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In Vitro Serum Stability Measurement

Creative Biolabs is an indubitable leader of antibody development and manufacture. With professional scientists and years of rich experience, we offer a variety of high quality in vitro serum stability measurement services for bispecific antibodies (BsAbs) and other therapeutic molecules to meet customers’ requirements.

For almost all medical applications, one common requirement is the satisfying stability of the functional molecule. The functional molecule needs to be stable during production, storage, transportation, and in vivo delivery to the target site. In the case of therapeutic or diagnostic BsAbs employed in human patients, they need to remain intact and active for hours or days at 37 °C in human plasma in order to localize and enrich at the specific target site such as a tumor tissue. The therapeutic BsAbs should not precipitate, degrade, or undergo inactivation. Besides, rapid degradation of novel therapeutic BsAbs in plasma generally leads to poor in vivo efficacy of the molecule and even toxicity. Therefore, it is very important to measure the in vitro serum stability of BsAbs.

Creative Biolabs provides in vitro serum stability tests to gather preclinical stability information of the samples. The principle is to determine the concentration of active BsAb molecules after being incubated with human serum at 37 °C for a certain time. Half-life is calculated as the final data to evaluate the in vitro stability of your BsAbs. Commonly used methods for stability test, such as Enzyme-linked Immunosorbent Assay (ELISA) and Flow-cytometry, are available in Creative Biolabs.

Enzyme-linked Immunosorbent Assay (ELISA)

ELISA for determining BsAb concentration.

ELISA is a solid-phase enzyme immunoassay technique that uses antibodies and color change to identify and quantify substances, including antigen proteins or antibodies in a liquid sample or wet sample. Therefore, ELISA is a useful tool for determining serum antibody concentrations and antigen-antibody interactions. In an ELISA assay, an antigen of known concentration is immobilized on a surface. Non-interacting proteins are added to the surface to block nonspecific adsorption of other proteins to the plate. A sample of diluted serum is applied after that. If antibodies in the serum are still intact and functional, they should bind to the antigens. The surface is then washed. Secondary antibodies, which bind to other antibodies and are chemically linked in advance to an enzyme, are then applied to the surface. Another wash is performed to get rid of unbound secondary antibodies. Next, the enzyme substrate is applied and a change in color or fluorescence caused by the enzyme catalysis occurs. In order to quantify the result, a spectrophotometer, spectrofluorometer, or other optical/electrochemical devices can be used.

Flow-cytometry Assay

Flow cytometry is a common used technique for analyzing the expression of cell surface and intracellular molecules, determining different cell types in a heterogeneous cell population, measuring the purity of isolated subpopulations and analyzing cell size and volume. It enables simultaneous multi-parameter analysis of single cells. It is primarily applied to determine fluorescence intensity produced by fluorescence-labeled antibodies or ligands that combine with specific cell-associated molecules.

 The schematic diagram of flow-cytometry assay.

Figure 2. The schematic diagram of flow-cytometry assay.

Creative Biolabs provides accurate in vitro serum stability tests to gather preclinical stability information of the samples. These tests can make great contributions to the application of the therapeutic BsAbs in medication. Creative Biolabs also provides various other services regarding BsAbs development. Please feel free to contact us for more information and a detailed quote.


1. Butler, J. E. Enzyme-linked immunosorbent assay. Journal of immunoassay. 2000, 21(2-3): 165-209.
2. Edwards, B. S.; et al. Flow cytometry for high-throughput, high-content screening. Current opinion in chemical biology. 2004, 8(4): 392-398.

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