Polymerisable squaramide receptors for anion binding and sensing

A novel series of polymerisable squaramides has been synthesised in high yields using simple chemical reactions, and evaluated in the binding of anionic species. These vinyl monomers can be used as functional building blocks in co-polymerisations with a plethora of co-monomers or cross-linkers, grace to their compatibility with free-radical polymerisation reactions. Aromatic substituted squaramides were found to be the strongest receptors, while binding of certain anions was accompanied by a strong colour change, attributed to the de-protonation of the squaramide. The best performing squaramide monomers were incorporated in molecularly imprinted polymers (MIPs) targeting a model anion and their capacities and selectivity were evaluated by rebinding experiments. Polymers prepared using the new squaramide monomers were compared to urea based co-polymers, and were found to contain up to 80% of the theoretical maximum number of binding sites, an exceptionally high value compared to previous reports. Strong polymer colour changes were observed upon rebinding of certain anions, equivalent to those witnessed in solution, paving the way for application of such materials in anion sensing devices.Graphical abstract: Polymerisable squaramide receptors for anion binding and sensin

Tetrabutylammonium methacrylate as a novel receptor for selective extraction of sulphonylurea drugs from biological fluids using molecular imprinting

Tetrabutylammonium methacrylate introduced as functional monomer for the stoichiometric imprinting of sulfonylurea drug glibenclamide.</p

Molecularly imprinted polymers

Despite continuous advances in analytical instrumentation, sample preparation remains one of the most crucial steps in an analytical process. In this regard, efforts have been made to improve selectivity during extraction and/or subsequent cleanup of sample extracts. Molecularly imprinted polymers (MIPs) are robust sorbents with molecular recognition abilities, provided by the presence of a template during their synthesis, and thus are excellent materials to provide selectivity in sample preparation. In this chapter, factors affecting the synthesis of MIPs and their subsequent performance in sample preparation procedures are discussed. The use of MIPs in solid-phase extraction and solid-phase microextraction as well as recent incorporation into other extraction techniques such as matrix solid-phase dispersion and stir-bar sorptive extraction, among others, is described. The advantages and drawbacks of each methodology as well as the future trends are discussed

A novel Hamilton receptor monomer for the stoichiometric molecular imprinting of barbiturates

New molecularly imprinted polymers (MIPs) for the recognition of barbiturates were synthesised by “bulk” polymerisation. These polymers were prepared using pentobarbital as the template in combination with a novel Hamilton receptor functional monomer. The solution binding properties of the monomer were assessed by NMR titration experiments, showing high affinity for barbiturates and lower affinity for related compounds lacking the ability to form as many hydrogen bonds. The properties of the MIP were assessed via equilibrium rebinding experiments and in the chromatographic mode, and compared to the behaviour of a control non-imprinted polymer (NIP). The MIP showed a far higher population of binding sites with higher affinity than the NIP which was reflected in the chromatographic evaluation, where the template and a related barbiturate were not eluted from the MIP within 60 min, while their retention was weak on the NIP, leading to extremely high imprinting factors. Other analytes were weakly retained by MIP and NIP, with those presented an acceptor-donor-acceptor array of hydrogen bonding sites most retained. Preliminary molecular modelling studies support the hypothesis that the presence of the template in the MIP synthesis “chooses” the conformation of the functional monomer that is “locked in” during the polymerisation

A novel Hamilton receptor monomer for the stoichiometric molecular imprinting of barbiturates

New molecularly imprinted polymers (MIPs) for the recognition of barbiturates were synthesised by “bulk” polymerisation. These polymers were prepared using pentobarbital as the template in combination with a novel Hamilton receptor functional monomer. The solution binding properties of the monomer were assessed by NMR titration experiments, showing high affinity for barbiturates and lower affinity for related compounds lacking the ability to form as many hydrogen bonds. The properties of the MIP were assessed via equilibrium rebinding experiments and in the chromatographic mode, and compared to the behaviour of a control non-imprinted polymer (NIP). The MIP showed a far higher population of binding sites with higher affinity than the NIP which was reflected in the chromatographic evaluation, where the template and a related barbiturate were not eluted from the MIP within 60 min, while their retention was weak on the NIP, leading to extremely high imprinting factors. Other analytes were weakly retained by MIP and NIP, with those presented an acceptor-donor-acceptor array of hydrogen bonding sites most retained. Preliminary molecular modelling studies support the hypothesis that the presence of the template in the MIP synthesis “chooses” the conformation of the functional monomer that is “locked in” during the polymerisation

Molecularly Imprinted Polymers for the isolation of bioactive naphthoquinones from plant extracts

Molecularly Imprinted Polymers (MIPs) targeting shikonin, a potent antioxidant and wound healing agent, have been prepared using methacrylic acid (MAA) and 2-diethylaminoethyl methacrylate (DEAEMA) as functional monomers. An investigation of solution association between shikonin and both acidic and basic functional monomers by UV-Vis titrations, suggested stronger affinity towards the basic functionality. Strong inhibition of the co-polymerisation reaction of such basic monomers was observed, but was overcome by reduction of the amount of template used during polymer synthesis. Polymer morphology was severely impacted by the template’s radical scavenging behaviour as demonstrated by solid state NMR spectroscopy measurements. HPLC evaluation of the final materials in polar conditions revealed limited imprinting effects and selectivity, with the MAA polymers exhibiting marginally better performance. During application of the polymers as MI-SPE sorbents in non-polar solvents it was found that the DEAEMA based polymer was more selective towards shikonin compared to the MAA counterpart, while shikonin recoveries of up to 72% were achieved from hexane solutions of a commercial sample of shikonin, hexane extract of Alkanna tinctoria roots and a commercial pharmaceutical ointment

Biological phosphorus removal during high-rate, low-temperature, anaerobic digestion of wastewater

We report, for the first time, extensive biologically mediated phosphate removal from wastewater during high-rate anaerobic digestion (AD). A hybrid sludge bed/fixed-film (packed pumice stone) reactor was employed for low-temperature (12°C) anaerobic treatment of synthetic sewage wastewater. Successful phosphate removal from the wastewater (up to 78% of influent phosphate) was observed, mediated by biofilms in the reactor. Scanning electron microscopy and energy dispersive X-ray analysis revealed the accumulation of elemental phosphorus (~2%) within the sludge bed and fixed-film biofilms. 4', 6-diamidino-2-phenylindole (DAPI) staining indicated phosphorus accumulation was biological in nature and mediated through the formation of intracellular inorganic polyphosphate (polyP) granules within these biofilms. DAPI staining further indicated that polyP accumulation was rarely associated with free cells. Efficient and consistent chemical oxygen demand (COD) removal was recorded, throughout the 732-day trial, at applied organic loading rates between 0.4 and 1.5 kg COD m(-3) d(-1) and hydraulic retention times of 8-24 h, while phosphate removal efficiency ranged from 28 to 78% on average per phase. Analysis of protein hydrolysis kinetics and the methanogenic activity profiles of the biomass revealed the development, at 12°C, of active hydrolytic and methanogenic populations. Temporal microbial changes were monitored using Illumina MiSeq analysis of bacterial and archaeal 16S rRNA gene sequences. The dominant bacterial phyla present in the biomass at the conclusion of the trial were the Proteobacteria and Firmicutes and the dominant archaeal genus was Methanosaeta. Trichococcus and Flavobacterium populations, previously associated with low temperature protein degradation, developed in the reactor biomass. The presence of previously characterized polyphosphate accumulating organisms (PAOs) such as Rhodocyclus, Chromatiales, Actinobacter, and Acinetobacter was recorded at low numbers. However, it is unknown as yet if these were responsible for the luxury polyP uptake observed in this system. The possibility of efficient phosphate removal and recovery from wastewater during AD would represent a major advance in the scope for widespread application of anaerobic wastewater treatment technologies.This work was supported by the Science Foundation Ireland Charles Parsons Award (06_CP_E006), Investigator Programme Grant (14/IA/2371), Science Foundation Ireland (14/IA/2371), and the Irish Environmental Protection Agency (2014-W-LS-7). CJS is supported by Science Foundation Ireland Starting Investigator-COFUND fellowship (11/SIRG/B2159).peer-reviewe