Smart carboxymethylchitosan hydrogels that have thermo‐ and pH‐responsive properties

Abstract

Thermo-responsive poly(N-isopropylacrylamide) (poly(NIPAAm)) and pH-responsive poly(N,N 0 -diethylaminoethyl methacrylate) (poly(DEAEMA)) polymers were grafted to carboxymethylchitosan (CMC) via radical polymerization to form highly water swellable hydrogels with dual responsive properties. Ratios of CMC, NIPAAm to DEAEMA used in the reactions were finely adjusted such that the thermo and pH responsiveness of the hydrogels was retained. Scanning electron microscopy (SEM) indicated the formation of an internal porous structure for the swollen CMC hydrogels upon incorporation of poly(NIPAAm) and poly(DEAEMA). Effect of temperature and pH changes on water swelling properties of the hydrogels was investigated. It was found that the water swelling of the hydrogels was enhanced when the solution pH was under basic conditions (pH 11) or the temperature was below its lower critical solution temperature (LCST). These responsive properties can be used to regulate releasing rate of an entrapped drug from the hydrogels, a model drug, indomethacin was used to demonstrate the release. These smart and nontoxic CMC-based hydrogels show great potential for use in controlled drug release applications with controllable on-off switch properties. V C 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41505. Poly(NIPAAm) is a thermo-sensitive polymer and is one of the most studied smart polymers. Poly(NIPAAm) exhibits phase separation at a certain temperature, which is referred to as the lower critical solution temperature (LCST). Poly(NIPAAm) has a LCST of about 32 C in aqueous solution. 9,14-17 When the temperature is below its LCST, poly(NIPAAm) is hydrophilic and soluble in water. The polymer chains are well hydrated and Additional Supporting Information may be found in the online version of this article

Influence of temperature, pH and simulated biological solutions on swelling and structural properties of biomineralized (CaCO3) PVP–CMC hydrogel

“…Till now, these hydrogels with unique characteristics have been implemented and given importance in several field of biomedical applications: wound healing, cell encapsulation, drug delivery, tissue engineering, etc. (Rodkate et al 2015; Nesrinne and Djamel 2013). Further, uses of hydrogels have also been noticed in carrying out the biomineralization process in several in vivo environments (Kim and Park 2014).…”

“…and also the other functional groups present in the backbone of the polymers (Ganji et al 2010). Another aspect of the hydrogels is that the changes observed with the variations seen in surrounding environment of pH, temperature, simulated biological solutions, ionic strength, electric field stimulus and so on (Roy and De 2014; Rodkate et al 2015; Sadeghi and Koutchakzadeh 2007; Chang et al 2010). Due to the presence of some functional groups within the background of the polymeric chain, hydrogels become sensitive to the environmental conditions (Nesrinne and Djamel 2013).…”

“…This type of study becomes interesting in the scientific area to be utilized in the advanced technologies. These types of hydrogels are referred to as stimuli responsive and smart hydrogels (Rodkate et al 2015). Till now, these hydrogels with unique characteristics have been implemented and given importance in several field of biomedical applications: wound healing, cell encapsulation, drug delivery, tissue engineering, etc.…”

“…(Chunyu et al 2011; Giridhar and Akanksha 2011) or peptoid nanosheets (Jun et al 2015). Among all these, in our study cellulose (in derivative form) had been chosen as the best candidate to form hydrogel as cellulose is abundantly available in nature, biodegradable, having good water absorbing capacity and biocompatible too (Sadeghi and Hosseinzadeh 2010; Rodkate et al 2015). In due course, to accomplish and maintain both hydrophilic and mechanical properties within the so-called “biobased hydrogel”, PVP is added to form a blend of carboxymethylcellulose (CMC) and polyvinylpyrrolidone (PVP) within the hydrogel.…”

Functional Hydrogels and Their Application in Drug Delivery, Biosensors, and Tissue Engineering

“…Additionally, hydrogels will not affect the metabolic processes of living organisms and metabolites can pass freely through the hydrogels. Hydrogels are also sensitive to small changes in external stimuli, such as temperature, pH, ionic strength, electric fields, and magnetic fields, and can respond to these stimuli through volume swelling or shrinking [7][8][9][10][11]. Therefore, hydrogels are more similar to living tissues, specifically the outer membrane of the cell matrix, than any other currently known synthetic biomaterials and these properties result in reducing friction and mechanical effects on the surrounding tissues, which significantly improves the biological properties of the material [12].…”