About Us

Nebulabio is a specialized biotechnology Contract Research Organization (CRO) at the forefront of single-domain antibody (sdAb) discovery and development. With a strategic focus on nanobody technology, we have built one of the industry's most comprehensive and well-characterized collections of premade single-domain antibody libraries. Our platform is designed for researchers and therapeutic developers who require rapid access to the unique advantages of VHHs/Nanobodies—exceptional stability, deep tissue penetration, and cryptic epitope targeting—without the extended timeline of custom library generation. Leveraging over a decade of expertise in camelid immunology, synthetic library design, and high-throughput phage display screening, we have successfully delivered functional leads against some of the most challenging targets in oncology, neuroscience, and infectious disease. Our mission is to provide a turnkey solution that transforms your antigen into a panel of high-affinity, developable single-domain leads in record time.

☞Introduction to Single Domain Antibody Library Screening

Single Domain Antibody Library Screening is a cutting-edge application of phage display technology focused exclusively on the discovery of VHHs (Variable Heavy-chain of Heavy-chain antibodies), also known as Nanobodies. These antibodies, derived naturally from camelids and cartilaginous fish, consist of a single, stable variable domain (~15 kDa) that retains full antigen-binding capacity.

Our screening service utilizes premade, pre-validated single-domain antibody libraries as the starting point. These libraries contain billions of unique VHH clones, each displayed on the surface of a filamentous phage particle, with its corresponding gene packaged within. The core process, biopanning, involves incubating the library with your target antigen, washing away non-binders, eluting specifically bound phage, and amplifying the enriched population through bacterial infection. This cycle is repeated 3-4 times, leading to the exponential enrichment of phages displaying high-affinity, specific VHHs.

By starting with a premade library, we eliminate the months-long process of animal immunization, lymphocyte harvesting, and primary library construction. This allows the project to begin directly with the selection phase, dramatically accelerating the path from target to lead. Our premade libraries are not just collections of clones; they are extensively quality-controlled resources with known diversity profiles and proven performance histories.

☞Advantages of Premade Single Domain Antibody Screening

Choosing our premade single-domain antibody screening service offers a compelling array of strategic and practical benefits:

• Unparalleled Speed: Bypass the 3-6 months typically required for camelid immunization program management, immune response maturation, and primary library construction. Initiate screening within days and receive lead sequences in as little as 8-10 weeks.

• Guaranteed Library Performance & Quality: Every premade library undergoes rigorous QC, including Next-Generation Sequencing (NGS) for diversity analysis and functional validation against benchmark antigens. You start with a proven, high-performing discovery tool, minimizing project risk.

• Cost Efficiency: The significant resource investment required to generate a high-diversity immune or synthetic single-domain library is shared across multiple users of our premade libraries, offering outstanding value and accessibility.

• Access to Superior and Diverse Repertoires: Our libraries are built from large panels of immunized camelids or through sophisticated synthetic design, offering diversity and quality that is often unattainable for a one-off custom project. This includes access to "immune" repertoires against common target classes (e.g., GPCRs, kinases, viral proteins).

• Expertise in sdAb-Specific Screening: Single-domain antibodies have unique biophysical properties. Our screening protocols are specifically optimized for VHHs, accounting for their stability and monovalent display, which maximizes the recovery of functional, well-folded clones.

• Ideal for Challenging Applications: Premade sdAb libraries are particularly advantageous for discovering binders to complex antigens like membrane proteins in their native conformation (via cell panning) or for epitopes requiring deep cavity access.

  
  

☞Generation of Single Domain Antibodies

Single-domain antibodies are sourced and generated through several distinct pathways, each reflected in our premade library portfolio:

• Natural Source - Camelid Immunization: The classic method. Camelids (llamas, alpacas) are immunized with the target antigen. Their unique immune system produces a significant proportion of heavy-chain-only antibodies (HCAbs). The variable domains (VHHs) from these HCAbs are then cloned to create an immune library rich in high-affinity binders.

• Naïve Repertoire Mining: VHH genes are isolated from the lymphocytes of non-immunized, healthy camelids. This creates a naïve library containing a vast, unbiased snapshot of the natural single-domain antibody repertoire, suitable for any antigen.

• Synthetic & Semi-Synthetic Design: This in silico approach involves designing VHH genes based on one or more stable framework sequences and introducing tailored diversity into the Complementarity-Determining Regions (CDRs), particularly the elongated CDR3. This method allows for the creation of fully humanized sdAb libraries or libraries with customized chemical diversity.

Our premade library collection includes best-in-class examples from all these generation strategies, allowing us to recommend the optimal source for your specific project needs. 

☞Library Construction & Screening Process

The value of our premade libraries stems from the rigorous, multi-stage process used in their creation and the optimized pipeline for their use.

 Phase A: Premade Library Construction & Validation 

1.Library Generation: Based on the strategy (immune, naïve, or synthetic), we execute the processes described in Section 4 at a large scale to maximize diversity.

2.High-Efficiency Cloning: The pooled VHH genes are cloned into a high-quality phagemid vector as fusions to the M13 phage gene III protein.

3.Transformation & Master Stock Creation: The library is electroporated into E. coli to create a primary bacterial stock with a diversity >10^10. A high-titer phage stock is subsequently rescued.

4.Comprehensive Quality Control (QC): This critical step includes:

• Titer Determination to confirm library size.

• NGS Diversity Analysis to map CDR3 length distribution, amino acid composition, and framework usage.

• Functional QC via successful panning against control antigens to verify the library's "pan-ability" and ability to yield high-affinity binders.

 Phase B: The Standardized Screening (Biopanning) Workflow 

When you engage our service, your target is processed through this optimized workflow using the selected premade library:

1.Antigen Immobilization: Your target is prepared for panning (e.g., coated on plates, biotinylated).

2.Iterative Selection (3-4 Rounds): Each round consists of Binding → Stringent Washing → Elution → Amplification.

3.Output Analysis: Polyclonal phage from each round is monitored by ELISA to track enrichment.

4.Monoclonal Screening: Hundreds of individual clones from the final round are tested for binding.

5.Sequence & Validation: Positive clones are sequenced, and unique VHHs are expressed as soluble proteins for affinity (BLI/SPR) and specificity testing.

Figure1.Design and construction of synthetic nanobody library

☞Our Premade sdAb Library Screening Service Workflow

Our client-facing service is designed for clarity, collaboration, and efficiency, providing a seamless experience from inquiry to deliverable leads.

 Step 1: Project Scoping & Library Selection 

We consult with you to understand your target and application. Based on this, we recommend the most suitable premade single-domain antibody library from our portfolio and present a detailed project plan.

Step 2: Antigen Submission & Protocol Design

You provide the purified antigen. Our scientists design a customized screening protocol, selecting the optimal panning strategy (solid-phase, solution-phase, cell-based).

Step 3: Rapid Screening Initiation & Execution

Using the pre-qualified library, we immediately commence the biopanning campaign. We provide regular updates, including enrichment data after each selection round.

Step 4: High-Throughput Hit Identification & Analysis

We perform monoclonal screening on the final output. All binding clones are sequenced, and our bioinformatics pipeline performs clustering analysis to identify all unique VHH families, providing a diversity report.

Step 5: Lead Characterization & Validation

Representative clones from key families are expressed in E. coli or yeast. Purified VHHs undergo a defined validation cascade:

• Confirmatory Binding Assay (ELISA/SPR/BLI).

• Affinity Determination using Biolayer Interferometry (Octet).

• Specificity Assessment.

Step 6: Comprehensive Delivery

You receive a final project report with all data, sequence files, expression constructs for lead VHHs, and optionally, purified protein samples. We hold a close-out meeting to review results and discuss potential next steps (e.g., affinity maturation, humanization).

 Our End-to-End Service Flowchart: 

Partner with us to leverage the power of pre-validated single-domain antibody diversity. Contact Nebulabio’s team to begin your accelerated discovery campaign and unlock the potential of nanobody technology for your most ambitious targets.