title: Characterization of novel photocrosslinked carboxymethylcellulose hydrogels for encapsulation of nucleus pulposus cells.
abstract: Back pain is a significant clinical concern often associated with degeneration of the intervertebral disc (IVD). Tissue engineering strategies may provide a viable IVD replacement therapy; however, an ideal biomaterial scaffold has yet to be identified. One candidate material is carboxymethylcellulose (CMC), a water-soluble derivative of cellulose. In this study, 90 and 250 kDa CMC polymers were modified with functional methacrylate groups and photocrosslinked to produce hydrogels at different macromer concentrations. At 7 days, bovine nucleus pulposus (NP) cells encapsulated in these hydrogels were viable, with values for the elastic modulus ranging from 1.07 + or - 0.06 to 4.29 + or - 1.25 kPa. Three specific formulations were chosen for further study based on cell viability and mechanical integrity assessments: 4% 90 kDa, 2% 250 kDa and 3% 250 kDa CMC. The equilibrium weight swelling ratio of these formulations remained steady throughout the 2 week study (46.45 + or - 3.14, 48.55 + or - 2.91 and 42.41 + or - 3.06, respectively). The equilibrium Young's modulus of all cell-laden and cell-free control samples decreased over time, with the exception of cell-laden 3% 250 kDa CMC constructs, indicating an interplay between limited hydrolysis of interchain crosslinks and the elaboration of a functional matrix. Histological analyses of 3% 250 kDa CMC hydrogels confirmed the presence of rounded cells in lacunae and the pericellular deposition of chondroitin sulfate proteoglycan, a phenotypic NP marker. Taken together, these studies support the use of photocrosslinked CMC hydrogels as tunable biomaterials for NP cell encapsulation.
authors.affiliation: Department of Bioengineering, University of Pennsylvania, Room 240 Skirkanich Hall, 210 S. 33rd Street, Philadelphia, PA 19104, USA.
authors.forename: Anna T
authors.initials: AT
authors.lastname: Reza
authors.forename: Steven B
authors.initials: SB
authors.lastname: Nicoll
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry*; D002266:Carboxymethylcellulose Sodium / Q000737:chemistry*; D002417:Cattle; D002470:Cell Survival; D002474:Cell-Free System; D003432:Cross-Linking Reagents / Q000737:chemistry / Q000494:pharmacology; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry*; D007403:Intervertebral Disc / Q000166:cytology; D010777:Photochemistry / Q000379:methods; D011108:Polymers / Q000737:chemistry; D011312:Pressure; D013314:Stress, Mechanical; D013997:Time Factors; D023822:Tissue Engineering / Q000379:methods; D014867:Water / Q000737:chemistry
chemical_list: D001672:Biocompatible Materials; D003432:Cross-Linking Reagents; D011108:Polymers; D014867:Water; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D002266:Carboxymethylcellulose Sodium