Development of a rubber elongation factor, surface-imprinted polymer–quartz crystal microbalance sensor, for quantitative determination of Hev b1 rubber latex allergens present in natural rubber latex products

Spectroscopic Ellipsometry and Quartz Crystal Microbalance with Dissipation for the Assessment of Polymer Layers and for the Application in Biosensing

Polymers represent materials that are applied in almost all areas of modern life, therefore, the characterization of polymer layers using different methods is of great importance. In this review, the main attention is dedicated to the non-invasive and label-free optical and acoustic methods, namely spectroscopic ellipsometry (SE) and quartz crystal microbalance with dissipation (QCM-D). The specific advantages of these techniques applied for in situ monitoring of polymer layer formation and characterization, biomolecule immobilization, and registration of specific interactions were summarized and discussed. In addition, the exceptional benefits and future perspectives of combined spectroscopic ellipsometry and QCM-D (SE/QCM-D) in one measurement are overviewed. Recent advances in the discussed area allow us to conclude that especially significant breakthroughs are foreseen in the complementary application of both QCM-D and SE techniques for the investigation of polymer structure and assessment of the interaction between biomolecules such as antigens and antibodies, receptors and ligands, and complementary DNA strands.

Molecularly imprinted polymer as a synthetic antibody for the biorecognition of hazelnut Cor a 14-allergen

Artificial receptors that mimic their natural biological counterparts have several advantages, such as lower production costs and increased shelf-life stability/versatility, while overcoming the ethical issues related to raising antibodies in animals. In this work, the proposed tailor-made molecularly imprinted polymer (MIP)-allergen receptors aimed at substituting or even transcending the performance of biological antibodies. For this purpose, a MIP was proposed as an artificial antibody for the recognition of hazelnut Cor a 14-allergen. The target protein was grafted onto the conducting polypyrrole receptor film using gold screen-printed electrodes (Au-SPE). The electrochemical assessment presented a linear response for the dynamic range of 100 fg mL^-1-1 μg mL^-1 and a LOD of 24.5 fg mL^-1, as determined by square wave voltammetry from the calibration curves prepared with standards diluted in phosphate buffer. Surface plasmon resonance (SPR) was used as a secondary transducer to evaluate the performance of the Cor a 14-MIP sensor, enabling a linear dynamic range of 100 fg mL^-1- 0.1 μg mL^-1 and a LOD of 18.1 fg mL^-1. The selectivity of the tailored-made Cor a 14-MIP was tested against potentially cross-reactive plant/animal species based on the rebinding affinity (Freundlich isotherm-K_F) of homologues/similar proteins, being further compared with custom-made polyclonal anti-Cor a 14 IgG immunosensor. Results evidenced that the MIP mimics the biorecognition of biological antibodies, presenting higher selectivity (only minor cross-reactivity towards walnut and Brazil nut 2S albumins) than the Cor a 14/anti-Cor a 14 IgG immunosensor. The application of electrochemical Cor a 14-MIP sensor to model mixtures of hazelnut in pasta enabled quantifying hazelnut down to 1 mg kg^-1 (corresponding to 0.16 mg kg^-1 of hazelnut protein in the matrix). To the best of our knowledge, Cor a 14-MIP is the first sensor based on an artificial/synthetic biorecognition platform for the specific detection of hazelnut allergens, while presenting high-performance parameters with demonstrated application in food safety management.

An electrochemical paper-based analytical sensor for one-step latex protein detection

A proposed simple electrochemical paper-based analytical sensor offered one-step latex protein detection by measuring remaining copper after online protein complexation

Assessment of cross-reactivity in a tailor-made molecularly imprinted polymer for phenolic compounds using four adsorption isotherm models

Cross-reactivity is an important feature of molecularly imprinted polymers (MIPs), and is central to successful use of a pseudo-template in molecular imprinting. The adsorption and cross-reactivity of a molecularly imprinted polymer (MIP) designed for recognition of phenols from water was assessed using four different isotherm models (Langmuir (LI), Freundlich (FI), Langmuir-Freundlich (L-FI), and Brunauer, Emmett, and Teller (BET)). The L-FI model succeeded in explaining the cross-reactivity behavior through the total number of binding sites, the affinity constants and heterogeneity indices of the small phenols (phenol (ph), 2-methylphenol (2-MP), 3-methylphenol (3-MP), 2-chlorophenol (2-CP), 2,4-dimethylphenol (DMP), 2,4-dichlorophenol (DCP), 4-chloro-3-methylphenol (CMP)) with evidence that the phenols compete for binding sites based on their hydrophobicity as well as π-π, π-σ and dipole-dipole intermolecular forces. The recognition of the large phenols (2,4,6-trichlorophenol (TCP), pentachlorophenol (PCP), 4-teroctylphenol (4-OP), 4-nonylphenol (4-NP), which have much higher binding affinities than the smaller phenolic compounds, was explained with the BET isotherm model that predicts that multiple layers adsorb to the adsorbed monolayer. The adsorption behavior with MIPs is also shown to be superior to corresponding non-imprinted polymers and applicability of MIPs for trace analysis is highlighted.

Dopaminergic receptor-ligand binding assays based on molecularly imprinted polymers on quartz crystal microbalance sensors

Molecularly imprinted polymers (MIPs) have been successfully applied as selective materials for assessing the binding activity of agonist and antagonist of dopamine D1 receptor (D1R) by using quartz crystal microbalance (QCM). In this study, D1R derived from rat hypothalamus was used as a template and thus self-organized on stamps. Those were pressed into an oligomer film consisting of acrylic acid: N-vinylpyrrolidone: N,N'-(1,2-dihydroxyethylene) bis-acrylamide in a ratio of 2:3:12 spin coated onto a dual electrode QCM. Such we obtained one D1R-MIP-QCM electrode, whereas the other electrode carried the non-imprinted control polymer (NIP) that had remained untreated. Successful imprinting of D1R was confirmed by AFM. The polymer can re-incorporate D1R leading to frequency responses of 100-1200Hz in a concentration range of 5.9-47.2µM. In a further step such frequency changes proved inherently useful for examining the binding properties of test ligands to D1R. The resulting mass-sensitive measurements revealed Kd of dopamine∙HCl, haloperidol, and (+)-SCH23390 at 0.874, 25.6, and 0.004nM, respectively. These results correlate well with the values determined in radio ligand binding assays. Our experiments revealed that D1R-MIP sensors are useful for estimating the strength of ligand binding to the active single site. Therefore, we have developed a biomimetic surface imprinting strategy for QCM studies of D1R-ligand binding and presented a new method to ligand binding assay for D1R.

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.

Mast cell-based electrochemical biosensor for quantification of the major shrimp allergen Pen a 1 (tropomyosin)

A novel cell-based electrochemical biosensor was developed to quantify major shrimp allergen Pen a 1 (tropomyosin) and to assess its immunoglobulin E (IgE)-mediated hypersensitivity. Rat basophilic leukemia (RBL-2H3) mast cells, encapsulated in type I collagen, were immobilized on a self-assembled l-cysteine/gold nanoparticle (AuNPsCys)-modified gold electrode to monitor IgE-mediated mast cell sensitization and activation. The exposure of dinitrophenol-bovine serum albumin (DNP-BSA), as a model antigen that stimulates mast cells, induced a robust and long-lasting electrochemical impedance signal in a dose-dependent manner which efficiently measured degranulation of anti-DNP IgE-stimulated mast cells. Then this mast cell-based biosensor was applied into quantification for the shrimp allergen with anti-shrimp tropomyosin IgE-sensitization. The electrochemical impedance spectroscopy (EIS) results showed that the impedance value (Ret) increased with the concentration of purified shrimp allergen Pen a 1 (tropomyosin) in range of 0.5-0.25 μg mL(-1) with the detection limit as 0.15 μg mL(-1), and the electrochemical result was confirmed by β-hexosaminidase assay and scanning electron microscopic morphological (SEM) analysis. Thus, a simple, label-free, and sensitive method for the determination of shrimp allergens was proposed and demonstrated here, implying a highly versatile biosensor for food allergen detection and prediction.

Preparation of an ion-imprinted fiber for the selective removal of Cu2+

A novel Cu(2+)-imprinted fiber (IIF) was prepared by grafting acrylic acid (AA) onto the surface of a polypropylene (PP) fiber and subsequently modified with polyethylenimine (PEI). An examination by infrared spectroscopy and scanning electron microscopy confirmed that the ion-imprinted polymer was successfully introduced onto the surface of a PP fiber. The modification of PP fibers with AA was beneficial to the grafting of PEI onto the fibers. The highest grafting degree of PEI could reach 120 wt % under optimal grafting conditions. This IIF showed excellent tensile and chemical stability in acid solution, which qualified the IIF for practical applications. Besides having a high adsorption capacity for Cu(2+) (120 mg/g), the IIF adsorbent showed a high selectivity for Cu(2+) as compared with that of the non-ion-imprinted fiber (NIF). The dynamic adsorption results indicated that IIF can thoroughly remove Cu(2+) from the solution in a relatively short contact time. The effective treatment volume was about 910 bed volumes. The selectivity coefficient of IIF for Cu(2+) with respect to Zn(2+) could reach 76.4. IIF also has good regeneration performance and could maintain almost the same adsorption capacity for copper ions after 10 adsorption-desorption cycles.