• Easy to use
• No specialized equipment needed
• Compatible with nearly any liquid sample
• Proven technology (many publications)
• Highly sensitive (pg/mL)
• Sandwich ELISA specificity
• Higher density than ELISA, Western blot or bead-based multiplex

The C-Series arrays feature chemiluminescent signal detection. The antibodies are spotted on nitrocellulose membrane solid supports and are handled in a very similar manner to Western blots.
All C-Series arrays work on the sandwich ELISA principle, utilizing a matched pair of antibodies: an immobilized capture antibody and a corresponding biotinylated detection antibody.

1. Block membranes
2. Incubate with Sample
3. Incubate with Biotinylated Detection Antibody Cocktail
4. Incubate with HRP-Conjugated Streptavidin
5. Incubate with Detection Buffers
6. Image with chemiluminescent imaging system
7. Perform densitometry and analysis

Use serum-free conditioned media if possible. If serum-containing conditioned media is required, it is highly recommended that complete medium be used as a control since many types of sera contains cytokines. We recommend the following parameters for your samples: 50 to 100 μl of original or diluted serum, plasma, cell culture media, or other body fluid, or 50-500 μg/ml of protein for cell and tissue lysates. If you experience high background or if the fluorescent signal intensities exceed the detection range, further dilution of your sample is recommended.

1. Place each membrane into the provided eight-well tray (- means the antibody printed side). 2. Add 2 ml 1X Blocking Buffer and incubate at room temperature for 30 min to block membranes. Note: incubation may be done at 4 °C for overnight. 3. Incubate membranes with 1ml of sample at room temperature for 1 to 2 hours. Dilute sample using 1X Blocking Buffer if necessary. Note: We recommend using 1 ml of Conditioned media or 1 ml of original or 10-fold diluted sera or plasma or 50-500 μg of protein for cell lysates and tissue lysates. Dilute the lysate at least 10 folds with 1 X blocking buffer. Note: The amount of sample used depends on the abundance of cytokines. More of the sample can be used if the signals are too weak. If the signals are too strong, the sample can be diluted further. Note: Incubation may be done at 4 °C for overnight. 4. Decant the samples from each container, and wash 3 times with 2 ml of 1X Wash Buffer I at room temperature with shaking. Please allow 5 min per wash. Dilute 20X Wash Buffer I with H 2 O. 5. Wash 2 times with 2 ml of 1X Wash Buffer II at room temperature with shaking. Allow 5 min per wash. Dilute 20X Wash Buffer II with H 2 O. 6. Prepare working solution for primary antibody. Add 100μl of 1X blocking buffer to the Biotin-Conjugated Anti- Cytokines tube. Mix gently and transfer all mixture to a tube containing 2 ml of 1X blocking buffer. Note: the diluted biotin-conjugated antibodies can be stored at 4 °C for 2-3 days. 7. Add 1 ml of diluted biotin-conjugated antibodies to each membrane. Incubate at room temperature for 1-2 hours. Note: incubation may be done at 4 °C for overnight. 8. Wash as directed in steps 4 and 5. 9. Add 2 ml of 1,000 fold diluted HRP-conjugated streptavidin (e.g. add 2 μl of HRP-conjugated streptavidin to 1998 μl 1X Blocking Buffer) to each membrane. Note: Mix the tube containing 1,000X HRP-Conjugated Streptavidin well before use since precipitation may form during storage. 10. Incubate at room temperature for 2 hours. Note: incubation may be done at 4 °C for overnight. 11. Wash as directed in steps 4 and 5.
   Do not let the membrane dry out during detection. The detection process must be completed within 40 minutes without stopping. 1. Proceed with the detection reaction. Add 250μl of 1X Detection Buffer C and 250μl of 1X Detection Buffer D for one membrane, mix both solutions. Drain off excess wash buffer by holding the membrane vertically with forceps. Place membrane protein side up ( - mark is on the protein side top left corner) on a clean plastic sheet (provided in the kit). Pipette the mixed Detection Buffer onto the membrane and incubate at room temperature for 2 minutes. Ensure that the detection mixture is completely and evenly covering the membrane without any air bubbles. 2. Drain off any excess detection reagent by holding the membrane vertically with forceps and touching the edge against a tissue. Gently place the membrane, protein side up, on a piece of plastic sheet ( - mark is on the protein side top left corner). Cover with another piece of plastic sheet on the array. Gently smooth out any air bubbles. Avoid using pressure on the membrane. 3. Expose the array to x-ray film (we recommend to use Kodak x-omat AR film) and detect signal using film developer. Or the signal can be detected directly from the membrane using a chemiluminescence imaging system. Expose the membranes for 40 seconds and then re-expose the film according to the intensity of signals. If the signals are too strong (background too high), reduce exposure time (e.g. 5-30 seconds). If the signals are too weak, increase exposure time (e.g. 5-20 min or overnight). Or re-incubate membranes overnight with 1x HRP-conjugated streptavidin, and redo detection in the second day. 4. Save membranes in -20° C to -80° C for future reference.

Visual comparison of array images may be sufficient to see differences in relative protein expression. However, most researchers will want to perform numerical comparisons of the signal intensities (or more precisely, signal densities), using 2-D densitometry. Gel/Blot documentation systems and other chemiluminescent or phosphorescent detection systems are usually sold as a package with compatible densitometry software. Any densitometry software should be sufficient to obtain spot signal densities from your scanned images. One such software program, ImageJ, is available for free from the NIH website along with an array plug-in.