Natural and synthetic biodegradable polymers: different scaffolds for cell expansion and tissue formation

The formation of tissue produced by implanted cells is influenced greatly by the scaffold onto which they are seeded. In the long term it is often preferable to use a biodegradable material scaffold so that all the implanted materials will disappear, leaving behind only the generated tissue. Research in this area has identified several natural biodegradable materials. Among them, hydrogels are receiv-ing increasing attention due to their ability to retain a great quantity of water, their good biocom-patibility, their low interfacial tension, and the minimal mechanical and frictional irritation that they cause. Biocompatibility is not an intrinsic property of materials; rather it depends on the biological environment and the tolerability that exists with respect to specific polymer-tissue interactions. The most often utilized biodegradable synthetic polymers for 3D scaffolds in tissue engineering are satu-rated poly-a-hydroxy esters, including poly(lactic acid) (PLA) and poly(glycolic acid) (PGA), as well as poly(lactic-co-lycolide) (PLGA) copolymers. Hard materials provide compressive and torsional strength; hydrogels and other soft composites more effectively promote cell expansion and tissue formation. This review focuses on the future potential for understanding the characteristics of the biomaterials considered evaluated for clinical use in order to repair or to replace a sizable defect by only harvesting a small tissue sample.