A rapid and sensitive method to measure numbers of live cells in alginate capsules following depolymerization with ethylenediaminetetraacetic acid

Cell encapsulation in alginate prevents migration and extends cell survival in vivo while allowing the secretion of factors across semipermeable capsules. Confocal microscopy is used to measure numbers of cells/capsule, but is time-consuming and limited to capsule diameters <0.4 mm for accurate counting. A rapid, accurate and inexpensive method for measuring the number of cells per capsule by using 50 mM ethylenediaminetetraacetic acid to collapse capsules into a single plane was developed. This assay was used to accurately count the number of live cells/capsule for capsules crosslinked with 50 mM BaCl2 with diameters up to 0.8 mm. This assay is ideal for counting cells/capsule during optimization to scale up the production of encapsulated cells, and for determining dosing in translational studies.