Comparative study of capsaicin molecularly imprinted polymers prepared by different polymerization methods

Abstract

In this study, the molecularly imprinted polymers (MIPs) of capsaicin are prepared by bulk polymerization (MIPs1), precipitation polymerization (MIPs2), and surface imprinting technology based on SiO2/Fe3O4 particles (MIPs3), respectively. MIPs are characterized by scanning electron microscopy and fourier transform infrared spectroscopy. The adsorption kinetics and thermodynamics of these composites are also investigated to estimate their capacity to rebind capsaicin. The adsorption kinetics show that the adsorption process of MIPs1 is fitted to pseudo first‐order kinetic model, while the kinetic properties of MIPs2 and MIPs3 are well described by pseudo second‐order kinetic model. Adsorption thermodynamics analysis indicated that there are two kinds of binding sites with different affinity in each MIPs, whereas only one kind of binding site in non‐imprinted polymers. All adsorption isotherms of MIPs are fitted to Freundlich models, illustrated that binding sites are distributed heterogeneously in the surface of the materials, and the adsorption might occur in the multimolecular layers. Comparisons of experimental data of three MIPs are achieved and the results show that MIPs3 has the best affinity and absorption capacity to capsaicin. Moreover, the MIPs3 maintain the magnetic properties of Fe3O4 particles, which will be applied to the rapid separation of capsaicin from chili peppers samples. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 157–164

Molecularly Imprinted Polymers (MIPs) as Theranostic Systems for Sunitinib Controlled Release and Self-Monitoring in Cancer Therapy

“…The Freundlich isotherm is introduced as an empirical model, which involves a non-ideal adsorption process on heterogeneous surfaces assuming that as the analyte concentration increases, the concentration of the analyte on the adsorbent surface will increase. Contrary to the Langmuir model described above, this one is not limited to the formation of a monolayer, but it assumes that the polymer surface recognition holes are not evenly distributed and the adsorption might occur in the multimolecular layer [34]. Freundlich isotherm is explained by the following Equation 7and its linear form 8:…”

“…log(Q e − Q t ) = log(Q e ) − K 1 2.303 t (10) in which Q e is the amount of adsorbed SUT at the equilibrium time, K 1 represents the first-order adsorption rate constant, and t is the adsorption time. This model is based on the assumption that one molecule adsorbs within the active site of the polymer [36] and that the drug adsorption process controlled by the diffusion step belongs to the physical adsorption [34].…”

“…where K 2 is the pseudo-second order adsorption rate constant. This kinetic model assumes that one adsorbate molecule interacts with two active sites [36] and that the adsorption process is a chemical process, which could be the rate-limiting step [34].…”

Sample Preparation Using Molecularly Imprinted Polymers

“…107 Wang et al recently compared different polymerization methods to produce a MIP for capsaicin such as bulk, precipitation polymerization, that give rise to non magnetic particles, and surface imprinting technology based on silanized Fe3O4 NPs, showing that the latest possess the best affinity and adsorption capacity. 171 At last, to prepare a HRP-MIP, boronic acid was grafted on Fe3O4 NPs covered by a porous TiO2 layer instead of a silica layer before the polymerization with dopamine in order to improve the specific surface area of the sorbent, since the surface of Fe3O4@TiO2 is much rougher, which is beneficial to offer more binding sites. 111 The measurement of the specific surface area is a parameter indicating the potential binding capacity of the MIP but it is also important to check for the presence of cavities.…”

Redesigning an Electrochemical MIP Sensor for PFOS: Practicalities and Pitfalls

“…Electrochemical techniques were employed to study the charge transfer on the modified electrode surface and to gather information about the imprinting process and overall performances of the sensor [16,17]. Imaging techniques were applied to map the morphology and properties of the bare electrode and the MIP-modified ones [15,18]. Thanks to the high concentration of fluorine in the template/target molecule, it was possible to visualize the MIP distribution by field-emission scanning electron microscopy–energy-dispersive X-ray spectrometry (FE-SEM–EDS) imaging.…”