system was coupled to an actuation mechanism based on traveling surface acoustic waves (TSAWs). SC-β cell clusters of varying size (∼100–500 μm in diameter) were passed through the sorting device. Inside the device, the size of each cluster was estimated from their bright-field images. After size identification, larger clusters, relative to the cutoff size for separation, were selectively actuated using TSAW pulses. As a result of this selective actuation, smaller and larger clusters exited the device from different outlets. At the current sample dilutions, the experimental sorting efficiency ranged between 78% and 90% for a separation cutoff size of 250 μm, yielding sorting throughputs of up to 0.2 SC-β cell clusters/s using our proof-of-concept design. The biocompatibility of this sorting technique was also established, as no difference in SC-β cell cluster viability due to TSAW pulse usage was found. We conclude the proof-of-concept sorting work by discussing a few ways to optimize sorting of SC-β cell clusters for potentially higher sorting efficiency and throughput. This sorting technique can potentially help in achieving a better distribution of islets for clinical islet transplantation (a potential cure for type 1 diabetes). Additionally, the use of this technique for sorting islets can help in characterizing islet biophysical properties by size and selecting suitable islets for improved islet cryopreservation.

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Pancreatic islet cryopreservation by vitrification achieves high viability, function, recovery and clinical scalability for transplantation

April 2022

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396 Reads

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69 Citations

Nature Medicine

Pancreatic islet transplantation can cure diabetes but requires accessible, high-quality islets in sufficient quantities. Cryopreservation could solve islet supply chain challenges by enabling quality-controlled banking and pooling of donor islets. Unfortunately, cryopreservation has not succeeded in this objective, as it must simultaneously provide high recovery, viability, function and scalability. Here, we achieve this goal in mouse, porcine, human and human stem cell (SC)-derived beta cell (SC-beta) islets by comprehensive optimization of cryoprotectant agent (CPA) composition, CPA loading and unloading conditions and methods for vitrification and rewarming (VR). Post-VR islet viability, relative to control, was 90.5% for mouse, 92.1% for SC-beta, 87.2% for porcine and 87.4% for human islets, and it remained unchanged for at least 9 months of cryogenic storage. VR islets had normal macroscopic, microscopic, and ultrastructural morphology. Mitochondrial membrane potential and adenosine triphosphate (ATP) levels were slightly reduced, but all other measures of cellular respiration, including oxygen consumption rate (OCR) to produce ATP, were unchanged. VR islets had normal glucose-stimulated insulin secretion (GSIS) function in vitro and in vivo. Porcine and SC-beta islets made insulin in xenotransplant models, and mouse islets tested in a marginal mass syngeneic transplant model cured diabetes in 92% of recipients within 24–48 h after transplant. Excellent glycemic control was seen for 150 days. Finally, our approach processed 2,500 islets with >95% islets recovery at >89% post-thaw viability and can readily be scaled up for higher throughput. These results suggest that cryopreservation can now be used to supply needed islets for improved transplantation outcomes that cure diabetes.


Citations (1)


... Furthermore, it will be relevant to pair large-scale manufacturing with islet cryopreservation. Many groups are investigating efficient methods to cryopreserve islets, aiming for good viability and the ability to ship globally [97,98]. ...

Reference:

Islet Cell Replacement and Regeneration for Type 1 Diabetes: Current Developments and Future Prospects
Pancreatic islet cryopreservation by vitrification achieves high viability, function, recovery and clinical scalability for transplantation

Nature Medicine