Table 2.

The list of advantages and disadvantages in skin regeneration applications for each of the different natural-based bioinks.

Natural-Based Bioinks	Advantages	Disadvantages
Alginate [1,44]	Alginate has hydrophilic properties with high viscosity and provide suitable environment for living cells to grow	Alginate hydrogel is too watery. Thus affecting the mechanical stability of the printed hydrogels. The viscosity features of alginate can heal skin tissue damage and promote cells proliferation rates.
Collagen [1,45,46,47]	Collagen can easily found in human and animal with fibrous like structures. Known as biocompatible biomaterial and suitable for supporting tissue adhesion and proliferation. Collagen type I mostly abundant the in human body and support the growth of the skin dermis layers.	Collagen type I will stimulate cytokines reaction such as inflammation and sometimes can cause damage to the skin tissue.
Hyaluronic Acid (HA) [1,48]	HA has hydrophilic properties. It can combine with water due to the speciality of the biochemical structure.	HA has pro-inflammatory and pro-angiogenetic properties.
Chitosan [1,49]	Composed of d-glucosamine and N-acetyl-d-glucosamine. Chitosan has an excellent combination with other natural bioinks.	Less stable if use alone as bioinks. Less solubility in an aqueous media due to its semi-crystalline polymer characteristics.