Protein-imprinted polysiloxane scaffolds

Sol-gel process: the inorganic approach in protein imprinting

Proteins play a central role in the signal transmission in living systems since they are able to recognize specific biomolecules acting as cellular receptors, antibodies or enzymes, being themselves recognized by other proteins in protein/protein interactions, or displaying epitopes suitable for antibody binding. In this context, the specific recognition of a given protein unlocks a range of interesting applications in diagnosis and in targeted therapies. Obviously, this role is already fulfilled by antibodies with unquestionable success. However, the design of synthetic artificial systems able to endorse this role is still challenging with a special interest to overcome limitations of antibodies, in particular their production and their stability. Molecular Imprinted Polymers (MIPs) are attractive recognition systems which could be an alternative for the specific capture of proteins in complex biological fluids. MIPs can be considered as biomimetic receptors or antibody mimics displaying artificial paratopes. However, MIPs of proteins remains a challenge due to their large size and conformational flexibility, their complex chemical nature with multiple recognition sites and their low solubility in most organic solvents. Classical MIP synthesis conditions result in large polymeric cavities and unspecific binding sites on the surface. In this review, the potential of the sol-gel process as inorganic polymerization strategy to overcome the drawbacks of protein imprinting is highlighted. Thanks to the mild and biocompatible experimental conditions required and the use of water as a solvent, the inorganic polymerization approach better suited to proteins than organic polymerization. Through numerous examples and applications of MIPs, we proposed a critical evaluation of the parameters that must be carefully controlled to achieve sol-gel protein imprinting (SGPI), including the choice of the monomers taking part in the polymerization.

Preparation and characterization of 96-well microplates coated with molecularly imprinted polymer for determination and biosimilarity assessment of recombinant human erythropoietin

Synthesis and applications of molecularly imprinted polymers (MIP) are rapidly growing. In this study, a biomimetic MIP was prepared through silanes polymerization on the surface of 96-well microplates using recombinant human erythropoietin-alfa (rhEPO) as a template molecule. The rhEPO was immobilized onto the plate surface using bi-functional cross-linker and a thin imprinted layer following sol-gel procedure was constructed. After template extraction, uniform three-dimensional cavities compatible with the configuration of rhEPO were obtained. The rhEPO-MIP preparation was optimized using 2-level factorial design and response surface design where polymerization time and interactions between the different variable were found to be the most significant factors. Size-exclusion chromatography (SEC) was used to monitor the stability of the rhEPO under the investigated polymerization conditions. Determination of rhEPO using the MIP microplate showed good dynamic response fitting to the 4 PL regression model (0.9962) over a concentration range of 10.00 - 100.00 ng mL^-1. Adsorption of rhEPO onto MIP followed the Langmuir isotherm model (r = 0.9957, χ² =0.02786) with pseudo-second-order kinetics (r = 0.9984). The surface of the rhEPO-MIP was characterized using scanning electron microscopy (SEM) while step-by-step surface modification was tracked using Fourier transform infrared (FTIR) spectroscopy. The rhEPO-MIP was able to distinguish between the rhEPO-alfa template and modified rhEPO molecules; rhEPO-beta, hyperglycosylated and pegylated forms (imprinting factors < 2) and in the commonly used formulation additive human serum albumin (HSA) (R% = 113.96 -95.22%). The rhEPO-MIP was applied to compare the receptor-binding pattern to rhEPO and its biosimilars / structural analogues. The results were cross-validated using the conventional assay protocol (RP-HPLC and ELISA) and an acceptable correlation was observed with RP-HPLC (maximum deviation is 7.78%). This work confirmed the applicability of rhEPO-MIP with its unique binding features for batch release, stability and biosimilarity assessment as well as subsequent evaluation of batch-to-batch consistency during bioproduction of target analytes.

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.

Hydrogel-Based Molecularly Imprinted Polymers for Biological Detection

Molecularly imprinted polymers (MIPs) have become an important tool in the preparation of artificial and robust recognition materials that are capable of mimicking natural systems. MIPs have been regarded as 'antibody mimics' and have shown clear advantages over real antibodies for sensor technology. Currently, on-site diagnostic (OSD) and point-of-care (POC) biosensor development are heavily dominated by antibody-dependent immuno-sensors such as the lateral flow immuno-assay. Although antibodies exhibit a high degree of selectivity, any biological recognition element is inherently unstable with limited shelf-life, even when stored under optimum conditions. OSD and POC tests are essential for disease screening and treatment monitoring as part of emergency management. Introduced or naturally occurring pathogens can cause significant disruptions, raise panic in the population, and result in significant economic losses. Cheaper, smaller, and smarter devices for early detection of disease or environmental hazards ultimately lead to rapid containment and corrective action. To this end, there has been extensive research on detection platforms based on genetic or immune techniques. MIPs have proven to produce selective biological extractions that rival immunoaffinity-based separations, but without the tediously lengthy time-consuming process. MIPs could provide an alternative to antibodies, and ultimately lead to cheaper, smaller, and smarter biosensors.

Novel electrochemical sensor for the selective recognition of chlorogenic acid

In this study, a novel sensitive molecularly imprinted electrochemical sensor was constructed for the selective detection of chlorogenic acid (CGA) by deposition of a molecularly imprinted siloxane (MIS) film, prepared by sol-gel process, onto Au bare electrode surface. Initially, a (3-mercaptopropyl)siloxane layer (MSL) was formed on the Au bare surface, followed by a siloxane layer obtained from the acid-catalyzed hydrolysis/condensation of a solution constituted by tetraethoxysilane (TEOS), phenyltriethoxysilane (PTEOS), 3-(aminopropyl)trimethoxysilane (APTMS) and CGA, as a molecular template. After the GCA extraction the MIS imprinted film was electrochemically characterized using differential pulse voltammetry (DPV). The MIS/Au sensor was tested in a solution of the CGA template and other similar molecules. This electrode displayed excellent selectivity towards CGA when compared with structurally similar molecules. Under optimized experimental conditions, the peak current response of the sensor for CGA was linear from 5.0 × 10(-7)mol L(-1) to 1.4 × 10(-5)mol L(-1), and the detection limit was 1.48 × 10(-7)mol L(-1). The MIS/Au sensor was successfully applied for the determination of CGA in coffee and tea samples.

Absorption performance of iodixanol-imprinted polymers in aqueous and blood plasma media

This paper presents the preparation and absorption performance of iodixanol-imprinted polymers in aqueous and blood plasma media in vitro for biomedical applications. The imprinted polymers were prepared by non-covalent imprinting of iodixanol in a matrix of poly(4-vinylpyridine) crosslinked by ethylene glycol dimethacrylate. The binding capacities (BCs) were investigated as a function of template-to-monomer, as well as monomer-to-crosslinker, ratios in the polymerization, and the solvent type. The highest BC of iodixanols achieved from the optimized imprinted polymer in the aqueous solution is 284mgg(-1) dry polymer with an imprinting effect (IE) 8.8 times higher than that of the non-imprinted polymer. In blood plasma, the BC of this polymer is slightly reduced to 232mgg(-1) with a smaller IE 4.3 times higher than that of the control polymer. The BCs of molecularly imprinted polymers as a function of the initial assay solution concentration as well as the examination time are also addressed. Surface analyses were additionally performed to characterize the surface morphologies and porosities of synthetic polymers. This work has demonstrated the feasibility of molecular imprinting of iodixanol, and the observed absorption performance of the imprinted polymers is encouraging for biomedical applications.

Molecularly imprinted nanopatterns for the recognition of biological warfare agent ricin

Molecularly imprinted polymer (MIP) for biological warfare agent (BWA) ricin was synthesized using silanes in order to avoid harsh environments during the synthesis of MIP. The synthesized MIP was utilized for the recognition of ricin. The complete removal of ricin from polymer was confirmed by fluorescence spectrometer and SEM-EDAX. SEM and EDAX studies confirmed the attachment of silane polymer on the surface of silica gel matrix. SEM image of Ricin-MIP exhibited nanopatterns and it was found to be entirely different from the SEM image of non-imprinted polymer (NIP). BET surface area analysis revealed more surface area (227 m(2)/g) for Ricin-MIP than that of NIP (143 m(2)/g). In addition, surface area study also showed more pore volume (0.5010 cm(3)/g) for Ricin-MIP than that of NIP (0.2828 cm(3)/g) at 12 nm pore diameter confirming the presence of imprinted sites for ricin as the reported diameter of ricin is 12 nm. The recognition and rebinding ability of the Ricin-MIP was tested in aqueous solution. Ricin-MIP rebound more ricin when compared to the NIP. Chromatogram obtained with Ricin-MIP exhibited two peaks due to imprinting, however, chromatogram of NIP exhibited only one peak for free ricin. SDS-PAGE result confirmed the second peak observed in chromatogram of Ricin-MIP as ricin peak. Ricin-MIP exhibited an imprinting efficiency of 1.76 and it also showed 10% interference from the structurally similar protein abrin.

Protein Binding to Peptide-Imprinted Porous Silica Scaffolds

Of the many types of biomolecules used for molecular imprinting applications, proteins are some of the most useful, yet challenging, templates to work with. One method, termed the 'epitope approach', involves imprinting a short peptide fragment of the protein into the polymer to promote specific adsorption of the entire protein, similar to the way an antigen binds to an antibody via the epitope. Whole lysozyme or the 16 residue lysozyme C peptide was imprinted into porous silica scaffolds using sol-gel processing. After removing template, scaffolds were exposed to lysozyme and/or RNase A, which was used as a competitor molecule of comparable size. When comparing protein- to peptide-imprinted scaffolds, similar amounts of lysozyme and RNase were bound from single protein solutions. However, while whole lysozyme-imprinted scaffolds showed about 4:1 preferential binding of lysozyme to RNase, peptide-imprinted scaffolds failed to show statistical significance, even though a slight preferential binding trend was present. These initial studies suggest there is potential for using peptide-imprinting to create specific protein-binding sites on porous inorganic surfaces, although further development of the materials is needed.