Development and physicochemical evaluation of chondroitin sulfate-poly(ethylene oxide) hydrogel

Abstract

Novel chondroitin sulfate (CS) -poly(ethylene oxide) (PEO) hydrogel was synthesized and evaluated by a mechanism of self cross-linking of CS derivative with PEO with hexa-thiols (PEO-SH). A derivative of CS was synthesized by the sequential grafting of adipic acid dihydrazide (ADH) and acrylic acid: chemical grafting of ADH to the carboxylic acid in CS (CS-ADH) followed by grafting of the acrylic acid to the free amine groups in the CS-ADH (CS-ADH-Ac). The synthesis of CS-ADH-Ac molecules was confirmed by observing new acrylate peaks in CS-ADH-Ac by FTIR, ESCA, and NMR. The CS-PEO hydrogel was self cross-linked through a Michael type addition reaction between the acrylate end groups of CS-ADH-Ac and the thiol end groups of the PEO-SH. the gelation behavior of 10% CS-PEO was evaluated by rheological analyses from the changes in the solution properties, such as phase angles and visco-elasticities. Rheological analysis indicated that the gelation process was complete within 2 min after mixing two polymer solutions of CS-ADH-Ac and PEO-SH. The fabricated CS-PEO hydrogel was analyzed by measuring both its swelling under different water pHs and its mechanical strength against compression. The morphological shapes of both its surface and cross sections were also evaluated after the sequential processes of gel swelling to equilibrium followed by dehydration. Both the gelation time and swelling of the fabricated hydrogel were dependent on the pH of the polymer solutions and swelling medium, showing quicker gel formation and better swelling behaviors under basic conditions than under acidic conditions. The equilibrated gel showed different morphologies depending on its location, i.e. its cross sections demonstrated more homogeneous morphologies than the surfaces. While the dehydrated hydrogel demonstrated 8-10 µm pore sizes on its cross sections, the compression strength of the hydrogel ranged from 1.4 to 2.8 Pa depending on its gel concentration. Toluidine blue molecules as a model drug were released from the hydrogel over a period of more than 5 days. These hydrogel properties, such as formation of in situ gel, release behaviors of toluidine blue, and porous structures and mechanical properties of the fabricated gel, highlighted the potential of a hydrogel as a carrier for local drug delivery and a scaffold for tissue engineering.

Effect of cross-linking spacers on biocompatibility of chitosan-spacer-poly(ethylene oxide) hydrogel

“…Chitosan-spacer-PEO hydrogel was synthesized by mixing the above two solutions into a 1 mL disposal vial via the Michael type addition reaction without further treatment. Their hydrogelation times were determined by employing the methods of both vial tilting 23 and rheological measurement as reported by our previous reports. 12,23,37 In vitro Cell Behaviors on/in Chitosan-PEO Hydrogel.…”

Induction and biological evaluations of self cross-linking chondroitin sulfate-poly(ethylene oxide) hydrogel

“…Fabrication of CS-PEO hydrogel was previously reported by us in detail. 5 Briefly, after acrylation of CS (CS-acrylate) with sequential grafting of ADH and acrylic acid via EDC chemistry, synthesis of the CS-PEO hydrogel was proceeds through a Michael type addition reaction between precursors such as CS-acrylate and PEO with thiols. Synthesis of CS-acrylate and CS-PEO hydrogel has been described in Figure 1 and reported in detail in our previous report.…”

“…Synthesis of CS-acrylate and CS-PEO hydrogel has been described in Figure 1 and reported in detail in our previous report. 5,6 Evaluation of Gelation Time. Measurement of gelation times was processed by a vial tiling method by tilting the mixture solution in a vial over time.…”

“…21 Fabrications of injectable CS hydrogel have been developed for drug delivery system, cell therapy and tissue engineering of bones. 5,22,23 As an example, Niu et al reported effect of CS on rhBMP-2 release from collagen delivery system. 24 Excellent biocompatibility of the CS-based biomaterials is required for its applications as a medical device such as hydrogel, scaffolds and drug carriers.…”

“…We here fabricated self cross-linking hydrogel under different experimental conditions and evaluated biological properties of a self cross-linking CS-PEO hydrogel for its possible applications in drug or cell delivery and tissue engineering as an injectable form, based on our previous synthesis of the CS-PEO hydrogel. 5 Gel induction conditions such as reaction temperatures and precursor solution component ratios and concentrations, and swelling of the hydrogel have been evaluated. In vitro biological properties such as behaviors of hydrogel degradation by chondrotinase ABC and bone cell behaviors and compatibility have been analyzed in detail.…”