Single-chain variable fragment (scFv) consists of the variable regions of an IgG light chain (VL) and heavy chain (VH), connected by a flexible peptide linker, with a size of approximately 25 kDa. scFvs have a simple structure, retain the specificity and affinity for their antigen, and do not require constant antibody regions. scFvs are primarily constructed from hybridoma cells, mouse spleen, and human B lymphocytes. Due to their small size, scFvs exhibit good tissue penetration, high in vivo clearance rates, and low immunogenicity, making them widely used in disease diagnosis and treatment. Furthermore, scFvs can be expressed in various systems, including mammalian cells, yeast cells, plant cells, and insect cells. Among these, the E. coli expression system is convenient to operate, has a short preparation cycle, and simple culture conditions, enabling large-scale scFv antibody production.

KMD Bioscience possesses extensive experience in recombinant antibody expression and can perform scFv expression using different protein expression systems based on client requirements. The mammalian expression system facilitates proper protein folding and post-translational modifications, making it the primary choice for expressing human or other mammalian proteins. However, the mammalian system suffers from low protein yield, requiring significant amplification, which increases experimental costs and timelines. Leveraging years of experience in developing mammalian expression systems, KMD provides clients with high-quality scFv Eukaryotic Expression Services. We hold the advantage of preparing large quantities of protein within a short turnaround time, delivering ideal proteins for clients' functional, structural, and therapeutic studies. We offer not only mammalian expression systems like CHO and HEK 293 cells but also prokaryotic expression services using E. coli. Additionally, we have developed efficient soluble protein expression technology that avoids inclusion body formation, ensuring protein activity. This technology is suitable for large-scale scFv antibody production. KMD Bioscience has successfully delivered large quantities of recombinant proteins to numerous domestic and international institutions using the E. coli expression system.

KMD Bioscience also maintains a comprehensive Baculovirus/Insect Cell Protein Expression System for producing and expressing viral recombinant proteins from baculovirus-infected insect cells. This system enhances protein solubility and enables post-translational modifications. Simultaneously, the Baculovirus/Insect cell system allows co-expression of multiple genes, forming heterodimers or multimers, and generates high yields of both intracellular and secreted proteins. Our protein expression and purification platform supports both small-scale and large-scale production to meet diverse client needs. KMD utilizes the baculovirus expression system to support production of difficult-to-express proteins, such as kinases, viral targets, cell surface receptors, transporters, various enzymes, and membrane proteins. We provide comprehensive services meeting client requirements, with high quality maintained throughout the entire process of scFv codon optimization & gene synthesis, scFv expression small-scale testing & scale-up, and scFv purification & characterization.