Nanoparticle Interaction with Immune Complement System

Nanoparticles introduced into the bloodstream encounter the immune complement system, a proteolytic cascade that bridges innate surveillance and adaptive responses. Complement activation can occur via three principal routes—the classical, lectin and alternative pathways—each culminating in deposition of C3 fragments on particle surfaces, generation of proinflammatory anaphylatoxins and formation of the membrane attack complex. Such interactions influence circulation half-life, biodistribution and clearance of nanoparticles by mononuclear phagocytes, and may provoke acute hypersensitivity or chronic inflammatory sequelae. Surface chemistry, size, charge and the formation of a biomolecular corona dictate the balance between stealth and recognition. A detailed understanding of complement engagement is central to optimising nanomedicines for cancer therapy, imaging and targeted delivery, while minimising adverse immune-related events.

Research from Nature Portfolio

Recent studies have demonstrated that reducing cholesterol content in cell-membrane-coated nanovehicles enhances evasion of complement-mediated clearance, thereby doubling tumour accumulation and improving therapeutic outcomes in preclinical cancer models. By selectively depleting cholesterol from T-cell–derived membrane coatings, engineered nanocarriers maintain functional surface receptors while attenuating complement opsonisation and blood clearance. Foundational work has elucidated how defined nanoscale chemistry and surface functionalities on carbon spheres regulate biocompatibility and complement activation. Systematic variation of particle size, surface charge and coating molecular weight revealed that highly positive charges markedly increase complement deposition, whereas neutral or negatively charged carboxyl-terminated surfaces minimise complement engagement, guiding the design of safer carbon-based nanomaterials.

Nanoparticle Interaction with Immune Complement System publication trend

The graph below shows the total number of articles in nanoparticle interaction with immune complement system across all publications each year (not limited to Nature Index journals).

Technical terms

Complement system: A cascade of plasma proteins that recognises and eliminates pathogens or foreign surfaces through proteolytic activation, opsonisation and membrane attack complex formation.

Opsonization: The process by which particles are tagged with complement fragments (e.g., C3b) to promote recognition and phagocytosis by immune cells.

Anaphylatoxins: Small complement-derived peptides (notably C3a and C5a) that induce inflammation, vascular permeability and leukocyte chemotaxis.

Classical, lectin and alternative pathways: Distinct mechanisms of complement activation triggered by antibodies or pattern recognition (classical), carbohydrate motifs (lectin) or spontaneous C3 hydrolysis and amplification loops (alternative).

Biomolecular corona: A dynamic layer of proteins and other biomolecules that adsorbs onto nanoparticle surfaces in biological fluids, modulating immune recognition and complement activation.

References

1. Cholesterol removal improves performance of a model biomimetic system to co-deliver a photothermal agent and a STING agonist for cancer immunotherapy. Nature Communications (2023).
2. Regulating Biocompatibility of Carbon Spheres via Defined Nanoscale Chemistry and a Careful Selection of Surface Functionalities. Scientific Reports (2015).
3. Immunological and Toxicological Considerations for the Design of Liposomes. Nanomaterials (2020).
4. Nanoparticle-Induced Complement Activation: Implications for Cancer Nanomedicine. Frontiers in Immunology (2021).
5. Mechanisms of complement activation by dextran-coated superparamagnetic iron oxide (SPIO) nanoworms in mouse versus human serum. Particle and Fibre Toxicology (2014).