Lower Coefficients of Variations (CV) of ELISA by using an easy stabilizing method
The result of the coating and blocking process of ELISA plates shows variances from one coating process to the next one – in spite of precise and accurate handling.
Furthermore the binding capacity and the structural organisation of the capture antibodies differ from coating process to coating process. There are several and quite different reasons for these differences, such as humidity and temperature variation during coating or aspects like electrostatic charge effects of the ELISA plate, which can occur from time to time during processing. It is not possible to keep all such external factors absolutely constant in a standard laboratory, when doing the coating process on different days. Therefore the variability when measuring a complete ELISA plate is normally larger when comparing two plates coated on different days instead of comparing two plates coated on the same day in one procedure. Besides many other factors, variability of differently coated ELISA plates enhances the total coefficient of variation of an ELISA.
If one validates an ELISA e.g. for day-to-day precision (inter-assay-precision) the precision is in many cases clearly better if one does all measurements with ELISA plates coated at one day in one production lot and stored until measurement instead of working with ELISA plates coated on several days. But for using plates from one lot over several weeks or months, it is necessary to stabilize them for storage.
This can be done by using Liquid Plate Sealer®.
Plates stabilized with Liquid Plate Sealer®.can be stored normally for weeks or months in a fridge and for several years when stored dry (dry storage at 4°C with dryer and shrink-wrapped in aluminium foil).
This procedure is similar to the procedure used by manufacturers of ELISA kits.
One can store the self-coated plates in the same way as is done with commercially available ELISA kits.
The storage of plates after stabilisation will help to improve the reproducibility of an ELISA by reducing the coefficient of variations. For many validations – e.g. in the field of pharmacological and security-relevant studies – the use of stabilized plates is applicable.
The validation criteria concerning precision or reliability of the assays can be met more easily by using this method of stabilization. The positive effects of stabilization on the improvement of the coefficient of variation depend on the materials used, capture antibodies, capture antigens and the respective assay. A generally acceptable prognosis of achievable shelf life and effect on CV cannot be given and each assay has to be validated individually.
Stabilizing ELISA plates and other assay components or reagents (e.g. conjugates with HRP-Protector or LowCross-HRP or antibodies and proteins with Antibody Stabilizer) is no longer only the domain of manufacturers of ELISA kits.
It is also established for home grown ELISAs in pre-clinical or clinical studies and “state-of-the-art” research studies.