Question

1. You prepared a dilution 1 in 2 of trypsinized CHO-K1 cells. Then, you took an aliquot of the cell suspension and counted the cells using a hemocytometer. There were 75 cells in the 16 little squares. Please explain how to get each!

a. Calculate the concentration of the cells prior to the dilution. Show your calculations. Use scientific notation to express the result.

b. Now, you want to seed a 25cm² flask with 750,000 cells. Calculate how many ml of the original cell suspension you will use

c. If the final volume of incubation is 4ml. How many ml of complete medium you will need to add?

Answer 1

1.- Data:
Dilution 1: 2
We have 75 cells counted in the 16 small squares.
If we count 75 cells in 16 small squares, the number of cells per square will be 75/16 = 4.68.
If in a volume of 0.00025 mm3 (surface of the small square) there are 4.68 cells, in 1 mm3 we will have:
0.00025mm3 ------------ 4.68
1 mm3 ---------------------- X
X = 18,720
18,720 will be the number of cells per mm3 of undiluted cell solution.
However, a 1: 2 dilution was made, therefore we will have to multiply the result (18,720) by 2, with which we will obtain the total of cells per each mm3 of sample (undiluted).
18,720 x 2 = 37,440
That is, we will have 37,440 cells per mm3 of sample