Monoclonal behavior of molecularly imprinted polymer nanoparticles in capillary electrochromatography

Biodegradable and Sustainable Synthetic Antibodies-A Perspective

Molecular imprinting technology has been around for almost a century, and we have witnessed dramatic advancements in the overall design and production of molecularly imprinted polymers (MIPs), particularly in terms of possible formats of the final products when it comes to truly resembling antibody substitutes, i.e., MIP nanoparticles (MIP NPs). Nonetheless, the overall technology appears to struggle to keep up with the current global sustainability efforts, as recently elucidated in the latest comprehensive reviews, which introduced the "GREENIFICATION" concept. In this review, we will try to elucidate if these advancements in MIP nanotechnology have indeed resulted in a sustainability amelioration. We will do so by discussing the general production and purification strategies for MIP NPs, specifically from a sustainability and biodegradation perspective, also considering the final intended application and ultimate waste management.

Recent application of molecular imprinting technique in food safety

Due to the extensive use of chemical substances such as pesticides, antibiotics and food additives, food safety issues have gradually attracted people's attention. The extensive use of these chemicals seriously damages human health. In order to detect trace chemical residues in food, researchers have to find several simple, economical and effective tools for qualitative and quantitative analysis. As a kind of material that specifically and selectively recognize template molecules from real samples, molecular imprinting technique (MIT) has widely applied in food samples analysis. This article mainly reviews the application of molecularly imprinted polymer (MIP) in the detection of chemical residues from food in the past five years. Some recent and novel methods for fabrication of MIP are reviewed. Their application of sample pretreatment, sensors, etc. in food analysis is reviewed. The application of molecular imprinting in chromatographic stationary phase is referred. Additionally, the challenges faced by MIP are discussed.

Molecular Imprinting: Green Perspectives and Strategies

Advances in revolutionary technologies pose new challenges for human life; in response to them, global responsibility is pushing modern technologies toward greener pathways. Molecular imprinting technology (MIT) is a multidisciplinary mimic technology simulating the specific binding principle of enzymes to substrates or antigens to antibodies; along with its rapid progress and wide applications, MIT faces the challenge of complying with green sustainable development requirements. With the identification of environmental risks associated with unsustainable MIT, a new aspect of MIT, termed green MIT, has emerged and developed. However, so far, no clear definition has been provided to appraise green MIT. Herein, the implementation process of green chemistry in MIT is demonstrated and a mnemonic device in the form of an acronym, GREENIFICATION, is proposed to present the green MIT principles. The entire greenificated imprinting process is surveyed, including element choice, polymerization implementation, energy input, imprinting strategies, waste treatment, and recovery, as well as the impacts of these processes on operator health and the environment. Moreover, assistance of upgraded instrumentation in deploying greener goals is considered. Finally, future perspectives are presented to provide a more complete picture of the greenificated MIT road map and to pave the way for further development.

Molecularly Imprinted Nanoparticles for Biomedical Applications

Molecularly imprinted polymers (MIPs) are synthetic receptors with tailor-made recognition sites for target molecules. Their high affinity and selectivity, excellent stability, easy preparation, and low cost make them promising substitutes to biological receptors in many applications where molecular recognition is important. In particular, spherical MIP nanoparticles (or nanoMIPs) with diameters typically below 200 nm have drawn great attention because of their high surface-area-to-volume ratio, easy removal of templates, rapid binding kinetics, good dispersion and handling ability, undemanding functionalization and surface modification, and their high compatibility with various nanodevices and in vivo biomedical applications. Recent years have witnessed significant progress made in the preparation of advanced functional nanoMIPs, which has eventually led to the rapid expansion of the MIP applications from the traditional separation and catalysis fields to the burgeoning biomedical areas. Here, a comprehensive overview of key recent advances made in the preparation of nanoMIPs and their important biomedical applications (including immunoassays, drug delivery, bioimaging, and biomimetic nanomedicine) is presented. The pros and cons of each synthetic strategy for nanoMIPs and their biomedical applications are discussed and the present challenges and future perspectives of the biomedical applications of nanoMIPs are also highlighted.

Strategies for Molecular Imprinting and the Evolution of MIP Nanoparticles as Plastic Antibodies-Synthesis and Applications

Materials that can mimic the molecular recognition-based functions found in biology are a significant goal for science and technology. Molecular imprinting is a technology that addresses this challenge by providing polymeric materials with antibody-like recognition characteristics. Recently, significant progress has been achieved in solving many of the practical problems traditionally associated with molecularly imprinted polymers (MIPs), such as difficulties with imprinting of proteins, poor compatibility with aqueous environments, template leakage, and the presence of heterogeneous populations of binding sites in the polymers that contribute to high levels of non-specific binding. This success is closely related to the technology-driven shift in MIP research from traditional bulk polymer formats into the nanomaterial domain. The aim of this article is to throw light on recent developments in this field and to present a critical discussion of the current state of molecular imprinting and its potential in real world applications.

Tuning surface-cross-linking of molecularly imprinted cross-linked micelles for molecular recognition in water

Molecular recognition in water is an important challenge in supramolecular chemistry. Surface-core double cross-linking of template-containing surfactant micelles by the click reaction and free radical polymerization yields molecularly imprinted nanoparticles (MINPs) with guest-complementary binding sites. An important property of MINP-based receptors is the surface-cross-linking between the propargyl groups of the surfactants and a diazide cross-linker. Decreasing the number of carbons in between the two azides enhanced the binding affinity of the MINPs, possibly by keeping the imprinted binding site more open prior to the guest binding. The depth of the binding pocket can be controlled by the distribution of the hydrophilic/hydrophobic groups of the template and was found to influence the binding in addition to electrostatic interactions between oppositely charged MINPs and guests. Cross-linkers with an alkoxyamine group enabled two-stage double surface-cross-linking that strengthened the binding constants by an order of magnitude, possibly by expanding the binding pocket of the MINP into the polar region. The binding selectivity among very similar isomeric structures also improved.

Surface Ligands in the Imprinting and Binding of Molecularly Imprinted Cross-Linked Micelles

Molecular recognition in water is challenging but water-soluble molecularly imprinted nanoparticle (MINP) receptors were produced readily by double cross-linking of surfactant micelles in the presence of suitable template molecules. When the micellar surface was decorated with different polyhydroxylated ligands, significant interactions could be introduced between the surface ligands and the template. Flexible surface ligands worked better than rigid ones to interact with the polar moiety of the template, especially for those template molecules whose water-exposed surface is not properly solvated by water. The importance of these hydrophilic interactions was examined in the context of different substrates, density of the surface ligands, and surface-cross-linking density of the MINP. Together with the hydrophobic interactions in the core, the surface hydrophilic interactions can be used to enhance the binding of guest molecules in water.

Selective Binding of Folic Acid and Derivatives by Imprinted Nanoparticle Receptors in Water

Folate receptors are overexpressed on cancer cells and frequently used for targeted delivery. Creation of synthetic receptors to bind folic acid and its analogues in water, however, is challenging because of its complex hydrogen-bonding patterns and competition for hydrogen bonds from the solvent. Micellar imprinting within cross-linkable surfactants circumvented these problems because the nonpolar micellar environment strengthened the hydrogen bonds between the amide group in the surfactant and the template molecule. Incorporation of polymerizable thiouronium functional monomers further enhanced the binding through hydrogen-bond-reinforced ion pairs with the glutamate moiety of the template. The resulting imprinted micelles were able to bind folate and their analogues with submicromolar affinity and distinguish small changes in the hydrogen-bonding patterns as well as the number/position of carboxylic acids. The binding constant obtained was 2-3 orders of magnitude higher than those reported for small-molecule synthetic receptors. Our binding study also revealed interesting details in the binding. For example, the relative contributions of different segments of the molecule to the binding followed the order of carboxylates > pyrimidine ring > pyrazine ring.

Imprinted micelles for chiral recognition in water: shape, depth, and number of recognition sites

Chiral molecular recognition is important to biology, separation, and asymmetric catalysis. Because there is no direct correlation between the chiralities of the host and the guest, it is difficult to design a molecular receptor for a chiral guest in a rational manner. By cross-linking surfactant micelles containing chiral template molecules, we obtained chiral nanoparticle receptors for a number of 4-hydroxyproline derivatives. Molecular imprinting allowed us to transfer the chiral information directly from the guest to host, making the molecular recognition between the two highly predictable. Hydrophobic interactions between the host and the guest contributed strongly to the enantio- and diastereoselective differentiation of these compounds in water, whereas ion-pair interactions, which happened near the surface of the micelle, were less discriminating. The chiral recognition could be modulated by tuning the size and shape of the binding pockets.

A General Method for Selective Recognition of Monosaccharides and Oligosaccharides in Water

Molecular recognition of carbohydrates plays vital roles in biology but has been difficult to achieve with synthetic receptors. Through covalent imprinting of carbohydrates in boroxole-functionalized cross-linked micelles, we prepared nanoparticle receptors for a wide variety of mono- and oligosaccharides. The boroxole functional monomer bound the sugar templates through cis-1,2-diol, cis-3,4-diol, and trans-4,6-diol. The protein-sized nanoparticles showed excellent selectivity for d-aldohexoses in water with submillimolar binding affinities and completely distinguished the three biologically important hexoses (glucose, mannose, and galactose). Glycosides with nonpolar aglycon showed stronger binding due to enhanced hydrophobic interactions. Oligosaccharides were distinguished on the basis of their monosaccharide building blocks, glycosidic linkages, chain length, as well as additional functional groups that could interact with the nanoparticles.

Water-Soluble Molecularly Imprinted Nanoparticle Receptors with Hydrogen-Bond-Assisted Hydrophobic Binding

Molecularly imprinted nanoparticles (MINPs) were prepared when surfactants with a tripropargylammonium headgroup and a methacrylate-functionalized hydrophobic tail were cross-linked in the micelle form on the surface and in the core in the presence of hydrophobic template molecules. With the surfactants containing an amide bond near the headgroup, the MINPs had a layer of hydrogen-bonding groups in the interior that strongly influenced their molecular recognition. Templates/guests with strong hydrogen-bonding groups in the midsection of the molecule benefited most, especially if the hydrophobe of the template could penetrate the amide layer to reach the hydrophobic core of the cross-linked micelles. The location and the orientation of the hydrophilic groups were also important, as they determined how the template interacted with the surfactant micelles and, ultimately, with the MINP receptors.

Approaches for enantioselective resolution of pharmaceuticals by miniaturised separation techniques with new chiral phases based on nanoparticles and monolithis

This article discusses new developments in the preparation of nanoparticles and monoliths with emphasis upon their application as the stationary and pseudo-stationary phases for miniaturised liquid phase separation techniques, which have occurred in the last 10 years (from 2006 to the actuality). References included in this review represent current trends and state of the art in the application of these materials to the analysis, by EKC, CEC and miniaturised chromatography, of chiral compounds with environmental interest such as pharmaceuticals. Due to their extraordinary properties, columns prepared with these new chiral stationary or pseudo-stationary phases, based on materials such as gold nanoparticles, metal-organic frameworks, ordered mesoporous silicas, carbonaceous materials, polymeric-based and silica-based monoliths or molecularly imprinted materials, can usually show some improvements in the separation selectivity, column efficiency and chemical stability in comparison with conventional chiral columns available commercially.

Molecularly imprinted polymers for the analysis and removal of polychlorinated aromatic compounds in the environment: a review

Molecularly imprinted polymers selective to polychlorinated aromatic compounds for application in environmental studies.

Reflux precipitation polymerization: a new synthetic insight in molecular imprinting at high temperature

Reflux precipitation polymerization was first used to fabricate monodispersed MIP microspheres, indicating electrostatic interaction was important for molecular imprinting at high temperature.

Efficient separation of tanshinones by polyvinylpyrrolidone-stabilized graphene-modified micellar electrokinetic chromatography

In this work, a PVP-stabilized graphene was used in MEKC for the separation of tanshinones. Seven structurally similar tanshinones were studied, that is, tanshinone IIB, dihydrotanshinone I, tanshinone I, cryptotanshinone, 1,2-dihydrotanshinone I, miltirone, and tanshinone IIA. To achieve optimal conditions, graphene concentration, sample solvent composition, SDS concentration, 2-propanolconcentration, and buffer pH were investigated. At a separation voltage of 30 kV and a 41.5 cm effective length fused-silica capillary, good resolution within 12 min was performed using 10 mM borate buffer (pH 9.3) containing 30 mM SDS, 10% v/v 2-propanol and 6 μg/mL graphene. The method was validated in terms of linearity (r(2) > 0.9970), intra- and inter-day precision were less than 3.56 and 4.83%, respectively. The proposed method was then successfully applied to Danshentong capsule, an herbal preparation from Salvia miltiorrhiza. Our results indicated the high separation efficiency of PVP-stabilized graphene provided new opportunities for the analysis of complex samples.

Current trends in the development of molecularly imprinted polymers in CEC

This review focused on the developments in the field of molecularly imprinted polymers (MIPs) for CEC since 2009. New preparation techniques of MIP-based CEC, such as, portable microchip with macroporous monolithic imprinted microchannel, and low cross-linking MIPs based on liquid crystalline monomers, were discussed. Using selected cases rather than a comprehensive review of the entire field, our goal is to highlight the studies of the interest with an emphasis on recent work, and offers suggestions for future development in the field of imprinted materials for CEC separation.

Crosslinked plastic scintillators: a new detection system for radioactivity measurement in organic and aggressive media

The measurement of radioactive solutions containing organic or aggressive media may cause stability problems in liquid and plastic scintillation (PS) techniques. In the case of PS, this can be overcome by adding a crosslinker to the polymer structure. The objectives of this study are to synthesise a suitable crosslinked plastic scintillator (C-PS) for radioactivity determination in organic and aggressive media. The results indicated that an increase in the crosslinker content reduces the detection efficiency and a more flexible crosslinker yields higher detection efficiency. For the polymer composition studied, 2,5-diphenyloxazole (PPO) is the most adequate fluorescent solute and an increase in its concentration causes little change in the detection efficiency. The inclusion of a secondary fluorescent solute 1,4-bis-2-(5-phenyloxazolyl) benzene (POPOP) improves the C-PS radiometrical characteristics. For the final composition chosen, the synthesis of the C-PS exhibits good reproducibility with elevated yield. The obtained C-PS also displays high stability in different organic (toluene, hydrotreated vegetable oil (HVO) and methanol) and aggressive media (hydrochloric acid, nitric acid and hydrogen peroxide). Finally, the C-PS exhibits high detection efficiency both in water and in aggressive media and can also be applied in organic media showing similar or even higher detection efficiency values.

Molecular imprinting science and technology: a survey of the literature for the years 2004-2011

Herein, we present a survey of the literature covering the development of molecular imprinting science and technology over the years 2004-2011. In total, 3779 references to the original papers, reviews, edited volumes and monographs from this period are included, along with recently identified uncited materials from prior to 2004, which were omitted in the first instalment of this series covering the years 1930-2003. In the presentation of the assembled references, a section presenting reviews and monographs covering the area is followed by sections describing fundamental aspects of molecular imprinting including the development of novel polymer formats. Thereafter, literature describing efforts to apply these polymeric materials to a range of application areas is presented. Current trends and areas of rapid development are discussed.

Analysis of five alkaloids using surfactant-coated multi-walled carbon nanotubes as the pseudostationary phase in nonaqueous capillary electrophoresis

In this paper, surfactant-coated multi-walled carbon nanotubes (SC-MWNTs) have been proposed as a novel pseudostationary phase (PSP) to enhance the separation of isoquinoline alkaloids in nonaqueous capillary electrophoresis (NACE). Several parameters affecting NACE separation were studied including the MWNT concentration, the electrolyte concentration, pH* and the separation voltage. In comparison to conventional NACE, the addition of an MWNT dispersion using surfactant solutions in the electrolyte produced an important enhancement in the resolution due to the π-π interactions between the analytes and the surface of the carbon nanotubes. Using SC-MWNTs (6μgmL(-1)) as a PSP in the background electrolyte (BGE) (i.e., 20mM sodium acetate in methanol-acetonitrile (80:20, v/v)) provided the complete separation of five alkaloids. Finally, the developed method has been successfully applied to the detection and quantification of the tested compounds of Rhizoma Coptidis.

Application of polymeric surfactants in chiral micellar electrokinetic chromatography (CMEKC) and CMEKC coupled to mass spectrometry

The use of amino acid-based polymeric surfactants (a.k.a. molecular micelles) in chiral micellar electrokinetic chromatography (CMEKC) has been shown to be a successful separation mode for capillary electrophoresis (CE). In this mode, chiral compounds can be enantioseparated with high efficiency, high chiral selectivity, and versatility. This chapter describes the state-of-the art studies published in the past 5 years in CMEKC using polymeric surfactants. Recent trends in the compatibility of chiral polymeric surfactants with mass spectrometric (MS) detection suggest that this type of chiral selector may be the most promising ones for chiral CE-MS applications. The synthesis of new anionic and cationic MS-compatible polymeric surfactants and their utility in CMEKC and CMEKC-MS are demonstrated. Examples of how to run a typical CMEKC-MS experiment using univariate and multivariate optimization of CMEKC and MS parameters are discussed.

Molecularly imprinted nanoparticles with nontailing peaks in capillary electrochromatography

The combination of microparticles of molecularly imprinted polymers (MIPs) with partial filling capillary electrochromatography (CEC) has previously been demonstrated for the enantiomer separation. In this paper, precipitation polymerization was used to prepare d-zopiclone imprinted nanoparticles (50-80 nm) by a strategy of the dilution of pre-polymerization mixtures. The influence of some important parameters on the preparation of MIPs nanoparticles, including template to monomer ratio, type and amount of cross-linking monomer, and functional monomer composition ratio were investigated. In addition, the effect of separation condition, e.g., organic modifier content, pH value and salt concentration of buffer, on the electrochromatographic behavior of the MIP nanoparticles were studied. In spite of lower selectivity factor (1.11), high column performance (theoretical plates 41,400) of template was obtained and the resolution of enantiomers separation was 4.75 under the optimized conditions. Compared to the previously reported MIP microparticles, the MIP nanoparticles showed good peak symmetry and an ability of high speed separation (<15 min) in CEC mode.

Synthesis and evaluation of uniformly sized nalidixic acid-imprinted nanospheres based on precipitation polymerization method for analytical and biomedical applications

For the first time in this work, uniform molecularly imprinted polymer (MIP) nanoparticles were prepared using nalidixic acid as a template. The MIP nanoparticles were successfully synthesized by precipitation polymerization applying methacrylic acid (MAA) as a functional monomer and trimethylolpropane trimethacrylate (TRIM) as a cross-linking monomer at different mole ratios. The morphology, binding, recognition, selectivity, and in vitro release behaviors of obtained particles were studied. The produced polymers were characterized by Fourier transform infrared spectroscopy and differential scanning calorimetric. Furthermore, their morphology was analyzed accurately by scanning electron microscopy, photon correlation spectroscopy, and Brunauer-Emmett-Teller analysis. The nanospheres and microspheres with mean diameter values of 94 nm, 256 nm, and 1.2 µm were obtained using nalidixic acid-MAA-TRIM various mole ratios. Among the MIPs, the product with nalidixic acid-MAA-TRIM mole ratio of 1:12:12 established nanospheres with the lowest polydispersity index (0.003), an average pore diameter (12 nm), and the highest specific surface area (280 m(2) g(-1)) and selectivity factor (10.4). Results from binding experiments demonstrated that the imprinted nanospheres with a 94-nm mean diameter and a binding capacity of 28 mg of nalidixic acid per gram of polymer had higher specific affinity to nalidixic acid in contrast with the other imprinted nanospheres, microspheres, and nonimprinted particles. However, the binding performance of imprinted nanospheres in human serum was estimated using high-performance liquid chromatography analysis (binding approximately 98% of nalidixic acid). In addition, release experiments proved to be successful in the controlled release of nalidixic acid during a long period. The 20% of loaded nalidixic acid was released from the imprinted nanospheres within the first 20 h, whereas the remaining 80% was released in the after 120 h. The nalidixic acid release kinetics from the MIPs was highly affected by properties of the particles.