Cell-Based Screening Introduction

Phage display technology is an efficient gene expression screening technology in which exogenous proteins or polypeptides are fused with specific phage coat proteins, displayed on the surface of phages, and maintain relatively independent spatial conformation and biological activity, which is conducive to the specific recognition and binding of target molecules, thus realizing the unity of the genotype and the expression type. It is an important research tool in biological research. Phage display technology fundamentally changes the traditional monoclonal antibody preparation process and greatly reduces the process of antibody preparation. This method is widely used in the establishment of antigen-antibody libraries, drug design, vaccine research, pathogen detection, gene therapy, antigen epitope research, and cell signal transduction research. Based on our rich field experience and advanced research platform, Creative Biolabs provides comprehensive services to support cell-based library screening.

Fig 1. Antibodies and immunoglobulins

Phage Display Library Screening

The successful application of antibody library technology cannot be separated from antibody library screening technology. Generally speaking, the screening of phage antibody libraries consists of two main parts, which are antibody biopanning and antibody identification. Antibody biopanning is the enrichment of strains carrying antibody genes specifically bound to antigens from the antibody library after several rounds of adsorption, elution, and amplification. Antibody identification refers to the selection of monoclones from the strains obtained in the previous step for the characterization of specificity and affinity, with a view to obtaining highly specific monoclones.

Screening of antibody libraries refers to the screening of antibodies specific to an antigen from an antibody library. Good or bad screening results are crucial for obtaining high-affinity antibodies. Common methods for phage display libraries are mainly categorized into classical and novel screening methods. Classical screening methods refer to solid phase library screening and solution sorting library screening. These two methods are usually used for antibody screening where the nature of the antigen is clear. However, when the nature of the antibody is not clear or the antigen cannot be purified, the new screening method is particularly important. Cell-based library screening is one of them. In addition to cell based library screening, tissue section library screening, in vivo library screening, selective infection library screening, protease substrate screening, and protein microarray library screening are also commonly used novel screening methods.

Cell-Based Library Screening

When the expression of antigens is low and the immunogenicity is weak, the commonly used screening methods for immobilized antigens are difficult to perform. In addition, solid phase library screening of encapsulated antigens does not maintain their natural conformation, making it unsuitable for panning membrane or cell-surface antigens, whereas panning with intact cells expressing these antigens avoids the problems caused by conformational changes. In addition to intact cells, cell membrane preparations and antigenic proteins on tissue sections can maintain their natural conformation, and therefore these materials can also be used as target materials for panning cell surface antigens.

Although it has been reported in the literature that phage antibodies binding to cell surface receptors have been obtained using cell-based library screening, cell-based library screening does present some difficulties. Antibodies obtained based on cell-based library screening suffer from high nonspecificity, high background values, and loss of specific ligands during the panning process. Due to the complexity of the cell membrane surface with many proteins, sugars, and lipids, there is a high chance that non-specific phage antibodies will bind to the cell, and the low density of antigens on the surface of the membrane makes antibody screening difficult, and it is difficult to obtain a single-chain antibody against a certain antigen. Compared with solid-phase screening of purified antigens, cell-based library screening is slower to enrich, but if too many rounds of biopanning are performed, rare, specific phage antibodies are easily lost. Therefore, more in-depth studies are needed to improve the specificity and selectivity of cell-based library screening.

Creative Biolabs has a wealth of knowledge and experience in antibody phage display. We would be happy to share with you our knowledge and experience in cell-based library screening.

All listed services and products are For Research Use Only. Do Not use in any diagnostic or therapeutic applications.

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