Molecularly imprinted polymers for the determination of a pharmaceutical development compound in plasma using 96-well MISPE technology

Sensitive and selective simultaneous biosensing of nandrolone and testosterone as two anabolic steroids by a novel biosensor assisted by second-order calibration

Recently, our research group have focused on an interesting project in which a novel dual template molecularly imprinted (DTMIP) biosensor was fabricated and assisted by second-order differential pulse voltammetric (DPV) data for simultaneous determination of nandrolone decanoate (ND) and testosterone decanoate (TS). An indium tin oxide (ITO) was modified with multiwalled carbon nanotubes-graphene-ionic liquid (MWCNT-Gr-IL) and then, the fullerene C₆₀ was casted onto the surface of MWCNT-Gr-IL/ITO and electrochemically reduced. Finally, DTMIPs were electrosynthesized by electropolymerization of 4-aminobenzoic acid (ABA) as monomer with ND and TS as template molecules to obtain the final structure of the biosensor (DTMIP/C₆₀/MWCNT-Gr-IL/ITO). Structure of the biosensor was electrochemically and microscopically characterized. The ND and TS generated two severely overlapped DPVs at the surface of the biosensor which forced us to assist the biosensor with three-way calibration by second-order DPV data to simultaneous determine them. Two second-order algorithms including multivariate curve resolution alternating least squares (MCR-ALS) and parallel factor analysis2 (PARAFAC2) were used to build second-order calibration models and evaluation of their performance in the analysis of synthetic samples showed more superiority of the MCR-ALS than PARAFC2 which motivated us to select PARAFC2 for the analysis of urine samples as real cases. Application of the biosensor assisted by PARAFC2 for the analysis of urine samples towards simultaneous determination of ND and TS was successful.

Optimising factors affecting solid phase extraction performances of molecular imprinted polymer as recent sample preparation technique

Molecular imprinted solid-phase extraction is the technique that uses molecular imprinted polymer as the sorbent in solid phase extraction. Molecular imprinted solid-phase extraction is effective and efficient for the extraction process and cleaning as compared with solid phase extraction (SPE) without molecular imprinted polymer. The complexity of variables in molecular imprinted solid-phase extraction arise as problems in the analysis, therefore it is necessary to optimize the extraction conditions of molecular imprinted solid-phase extraction. To achieve the sorption equilibrium and achieve the shortest time, certain parameters such as contact time, ion strength of sample, pH of sample, amount of sorbent, sample flow rate, addition of salt and buffer solution, washing solvent, elution solvent, and loading solvent need to be optimized. The selection of suitable properties and quantities of each factor greatly affect the formation of appropriate interactions between the sorbent and analytes. Percentage recovery is also influenced by formation of the appropriate bonds, sample flow rates, extraction time, salt addition, and sorbent mass. Therefore, in the future, molecular imprinted solid-phase extraction optimization has to consider and adjust various factors reviewed in this paper to form appropriate interactions between the absorbent and target molecules which have an impact on the optimal results.

Molecular imprinting science and technology: a survey of the literature for the years 2004-2011

Herein, we present a survey of the literature covering the development of molecular imprinting science and technology over the years 2004-2011. In total, 3779 references to the original papers, reviews, edited volumes and monographs from this period are included, along with recently identified uncited materials from prior to 2004, which were omitted in the first instalment of this series covering the years 1930-2003. In the presentation of the assembled references, a section presenting reviews and monographs covering the area is followed by sections describing fundamental aspects of molecular imprinting including the development of novel polymer formats. Thereafter, literature describing efforts to apply these polymeric materials to a range of application areas is presented. Current trends and areas of rapid development are discussed.

The selective binding character of a molecular imprinted particle for Bisphenol A from water

A molecular imprinted particle for Bisphenol A (BPA-MIP) was successfully used for selective recognition of BPA in the water. The contaminants such as 3, 3', 5, 5'-Tetrabromobisphenol A (TBBPA), phenol and phenol red (PSP) were selected as the latent interferon to investigate the selectivity. The binding efficiencies of BPA-MIP for different phenols were explored at various initial concentrations in the single and mixed water. Various selective parameters such as Kd, K and K' of BPA-MIP for BPA were calculated. The influences of humic acid (HA) and common ions on the BPA binding were investigated. A physical model was proposed to illustrate the selective binding performance. The results showed that BPA-MIP possessed strong selectivity for BPA in competitive water, while the other similar phenols had the influence for BPA binding at the order of TBBPA > phenol > PSP. The HA and common ions indicated little effect on the BPA binding process onto BPA-MIP. It was found that the molecular geometry and the hydrogen bonding interactions between the hydroxyl and carboxyl played an important role in recognizing the target molecular in the binding process.

Molecularly Imprinted Hydrogels for Affinity-controlled and Stimuli-responsive Drug Delivery

The performance of smart or intelligent hydrogels as drug-delivery systems (DDSs) can be notably improved if the network is endowed with high-affinity receptors for the therapeutic molecule. Conventional molecular imprinting technology aims to create tailored binding pockets (artificial receptors) in the structure of rigid polymers by means of a template polymerization, in which the target molecules themselves induce a specific arrangement of the functional monomers during polymer synthesis. Adaptation of this technology to hydrogel synthesis implicates the optimization of the imprinting pocket to be able to recover the high-affinity conformation when distorted by swelling or after the action of a stimulus. This chapter analyzes the implementation of the molecular imprinting technology to the synthesis of both non-responsive and responsive loosely cross-linked hydrogels, and provides recent examples of the suitability of the imprinted networks to attain affinity-controlled, activation-controlled or stimuli-triggered drug and protein release.

Synthesis by precipitation polymerization of molecularly imprinted polymer for the selective extraction of diclofenac from water samples

A molecularly imprinted polymer (MIP) was synthesized by precipitation polymerization using diclofenac (DFC) as a template, 2-vinylpyridine (2-VP) as functional monomer, ethylene glycol dimethacrylate (EGDMA) as cross-linker, and toluene as porogen. The MIP showed outstanding affinity toward DFC in aqueous solution with a binding site capacity (Q(max)) of 324.8 mg/g (1.09 mmol/g) and was used as solid-phase extraction (SPE) material for the quantitative enrichment of DFC in environmental water samples and off-line coupled to a reversed-phase HPLC/DAD. Various parameters including washing solvent, elution solvent and breakthrough volume affecting the extraction efficiency of the polymers have been evaluated to achieve the selective preconcentration of DFC from water samples and to reduce non-specific interactions. Recoveries of DFC extracted from tap water, river water and wastewater samples were higher than 95%, and no significant DFC recovery difference was obtained among the different water matrix. The stability of MIP was tested by consecutive percolation of water sample, and it was shown that the performance of the MIP did not vary even after 30 adsorption and desorption cycles. Furthermore, the MISPE was used for the analysis of DFC in river water and wastewater samples and revealed DFC concentrations of 0.69±0.002 μg/L (n=3) and 0.31±0.004μg/L (n=3), respectively. The results were in good agreement with corresponding LC-MS/MS data.

Molecularly imprinted solid-phase extraction of matrine from radix Sophorae tonkinensis

In the study, molecularly imprinted polymers (MIPs) with special molecular recognition properties of matrine (MAT) were prepared in our lab, using melamine-urea-formaldehyde (MUF) as the functional monomer and matrine as the template. An equilibrium binding experiment was performed to investigate the binding ability of the MIPs, and indicated that the MIPs had a high adsorption and good elution ability to the target molecule MAT, when the template/functional monomer ratio (T/M) was 5 mg g(-1). Scatchard analysis and isothermal equilibrium adsorption indicated that only one kind of binding site had existed in the MAT-imprinted polymers with its dissociation constants estimated to be 3.31 × 10(-4) mol L(-1) (200-400 mesh (inch(-1))) and 6.83 × 10(-4) mol L(-1) (over 400 mesh (inch(-1))) depending on the mesh of the MIPs. MAT purification and elution experiments were carried out using MIPs as the solid-phase extraction (MISPE) sorbent, and acetone, water, and chloroform as the elution solvents. The results demonstrated that MIPs achieved their highest adsorption capability after treatment with alkaline solution, while acetone was the most efficient elution solvent. Then, a crude extraction of matrine in radix Sophorae tonkinensis was performed using these MIPs as the separation medium. The results showed that MIPs had a high MAT selectivity, and the amount of matrine content obtained by MISPE was 1.4-fold to that obtained by liquid-liquid extraction.

Molecularly imprinted polymers: synthetic receptors in bioanalysis

Molecularly imprinted polymers (MIPs) are tailor-made synthetic materials possessing specific cavities designed for a target molecule. Since they recognise their target analyte with affinities and selectivities comparable to those of antibody-antigen, enzyme-substrate and ligand-receptor interactions, they are often referred to as synthetic receptors or plastic antibodies. In this review, we describe the great potential and recent developments of MIPs in affinity separations, with emphasis on their application to the solid-phase extraction (SPE) of analytes from complex matrices. Research efforts made in this field to obtain water-compatible polymers for their applicability in aqueous environments are described. We particularly discuss problems encountered in the use of MIPs in SPE and the attempts carried out to improve their efficiency.

Molecularly imprinted polymers and their application in solid phase extraction

Solid phase extraction is routinely used in many different areas of analytical chemistry. Some of the main fields are environmental, biological, and food chemistry, where cleaning and pre-concentration of the sample are important steps in the analytical protocol. Molecularly imprinted polymers (MIPs) have attracted attention because they show promise as compound-selective or group-selective media. The application of these synthetic polymers as sorbents allows not only pre-concentration and cleaning of the sample but also selective extraction of the target analyte, which is important, particularly when the sample is complex and impurities can interfere with quantification. This review surveys the selectivity of MIPs in solid phase extraction of various kinds of analytes.

Selection of imprinted nanoparticles by affinity chromatography

Soluble molecularly imprinted nanoparticles were synthesised via iniferter initiated polymerisation and separated by size via gel permeation chromatography. Subsequent fractionation of these particles by affinity chromatography allowed the separation of high affinity fractions from the mixture of nanoparticles. Fractions selected this way possess affinity similar to that of natural antibodies (K(d) 6.6x10(-8)) M and were also able to discriminate between related functional analogues of the template.

Preparation of molecularly imprinted solid phase extraction using bensulfuron-methyl imprinted polymer and clean-up for the sulfonylurea-herbicides in soybean

A pre-treatment methodology based on the molecularly imprinted solid phase extraction (MI-SPE) procedure was developed for the determination of bensulfuron-methyl (BSM), tribenuron-methyl (TBM), metsulfuron-methyl (MSM) and nicosulfuron (NS) in soybean samples. A molecular imprinted polymer (MIP) was prepared by precipitation polymerization using BSM as the template molecule, alpha-methacrylic acid (MAA) as the functional monomer, trimethylolpropane trimethacrylate (TRIM) as the cross-linker and dichloromethane as the porogen. The binding behaviors of the template BSM and its analogues on the MIP were evaluated by high performance liquid chromatography (HPLC). Then, solid phase extraction (SPE) with a BSM molecularly imprinted polymer (BSM-MIP) as adsorbent was investigated and the optimum loading, washing, and eluting conditions for MI-SPE of the selected BSM, MSM, TBM, and NS were established. The optimized MI-SPE procedure was used to extract the sulfonylureas and a high recovery was obtained in the soybean samples.

Preparation and evaluation of solid-phase microextraction fibers based on monolithic molecularly imprinted polymers for selective extraction of diacetylmorphine and analogous compounds

All of the studies on solid-phase microextraction based on molecularly imprinted polymers up to now have been carried out on the synthesis of the polymer on the surface of the fiber which is brittle and the polymer coating strips during handling. The objective of this study was to develop a method for fabrication of a monolithic and robust solid-phase microextraction fiber on the basis of molecularly imprinted polymer for selective extraction of diacetylmorphine and its structural analogues followed by their GC or GC/MS analysis. A fiber was produced by copolymerization of methacrylic acid-ethylene glycol dimethacrylate imprinted with diacetylmorphine. The effective factors influencing the polymerization have been investigated and are detailed here. Also, the influences of pH, extraction time and temperature on the extraction efficiency of analytes were investigated. The prepared fiber was thermally stable up to 300 degrees C which has vital importance in SPME coupled with GC or GC/MS. The adsorption isotherm modeling was performed by fitting the data of studied compounds to bi-Langmuir isotherm model. The evaluated equilibrium constants for diacetylmorphine were 0.011 and 1824.72 microM(-1), and the number of binding sites was 170.37 and 4.64 nmolg(-1), respectively. This fiber was successfully used for extraction of template molecule from aqueous solution and further analysis with GC or GC/MS. The high extraction efficiency was obtained for diacetylmorphine, 6-monoacetylcodeine, and 6-monoacetylmorphine, yielding the detection limits of 300, 47, and 1 ngmL(-1), respectively.

On-line clean-up and screening of oxacillin and cloxacillin in human urine and plasma with a weak ion exchange monolithic column

A weak ion exchange monolithic column prepared by modifying the GMA-MAA-EDMA (glycidyl methacrylate-methacrylic acid-ethylene glycol dimethacrylate) monoliths with ethylenediamine was applied to remove matrix compounds in biological fluid. Using this monolithic column, on-line clean-up and screening of oxacillin and cloxacillin in human urine and plasma samples had been investigated. Chromatography was performed by reversed-phase HPLC on a C(18) column with ultraviolet detection at 225 nm. Results showed that the ion exchange monolithic column could be used for deproteinization and retaining oxacillin and cloxacillin in human urine and plasma, which provided a simple and fast method for assaying drugs in human urine and plasma.

Evaluation of water-compatible molecularly imprinted polymers as solid-phase extraction sorbents for the selective extraction of sildenafil and its desmethyl metabolite from plasma samples

The evaluation of molecularly imprinted polymers (MIPs) as selective sorbents for the solid-phase extraction of sildenafil and its principal metabolite, desmethylsildenafil, was investigated. Two MIPs were synthesised using structural analogues of sildenafil as templates, and a comparison of the performance of the two MIP sorbents in organic and aqueous media was performed. Additionally, the feasibility of applying molecularly imprinted solid-phase extraction (MISPE) to the clean-up of plasma samples containing sildenafil and desmethylsildenafil was investigated. A preliminary, quantitative MISPE for the determination of both compounds in plasma was also performed. The results showed that the MIPs used for the selective extraction of sildenafil gave better compound recovery when aqueous samples were used in comparison to organic-based samples. A preliminary, quantitative MISPE of sildenafil and desmethylsildenafil indicated that the imprinted materials could be used successfully as SPE sorbents for sample pre-treatment for the determination of sildenafil, and related compounds, in plasma.

Application of molecularly imprinted polymers to solid-phase extraction of analytes from real samples

A review is presented of recent developments in the use of molecularly imprinted polymers (MIPs) as selective materials for solid-phase extraction. Compared with traditional sorbents, MIPs can not only concentrate but also selectively separate the target analytes from real samples, which is crucial for the quantitatively determination of analytes in complex samples. Consequently, as one of the most effective sorbents, MIPs have been successfully applied to the pretreatment of analytes in foods, drugs, and biological and environmental samples in the past five years.

Investigation of the nature of MIP recognition: The development and characterisation of a MIP for Ibuprofen

This paper describes the rational design, generation and testing of a molecularly imprinted polymer specific for Ibuprofen. Ibuprofen is a member of the class of drugs termed non-steroidal anti-inflammatory drugs (NSAIDS). In the present study, Ibuprofen was used as a template molecule for the preparation of molecularly imprinted polymers. A MIP has been produced which is capable of recognising Ibuprofen in aqueous media. Furthermore, Ibuprofen can be selectively extracted from aqueous conditions by molecularly imprinted solid phase extraction (MISPE). Recoveries were typically high (>80%) and good selectivity for Ibuprofen over structurally related analogues was seen. Moreover, the nature of the recognition between MIP and template has been investigated by NMR and molecular modelling to analyse whether or not it is possible to predict how well a given MIP will perform under set conditions. In addition, the physical characteristics of the MIP have been investigated including the particle size distribution on exposure of the MIP to different solvents. This has been related to the ability of the MIP to rebind Ibuprofen under the same conditions. The data from the characterisation of the MIP has been used to further enhance the understanding of the nature of MIP recognition.

Direct determination of ciprofloxacin by mass spectrometry after a two-step solid-phase extraction using a molecularly imprinted polymer

A molecularly imprinted polymer (MIP) has been prepared for the first time with ciprofloxacin (CIPRO) as the template molecule, via a noncovalent synthetic procedure. Prior to its use as a sorbent in SPE, the MIP was evaluated chromatographically to confirm that it was indeed molecularly imprinted. The MIP was then used to extract CIPRO selectively from urine samples by means of a two-step SPE procedure in which a commercial Oasis cartridge and a molecularly imprinted SPE cartridge were combined in series. This approach allowed the matrix compounds present in the samples to be removed effectively. The urine extracts obtained after this two-step SPE procedure was applied were relatively clean compared to the original samples, and this made it possible to inject directly the extracts into a mass spectrometer and thus quantify CIPRO in urine samples at low levels and reduce the time of analysis.

Molecularly imprinted materials as advanced excipients for drug delivery systems

The application of the molecular imprinting technology in the design of new drug delivery systems (DDS) and devices useful in closely related fields, such as diagnostic sensors or biological traps, is receiving increasing attention. Molecular imprinting technology can provide polymeric materials with the ability to recognize specific bioactive molecules and with a sorption/release behaviour that can be made sensitive to the properties of the surrounding medium. In this review, an introduction to the imprinting technology presenting the different approaches in preparing selective polymers of different formats is given, and the key factors involved in obtaining of imprinted binding sites in materials useful for pharmaceutical applications are analysed. Examples of DDS based on molecularly imprinted polymers (MIPs) can be found for the three main approaches developed to control the moment at which delivery should begin and/or the drug release rate; i.e., rate-programmed, activation-modulated or feedback-regulated drug delivery. This review seeks to highlight the most remarkable advantages of the imprinting technique in the development of new efficient DDS as well as to point out some possibilities of adapting the synthesis procedures to create systems compatible with both the relative instable drug molecules, especially of peptide nature, and the sensitive physiological tissues with which MIP-based DDS would enter into contact when administered. The prospects for future development are also analysed.

Analysis of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol in urine by extraction on a molecularly imprinted polymer column and liquid chromatography/atmospheric pressure ionization tandem mass spectrometry

The tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) is present in the urine of tobacco users and, at lower concentrations, in the urine of nonsmokers exposed to secondhand smoke. NNAL is a valuable biomarker of human exposure to the carcinogenic nitrosamines in tobacco and tobacco smoke, but its presence at low concentrations in urine requires sensitive and often complex analytic procedures. In this report, we describe the development of an efficient method for the analysis of NNAL in human urine using liquid chromatography/atmospheric pressure ionization tandem mass spectrometry (LC/MS/MS) combined with a novel sample cleanup based on a molecularly imprinted polymer (MIP) column developed specifically for this assay. Our results suggest that this combination of MIP column extraction and LC/MS/MS can provide a sensitive and relatively simple analytical method suitable for application to epidemiologic investigations of health risks associated with the exposure to tobacco smoke or SHS in both smokers and nonsmokers.

Determination of ropivacaine in human plasma using highly selective molecular imprint-based solid phase extraction and fast LC–MS analysis

A method for determining ropivacaine in human plasma using highly selective molecular imprint-based solid phase extraction and LC-MS analysis was developed. The imprinted extraction material was prepared using a structural analogue of ropivacaine as the template. The efficient sample cleanup achieved allowed single MS mode operation and analytical separation under isocratic conditions with a total separation time of less than two minutes. The absence of ion suppression was confirmed for both the m/z of ropivacaine and the m/z of the internal standard. The solid phase extraction protocol was optimised for elution of ropivacaine in a small volume of aqueous-rich solvent suitable for injection into a reversed phase LC-MS system. The final method measured trace levels of ropivacaine in human plasma with a limit of quantification of 2.5 nmol/L and interassay accuracy and precision of 101.7-104.4% and 2.1-7.2%, respectively.

An insight into molecularly imprinted polymers for capillary electrochromatography

Molecularly imprinted polymers (MIPs) are actively being developed as a practical tool for affinity chromatographic supports. From the viewpoint of separation science, capillary electrochromatography (CEC) might be one of the more promising chromatographic techniques to be used in combination with the MIPs. However, up to the present, very little MIP work has involved CEC. This review gives a full overview of MIP including current trends in MIP, methods for the characterization of MIP, and methods for the preparation of MIP with particular emphasis on application of the resulting materials in CEC. To prepare MIPs with selectivity predetermined for a particular substance or group of structural analogues is an important factor for the development of a new format of CEC. From the fundamental research with the batch method, a better knowledge of imprint formation and imprint recognition will be helpful for expanding the application area of the combination of MIPs with CEC.

The use of molecularly imprinted sol–gels in pharmaceutical separations

This paper illustrates the potential of the sol-gel process to imprint the pharmaceutical active--N-[N-[(1S)-1-carboxssy-3-phenylpropyl]-l-lysyl]-L-proline, (lisinopril dihydrate). This template exhibits unique difficulties such as limited solubility in non-polar and most polar porogens with multiple functionality evident in its 4 pKa values. Selectivity for this template was achieved using a 3-monomer sol-gel system utilising solid phase extraction (SPE). Analysis of the template and its related substances was achieved using HPLC. The effect of solvent polarity on the rebinding of the template was studied. Through optimisation of porogen and extraction solvent, the imprinted material (MIP) demonstrated enhanced selectivity, for the template, over a non-imprinted material (NIP). Selectivity was also illustrated for the original template over two of its related substances. The effect of starting monomer ratio on selectivity was studied to determine the interactions, which could best be exploited to further enhance selectivity.