A scaffold is a structural or molecular platform that supports the spatial organization and functional integration of biological components. In molecular biology and bioengineering, scaffolds are used to:

• Anchor proteins, tags, or ligands
• Facilitate selective cargo loading
• Enable molecular assembly or delivery

In engineered extracellular vesicles, CD63 is used as a membrane-anchored scaffold to:

• Display mCherry on the luminal side
• Present FLAG-tags externally
• Enable cargo binding via nanobody–fluorophore interaction