V&P Scientific has recently added a new line of stir elements which are capable of re-suspending cells or particles and keeping cells or particles in suspension without causing cell damage.

 The VP 772FN-25-55TF-150 {Tuning Fork} and the VP 772FN-20-21CV-150 {Torpedo-Cross} were both designed to be autoclavable. They fit inside 50ml centrifuge tubes to mix the constituents. The outer shape of both stir elements matches the inside topography of the tube.  Both designs allow you to take samples while the tube is being stirred. The Torpedo-Cross design has a lower profile and therefore requires less dead-volume than the tuning fork design. Both stir elements use two VP 782N-12-150  Neodymium Iron Boron magnetic discs.

These stir elements have optimal performance with our VP 710D2 Multi Stirrus™. Both designs are well suited for mixing different solutions, resuspension of cells, or dissolution of powders. When these stir elements are used in conjunction with the VP 710D2 Multi Stirrus™ more than 24 50ml conical tubes can be mixed simultaneously. The stirring action does not shear or damage fragile cells even after continuous mixing.

 In a test experiment using human promyelocytic leukemia cells, 35ml samples were removed from a tissue culture flask and placed into three different 50ml conical tubes.

The 1st tube was allowed to sit at room temperature with no stirring. The 2nd tube was stirred at 350 RPM with the Tuning Fork design{VP 772FN-25-55TF-150}. The 3rd tube was stirred at 350 RPM with the new Torpedo-Cross design {VP 772FN-20-21CV-150}.

The cells in each tube were counted within 5 minutes of being removed from the tissue culture flask. They all had comparable cell counts with percent viability greater than 98%, as measured by Trypan blue exclusion. The three tubes were then allowed to incubate at room temperature for approximately one hour, with 2 tubes being continuously stirred at 350 RPM during the incubation.

 The cell counts taken from the tubes being stirred remained consistent with the counts that were taken within the first 5 minutes of removal from the tissue culture flask. The counts from the tube with no stir element showed a drop of 40% due to the settling of the cells. 

 The three tubes were then centrifuged for 5 minutes at 500 RPM to pellet the cells. The 2 tubes with stir elements were returned to the stir device and stirred for 5 minutes in an attempt to resuspend the pelleted cells. The counts from the tube with no stir device dropped by over 99%, consistent with the pelleting of the cells. The tubes being stirred returned to the counts comparable to those taken within the first 5 minutes of removal from the tissue culture flask. There was no evidence of cell damage seen in any tube as measured by Trypan blue dye exclusion; the percent viability remained greater than 98% in all three tubes.

 In a second test experiment, both stir elements were used to mix heavy glitter particulates. The Torpedo-Cross style element was superior in keeping heavy particulates in suspension. When very light particulates {fine glitter} were tested, the Tuning Fork design was equally effective. The Torpedo-Cross stir element, being a two piece design, is more expensive than the single piece Tuning Fork stir element, but offers a greater performance when stirring heavy particulates.

 In summation, both the Torpedo-Cross and the Tuning Fork style stir elements provide a safe and effective way of keeping cells or particulates in a uniform suspension throughout a 50ml conical tube, all the while allowing you to take samples while the tube is being stirred. The Torpedo-Cross is superior when using heavy particulates or clumping cells.