Recognitive nano-thin-film composite beads for the enantiomeric resolution of the metastatic breast cancer drug aminoglutethimide.

Straightforward crushing and sieving bulk polymeric R-aminoglutethimide-imprinted materials were prepared by classical free radical polymerization, whereas nano thin walled grafted imprinted materials were prepared using RAFT mediated control polymerization technique. A stoichiometric non-covalent approach based on a triply hydrogen bonding functional monomer-template 1:1 complex (K=599mol(-1)L(-1)) led to chiral selectors far outperforming previously used selectors for resolving this racemate. The recognitive materials produced here (enantioselectivity factors, α∼10) also have no match within the previously reported enantioselective imprinted polymers (α 1.2-4.5). We here demonstrate a potentially generic solution to produce good quality grafted MIPs for templates interacting by hydrogen bonding alone, relying on solvent polarity tuning, significantly extending the range of templates compatible with this format.

Vapor-phase testing of the memory-effects in benzene- and toluene-imprinted polymers conditioned at elevated temperature.

The preparation of polymers imprinted with common aromatic solvents such as benzene and toluene is an under-exploited subject of research. The present study was aimed at the understanding of whether true solvent memory effects can be achieved by molecular imprinting, as well as if they are stable at elevated temperature. A set of copolymers, comprising low and high cross-linking levels, was prepared from four different combinations of functional monomer and cross-linker, namely methacrylic acid (MAA)/ethylene glycol dimethacrylate (EGDMA), methyl methacrylate (MMA)/EGDMA, MAA/divinyl benzene (DVB) and MMA/DVB. Each possible combination was prepared separately in benzene, toluene and acetonitrile. The obtained materials were applied as coatings onto nickel-titanium (Ni-Ti) alloy wires which were incorporated into solid-phase microextraction devices and finally tested for their ability to competitively adsorb vapors from the headspace of an aqueous solution containing a few volatile organic compounds. Porosity analysis showed that, regardless of the solvent used, only a high cross-linking level permitted the preparation of mesoporous copolymers (BJH radius typically in the range 13-15 nm), a requirement for providing accessibility to the targeted nanoscale-imprinted cavities. A noticeable exception was, however, observed for the MMA/DVB copolymers which exhibited much diminished BJH radius. The porosity data correlated well with the extraction profiles found, which suggested the presence of benzene-imprinted sites in all the highly cross-linked copolymers prepared in benzene, except for the MMA/DVB copolymers. Concerning the effect of an elevated conditioning temperature on the memory-effects created by the imprinting process, the results were clearly indicative that the tested copolymers, including the more robust highly cross-linked ones, are not suitable for high temperature applications such as solid-phase microextraction coupled to gas chromatography.

Imidazolium-based functional monomers for the imprinting of the anti-inflammatory drug naproxen: comparison of acrylic and sol-gel approaches.

Imidazolium-based monomers were, for the first time, employed in a comprehensive investigation of the molecular imprinting process of naproxen in both acrylic and sol-gel tridimensional networks. To this end, molecularly imprinted polymer (MIP) and xerogel (MIX) were both optimized for performance, by testing different porogen, template speciation and component ratios. The developed imprints were characterized for their pore properties (nitrogen adsorption analysis), site heterogeneity, binding properties and other performance parameters such as the imprinting factor, selectivity (HPLC column tests), column efficiency and mass transfer kinetics (frontal analysis study). MIP exhibited mesoporosity (Dp 29nm), whereas MIX did not, which was reflected in both the lower number of accessible imprinted sites (4.9µmol/g versus 3.7µmol/g) and the slower binding/dissociation in MIX. The naproxen/ibuprofen selectivity ratio was estimated as 6.2 for the MIX and 2.5 for the MIP. Given the high importance of capacity and fast mass transfer in typical applications of imprinted materials, and the satisfactory selectivity of MIP, it can be concluded that the acrylic approach was globally the most advantageous. Still, the remarkably high selectivity of MIX and its reasonable capacity demonstrate that future work devoted to further optimization of both formats is worthwhile.

An artificial estrogen receptor through combinatorial imprinting.

Polymeric sorbents targeting endocrine-disrupting estrogen active compounds (EAC) were prepared by terpolymer imprinting using 17ß-estradiol (E2) as template. From a group of eight functional monomers representing Brønsted acids, bases, hydrogen-bond donors and acceptors, as well as π-interacting monomers, a terpolymer library that comprises all possible binary combinations of the functional monomers was prepared. Binding tests revealed that imprinted polymers exhibit a markedly higher affinity for E2 compared to nonimprinted polymers (NIPs) or polymers prepared by using single functional monomers. A combination of methacrylic acid (MAA) and p-vinylbenzoic acid offered a particularly promising lead polymer, displaying an imprinting factor of 17 versus 2.4 for a benchmark polymer prepared by using only MAA as functional monomer. The saturation capacities ascribed to imprinted sites were four to five times higher for this polymer compared to previously reported imprinted polymers. NMR titrations and molecular dynamics simulations corroborated these results, indicating an orthogonal preference of the two functional monomers with respect to the E2 3-OH and 17-OH groups. The optimized polymer exhibited a retentivity for EACs that correlates with their inhibitory effect on the natural receptor. By using the optimized molecularly imprinted polymers (MIPs) in a model water-purification system, they were capable of completely removing ppb levels of a small group of EACs from water. This is in contrast to the performance of nonimprinted polymers and well-established sorbents for water purification (e.g., active carbon), which still contained detectable amounts of the compounds after treatment.

Polymeric complements to the Alzheimer's disease biomarker ß-amyloid isoforms Aß1-40 and Aß1-42 for blood serum analysis under denaturing conditions.

Treatment of Alzheimer's disease (AD) is plagued by a lack of practical and reliable methods allowing early diagnosis of the disease. We here demonstrate that robust receptors prepared by molecular imprinting successfully address current limitations of biologically derived receptors in displaying affinity for hydrophobic peptide biomarkers for AD under denaturing conditions. C-terminal epitope-imprinted polymers showing enhanced binding affinity for Aß1-42 were first identified from a 96-polymer combinatorial library. This information was then used to synthesize molecularly imprinted polymers for both of the ß-amyloid (Aß) isoforms and a corresponding nonimprinted polymer. A solid-phase extraction method was developed to be compatible with sample loading under conditions of complete protein denaturation. This resulted in a method capable of quantitatively and selectively enriching a shorter C-terminal peptide corresponding to the sequences Aß33-40 and Aß33-42 as well as the full-length sequence Aß1-40 and Aß1-42 from a 4 M guanidinum chloride solution. Application of the method to serum allowed selective, high-recovery extraction of both biomarkers at spiking levels marginally higher than clinically relevant concentrations found in cerebrospinal fluid.

Chromatographic comparison of bupivacaine imprinted polymers prepared in crushed monolith, microsphere, silica-based composite and capillary monolith formats.

A comprehensive comparison of five chromatographic stationary phases based on molecularly imprinted polymers is presented. Efficiency, imprinting factors, water compatibility and batch-to-batch reproducibility are discussed for crushed monolith, microspheres, two silica-based composites and capillary monoliths, all imprinted with the local anaesthetic bupivacaine. Synthesis protocol and chromatographic test conditions have been kept fixed within certain limits, in order to provide further insight into the strengths and weaknesses of the different formats. Excluding microparticles, all formats give satisfactory performance, especially in aqueous mobile phases. An assessment of batch-to-batch reproducibility in different mobile phases adds further value to this comparison study.

A field evaluation of a piezo-optical dosimeter for environmental monitoring of nitrogen dioxide.

Measurements of 8-hour time-weighted average NO(2) concentrations are reported at 7 different locations in the region of Dunkirk over 5 consecutive days using PiezOptic monitoring badges previously calibrated for the range 0-70 ppb together with data from chemiluminescent analysers in 5 sites (4 fixed and one mobile). The latter facilities also provided data on ozone and NO concentrations and meteorological conditions. Daily averages from the two pairs of badges in different types of sampling cover in each site have been compared with data from the chemiluminescent analysers, and found largely to agree within error margins of +/-30%. Although NO(2) and ozone concentrations were low, rendering detailed discussion impossible, the general features followed expected patterns.

Water-compatible molecularly imprinted polymers obtained via high-throughput synthesis and experimental design.

A technique allowing high-throughput synthesis and evaluation of molecularly imprinted polymer sorbents at a reduced scale (mini-MIPs) was developed and used for the optimization of MIPs for use in pure aqueous environments. The technique incorporated a 4-port liquid-handling robot for the rapid dispensing of monomers, templates, solvents and initiator into the reaction vessels of a 96-well plate. A library of 80 polymers, each ca. 50 mg, could thus be prepared in 24 h. The MIP rebinding capacity and selectivity could be rapidly assessed in the batch mode by quantifying nonbound fractions in parallel using a UV monochromator plate reader. This allowed a complete evaluation of the binding characteristics of an 80 polymer library in approximately 1 week. With the objective of optimizing a polymer imprinted with the local anaesthetic Bupivacaine for use in pure aqueous systems, a polymer library was prepared by varying the original poly(MAA-co-EDMA) MIP composition. The variable factors were the added amount of the hydrophilic comonomer, 2-hydroxyethyl methacrylate (HEMA), the cross-linking ratio, and the porogen. This optimization resulted in polymers showing high imprinting factors (IF = K(MIP)/K(NIP)) in water as a result, mainly, of reduced binding to the nonimprinted polymer. Normal scale batches of these materials showed strong retention of the template and low nonspecific binding when assessed as chromatographic stationary phases using pure phosphate buffer, pH 7.4, as mobile phase, by equilibrium batch rebinding experiments and as sorbents for extractions of the analyte from blood plasma samples.