Warning about EDC

16, March, 2020

Dear SPR friends,

this warning concerns you, if you use EDC-NHS activation chemistry for immobilization of your ligands onto sensors and if you source the EDC directly from Sigma Aldrich (Merck). In this text, we include EDC handling recommendations and a simple test how to show that the EDC is not working.

 In the last year, our customers in USA as well as in Europe, our suppliers and ourselves, have encountered a problem with EDC (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide) from Sigma Aldrich (“BioXtra” grade, product No. E-1769). In a number of cases, the EDC activation does not succeed. The likely cause is the presence of amine-based by-products (e.g. 3-aminopropyldimethylamine in case of EDC degradation). Such by-products are likely present when EDC is exposed to higher temperatures or higher moisture content. During a year, we have tried to resolve this issue with Sigma Aldrich (several batches shipped and tested) without success. Until today, the supplier has not shipped the product in required conditions (desiccated on ice) and consequently, many hours of work and sensor surfaces were wasted. Therefore, to save your time and sensors budget, we recommend to consider other successfully proven suppliers of EDC such as Xantec, Thermo Fisher Scientific (No. 22980) or TCI (No. D1601).

HANDLING RECOMMENDATIONS:

  • We recommend to order smaller amounts of EDC, have them shipped desiccated, store aliquoted and use within 6 months.
  • Once you receive EDC, avoid moisture from entering the vial, let the EDC to attain room temperature for at least 1 hour before opening the vial and before the intended usage.
  • Aliquot EDC into Eppendorf tubes (e.g. 40 mg portions for 1 mL of solution) before storage in the freezer, which will prevent repeated thawing.
  • Prepare the EDC/NHS solution within 15 minutes prior to the use by adding the 0.05 M NHS solution to 40 mg EDC.

IS MY EDC OK?

How can you tell from a sensograms that the EDC has likely degraded?

A simple protein binding study was selected – here HSA, human serum albumin - to show the difference. All of the instrumentation, carboxymethyldextran (CMD) sensors, buffers and samples are the same with the exception of EDC.

In this experiment, we used following EDC:

-          Sigma E1769 (bioXtra), Lot # BCCB8365, 1 g

-          Xantec, Lot #T1268242, 1 g

-          Pierce (Thermo Scientific) PG82079, Lot # UI282418, 1 g

-          TCI D1601, Lot # QBHSL-RO, 5 g

They were all new bottles that were kept at -20°C.

The test for Sigma and Xantec was done on one CMD-3D sensor, and gave following sensograms:

EDC warning

Note: EDC in the graph stands for 0.05 M NHS + 0.2 M EDC in water.

The blue signal (EDC from Xantec) shows correct activation level after EDC and consequently correct protein immobilization level. The green signal (EDC from Sigma) shows that the surface has been compromised by the EDC by-products and does not provide sufficient activation for protein binding.

 

The test for EDC by Thermo and TCI were done on another CMD-3D sensor and gave the following results:

EDC warning

Note: EDC in the graph stands for 0.05 M NHS + 0.2 M EDC in water.

Both, the blue and the green signals (EDC from TCI and Thermo) show good performance.

 

The team of BioNavis

For further information contact support@bionavis.com and put EDC in subject line. Thank you!