Scaffolds for Cartilage Tissue Engineering:

Tissue engineered additive manufactured scaffolds for cartilage repair, shows high prospective for growing adult cartilage tissue.

Articular cartilage is the connective tissue that allows for the frictionless movement of bone within the synovial joints of the body. Its extracellular matrix consists of a combination of different types of collagen and proteoglycans that together are responsible for the viscoelastic and swelling properties of the tissue. Both natural and synthetic polymers have considered as substrate materials for the fabrication of 3D support structures. While natural source compounds, such as gelatin and alginates, are more bioactive and truly biodegradable, synthetic polymers are more predictable, reproducible, and scalable in terms of chemical and physical properties and offer a stronger structural support. Depending on the chosen scaffold fabrication technique and the end-application, both types of resources can be valid options. Among the different synthetic polymers, biodegradable thermoplastics such as Poly-L-lactic acid (PLLA), poly-ε-caprolactone (PCL) and poly (ethylene oxide terephthalate)/poly (butylene terephthalate)  are of particular interest, as they are relatively cheap, commercially available, easily manipulated and exhibit excellent structural properties. Other one is   fixed degradation rates, acidic degradation products, low elasticity and limited bioactivity.

To extract a proper bioactive response from these 3D scaffolds is now one of the main challenges today. Extensive literature is available on the enhancement of thermoplastic elastomers for cartilage repair in 2D configuration through surface modifications, yet literature on surface modifications of 3D scaffolds is rather limited. An alternative approach towards the effective modification of 3D polymeric scaffolds is non-thermal plasma technology (NTP). NTP is a well-established gas-based technique typically used for altering the surface chemical composition of any exposed substrate. When feeding an inert gas such as argon, air or helium to generate the plasma discharge, radical sites are generated, resulting in the incorporation of polar functional groups, a process that is often referred to as plasma activation. When feeding the gaseous film precursor into the reactor after activation, but without employing the discharge, the process is referred to as plasma grafting. If a plasma discharge is active while feeding the precursor gas, the deposition process is defined as plasma polymerization. Unlike traditional polymerization reactions, plasma “polymers” are known to be extensively cross-linked, pinhole free, and highly adherent. Compared to wet-chemical deposition processes, plasma polymerization can be favorable for the deposition of thin films on geometrically complex biodegradable polymer structures, as it is 1) a solvent-free technique, thus generating no waste and avoids the use of toxic solvents, 2) time-efficient, with deposition runs typically no longer than 30 min, 3) gas-based, thus allowing for a more efficient penetration throughout the porous scaffold, 4) non-invasive, not altering the bulk properties of the used biodegradable polymer.

Generally, scaffolds have shown potential for cartilage tissue engineering applications.