About Us

Nebulabio is a premier biotechnology CRO (Contract Research Organization) specializing in advanced in vitro selection technologies. With over a decade of experience and a dedicated team of molecular biologists and protein engineers, we provide end-to-end antibody discovery solutions. Our core expertise lies in designing and executing high-success-rate screening campaigns using state-of-the-art phage display platforms, having successfully delivered high-affinity leads against a wide range of targets, from soluble proteins to complex membrane receptors.

☞Principle of Phage Display Screening

The power of phage display is harnessed through a process called Biopanning, an in vitro evolution technique that enriches specific, high-affinity binders from a library of billions.

The core principle is the physical link between phenotype (the displayed antibody fragment on the phage surface) and genotype (the DNA encoding it inside the phage particle). A diverse phage library—displaying Fab, scFv, or VHH variants—is incubated with an immobilized target antigen. Phages displaying binders attach, while others are washed away. The bound phages are eluted, used to infect E. coli for amplification, and the process is repeated over 3-5 rounds. Each round exponentially enriches the population for the strongest binders, allowing for the rapid identification of lead molecules from immense genetic diversity without animal immunization.

☞Our Screening Services & Process

We offer tailored screening solutions for custom-built or our proprietary pre-made libraries across all major antibody formats.

 Service Portfolio: 

■ Custom Library Screening: We screen libraries you provide (Fab, scFv, VHH) using optimized protocols.

■ Pre-made Library Screening: Access our vast, high-diversity naïve human Fab/scFv or immunized VHH libraries for a faster start.

■ Format-Specific Optimization: Our screening conditions are finely tuned for the unique characteristics of Fab (bivalent potential), scFv (monovalent, stability), and VHH (high stability, deep pocket access) formats.

■ Specialized Panning Strategies:

• Solid-Phase Panning: Against antigens coated on plates or beads.

• Solution-Phase Panning: Using biotinylated antigens for more native conformation screening.

• Cell-Surface Panning: For identifying binders to membrane proteins in their native cellular context.

• Depletion/Subtractive Panning: To increase specificity by removing cross-reactive binders.

☞Our Proven Screening Workflow:

We follow a rigorous, multi-stage process to ensure the highest probability of success.

■ Phase 1: Project Design & Antigen Preparation

We collaborate with you to define screening stringency, select the library, and prepare the antigen in the optimal format (purified protein, biotinylated, or on cells).

■ Phase 2: Iterative Biopanning Rounds

The library undergoes 3-5 rounds of the selection cycle: Binding → Washing → Elution → Amplification. Stringency is increased each round to drive affinity maturation.

■ Phase 3: Hit Identification & Characterization

Individual clones from the final output are screened via monoclonal phage ELISA. Positive clones are sequenced, grouped into families, and their variable regions are subcloned for soluble expression.

■ Phase 4: Lead Analysis & Delivery

Soluble antibodies are produced for preliminary validation via ELISA, BLI/SPR (for affinity measurement), and specificity testing. A final report with all data and prioritized lead sequences is delivered.

Figure 1.Schema of antibody (scFv) phage display selection, screening and reformating/production of other antibody formats. 

☞Classification of Phage Display Systems

Different bacteriophage vectors offer distinct advantages for library construction and screening. The choice of system can impact display valency, protein size, and screening outcomes. The major systems are classified as follows:

 1. Filamentous Phage Systems (M13, fd, f1 - Non-Lytic): 

• Principle: The antibody gene is fused to a coat protein gene (pIII or pVIII) on the phage genome.

• Advantages: Well-established, excellent for multi-round panning, high phage yields.

• Display: Typically monovalent on pIII (higher affinity selection) or multivalent on pVIII (avidity effects).

 2. Lytic Phage Systems (T7, T4 - Lytic): 

• Principle: The antibody is fused to a capsid protein gene. Phage replication causes host cell lysis.

• Advantages: Can display larger proteins, faster cycle time, more stable virions tolerate harsh conditions.

• Display: High copy number (multivalent) on the capsid surface.

 3. Phagemid Systems (Most Common for Antibodies): 

• Principle: Combines a plasmid (phagemid) carrying the antibody gene and a helper phage. The phagemid provides the antibody gene, while the helper phage supplies other viral proteins.

• Advantages: Higher transformation efficiency (larger library sizes), easier DNA manipulation, controlled valency (typically monovalent display).

• Our Expertise: We primarily utilize advanced phagemid systems for their superior library diversity and are proficient in M13 and T7-based systems for specific applications.

Figure 2. (a) Overall architecture and coat proteins of filamentous M13 bacteriophage. The coat protein PIII is the most utilized protein for antibody display. The structures of (b) T7 phage (c) Lambda phage (d) T4 phage. Colour red indicates protein and antibody displaying proteins in all four bacteriophages. 

☞Applications of Phage Display Screening

Nebulabio screening service is the critical engine for numerous biotechnology and therapeutic applications:

• Therapeutic Antibody Discovery: Rapidly screen for leads against novel oncology, immunology, and infectious disease targets.

• Diagnostic Antibody Development: Identify highly specific, matched antibody pairs for ELISA, lateral flow, and biosensor applications.

• Cell & Gene Therapy: Discover scFv binders for CAR-T cell targeting domains against tumor-specific antigens.

• Antibody Affinity Maturation: Screen mutagenesis libraries derived from a parent antibody to significantly enhance its binding affinity.

• Protein Interaction Mapping: Identify antibodies that bind specific functional domains or epitopes to study protein function.

• VHH/Nanobody Isolation: Especially effective for screening camelid immune libraries to obtain stable, single-domain binders for therapeutic or imaging use.

Partner with Nebulabio to transform your target into high-quality antibody leads. Our systematic, data-driven screening approach maximizes your success in identifying functional, developable candidates.