Exfoliation and gelation in laponite–carboxymethyl cellulose complexes and its application in sustained drug release

Abstract

Herein, we have reported the exfoliation of laponite (L) in the presence of carboxymethyl cellulose (CMC) and the formation of CMC–laponite (CMC–L) nanocomposite gel. Analysis of CMC–L complex using XRD confirmed that the addition of CMC actually exfoliates laponites. The interplanar spacing of laponite was observed to increase from 0.74 to 0.98 nm when concentration of CMC, CCMC, increased from 0 to 0.5% w/v in aqueous solution of laponite having concentration of laponite, CL = 1% w/v. Time-dependent scattering intensity studied by dynamic light scattering on CMC–L complex (CCMC = 0.5% w/v, CL = 1% w/v) in aqueous medium illustrated that the exfoliation progresses with the passage of time. It was further observed that the CMC–L complex (CL = 1% w/v, CCMC ≥ 0.5% w/v) forms gel, and the strength of gel increases with the increase in CMC concentration in aqueous medium owing to interaction between exfoliated laponite and CMC. Furthermore, microstructure of the gels and their mesh size were studied using small-angle neutron scattering (SANS). SANS study revealed the fact that with the increase in CCMC from 0.5 to 2% w/v in CMC–L gels, mesh size, ξ decreases from 0.29 to 0.24 nm. This decrease in mesh size is responsible for sustained drug release of methylene blue which was chosen as a cationic model drug. The obtained drug release profile was fitted with different release kinetic models, and it was found that release profile follow first-order kinetic model.