A study of a new TSM bio-mimetic sensor using a molecularly imprinted polymer coating and its application for the determination of nicotine in human serum and urine

Advancing the use of molecularly imprinted polymers in bioanalysis: the selective extraction of cotinine in human urine

Aim: To characterize a molecularly imprinted polymer via precipitation polymerization for the extraction of cotinine in urine. Methods: The polymer was created via precipitation polymerization. Physical characteristics of the polymer were assessed via scanning electron microscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis. The polymer adsorption capacity was assessed and an solid-phase extraction method from urine by LC-MS/MS was developed. Results: The polymer had small, spherical morphology and little thermal decomposition. The extraction method yielded cotinine recoveries of 77-103% in urine. The molecularly imprinted polymer adsorption capacity for cotinine was 448.2 ± 2.1 μg/mg. Common interferants did not affect cotinine's extraction. Conclusion: The resulting polymer was determined to be specific for cotinine and can be used for the detection of cotinine in urine for clinical samples.

Insights on the Molecular Characteristics of Molecularly Imprinted Polymers as Monitored by Sum Frequency Generation Spectroscopy

Sensing in molecularly imprinted polymers (MIPs) requires specific interactions of the imprinted polymer and the approaching template molecule. These interactions are affected by the morphology of the polymer surface, the affinity of the template molecule to the polymer network, and the steric approach. In this particular study, a template molecule, metronidazole, is studied with respect to the typically used methacrylic acid-based imprinted polymer using a combination of bulk and surface techniques. The resulting infrared (IR) spectra exhibited the presence of the template molecule in the polymer matrix as well as their efficient removal after washing. Dipping of the MIP according to what is expected of facile sensing in an aqueous solution of metronidazole did not show any presence of the template molecule in the bulk of the MIP, as observed by IR spectroscopy. However, using sum frequency generation (SFG) spectroscopy, the CH aromatic stretch of the imidazole ring positioned at ∼3100 cm^-1 was observed at the polymer surface, including its inner pores or cavities, and at the buried polymer-fused silica interface after dipping. SFG studies have also shown the vibrational signatures of the polymer matrix, the presence of the template molecule on the surface, and the detection of residual template molecules after washing. Increasing the washing time to 50 min has proven to be less effective than increasing the washing cycles to three. However, after the third cycle, reorganization of the polymer matrix was evident as also the complete removal of the template molecule. The observed changes from the acquired images using scanning electron microscopy and atomic force microscopy show the structural morphologies of MIPs and a good distribution of the pores across the MIP surface. The study demonstrates the importance of combining both bulk and surface characterization in providing insight into the template molecule-polymer network interactions.

Effect of Multiaxial Tensile Deformation on the Mechanical Properties of Semiflexible Polymeric Samples

Molecular dynamics simulation is used to investigate the mechanical properties of the semiflexible polymer during multiaxial tensile deformations. The multiaxial tensile deformations can be imposed in totally or partially constrained modes. These types of deformations may be observed during the sudden deformation of polymeric material in the areas of aerospace, automobile, defense applications, etc. It is found that the constrained multiaxial deformation leads to the formation of nanovoids into the polymer sample. The high Young's modulus and yield strength for the totally constrained modes of tensile deformation are due to the energy required to create voids. The variation in von Misses stress, void volume, and bond order parameter with strain indicates the occurrence of brittle fracture during totally constrained tensile deformations. The partially constrained tensile deformations lead to the improvement in bond order parameter and lesser creation of nanovoids within the system. The system shows the characteristic strain hardening before failures.

Label-Free Bioanalyte Detection from Nanometer to Micrometer Dimensions-Molecular Imprinting and QCMs †

Modern diagnostic tools and immunoassay protocols urges direct analyte recognition based on its intrinsic behavior without using any labeling indicator. This not only improves the detection reliability, but also reduces sample preparation time and complexity involved during labeling step. Label-free biosensor devices are capable of monitoring analyte physiochemical properties such as binding sensitivity and selectivity, affinity constants and other dynamics of molecular recognition. The interface of a typical biosensor could range from natural antibodies to synthetic receptors for example molecular imprinted polymers (MIPs). The foremost advantages of using MIPs are their high binding selectivity comparable to natural antibodies, straightforward synthesis in short time, high thermal/chemical stability and compatibility with different transducers. Quartz crystal microbalance (QCM) resonators are leading acoustic devices that are extensively used for mass-sensitive measurements. Highlight features of QCM devices include low cost fabrication, room temperature operation, and most importantly ability to monitor extremely low mass shifts, thus potentially a universal transducer. The combination of MIPs with quartz QCM has turned out as a prominent sensing system for label-free recognition of diverse bioanalytes. In this article, we shall encompass the potential applications of MIP-QCM sensors exclusively label-free recognition of bacteria and virus species as representative micro and nanosized bioanalytes.

Molecular Imprinting Applications in Forensic Science

Producing molecular imprinting-based materials has received increasing attention due to recognition selectivity, stability, cast effectiveness, and ease of production in various forms for a wide range of applications. The molecular imprinting technique has a variety of applications in the areas of the food industry, environmental monitoring, and medicine for diverse purposes like sample pretreatment, sensing, and separation/purification. A versatile usage, stability and recognition capabilities also make them perfect candidates for use in forensic sciences. Forensic science is a demanding area and there is a growing interest in molecularly imprinted polymers (MIPs) in this field. In this review, recent molecular imprinting applications in the related areas of forensic sciences are discussed while considering the literature of last two decades. Not only direct forensic applications but also studies of possible forensic value were taken into account like illicit drugs, banned sport drugs, effective toxins and chemical warfare agents in a review of over 100 articles. The literature was classified according to targets, material shapes, production strategies, detection method, and instrumentation. We aimed to summarize the current applications of MIPs in forensic science and put forth a projection of their potential uses as promising alternatives for benchmark competitors.

Molecularly imprinted polymers: present and future prospective

Molecular Imprinting Technology (MIT) is a technique to design artificial receptors with a predetermined selectivity and specificity for a given analyte, which can be used as ideal materials in various application fields. Molecularly Imprinted Polymers (MIPs), the polymeric matrices obtained using the imprinting technology, are robust molecular recognition elements able to mimic natural recognition entities, such as antibodies and biological receptors, useful to separate and analyze complicated samples such as biological fluids and environmental samples. The scope of this review is to provide a general overview on MIPs field discussing first general aspects in MIP preparation and then dealing with various application aspects. This review aims to outline the molecularly imprinted process and present a summary of principal application fields of molecularly imprinted polymers, focusing on chemical sensing, separation science, drug delivery and catalysis. Some significant aspects about preparation and application of the molecular imprinting polymers with examples taken from the recent literature will be discussed. Theoretical and experimental parameters for MIPs design in terms of the interaction between template and polymer functionalities will be considered and synthesis methods for the improvement of MIP recognition properties will also be presented.

Fabrication and Characterization of a Surface-Acoustic-Wave Biosensor in CMOS Technology for Cancer Biomarker Detection

Design, fabrication, and characterization of a novel surface acoustic wave (SAW) biosensor in complementary metal-oxide semiconductor (CMOS) technology are introduced. The biosensor employs a streptavidin/biotin-based five-layer immunoassay for detecting a prominent breast cancer biomarker, mammoglobin (hMAM). There is a growing demand to develop a sensitive and specific assay to detect biomarkers in serum that could be used in the early detection of breast cancer, determining prognosis and monitoring therapy. CMOS-SAW devices present a viable alternative to the existing biosensor technologies by providing higher sensitivity levels and better performance at low costs. Two architectures (circular and rectangular) were developed and respective tests were presented for performance comparison. The sensitivities of the devices were analyzed primarily based on center frequency shifts. A frequency sensitivity of 8.704 pg/Hz and a mass sensitivity of 2810.25 m(2) /kg were obtained. Selectivity tests were carried out against bovine serum albumin. Experimental results indicate that it is possible to attach cancer biomarkers to functionalized CMOS-SAW sensor surfaces and selectively detect hMAM antigens with improved sensitivities, lowered costs, and increased repeatability of fabrication.

On-line molecularly imprinted solid-phase extraction for the selective spectrophotometric determination of nicotine in the urine of smokers

This work describes an on-line molecularly imprinted solid-phase extraction (MISPE) method for spectrophotometric determination of nicotine in urine samples of smokers. This method is based on manganese (VII) to manganese (VI) reduction in an alkaline medium, promoted by nicotine. Two wash solutions (1:4 (v/v) acetonitrile:sodium hydroxide--pH 11.4, and nitric acid--pH 2.5) were employed to circumvent interferences. Aqueous solutions containing nicotine plus different possible concomitants (cotinine, anabasine, norcotinine and caffeine) were tested individually. The analytical calibration curve was prepared in urine samples collected from non-smokers and spiked with nicotine standard from 1.1 to 60 micromol L(-1) (r(2)>0.998). The limit of quantification and the analytical frequency were 1.1 micromol L(-1) and 11 h(-1), respectively. The precision, evaluated using 3, 10 and 30 micromol L(-1) nicotine in urine, was 10, 10 and 4% (intra-day precision) and 12, 13 and 5% (inter-day precision), respectively. Accuracy was checked through high performance liquid chromatography and the results did not present significant differences at the 95% confidence level according to the Student's t-test.

Molecularly imprinted polymers in clinical diagnostics—Future potential and existing problems

The last five years have witnessed a fast progress in the area of molecularly imprinted polymers (MIPs). These have included the development of rational protocols for polymer design (combinatorial and computational), the development of MIPs compatible for use in aqueous environment and the development of various procedures for the integration of MIPs with sensors. The substantial improvements in the performance of imprinted polymers have also been accompanied by a growing number of MIP publications related to solving practical problems associated with their use, e.g. in environmental and clinical analysis. This paper furnishes a detailed analysis of recent achievements in MIPs design and applications related to healthcare, made by our group as well as others worldwide.

Application of a novel electrosynthesized polydopamine-imprinted film to the capacitive sensing of nicotine

The application of novel electrosynthesized polydopamine (PDA)-imprinted film as a recognition element for the capacitive sensing of nicotine is reported. The PDA-imprinted film was electropolymerized directly on the gold electrode surface in the presence of nicotine without an additional self-assembled thiol sublayer. The compact PDA film has various functional groups that aid the imprinting procedure. Furthermore, the film shows good capacitive response since it is insulating in nature and ultrathin. The sensor's linear response range for nicotine was between 1-25 micromol L(-1), with a detection limit of 0.5 micromol L(-1). The proposed molecularly imprinted polymer capacitive (MIPC) sensor exhibited good selectivity for nicotine. The reproducibility and repeatability of the MIPC sensor were all found to be satisfactory. The results from sample analysis confirmed the applicability of the MIPC sensor to quantitative analysis.

Designing a molecularly imprinted polymer as an artificial receptor for the specific recognition of creatinine in serums

In this study, molecularly imprinted polymers (MIP) synthesized from two different functional monomers, beta-cyclodextrin (beta-CD) and 4-vinylpyridine (4-Vpy), were prepared. The crosslinkers used for these two monomers were epichlorohydrin (EPI) and divinylbenzene (DVB), respectively. It was attempted to adsorb the target molecule, creatinine, from its mixture solutions. A proper molar ratio of monomer/crosslinker for the preparation of the imprinted poly(beta-CD) was 1:10. Between both polymers mentioned above, the affinity of the imprinted poly(4-Vpy-co-DVB) towards creatinine was comparably superior. The imprinted poly(4-Vpy-co-DVB) for creatinine could reach a specific binding ratio of 3.11. The imprinted poly(4-Vpy-co-DVB) was further utilized to bind creatinine from human serum samples. The binding capacity of the imprinted poly(4-Vpy-co-DVB) for creatinine from the serum samples was plotted against the creatinine concentration. From the correlation, the feasibility of the imprinted poly(4-Vpy-co-DVB) thus prepared for the target analyte, creatinine, was experimentally confirmed.

Molecular imprinting science and technology: a survey of the literature for the years up to and including 2003

Over 1450 references to original papers, reviews and monographs have herein been collected to document the development of molecular imprinting science and technology from the serendipitous discovery of Polyakov in 1931 to recent attempts to implement and understand the principles underlying the technique and its use in a range of application areas. In the presentation of the assembled references, a section presenting reviews and monographs covering the area is followed by papers dealing with fundamental aspects of molecular imprinting and the development of novel polymer formats. Thereafter, literature describing attempts to apply these polymeric materials to a range of application areas is presented.

Study on the enhancement of catalytic activity for hemoglobin by quinhydrone in poly(o-aminophenol) film

Hemoglobin (Hb) and quinhydrone (QHQ) were incorporated in poly(o-aminophenol) [o-AP, POAP] film by electropolymerization of o-aminophenol in a weak acid solution containing Hb and QHQ. The nonconducting polymer film was found to be nearly rigid by piezoelectric quartz crystal (PQC) impedance. Therefore, the thickness of the Hb-QHQ-POAP film was estimated as about 104 +/- 10 nm by quartz crystal microbalance (QCM). The QHQ mediation effects on the biomacromolecule Hb entrapped in the POAP film were investigated by using cyclic voltammetry, amperometric technique and kinetic study. Cyclic voltammograms showed that the redox peaks in the Hb-QHQ-POAP film are much more reversible than those in the Hb-POAP film. The response current of the Hb-QHQ-POAP film to H(2)O(2) was almost twice than that of the Hb-POAP film. The Michaelis-Menten constant and the activation energy of Hb in the Hb-QHQ-POAP film are 7.47 mM and 13.91 kJ/mol, respectively, both are smaller than that in the Hb-POAP film. These results showed that the immobilized Hb in POAP film exhibited higher catalytic activity to H(2)O(2) due to the mediation of QHQ.

Synthesis and application of molecularly imprinted polymer on selective solid-phase extraction for the determination of monosulfuron residue in soil

A novel sample clean-up procedure using molecularly imprinted polymer as the solid-phase extraction material for the determination of monosulfuron residue in soil samples has been developed. The molecularly imprinted polymer (MIP) was synthesized by non-covalent method with monosulfuron as the template. The selectivity and affinity of the MIP was evaluated by equilibrium adsorption and HPLC experiments, which demonstrated that the MIP has specific affinity for the template. The template-MIP interaction was studied by investigating the influence of different mobile phases on the retention of the template, which provided basic knowledge for the selection of the washing and elution solutions in the molecularly imprinted solid-phase extraction (MISPE) process. The study indicated that polar organic solvents with hydrogen bonding abilities have stronger eluting strength for the monosulfuron. After the MISPE procedure, a clean baseline was obtained in the HPLC quantification analysis. The recoveries of the method using the combination of MISPE and HPLC were above 93% and the R.S.D. was less than 3.2% in the soil sample determinations. Low detection limit (0.08 microg g(-1), when defined as 3 times of the noise) was also obtained in the method evaluation study.

Nuclear magnetic resonance study of the molecular imprinting of (−)-nicotine: template self-association, a molecular basis for cooperative ligand binding

In the present study, the interactions of components in a (-)-nicotine molecular imprinting polymerization mixture have been studied by 1H NMR spectroscopy. The dissociation constants for complexation of template by a functional monomer analogue, acetic acid, have been determined. Nicotine was shown to self-associate at concentrations comparable to those used in previous molecular imprinting studies (app K(diss) = 0.082M in CDCl3 at 298 K). The extent of self-association was enhanced by the presence of acetic acid. Previous studies on (-)-nicotine-imprinted methacrylic acid-ethylene dimethacrylate co-polymers suggested the involvement of recognition sites for template-template complexes. Collectively these results provide the first direct evidence for the presence of template-template complexes, and support the previously hypothesized basis for cooperative ligand recognition events in this polymer system.

Quartz crystal analytical sensors: the future of label-free, real-time diagnostics?

Acoustic sensor technologies have a long and prestigious history. However, liquid phase applications based upon thickness shear mode transducers are a relatively recent addition but are nonetheless being rapidly accepted as a broad usage analytical platform upon which to carry out label-free, real-time chemical, biological and pharmaceutical assays. This article discusses the development of thickness shear mode devices, current technologies, with a focus on the breadth of application and the future potential of the technique within the pharmaceutical and biochemical industries.