Purification systems and methods

1. A method of preparing hydrogel particles, the method comprising:

applying a solution including a plurality of hydrogel particles to a stir cell, a retentate side of a filter defining a lower surface of the stir cell, the filter having the retentate side and a permeate side; and

while stirring the solution within the stir cell, drawing a permeate from the permeate side of the filter using a pump at a first flow rate, the permeate including a subset of the plurality of hydrogel particles;

applying the permeate to a second stir cell, a retentate side of a second filter defining a lower surface of the second stir cell, the second filter having the retentate side and a permeate side; and

while stirring within the second stir cell, drawing from the permeate side of the second filter using a second pump at a third flow rate; and

collecting a second subset of hydrogel particles from the retentate side of the second filter after a period of time.

2. The method of claim 1 , wherein the pump is a syringe pump.

3. The method of claim 1 , dispensing a buffer solution at a second flow rate to the stir cell.

4. The method of claim 3 , wherein the first and second flow rate are approximately equal.

5. The method of claim 1 , wherein the velocity of the permeate across the filter is in a range of 0.01 cm/min to 0.17 cm/min, a range of 0.02 cm/min to 0.17 cm/min, a range of 0.05 cm/min to 0.16 cm/min, a range of 0.07 to 0.15 cm/min, or a range of 0.08 cm/min to 0.15 cm/min.

6. The method of claim 1 , wherein a velocity across the second filter is in a range of 0.01 cm/min to 0.17 cm/min, a range of 0.02 cm/min to 0.14 cm/min, a range of 0.02 cm/min to 0.11 cm/min, a range of 0.02 cm/min to 0.085 cm/min, or a range of 0.02 cm/min to 0.075 cm/min.

7. The method of claim 1 , wherein the second pump is a syringe pump.

8. The method of claim 1 , wherein the filter has a larger pore size than the second filter.

9. The method of claim 1 , wherein the filter and the second filter have approximately the same pore size.

10. The method of claim 9 , wherein the velocity across the filter is greater than the velocity across the second filter.

11. The method of claim 1 , wherein the average particle size of the second subset of hydrogel particles is in a range of 0.3 micrometers to 1.5 micrometers.

12. The method of claim 1 , wherein the coefficient of variance of the second subset of hydrogel particles is not greater than 5.0%.

13. A method of preparing hydrogel particles, the method comprising:

applying a solution including a plurality of hydrogel particles to a first stir cell, a retentate side of a first filter defining a lower surface of the first stir cell, the first filter having the retentate side and a permeate side, the first filter having a first pore size; and

while stirring the solution within the first stir cell,

dispensing a first buffer solution at a first flow rate to the first stir cell; and

drawing a permeate from the permeate side of the first filter using a first pump at a second flow rate, the permeate including a subset of the plurality of hydrogel particles;

applying the permeate to a second stir cell, a retentate side of a second filter defining a lower surface of the second stir cell, the second filter having the retentate side and a permeate side, the second filter having a second pore size; and

while stirring within the second stir cell,

dispensing a second buffer solution at a third flow rate to the second stir cell; and

drawing from the permeate side of the second filter using a second pump at a fourth flow rate; and

collecting a second subset of hydrogel particles from the retentate side of the second filter after a period of time;

wherein the first and second pore size are the same.

14. The method of claim 13 , wherein the first and second buffer solutions have the same composition.

15. The method of claim 13 , wherein the average particle size of the second subset of hydrogel particles is in a range of 0.3 micrometers to 1.5 micrometers.

16. The method of claim 13 , wherein the coefficient of variance of the second subset of hydrogel particles is not greater than 5.0%.

17. A plurality of particles wherein a subset of the plurality of particles comprise hydrogel and the plurality of particles has a coefficient of variance of not greater than 5%, wherein the particles are formed by the method comprising:

applying a solution including a plurality of hydrogel particles to a first stir cell, a retentate side of a first filter defining a lower surface of the first stir cell, the first filter having the retentate side and a permeate side, the first filter having a first pore size; and

while stirring the solution within the first stir cell,

dispensing a first buffer solution at a first flow rate to the first stir cell; and

drawing a permeate from the permeate side of the first filter using a first pump at a second flow rate, the permeate including a subset of the plurality of hydrogel particles;

applying the permeate to a second stir cell, a retentate side of a second filter defining a lower surface of the second stir cell, the second filter having the retentate side and a permeate side, the second filter having a second pore size; and

while stirring within the second stir cell,

dispensing a second buffer solution at a third flow rate to the second stir cell; and

drawing from the permeate side of the second filter using a second pump at a fourth flow rate; and

collecting a second subset of hydrogel particles from the retentate side of the second filter after a period of time.