A surface functional monomer-directing strategy for highly dense imprinting of TNT at surface of silica nanoparticles

Advances in the manufacture of MIP nanoparticles

Molecularly imprinted polymers (MIPs) are prepared by creating a three-dimensional polymeric matrix around a template molecule. After the matrix is removed, complementary cavities with respect to shape and functional groups remain. MIPs have been produced for applications in in vitro diagnostics, therapeutics and separations. However, this promising technology still lacks widespread application because of issues related to large-scale production and optimization of the synthesis. Recent developments in the area of MIP nanoparticles might offer solutions to several problems associated with performance and application. This review discusses various approaches used in the preparation of MIP nanoparticles, focusing in particular on the issues associated with large-scale manufacture and implications for the performance of synthesized nanomaterials.

The Rebinding Properties of Bovine Serum Albumin Imprinted Calcium Phosphate/Polyacrylate/Alginate Hybrid Polymer Microspheres

Calcium phosphate/polyacrylate/alginate hybrid polymer microspheres with bovine serum albumin (BSA) embedded and coated on the surface were prepared with (NH4)2HPO4, sodium polyacrylate (SPA) and sodium alginate (SA) via Ca2+ crosslinking in inverse suspension. Rebinding behaviors of the microspheres were evaluated. The factors influencing the imprinting efficiency (IE) of imprinted microspheres were also studied, including the concentration of CaCl2, template content and pH values in rebinding solutions. Selectivity tests showed that the imprinted microspheres exhibited good recognition property for the template protein.

Preparation of dummy template imprinted polymers at surface of silica microparticles for the selective extraction of trace bisphenol A from water samples

Molecularly imprinted polymers for bisphenol A (BPA) were prepared by using surface molecular imprinting technique. Analogues of BPA, namely 4,4'-dihydroxybiphenyl and 3,3',5,5'-tetrabromobisphenol A, were used as the dummy templates instead of BPA, to avoid the leakage of a trace amount of the target analyte (BPA). The resulting dummy molecularly imprinted polymers (DMIPs) showed the large sorption capacity, high recognition ability and fast binding kinetics for BPA. The maximal sorption capacity was up to 958 micromol g(-1), and it only took 40 min for DMIPs to achieve the sorption equilibrium. The DMIPs were successfully applied to the solid-phase extraction coupled with HPLC/UV for the determination of BPA in water samples. The calibration graph of the analytical method was linear with a correlation coefficient more than 0.999 in the concentration range of 0.0760-0.912 ng mL(-1) of BPA. The limit of detection was 15.2 pg mL(-1) (S/N=3). Recoveries were in the range of 92.9-102% with relative standard deviation (RSD) less than 11%. The trace amounts of BPA in tap water, drinking water, rain and leachate of one-off tableware were determined by the method built, and the satisfactory results were obtained.

Well-defined PMMA brush on silica particles fabricated by surface-initiated photopolymerization (SIPP)

The photochemical method is a convenient and simple way to synthesize the polymer brush on surface. We presented here a facile approach to fabricate PMMA brush on silica particles (SPs) by combination of self-assembly monolayer of hyperbranched polymeric thioxanthone (HPTX) and surface-initiated photopolymerization (SIPP). HPTX was immobilized on the surface of silica particles (SPs) through nucleophilic addition between amine and epoxy groups, and then initiated photopolymerization of MMA to generate PMMA brush on SPs at room temperature. The whole process was well-traced by FT-IR, TGA, SEM, and TEM. The results show that it is easy to create PMMA brushes of tunable thickness under UV irradiation. Especially, TEM images reveal the obvious formation of well-defined hybrid particles with SPs as the core and PMMA layers as the shell. The obtained hybrid particles can be implanted into PMMA matrix to produce PMMA composite with enhanced thermal and mechanical properties.

Separation of phthalocyanine-like substances from humic acids using a molecular imprinting method and their photochemical activity under simulated sunlight irradiation

To elucidate the existence of phthalocyanine-like (Pc-like) substances in humic acids (HA) and their roles in photochemical transformation of organic pollutants, Pc-imprinted polymers (MIP) were synthesized successfully and employed to separate Pc-like substances from HA. The fraction bound by MIP (F(mip-b)) presented better photochemical activity for degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) in aqueous solution irradiated by simulated sunlight. The pseudo-first-order rate constant of 2,4-D photodegradation with the presence of F(mip-b) was 2.5 times as high as that in solution containing effluent fraction (F(eff)). These results show the key role of some HA with special structures in photochemistry and are helpful for better understanding phototransformation of environmental contaminants in natural aquatic systems.

Magnetic molecularly imprinted polymer for aspirin recognition and controlled release

Core-shell structural magnetic molecularly imprinted polymers (magnetic MIPs) with combined properties of molecular recognition and controlled release were prepared and characterized. Magnetic MIPs were synthesized by the co-polymerization of methacrylic acid (MAA) and trimethylolpropane trimethacrylate (TRIM) around aspirin (ASP) at the surface of double-bond-functionalized Fe(3)O(4) nanoparticles in chloroform. The obtained spherical magnetic MIPs with diameters of about 500 nm had obvious superparamagnetism and could be separated quickly by an external magnetic field. Binding experiments were carried out to evaluate the properties of magnetic MIPs and magnetic non-molecularly imprinted polymers (magnetic NIPs). The results demonstrated that the magnetic MIPs had high adsorption capacity and selectivity to ASP. Moreover, release profiles and release rate of ASP from the ASP-loaded magnetic MIPs indicated that the magnetic MIPs also had potential applications in drug controlled release.

Analytical chemistry with silica sol-gels: traditional routes to new materials for chemical analysis

The versatility of sol-gel chemistry enables us to generate a wide range of silica and organosilica materials with controlled structure, composition, morphology and porosity. These materials' hosting and recognition properties, as well as their wide-open structures containing many easily accessible active sites, make them particularly attractive for analytical purposes. In this review, we summarize the importance of silica sol-gels in analytical chemistry by providing examples from the separation sciences, optical and electrochemical sensors, molecular imprinting, and biosensors. Recent work suggests that manipulating the structure and composition of these materials at different scales (from molecular to macromolecular states and/or from micro- to meso- and/or macroporous levels) promises to generate chemical and biochemical sensing devices with improved selectivity and sensitivity.

Molecularly Imprinted Polymers and Controlled/Living Radical Polymerization

Molecularly imprinted polymers (MIPs) are tailor-made biomimetic receptors that are obtained by polymerization in the presence of molecular templates. They contain binding sites for target molecules with affinities and specificities on a par with those of natural receptors such as antibodies, hormone receptors, or enzymes. A great majority of the literature in the field describes materials based on polymers obtained by free radical polymerization. In order to solve general problems associated with MIPs, in particular their heterogeneity in terms of inner morphology and distribution of binding site affinities, it has been suggested to use modern methods of controlled/living radical polymerization for their synthesis. This also facilitates their generation in the form of nanomaterials, nanocomposites, and thin films, a strong recent trend in the field. The present paper reviews recent advances in the molecular imprinting area, with special emphasis on the use of controlled polymerization methods, their benefits, and current limitations.

Imprinting of Molecular Recognition Sites on Nanostructures and Its Applications in Chemosensors

Biological receptors including enzymes, antibodies and active proteins have been widely used as the detection platform in a variety of chemo/biosensors and bioassays. However, the use of artificial host materials in chemical/biological detections has become increasingly attractive, because the synthetic recognition systems such as molecularly imprinted polymers (MIPs) usually have lower costs, higher physical/chemical stability, easier preparation and better engineering possibility than biological receptors. Molecular imprinting is one of the most efficient strategies to offer a synthetic route to artificial recognition systems by a template polymerization technique, and has attracted considerable efforts due to its importance in separation, chemo/biosensors, catalysis and biomedicine. Despite the fact that MIPs have molecular recognition ability similar to that of biological receptors, traditional bulky MIP materials usually exhibit a low binding capacity and slow binding kinetics to the target species. Moreover, the MIP materials lack the signal-output response to analyte binding events when used as recognition elements in chemo/biosensors or bioassays. Recently, various explorations have demonstrated that molecular imprinting nanotechniques may provide a potential solution to these difficulties. Many successful examples of the development of MIP-based sensors have also been reported during the past several decades. This review will begin with a brief introduction to the principle of molecular imprinting nanotechnology, and then mainly summarize various synthesis methodologies and recognition properties of MIP nanomaterials and their applications in MIP-based chemosensors. Finally, the future perspectives and efforts in MIP nanomaterials and MIP-based sensors are given.

Surface-imprinted nanostructured layer-by-layer film for molecular recognition of theophylline derivatives

In this article we report the introduction of the cooperativity of various specific interactions combined with photo-cross-linking of the interlayers to yield binding sites that can realize better selectivity and imprinting efficiency of a surface molecularly imprinted LbL film (SMILbL), thus providing a new approach toward fabrication of nanostructured molecularly imprinted thin films. It involves preassembly of poly(acrylic acid) (PAA) conjugated of the theophylline residue template via a disulfide bridge, denoted as PAAtheo 15, in solution, and layer-by-layer (LbL) assembly of PAAtheo 15 and a positively charged photoreactive diazo resin (DAR) to form multilayer thin film with designed architecture. After photo-cross-linking of the film and template removal, binding sites specific to 7-(beta-hydroxyethyl)theophylline (Theo-ol) molecules are introduced within the film. Binding assay demonstrates that the SMILbL has a high selectivity of SMILbL to Theo-ol over caffeine. A control experiment demonstrates that the selectivity of SMILbL derives from nanostructured recognition sites among the layers. The imprinting amount per unit mass of the film can be 1 order of magnitude larger than that of the conventional bulk molecular imprinting systems. As this concept of construction SMILbL can be easily extended to the other molecules by the following similar protocol: its applications in building many other different molecular recognition systems are greatly anticipated.

Molecular imprinting at walls of silica nanotubes for TNT recognition

This paper reports the molecular imprinting at the walls of highly uniform silica nanotubes for the recognition of 2,4,6-trinitrotoluene (TNT). It has been demonstrated that TNT templates were efficiently imprinted into the matrix of silica through the strong acid-base pairing interaction between TNT and 3-aminopropyltriethoxysilane (APTS). TNT-imprinted silica nanotubes were synthesized by the gelation reaction between APTS and tetraethylorthosilicate (TEOS), selectively occurring at the porous walls of APTS-modified alumina membranes. The removal of the original TNT templates leaves the imprinted cavities with covalently anchored amine groups at the cavity walls. A high density of recognition sites with molecular selectivity to the TNT analyte was created at the wall of silica nanotubes. Furthermore, most of these recognition sites are situated at the inside and outside surfaces of tubular walls and in the proximity of the two surfaces due to the ultrathin wall thickness of only 15 nm, providing a better site accessibility and lower mass-transfer resistance. Therefore, greater capacity and faster kinetics of uptaking target species were achieved. The silica nanotube reported herein is an ideal form of material for imprinting various organic or biological molecules toward applications in chemical/biological sensors and bioassay.