Thermoresponsive poly(N‐isopropylacrylamide)‐g‐methylcellulose hydrogel as a three‐dimensional extracellular matrix for cartilage‐engineered applications

Abstract

Recent advances in tissue engineering and regenerative medicine fields can offer alternative solutions to the existing techniques for cartilage repair. In this context, a variety of materials has been proposed, and the injectable hydrogels are among the most promising alternatives. The aim of this work is to explore the ability of poly(N-isopropylacrylamide)-g-methylcellulose (PNIPAAm-g-MC) thermoreversible hydrogel as a three-dimensional support for cell encapsulation toward the regeneration of articular cartilage through a tissue engineering approach. The PNIPAAm-g-MC copolymer was effectively obtained using ammonium-persulfate and N,N,N',N'-tetramethylethylenediamine as initiator as confirmed by Fourier transform infrared spectroscopy and (1) H NMR results. The copolymer showed to be temperature responsive, becoming a gel at temperatures above its lower critical solution temperature (~ 32 °C) while turning into a liquid below it. Results obtained from the MTS test showed that extracts of the hydrogel were clearly noncytotoxic to L929 fibroblast cells. ATDC5 cells, a murine chondrogenic cell line, were used as the in vitro model for this study; they were encapsulated at high cell density within the hydrogel and cultured for up to 28 days. PNIPAAm-g-MC did not affect the cell viability and proliferation, as indicated by both MTS and DNA assays. The results also revealed an increase in synthesis of glycosoaminoglycans within culture time measured by the dimethylmethylene blue quantification assay. These results suggest the viability of using PNIPAAm-g-MC thermoresponsive hydrogel as a three-dimensional scaffold for cartilage tissue engineering using minimal-invasive strategies.

Injectable hydrogels

“…Natural repair of cartilage tissue is a slow process where the limiting factor is the availability and transport of new chondrocytes to the area of injury. 162 To address this limitation, development of materials for cartilage TE is largely focused on efficient means of delivering chondrocytes to the site of injury. A number of hybrid injectable hydrogel constructs have been proposed where data suggests that the incorporation of cartilage-specific GAGs, PGs (e.g., HA, heparin sulfate, tyramine, and chondroitin sulfate) and peptide sequences can support chondrocyte growth and promote formation of new ECM matrix both in vitro and in vivo.…”

“…A hydrated environment is essential for cell survival because it mediates transport of nutrients and waste products to and from the extracellular space; syneresis may interfere with this process. 162 For example, poly(NIPAAm) homopolymer gels exhibit shrinking behavior to the extent that they are impractical for cell encapsulation. 49 However, several formulations of poly(NIPAAm) have shown promise for cell delivery in various TE applications, largely though the incorporation of hydrophilic segments such as AAc 167 or PEG 168 that counteract syneresis.…”

“…S a-Lima et al 162 explored the capacity of this system to encapsulate murine chondrocytes and found the material to be nontoxic to fibroblast and chondrocytes in vitro while enhancing GAG production. Furthermore, the authors provide evidence of transplanted cells maintaining chondrocytic lineage and signs of PG-and GAG-containing ECM production after 4 weeks, although it is worth noting that the poly(NIPAAm) portions of this material are nondegradable.…”

Stem Cell Research: A New Era for Reconstructive Surgery

“…Such combinations have also been used to create a 3-D structure with spatially-varying mechanical properties to mimic the native extra cellular matrix (ECM) composition. [27][28][29][30] Great progress has been achieved in cartilage tissue engineering during the past decades, however, some issues still remain in this area, for example the directed differentiation of stem cells, the simulation of actual physiological condition into the body, the integration of tissue engineered cartilage to the body, and so on. Growth factors have been found to be promising in the directed differentiation of stem cells.…”

Self-Assembled Glucose and Thermo Dual-Responsive Micelles of an Amphiphilic Graft Copolymer

“…These polymers have been used in diverse applications such as self-regulated drug delivery systems, artificial muscles, chemical valves, specialized separation systems, and immobilization of enzymes and cells [3][4][5][6][7][8]. Similar to artificial pancreas, self-regulated insulin release systems could deliver suitable amount of insulin in due time according to the blood glucose level in diabetic patients [9][10][11].…”