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.
"), 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. "
[Show abstract][Hide abstract] ABSTRACT: A thermo-sensitive comb-like copolymer was synthesized by grafting PNIPAAm-COOH with a single carboxy end group onto aminated alginate (AAlg) through amide bond linkages. In the copolymer, alginate was the backbone and poly(N-isopropylacrylamide) (PNIPAAm) was the pendant group. The structures of AAlg and three AAlg-g-PNIPAAm copolymers with different PNIPAAm grafting ratios were determined by FTIR and 1H NMR. The rheological properties of AAlg-g-PNIPAAm copolymer hydrogels were measured by monitoring the viscosity, storage modulus and loss modulus as a function of temperature. The lower critical solution temperature of AAlg-g-PNIPAAm copolymers was measured as 35°C through rheological analysis. An in vitro degradation study was carried out by monitoring weight loss. It was confirmed that degradation can be controlled by PNIPAAm modification. Encapsulation of human bone mesenchymal stem cells (hBMSCs) within hydrogels showed that the AAlg-g-PNIPAAm copolymer was not cytotoxic and preserved the viability of the entrapped cells well. The thermo-sensitive AAlg-g-PNIPAAm copolymer has attractive properties that make it suitable as cell or pharmaceutical delivery vehicles for a variety of tissue engineering applications.
[Show abstract][Hide abstract] ABSTRACT: In this study, a novel semi-interpenetrating polymer network (semi-IPN) hydrogel of poly(diallyldimethylammonium chloride)/poly(N,N-diethylacrylamide) (PDADMAC/PDEA) was prepared using ammonium persulfate as an initiator and N,N,N′,N′-tetramethylethylenediamide as an accelerator at room temperature. The influence of this additive on the property of resulting PDEA hydrogels was investigated and characterized. The interior morphology by scanning electron microscopy (SEM) revealed that PDADMAC introduced PDEA hydrogels have large and interconnected porous network structures. Differential scanning calorimetry (DSC) studies showed the difference in the state of the water between PDEA and semi-IPN hydrogels. The incorporating of PDADMAC significantly improved the equilibrium swelling ratio of modified hydrogels when comparing with a normal PDEA hydrogel. The semi-IPN hydrogels exhibited improved thermosensitive characteristics, such as faster deswelling and swelling rates and great oscillating deswelling–swelling behavior, and the level of improvement depended on the PDADMAC content. The swelling dynamic transport of the hydrogels was analyzed based on the Fickian equation.
The Chemical Engineering Journal 05/2010; 159(1-159):247-256. DOI:10.1016/j.cej.2010.02.034 · 4.32 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The poly(N,N-diethylacrylamide-co-(2-dimethylamino)ethyl methacrylate) (poly(DEA-co-DMAEMA)) macromonomers with three different chain lengths were prepared by telomerization of DEA and DMAEMA monomers with different ratios of the chain transfer agent, 2-mercaptoethanol. The number-average weight of three macromonomers determined by gel permeation chromatography of the terminal hydroxyl groups was 8355, 10,516 and 15,953, respectively. The comb-type grafted poly(DEA-co-DMAEMA) hydrogels having the different lengths of the grafted chains were synthesized in the presence of crosslinker. Equilibrium and dynamic swelling/deswelling properties of the prepared hydrogels responding to temperature and pH were investigated. Compared to normal-type hydrogel, the comb-type grafted hydrogels exhibited excellent variational values in response to an alternation of the temperature and pH. Moreover, the grafted hydrogels showed quite fast reswelling and deswelling behaviors in response to simultaneous dual temperature and pH stimuli. This is because that the introduction of side chains with freely mobile ends in the comb-type grafted hydrogels made the mobility of the networks increased. The responsive rates of the grafted hydrogels were also controlled by modifying the length of the grafted chains. The dual thermo- and pH-sensitive comb-type grafted poly(DEA-co-DMAEMA) hydrogels in this study may find various potential applications.
Sensors and Actuators B Chemical 08/2010; 149(1):34-43. DOI:10.1016/j.snb.2010.06.034 · 4.10 Impact Factor
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