text: There are also current approaches that are manufacturing scaffolds and coupling them with biological cues. Fabricated scaffolds can also be manufactured using either biological, synthetic, or a combination of both materials from scratch to mimic the native heart valve observed using imaging techniques. Since the scaffold is created from raw materials, there is much more flexibility in controlling the scaffold's properties and can be more tailored. Some types of fabricated scaffolds include solid 3-D porous scaffolds that have a large pore network that permits the flow through of cellular debris, allowing further tissue and vascular growth. 3-D porous scaffolds can be manufactured through 3-D printing or various polymers, ranging from polyglycolic acid (PGA) and polylactic acid (PLA) to more natural polymers such as collagen.
  Fibrous scaffolds have the potential to closely match the structure of ECM through its use of fibers, which have a high growth factor. Techniques to produce fibrous scaffolds include electrospinning, in which a liquid solution of polymers is stretched from an applied high electric voltage to produce thin fibers. Conversely to the 3-D porous scaffolds, fibrous scaffolds have a very small pore size that prevents the pervasion of cells within the scaffold.
  Hydrogel scaffolds are created by cross-linking hydrophilic polymers through various reaction such as free radical polymerization or conjugate addition reaction. Hydrogels are beneficial because they have a high water content, which allows the ease of nutrients and small materials to pass through.