The low density of ZZ on the surface of microbes makes it difficult to capture mouse and goat IgG on their surface. ZZ peptide (designated CHO-ZZ cells). These stable CHO-ZZ cells were able to capture a variety of IgG, including human, rabbit, donkey and even mouse and goat. CHO-ZZ cells could be used to quantify human IgG in the range of approximately 12.51000 ng/mL, and to identify high-yielding engineered monoclonal cell lines. == Conclusions == We have established a highly efficient CHO-ZZ display system in this study, which enables the quantification of IgG from numerous species under physiological conditions. This system offers the advantage of eliminating Azoramide the need for antibody purification and will contribute to antibody development. == Supplementary Information == The online version contains supplementary material available at 10.1186/s12896-023-00798-2. Keywords:Immunoglobulin G, ZZ peptide, Cell-based surface display, Quantification, Cell sorting == Background == As ideal therapeutic and diagnostic molecules, antibodies have become the best-selling drugs in the pharmaceutical market. In recent years, the global antibody drug market has been growing at a rate of over 10% [1]. In the mean time, major Azoramide improvements in the field of tumor immunotherapy vastly accelerated the growth of antibody drugs [2]. In antibody drugs development, it is crucial to screen and identify stable and high-yielding cell lines to produce highly active antibodies [3]. Various methods have been developed to identify and characterize the overall performance of IgG-secreting cells, including turbidimetric assay, enzyme-linked immunosorbent assay (ELISA), mass spectrometry, high-performance liquid chromatography and surface plasmon resonance [47]. The quantification of antibodies using these methods necessitates antibody screening and purification, which incurs significant time and cost expenditures. Additionally, these assays are usually performed under non-physiological conditions (hostile and variable buffer environment), which may not only impact the activity of antibody, but also fail to discriminate between functional and non-functional antibodies. In the present study, to screen and identify Azoramide monoclonal cells that secrete highly potent IgG, we intended to develop a novel method for IgG quantification by displaying the ZZ domain name on mammalian cell surface. The Z domain name is a synthetic artificial analogue of the B domain name of staphylococcal protein A [8], and ZZ are two tandem Z domains [9]. The Z peptide binds with high affinity (Kd = 10 nM) to the constant region (Fc) of the human IgG heavy chain and does not interfere with the antibody-antigen conversation [10]. Therefore, ZZ has been successfully applied in protein production, immunofluorescence staining and immunodetection etc [1113]. Compared to protein A or protein G, ZZ is usually less time-consuming and more cost-effective. ZZ-modified beads provide a quick method for IgG purification from serum or culture supernatants [11,14]. Furthermore, immobilization of purified ZZ proteins around the microtiter plate or beads is an excellent immunosorbent for ELISA [11,15,16]. Expression and display of the Z/ZZ peptide on the surface of E. coli and yeast can eliminate the hassle of Z/ZZ purification and make the assay less difficult [17,18]. However, the cell wall of these microbes is a rigid structure that constitutes a physical barrier to large molecules transit and limits the release and display of proteins [19], which may result in lower display efficiency of ZZ comparing to mammalian cells. Numerous of genetic elements related to ZZ display have been used to improve the display efficiency of ZZ [20]. Due to cell wall barriers and limited surface area, efficient display of Z/ZZ on microbial surfaces remains a challenge. CASP3 In addition, the risk of microbial contamination weakens the application of yeast display of ZZ in the cell laboratories and biofactories. The objective of this study was to establish a ZZ display system on the surface of mammalian cells for the quantification of highly active IgG under physiological conditions, without requiring antibody purification. We constructed a eukaryotic ZZ-displaying plasmid and transfected it into CHO cells. After circulation cytometric sorting, we obtained the stable cells.