title: Triple-helical collagen hydrogels via covalent aromatic functionalization with 1,3-Phenylenediacetic acid.
abstract: Chemical crosslinking of collagen is a general strategy to reproduce macroscale tissue properties in physiological environment. However, simultaneous control of protein conformation, material properties and biofunctionality is highly challenging with current synthetic strategies. Consequently, the potentially-diverse clinical applications of collagen-based biomaterials cannot be fully realised. In order to establish defined biomacromolecular systems for mineralised tissue applications, type I collagen was functionalised with 1,3-Phenylenediacetic acid (Ph) and investigated at the molecular, macroscopic and functional levels. Preserved triple helix conformation was observed in obtained covalent networks via ATR-FTIR (AIII/A1450~ 1) and WAXS, while network crosslinking degree (C: 87-99 mol.-%) could be adjusted based on specific reaction conditions. Decreased swelling ratio (SR: 823-1285 wt.-%) and increased thermo-mechanical (Td: 80-88 °C;E: 28-35 kPa;σmax: 6-8 kPa;εb: 53-58 %) properties were observed compared to state-of-the-art carbodiimide (EDC)-crosslinked collagen controls, likely related to the intermolecular covalent incorporation of the aromatic segment. Ph-crosslinked hydrogels displayed nearly intact material integrity and only a slight mass decrease (MR: 5-11 wt. %) following 1-week incubation in either PBS or simulated body fluid (SBF), in contrast to EDC-crosslinked collagen (MR: 33-58 wt. %). Furthermore, FTIR, SEM and EDS revealed deposition of a calcium-phosphate phase on SBF-retrieved samples, whereby an increased calcium phosphate ratio (Ca/P: 0.84-1.41) was observed in hydrogels with higher Ph content. 72-hour material extracts were well tolerated by L929 mouse fibroblasts, whereby cell confluence and metabolic activity (MTS assay) were comparable to those of cells cultured in cell culture medium (positive control). In light of their controlled structure-function properties, these biocompatible collagen hydrogels represent attractive material systems for potential mineralised tissue applications.
authors.affiliation: Biomaterials and Tissue Engineering Research Group, Leeds Dental Institute, University of Leeds, Leeds LS2 9LU, United Kingdom; Nonwoven Research Group, Centre for Technical Textiles, University of Leeds, Leeds LS2 9JT, United Kingdom.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Tronci
authors.affiliation: Biomaterials and Tissue Engineering Research Group, Leeds Dental Institute, University of Leeds, Leeds LS2 9LU, United Kingdom; Nonwoven Research Group, Centre for Technical Textiles, University of Leeds, Leeds LS2 9JT, United Kingdom.
authors.forename: Amanda
authors.initials: A
authors.lastname: Doyle
authors.affiliation: Nonwoven Research Group, Centre for Technical Textiles, University of Leeds, Leeds LS2 9JT, United Kingdom.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Russell
authors.affiliation: Biomaterials and Tissue Engineering Research Group, Leeds Dental Institute, University of Leeds, Leeds LS2 9LU, United Kingdom.
authors.forename: David J
authors.initials: DJ
authors.lastname: Wood