CHO Cell Encapsulation & Incubation in Gelatin Particles
Cell studies by encapsulation, incubation, and manipulation in droplets is gaining popularity due to the ease afforded by droplet technology. Microfluidic systems further lend the advantage of producing extremely consistent droplets with size range limited to 1% size variation, making cell encapsulation still more attractive.
Cell encapsulation in picoliter volume droplets is demonstrated in this application note using Dolomite’s Droplet system. Thereafter, the viability of the encapsulated cells is assessed by incubating and monitoring cell growth. A premixed cell suspension is made consisting of 10% Gelatin (highly viscous) in aqueous cell media. A cross linker is added shortly before start of test. This solution is used as the droplet phase in a droplet system to create approximately 200 μm diameter (~ 5 nanoliter) droplets at approximately 10 Hz. Pico-Surf2TM an immiscible fluorinated organic hydrocarbon carrier containing a biocompatible surfactant stabilizes the emulsion. The gelatin upon curing becomes a soft solid hydrogel after which the particles are re-suspended in fresh cell medium. The cells continue to grow within this gel matrix.
Cell viability is an important concern in encapsulation systems. To assess this, the cell encapsulated particles are incubated for 3 weeks. A few particles are taken intermittently and imaged using high magnification microscopy. Only a few sparse cells per particle are visible initially. At week 1, the single cells are seen to grown into clumps. The rate of increase in clump size rises with time – binary fission theory suggests growth rates to be exponential. At 3 weeks, the colony is seen to break out of the particles due to increased population density, as well as due to collagen degradation from the cell secretion.
The results show that the Droplet system in the configuration presented in this application note is well suited for use in CHO cell encapsulation applications. The cells are shown to survive well the encapsulation process, with no visible adverse effect suggesting no material incompatibility.