Thermoresponsive hydrogels based on poly(N-isopropylacrylamide)/chondroitin sulfate

Department of Biomedical Engineering, Hanyang University, Seoul 133-791, Republic of Korea
Sensors and Actuators B Chemical (Impact Factor: 4.1). 12/2008; 135(1):336-341. DOI: 10.1016/j.snb.2008.09.001


A fast, thermoresponsive hydrogel composed of poly(N-isopropylacrylamide) (PNIPAm) and chondroitin sulfate (ChS) was synthesized using precipitation polymerization. ChS was introduced to increase the water absorption of the PNIPAm hydrogel, and the precipitation polymerization method was used to induce a porous network morphology to enhance the thermal response of the hydrogel. PNIPAm/ChS hydrogels (15:7.5 wt.%) underwent a very fast deswelling, within a period of approximately 2 min, due to the presence of a large free water content (∼90–94%), which was associated with the interconnected filamentous morphology within the hydrogel. The swelling ratio was greatly enhanced by the addition of ChS. The hydrogels exhibited stable thermoactuation behavior, following a volume change of 75% while cycling the temperature between 20 and 45 °C.

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Available from: Yahya Ismail, Jan 27, 2016
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    • "This dehydration of the polymer chains could potentially result in cellular exclusion from the matrix and excessive volume loss. However, the fixed negative charges on chondroitin sulfate (–COO -and –SO 3 -) at neutral pH have been shown to enhance osmotic pressure of highly crosslinked PNIPAAm networks[50]. Water loss data for our in situ forming system at 37 °C, shown in Fig. 1, is consistent with these prior findings. The PNIPAAm homopolymer gel exhibited an approximate 83.0 ± 3.6 % water loss over the 14 day period. "
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    ABSTRACT: The goal of this work is to develop an injectable nucleus pulposus (NP) tissue engineering scaffold with the ability to form an adhesive interface with surrounding disc tissue. A family of in situ forming hydrogels based on poly(N-isopropylacrylamide)-graft-chondroitin sulfate (PNIPAAm-g-CS) were evaluated for their mechanical properties, bioadhesive strength, and cytocompatibility. It was shown experimentally and computationally with the Neo-hookean hyperelastic model that increasing the crosslink density and decreasing the CS concentration increased mechanical properties at 37 °C, generating several hydrogel formulations with unconfined compressive modulus values similar to what has been reported for the native NP. The adhesive tensile strength of PNIPAAm increased significantly with CS incorporation (p < 0.05), ranging from 0.4 to 1 kPa. Live/Dead and XTT assay results indicate that the copolymer is not cytotoxic to human embryonic kidney (HEK) 293 cells. Taken together, these data indicate the potential of PNIPAAm-g-CS to function as a scaffold for NP regeneration.
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    • "), hyaluronic acid (Ha et al., 2006; H.P. Tan et al., 2009), chondroitin sulfate (Varghese et al., 2008) or other polymers to adjust its gelling temperature and mechanical properties. This is to preserve the viability and phenotypic morphology, as well as improve proliferation, differentiation and extracellular matrix secretion of the cells entrapped within the hydrogel. "
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