Fluorescent Functional Monomer Research Articles

Synthesis of highly selective molecularly imprinted nanoparticles by a solid-phase imprinting strategy for fluorescence turn-on recognition of phospholipid

Molecularly imprinted polymers (MIPs) are artificial receptors with template tailored recognition sites complementary to the targets. The versatility of this molecular imprinting technique has been hampered by the lack of practical synthetic procedures to prepare highly selective MIP nanoparticles targeting phospholipids, which are challenging to be imprinted due to their amphiphilic structure. Here, a novel sedimentation-based solid-phase imprinting strategy is introduced relying on polymerization in the presence of template-modified silica nanospheres (SNs). To demonstrate this concept, the sphingosine-1-phosphate receptor agonist fingolimod phosphate (FP) was coupled to SNs which were dispersed in the prepolymerization medium consisting of the fluorescent functional monomer 1,8-bis(N-vinylimidazol-N′-methyl)anthracene bromide and the crosslinking monomer ethyleneglycol dimethacrylate. High dilution polymerization of the dispersion under agitation followed by simple sedimentation-based separation of the SN template resulted in the isolation of surface imprinted fluorescent MIP nanoparticles (FMIP NPs) in a high yield (17 %). The FMIP NPs displayed fluorescence enhancement in response to the template with a high imprinting factor (IF=9) under the experimental conditions and good specificity, and could recognize FP in human serum with recoveries of 68–74 %. Moreover, the template-modified SNs could be recycled for reuse. Such molecular imprinting strategy opens a new approach to produce highly selective artificial receptors targeting phospholipids.

Influence of the synthesis parameters on the efficiency of fluorescent ion-imprinted polymers for lead detection

New fluorescent ion-imprinted polymers (IIPs) specific for Pb(II) detection were synthesized by precipitation polymerization. The fluorescent activity of the IIPs was provided by a fluorescent functional monomer, ANQ-ST, based on the chelating 5-amino-8-hydroxyquinoline moiety coupled to anthracene and a styrenic group. Various synthesis parameters were tested: metal/functional monomer ratio, polymerization solvent and crosslinker (ethyleneglycol dimethacrylate, EGDMA, or divinylbenzene, DVB). The characterization of the different IIPs was carried out by solid-state 13C NMR spectroscopy, to analyse the structure of the polymers and to attest the integration of the ANQ-ST in the polymer matrix, and by scanning electron microscopy and nitrogen adsorption/desorption experiments, to study the morphology of the prepared materials. After characterization, the IIPs and their corresponding non-imprinted polymer (NIPs) were subjected to various fluorescence studies, in order to conclude on the influence of the synthesis parameters onto the polymer properties. The results demonstrated that the IIP synthesized with a metal/functional monomer ratio of 0.42 in DMSO/MeOH (1:1, v/v) and using EGDMA as a crosslinker was very sensitive to the presence of Pb(II) ions and almost not to other tested ions (Ag(I), Na(I), Ca(II), Cd(II), Co(II), Cu(II) and Zn(II)), even introduced in high excess. Calibration curves were performed in various matrices: ultra-pure water, buffered water at pH 7.0 and 8.1, seawater, tap water. They highlighted the low impact of the tested matrices onto the detection and allowed to determine a limit of detection of 2.4 μg/L and a linear range of 8.0–50 μg/L. Finally, the very good recovery obtained in natural samples emphasized the potential for the synthesized IIP to detect Pb(II) in natural waters.

Molecularly imprinted polydopamine coated CdTe@SiO2 as a ratiometric fluorescent probe for ultrafast and visual p-nitrophenol monitoring

Molecular imprinted ratiometric fluorescent analysis method has been a popular method for the quantitative and qualitative tests of target analysis yet encounters low detection efficiency caused by the deep embedment and uneven distribution of fluorescent monomers, even the embedding rate of fluorescent monomer directly affects the visual detection effect. Herein, the ratiometric fluorescent molecularly imprinted polymers (F-PDA/CdTe QDs@SiO2@MIPs) based fluorescent polydopamine (F-PDA) and CdTe quantum dots (CdTe QDs) was successfully synthesized to detect p-nitrophenol (p-NP) selectively and visually. F-PDA was firstly used in the synthesis of ratiometric fluorescent molecularly imprinted polymers to serve as both fluorescent monomer and functional monomer, which greatly shorten the detection time while reducing the fluorescence loss caused by polymer coating. The test results showed that the p-NP quenched the fluorescent of F-PDA via electron transfer. Meanwhile, F-PDA/CdTe QDs@SiO2@MIPs enabled to visually detect a low detection limit of p-NP (56.68 nM) within 2.0 min by naked eyes. The detection time was as fast as quantum dots detect targets directly and the detection limit was well below the standard concentration of p-NP in drinking water. Finally, the F-PDA/CdTe QDs@SiO2@MIPs realize the detection of p-NP in the drinking and wastewater respectively.

Highly efficient and selective supramolecular hydrogel sensor based on rhodamine 6G derivatives

A mercury ion sensitive fluorescent functional monomer was synthesized based on rhodamine 6G, and two highly-effective approaches about the research and development of novel macroscopic hydrogel sensor were reported. The monomer was utilized to synthesize hydrogel sensors by free radical polymerization and guest–host interaction. Hydrogel sensors have prominent selectivity to Hg2+ and can be tailored and reused, which are capable of detecting Hg2+ sensitively in flowing and standing water environment with satisfactory performance. This work is expected to open an avenue to construct novel fluorescent analysis method for Hg2+ detection.

An ultrasensitive PVDF-based molecularly imprinted fluorescent test strip for the rapid and off-line detection of 4-NP with improved anti-coffee ring effect

A PVDF-based test strip was prepared for offline visual detection of 4-NP. The test strip was optimized by paper materials and visual effects. F-PDA was used as a fluorescent functional monomer to improve the response time of test strip to 4-NP.

Molecularly imprinted micelles for fluorescent sensing of nonsteroidal anti-inflammatory drugs (NSAIDs)

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used over-the-counter drugs and their uncontrolled disposal is a significant environmental concern. Although their fluorescent sensing is a desirable method of detection for its sensitivity and simplicity, the structural similarity of the drugs makes the design of selective sensors highly challenging. A thiourea-based fluorescent functional monomer was identified in this work to enable highly efficient synthesis of molecularly imprinted nanoparticle (MINP) sensors for NSAIDs such as Indomethacin or Tolmetin. Micromolar binding affinities were obtained in aqueous solution, with binding selectivities comparable to those reported for polyclonal antibodies. The detection limit was ~50 ng/mL in aqueous solution, and common carboxylic acids such as acetic acid, benzoic acid, and citric acid showed negligible interference.

Rhodamine-immobilized optical hydrogels with shape deformation and Hg2+-sensitive fluorescence behaviors

A highly effective method for the research and development of a novel macroscopic hydrogel sensor and bilayer hydrogel is reported. Based on Rhodamine 6G, an Hg2+ sensitive fluorescent functional monomer was synthesized, then the monomer was utilized to synthesize hydrogel sensors and bilayer hydrogels. Hydrogel sensor has prominent selectivity to Hg2+, the bilayer hydrogel has shape changing function additionally. By combining a thermoresponsive hydrogel layer, poly N-isopropylacrylamide (PNIPAM), with an Hg2+ selective hydrogel layer via macroscopic supramolecular assembly, a bilayer hydrogel is obtained that can be tailored and reswells. The bilayer hydrogel sensor can show complex shape deformation caused by the PNIPAM layer and the Hg2+-responsive characteristic of hydrogel sensor layer can be observed under visible light or UV light. This work will provide novel insights for the design and synthesis of novel smart materials with synergistic functions.

A novel fluorescent functional monomer as the recognition element in core-shell imprinted sensors responding to concentration of 2,4,6-trichlorophenol.

We have demonstrated a fluorescent functional monomer instead of the traditional functional monomers for molecularly imprinted sensors. The sensors were firstly used to selectively detect 2,4,6-trichlorophenol (2,4,6-TCP) by solid fluorescence detection without a dispersion solution. Moreover, the selectivity and anti-interference ability of the SiO2@dye-FMIPs sensor meet the requirements of a fluorescent sensor. The novel fluorescent monomer introduced into MIP is no longer just a fluorophore without recognizing ability. The fluorescence intensity of SiO2@dye-FMIPs showed a linear response to 2,4,6-TCP concentration in the range of 0–100 nM with a detection limit of 0.0534 nM. We could also demonstrate that such a system can not only get rid of the confines of traditional functional monomers and detection manner, but also improved the applications of MIPs sensors in sensing systems.

Competitive ELISA-like Label-free Detection of Lysozyme by Using a Fluorescent Monomer-doped Molecularly Imprinted Hydrogel.

We report on a molecularly imprinted hydrogel for the selective fluorescent detection of a targeting protein. To achieve the fluorescent detection of proteins, a fluorescent functional monomer was synthesized with fluorescein isothiocyanate and allylamine. The monomer (FITC-AA) provided a gradable alteration of the absorption spectrum, and a decrease of the fluorescent intensity due to an interaction with the model protein, lysozyme. Also, the imprinted hydrogel (PI-gel) was simply prepared with FITC-AA, the anionic functional monomers, poly(ethylene glycol) dimethacrylate, and lysozyme by radical photo polymerization. The PI-gel showed selective adsorption for lysozyme and the imprinting factor reached to 2.7. Additionally, the PI-gel indicated a gradual decrease of the fluorescent intensity corresponding to the lysozyme concertation similar to a competitive enzyme-linked immunosorbent assay detection.

Fluorescent ion-imprinted sensor for selective and sensitive detection of copper (II) ions

In the present study, a fluorescent ion-imprinted sensor (FIIS) for rapid and convenient detection of Cu2+ ions was fabricated. A fluorescent polymerizable ligand, i.e., 4-(2-aminomethyl)pyridine-N-allylnaphthalimide, was designed and synthesized. The FIIS was prepared by surface functionalization of PVDF membrane with a thin layer of copper (II) ion-imprinted polymer using the synthesized ligand as the fluorescent functional monomer. The intensity of fluorescence emission of FIIS decreased linearly with the increase of copper (II) ions concentration in the range of 0–70.0μM. The results of selectivity tests indicated that FIIS has high specific recognition ability for Cu2+ ions. The recoveries for the spiked samples were in the range of 96.4–104.4%, and the relative standard deviations (RSDs) were found to be 2.17–4.75%. The FIIS was successfully applied to the determination of copper (II) ions in real water samples. The Limits of detection (LODs) for Cu2+ ions in real water samples were in the range of 0.11–0.14 uM. The present study provided a feasible strategy for construction of fluorescent ion-imprinted sensor for convenient, sensitive and selective detection of metal ions.

One-step post-imprint modification achieve dual-function of glycoprotein fluorescent sensor by "Click Chemistry"

A novel molecular imprinting fluorescent sensor synthesized avoiding complicated design and synthesis of a fluorescent functional monomer, and without the extra cost of additional fluorescence materials (quantum dots, carbon dots and fluorescein), only by a click reaction making the common protein imprinting polymers upgraded to a fluorescent sensing material which can be applied to the fast detection of glycoproteins. In this study, a common protein imprinted polymer (protein-IP) which containing a disulfide bond in the imprinted cavities was first synthesized, then the disulfide linkage was cleaved by reduction, the exposed thiol groups were used for the click reaction to introduce 4-vinyl phenylboronic acid to improve the imprinted recognition for glycoproteins and convert recognition behavior into fluorescent signal simultaneously in one-step site-specific post-imprinting modifications (PIMs). Good linear relationship was obtained in the range of 0.1–10mgmL−1 by fluorescence assay, comparison of the adsorption capacity of the MIPs before and after modification proved that the method has no negative impact on the imprinting effect and exhibit good imprinting effect for glycoproteins of different molecular size and weight.

A Novel 2-Acrylamide-6-Methoxybenzothiazole Fabricated Molecularly Imprinted Polymers for Direct Fluorescent Sensing of Alachlor

In this work, a fluorescent, molecularly imprinted polymer sensor was developed for the rapid and direct sensing of trace alachlor. 2-Acrylamide-6-methoxybenzothiazole, synthesized via a simple one-step reaction with 2-amino-6-methoxybenzothiazole and acryloyl chloride, was used as both fluorescent reporter and functional monomer to prepare an alachlor-imprinted polymer. In this way, binding events produced physically detectable fluorescence signals, and the alachlor could therefore be quantified directly without any further treatment. Binding experiments demonstrated that the fluorescence intensity of the resultant polymer decreased linearly with increases in the concentration of alachlor, in the range of 1–150 μM, and with a detection limit of 0.5 μM. In addition, the fluorescent sensor exhibited significant selectivity toward alachlor over its potentially competing molecules of S-metolachlor, cyanazine, and cypermethrin. Finally, the proposed method was successfully applied for the determination of trace alachlor in corn seed samples, with excellent recoveries ranging from 95.58 to 103.83 %. The developed method shows great potential for the determination of residual alachlor in real samples.

Molecular imprinting-based fluorescent optosensor using a polymerizable 1,8-naphthalimide dye as a florescence functional monomer

A molecular imprinting-based fluorescent optosensor (FMIPs) was developed based on N-allyl-4-ethylenediamine-1,8-naphthalimide as a fluorescent functional monomer in order to study the selective recognition of caffeine as a model drug. The photo physical characteristics of dye and its imprinting polymer in solution and solid form were investigated in the presence of caffeine. The sensing principle was also discussed. Fluorescence emissions of synthesized FMIP as well as monomer dye were ‘switched off’ in the presence of target molecule based on PET mechanism. The relative intensity was linear against caffeine concentration from 1.94×10−6 to 1.94×10−4gml−1 with a detection limit of 1.22×10−6gml−1. The present FMIP sensor has been successfully applied to the determination of caffeine in real samples.

Core-shell nanostructured molecular imprinting fluorescent chemosensor for selective detection ofatrazine herbicide

To convert the binding events on molecularly imprinted polymers (MIPs) into physically detectable signals and to extract the templates completely are the great challenges in developing MIP-based sensors. In this paper, a core-shell nanostructure was employed in constructing the MIP chemosensor for the improvements of template extraction efficiency and imprinted sites accessibility. Vinyl-substituted zinc(II) protoporphyrin (ZnPP) was used as both fluorescent reporter and functional monomer to synthesize atrazine-imprinted polymer shell at silica nanoparticle cores. The template atrazine coordinates with the Lewis acid binding site Zn of ZnPP to form a complex for the molecular imprinting polymerization. These imprinted sites are located in polymer matrix of the thin shells (~8 nm), possessing better accessibility and lower mass-transfer resistance for the target molecules. The fluorescence properties of ZnPP around the imprinted sites will vary upon rebinding of atrazine to these imprinted sites, realizing the conversion of rebinding events into detectable signals by monitoring fluorescence spectra. This MIP probe showed a limit of detection (LOD) of about 1.8 μM for atrazine detection. The core-shell nanostructured MIP method not only improves the sensitivity, but also shows high selectivity for atrazine detection when compared with the non-molecular imprinted counterparts.

A fluorescent sensor array based on ion imprinted mesoporous silica

We report an ion imprinted mesoporous silica based fluorescence turn-on sensor array for discrimination of metal ions. A novel fluorescent functional monomer containing an 8-hydroxyquinoline (8-HQ) moiety in combination with one-pot co-condensation method was employed to prepare fluorescent ion imprinted mesoporous silica. The imprinted materials for Zn 2+ and Cd 2+ as well as a control blank non-imprinted material (NIM) were synthesized. With the covalently anchored organic fluorophore in the inorganic mesoporous silica matrix, the binding of metal ions to the imprinting site was directly transformed into fluorescence signals. Both the imprinted materials displayed faster binding kinetics toward metal ions than NIM. Apparent binding constants (adsorption constants) for the materials with the metal ions in water were determined by a Langmuir-type analysis of the spectrofluorimetric titration data. The sensor array composed of the three materials allows discriminating the two template metal ions (Zn 2+ and Cd 2+) plus three non-template metal ions (Mg 2+, Ca 2+ and Al 3+) at two different concentrations. This work proves that using a simple fluorescent receptor can provide a pattern based fluorescent sensing system by taking advantage of the imprinting effect.

Fluorescent Imprinted Polymers Prepared with 2‐Acrylamidoquinoline as a Signaling Monomer.

A cyclobarbital-selective molecularly imprinted polymer was prepared using a fluorescent functional monomer, 2-acrylamidoquinoline. This monomer was designed to increase in fluorescence intensity upon hydrogen bonding to the cyclobarbital guest. The resultant imprinted polymers exhibited the enhancement of the fluorescence intensity when cyclobarbital was bound. Our results show that this fluorescent responsive imprinting method could be useful in the development of sensors for quantification of nonfluorescent compounds.

Fluorescent Imprinted Polymers Prepared with 2-Acrylamidoquinoline as a Signaling Monomer

[structure: see text] A cyclobarbital-selective molecularly imprinted polymer was prepared using a fluorescent functional monomer, 2-acrylamidoquinoline. This monomer was designed to increase in fluorescence intensity upon hydrogen bonding to the cyclobarbital guest. The resultant imprinted polymers exhibited the enhancement of the fluorescence intensity when cyclobarbital was bound. Our results show that this fluorescent responsive imprinting method could be useful in the development of sensors for quantification of nonfluorescent compounds.

Multiple hydrogen bonding-based fluorescent imprinted polymers for cyclobarbital prepared with 2,6-bis(acrylamido)pyridine.

A cyclobarbital-imprinted polymer was prepared using a fluorescent functional monomer, 2,6-bis(acrylamido)pyridine, and the polymer showed not only selective binding of cyclobarbital but also enhancement of fluorescence intensity, suggesting that the polymer could be utilized as a selective fluorescence probe.

Molecular imprinting-based fluorescent chemosensor for histamine using zinc(II)–protoporphyrin as a functional monomer

A commercially available reagent zinc(II)–protoporphyrin (ZnPP) is used as a novel fluorescent functional monomer to synthesize molecularly imprinted polymers (MIPs) for the selective recognition of histamine. ZnPP having a Lewis acid binding site Zn, binds with the imidazolyl group of histamine through coordination. Association constant ( K ass) and the number of accessible sites ( N) between the MIP and the template are found to be dependent upon the template concentration. By using Scatchard’s plot, the K ass and N are determined as 4500 l/mol and 180 μmol/g when the concentration of histamine is 0.1–1 mmol/l, but the two values are obtained, respectively, as 270 l/mol and 1100 μmol/g when the concentration is 4–10 mmol/l. The binding ability was also evaluated more accurately with a multi-binding model. Highly binding affinity is found for the ZnPP-based polymer than that only using methacrylic acid (MAA) as a functional monomer. Fluorescence intensity of the MIP decreased with histamine concentration but saturation behavior is observed when the histamine concentration is above 1 mmol/l, indicating that histamine no longer coordinated with ZnPP in the MIP and led to the low association constant at this condition.

Recognition of Histamine by a Molecularly Imprinted Polymer Based on Zinc(II)-Protoporphyrin as the Fluorescent Functional Monomer

Recognition of Histamine by a Molecularly Imprinted Polymer Based on Zinc(II)-Protoporphyrin as the Fluorescent Functional Monomer