Innovative Methods of Synthesis and Characterization for Molecularly Imprinted Polymers

The characterization of these molecularly imprinted polymers is essential to understanding their binding dynamics and structural properties. Through the analysis of the current research, it is found that there are overlaps in the methods used by scholars. The Langmuir equation is frequently applied to model the adsorption isotherms of MIPs, providing critical insight into the capacity and affinity of the binding sites. Infrared Spectroscopy (IR) plays a crucial role in identifying the functional groups involved in the imprinting process and confirming the successful formation of specific binding sites. UV-visible spectrophotometry is employed to monitor the absorption characteristics of the polymers, offering data on the interactions between the template molecules and the polymer matrix. Transmission Electron Microscopy (TEM) provides detailed visualization of the internal structure of MIPs at the nanoscale, revealing the morphology and size of the imprinted cavities. Thermogravimetric Analysis (TGA) assesses the thermal stability and composition of the polymers, identifying decomposition patterns that are indicative of the material’s robustness under different conditions. Finally, the Laser Particle Size Analyzer is used to measure the size distribution of the polymer particles, which is critical for determining the uniformity and efficiency of the imprinting process. The six characterization methods discussed in this paper provide a comprehensive understanding of MIP, and it is hoped that in the future, more optimized design solutions will emerge and their applications in various fields will be enhanced.

Synthesis and Solid Phase Extraction Performance Study of NNAL-specific Molecularly Imprinted Polymers Using Dummy Templates

Dummy molecularly imprinted polymers （DMIPs） for 4-（methylnitrosamino）-1-（3-pyridyl）-1-butanol （NNAL） were produced using three structural analogues as dummy template molecules. The chosen analogues were 4-（acetymethylamino）-1-（3-pyridyl）-butanol, 4- （methylamino）-1-（3-pyridyl）-1-butanol, and 1-（3-pyridyl）-1,4,-butanediol. The molecular recognition characteristics of the produced polymers were evaluated by X-ray photoelec- tron spectroscopy （XPS） and Fourier transform infrared spectroscopy （FT-IR）. Interactions between NNAL and methacrylic acid should be cooperative hydrogen bonds while the ni- trogen atom of the pyridine ring and the oxygen atom of the nitroso group in NNAL are two of the hydrogen-bond acceptors. It was further demonstrated that DMIP synthesized by 4-（acetymethylamino）-1-（3-pyridyl）-butanol had the best binding performance by XPS and FT-IR. Then dummy molecularly imprinted solid phase extraction （DMISPE） was developed for the determination of the analyte using the hit polymer as the sorbing material. Under optimal conditions, the recovery of NNAL dissolved in standard solution reached 93%. And the investigated polymer exhibited much higher binding of NNAL when nicotine was acted as the competitive molecule. Also the proposed method was applied to the measurement of NNAL spiked in blank urine samples with recoveries ranging from 87.2% to 101.2%.

Preparation of high selective molecularly imprinted polymers for tetracycline by precipitation polymerization

High selective molecularly imprinted polymers （MIPs） for tetracycline have been prepared by precipitation polymerization. Effects of monomer and solvent, the ratio of monomer and template and the characterization of the polymer were investigated by frontal chromatography and selectivity experiment. The results clearly indicated that the polymer, which had the highest molecular recognition abilities for tetracycline antibiotics, had been received.

Molecularly Imprinted Polymers for Selective Extraction of Crystal Violet from Natural Seawater coupled with HighPerformance Liquid Chromatographic Determination

Molecularly imprinted polymers （MIPs） were prepared by the bulk polymerization using crystal violet as the template molecule, and the methacrylic acid and ethylene glycol dimetheacrylate as functional monomer and cross-linker, respectively. Sys- tematic investigations of synthetic conditions were conducted. The surface morphology and recognition mechanism of the obtained polymers were studied using scanning electron microscope and spectrophotometric analysis. MIPs showed high atTmity to template molecule and were successfully applied as special solid-phase extraction sorbent for selective extraction of crystal violet from natural seawater. An off-line molecularly imprinted solid-phase extraction （MISPE） method followed by high-performance liquid chroma- tography with diodearray detection for the analysis of crystal violet was also established. MISPE columns have good recoveries for crystal violet standard solutions and good linearity was obtained over the concentration range of 0-200 ~tg L-1 （R2 〉 0.99）. Finally, two natural seawater samples were investigated. The recoveries of spiked seawater on the MISPE columns were from 44.47% to 62.34%, the relative standard deviation （n=3） being in the range of 2.89%-5.96%.

Fluorescent competitive assay for melamine using dummy molecularly imprinted polymers as antibody mimics

A fluorescent competitive assay for melamine was first developed utilizing dummy molecularly imprinted polymers（DMIPs） as artificial antibodies. This method is based on the competition between fluorescent substances and the unlabeled analyte for binding sites in synthesized DMIPs and the decreased binding of fluorescent substances to DMIPs due to increased concentrations of melamine in the solutions. DMIPs for melamine were synthesized under a hot water bath in the presence of the initiator azobisisobutyronitrile（AIBN） using 2,4-diamino-6-methyl-1,3,5-triazine（DAMT） as a dummy template, methacrylic acid（MAA） as a functional monomer, and ethylene glycol dimethacrylate（EGDMA） as a crosslinking agent. The adsorption capacity and selectivity of DMIPs for melamine were evaluated by the isothermal adsorption curve and Scatchard analysis. The evaluation results showed that the synthesized DMIPs had specific recognition sites for melamine and the maximum adsorption amount was 1 066.33 μg g^（-1）. Later, 5-（4,6-d ichlorotriazinyl） amino fluorescein（DTAF） with a triazine ring, which s lightly resembles m elamine, w as selected as the fluorescent substance. The fluorescent competitive assay using DMIPs as t he antibody mimics was finally established by selecting and optimizing the reaction solvents, DMIPs amount, DTAF concentration, and incubation time. The optimal detection system showed a linear response w ithin range of 0.05-40 mg L^（-1） and the limit of detection（LOD） was 1.23 μg L^（-1）. It was successfully applied to the detection of melamine in spiked milk samples wi th satisfactory recoveries（71.9 to 86.3%）. According to the comparative analysis, the result of optimized fluorescent competitive assay re vealed excellent agreement with the HPLC-MS/MS result for melamine.

Preparation of Magnetic Molecularly Imprinted Polymers for Selective Isolation and Determination of Kaempferol and Protoapigenone in Macrothelypteris torresiana

Novel uniform-sized magnetic molecularly imprinted polymers （MMIPs） were synthe- sized for selective recognition of active antitumor ingredients of kaempferol （KMF） and protoapi- genone （PA） in Macrothelypteris torresiana （M. torresiana） by surface molecular imprinting tech- nique in this study. Super paramagnetic core-sheU nanoparticles （γ-MPS-SiO2@Fe3O4） were used as seeds, KMF as template molecule, acrylamide （AM） as functional monomer, and N, N＇-methylene bisacrylamide （BisAM） as cross-linker. The prepared MMIPs were characterized by X-ray diffraction （XRD）, Fourier transform infrared spectrum fiT/R）, transmission electron microscopy （TEM） and thermo-gravimetric analysis （TGA）, respectively. The recognition capacity of MMIPs was 2.436 times of non-imprinted polymers. The adsorption results based on kinetics and isotherm analysis were in accordance with the pseudo-second-order model （R2=0.9980） and the Langmuir adsorption model （R2=0.9944）. The value of E （6.742 kJ/mol） calculated from the Dubinin-Radushkevich isotherm model suggested that the physical adsorption via hydrogen-bonding might be predominant. The Scatchard plot showed a single line （R2=0.9172） and demonstrated the homogeneous recognition sites on MMIPs for KMF. The magnetic solid phase extraction （MSPE） based on MMIPs as sorbent was established for fast and selective enrichment of KMF and its structural analogue PA from the crude extract of M. torresiana and then KMF and PA were detected by HPLC-UV. The established method showed good performance and satisfactory results for real sample analysis. It also showed the feasi- bility of MMIPs for selective recognition of active structural analogues from complex herbal extracts.

Molecularly Imprinted Polymers on Chloromethyl Polystyrene Resin Prepared via RAFT Polymerization

Surface molecularly imprinted polymers （SMIP） was prepared via the reversible addition-fragmentation chain transfer （RAFT） polymerization on the chloromethyl polystyrene resin （CPR） in the presence of the template D-phenylalanine. The structure of SMIP was characterized by FTIR and SEM. The adsorption behavior of D-phenylalanine of SMIP was preliminarily investigated.

Application of Molecularly Imprinted Polymers for the Analysis of Pesticide Residues in Food—A Highly Selective and Innovative Approach

The increasing application of pesticides for agricultural purposes involves serious risk to the environment and human health due to either exposure or through residues in food and drinking water. Since food safety is of mandatory importance there is a growing interest on the development of selective, simple, rapid, cost-effective and reliable analytical methodologies in order to ensure that pesticides residues should not be found at levels above the established maximum pesticide residue limits (MRLs). In recent years, a new methodology based on the development of molecularly imprinting polymers (MIPs) allows not only pre-concentration and cleaning of the sample but also selective extraction of the target analyte, which is crucial, particularly when the sample is complex and impurities can interfere with quantification. The scope of this review is to provide a general overview on MIPs field, with emphasis on MIP preparation and its use as sorbents for solid-phase extraction. This paper will be focused on the review of the current state of the art in the use of MIPs as selective materials in molecularly imprinted solid-phase extraction (MISPE) for the analysis of pesticide residues from food matrices. A review of preparation and application of MIPs in food matrices, will also be discussed.

STUDY ON THE NON-COVALENT INTERACTION OF APIGENIN MOLECULARLY IMPRINTED POLYMERS BY SPECTROMETRY

The non-covalent interaction between apigenin (API) and different functional monomers (α-methylacrylic acid (MAA), acrylamide (AM), 2-vinylpyridine (2-Vpy) and combined functional monomers (AM/2-Vpy)) was determined by UV spectrometry, and a series of apigenin molecularly imprinted polymers (API-MIPs) was synthesized with different functional monomers through molecular imprinting technology. The relationship between the non-covalent interaction of template/functional monomer and absorption of MIPs also was studied. The results showed that the order of the strength of the non-covalent interaction between API and different functional monomers in tetrahydrofuran (THF) is as follows: 2-Vpy> AM/2-Vpy>AM>MAA, which is positive correlation to the absorption capability of corresponding MIPs, and 2-Vpy is the optimum functional monomer among the used monomer for preparing API- MIPs.

Preparation of High Selective Molecularly Imprinted Polymers for (S)-4-Phenyl-2-oxazolidinone

（S）-4-Phenyl-2-oxazolidinone imprinted polymers were prepared by using methacrylic acid （MAA） as the functional monomer, and divinylbenzene （DVB） as crosslinker. The factors, which influence the selectivity of the polymers were explored. Effective separation was observed for racemic 4-phenyl-2-oxazolidinone in mobile phase of acetonitrile. The investigation of mobile phase suggested that the hydrogen bonds between template and functional monomer was a primary factor in chiral recognition, while the preparation of polymers implied that the л-л stacking interaction between template and crosslinker played a role in imprinting procedure.

RECENT ADVANCES IN THE PREPARATION OF MOLECULARLY IMPRINTED POLYMERS VIA CONTROLLED RADICAL POLYMERIZATION TECHNIQUES

Molecular imprinting technique is a simple and efficient method for the preparation of polymer materials (i.e., molecularly imprinted polymers, MIPs) with tailor-made recognition sites for certain target molecules. The resulting MIPs have proven to be versatile synthetic receptors due to their high specific recognition ability, favorable mechanical, thermal and chemical stability, and ease of preparation. Recent years have witnessed significant progress in the synthesis and applications of MIPs. This review focus on the recent developments and advances in the preparation of MIPs via various controlled radical polymerization techniques.

Recent advances in magnetic molecularly imprinted polymers and their application in the food safety analysis

Food safety is a worldwide concern and is directly related to human health.Therefore,convenient,effective,and economical methods and technologies for food safety analysis have been developed continuously.Magnetic molecularly imprinted polymers(MMIPs)have gained extensive attention in recent years,as they have high selectivity,high adsorption capacity,and are easy to isolate from food samples.Recently,advanced strategies for the synthesis of MMIPs have been proposed to solve problems of template leakage and non-specific adsorption,and to increase the biocompatibility,adsorption rate,as well as adsorption capacity of the imprinted materials.In this review,we focus on new attempts at modification of magnetic core and MMIPs’surfaces,and the selection of template,functional monomer,cross-linker as well as porogen.Studies are summarized that used advanced MMIPs for the recognition and adsorption of pesticide residues,veterinary drug residues,mycotoxins,contaminants,and adulterations in foodstuffs over the last 5 years.Finally,some still existing challenges and future prospects to further promote MMIPs properties are also discussed.

A novel surface molecularly imprinted polymer as the solid-phase extraction adsorbent for the selective determination of ampicillin sodium in milk and blood samples

Surface molecularly imprinted polymers （SMIPs） for selective adsorption of ampicillin sodium were synthesized using surface molecular imprinting technique with silica gel as a support. The physical and morphological characteristics of the polymers were investigated by scanning electron microscope （SEM）, Fourier transform infrared spectroscopy （FT-IR）, thermogravimetric analysis （TGA）, elemental analysis and nitrogen adsorption-desorption test. The obtained results showed that the SMIPs displayed great adsorption capacity （13.5 lag/mg）, high recognition ability （the imprinted factor is 3.2） and good binding kinetics for ampicillin sodium. Finally, as solid phase extraction adsorbents, the SMIPs coupled with HPLC method were validated and applied for the enrichment, purification and determination of anapicillin sodium in real milk and blood samples. The averages of spiked accuracy ranged from 92.1% to 107.6%. The relative standard deviations of intra- and inter-day precisions were less than 4.6%. This study provides a new and promising method for enriching, extracting and determining ampicillin sodium in complex biological samples.

Molecularly imprinted polymer based on upconversion nanoparticles for highly selective and sensitive determination of Ochratoxin A

A novel molecularly imprinted polymer (MIP) based on upconversion nanoparticles (UCNPs) was successfully synthesized for determination of Ochratoxin A (OTA). The MIP was developed on the silica-coated UCNPs using N-(1-hydroxy-2-naphthoyl amido)-(L)-phenylalanine (HNA-Phe) as the alternative template. The final composite combined the advantages of the high selectivity of MIP with the high fluorescence intensity of UCNPs which was selective and sensitive to OTA. Under the optimal condition, the fluorescence intensity of UCNPs@SiO2@MIP decreases linearly when the concentration of OTA increases from 0.05 to 1.0 mg/L. The detection limit of OTA with the method was 0.031 mg/L. At three spiked concentration levels (50, 100 and 200 μg/kg), the recovery ranges of OTA in corn, rice and feed are 88.0%–91.6%, 80.2%–91.6% and 89.2%–90.4%, respectively.

The Recent Advances of Fluorescent Sensors Based on Molecularly Imprinted Fluorescent Nanoparticles for Pharmaceutical Analysis

Fluorescent nanoparticles have good chemical stability and photostability,controllable optical properties and larger stokes shift.In light of their designability and functionability,the fluorescent nanoparticles are widely used as the fluorescent probes for diverse applications.To enhance the sensitivity and selectivity,the combination of the fluorescent nanoparticles with the molecularly imprinted polymer,i.e.molecularly imprinted fluorescent nanoparticles(MIFN),was an effective way.The sensor based on MIFN(the MIFN sensor)could be more compatible with the complex sample matrix,which was especially widely adopted in medical and biological analysis.In this mini-review,the construction method,detective mechanism and types of MIFN sensors are elaborated.The current applications of MIFN sensors in pharmaceutical analysis,including pesticides/herbicide,veterinary drugs/drugs residues and human related proteins,are highlighted based on the literature in the recent three years.Finally,the research prospect and development trend of the MIFN sensor are forecasted.

Synthesis of Molecularly Imprinted Polymer Particles by Suspension Polymerization in Silicon Oil

Molecularly imprinted polymers using 2,4-dichlorophenoxyacetic acid （2,4-D） as templates were prepared by suspension polymerization in silicon oil. The polymer particles exhibited regular shape in the micro-scale range. The adsorbing experiments indicated that the imprinted polymer particles possessed higher affinity to 2,4-D than the non-imprinted polymer particles.

Metsulfuron-methyl Molecularly Imprinted Stir Bar Sorptive Extraction Coupled with High Performance Liquid Chromatography for Trace Sulfonylurea Herbicides Analysis in Complex Samples

Metsulfuron-methyl molecularly imprinted polymer（MIP）-coated stir bar was prepared for sorptive extraction of sulfonylurea herbicides in complex samples.The MIP-coating was about 21.3 μm thickness with the relative standard deviation（RSD） of 4.4%（n=10）.It was homogeneous and porous with good thermal stability and chemical stability.The extraction capability of the MIP-coating was 2.8 times over that of the non-imprinted polymer（NIP）-coating in hexane.The MIP-coating exhibited selective adsorption ability to the template and its analogues.The extraction conditions,including extraction solvent,desorption solvent,extraction time,desorption time and stirring speed,were optimized.A method for the determination of six sulfonylurea herbicides by MIP-coated stir bar sorptive extraction coupled with high performance liquid chromatography（HPLC） was developed.The linear range was 10―200 μg/L and the detection limits were within a range of 2.0―3.3 μg/L.It was also applied to the analysis of sulfonylurea herbicides in spiked river water,soil and rice samples.

Capillary Electrochromatography of Molecularly Imprinted Monolithic Column Using p-Hydroxybenzoic Acid as Templates

Moleculary imprinted polymers using p-hydroxybenzoic acid as templates wassynthesized by an in situ polymerization reaction and rendered capillary monolithic column wasused in capillary electrochromatographic mode. Good molecular recognition was achieved for p-hydroxybenzoic acid and good resolution of isomers can be realized.

Preparation and evaluation of monolithic molecularly imprinted stationary phase for S-naproxen

An S-naproxen（S-NAP）molecularly imprinted monolithic stationary phase（MIMSP）with specific recognition for S-NAP and naproxen（NAP）was prepared by in situ technique,utilizing 4-vinylpridine（4-VP）as a function monomer,ethylene glycol dimethacrylate（EDMA）as a cross-linking agent,and low-polar solvents（toluene and dodecanol）as porogenic solvents.The selectivity of the polymers for S-NAP and NAP was evaluated by high performance liquid chromatography（HPLC）.The binding characteristics were tested by Scatchard analysis.Racemic NAP could be specifically separated to some extent.At the same time,NAP could be separated from ibuprofen under optimized conditions.Scatchard analysis showed that two classes of binding sites existed in the S-NAP-imprinted polymers,with their dissociation constants estimated to be 1.045 and 5.496 μM,respectively.The results demonstrate that S-NAP and NAP can be recognized specifically on the obtained MIMSP.

Development and Characterization of an Electrochemical Sensor for Cinchonidine Detection Based on Molecularly Imprinted Polymer with Modified Rosin as Cross-linker

Molecularly imprinted polymers（MIPs） were applied as molecular recognition elements to an electro- chemical sensor for cinchonidine（CD）. A kind of MIP was synthesized with cinchonidine as template, modified ro- sin（ethylene glycol maleic rosinate acrylate） containing the skeleton of phenanthrene rings as cross-linker and me- thylacrylic acid as functional monomer. MIP membrane was prepared on a glassy carbon electrode for the determina- tion of CD via free radical polymerization method. Electrochemical impedance spectroscopy（EIS） and cyclic vol- tammetry（CV） were used to characterize the membrane electrochemical behavior in electrode fabrication process. The experimental conditions were discussed. Under optimum conditions, it was found that the response of peak cur- rents was linear to the concentration of CD in a range of 0.013-2.26 mmol/L. The detection limit for CD is 1 μmol/L the relative standard deviation for 100 μmol/L CD is 1.34% and the incubation time is 2 min. The sensor was applied to the determination of CD in urine samples with satisfactory results.