There are some variations in plate coating protocols, but they typically involve the following steps:
- Add coating solution (e.g. antibody or antigen)
- Overnight incubation, normally at room temperature
- Aspirate (suck-off coating solution)
- Wash 3 times with washing buffer (step not mandatory for all coatings)
- Dispense blocking solution
- Incubate, typically 1-3 hrs
- Aspirate (suck-off blocking solution). Residual volume is critical in this step!
At the most basic level, a multichannel pipette is enough to coat a single plate. However, ELISA coating is typically applied to many plates at a time and is normally a production process. Therefore, automation is highly desired.
Plate coating is a demanding process. Most demands come from the fact that it is a production process, thus involving the preparation of many plates per day. The most important demands are:
- Throughput: Can range from a few dozen plates per day for homebrew ELISA assays to hundreds or even thousands of plates per day for kith manufacturers. To achieve this throughput, a very fast microplate washer is required.
- Reliable handling of troublesome ingredients: the reagents used in plate coating can be troublesome, as they may clog the thin needles typically found in (for example, buffers containing high salt or sugar concentrations) or produce large amounts of foam (for example, detergent-containing wash buffers or protein solutions).
- Low residual volume: this is of utmost importance when removing the blocking reagent, as any residues would interfere with the actual assay and the washing steps in the plates.
- Easy setup: time is gold when processing large quantities of plates. Therefore, it is important to start your daily work as soon as possible.
- Easy maintenance: similarly, it is important to keep low the time and money to be spent in maintenance, and to avoid long downtimes in case of failure.
Thesatisfies all plate coating demands:
- High throughput thanks to its integrated stackers and single-rail design: it can coat or block up to 250 plates/hour, and wash (3x) up to 150 plates/hour.
- Clogging is prevented thanks to the large diameter of its dispense and aspirate needles and automated rinse and clean-out routines.
- Foaming is prevented thanks to the ability to optimize dispense position and speed, and the possibility to continuously add an anti-foaming reagent the liquid waste trap.
- Lowest residual volumes thanks to 3D-positioning of the aspiration needles and its powerful vacuum system with a constant and stable flow rate.
- Daily setup and shutdown normally involve only running the integrated rinse and cleaning routines; waste management is extremely simplified thanks to its self-emptying waste trap, with automated addition of sterilization reagent, if necessary.