Thermally reversible colloidal gels for three-dimensional chondrocyte culture

Abstract

Healthy cells are required in large numbers to form a tissue-engineered construct and primary cells must therefore be increased in number in a process termed 'expansion'. There are significant problems with existing procedures, including cell injury and an associated loss of phenotype, but three-dimensional culture has been reported to offer a solution. Reversible gels, which allow for the recovery of cells after expansion would therefore have great value in the expansion of chondrocytes for tissue engineering applications, but they have received relatively little attention to date. In this study, we examined the synthesis and use of thermoresponsive polymers that form reversible three-dimensional gels for chondrocyte cell culture. A series of polymers comprising N-isopropylacrylamide (NIPAM) and styrene was synthesized before studying their thermoresponsive solution behaviour and gelation. A poly(NIPAM-co-styrene-graft-N-vinylpyrrolidone) variant was also synthesized in order to provide increased water content. Both random-and graft-copolymers formed particulate gels above the lower critical solution temperature and, on cooling, re-dissolved to allow enzyme-free cell recovery. Chondrocytes remained viable in all of these materials for 24 days, increased in number and produced collagen type II and glycosaminoglycans.

Photo-active collagen systems with controlled triple helix architecture

“…Figure 3 displays exemplary spectra of CRT (A), CRT-4VBC blend (B, 50 4VBC/Lys molar excess) and CRT-4VBC25 (C). Here, geminal protons of 4VBC (at 5.2-6.7 ppm32) were successfully identified in the functionalized sample in contrast to the CRT control. At the same time, the CRT-4VBC blended mixture was also analysed as an additional control; here, the 1 H-NMR spectrum mainly displays 4VBC-related peaks, while the presence of CRT was not detected, likely related to the excess of 4VBC with respect to the collagen lysines.…”

“…However, although aromatic residues are not supposed to form triple helix-stabilizing hydrogen bonds, they are well-known to mediate other secondary interactions, i.e. π-π stacking or hydrophobic interactions 32. It is therefore likely that these physical interactions account for the comparable thermal stability of 4VBC-based solutions in comparison with native collagen solutions.…”

“…Following isolation in-house, type I collagen was reacted with either 4-vinylbenzyl chloride (4VBC) or glycidyl methacrylate (GMA). 4VBC was selected based on its backbone rigidity, hydrophobicity, and biocompatibility 32. 4VBC-based systems were therefore expected to display reduced swellability and increased mechanical properties (i.e.…”

Reactive Oxygen Species Shielding Hydrogel for the Delivery of Adherent and Nonadherent Therapeutic Cell Types

“…22 In particular, type 1 collagen (T1C) is one of the most abundant structural proteins found in almost all tissue and promotes robust cellular adhesion. 29 Similar to PNIPAAM-based polymers, T1C solutions also undergo thermoresponsive gel formation, 30 therefore making incorporation of T1C into PDN hydrogels an attractive strategy for increasing the cellular adhesion capacity of these materials. Herein, we have extended the utility and retained the injectability of PDN hydrogels by incorporating collagen into these materials to improve the adhesion, growth, and proliferation of both adherent and nonadherent cells in 3D culture.…”

Effect of adhesive ligand on cell deadhesion kinetics on poly(N-isopropylacrylamide)

“…Recently, the emergence of thermo-responsive polymer (TRP) has enabled the culture and recovery of various tissues including cardiac myocytes, hepatocytes, chondrocytes and aortic endothelial cells [1][2][3]. For instance, chondrocytes has been shown to produce collagen type II and glycosaminoglycans for twenty four days in a three dimensional gel composed of poly(N -isopropylacrylamide) (PIPAAm), a common TRP, which allows enzyme free tissue recovery below its lower critical solution temperature (LCST) [3].…”