Table 1.

Natural materials used to prepare 3D scaffolds.

Natural Materials and Their Chemical Structure	SPR	Merits	Demerits	References
Collagen	Hydrogen bonds hold the structure. Presence of glycine, proline, and hydroxyproline.	Biocompatible and biodegradable. Non-toxic. Less immunogenic. Extracellular matrix secretion.	Poor mechanical properties. Less stable.	[44]
Fibrinogen	Presence primary and secondary amines in the structure. It consists of polypeptide chains.	High cellular uptake. Hemostatic properties. High cell adhesion properties. High surface-to-volume ratio.	Fast degradation. Poorly stable.	[41]
Gelatin [45,46]	Consists of glycine, proline, and 4-hydroxyproline.	It can be used as a crosslinking agent. It helps to enhance the expansion ratios of other polymers. Excellent cell adhesion, proliferation, and differentiation properties. Less immunogenic. Biodegradable. Biocompatible.	Low stability.	[45,46]
Keratin	Presence of cysteine residues. Structural stability comes from intermediate filaments.	Excellent cell proliferation properties. Self-assemble. High cell viability. Controlled release properties. Time-dependent degradation profile.	Poor structural integrity at biological environment.	[47]
Starch	Consists of α-glycans. Carbohydrates.	Cytocompatibility. Excellent cell adhesion profiles. Highly hydrophilic Biodegradable. Suitable for photothermal therapy.	High water absorption ability. Poor mechanical properties. Difficult to chemical modification.	[48]
Chitosan	Linear polysaccharides. Beta-(1→4)-linked D-glucosamine	Highly porous structure. Hemostatic properties. High thermal stability. Inhibits liver metastasis. Inhibits growth factor-based proliferation of tumor cells.	Poor solubility in water. Susceptible to proteolytic enzymes.	[49,50]
Chitin	Presence of N-acetylglucosamine and N-glucosamine	It can be used for tissue repairing after breast cancer surgery. Non-toxic. Anti-inflammatory. Inhibits angiogenesis in tumors.	Poor stability. Poor solubility.	[51]
Agarose	Agarobiose units are linked by hydrogen bonds.	Injectable in liquid form that later forms gel at body temperature. Excellent for cell delivery to target organs. It does not enhance immunogenicity. Biocompatible and biodegradable.	Non-degradable. Poor cell attachment.	[52,53]
Alginate	Different units of alginate have different properties. Presence of -COOH groups that can be chemically linked with anticancer drugs. Presence of guluronate units that inhibit metastasis.	It can mimic natural ECM. Inhibits tumor cell proliferations due to gel-forming properties at body temperature. Highly hydrophilic. Biocompatible and biodegradable.	Poor mechanical strength. Difficult to use in cell-based anticancer therapy due to poor cell adhesion properties.	[54]
Cellulose	The glucose units are linked by glycosidic bonds and thereby form a polysaccharide structure.	Excellent mechanical properties. Hydrophilic in nature. Non-toxic.	Non-degradable.	[55]
Hyaluronic acid (HA)	It consists of repeating disaccharide units. Presence of -OH and -COOH groups on the surface that can be chemically crosslinked with anticancer drugs.	High drug-loading properties. Facilitates tumor cell targeting properties. High degradable profile. Non-immunogenic.	Poor degradation profile. Unstable structure due to poor mechanical properties.	[56]
Glycosaminoglycans	Individual disaccharide units are linked together by glycosidic bonds.	Anticancer activity. Prevents blood clots. Inhibits inflammatory pathway. Inhibition of metastasis.	Microbial Contamination.	[57]