Development of chitosan-tripolyphosphate fibers through pH dependent ionotropic gelation.
ABSTRACT Incorporation of phosphate groups into a material may be of particular interest as they act as templates for hydroxyapatite growth through complexation with Ca(2+) and thus improve the osteoconduction property. The phosphate groups can be incorporated into chitosan through ionotropic gelation with tripolyphosphate (TPP). Interestingly, the ion pairs formed through negatively charged phosphate groups with protonated amine functionality of chitosan in ionotropic gelation are expected to provide chitosan with an amphoteric character, which may facilitate protein adhesion following enhanced attachment of anchorage dependant cells than chitosan, which shows poor cell adhesion properties. In this study, chitosan-tripolyphosphate (TPP) fibers with varying phosphate contents were prepared through wet spinning in STPP baths of different pH. Gelation kinetics and gel strength of chitosan with STPP solutions of three different pH were evaluated and compared with that of NaOH solution for evaluation of their influence on nature of gelation. The solution pH of STPP baths was found to have significant control on the extent of ionic cross-linking and physico-chemical properties of the fibers. Moreover, this kinetically driven ionotropic gelation of chitosan by TPP results in low degree of crystallinity of chitosan-TPP fibers and consequently their lower thermal stability than chitosan fibers.
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ABSTRACT: This work reports details pertaining to the formation of chitosan nanoparticles that we prepare by the ionic gelation method. The molecular interactions of the ionic cross-linking of chitosan with tripolyphosphate have been investigated and elucidated by means of all-electron density functional theory. Solvent effects have been taken into account using implicit models. We have identified primary-interaction ionic cross-linking configurations that we define as H-link, T-link, and M-link, and we have quantified the corresponding interaction energies. H-links, which display high interaction energies and are also spatially broadly accessible, are the most probable cross-linking configurations. At close range, proton transfer has been identified, with maximum interaction energies ranging from 12.3 up to 68.3 kcal/mol depending on the protonation of the tripolyphosphate polyanion and the relative coordination of chitosan with tripolyphosphate. On the basis of our results for the linking types (interaction energies and torsion bias), we propose a simple mechanism for their impact on the chitosan/TPP nanoparticle formation process. We introduce the β ratio, which is derived from the commonly used α ratio but is more fundamental since it additionally takes into account structural details of the oligomers.Molecular Pharmaceutics 07/2012; 9(10):2856-62. · 4.57 Impact Factor
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ABSTRACT: Tripolyphosphate (TPP) crosslinked chitosan (CH)-based fibrous matrices have potential as bioactive scaffolds for bone tissue engineering. This study describes mechanical, biomineralization, and in vitro bone cell growth and differentiation properties of CH-TPP (chitosan-tripolyphosphate) fibrous scaffolds and compared with that of uncrosslinked CH one. The hydrated CH-TPP scaffolds were viscoelastic in nature and their compressive strength was ∼2.9 MPa, which is greater than recent polymer experimental bone scaffolds. This improvement in mechanical properties of CH-TPP scaffold may be beneficial toward cancellous bone graft application. Furthermore, CH-TPP fibers supported in vitro biomineralization with phosphate as nucleation site; however, no significant difference in biomineralization morphology was observed with uncrosslinked CH fibers. Interestingly, a significant improvement in cellular responses (>33% increase in cell number based on DNA quantification) was observed when osteoblast like cells were cultured on the CH-TPP scaffolds than that of CH scaffolds without phosphate group. Enhanced osteoblastic differentiation of MG63 cells on CH-TPP scaffolds was also evidenced. Altogether, the results show that the CH-TPP fibrous scaffolds are encouraging for bone tissue engineering. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.Journal of Biomedical Materials Research Part A 01/2013; · 2.83 Impact Factor
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ABSTRACT: In this study, chitosan-PEO blend, prepared in a 15M acetic acid, was electrospun into nanofibers (~78nm diameter) with bead free morphology. While investigating physico-chemical parameters of blend solutions, effect of yield stress on chitosan based nanofiber fabrication was clearly evidenced. Architectural stability of nanofiber mat in aqueous medium was achieved by ionotropic cross-linking of chitosan by tripolyphosphate (TPP) ions. The TPP cross-linked nanofiber mat showed swelling up to ~300% in 1h and ~40% degradation during 30 day study period. 3T3 fibroblast cells showed good attachment, proliferation and viability on TPP treated chitosan based nanofiber mats. The results indicate non-toxic nature of TPP cross-linked chitosan based nanofibers and their potential to be explored as a tissue engineering matrix.Materials science & engineering. C, Materials for biological applications. 04/2013; 33(3):1446-54.