I have been trying to inject cells into the internal lumen of spheroids growing in a collagen gel using an oocyte microinjector and very thin glass pipets. However, whenever I try to poke the spheroids, they (and the surrounding collagen) dogde away from the pipet tip. There seems to be no way for holding them in place, consequently, the tip does not really penetrate them and the cells are delivered at the outside of the spheroid, not into its lumen. I cannot change the collagen gel density since this recipe has been established for them and other percentages of collagen etc. would change their growth conditions.
Do you have any ideas ?
Thanks in advance !