Bio-Rad Bio-Plex Pro™ Human Cancer Biomarker Assays - Manual (Page 16)

14
Sample Preparation
Serum and Plasma
EDTA or citrate is preferred as an anticoagulant. Heparin-treated plasma,
while compatible with Bio-Plex Pro
™ assays, may absorb certain soluble
proteins of interest. Avoid using hemolyzed samples as this may lead to
false positive results.
1. Draw whole blood into collection tubes containing anticoagulant.
Invert tubes several times to mix.
2. For serum, allow blood to clot at room temperature for 30 to 45 min.
For plasma, proceed directly to the centrifugation steps.
3. Perform centrifugation at 1,000 x g for 15 min at 4°C and transfer the
serum or plasma to a clean polypropylene tube.
4. To completely remove platelets and precipitates, centrifuge again at
10,000 x g for 10 min at 4°C.
5. Dilute samples fourfold (1:4) by adding 1 volume of sample to 3
volumes of Bio-Plex ® sample diluent HB (for example, 40 µl sample +
120 µl sample diluent).
6. Assay samples immediately or aliquot into single-use tubes and store
at –70°C. Avoid repeated freeze-thaw cycles.
Cell Culture Supernatant
1. Collect supernatants and centrifuge at 1,000 x g for 15 min at 4°C.
For cell lines cultured in serum-free culture media, collect
samples and add BSA as a carrier protein to a final concentration
of at least 0.5% to stabilize protein analytes and to prevent
adsorption to labware.
2. Transfer to a clean polypropylene tube. If cellular debris or precipitates
are present, centrifuge again at 10,000 x g for 10 min at 4°C.
3. We recommend testing undiluted samples first. If levels are
anticipated to be high, samples can be further diluted in culture
medium. Rarely would samples need to be diluted greater than 1:10.
4. Assay immediately or store samples in single-use aliquots at –70°C.
Avoid repeated freeze-thaw cycles.