Variation in protein activity, even when the proteins are from the same batch, can be a nuisance. It is a good idea to check the quality of proteins if they have been stored for a while or if the source of proteins has changed before doing further experimentation with them. The quality control of biopharmaceuticals such as antibodies is also done in manufacturing settings because the quality of antibodies is affected by process parameters such as pH, temperature, CO2, and cell culture metabolites . Not only should these biopharmaceuticals be characterized by standard physicochemical methods such as mass spectrometry, but their biological activities must be investigated as well. This has traditionally been done using endpoint assays such as Enzyme-Linked Immunosorbent Assays (ELISA)  . However, these assays do not provide kinetic and affinity data . An alternative method is Surface Plasmon Resonance (SPR). SPR is a powerful technique to characterize proteins because it is a label-free technique that enables real-time assessment of protein interactions, and it does not require much sample preparation . Large SPR systems have been used to perform protein quality control  . Still, access to large centralized SPR equipment is limited, samples must be pre-stored and transported to the facility, and consumable costs are high . Portable SPR devices, on the other hand, can give scientists quick and easy access to obtain valuable kinetic and affinity data needed to validate quality, without compromising sensitivity and specificity.
Quality control with P4SPRTM
We demonstrate how easy it is to use our portable SPR sensor (P4SPR™) to determine which source of anti-nucleocapsid antibody exhibits the best binding performance with the SARS-CoV-2 nucleocapsid recombinant protein (Figure 1). Please see our Antibody QC Appnote for more experimental details and results. Basically, four sources of anti-nucleocapsid antibody were introduced to a sensor surface which has been immobilized with the SARS-CoV-2 nucleocapsid protein (Table 1). The SPR response of each source of antibody was compared.
Figure 1 – Detection scheme of anti-nucleocapsid antibody by immobilized SARS-CoV-2 nucleocapsid protein on P4SPR™.1
Table 1. Sequence of injection and source of anti-nucleocapsid antibody.
AB1, lot A
AB1, lot B
AB2, lot A
AB1, lot C
The four sources of anti-nucleocapsid antibodies yielded different average levels of binding (Figure 2), with the second source (Injection #2) giving the highest level of response. It is also important to point out that the entire experiment took about 2 hours, which is much shorter than performing an ELISA assay.
Figure 2. Average shifts in resonance units (RU) for all four sources of anti-nucleocapsid antibody. The reference for Injection #4 is too small to be seen (-0.486 RU).
It is evident that a simple and portable SPR instrument (P4SPRTM) by Affinité instruments can quickly establish which antibody source should be used for further experimentation due to its superior performance over others. This will certainly reduce a significant amount of of lost time for researchers to disqualify less biologically active antibodies before conducting their experiments. Therefore, the P4SPR™ provides a quick and easy alternative to perform quality control on other types of biopharmaceutical products. Furthermore, it is a very user-friendly instrument that provides fast, real-time data and precision due to its multichannel feature. It is thus more advantageous than long and laborious endpoint assays such as ELISA to obtain quality control data.
Thank you for reading and watch out for additional blogs discussing SPR related topics such as SPR vs ELISA, wavelength vs. angle interrogation, planar SPR vs. nanoparticle localized SPR, multiple channel SPR, and integrating pumps with SPR.
Contact us to learn more about SPR at email@example.com
We would like to thank Abdelhadi Djaileb from Dr. Jean-François Masson’s lab from Université de Montréal for the collection of these data.
1. M. Zschatzsch, Paul Ritter, Anja Henseleit, Klaus Wiehler, Sven Malik, Thomas Bley, Thomas Walther, Elke Boschke, “Monitoring bioactive and total antibody concentrations for continuous process control by surface plasmon resonance spectroscopy,” Eng. Life Sci., vol. 19, pp. 681-690, 2019.
2. P. Thillaivinayagalingam, J. Gommeaux, M. McLoughlin, D. Collins, A. R. Newcombe, “Biopharmaceutical production: Applications of surface plasmon resonance biosensors,” J. Chromatogr. B, vol. 878, pp. 149-153, 2010.
3. C. Gassner, F. Lipsmeier, P. Metzger, H. Beck, A. Schnueriger, J.T. Regula, J. Moelleken, “Development and validation of a novel SPR-based assay principle for bispecific molecules,” J. Pharm. Biomed. Anal., vol. 102, pp. 144-149, 2015.
4. “Affinité Instruments,” [Online]. Available: http://affiniteinstruments.com/.