Synthetic Recognition Elements Research Articles

Bioinspired host-tailored polymers based on molecular imprinting for cytokine assessment

Molecular imprinting undergone a substantial boost driven by the awareness of molecularly imprinted polymers (MIPs)-ligand recognition skills. In particular, the introduction of natural-based compounds like cyclodextrins into the structural scaffold of synthetic recognition elements attracted great importance as a novel route to design more friendly-environments for protein binding, while promoting higher selectivity features. Herein, carbon electrodes doped with platinum nanoparticles supported on multiwalled carbon nanotubes and functionalized with polyallylamine (MWCNTs-PAH/Pt) were electrochemically modified with an imprinted sensing layer of poly(β-cyclodextrin-pyrrole) (poly(β-CD-Py)) towards interleukin 6 (IL-6) monitoring. The analytical performance of the biosensor was evaluated by using Cyclic Voltammetry and Electrochemical Impedance Spectroscopy techniques. Along the assembly, experimental parameters like nanomaterial deposition, monomer-protein concentrations and template removal solutions were carefully optimized and discussed. Furthermore, the electrodeposited film was characterized in terms of composition, morphology and structure using scanning electron microscopy (SEM) and Raman spectroscopy. Under optimal conditions, the developed sensor was able to rebind IL-6 over a wide linear range [1 pg/mL – 100 ng/mL], displaying high sensitivity, quick electrochemical response, and specific binding of the target molecule. Overall, this work reported the relevance of using host-guest complexes directly embedded in polymeric chains to generate newly controlled electrochemical sensors holding great potential for protein biosensing.

Metal Microwires Functionalized with Cell-Imprinted Polymer for Capturing Bacteria in Water

Molecularly imprinted polymers (MIPs) and cell-imprinter polymers (CIPs) have emerged as synthetic recognition elements in biomimetic sensors. In this paper, we have conducted a parametric study to optimize a bulk polymerization methodology for uniform functionalization of stainless steel microwires (MWs) with CIPs comprising single to fourplex combinations of functional monomers (FMs). MWs are widely used in biosensors, and their functionalization with single-FM MIPs has been demonstrated. Complex MIPs comprising multiple FMs have shown enhanced selectivity toward microorganisms, but their coating on MWs has yet to be shown. Moreover, imprinting microorganisms into these coatings has not been reported. In our studies, solvent, FM, cross-linker-to-FM ratio, polymerization temperature, and time were found to significantly influence the thickness and uniformity of CIP coatings on MWs. Reproducible CIP coatings with a thickness of 2.2 ± 0.4 μm, imprinted with E. coli OP50 as the template, were achieved. E. coli rebinding assays demonstrated a 76 ± 10% capture efficiency in a suspension with an initial bacteria count of 104 CFU/mL, using a 3 cm long CIP-MW with an optimized fourplex CIP composition, while the capture efficiency obtained by using a single-monomer CIP composition was 30 ± 5%. Our results indicated a higher binding capacity of fourplex CIP-MWs to target bacteria, while nonsignificant binding was obtained using single-monomer CIP-MWs. The addition of N-vinylpyrrolidone significantly increased the binding performance due to its hydrophobic–hydrophilic functional groups interacting with counterparts on the surface of bacterial cells. The developed CIP-MWs can be integrated with microfluidic sensing systems as low-cost and stable working electrodes for future transduction of CIP-target binding events to an electrical read-out in CIP-based electrochemical biomimetic sensors.

Recent progress on electrochemical (bio)sensors based on aptamer-molecularly imprinted polymer dual recognition

Antibodies have been the dominant receptors used to construct biosensors and bioassays owing to their intrinsically excellent antigen specificity and affinity. Despite their wide applications, antibodies suffer from many drawbacks such as high costs, poor stability, limited availability, and stringent storage conditions. Over the last three decades, aptamers and molecularly imprinted polymers (MIPs) have emerged as alternative synthetic receptors to substitute antibodies in biosensors and bioassays due to their specific conformational and binding relationships to analytes and selectivity similar to that of natural counterparts. More recently, aptamers and MIPs have been combined as a hybrid system that combines both of these synthetic recognition elements to detect various analytes such as small molecules, proteins, and viruses, utilizing their desired properties and complementing each other's limitations. Due to the overall low-cost, high sensitivity, miniaturization compatibility, and portability of electrochemical sensors, this review focuses on the recent progress of electrochemical (bio)sensors based on aptamer-MIP (AptaMIP) dual receptors since the first one reported in 2016. Three design strategies of AptaMIP-based electrochemical sensors with related works are summarized and discussed in detail, including aptamer embedded in MIP as a hybrid receptor, aptamer and MIP dual-functional areas-based microfluidic device, and MIP/Target/aptamer sandwich assay. For each strategy, sensor configurations, transducing mechanisms, strengths and limitations are discussed.

Approaches to the Rational Design of Molecularly Imprinted Polymers Developed for the Selective Extraction or Detection of Antibiotics in Environmental and Food Samples

The World Health Organisation (WHO) reported antimicrobial resistance (AMR) as a global threat comparable to terrorism and climate change. The use of antibiotics in veterinary or clinical practice exerts a selective pressure, which accelerates the emergence of antimicrobial resistance. Therefore, there is a clear need to detect antibiotic residues in complex matrices, such as water, food, and environmental samples, in a fast, selective, cost‐effective, and quantitative manner. Once problematic areas are identified, can extraction of the antibiotics then be carried out to reduce AMR development. Molecularly imprinted polymer (MIPs) are synthetic recognition elements produced through the biomarker of interest being used as a template in order to manufacture tailor‐made ligand selective polymeric recognition sites. They are emerging steadily as a viable alternative to antibiotics, especially given their low‐cost, superior thermal and chemical stability that facilitates on‐site detection, simplified manufacturing process, and avoiding the use of animals in the production process. In this paper, the authors critically review literature from primarily 2010–2020 on rational design approaches used to develop MIPs for sensing and extraction of antibiotics, providing an outlook on crucial issues that need to be tackled to bring MIPs for antibiotic sensing to the market.

Towards the development of cascaded surface plasmon resonance POF sensors exploiting gold films and synthetic recognition elements for detection of contaminants in transformer oil

The possibility of developing a multichannel optical chemical sensor, based on molecularly imprinted polymers (MIPs) and surface plasmon resonance (SPR) in a D-shaped multimode plastic optical fiber (POF), is presented by two cascaded SPR-POF-MIP sensors with different thicknesses of the gold layer. The low cost, the high selectivity and sensitivity of the SPR-POF-MIP platforms and the simple and modular scheme of the optical interrogation layout make this system a potentially suitable on-line multi-diagnostic tool. As a proof of principle, the possibility of simultaneous determination of two important analytes, dibenzyl disulfide (DBDS) and furfural (2-FAL), in power transformer oil was investigated. Their presence gives useful indication of underway corrosive or ageing processes in power transformers, respectively. Preliminarily, the dependence of the performance of the D-shaped optical platform on the gold film thickness has been studied, comparing two platforms with 30nm and 60nm thick gold layers. It has been found that the resonance wavelengths are different on platforms with gold layer of different thickness, furthermore when MIPs are present on the gold as receptors, the performances of the platforms are similar in the two considered sensors.

Evaluating the potential of thermal read-out techniques combined with molecularly imprinted polymers for the sensing of low-weight organic molecules.

In recent years, there has been a tremendous increase in the papers published on synthetic recognition elements. Molecularly imprinted polymers (MIPs), also referred to as "man-made mimics" of antibodies, are able to rebind their template molecules with high affinity. Advantages compared with those of natural receptors include their excellent thermal and chemical stability, low cost, and ease of the production process. However, their use in commercial biosensors is limited owing to the difficulty to incorporate MIPs into suitable sensing platforms and traditional detection techniques, such as chromatography, that require bulky and sophisticated equipment. In this review, we evaluate the potential to use MIPs combined with thermal read-out for the detection of low-weight organic molecules. We discuss thermal methods to study MIP-template complexation and to determine neurotransmitters concentrations. In particular, we highlight the heat-transfer method, a recent technique that is straightforward and low cost and requires minimal instrumentation. Until now, sample preparation involves a 2-step process, making it time-consuming, and measuring biological samples is difficult owing to the noise in the signal. Different sample preparation methods are discussed, and it will be demonstrated how this affects the thermal response. An outlook is given in novel methods that can simplify and speed up sample preparation. Finally, we show a novel thermal technique, which is based on the analysis of transport of thermal waves rather than evaluating the fixed heat-transfer resistance. Through applying the concept of thermal waves, signal-noise ratio is significantly increased, which results in lower detection limits and has potential for the study of biological samples.

Affinity sensor based on immobilized molecular imprinted synthetic recognition elements.

An affinity sensor based on capacitive transduction was developed to detect a model compound, metergoline, in a continuous flow system. This system simulates the monitoring of low-molecular weight organic compounds in natural flowing waters, i.e. rivers and streams. During operation in such scenarios, control of the experimental parameters is not possible, which poses a true analytical challenge. A two-step approach was used to produce a sensor for metergoline. Submicron spherical molecularly imprinted polymers, used as recognition elements, were obtained through emulsion polymerization and subsequently coupled to the sensor surface by electropolymerization. This way, a robust and reusable sensor was obtained that regenerated spontaneously under the natural conditions in a river. Small organic compounds could be analyzed in water without manipulating the binding or regeneration conditions, thereby offering a viable tool for on-site application.

In-situ polymerized molecularly imprinted polymeric thin films used as sensing layers in surface plasmon resonance sensors: Mini-review focused on 2010–2011

AbstractThis review provides a short overview of polymeric thin films incorporating molecular imprints within their 3D macromolecular structure as synthetic recognition elements and prepared by in situ polymerization for surface plasmon resonance application. This review starts with a brief reminder of the principle of surface plasmon resonance detection. The second section is focused on molecularly imprinted materials. Bulk and thin film polymer formats can be obtained by free radical polymerization, where the functional monomer interacts specifically with the template and the cross-linker controls the rigidity of the imprinted cavities. Grafting polymerization is presented as a method of choice for covalent attachment of ultra-thin molecularly imprinted films on a surface plasmon resonance metallic substrate. Examples of electropolymerized thin films are also provided. In the rest of this contribution, surface plasmon resonance applications of molecularly imprinted polymers reported mainly over the last two years are presented with respect to the preparation mode. Also, applications of gold nanoparticle/molecularly imprinted polymer composites for the design of surface plasmon resonance-based sensors with enhanced sensitivity due to the phenomenon of localized surface plasmon resonance induced by the presence of gold nanoparticles are summarized.

MIP-based sensor platforms for the detection of histamine in the nano- and micromolar range in aqueous media

The need for more advanced, accurate and lower cost sensor platforms is constantly growing. However, for certain applications the already existing sensing systems based on biological recognition elements have sometimes restrictions, which limit their use. As a result, sensors with synthetic recognition elements, such as molecular imprinted polymers (MIPs), can be interesting alternatives. Molecular imprinting leads to the formation of inert polymer particles with nanocavities, which can exhibit similar selectivity and specificity to target molecules as antibodies or enzymes. It is demonstrated that MIPs can be readily incorporated into two different sensor platforms for the detection of histamine in aqueous media. The first platform is based on electrochemical impedance spectroscopy and allows for the accurate detection of histamine in the nanomolar range. The second sensing technique is based on microgravimetry and allows for the detection of histamine in the micromolar range. Using the analogous molecule histidine, it is demonstrated that both sensor platforms are specific for the detection of histamine.

MONITORIZACIÓN DE LA DEGRADACIÓN DE ACEITES CON SENSORES QUÍMICOS Y POLÍMEROS DE IMPRONTA MOLECULAR OIL DEGRADATION MONITORING WITH CHEMICAL SENSORS AND MOLECULAR IMPRINTED POLYMER

The engine operation state can be reported by real-time monitoring programs. Detecting early signs of equipment failure is the aim of these maintenance programs.Chemical sensors are devices that can perform this function in predictive maintenance.The monitoring of the degradation of automotive engine oils has been achieved by chemical sensors coated with synthetic recognition elements. Following, the elements that make up the QCM device, MIPs, organic-inorganic hybrid materials obtained by sol-gel and electronic packaging are described.

Application of the Doehlert experimental design to molecularly imprinted polymers: surface response optimization of specific template recognition as a function of the type and degree of cross-linking

We propose the use of Doehlert's experimental design, a second-order uniform shell design, for the optimization of molecularly imprinted polymers (MIPs). We have chosen a simple model system where the influence of kind and degree of cross-linking on template recognition was studied using S-propranolol as the template. We found that Doehlert's design allows--with very few experiments--one to screen the evolution of the binding capacity of a MIP as a function the different parameters, and thus appears to be a powerful means to screen for the best composition and synthesis method for MIPs. We believe that this chemometric tool can significantly accelerate the development of new MIPs as synthetic recognition elements, particularly in the context of a given application, and will be a versatile complement or alternative to first-order designs to fit complex processes.

A Fluorescence-Based Synthetic LPS Sensor

For the detection of bioanalytes, there is an ongoing search for synthetic sensors to replace enzyme-based assays which are sensitive to contaminants or suboptimal storage conditions. Lipopolysaccharide (LPS), a bacteria-borne endotoxin that may lead to life-threatening conditions such as septic shock, is one such case. Fluorescently labeled analogues of two peptide variants derived from the putative ligand-binding domain of the LPS-binding protein CD14 were developed that detect and discriminate LPS and lipids down to the submicromolar concentration range. Peptides are terminally labeled with carboxyfluorescein and tetramethylrhodamine. For one given peptide, sensitivity and specificity for the detection of LPS and discrimination from other lipids are achieved by spectral signatures that combine changes in the fluorescence resonance energy transfer (FRET) between both dyes and the total emission of tetramethylrhodamine. Alternatively, specificity is obtained by combining the FRET efficiencies of both peptide variants. In comparison to published synthetic LPS sensors, the CD14-derived sensors yield an increase in sensitivity by about 3 orders of magnitude and exhibit specificity for analytes for which the design of synthetic recognition elements is a challenging task. Moreover, one of the sensors enabled the detection of LPS in the presence of up to 50% fetal calf serum, thereby demonstrating the feasibility of this peptide-based approach for clinically relevant samples.