Antibody-Targeted PEG LiposomesDistal-PEG Conjugation and Orientation ControlLong-Circulating Vesicles for Targeted Delivery
PEGylated immunoliposomes combine the long circulation of PEG-shielded liposomes with the cell selectivity of an antibody or antibody fragment, producing a vesicle that stays in the blood longer and binds a chosen receptor on target cells. The antibody is attached to the distal end of the PEG chains so it extends beyond the shielding corona and remains accessible to the antigen, while the PEG layer continues to reduce recognition by the reticuloendothelial system. We develop these constructs from antibody selection and reactive-lipid design through conjugation, purification, and characterization, with payload encapsulation where the study requires it.
Projects can start from a validated antibody or fragment, a reactive liposome platform, or a target receptor with a known antibody. Where the work involves vesicle engineering, we coordinate with antibody liposome conjugation, liposome conjugation, and PEG lipid synthesis and conjugation programs.
An immunoliposome that targets well but clears fast, or circulates well but cannot reach its antigen, helps no one. Early immunoliposome designs were cleared rapidly by the liver and spleen; simple PEG coatings improved circulation but hid the antibody behind the polymer layer. The solution is a construction where the antibody sits on the PEG terminus rather than under it, and where conjugation does not cost the antibody its binding activity or the vesicle its stability.
A practical immunoliposome strategy treats antibody format, PEG length, reactive-lipid chemistry, ligand density, and orientation as connected variables. That matters because the same vesicle must evade serum proteins, reach the target tissue, bind the receptor, and in many projects be internalized with its payload intact. We design these features together and verify them after conjugation rather than assuming the antibody survived the coupling chemistry.
Schematic of a long-circulating PEG liposome with antibodies conjugated at the PEG distal termini, illustrating receptor-mediated targeting.
Antibodies anchored directly on the bilayer can be sterically hidden by the PEG layer. We attach the antibody or fragment at the distal end of PEG chains, so it extends beyond the corona and remains accessible to the antigen.
Random coupling can modify the antigen-binding site or denature the antibody. We select site-oriented chemistries such as maleimide-thiol coupling of reduced hinge fragments and control the reaction so antigen recognition is preserved.
How many antibodies sit on the vesicle and which way they face decide avidity and uptake. We tune ligand density and use orientation-aware conjugation, then verify binding and, where relevant, internalization.
Surface conjugation can shift size, zeta potential, and storage behavior, and batch-to-batch variation breaks comparative studies. We characterize size, charge, and antibody content per batch and document them for reproducible builds.
We provide custom PEGylated immunoliposomes built around the antibody format and targeting goal, with reactive-lipid design, conjugation chemistry, and characterization defined for the project.
Antibody and Fragment Selection Review
Capabilities include:
Typical applications:
Targeting constructs for receptors such as HER2, EGFR, CD19, TfR, and related cell-surface markers.
Reactive PEG Lipid and Vesicle Design
Capabilities include:
Typical applications:
Vesicles engineered with the reactive handle at the PEG terminus for antibody attachment.
Conjugation, Purification and Stabilization
Capabilities include:
Typical applications:
Functional immunoliposomes with controlled antibody loading and retained binding activity.
Characterization and Targeting Verification
Capabilities include:
Typical applications:
Release-ready immunoliposomes with a defined analytical and functional profile.
The conjugation route decides where the antibody sits, whether it remains active, and how reproducible the construct is. The comparison below ties the route to the antibody format and the targeting goal.
| Conjugation route | Antibody format | Attachment point | Typical use |
| Maleimide-thiol coupling | Reduced F(ab')2 or thiolated IgG | Hinge or engineered thiol | Site-oriented, activity-preserving targeting |
| Amide coupling to DSPE-PEG-COOH | IgG, F(ab')2, scFv | Lysine or available amine | Flexible format, moderate orientation control |
| Click chemistry (azide-DBCO) | Engineered or modified antibody | Defined handle | Orthogonal, low-background conjugation |
| Post-insertion of antibody-PEG-lipid | Pre-formed antibody-lipid conjugate | Distal PEG | Preserving encapsulated cargo and vesicle integrity |
The lipid recipe and PEG architecture set circulation, antibody access, and vesicle behavior. The ranges below are typical starting points adjusted to the specific project.
| Component | Role | Typical choice / range |
| Core lipid (DSPC, HSPC, DOPC) | Bilayer scaffold | 50-70 mol% |
| Cholesterol | Stability and packing | 30-45 mol% |
| PEG lipid (DSPE-PEG) | Stealth and antibody anchoring | 3-8 mol% (PEG2000 common) |
| Reactive PEG lipid (maleimide, COOH, azide) | Antibody attachment point | 0.5-3 mol% |
| Antibody loading | Targeting ligand | 10-40 molecules per vesicle typical |
| Payload (optional) | Encapsulated cargo | Drug, siRNA, mRNA, or label per project |
For immunoliposomes, release data must cover the vesicle, the antibody, and the targeting function together. The checks below are typical of the qualification package.
| Check | Method | What It Confirms |
| Vesicle size and PDI | Dynamic light scattering | Stable size distribution after coupling |
| Surface charge | Zeta potential | Expected surface state maintained |
| Antibody content | Protein assay or labeled-antibody quantification | Ligand loading per vesicle |
| Binding function | Target-binding or cell-binding assay | Antibody remains active on the vesicle |
| Uptake (optional) | Flow or microscopy with labeled vesicles | Receptor-mediated internalization |
| Stability | Storage study | Size, binding, and payload retained over time |
We clarify the receptor, its expression and internalization behavior, and the antibody or fragment you plan to use. This decides format, chemistry, and density before formulation.
Lipid composition, PEG length, and reactive-lipid handle are selected so the antibody attaches at the PEG distal end and the vesicle circulates well.
The antibody is coupled by the chosen route, then purified away from unconjugated antibody and reaction byproducts while vesicle integrity is preserved.
Buffer, blocking, and storage conditions are set so the immunoliposome remains dispersible and stable for the intended use.
Size, zeta, antibody content, and binding are measured; uptake is verified where the project needs it.
Final output includes the PEGylated immunoliposomes, handling guidance, and an analytical summary supporting targeted delivery research.
We attach the antibody at the distal end of the PEG chains so it extends beyond the shielding corona. This is the design difference between an immunoliposome that binds its antigen and one that circulates well but cannot reach it.
Site-oriented chemistries such as maleimide-thiol coupling are used to keep the antigen-binding region intact, and binding is verified on the finished vesicle rather than assumed.
Ligand density and facing are controlled for avidity and uptake, so the vesicle binds and, where required, is internalized with its payload.
Size, charge, antibody content, binding, and stability are reported together, giving a picture of the immunoliposome that supports comparative and downstream studies.
Whether you need a receptor-targeted immunoliposome for cancer research, a brain-targeting vesicle for CNS delivery, or a stealth liposome with a defined antibody for imaging, we provide support from antibody and vesicle design through conjugation, purification, and targeting verification.
Our team works with customer-defined antibodies, lipid systems, and payloads to deliver PEGylated immunoliposomes and data packages that are easier to evaluate and integrate into downstream research. Contact our scientific team to discuss your PEGylated immunoliposome requirements and request a project-specific proposal.
It is a liposome with a PEG coating that prolongs circulation and an antibody or antibody fragment attached, usually at the distal end of the PEG chains, that binds a target receptor. The combination gives a long-circulating vesicle with cell-selective targeting.
If the antibody sits directly on the bilayer, the PEG corona can hide it from the antigen. Attaching it at the PEG distal terminus lets it extend beyond the shielding layer, so the immunoliposome keeps its stealth properties and still binds the target.
Full IgG, F(ab')2, Fab', and scFv fragments can all be conjugated. Smaller formats are often preferred when reduced steric burden, better surface access, or a more compact vesicle is needed.
We use site-oriented chemistries such as maleimide-thiol coupling of reduced fragments, and we control density and reaction conditions to protect the antigen-binding region. Binding is verified on the finished vesicle.
Ligand density is tuned to the project, with tens of antibody molecules per vesicle as a common working range. The value is measured and reported so avidity and uptake behavior can be interpreted.
Delivered material is for research use only. Immunoliposome technology has clinical precedents in targeted liposomal drug development, but our services supply research-grade constructs and are not for clinical or therapeutic application.
