Synthesis of molecularly imprinted polymer by precipitation polymerization for the removal of ametryn

Ametryn (AME) is a triazine herbicide which is mainly used to kill unwanted herbs in crops. Despite its importance in agriculture, the usage of AME also poses a risk to humans and the ecosystem due to its toxicity. Hence, it is important to develop a method for the effective removal of AME from various water sources which is in the form of molecular imprinting polymer (MIP). In this study, MIP of AME was synthesized via precipitation polymerization using AME as the template molecule with three different functional monomers including methacrylic acid (MAA), acrylamide (AAm) and 2-vinylpyridine (2VP). The three different synthesized polymers namely MIP (MAA), MIP (AAm) and MIP (2VP) were characterized using Fourier Infra-red spectroscopy (FTIR) and Field Emission Electron Microscopy (FESEM). Then, the batch binding study was carried out using all three MIPs in which MIP (MAA) attained the highest rebinding efficiency (93.73%) among the synthesized polymers. The Energy-Dispersive X-ray spectroscopy (EDX) analysis, Brunauer-Emmett-Teller (BET) analysis and thermogravimetric analysis (TGA) were also conducted on the selected MIP (MAA). Adsorption studies including initial concentration, pH and polymer dosage were also conducted on MIP (MAA). In this study, the highest adsorption efficiency was attained at the optimum condition of 6 ppm of AME solution at pH 7 with 0.1 g of MIP (MAA). MIP (MAA) was successfully applied to remove AME from spiked distilled water, tap water and river water samples with removal efficiencies of 95.01%, 90.24% and 88.37%, respectively.

Temperature and pH-responsive PNIPAM@PAA Nanospheres with a Core-Shell Structure for Controlled Release of Doxorubicin in Breast Cancer Treatment

Stimuli-responsive polymers have been of great interest in the fabrication of advanced drug delivery systems. In this study, a facile approach was developed to synthesize a dually temperature/pH-responsive drug delivery system with a core-shell structure to control the release of doxorubicin (DOX) at the target site. For this purpose, poly(acrylic acid) (PAA) nanospheres were first synthesized using the precipitation polymerization technique and were used as pH-responsive polymeric cores. Then, poly(N-isopropylacrylamide) (PNIPAM) with thermo-responsivity properties was coated on the outer surface of PAA cores via seed emulsion polymerization technique to render monodisperse PNIPAM-coated PAA (PNIPAM@PAA) nanospheres. The optimized PNIPAM@PAA nanospheres with an average particle size of 116.8 nm (PDI= 0.243), had a high negative surface charge (zeta potential= -47.6 mV). Then, DOX was loaded on PNIPAM@PAA nanospheres and the entrapment efficiency (EE) and drug loading (DL) capacity were measured to be 92.7% and 18.5%, respectively. The drug-loaded nanospheres exhibited a low leakage at neutral pH and physiological temperature, but drug release significantly enhanced at acidic pH (pH= 5.5), indicating the tumor-environment responsive drug release behavior of the prepared nanospheres. Also, kinetics studies showed that, the sustained release of DOX from PNIPAM@PAA nanospheres was consistent with the Fickian diffusion mechanism. Moreover, the anticancer efficacy of DOX-loaded nanospheres was evaluated in vitro against MCF-7 breast cancer cells. The obtained results revealed that, the incorporation of DOX into PNIPAM@PAA nanospheres increases its cytotoxicity against cancer cells compared to the free DOX. Our results suggest that, PNIPAM@PAA nanospheres can be considered as a promising vector to release anticancer drugs with dual-stimuli responsivity to pH and temperature.

Template-assisted synthesis of molecularly imprinted polymers for the removal of methyl red from aqueous media

This study entails the synthesis of molecularly imprinted polymers (MIPs) with good selectivity coefficients for azo dye as a potential sorbent material to extract azo dye from polluted aqueous media. A series of MIPs for methyl red (MR) as a template, were synthesized by changing the molar ratio of functional monomers, via precipitation polymerization format of non-covalent approach. Water-soluble functional monomer; acrylic acid (AA) was used to weave the frame work of polymers while ethylene glycol dimethacrylate (EGDMA) was utilized as crosslinking monomer. The impact of different experimental parameters, such as mole ratio of monomer (functional) to crosslinking monomer on the molecular recognition was investigated. The highly efficient and selective MR-MIP was used for the removal of spiked MR dye from different water samples. The selected imprinted polymer, MR1-MIP was able to selectively remove the MR molecules from aqueous media. A significant amount of dye was removed by MR1-MIP from the river water samples with a high degree of removal efficiency i.e. 92.25%. The imprinting factor of 3.75 for MR1-MIP indicated that the high selectivity in terms of adsorption for MR. A minimum loss of only ~ 3.35% in the removal efficiency within ten sequential cycles of adsorption-desorption study evidenced that MR-MIPs could be used as the most cost effective and best sorbent for the removal of MR from polluted water. Furthermore, the structural properties of MR-MIPs were characterized by FTIR and EDX, whereas TGA, SEM and BET were used to describe the thermal, morphological and surface structures of the particles, respectively.

Superhydrophobic fluorinated microspheres for fluorous affinity chromatography

Fluorous affinity chromatography has received growing attention in separation and purification of fluoro compounds, but the wettability of the fluorinated stationary phases is seldom noticed. Here, we construct a series of micro-sized fluorine-containing microspheres by solvothermal precipitation polymerization. The fluorinated microspheres could be obtained with narrow size distribution at even high monomer loading of 15 wt%. Through alternating fluoro monomer, both the particle size and the wettability of the microsphere array could be tuned. Among them, the poly(divinylbenzene -dodecafluoroheptyl methacrylate), P(DVB-DFHMA), microsphere (6.1 μm) arrays displays superhydrophobicity with 153.2° water contact angle. The P(DVB-DFHMA) fluorinated microspheres (7.58% fluorine content) can be packed into steel-less columns as stationary phase for high-performance liquid chromatography. The retention mechanism of the fluorinated column is proven to be the specific fluorine-fluorine interaction. Compared to the commercial C18 silica column, the fluorinated column can completely separate fluorine-containing compounds under high water content mobile phase, including small fluoro molecules and fluoro macromolecules, at much lower back pressure by fluorous affinity.

Facile "one-pot" preparation of phosphonate functional polythiophene based microsphere via Friedel-Crafts reaction for selective enrichment of phosphopeptides from milk

A novel kind of phosphonate functionalized polythiophene microsphere was designed and fabricated via Friedel-Crafts reaction. Diethyl (thiophen-2-ylmethyl) phosphonate (DTYP) and thiophene were co-polymerized by Fe (III) catalysis, without any surfactant, stabilizer and initiator. Functional phosphonate group was directly introduced into the microsphere without redundant modification steps. The adsorption amount of the as-synthesized microsphere, Ti-poly(Th-co-DTYP), was as high as 66.7 mg/g, which was higher than that of commercial Ti⁴⁺-IMAC microsphere (49.7 mg/g). The microsphere was explored on the specific capture of phosphopeptides from either tryptic digests of milk or HeLa cell protein. As a result, 88 of unique phosphopeptides mapping to 21 phosphoproteins were identified from 150 μg of milk tryptic digest after enrichment, and a total of 2534 unique phosphopeptides mapping to 1087 phosphoproteins was identified from HeLa cell. It is expected that such a robust and facile approach will be explored in other functional microspheres to be commercialized in the future.

Synthesis of uniform submicron poly(lactic acid)-based particles/capsules by radical precipitation polymerization

Poly(l-lactic acid) (PLLA) is a well-known biopolymer, usually synthesized via step-growth or ring-opening polymerization from lactic acid or a lactide monomer, respectively. PLLA microspherical particles are produced by dispersion polymerization with a ring-opening lactide monomer using a particular copolymer chain as a stabilizer. This is not easy to achieve when dehydration is needed. Here, a robust and simple synthesis of a nearly monodisperse, submicron PLLA-based particle/capsule was proposed via radical precipitation polymerization without the use of surfactant. A commercial PLLA was first glycolyzed with ethylene glycol to obtain a low molecular weight glycolyzed PLLA (GPLLA). Then, the GPLLA was copolymerized with methacrylic acid and ethylene glycol dimethacrylate monomers using a benzoyl peroxide initiator. Active sites on the GPLLA backbone were generated by hydrogen abstraction of benzoyloxy radicals that further copolymerized before self-assembly to form the polymer particles. Uniform particle size of about 580 nm with a low polydispersity index (PDI) of 0.012 was obtained. This method was also implemented to produce nearly monodisperse capsules containing linalool. The particle size of PLLA-based capsules was about 280 nm with narrow particle size distribution (PDI of 0.120). The PLLA-based capsules effectively inhibited microbial growth of Staphylococcus aureus, Escherichia coli and Candida albicans and were not toxic to human cells.

Molecularly Imprinted Polymer for a Smart Dispersive Micro-Solid Phase Extraction Technique for Assessing Trace Level Aflatoxins in Cultured Fish

Molecularly imprinted technology (MIT) consists of preparing materials exhibiting specific recognition cavities to selective mimic the target analytes. The prepared materials promote selective interactions with the targets and avoid interactions of concomitants from complex food, biological, clinical, and environmental matrices. This chapter provides information on a recent development of a vortex-assisted micro-solid phase extraction using a molecularly imprinted polymer (MIP) as an adsorbent for aflatoxins (AFs) determination in cultured fish. MIP particles were synthesized by precipitation polymerization using 5,7-dimethoxycoumarin as a dummy template, methacrylic acid as a functional monomer, divinylbenzene as a cross-linker, and 2,2-azobisisobutyronitrile as an initiator. Polymerization following the precipitation method guarantees homogeneous particle size distribution and the integrity of the imprinted cavities. The MIP microparticles were found to have 5 μm in diameter and a spherical shape. Important parameters such as sample extract pH, adsorption stirring speed and time, desorption stirring speed and time, elution solvent composition and volume, and polymer mass, were fully optimized. The pre-concentration method allows therefore the assessment of four major AFs (B1, B2, G1, and G2) present in cultured fish at very low levels, with pre-concentration factors from 15 to 50 depending of the volume of extract used for performing the dispersive micro-solid phase extraction (D-μ-SPE).

Fluorescent linear polyurea based on toluene diisocyanate: Easy preparation, broad emission and potential applications

In contrast to conventional fluorescent polymers featured by large conjugation structures, a new class of fluorescent polymers without above conjugations are gaining constant interest owing to their significant academic importance and promising applications in diverse fields. These unconventional fluorescent polymers are in general composed of heteroatoms (e.g. N, O, P, and S) under different forms. Here we report our recent study on polyurea, prepared by a very simple one step precipitation polymerization of toluene diisocyanate in a binary solvent of water-acetone. This polyurea, basically consisting of phenyl ring and urea group, shows fluorescent emission in a broad concentration range, from very low (10-5 mg/mL) to its solubility limit (50 mg/mL), and in a wide range of emission wavelength from UV to visible regions of up to 500 nm under varied excitation wavelength. The emission behaviors were fully studied under different concentrations and excitations. It was concluded that the emission in UV region was intrinsic due to the conjugation between the phenyl and the adjacent urea unit; while the emission in visible region, strongly excitation dependent, was caused by the cluster formation of the molecular chains, in accordance with the cluster-triggered-emission (CTE) mechanism. The formation of the cluster was tested through dynamic light scattering, FTIR and UV absorbance. Tested in presence of different metal ions, Fe3+ demonstrated a quenching effect with high selectivity. Based on this study, different paper-based sensors were designed to detect Fe3+, H2O2 in bioanalysis and for data encryption. This work provides a simple way to prepare a polyurea, a novel type of unconventional fluorescent polymer, with high emission performance distinct from its known analogues.

Molecularly Imprinted Polymer Thin-Film Electrochemical Sensors

Preparation of potentiometric and amperometric sensors with thin-film membranes based on molecularly imprinted polymers (MIP) is described. Spherical MIP microparticles with diameter below 1 μm are suitable for incorporation into the sensing membrane by the deposition of a conducting polymer on the electrode surface. This is achieved through electropolymerization from the suspension of MIP particles in monomer solution. Procedures of the synthesis of MIP particles, preparation of sensing membranes, and analytical application of potentiometric and amperometric sensors with MIP-modified membranes are described.

Antitumor activity of a molecularly imprinted nanopreparation of 5-flurouracil against Ehrlich's carcinoma solid tumors grown in mice: Comparison to free 5-flurouracil

Recently, nanotechnology has received great attention in war against cancer. The present study investigated the antitumor efficacy of molecularly imprinted nanopreparation of 5-fluorouracil (nano-5-FU) against Ehrlich ascites carcinoma (EAC) solid tumors grown in mice. Tumor cells were transplanted into female albino mice. Mice were allocated into 5 groups; Group 1: control EAC bearing mice. Groups 2&3: EAC-bearing mice treated orally with 5-FU (5 and 10 mg/kg) twice weekly. Groups 4&5: EAC bearing mice treated with nano-5-FU (5 and 10 mg/kg) twice weekly. Treatment with nano-5-FU showed higher antitumor effect compared to free 5-FU as indicated by enhanced apoptosis and reduction in tumor weight. Additionally, lower number of mitotic figures and greater area for necrosis were observed in the tumor specimens alongside with a decline in the number of intratumoral proliferating nuclei in comparison to free 5-FU. Furthermore, the results showed a significant down-regulation in tumoral expression of caspase-3 and vascular endothelial growth factor. Together, these results further support the potential of using nanotechnology to enhance anticancer efficacy of 5-FU.

Structurally stable N-t-butylacrylamide hydrogel particles for the capture of peptides

Hydrogel particles have proven to be powerful tools for the capture and concentration of low abundance, low molecular weight peptides and proteins from complex biofluids, such as plasma. The primary means of recovering and washing the particles following harvesting is through centrifugation, which can be a very time-consuming process depending on harvest conditions. To improve the process of particle recovery, washing, and elution we have developed new particle formulations: incorporating N-t-butylacrylamide (tBA) in the polymer backbone with monomers bearing more acidic functional groups and higher degrees of cross-linking. These particle formulations produce a stable architecture that does not significantly respond to changes in environmental conditions, such as pH and temperature. These two new formulations impart structural stability to the particle, control swelling, and improve pelleting through centrifugation, even at high pH values. These structurally stable microparticles yield improved particle recovery while maintaining the peptide capture properties of the particle.

Preparation of Molecularly Imprinted Microspheres by Precipitation Polymerization

Molecularly imprinted polymers (MIPs) gained an expansively growing interest in the past few decades. After an initial, explorative period of preparing MIPs exclusively with bulk polymerization, new polymer synthesis routes have been adapted to overcome the drawbacks of the traditional method. Among these the most appealing is precipitation polymerization that results in nano- and microspheres with narrow size distribution and makes the production of MIPs more straightforward. Here, we describe a precipitation polymerization protocol for a common small molecule template, propranolol that is carried out in the conventional way, in dilute monomer solution. Moreover, a modified precipitation polymerization protocol from concentrated monomer solution is presented for a diclofenac imprinted polymer which makes the synthesis even more versatile and circumvents the disadvantages of the dilute solution conditions.

Synthesis, recognition characteristics and properties of l-3-n-butylphthalide molecularly imprinted polymers as sorbent for solid-phase extraction through precipitation polymerization

L-3-n-butylphthalide molecularly imprinted polymers (MIPs) were synthesized using l-3-n-butylphthalide as template molecule, acrylamide as functional monomer, ethylene glycol dimethacrylate as cross-linking agent, and acetone as the porogenic solvent through precipitation polymerization. The non-imprinted polymers (NIPs) were prepared with the same procedure, but with the absence of template molecule. The optimum preparation conditions of the MIPs such as the functional monomer, the porogenic solvent, the molar ratio of the template to the functional monomer and the molar ratio of the template to the cross-linker were investigated in detail. Prior to the polymerization, the molecular simulation with the computer-aided design was used to help choose a suitable polymerization porogen for the molecularly imprinted pre-assembled system and study the interactions between l-NBP and the functional monomers. The synthesized polymers were characterized with FTIR and SEM to observe their structures as well as the morphologies, and their adsorption properties were respectively evaluated by static and dynamic adsorption as well as selectivity experiments. Scatchard analyses revealed that there were high and low affinity sites formed in the MIPs, which elucidated good affinity to l-NBP in the ethanol system. The adsorption capacity of the MIPs for l-NBP was 3.561 mg g(-1), with an imprinting factor (α) of 2.321 when compared with that of the NIPs. Scatchard analysis illustrated that the binding sites with affinity for l-3-n-butylphthalide molecules were formed in the prepared MIPs.

Selective extraction of dimethoate from cucumber samples by use of molecularly imprinted microspheres

Molecularly imprinted polymers for dimethoate recognition were synthesized by the precipitation polymerization technique using methyl methacrylate (MMA) as the functional monomer and ethylene glycol dimethacrylate (EGDMA) as the cross-linker. The morphology, adsorption and recognition properties were investigated by scanning electron microscopy (SEM), static adsorption test, and competitive adsorption test. To obtain the best selectivity and binding performance, the synthesis and adsorption conditions of MIPs were optimized through single factor experiments. Under the optimized conditions, the resultant polymers exhibited uniform size, satisfactory binding capacity and significant selectivity. Furthermore, the imprinted polymers were successfully applied as a specific solid-phase extractants combined with high performance liquid chromatography (HPLC) for determination of dimethoate residues in the cucumber samples. The average recoveries of three spiked samples ranged from 78.5% to 87.9% with the relative standard deviations (RSDs) less than 4.4% and the limit of detection (LOD) obtained for dimethoate as low as 2.3 μg/mL.

Preparation and study of tramadol imprinted micro-and nanoparticles by precipitation polymerization: microwave irradiation and conventional heating method

In the present work a series of tramadole imprinted micro- and nanoparticles were prepared and study their recognition properties. Methacrylic acid (MAA), as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a cross-linker and different solvents (chloroform, toluene and acetonitrile (ACN)) were used for the preparation of molecularly imprinted polymers (MIPs) and non-imprinted polymers (NIPs). Several factors such as template/monomer molar ratio, volume of polymerization solvent, total monomers/solvent volume ratio, polymerization condition (heating or microwave irradiation) were also investigated. Particle size of the polymers, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), rebinding, selectivity tests and release study were applied for evaluation of the polymers. The optimized polymers with smaller particle size and superior binding properties were obtained in acetonitrile under heating method. MIPA4 with a size of 42.6 nm and a binding factor (BF) of 6.79 was selected for selectivity and release tests. The polymerization was not successful in acetonitrile and toluene under microwave irradiation. The MIPA4 could selectively adsorb tramadol, compared to imipramine, naltrexone and gabapentin. The data showed that tramadol release from MIPA4 was significantly slower than that of its non-imprinted polymer. Therefore, MIP nanoparticles with high selectivity, binding capacity and ability to control tramadol release could be obtained in precipitation polymerization with optimized condition.

Synthesis of tetracycline-imprinted polymer microspheres by reversible addition-fragmentation chain-transfer precipitation polymerization using polyethylene glycol as a coporogen

Tetracycline (TC)-imprinted microspheres have been synthesized by reversible addition-fragmentation chain-transfer precipitation polymerization using PEG as a coporogen. In the synthesis, methacrylic acid and ethylene dimethacrylate were used as the functional monomer and cross-linker, respectively. 2,2'-Azobisisobutyronitrile was the initiator, and cumyl dithiobenzoate was the chain-transfer reagent. Although monodispersed microspheres were obtained using acetonitrile as porogen, the particles cannot be used in the column extraction because of the high backpressure. To increase the porosity of the material, PEG was introduced as a coporogen. The influence of the molecular weight and concentration of PEG on the morphology, binding affinity, and porosity of the molecularly imprinted polymers (MIPs) have been studied. The results demonstrated that PEG as a macroporogen increased the porosity of the polymers. Meanwhile, the column backpressure was reduced using the MIPs with higher porosity. The binding affinity of the MIPs was increased when a low concentration of PEG was employed, while it was decreased when the ratio of PEG 12,000/monomers was >0.8%. Under the optimized conditions, TC-imprinted microspheres with good selectivity and size uniformity have been obtained, which facilitates its application in the column extraction for TC determinations.

Effect of thiol-containing monomer on the preparation of temperature-sensitive hydrogel microspheres

The main objective of this study is to prepare, thermally, sensitive microgel particles bearing thiol groups via precipitation polymerization of N-isopropylacrylamide (NIPAM), methylenebisacrylamide (MBA) and vinylbenzylisothiouronium chloride (VBIC) using 2-2′-azobis(2-amidinopropane)-dihydrochloride (V50) as initiator. The influence of various parameters has been investigated as a systematic study to point out the role of each reactant on polymerization conversion, and consequently, on particles and water-soluble polymer formation. The final microgel particles were characterized with respect to particle size and swelling ability. The aim of this paper is to complete our first short communication; Macromolecular symposia, 2000. 150: p. 283–290.