1. Plasma samples
Plasma is the clear, straw-colored liquid portion of blood containing red blood cells, white blood cells, platelets and proteins for blood clotting. To collect plasma, blood is collected with anticoagulant like EDTA or heparin. Within 30 minutes of blood collection centrifuged samples for 15 minutes at 1,000×g at 2-8?. Carefully transfer the supernatant to other vial. Assay could be performed immediately or plasma could be stored at -20oC for long storage. Blood collection tubes should be non-pyrogenic, and non-endotoxin.
Note: Hemolyzed blood samples should be avoid for ELISA assays.
2. Serum Samples
Serum is an amber-coloured, protein-rich liquid which separates out when blood is allowed to coagulate. To obtain serum, fresh blood is collected and allowed to clot for 2 hrs at room temperature (RT) or overnight at 4 ?. The clotted blood is centrifuged at 1,000×g for 15 minutes. Assay could be performed immediately or serum could be stored at -20oC for long storage. Blood collection tubes should be non-pyrogenic, and non-endotoxin.
3. Cell culture supernatant
The supernatant is the liquid media or culture fluid in which cells are cultured for growth. The supernatant is centrifuged at 1,000×g at 2-8°C for 20-25 minutes to remove insoluble impurity and cell debris.
4. Tissue homogenates
Tissue homogenate is cell suspension of cell fragments and cell constituents obtained when tissue is homogenized. To start with tissues are mince into small pieces and rinse with ice-cold PBS to remove excess blood. Tissue pieces are weighed and homogenized in PBS with a glass homogenizer on ice or subject to sonicator with an ultrasonic cell disrupter. The homogenates is centrifuge at 5000×g for 5 minutes to gain the supernatant.
5. Cell homogenates
Cell homgenate is a suspension of cell fragments and cell constituents obtained during process of tissue homogenization. The cell cultured plate or cell suspension is wash with with PBS (pH=7.2 ~ 7.4). Lyses of the cell is made by frequent freeze-thaw cycles or adding lysate. The samples are centrifuged at 1,000×g at 2-8? for 15 minutes to collect the supernatant.
6. Saliva / Urine / Cerebrospinal fluid / Broncho alveolar lavage fluid / Synovial fluid
The samples are centrifuged at 1,000×g for 15 minutes at 2-8? to collect the supernatant.
7. Stool / Feces
The sample is suspended with 0.01M PBS (pH=7.2~7.4) and allowed to oscillate on the ice for 15min. The sample is centrifuge at 4? for 5min to collect supernatant.
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