SpinTip: A Simple, Robust, and Versatile Preanalytical Method for Microscale Suspension Cell Proteomics

Sample loss and contamination
are critical preanalytical pitfalls
in microscale proteomic applications of nonadhering cells. Common
assays and workflows are not easily adoptable to microscale sample
sizes of suspension cells due to inadvertent sample loss. This impedes
preanalytical experimental manipulation of limited suspension cell
samples for microscale proteomics applications, such as encountered
for primary human materials. Here, we describe and test a simple manual
batch technique for single-step 100-fold concentration of scarce numbers
of diluted suspension cells (down to 5000 cells) by volume reduction,
facilitating microscale experiments with suspension cells. Pipette
tips with heat-sealed orifices (SpinTips) are manufactured within
1 min and serve as versatile microcentrifugation vessels from which
supernatant can be aspirated with minimal cell loss. A residual volume
of approximately 3 μL can be achieved without visualization
of the cell pellet. The results show that SpinTips enable the concentration,
medium exchange, washing, and culture of highly limited amounts of
suspension cells for functional manipulation and microscale proteomics
and are readily incorporated into standard workflows. The application
is illustrated by profiling ex vivo responses of primary acute myeloid
leukemia (AML) cells from one AML patient to daunorubicin (DNR) to
a depth of 3462 quantified proteins with excellent repeatability.