Stimulus-responsive hydrogels reinforced by cellulose nanowhisker for controlled drug release

Abstract

Hybrid hydrogels (W–C gels), composed of PDMAEMA, cellulose nanowhisker (CNW) and carboxymethyl chitosan (CMCS), were prepared for developing a stimuli-responsive drug-release system. Compared to the neat gels, W–C gels exhibit improved properties, which are directly dependent on the content of both the CNW and CMCS. For W–C gels, an increase in the CNW has an obvious reinforcement effect, which could be strengthened further by an increased CMCS content, due to the strong interaction between these components. Better compression resistance and elasticity is also observed as the CNW and CMCS content increases. Moreover, the W–C gels retain good swelling capacity with obvious responsiveness to both pH and temperature, which is similar to that of neat gels; the ionization of CMCS increases the swelling ratio of gels in both acidic and alkaline conditions, except in a certain pH region (pH = 4–6), corresponding to the correlative isoelectric points (IEP) of CMCS with PDMAEMA, where a low swelling ratio is found. In the meantime, the increased CNW content brings about a decreased swelling ratio and a faster deswelling rate in the gels. To test the potential of W–C gels as drug carriers, flutamide was used as a target drug to analyze the drug-loading and release properties of the gels. The hybrid gels exhibit better drug-loading ability than neat gels; for W–C gels, a burst release is followed by a slow and sustained release, and the release of the drug could be controlled by deprotonation or protonation of PDMAEMA and CMCS in the gels under different pH conditions; this is fast in alkaline conditions and slow in acidic conditions, and the drug-release mechanism with a changed pH value could be explained by the superposition of Fickian diffusion.