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Molecularly imprinted polymer hollow spheres (MIHSs) were produced by using hexanitrohexaazaisowurtzitane (HNIW or CL-20) as a template, silica nanospheres as a sacrificial matrix, acrylamide as a functional monomer, ethylene glycol dimethacrylate as a cross-linker and acetonitrile as a porogen at 4 °C under UV irradiation. This sorbent was applied to the selective solid-phase extraction (SPE) of several explosives simultaneously by using a newly-developed SPE procedure. For the first time, 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) and CL-20 were selectively extracted and determined simultaneously from simulated post-blast samples prepared from motor oil and vacuum pump oil. The matrix effects were successfully eliminated and accurate quantization was achieved. When the loading amounts of HMX, RDX, TNT and CL-20 were, respectively, below 10, 2, 5 and 20 nmol for 100 mg of MIHS, these explosives were almost retrieved completely (above 98%). For the MIHSs and non-imprinted polymer hollow spheres (NIHSs), in acetonitrile and methanol, the imprinting factors (IFs) of CL-20 and tetraacetyldibenzylhexaazaisowurtzitane (TADB, a structural analogue of CL-20) changed dramatically, from 7.75 to 1.57 and 0.88 to 2.39, respectively. It highlighted the significant effect of solvents on imprinted sites. [ABSTRACT FROM AUTHOR]

Abstract: Molecular imprinting is a useful method to make enzyme mimics for protein recognition. Classic protein imprinting involves entrapping proteins within polysiloxane or polyacrylamide, but due to the rigidity of the recognition sites and the limited interaction between proteins and small molecule monomers, they often have unsatisfactory capacity, poor reproducibility and low specificity. In this report, “soft” and flexible recognition sites that can allow “induced fit” of the target proteins were created by a novel surface imprinting technique. When about 25% of the template proteins were removed, the unremoved proteins created “soft” and flexible loops that can lock into place upon protein rebinding, which provides additional favorable interactions between the rebind proteins and the imprinted sites. The adsorption capacity of the surface imprinted silica is 24.8×10−7 mol/g. The “soft” recognition sites can distinguish target hemoglobin from other proteins such as bovine serum albumin, Cytochrome C and RNase A. [Copyright &y& Elsevier]

Abstract: To assess the potential risks associated with the environmental exposure of β-lactam antibiotics (BLAs), the monitoring of the occurrence, distribution, and fate of these emerging contaminants in the environment is required. Herein, we demonstrate a molecularly imprinted solid-phase extraction (MISPE) method for selective and reliable screening of trace BLAs in river and tap water. By developing a low-temperature photopolymerization, highly selective molecularly imprinted polymers (MIPs) for five BLAs (penicillin G, amoxicillin, ampicillin, nafcillin and mezlocillin) were synthesized. Nafcillin was chosen as a pseudo template to make the MIP sorbent (Nafc-MIP), which was used in pseudo-template MISPE for preconcentration of the other four BLAs from river and tap water. The application of pseudo-template MISPE overcomes the template bleeding, which significantly elevates the sample background and restricts the application of MIP for detection of the target BLA below 2μg/L. The average recoveries of BLAs are in the range of 60–90% when Nafc-MIP was adopted as the selective MISPE sorbent. The developed method was validated, and applied to the screening of trace β-lactam antibiotics in river and tap water. The linearity of the calibration curve for each BLA was observed over the range of 0.1–20μg/L (r >0.998). The β-lactam antibiotics were found within the range of 0–9.56μg/L in river water at the downstream of antibiotics manufacturers, and none were detected in the tap water. [Copyright &y& Elsevier]

We developed a photonic crystal (PhC) sensor for the quantification of 2,4,6-trinitrotoluene (TNT) in solution. Monodisperse (210 nm in diameter) molecularly imprinted colloidal particles (MICs) for TNT were prepared by the emulsion polymerization of methyl methacrylate and acrylamide in the presence of TNT as a template. The MICs were then self-assembled into close-packed opal PhC films. The adsorption capacity of the MICs for TNT was 64 mg TNT/g. The diffraction from the PhC depended on the TNT concentration in a methanol/water (3/2, v/v) potassium dihydrogen phosphate buffer solution (pH = 7.0, 30 mM). The limit of detection (LOD) of the sensor was 1.03 μg. The color of the molecularly imprinted colloidal array (MICA) changed from green to red with an 84 nm diffraction red shift when the TNT concentration increased to 20 mM. The sensor response time was 3 min. The PhC sensor was selective for TNT compared to similar compounds such as 2,4,6-trinitrophenol, 2,4-dinitrotoluene, 2,6-dinitrotoluene, 2-nitromesitylene, 4-nitrotoluene, 2-nitrotoluene, 1,3-dinitrobenzene, methylbenzene, 4-nitrophenol, 2-nitroaniline, 3-aminophenol and 3-nitroaniline. The sensor showed high stability with little response change after three years storage. This sensor technology might be useful for the visual determination of TNT. [ABSTRACT FROM AUTHOR]

Ion mobility spectrometry (IMS) was explored in the selective detection of nitrobenzene compounds in industrial waste water and surface water, and the selectivity was theoretically elucidated with the transformation energy in the product ion formation reaction. A linear detection range of 0.5–50 ppm and a limit of detection (LOD) of 0.1 ppm were found for 2,4,6-trinitrotoluene (TNT). With the IMS as the detection system of molecularly imprinted polymer (MIP) separation technique, the MIP-IMS system was proved to be excellent method to detect trace amount of nitrobenzene compounds in surface water, in which more than 87% of nitrobenzene compounds could be adsorbed on MIPs with 90–105% of recovery. [ABSTRACT FROM AUTHOR]

Flash column chromatography prepacked with molecularly imprinted polymers (MIPs) has been successfully used for the extraction of shikimic acid from Chinese star anise. The shikimic acid imprinted polymer with an adsorption capacity of 21.94 µmol g−1dry polymer and imprinting factor of 4.2 was prepared using the dispersion polymerization method. The capacity of the MIP-Flash column was determined as 23.3 mg g−1using a frontal chromatography method when 10 m mol L−1shikimic acid was eluted through the MIP-flash column at 1.7 mL min−1. The crude extract of Chinese star anise loaded on the column was eluted with ethanol/water (40/60, v/v) to remove the impurities, after elution with methanol/water/acetic acid (32/48/20, v/v/v), purified shikimic acid (>95%) was obtained. The MIP-flash column can be reused for at least 4 rounds with capacity lost less than 15%. It was demonstrated that, compared with HPLC, flash column chromatography prepacked with MIPs is a more rapid, feasible, and economical method for the extraction of active ingredients from plants on a large scale based on the technology of molecular imprinting. [ABSTRACT FROM AUTHOR]

Abstract: Molecularly-imprinted polymers in the form of microspheres were synthesized using the dispersion polymerization protocol; cyromazine was used as dummy template, while methacrylic acid, ethylene glycol dimethacrylate and acetonitrile (MeCN) were used as functional monomer, cross-linker, and porogen, respectively. When compared with the non-imprinted polymer, the molecularly-imprinted polymers (MIPs) showed outstanding affinity toward melamine in MeCN with a maximum binding concentration (B max) of 53.20nmolmg−1 MIPs, imprinting effect of 4.6, and a dissociation constant (K d) of 90.45μM. After optimization of the molecularly-imprinted solid-phase extraction conditions, a new method was developed to determine the melamine in milk and feed with gas chromatography–mass spectrometry. The performance of this method has been evaluated in the tainted milk and feed in terms of recovery, precision, linearity, the limit of detection (LOD) and limit of quantitation (LOQ). Recovery ranged in samples from 93.1 to 101.3% with intra-day and inter-day relative standard deviation values below 5.34%. The LOD and LOQ of melamine in milk and feed were 0.01μgmL−1 (μgg−1) and 0.05μgmL−1 (μgg−1), respectively. [ABSTRACT FROM AUTHOR]

As a typical antibiotic that is harmful to the health of human beings and widely used in animal husbandry, oxytetracycline (OTC) has a potential threat to the food safety. Therefore, the design of portable sensors for efficiently monitoring trace amounts of OTC in foods is vital to maintain safe food supply in our daily life. Herein, a two-dimensional (2D) molecularly imprinted photonic crystal hydrogel (MIPCH) sensor for the detection of OTC was fabricated by combining the photonic crystal (PC) method and molecular imprinting technique. In this regard, OTC was used as imprinted template to form the MIPCH sensor with specific binding sites during polymerization. After the removal of template, the obtained MIPCH possessed the specific nanocavities that were complementary to target compound, OTC. In addition, the response of the MIPCH to tetracyclines (TCs) in aqueous solution was monitored through a readable change of Debye diffraction ring, which is related to the particle spacing variation of MIPCH in response to the target molecules. As the concentration of OTC increased from 0 to 60 μM, the particle spacing of MIPCH sensor increased to about 94 nm and the structural color redshifted from blue to red. More importantly, the detection of OTC in milk sample by this portable, cost-effective MIPCH sensor has also been achieved at the same range of OTC. With the increasing concentration of OTC in milk sample, the particle spacing of MIPCH sensor increased about 92 nm and the structural color of MIPCH changed from blue through green to orange. Image 1 • A novel 2D molecularly imprinted PC was developed for the fast screening of trace level residues of OTC in milk. • The detection could be realized by naked eyes through observing the diffraction ring or structural color. • The sensor also showed advantages in easy preparation and specificity towards the targets. [ABSTRACT FROM AUTHOR]