Molecularly imprinted poly(methacrylic acid) based QCM biosensor for selective determination of L-tryptophan

Sensing with Molecularly Imprinted Membranes on Two-Dimensional Solid-Supported Substrates

Molecularly imprinted membranes (MIMs) have been a focal research interest since 1990, representing a breakthrough in the integration of target molecules into membrane structures for cutting-edge sensing applications. This paper traces the developmental history of MIMs, elucidating the diverse methodologies employed in their preparation and characterization on two-dimensional solid-supported substrates. We then explore the principles and diverse applications of MIMs, particularly in the context of emerging technologies encompassing electrochemistry, surface-enhanced Raman scattering (SERS), surface plasmon resonance (SPR), and the quartz crystal microbalance (QCM). Furthermore, we shed light on the unique features of ion-sensitive field-effect transistor (ISFET) biosensors that rely on MIMs, with the notable advancements and challenges of point-of-care biochemical sensors highlighted. By providing a comprehensive overview of the latest innovations and future trajectories, this paper aims to inspire further exploration and progress in the field of MIM-driven sensing technologies.

Innovative approaches to suppress non-specific adsorption in molecularly imprinted polymers for sensing applications

Molecularly imprinted polymers (MIPs) are synthetic antibodies developed to bind selectively with specific molecules. They function through a particular recognition process involving their cavities and functional groups. Nevertheless, functional groups located outside these cavities are the main cause of non-specific molecule binding, thus reducing the effectiveness of MIPs in sensing applications. This work focused on enhancing the selectivity and performance of MIPs through electrostatic modification with surfactants. The study investigates the use of two surfactants, namely sodium dodecyl sulfate (SDS) and cetyl trimethyl ammonium bromide (CTAB), to eliminate non-specific adsorption in MIPs. The binding isotherms of the target molecule sulfamethoxazole (SMX) on MIPs and non-imprinted polymers (NIPs) were analyzed, showing higher adsorption capacity of MIPs due to the specific cavities. The modification with SDS or CTAB effectively eliminated non-specific adsorption in MIPs. The kinetic adsorption behavior further demonstrated the efficacy of MIP+--SDS/CTAB in the selective adsorption of SMX. Calibration curves showcase the methodology's analytical capabilities, achieving low limit of detection for SMX 6 ng mL-1 using MIP +-SDS. The stability study confirmed that the developed MIP +/--SDS/CTAB remains stable even at high temperatures, demonstrating its suitability for on-site applications. The methodology was successfully applied to detect SMX in milk and water samples, achieving promising recoveries. Overall, the electrostatic modification of MIPs with surfactants emerges as a valuable strategy for enhancing selectivity and performance in target molecule recognition and detection.

Electric Field-Assisted Molecularly Imprinted Polymer-Modified QCM Sensor for Enhanced Detection of Immunoglobulin

In this study, an electric-field-assisted molecularly imprinted polymer (EFAMIP) as an enhanced form of MIP was developed to improve the MIP-modified quartz crystal microbalance (QCM) biosensors. While exerting a vertical electric field, polymerization of methacrylic acid in the presence of immunoglobulin G (IgG) as the template was initiated, and later, after the template removal process, the EFAMIPs were obtained. The polymer surface characterization was conducted by using a scanning electron microscope. The impact of electric field direction on IgG binding sites, forming either EFAMIP-Fab or EFAMIP-Fc, was assessed. Next, the static measurement results in liquid for EFAMIP-modified QCM and MIP-modified QCM were compared. While encompassing IgG, EFAMIP-modified QCMs exhibited up to a 113.5% higher frequency shift than typical MIP in time-limited detection. The final frequency shift of EFAMIP, which determines the detection limit of IgG, was improved up to 12.5% compared to typical MIP. Moreover, the EFAMIP-Fab performance was promising for the selective detection of IgG in a solution containing different types of immunoglobulins.

Magnetic dummy template molecularly imprinted particles functionalized with dendritic nanoclusters for selective enrichment and determination of 4-methylnitrosamino-1-(3-pyridyl)-1-butanone (NNK) in tobacco products

The compound 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), one of the tobacco specific nitrosamines (TSNAs), is widely recognized as a major carcinogen found in tobacco products, environmental tobacco smoke and wastewater. Thus, a selective enrichment and sensitive detection method for monitoring the risk of NNK exposure is highly desirable. In this study, a magnetic molecularly imprinted polymer (MMIP) functionalized with dendritic nanoclusters was synthesized to selectively recognize NNK via the dummy template imprinting strategy, aiming to avoid residual template leakage and increase the imprinting efficiency. The nanocomposites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, as well as vibrating sample magnetometry (VSM) and nitrogen adsorption/desorption analysis. The resulting MMIPs exhibited high adsorption capacity, fast binding kinetics and good selectivity for trace amounts of NNK. A rapid, low cost and efficient method for detecting NNK in tobacco products was established using magnetic dispersive solid-phase extraction coupled with HPLC-DAD with a good linear range of 0.1-250 μg mL^-1. The limit of detection (LOD) and limit of quantification (LOQ) of NNK were 13.5 and 25.0 ng mL^-1, respectively. The average recoveries were 87.8-97.3% with RSDs lower than 3%. The results confirmed that the MMIPs could be used as an excellent selective adsorbent for NNK, with potential applications in the pretreatment of tobacco products.

Recent molecularly imprinted polymers applications in bioanalysis

Molecular imprinted polymers (MIPs) as extraordinary compounds with unique features have presented a wide range of applications and benefits to researchers. In particular when used as a sorbent in sample preparation methods for the analysis of biological samples and complex matrices. Its application in the extraction of medicinal species has attracted much attention and a growing interest. This review focus on articles and research that deals with the application of MIPs in the analysis of components such as biomarkers, drugs, hormones, blockers and inhibitors, especially in biological matrices. The studies based on MIP applications in bioanalysis and the deployment of MIPs in high-throughput settings and optimization of extraction methods are presented. A review of more than 200 articles and research works clearly shows that the superiority of MIP techniques lies in high accuracy, reproducibility, sensitivity, speed and cost effectiveness which make them suitable for clinical usage. Furthermore, this review present MIP-based extraction techniques and MIP-biosensors which are categorized on their classes based on common properties of target components. Extraction methods, studied sample matrices, target analytes, analytical techniques and their results for each study are described. Investigations indicate satisfactory results using MIP-based bioanalysis. According to the increasing number of studies on method development over the last decade, the use of MIPs in bioanalysis is growing and will further expand the scope of MIP applications for less studied samples and analytes.

Design of surface nanostructures for chirality sensing based on quartz crystal microbalance

Quartz crystal microbalance (QCM) has been widely used for various sensing applications, including chirality detection due to the high sensitivity to nanogram or picogram mass changes, fast response, real-time detection, easy operation, suitability in different media, and low experimental cost. The sensing performance of QCM is dependent on the surface design of the recognition layers. Various strategies have been employed for studying the relationship between the structural features and the specific detection of chiral isomers. This review provides an overview of the construction of chiral sensing layers by various nanostructures and materials in the QCM system, which include organic molecules, supermolecular assemblies, inorganic nanostructures, and metal surfaces. The sensing mechanisms based on these surface nanostructures and the related potentials for chiral detection by the QCM system are also summarized.

Immuno-affinity Potent Strip with Pre-Embedded Intermixed PEDOT:PSS Conductive Polymers and Graphene Nanosheets for Bio-Ready Electrochemical Biosensing of Central Nervous System Injury Biomarkers

Future point-of-care (PoC) and wearable electrochemical biosensors explore new technology solutions to eliminate the need for multistep electrode modification and functionalization, overcome the limited reproducibility, and automate the sensing steps. In this work, a new screen-printed immuno-biosensor strip is engineered and characterized using a hybrid graphene nanosheet intermixed with the conductive poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) polymers, all embedded within the base carbon matrix (GiPEC) of the screen-printing ink. This intermixed nanocomposite ink is chemically designed for self-containing the "carboxyl" functional groups as the most specific chemical moiety for protein immobilization on the electrodes. The GiPEC ink enables capturing the target antibodies on the electrode without any need for extra surface preparation. As a proof of concept, the performance of the non-functionalized ready-to-immobilize strips was assessed for the detection of glial fibrillary acidic protein (GFAP) as a known central nervous system injury blood biomarker. This immuno-biosensor exhibits the limit of detection of 281.7 fg mL^-1 (3 signal-to-noise ratio) and the sensitivity of 322.6 Ω mL pg^-1 mm^-2 within the clinically relevant linear detection range from 1 pg mL^-1 to 10 ng mL^-1. To showcase its potential PoC application, the bio-ready strip is embedded inside a capillary microfluidic device and automates electrochemical quantification of GFAP spiked in phosphate-buffered saline and the human serum. This new electrochemical biosensing platform can be further adapted for the detection of various protein biomarkers with the application in realizing on-chip immunoassays.

A Review of Sensors and Biosensors Modified with Conducting Polymers and Molecularly Imprinted Polymers Used in Electrochemical Detection of Amino Acids: Phenylalanine, Tyrosine, and Tryptophan

Recently, the studies on developing sensors and biosensors-with an obvious interdisciplinary character-have drawn the attention of many researchers specializing in various fundamental, but also complex domains such as chemistry, biochemistry, physics, biophysics, biology, bio-pharma-medicine, and bioengineering. Along these lines, the present paper is structured into three parts, and is aimed at synthesizing the most relevant studies on the construction and functioning of versatile devices, of electrochemical sensors and biosensors, respectively. The first part presents examples of the most representative scientific research focusing on the role and the importance of the phenylalanine, tyrosine, and tryptophan amino acids, selected depending on their chemical structure and their impact on the central nervous system. The second part is dedicated to presenting and exemplifying conductor polymers and molecularly imprinted polymers used as sensitive materials in achieving electrochemical sensors and biosensors. The last part of the review analyzes the sensors and biosensors developed so far to detect amino acids with the aid of conductor polymers and molecularly imprinted polymers from the point of view of the performances obtained, with emphasis on the detection methods, on the electrochemical reactions that take place upon detection, and on the electroanalytical performances. The present study was carried out with a view to highlighting, for the benefit of specialists in medicine and pharmacy, the possibility of achieving and purchasing efficient devices that might be used in the quality control of medicines, as well as in studying and monitoring diseases associated with these amino acids.

Acoustic Biosensors and Microfluidic Devices in the Decennium: Principles and Applications

Lab-on-a-chip (LOC) technology has gained primary attention in the past decade, where label-free biosensors and microfluidic actuation platforms are integrated to realize such LOC devices. Among the multitude of technologies that enables the successful integration of these two features, the piezoelectric acoustic wave method is best suited for handling biological samples due to biocompatibility, label-free and non-invasive properties. In this review paper, we present a study on the use of acoustic waves generated by piezoelectric materials in the area of label-free biosensors and microfluidic actuation towards the realization of LOC and POC devices. The categorization of acoustic wave technology into the bulk acoustic wave and surface acoustic wave has been considered with the inclusion of biological sample sensing and manipulation applications. This paper presents an approach with a comprehensive study on the fundamental operating principles of acoustic waves in biosensing and microfluidic actuation, acoustic wave modes suitable for sensing and actuation, piezoelectric materials used for acoustic wave generation, fabrication methods, and challenges in the use of acoustic wave modes in biosensing. Recent developments in the past decade, in various sensing potentialities of acoustic waves in a myriad of applications, including sensing of proteins, disease biomarkers, DNA, pathogenic microorganisms, acoustofluidic manipulation, and the sorting of biological samples such as cells, have been given primary focus. An insight into the future perspectives of real-time, label-free, and portable LOC devices utilizing acoustic waves is also presented. The developments in the field of thin-film piezoelectric materials, with the possibility of integrating sensing and actuation on a single platform utilizing the reversible property of smart piezoelectric materials, provide a step forward in the realization of monolithic integrated LOC and POC devices. Finally, the present paper highlights the key benefits and challenges in terms of commercialization, in the field of acoustic wave-based biosensors and actuation platforms.

Molecularly Imprinted Polymers for Chemical Sensing: A Tutorial Review

The field of molecularly imprinted polymer (MIP)-based chemosensors has been experiencing constant growth for several decades. Since the beginning, their continuous development has been driven by the need for simple devices with optimum selectivity for the detection of various compounds in fields such as medical diagnosis, environmental and industrial monitoring, food and toxicological analysis, and, more recently, the detection of traces of explosives or their precursors. This review presents an overview of the main research efforts made so far for the development of MIP-based chemosensors, critically discusses the pros and cons, and gives perspectives for further developments in this field.