Biointron is pleased to announce the publication of our AbDrop platform in mAbs. The paper describes an integrated workflow that combines droplet microfluidics, repertoire-level sequencing, and rapid full-length IgG expression in CHO cells. The platform achieves screening throughput of more than one million plasma cells per run and enables functional testing of expressed antibodies in under three weeks.
In a proof-of-concept study targeting PD-1, Lu et al. (2025) demonstrate that AbDrop can recover a broad panel of antigen-specific antibodies with diverse binding and functional profiles, including both blocking and agonistic activities. Several candidates exhibited affinities comparable to or exceeding those of established clinical antibodies.
Context and Limitations of Current Methods
Hybridoma and phage display technologies have been foundational to monoclonal antibody discovery but remain limited by throughput, labor requirements, and constraints on heavy- and light-chain pairing. Hybridoma workflows often require extended timelines and may bias toward immunodominant clones. Phage display libraries enable high-throughput in vitro selection but disrupt native chain pairing and typically rely on preliminary scFv or Fab formats before reformatting into IgG for functional evaluation.
AbDrop was developed to address these limitations by focusing on plasma cells, which naturally produce affinity-matured, class-switched antibodies and maintain native heavy/light chain pairing.
Overview of the AbDrop Workflow
Plasma cells from immunized animals are enriched and encapsulated into microfluidic droplets containing fluorescent antigen and anti-IgG detection reagents. Fluorescence-activated droplet sorting (FADS) is used to isolate antigen-reactive cells using a Förster resonance energy transfer (FRET)-based readout.
Each run processes approximately 1-2 million plasma cells and yields hundreds to thousands of unique paired heavy–light chain sequences. These sequences are recovered using single-cell BCR sequencing (MOBIDROP kits), which apply barcoded beads and nested PCR to capture full variable regions. Sequence diversity is assessed across CDRs, and phylogenetic analysis guides clone selection for expression.
Selected antibodies are produced directly as full-length IgGs using Biointron’s transient CHO expression system. Purified antibodies are evaluated for binding, purity, aggregation, and endotoxin levels.
The end-to-end workflow requires less than three weeks from plasma cell isolation to availability of functional antibodies.
Case Study: Antibodies Targeting PD-1
To demonstrate platform performance, AbDrop was applied to a PD-1 immunization model in mice. Screening of approximately one million plasma cells generated over 6,900 antigen-positive droplets. Sequencing identified 2,899 paired chains clustered into 461 unique antibodies.
Fifty-two antibodies were expressed and assessed in detail. All bound recombinant PD-1, and 51 showed ELISA activity. Several candidates displayed sub-nanomolar EC50 values.
Affinity and Functional Assessment
Using surface plasmon resonance (Carterra LSA), the 52 expressed antibodies exhibited a wide range of affinities:
- 24 antibodies: 0.1-1 nM
- 22 antibodies: 1-9 nM
- 6 antibodies: 10-70 nM
Compared with pembrolizumab (8 nM) and peresolimab (0.37 nM), 45 antibodies showed equal or stronger binding. Nine exceeded peresolimab in kinetic measurements. Flow cytometry confirmed that 38 antibodies recognized PD-1 on mammalian cells.
Epitope and Functional Profiling
Epitope binning using array-based SPR grouped the antibodies into five clusters, including pembrolizumab-like, nivolumab-like, peresolimab-like, and two clusters representing distinct epitopes.
Functional assays showed:
- Blocking activity: 17 antibodies from Clusters I–II inhibited PD-1/PD-L1 signaling; seven matched or exceeded pembrolizumab potency in reporter assays. Two antibodies (N-18-PD and N-23-PD) produced tumor growth inhibition comparable to pembrolizumab in hPD-1 knock-in mice.
- Agonist activity: Ten antibodies from Cluster III reduced T-cell proliferation in a dendritic cell–T cell co-culture assay in a dose-dependent manner.
Implications for Antibody Discovery
AbDrop integrates microfluidics, sequencing, and full-length IgG expression to provide a high-throughput, plasma cell-focused discovery workflow. Its ability to preserve native chain pairing, operate at million-cell scales, and deliver purified IgGs within weeks may support a range of research applications, including early discovery campaigns and targeted screening programs.
Publication Details
Title: AbDrop-a scalable microfluidics-enabled platform for rapid discovery and functional analysis of plasma cell-derived antibodies
Journal: mAbs (Taylor & Francis)
DOI: 10.1080/19420862.2025.2597610
Authors: Meng Yu, Liang Wang, Yan Yang, Su Liang, Yiyang Ge, Huanlei Xi, Shipin Lin, Ying Chen, Wei Liu, Weihua Wang, Changchun Zha, Haisong Lu
Affiliation: Biointron Biological Inc., Shanghai, China
Publication Date: December 4, 2025
Interested in running your own antibody discovery campaign with AbDrop? Contact us at info@biointron.com to explore how Biointron can support you.