A pH‐controllable imprinted composite membrane for selective separation of podophyllotoxin and its analog

Abstract

A molecularly imprinted composite membrane (MICM) with pH-controllability and selectivity to podophyllotoxin (PPT) was prepared using a polyvinylidene fluoride (PVDF) microfiltration membrane as the support. The functional monomer is 1-phenyl-3-methyl-4-methacryloyl-5-pyrazolone (PMMP), which is a new b-diketone compound with enol/ketol tautomerization. In this study, imprinting parameters, including the amounts of functional monomer and cross-linker, and immersion time of membrane in the imprinting solution, were optimized by equilibrium adsorption experiments. Pore structure and surface morphology of the optimal MICM (MICM 2 ) was characterized. Finally, competitive permeability of PPT in the presence of its analog 4'-demethylpodophyllotoxin (DMEP) was measured under the drive of concentration difference. The results reveal that the surface morphology and pore structure of MICM 2 are structurally different from those of the control nonimprinted membrane. As a result, MICM 2 could efficiently recognize PPT in a complex system due to a better structural matching and the interaction between the functional groups of MICM 2 and PPT. However, the most interesting finding is its pH-controllability. The membrane could switch the preference to either PPT or DMEP with the change of pH values in the sample solution. At pH values smaller than 8.4, it led to a faster transportation of PPT, while the situation reversed to DMEP at pH values greater than 8.4. This peculiar property would lead this imprinted membrane to have potential application in the separation and enrichment of PPT, and the new functional monomer PMMP exhibited an attractive application prospect in the functional material fields.

Synthesis and evaluation of ion-imprinted composite membranes of Cr(vi) based on β-diketone functional monomers

“…In addition, the structure of ADPD may vary between keto and enol forms under conditions of altered solvent polarity, which can impact the interactions between it and the template ions. 22,27 Therefore, in order to design IICMs with good recognition towards Cr( vi ), a series of experiments were carried out using different types of solvents and varying ratios of Cr( vi ) to ADPD and EDMA.…”

“…Among all ion-imprinted composite membranes (IICMs), the stimuli-responsive membrane is one of the most attractive materials. 22,40 It has the potential to modify its permeation selectivity for metal ions by grafting pH-responsive or temperature-responsive polymers on the substrate membrane. However, the functional monomers currently available for use are almost limited to acrylic acid, methacrylic acid or N -isopropylacrylamide.…”

“…Their enol/ketone group isomerization with changes in polarity or pH in solvents has attracted increasing interest from scientists and has been applied in the field of functional materials. 22 It would be an interesting study to explore a novel stimuli-responsive smart membrane with predetermined affinity for Cr( vi ) using β-diketone compounds as functional monomers.…”

Green Chemistry and Molecularly Imprinted Membranes

“…Over time, these approaches were improved and strategically combined for producing advanced membranes [ 238 , 239 , 240 , 241 , 242 , 243 , 244 , 245 , 246 , 247 , 248 ].…”

Recent Advances in the Chemistry and Biology of Podophyllotoxins

“…However, the extraction of podophyllotoxin is always tedious and inefficient because of the poor affinity and selectivity of conventional separation materials. Effective materials and methods for the separation of podophyllotoxin have recently been developed, and new plant sources for podophyllotoxin and its analogues have been discovered –. Given intensive collection of plants from the wild and long plant growth period, the availability of podophyllotoxin and its analogues is limited from natural resources.…”