Cell detection by surface imprinted polymers SIPs:A study to unravel the recognition mechanisms

Previous studies have shown that selective synthetic cell receptors can be produced by cell imprinting on polymer layers. However, knowledge on the fundamental detection mechanisms remains limited. In this article, while using yeast cells (Saccharomyces cerevisiae) as model cells, the factors influencing cellular recognition by surface-imprinted polymers (SIPs) are studied by means of spectroscopic and microscopy techniques and a transducer platform based on interfacial thermal transport, the so-called heat-transfer method (HTM). These analyses indicate that cell imprinting creates selective binding sites on the surface of the SIP layer in the form of binding cavities that match the cells in shape and size. Also, we show that phospholipid moieties are incorporated into the SIP cavities during imprinting, while membrane proteins do not seem to be transferred. More importantly, we demonstrate that the incorporated phospholipids significantly enhance cell adhesion to the SIP, and thus play a significant role in the cell-SIP binding mechanism. Furthermore, the hydrophobicity of the SIP layer was found to be considerably higher when compared with a non-imprinted polymer layer (NIP), an effect that could not be attributed to the presence of cavities on the surface of the SIP layer. Therefore, we suggest that the role of phospholipids in the SIP recognition mechanism is mediated by long range hydrophobic forces. (C) 2017 Elsevier B.V. All rights reserved.</p

Studying the Drug Delivery Kinetics of Nanosponges Using a MIP-Based Thermal Sensing Platform

The implementation of Molecularly Imprinted Polymers (MIPs) into sensing systems has been demonstrated abundantly over the past few decades. In this article, a novel application for an MIP-based thermal sensing platform is introduced by using the sensor to characterize the drug release kinetics of a nanoporous silver-organic framework. This Ag nanoporous matrix was loaded with acetylsalicylic acid (aspirin) which was used as a model drug compound in this study. The drug elution properties were studied by placing the nanoporous matrix in phosphate buffered saline solution for two days and measuring the drug concentration at regular time intervals. To this extent, an acrylamide-based MIP was synthesized that was able to detect aspirin in a specific and selective manner. Rebinding of the template to the MIP was analyzed using a thermal sensor platform. The results illustrate that the addition of aspirin into the sensing chamber leads to a concentration-dependent increase in the phase shift of a thermal wave that propagates through the MIP-coated sensor chip. After constructing a dose-response curve, this system was used to study the drug release kinetics of the nanoporous matrix, clearly demonstrating that the metalorganic framework releases the drug steadily over the course of the first hour, after which the concentration reaches a plateau. These findings were further confirmed by UV–Visible spectroscopy, illustrating a similar time-dependent release in the same concentration range, which demonstrates that the MIP-based platform can indeed be used as a low-cost straightforward tool to assess the efficacy of drug delivery systems in a lab environmen

Substrate displacement colorimetry for the detection of diarylethylamines

In this work, a novel detection assay for the new psychoactive substance (NPS) 2-methoxiphenidine (2-MXP) and other diarylethylamines is introduced. The assay is based on the competitive displacement of dye molecules from molecularly imprinted polymers (MIPs) by the target molecule. The assay was fully characterized by studying the affinity of the MIP for six common dyes, expressed as the binding factor (BF). The results of this study indicate that the mathematical relationship between the BF of a dye and the imprinting factor (IF) for the target could be used for the prediction of the efficacy of the displacement assay. Dye-loaded MIP particles where incubated with the target, two adulterants and two legal pharmacological compounds. The target has a higher affinity for the MIP than the dye and displaces it out of the nanocavities of the receptor leading to a colour change in the filtrate that can be observed with the naked eye. Incubation of the MIP particles with the adulterants and legal medicines did not result in any observable change in absorbance. The robust, fast and low-cost nature of the assay, combined with its tailorable selectivity and generic nature, illustrate its potential as a pre-screening tool for the identification of narcotic substances in unidentified powders. Keywords: Molecularly imprinted polymer, displacement assay, colorimetry, new psychoactive substance identificatio

Single-Shot Detection of Neurotransmitters in Whole-Blood Samples by Means of the Heat-Transfer Method in Combination with Synthetic Receptors.

Serotonin is an important neurotransmitter that plays a major role in the pathogenesis of a variety of conditions, including psychiatric disorders. The detection of serotonin typically relies on high-performance liquid chromatography (HPLC), an expensive technique that requires sophisticated equipment and trained personnel, and is not suitable for point-of-care applications. In this contribution, we introduce a novel sensor platform that can measure spiked neurotransmitter concentrations in whole blood samples in a fast and low-cost manner by combining synthetic receptors with a thermal readout technique-the heat-transfer method. In addition, the design of a miniaturized version of the sensing platform is presented that aims to bridge the gap between measurements in a laboratory setting and point-of-care measurements. This fully automated and integrated, user-friendly design features a capillary pumping unit that is compatible with point-of-care sampling techniques such as a blood lancet device (sample volume-between 50 µL and 300 µL). Sample pre-treatment is limited to the addition of an anti-coagulant. With this fully integrated setup, it is possible to successfully discriminate serotonin from a competitor neurotransmitter (histamine) in whole blood samples. This is the first demonstration of a point-of-care ready device based on synthetic receptors for the screening of neurotransmitters in complex matrices, illustrating the sensor's potential application in clinical research and diagnosis of e.g., early stage depression

Dipstick sensor based on molecularly imprinted polymer-coated screen-printed electrodes for the single-shot detection of glucose in urine samples—from fundamental study toward point-of-care application

Glucose biosensors play an extremely important role in health care systems worldwide. Therefore, the field continues to attract significant attention leading to the development of innovative technologies. Due to their characteristics, Molecularly Imprinted Polymers (MIPs) represent a promising alternative to commercial enzymatic sensors. In this work, a low-cost, flexible MIP-based platform for glucose sensing by integrating MIP particles directly into screen-printed electrodes (SPEs) is realized. The sensor design allows the detection of glucose via two different transducer principles, the so-called “heat-transfer method” (HTM) and electrochemical impedance spectroscopy (EIS). The sensitivity and selectivity of the sensor are demonstrated by comparing the responses obtained toward three different saccharides. Furthermore, the application potential of the MIP-SPE sensor is demonstrated by analyzing the response in urine samples, showing a linear range of 14.38–330 µm with HTM and 1.37–330 µm with EIS. To bring the sensor closer to a real life application, a handheld dipstick sensor is developed, allowing the single-shot detection of glucose in urine using EIS. This study illustrates that the simplicity of the dipstick readout coupled with the straightforward manufacturing process opens up the possibility for mass production, making this platform a very attractive alternative to commercial glucose sensors

A Novel Biomimetic Tool for Assessing Vitamin K Status Based on Molecularly Imprinted Polymers

Vitamin K was originally discovered as a cofactor required to activate clotting factors and has recently been shown to play a key role in the regulation of soft tissue calcification. This property of vitamin K has led to an increased interest in novel methods for accurate vitamin K detection. Molecularly Imprinted Polymers (MIPs) could offer a solution, as they have been used as synthetic receptors in a large variety of biomimetic sensors for the detection of similar molecules over the past few decades, because of their robust nature and remarkable selectivity. In this article, the authors introduce a novel imprinting approach to create a MIP that is able to selectively rebind vitamin K1. As the native structure of the vitamin does not allow for imprinting, an alternative imprinting strategy was developed, using the synthetic compound menadione (vitamin K3) as a template. Target rebinding was analyzed by means of UV-visible (UV-VIS) spectroscopy and two custom-made thermal readout techniques. This analysis reveals that the MIP-based sensor reacts to an increasing concentration of both menadione and vitamin K1. The Limit of Detection (LoD) for both compounds was established at 700 nM for the Heat Transfer Method (HTM), while the optimized readout approach, Thermal Wave Transport Analysis (TWTA), displayed an increased sensitivity with a LoD of 200 nM. The sensor seems to react to a lesser extent to Vitamin E, the analogue under study. To further demonstrate its potential application in biochemical research, the sensor was used to measure the absorption of vitamin K in blood serum after taking vitamin K supplements. By employing a gradual enrichment strategy, the sensor was able to detect the difference between baseline and peak absorption samples and was able to quantify the vitamin K concentration in good agreement with a validation experiment using High-Performance Liquid Chromatography (HPLC). In this way, the authors provide a first proof of principle for a low-cost, straightforward, and label-free vitamin K sensor

A Review on Synthetic Receptors for Bioparticle Detection Created by Surface-Imprinting Techniques-From Principles to Applications

© 2016 American Chemical Society. The strong affinity of biological receptors for their targets has been studied for many years. Noncovalent interactions between these natural recognition elements and their ligands form the basis for a broad range of biosensor applications. Although these sensing platforms are usually appreciably sensitive and selective, certain drawbacks are associated with biological receptors under nonphysiological conditions in terms of temperature, pH, or ionic strength. Therefore, there are considerable efforts to mimic such molecular interactions with robust, synthetic receptors. Molecular imprinting is the best-known technique to obtain antibody mimics by synthesizing a polymer matrix in the presence of a template species, such as molecules or larger aggregates. Extraction of the template results in sterically and functionally adapted binding cavities in or on a porous matrix. Although in principle possible, the detection of larger bioparticles such as proteins, microorganisms, or cells remains challenging when using the classical MIP concept. To tackle inherent difficulties, extending the concept of molecular imprinting toward surface imprinting is a promising approach: Here, binding cavities are formed directly on the surface of a cross-linked polymer layer, thus facilitating the removal of the templates. This article reviews the main surface-imprinting techniques and focuses on the implementation of surface-imprinted polymers (SIPs) into various biomimetic sensors and related applications. In addition, we provide an outlook on emerging research on surface imprinting and the development of biomimetic tools for diagnostic purposes.status: publishe

Colorimetric Sensing of Amoxicillin Facilitated by Molecularly Imprinted Polymers

The scope of the presented research orientates itself towards the development of a Molecularly Imprinted Polymer (MIP)-based dye displacement assay for the colorimetric detection of the antibiotic amoxicillin in aqueous medium. With this in mind, the initial development of an MIP capable of such a task sets focus on monolithic bulk polymerization to assess monomer/crosslinker combinations that have potential towards the binding of amoxicillin. The best performing composition (based on specificity and binding capacity) is utilized in the synthesis of MIP particles by emulsion polymerization, yielding particles that prove to be more homogenous in size and morphology compared to that of the crushed monolithic MIP, which is an essential trait when it comes to the accuracy of the resulting assay. The specificity and selectivity of the emulsion MIP proceeds to be highlighted, demonstrating a higher affinity towards amoxicillin compared to other compounds of the aminopenicillin class (ampicillin and cloxacillin). Conversion of the polymeric receptor is then undertaken, identifying a suitable dye for the displacement assay by means of binding experiments with malachite green, crystal violet, and mordant orange. Once identified, the optimal dye is then loaded onto the synthetic receptor, and the displaceability of the dye deduced by means of a dose response experiment. Alongside the sensitivity, the selectivity of the assay is scrutinized against cloxacillin and ampicillin. Yielding a dye displacement assay that can be used (semi-)quantitatively in a rapid manner