Zipper-like thermosensitive molecularly imprinted polymers based on konjac glucomannan for metformin hydrochloride

Abstract

Zipper-like thermosensitive molecularly imprinted polymers (MIPs) based on konjac glucomannan (KGM) for metformin hydrochloride were prepared using KGM, a natural polysaccharide, as the matrix, acrylamide (AM) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) as the comonomers, N, N′-methylenebis(acrylamide) as the cross-linking agent, ceric ammonium nitrate as the initiator, and metformin hydrochloride as the template molecule. The resultant MIPs were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectrometry (XPS), X-ray diffractometry (XRD), thermal gravimetric analyzing (TGA), and scanning electron microscopy (SEM). The interpolymer interactions between poly (AM) and poly (AMPS) were demonstrated by the results of ultraviolet spectrometry (UV), indicating that MIPs with zipper-like structure could be fabricated. The thermo-responsive MIPs with on/off-switchable characteristic were evaluated by the method of cyclic voltammetry (CV). The adsorption experiment showed that the target molecules could be controlled to be adsorbed/desorbed by changing the external temperature. The adsorption capacity at high temperature was higher than that at low temperature. Moreover, the adsorption capacity of MIPs was much higher than that of NIPs. The results of adsorption experiments showed that the MIPs could specifically recognize and adsorb metformin with excellent selectivity, repeatability, and stability. Langmuir equation and Freundlich equation were applied to fit the adsorption isotherms of MIPs and the results showed that the Langmuir equation fitted better than the Freundlich equation. The product is expected to serve as a novel adsorption and separation material.