title: Enhancing the stiffness of collagen hydrogels for delivery of encapsulated chondrocytes to articular lesions for cartilage regeneration.
abstract: This study investigated a dual crosslinking paradigm, consisting of (a) photocrosslinking with Rose Bengal (RB) and green light followed by (b) chemical crosslinking with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), and N-hydroxysuccinimide (NHS) to enhance collagen gel stiffness. In group 1, 50 μL collagen constructs of 2% (w/v) type I collagen containing 10 μM RB were allowed to gel spontaneously at 37 °C. In group 2, the spontaneous gels were exposed to green light (532 nm). In group 3, the photochemically crosslinked gels were subsequently treated with a 1-h exposure to 33 mM EDC/6 mM NHS. Samples (n = 18) were subjected to 0.08% (w/v) collagenase digestion, and the storage modulus of samples was measured by rheometry. Viability of encapsulated chondrocytes was measured by live/dead assay. Chondrocytes were ≥ 95% viable in all constructs at 10 days in vitro. Resistance to collagenase digestion increased as; spontaneous gels (2 h) < photochemical gels (3-4 h) < dual crosslinked gels (>24 h). The storage modulus of dual-crosslinked constructs was increased 5-fold over both photocrosslinked and spontaneous gels. As the dual crosslinking paradigm did not reduce encapsulated chondrocyte viability, these crosslinked collagen hydrogels could be a useful tool for the practical delivery of encapsulated chondrocytes to articular defects.
authors.affiliation: Department of Surgery, Plastic Surgery Research Laboratory, Harvard Medical School, Massachusetts General Hospital, Boston, Massachusetts, 02114; Wellman Center for Photomedicine, Harvard Medical School, Massachusetts General Hospital, Boston, Massachusetts, 02114.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Omobono
authors.forename: Xing
authors.initials: X
authors.lastname: Zhao
authors.forename: Michael A
authors.initials: MA
authors.lastname: Furlong
authors.forename: Chi-Heon
authors.initials: CH
authors.lastname: Kwon
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Gill
authors.forename: Mark A
authors.initials: MA
authors.lastname: Randolph
authors.forename: Robert W
authors.initials: RW
authors.lastname: Redmond
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000187:drug effects / Q000473:pathology*; D002470:Cell Survival / Q000187:drug effects; D018914:Cells, Immobilized / Q000166:cytology; D019902:Chondrocytes / Q000166:cytology* / Q000637:transplantation*; D003094:Collagen / Q000494:pharmacology*; D017364:Collagenases / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000494:pharmacology; D055119:Elastic Modulus / Q000187:drug effects; D005782:Gels; D020100:Hydrogels / Q000494:pharmacology*; D008422:Materials Testing; D055595:Mechanical Phenomena; D051381:Rats; D012038:Regeneration / Q000187:drug effects*; D034421:Sus scrofa
chemical_list: D003432:Cross-Linking Reagents; D005782:Gels; D020100:Hydrogels; D003094:Collagen; D017364:Collagenases
keywords: cartilage tissue engineering; collagen; crosslinking; hydrogel; scaffold