Nonspecific Colloidal-Type Interaction Explains Size-Dependent Specific Binding of Membrane-Targeted Nanoparticles

Area of Science:

• Biophysics
• Nanotechnology
• Biomedical Engineering

Background:

• Directed nanoparticle binding to cell receptors is crucial for applications like molecular imaging and drug delivery.
• Current understanding attributes nanoparticle-ligand binding affinity primarily to multivalent receptor-ligand interactions.
• The size-dependent nature of this binding has been observed but not fully explained.

Purpose of the Study:

• To investigate the role of non-specific nanoparticle-membrane interactions in binding kinetics.
• To challenge the sole attribution of size-dependent affinity to multivalent interactions.
• To provide a more comprehensive model for predicting nanoparticle targeting efficacy.

Main Methods:

• Utilized label-free single-particle imaging to observe nanoparticle behavior.
• Correlated the binding of targeted nanoparticles with the distribution of non-targeted particles near a cell-mimetic lipid membrane.
• Quantified the influence of weak, attractive colloidal forces on binding avidity.

Main Results:

• Demonstrated that weak, attractive colloidal interactions significantly impact nanoparticle binding kinetics.
• Showed that 50 nm gold nanoparticles exhibit an order of magnitude higher avidity than 20 nm particles due to these forces.
• Identified a k_BT-scale attraction as a key factor influencing binding.

Conclusions:

• Non-specific nanoparticle-membrane interactions are a critical determinant of binding avidity, alongside specific receptor-ligand binding.
• Existing models may underestimate the contribution of these weak forces.
• Accurate prediction of nanoparticle targeting, cellular uptake, and related processes requires considering these nonspecific interactions.