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The selectivity and rebinding capacity of molecularly imprinted polymers selective for propranolol (1) using the room temperature ionic liquids [BMIM][BF4], [BMIM][PF6], [HMIM][PF6] and [OMIM][PF6] and CHCl3 were examined. The observed IF (imprinting factor) values for MIPBF4, MIPPF6 and MIPCHCl3 were 1.0, 1.98 and 4.64, respectively. The longer chain HMIM and OMIM systems returned lower IF values of 1.1 and 2.3, respectively. MIPPF6 also showed a 25% binding capacity reduction vs. MIPCHCl3 (5 μmol g(−1)vs. 7 μmol g(−1) respectively). MIPCHCl3 and MIPPF6 differed in terms of BET surface area (306 m(2) g(−1)vs. 185 m(2) g(−1)), pore size (1.10 and 2.19 nm vs. 0.97 and 7.06 nm), the relative number of pores (Type A: 10.4 vs. 7.5%; Type B: 8.5 vs. 3.0%), and surface zeta potential (−37.9 mV vs. −20.3 mV). The MIP specificity for 1 was examined by selective rebinding studies with caffeine (2) and ephedrine (3). MIPPF6 rebound higher quantities of 2 than MIPCHCl3, but this was largely due to non-specific binding. Both MIPCHCl3 and MIPPF6 showed a higher affinity for 3 than for 2. Reduction in the Room Temperature Ionic Liquid (RTIL) porogen volume had little impact on the polymer morphology, but did result in a modest decrease in IF from 2.6 to 2.3 and in the binding capacity (30% to 19%). MIPCHCl3 retained the highest template specificity on rebinding from CHCl3 (IF = 4.6) dropping to IF = 0.6 in MeOH/[BMIM][PF6]. The MIPCHCl3 binding capacity remained constant using CHCl3, CH2Cl2 and MeOH (46–52%), dropped to 6% on addition of [BMIM][PF6] and increased to 83% in H2O (but at the expense of specificity with IFH2O = 1.4). MIPPF6 rebinding from MeOH saw an increase in specific rebinding to IF = 4.9 and also an increase in binding capacity to 48% when rebinding 1 from MeOH and to 42% and 45% with H2O and CH2Cl2, respectively, although in the latter case the increased capacity was at the cost of specificity with IFCH2Cl2 = 1.2. Overall the MIPPF6 capacity and specificity were enhanced on addition of MeOH.

Beta-Glucosidase has been chosen as a model biomolecule to establish a general protocol for binding enzymes on both ferromagnetic and superparamagnetic nano-particles for sensing applications. Using EDC (1-(3-dimethyl-aminopropyl)-3-ethylcarbodiimide) or SMCC (Succinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate) as coupling agents, we compared two different methods for the fabrication of enzyme-decorated magnetic nanoparticles. We identified the best conditions for the preparation of a responsive bioactive magnetic system comparing different covalent bio-grafting protocols. The enzymatic test has been performed using beta-Glucosidase. The systems were characterized using scanning electron microscopy, infrared spectroscopy, and the enzyme loading was measured by a glucose assay in the presence of the enzyme-decorated magnetic particles. Although the faster response of ferromagnetic particles to the magnetic field, the assay results suggested that the superparamagnetic particles are more efficient carriers. In fact, the best enzymatic activity was measured on superparamagnetic systems that have the further advantage of preventing aggregation induced by the residual magnetization. Hence, beta-Glucosidase coated magnetic nanospheres could provide an attractive system suitable for the cleavage and the rapid evaluation of glycoside levels in natural products, measuring the liberated glucose without the need for specialised instrumentation. Moreover, the magnetic particles allow the subsequent collection of enzymes for further analysis, such as its use in portable fast screening kits or devices.

Long-term environmental monitoring of organic compounds in natural waters requires sensors that respond reproducibly and linearly over a wide concentration range, and do not degrade with time. Although polymer coated piezoelectric based sensors have been widely used to detect hydrocarbons in aqueous solution, very little information exists regarding their stability and suitability over extended periods in water. In this investigation, the influence of water aging on the response of various polymer membranes [polybutadiene (PB), polyisobutylene (PIB), polystyrene (PS), polystyrene-co-butadiene (PSB)] was studied using the quartz crystal microbalance (QCM). QCM measurements revealed a modest increase in sensitivity towards toluene for PB and PIB membranes at concentrations above 90 ppm after aging in water for 4 days. In contrast, the sensitivity of PS and PSB coated QCM sensors depended significantly on the toluene concentration and increased considerably at concentrations above 90 ppm after aging in water for 4 days. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) showed that there is a change in the sorption mechanism at higher toluene levels for PS and PSB. Positron annihilation lifetime spectroscopy (PALS) studies were performed to investigate the free volume properties of all polymers and to monitor any changes in the free volume size and distribution due to water and toluene exposure. The PALS did not detect any considerable variation in the free volume properties of the polymer films as a function of solution composition and soaking time, implying that viscoelastic and/or interfacial processes (i.e. surface area changes) are probably responsible for variations in the QCM sensitivity at high hydrocarbon concentrations. The results suggest that polymer membrane conditioning in water is an issue that needs to be considered when performing QCM measurements in the aqueous phase. In addition, the study shows that the hydrocarbon response is concentration dependant for polymers with a high glass transition temperature, and this feature is often neglected when comparing sensor sensitivity in the literature., (Crown Copyright © 2011. Published by Elsevier B.V. All rights reserved.)