===== Scaffold (Biological Definition) =====

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

==== Example: CD63 as Scaffold ====
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