Covalent cross-links in polyampholytic chitosan fibers enhances bone regeneration in a rabbit model

• Published in: Colloids and surfaces, B, Biointerfaces B, Biointerfaces, 2015-01, Vol.125, p.160-169
• Main Authors: Ghosh, Paulomi, Rameshbabu, Arun Prabhu, Das, Dipankar, Francis, Nimmy K., Pawar, Harpreet Singh, Subramanian, Bhuvaneshwaran, Pal, Sagar, Dhara, Santanu
• Format: Article
• Language: English
• Subjects: Amides; Animals; Biocompatible Materials - chemistry; Biocompatible Materials - pharmacology; Bone marrow derived mesenchymal stem cells; Bone Regeneration; Carbodiimides - chemistry; Cell Differentiation; Chitosan; Chitosan - chemistry; Citric acid; Citric Acid - chemistry; Covalence; Cross-Linking Reagents - chemistry; Crosslinking; Dual cross-linking; Elasticity; Energy dissipation; Fibers; Hydration effects; Hydrogen-Ion Concentration; Hydrophobic and Hydrophilic Interactions; Interfacial phenomena; Ion pairs; Mesenchymal Stromal Cells - cytology; Mesenchymal Stromal Cells - drug effects; Mesenchymal Stromal Cells - physiology; Osteogenesis; Osteogenesis - physiology; Primary Cell Culture; Rabbits; Tibia - drug effects; Tibia - injuries; Tibia - physiology; Tibia - surgery; Tissue Engineering; Tissue Scaffolds
• ISSN: 0927-7765; 1873-4367
• DOI: 10.1016/j.colsurfb.2014.11.031

•Citrate–chitosan fibers with dual cross-linking (ionic as well as covalent) were prepared.•The fibers were mechanically unique with twin property of elasticity and energy dissipation.•Improved interfacial properties demonstrated by dual cross-linked fibers.•Enhanced osteogenic differentiation and better osseous regeneration on the fibers. Chitosan fibers were prepared in citric acid bath, pH 7.4 and NaOH solution at pH 13, to form ionotropically cross-linked and uncross-linked fibers, respectively. The fibers formed in citric acid bath were further cross-linked via carbodiimide chemistry; wherein the pendant carboxyl moieties of citric acid were used for new amide bond formation. Moreover, upon covalent cross-linking in the ionically gelled citrate–chitosan fibers, incomplete conversion of the ion pairs to amide linkages took place resulting in the formation of a dual network structure. The dual cross-linked fibers displayed improved mechanical property, higher stability against enzymatic degradation, hydrophobicity and superior bio-mineralization compared to the uncross-linked and native citrate cross-linked fibers. Additionally, upon cyclic loading, the ion pairs in the dual cross-linked fibers dissociated by dissipating energy and reformed during the relaxation period. The twin property of elasticity and energy dissipation mechanism makes the dual cross-linked fiber unique under dynamic mechanical conditions. The differences in the physico-chemical characteristics were reflected in protein adsorption, which in turn influenced the cellular activities on the fibers. Compared to the uncross-linked and ionotropically cross-linked fibers, the dual cross-linked fibers demonstrated higher proliferation and osteogenic differentiation of the MSCs in vitro as well as better osseous tissue regeneration in a rabbit model.