Molecularly imprinted polymers for sample preparation: A review

Controlling substrate specificity and product regio- and stereo-selectivities of P450 enzymes without mutagenesis

P450 enzymes (P450s) are well known for their ability to oxidize unactivated CH bonds with high regio- and stereoselectivity. Hence, there is emerging interest in exploiting P450s as potential biocatalysts. Although bacterial P450s typically show higher activity than their mammalian counterparts, they tend to be more substrate selective. Most drug-metabolizing P450s on the other hand, display remarkable substrate promiscuity, yet product prediction remains challenging. Protein engineering is one established strategy to overcome these issues. A less explored, yet promising alternative involves substrate engineering. This review discusses the use of small molecules for controlling the substrate specificity and product selectivity of P450s. The focus is on two approaches, one taking advantage of non-covalent decoy molecules, and the other involving covalent substrate modifications.

Magnetic Molecularly Imprinted Polymers Based on Poly[2,2’-(p-oxidiphenylene)-5,5’-bibenzimidazole] (OPBI) for Selective Detection of Nonylphenol in Water Samples

Magnetic molecularly imprinted polymers (MMIPs) based on poly [2,2’-(p-oxidiphenylene)-5,5’-bibenzimidazole] (OPBI) composites were synthesized for the selective adsorption and detection of nonylphenol (NP) from water samples. During polymerization, Fe3O4@C was used as supporter and magnetic substance and OPBI not only was used as crosslinking agent but also functional monomer. Morphology of Fe3O4@C and MMIPs were investigated by scanning electron microscopy (SEM). The kinetics of adsorption followed the pseudo-first-order model. Selectivity of MMIPs was further demonstrated through HPLC analysis of the water samples, in which bisphenol A (BPA), phenol, 4-nitrophenol (4-NP) and tetrabromobisphenol (TBBPA) were dissolved respectively. The result showed that MMIPs had more effectively recognition capability of NP than other contrasts.

Past, Present and Future of Sensors in Food Production

Microbial contamination management is a crucial task in the food industry. Undesirable microbial spoilage in a modern food processing plant poses a risk to consumers' health, causing severe economic losses to the manufacturers and retailers, contributing to wastage of food and a concern to the world's food supply. The main goal of the quality management is to reduce the time interval between the filling and the detection of a microorganism before release, from several days, to minutes or, at most, hours. This would allow the food company to stop the production, limiting the damage to just a part of the entire batch, with considerable savings in terms of product value, thereby avoiding the utilization of raw materials, packaging and strongly reducing food waste. Sensor systems offer major advantages over current systems as they are versatile and affordable but need to be integrated in the existing processing systems as a process analytical control (PAT) tool. The desire for good selectivity, low cost, portable and usable at working sites, sufficiently rapid to be used at-line or on-line, and no sample preparation devices are required. The application of biosensors in the food industry still has to compete with the standard analytical techniques in terms of cost, performance and reliability.

An ion-imprinted functionalized SBA-15 adsorbent synthesized by surface imprinting technique via reversible addition-fragmentation chain transfer polymerization for selective removal of Ce(III) from aqueous solution

A novel Ce(III) ion-imprinted polymer (Ce(III)-IIP) has been prepared by surface imprinting technique with reversible addition-fragmentation chain transfer (RAFT) polymerization based on support matrix of SBA-15. The prepared adsorbent is characterized by FT-IR, XRD, SEM, TEM, nitrogen adsorption-desorption, GPC, and TGA. The results suggest that the surface imprinted polymer synthesized by RAFT is a thin layer. For adsorption experiments, Ce(III)-IIP is investigated to remove Ce(III) by column study at different flow rates, initial metal ion concentrations, and adsorption temperature. The dynamic kinetics analyses reveal that the overall adsorption process is successfully fitted with the pseudo-first-order kinetic model and the equilibrium time was 60 min. Meanwhile, the experimental data is in good agreement with Thomas model. Ce(III)-IIP has the excellent selectivity and regenerate property. Meanwhile, the proposed method has been successfully applied in the removal of Ce(III) in natural water samples with satisfactory results. All the results suggest that Ce(III)-IIP could be used as an excellent adsorbent for efficient removal of Ce(III) from aqueous solution.

Selective and simultaneous determination of NSAIDs in equine plasma by HPLC with molecularly imprinted solid-phase extraction

Background: Detection of nonsteroidal anti-inflammatory drugs (NSAIDs) in equine plasma is a significant analytical problem in veterinary anti-doping controls. Results: A new HPLC method coupled to selective extraction with molecularly imprinted polymers was developed for the simultaneous determination in equine plasma of the NSAIDs phenylbutazone, flunixin, oxyphenbutazone, ketoprofen and naproxen. The analytical performances of the method have been evaluated both in standard solutions and equine plasma samples. Recovery: Molecularly imprinted polymers solid-phase extraction for all NSAIDs was >94% with intra-day values below 15.0% and inter-day values below 20%. Method quantification limit was 0.01 μg/ml. Conclusion: The developed method could be considered as a useful alternative to existing screening methods for the determination of NSAIDs in the context of studies of pharmacokinetics and anti-doping controls.

Novel dummy molecularly imprinted polymers for matrix solid-phase dispersion extraction of eight fluoroquinolones from fish samples

A series of novel dummy molecularly imprinted polymers (DMIPs) were prepared as highly class-selective sorbents for fluoroquinolones. A non-poisonous dummy template, daidzein, was used for the first time to create specific molecular recognition sites for fluoroquinolones in the synthesized polymers. The influence of porogen polarity on dummy molecular imprinting effect was studied. The DMIP prepared using dimethylsulfoxide-acetonitrile (1:1.8, v/v) as porogen achieved the highest imprinting factors (IF) for fluoroquinolones over a range of IF 13.4-84.0. This DMIP was then used for selective extraction of eight fluoroquinolones (fleroxacin, ofloxacin, norfloxacin, pefloxacin, ciprofloxacin, lomefloxacin, enrofloxacin and gatifloxacin) from fish samples based on dummy molecularly imprinted matrix solid-phase dispersion (DMI-MSPD). The extracted fluoroquinolones were subsequently analyzed by high-performance liquid chromatography (HPLC) equipped with a fluorescence detector (FLD). The developed method had acceptable recoveries (64.4-102.7%) and precision (RSDs: 1.7-8.5%, n=5) for determination of fluoroquinolones in fish samples fortified at levels of 10 and 100ngg(-1). The limits of detection (LODs) for identification of eight fluoroquinolones ranged between 0.06 and 0.22ngg(-1). The results demonstrated great potential of the optimized method for sample preparation in routine analysis of trace fluoroquinolones in fish samples.

Selective solid phase extraction of copper using a new Cu(II)-imprinted polymer and determination by inductively coupled plasma optical emission spectroscopy (ICP-OES)

This work reports the preparation of a novel Cu(II)-ion imprinted polymer using 2-thiozylmethacrylamide (TMA) for on-line preconcentration of Cu(II) prior to its determination by inductively coupled optical emission spectroscopy (ICP-OES). Cu(II)-TMA monomer (complex) was synthesized and copolymerized via bulk polymerization method in the presence of ethyleneglycoldimethacrylate cross-linker. The resulting polymer was washed with 5% (v/v) HNO₃ to remove Cu(II) ions and then with water until a neutral pH. The ion imprinted polymer was characterized by FT-IR and scanning electron microscopy. The experimental conditions were optimized for on-line preconcentration of Cu(II) using a minicolumn of ion imprinted polymer (IIP). Quantitative retention was achieved between pH 5.0 and 6.0, whereas the recoveries for the non-imprinted polymer (NIP) were about 61%. The IIP showed about 30 times higher selectivity to Cu(II) in comparison to NIP. The IIP also exhibited excellent selectivity for Cu(II) against the competing transition and heavy metal ions, including Cd, Co, Cr, Fe, Mn, Ni, Pb and Zn. Computational calculations revealed that the selectivity of IIP was mediated by the stability of Cu(II)-TMA complex which was far more stable than those of Co(II), Ni(II) and Zn(II) that have similar charge and ionic radii to Cu(II). A volume of 10 mL sample solution was loaded onto the column at 4.0 mL min^-1 by using a sequential injection system (FIALab 3200) followed by elution with 1.0 mL of 2% (v/v) HNO₃. The relative standard deviation (RSD) and limit of detection (LOD, 3s) of the method were 3.2% and 0.4 μg L^-1, respectively. The method was successfully applied to determination of Cu(II) in fish otoliths (CRM 22), bone ash (SRM 1400) and coastal seawater and estuarine water samples.

Learning from nature - novel synthetic biology approaches for biomaterial design

Many biomaterials constructed today are complex chemical structures that incorporate biologically active components derived from nature, but the field can still be said to be in its infancy. The need for materials that bring sophisticated properties of structure, dynamics and function to medical and non-medical applications will only grow. Increasing appreciation of the functionality of biological systems has caused biomaterials researchers to consider nature for design inspiration, and many examples exist of the use of biomolecular motifs. Yet evolution, nature's only engine for the creation of new designs, has been largely ignored by the biomaterials community. Molecular evolution is an emerging tool that enables one to apply nature's engineering principles to non-natural situations using variation and selection. The purpose of this review is to highlight the most recent advances in the use of molecular evolution in synthetic biology applications for biomaterial engineering, and to discuss some of the areas in which this approach may be successfully applied in the future.

Developments and trends of molecularly imprinted solid-phase microextraction

This review focuses on a solid-phase microextraction (SPME) method coupled with molecularly imprinted polymers (MIPs), namely molecularly imprinted solid-phase microextraction (MISPME). The first two sections discuss the summaries of conventional SPME and MIPs. The third section reviews the development of MISPME in past years, including the preparation of MISPME, and the applications to compounds in real samples.

Highly effective removal of 2,4-dinitrophenolic from surface water and wastewater samples using hydrophilic molecularly imprinted polymers

Novel hydrophilic molecularly imprinted polymers (MIPs) with high adsorption capacity were used as the sorbents to remove 2,4-dinitrophenol (2,4-DNP) from surface water and wastewater samples. Kinetic studies, dynamic adsorption and selectivity experiments of hydrophilic MIPs were investigated in this study. The results indicated that the maximum adsorption capacity of 2,4-DNP on hydrophilic MIPs was 138.9 mg g(-1) and kinetic experimental data were described by the pseudo-second-order model. Furthermore, the effects of flow rate, initial concentration, pH value, and humic acid on the removal efficiency of 2,4-DNP were optimized. Compared with the active carbon, carbon nanotube, C18 sorbents and common MIPs, the removal efficiency of hydrophilic MIPs (100 mg) was very high with all above 92 % even though the sampling volume was more than 1 L. Investigated results of five times adsorption-desorption cycles indicated hydrophilic MIPs were high stability. In a word, the obtained results demonstrated that hydrophilic MIPs could be used as the effective sorbents for 2,4-DNP removal in practical application.

Synthesis and evaluation of molecularly imprinted silica gel for 2-hydroxybenzoic Acid in aqueous solution

A molecularly imprinted silica gel sorbent for selective removal of 2-Hydroxybenzoic acid (2-HA) was prepared by a surface imprinting technique with a sol-gel process. The 2-HA molecularly imprinted silica gel (2-HA-MISG) sorbent was evaluated by various parameters, including the influence of pH, static, kinetic adsorption and selectivity experiments. The optimum adsorption capacity to the 2-HA appeared to be around pH 2 by the polymer. Morevoer, the imprinted sorbent displayed fast uptake kinetics, obtained within 20 min. The adsorption capacity of the 2-HA-MISG (76.2 mg g-1) was higher than that of the non-imprinted silica gel (NISG) (42.58 mg g-1). This indicates that the 2-HA-MISG offers a higher affinity for 2-HA than the NISG. The polymer displays good selectivity and exhibits good reusability. Experimental results show the potential of molecularly imprinted silica sorbent for selective removal of 2-HA.