High affinity single-chain variable fragments are specific and versatile targeting motifs for extracellular vesicles

Area of Science:

• Biotechnology
• Cell Biology
• Nanomedicine

Background:

• Exosomes facilitate intercellular communication via cargo transfer (DNA, RNA, proteins).
• Genetic engineering allows exosome loading with therapeutic molecules and surface display of targeting moieties.
• Targeted exosomes offer a natural platform for therapeutic delivery.

Purpose of the Study:

• To investigate the efficacy of single chain variable fragments (scFv) as targeting domains for exosome delivery.
• To determine the optimal conditions for targeted exosome uptake by cells expressing a specific antigen (Her2 receptor).

Main Methods:

• Generation of exosomes engineered to target the Her2 receptor using anti-Her2 scFvs.
• Systematic variation of scFv affinity and Her2 expression levels on recipient cells.
• Analysis of exosome uptake, intracellular trafficking, and cargo delivery.

Main Results:

• Optimal selective exosome uptake required high-affinity anti-Her2 scFvs (K_D≤ 1 nM) and high Her2 expression (≥10⁶ copies/cell).
• Targeted exosome delivery via cell surface receptors altered intracellular trafficking pathways.
• Demonstrated potential to influence cargo delivery efficiency and intracellular fate.

Conclusions:

• Antibody fragment-displaying exosomes are effective vehicles for targeted therapeutic delivery.
• Affinity and target expression levels are critical parameters for successful targeted delivery.
• Targeted delivery influences exosome intracellular routing, impacting therapeutic outcomes.