Molecularly Imprinted Nanomaterials for Sensor Applications

An Overview on Recent Advances in Biomimetic Sensors for the Detection of Perfluoroalkyl Substances

Per- and polyfluoroalkyl substances (PFAS) are a class of materials that have been widely used in the industrial production of a wide range of products. After decades of bioaccumulation in the environment, research has demonstrated that these compounds are toxic and potentially carcinogenic. Therefore, it is essential to map the extent of the problem to be able to remediate it properly in the next few decades. Current state-of-the-art detection platforms, however, are lab based and therefore too expensive and time-consuming for routine screening. Traditional biosensor tests based on, e.g., lateral flow assays may struggle with the low regulatory levels of PFAS (ng/mL), the complexity of environmental matrices and the presence of coexisting chemicals. Therefore, a lot of research effort has been directed towards the development of biomimetic receptors and their implementation into handheld, low-cost sensors. Numerous research groups have developed PFAS sensors based on molecularly imprinted polymers (MIPs), metal-organic frameworks (MOFs) or aptamers. In order to transform these research efforts into tangible devices and implement them into environmental applications, it is necessary to provide an overview of these research efforts. This review aims to provide this overview and critically compare several technologies to each other to provide a recommendation for the direction of future research efforts focused on the development of the next generation of biomimetic PFAS sensors.

Molecularly imprinted polymer-based optical immunosensors

Molecularly imprinted polymers (MIPs) are artificial antibodies for a target molecule. The review focuses mainly on mechanistic steps involved in forming MIPs and the role of co-monomers and porogen. In addition, the electronic transition between different energy levels is explained with the help of the Jablonski diagram. Diverse receptor and target molecules for anchoring artificial MIPs are discussed, accentuating the synergetic effects obtained. The binding efficiency, selectivity, and sensitivity of various optical sensors are discussed intensively. In addition to this, we focused on synthesis, physical forms, characterization techniques, and microorganism detection of imprinted polymers. A brief investigation on the use of MIPs in cancer diagnosis is also included, and attention is extended to the important challenges faced in using imprinted polymers.

A Physical Model to Describe the Motion Behavior of BNNSs under Nanosecond Pulses

This paper presents a physical model that provides a comprehensive understanding of the motion behavior of boron nitride nanosheets (BNNSs) immersed in ultrapure deionized water and subjected to a series of nanosecond pulses. In a study conducted by Y. Mi et al. The authors explored the global alignment behavior of BNNSs and fitted the experimental data with an exponential decay function. However, this function lacks clear physical mechanisms and the significance of the fitting parameters remains unclear. To address this issue, we have developed a kinetic model that explicitly describes the underlying physical mechanisms. Furthermore, we propose a simplified mathematical model that not only predicts the displacement of BNNSs but also estimates the total time, velocity, and acceleration of the motion process.

pH-responsive gelatin polymer-coated silica-based mesoporous composites for the sustained-release of indomethacin

This paper prepared drug-loaded mesoporous silica composites with a pH-responsive type. These composites were prepared by using three-dimensional caged silica (SBA-16) as the carrier, 3-aminopropyl trimethoxysilane (APTMS) as the silane coupling agent, and indomethacin (IMC) as the loaded drug, respectively. The drug-loaded precursor NH₂-SBA-16@IMC was prepared by solution diffusion adsorption. Finally, the pH-responsive drug-loaded composites NH₂-SBA-16@IMC@GA were synthesized by wrapping the NH₂-SBA-16@IMC with a condensation polymer of gelatin and glutaraldehyde. The composition and structure of the drug-loaded composites were characterized by FT-IR, XRD, TG, SEM, TEM, and N₂ adsorption-desorption. The in vitro simulated release performance of the drug-loaded composites was investigated at 37 °C under three pH conditions. The results show that the NH₂-SBA-16@IMC@GA can be released in response to specific pH environment, which can effectively control the release speed of the indomethacin.

Bio-Inspired Imprinting Materials for Biomedical Applications

Inspired by the recognition mechanism of biological molecules, molecular imprinting techniques (MITs) are imparted with numerous merits like excellent stability, recognition specificity, adsorption properties, and easy synthesis processes, and thus broaden the avenues for convenient fabrication protocol of bio-inspired molecularly imprinted polymers (MIPs) with desirable functions to satisfy the extensive demands of biomedical applications. Herein, the recent research progress made with respect to bio-inspired imprinting materials is discussed in this review. First, the underlying mechanism and basic components of a typical molecular imprinting procedure are briefly explored. Then, emphasis is put on the introduction of diverse MITs and novel bio-inspired imprinting materials. Following these two sections, practical applications of MIPs in the field of biomedical science are focused on. Last but not least, perspectives on the remaining challenges and future development of bio-inspired imprinting materials are presented.

Green Chemistry and Molecularly Imprinted Membranes

Technological progress has made chemistry assume a role of primary importance in our daily life. However, the worsening of the level of environmental pollution is increasingly leading to the realization of more eco-friendly chemical processes due to the advent of green chemistry. The challenge of green chemistry is to produce more and better while consuming and rejecting less. It represents a profitable approach to address environmental problems and the new demands of industrial competitiveness. The concept of green chemistry finds application in several material syntheses such as organic, inorganic, and coordination materials and nanomaterials. One of the different goals pursued in the field of materials science is the application of GC for producing sustainable green polymers and membranes. In this context, extremely relevant is the application of green chemistry in the production of imprinted materials by means of its combination with molecular imprinting technology. Referring to this issue, in the present review, the application of the concept of green chemistry in the production of polymeric materials is discussed. In addition, the principles of green molecular imprinting as well as their application in developing greenificated, imprinted polymers and membranes are presented. In particular, green actions (e.g., the use of harmless chemicals, natural polymers, ultrasound-assisted synthesis and extraction, supercritical CO2, etc.) characterizing the imprinting and the post-imprinting process for producing green molecularly imprinted membranes are highlighted.

Plastic Antibody of Polypyrrole/Multiwall Carbon Nanotubes on Screen-Printed Electrodes for Cystatin C Detection

This work reports the design of a novel plastic antibody for cystatin C (Cys-C), an acute kidney injury biomarker, and its application in point-of-care (PoC) testing. The synthetic antibody was obtained by tailoring a molecularly imprinted polymer (MIP) on a carbon screen-printed electrode (SPE). The MIP was obtained by electropolymerizing pyrrole (Py) with carboxylated Py (Py-COOH) in the presence of Cys-C and multiwall carbon nanotubes (MWCNTs). Cys-C was removed from the molecularly imprinted poly(Py) matrix (MPPy) by urea treatment. As a control, a non-imprinted poly(Py) matrix (NPPy) was obtained by the same procedure, but without Cys-C. The assembly of the MIP material was evaluated in situ by Raman spectroscopy and the binding ability of Cys-C was evaluated by the cyclic voltammetry (CV) and differential pulse voltammetry (DPV) electrochemical techniques. The MIP sensor responses were measured by the DPV anodic peaks obtained in the presence of ferro/ferricyanide. The peak currents decreased linearly from 0.5 to 20.0 ng/mL of Cys-C at each 20 min successive incubation and a limit of detection below 0.5 ng/mL was obtained at pH 6.0. The MPPy/SPE was used to analyze Cys-C in spiked serum samples, showing recoveries <3%. This device showed promising features in terms of simplicity, cost and sensitivity for acute kidney injury diagnosis at the point of care.

Point-of-Care Diagnostics: Molecularly Imprinted Polymers and Nanomaterials for Enhanced Biosensor Selectivity and Transduction

Significant healthcare disparities resulting from personal wealth, circumstances of birth, education level, and more are internationally prevalent. As such, advances in biomedical science overwhelmingly benefit a minority of the global population. Point-of-Care Testing (POCT) can contribute to societal equilibrium by making medical diagnostics affordable, convenient, and fast. Unfortunately, conventional POCT appears stagnant in terms of achieving significant advances. This is attributed to the high cost and instability associated with conventional biorecognition: primarily antibodies, but nucleic acids, cells, enzymes, and aptamers have also been used. Instead, state-of-the-art biosensor researchers are increasingly leveraging molecularly imprinted polymers (MIPs) for their high selectivity, excellent stability, and amenability to a variety of physical and chemical manipulations. Besides the elimination of conventional bioreceptors, the incorporation of nanomaterials has further improved the sensitivity of biosensors. Herein, modern nanobiosensors employing MIPs for selectivity and nanomaterials for improved transduction are systematically reviewed. First, a brief synopsis of fabrication and wide-spread challenges with selectivity demonstration are presented. Afterward, the discussion turns to an analysis of relevant case studies published in the last five years. The analysis is given through two lenses: MIP-based biosensors employing specific nanomaterials and those adopting particular transduction strategies. Finally, conclusions are presented along with a look to the future through recommendations for advancing the field. It is hoped that this work will accelerate successful efforts in the field, orient new researchers, and contribute to equitable health care for all.

Molecular-Imprinting-Based Surface-Enhanced Raman Scattering Sensors

Molecularly imprinted polymers (MIPs) receive extensive interest, owing to their structure predictability, recognition specificity, and application universality as well as robustness, simplicity, and inexpensiveness. Surface-enhanced Raman scattering (SERS) is regarded as an ideal optical detection candidate for its unique features of fingerprint recognition, nondestructive property, high sensitivity, and rapidity. Accordingly, MIP based SERS (MIP-SERS) sensors have attracted significant research interest for versatile applications especially in the field of chemo- and bioanalysis, showing excellent identification and detection performances. Herein, we comprehensively review the recent advances in MIP-SERS sensors construction and applications, including sensing principles and signal enhancement mechanisms, focusing on novel construction strategies and representative applications. First, the basic structure of the MIP-SERS sensors is briefly outlined. Second, novel imprinting strategies are highlighted, mainly including multifunctional monomer imprinting, dummy template imprinting, living/controlled radical polymerization, and stimuli-responsive imprinting. Third, typical application of MIP-SERS sensors in chemo/bioanalysis is summarized from both small and macromolecular aspects. Lastly, the challenges and perspectives of the MIP-SERS sensors are proposed, orienting sensitivity improvement and application expanding.

Magnetic molecularly imprinted electrochemical sensors: A review

The preparation and practical applications of molecularly imprinted electrochemical sensors (MIECSs) remain challenging due to issues involving electrode surface renewal modes, low adsorption capacities, and sample preparation speeds. To solve these issues, magnetic molecularly imprinted electrochemical sensors (MMIECSs) have been extensively explored by various groups. Recently, MMIECSs fabricated based on diverse strategies have yielded insight into the development of MIECSs, and they have provided effective paths for sample preparation, immobilization and renewal of molecularly imprinted polymers (MIPs) on the electrode surface, leading to promising performances of MIECSs. This review comprehensively describes the research advances for various types of MMIECSs and their applications in the fields of food safety, environmental monitoring, and clinical and pharmaceutical analysis. Based on our understanding of MMIECSs, the literature in this field is thoroughly explored and classified in this review. The challenges existing in this research area and some potential strategies for the rational design of high-performance MMIECS are also outlined.

Mn-doped ZnS quantum dots-chlorin e6 shows potential as a treatment for chondrosarcoma: an in vitro study

Chondrosarcoma is the second-most malignant cancer of the bone and routine treatments such as chemotherapy and radiotherapy have not responded to the treatment of this cancer. Due to the resistance of chondrosarcoma to radiotherapy, the combination of therapeutic methods has been considered in recent years. In this study, a novel combination approach is used that allows photodynamic therapy to be activated by X-rays. The synthesis of Mn-doped zinc sulphide (ZnS) quantum dots was carried out and chlorin e6 photosensitiser attached by covalent and non-covalent methods and their application as an intracellular light source for photodynamic activation was investigated. The toxicity of each nanoparticles was evaluated on chondrosarcoma cancer cells (SW1353) before and after radiation. Also, the effect nanoparticle-photosensitiser conjugated type was investigated in the therapeutic efficacy. The characterisation test (SEM, TEM, EDS, TGA, XRD and ICP analyses) was shown successful synthesis of Mn-doped ZnS quantum dots. Chondrosarcoma cancer cell viability was significantly reduced when cells were treated with MPA-capped Mn-doped ZnS quantum dots-chlorin e6 with spermine linker and with covalent attachment (P ≤ 0.001). These results indicate that X-ray can activate the quantum dot complexes for cancer treatment, which can be a novel method for treatment of chondrosarcoma.

A Spectral Probe for Detection of Aluminum (III) Ions Using Surface Functionalized Gold Nanoparticles

A simple green route has been developed for the synthesis of casein peptide functionalized gold nanoparticles (AuNPs), in which casein peptide acts as a reducing as well as the stabilizing agent. In this report, AuNPs have been characterized on the basis of spectroscopic and microscopic results; which showed selective and sensitive response toward Al3+ in aqueous media, and Al3+ induces aggregation of AuNPs. The sensing study performed for Al3+ revealed that the color change from red to blue was due to a red-shift in the surface plasmon resonance (SPR) band and the formation of aggregated species of AuNPs. The calibration curve determines the detection limit (LOD) for Al3+ about 20 ppb (0.067 μM) is presented using both decrease and increase in absorbance at 530 and 700 nm, respectively. This value is considerably lower than the higher limit allowed for Al3+ in drinking water by the world health organization (WHO) (7.41 μM), representing enough sensitivity to protect water quality. The intensity of the red-shifted band increases with linear pattern upon the interaction with different concentrations of Al3+, thus the possibility of producing unstable AuNPs aggregates. The method is successfully used for the detection of Al3+ in water samples collected from various sources, human urine and ionic drink. The actual response time required for AuNPs is about 1 min, this probe also have several advantages, such as ease of synthesis, functionalization and its use, high sensitivity, and enabling on-site monitoring.

Molecularly imprinted polymers for sample preparation and biosensing in food analysis: Progress and perspectives

Molecularly imprinted polymers (MIPs) are biomimetics which can selectively bind to analytes of interest. One of the most interesting areas where MIPs have shown the biggest potential is food analysis. MIPs have found use as sorbents in sample preparation attributed to the high selectivity and high loading capacity. MIPs have been intensively employed in classical solid-phase extraction and solid-phase microextraction. More recently, MIPs have been combined with magnetic bead extraction, which greatly simplifies sample handling procedures. Studies have consistently shown that MIPs can effectively minimize complex food matrix effects, and improve recoveries and detection limits. In addition to sample preparation, MIPs have also been viewed as promising alternatives to bio-receptors due to the inherent molecular recognition abilities and the high stability in harsh chemical and physical conditions. MIPs have been utilized as receptors in biosensing platforms such as electrochemical, optical and mass biosensors to detect various analytes in food. In this review, we will discuss the current state-of-the-art of MIP synthesis and applications in the context of food analysis. We will highlight the imprinting methods which are applicable for imprinting food templates, summarize the recent progress in using MIPs for preparing and analysing food samples, and discuss the current limitations in the commercialisation of MIPs technology. Finally, future perspectives will be given.

Recent Progress in Electrochemical Biosensors for Glycoproteins

This review provides an overview of recent progress in the development of electrochemical biosensors for glycoproteins. Electrochemical glycoprotein sensors are constructed by combining metal and carbon electrodes with glycoprotein-selective binding elements including antibodies, lectin, phenylboronic acid and molecularly imprinted polymers. A recent trend in the preparation of glycoprotein sensors is the successful use of nanomaterials such as graphene, carbon nanotube, and metal nanoparticles. These nanomaterials are extremely useful for improving the sensitivity of glycoprotein sensors. This review focuses mainly on the protocols for the preparation of glycoprotein sensors and the materials used. Recent improvements in glycoprotein sensors are discussed by grouping the sensors into several categories based on the materials used as recognition elements.

Design and Electrochemical Study of Platinum-Based Nanomaterials for Sensitive Detection of Nitric Oxide in Biomedical Applications

The extensive physiological and regulatory roles of nitric oxide (NO) have spurred the development of NO sensors, which are of critical importance in neuroscience and various medical applications. The development of electrochemical NO sensors is of significant importance, and has garnered a tremendous amount of attention due to their high sensitivity and selectivity, rapid response, low cost, miniaturization, and the possibility of real-time monitoring. Nanostructured platinum (Pt)-based materials have attracted considerable interest regarding their use in the design of electrochemical sensors for the detection of NO, due to their unique properties and the potential for new and innovative applications. This review focuses primarily on advances and insights into the utilization of nanostructured Pt-based electrode materials, such as nanoporous Pt, Pt and PtAu nanoparticles, PtAu nanoparticle/reduced graphene oxide (rGO), and PtW nanoparticle/rGO-ionic liquid (IL) nanocomposites, for the detection of NO. The design, fabrication, characterization, and integration of electrochemical NO sensing performance, selectivity, and durability are addressed. The attractive electrochemical properties of Pt-based nanomaterials have great potential for increasing the competitiveness of these new sensors and open up new opportunities in the creation of novel NO-sensing technologies for biological and medical applications.

Silica nanoparticle based techniques for extraction, detection, and degradation of pesticides

Silica nanoparticles (SiNPs) find applications in the fields of drug delivery, catalysis, immobilization and sensing. Their synthesis can be mediated in a facile manner and they display broad range compatibility and stability. Their existence in the form of spheres, wires and sheets renders them suitable for varied purposes. This review summarizes the use of silica nanostructures in developing techniques for extraction, detection and degradation of pesticides. Silica nanostructures on account of their sorbent properties, porous nature and increased surface area allow effective extraction of pesticides. They can be modified (with ionic liquids, silanes or amines), coated with molecularly imprinted polymers or magnetized to improve the extraction of pesticides. Moreover, they can be altered to increase their sensitivity and stability. In addition to the analysis of pesticides by sophisticated techniques such as High Performance Liquid Chromatography or Gas chromatography, silica nanoparticles related simple detection methods are also proving to be effective. Electrochemical and optical detection based on enzymes (acetylcholinesterase and organophosphate hydrolase) or antibodies have been developed. Pesticide sensors dependent on fluorescence, chemiluminescence or Surface Enhanced Raman Spectroscopic responses are also SiNP based. Moreover, degradative enzymes (organophosphate hydrolases, carboxyesterases and laccases) and bacterial cells that produce recombinant enzymes have been immobilized on SiNPs for mediating pesticide degradation. After immobilization, these systems show increased stability and improved degradation. SiNP are significant in developing systems for effective extraction, detection and degradation of pesticides. SiNPs on account of their chemically inert nature and amenability to surface modifications makes them popular tools for fabricating devices for 'on-site' applications.

Electrochemical biosensors for rapid detection of Escherichia coli O157:H7

Electrochemical biosensors have shown great promise in the development of rapid methods for the detection of foodborne pathogens and have been intensively studied over the past two decades. The scope of this review is to summarize the advancements made in the development of electrochemical biosensors for the rapid detection of one of the most common foodborne pathogens, Escherichia coli O157:H7. The article is intended to include different configurations of electrochemical biosensors based on the sensing principles and measured electrical parameters, as well as the latest improvements of technology in the progress of electrochemical biosensor development to detect E. coli O157:H7. By discussing the current and future trend based on some of excellent published literatures and reviews, this survey is hoped to illustrate a broad and comprehensive understanding of electrochemical biosensors for the detection of foodborne pathogens.

CdTe quantum dots@luminol as signal amplification system for chrysoidine with chemiluminescence-chitosan/graphene oxide-magnetite-molecularly imprinting sensor

A sensitive chemiluminescence (CL) sensor based on chemiluminescence resonance energy transfer (CRET) in CdTe quantum dots@luminol (CdTe QDs@luminol) nanomaterials combined with chitosan/graphene oxide-magnetite-molecularly imprinted polymer (Cs/GM-MIP) for sensing chrysoidine was developed. CdTe QDs@luminol was designed to not only amplify the signal of CL but also reduce luminol consumption in the detection of chrysoidine. On the basis of the abundant hydroxy and amino, Cs and graphene oxide were introduced into the GM-MIP to improve the adsorption ability. The adsorption capacities of chrysoidine by both Cs/GM-MIP and non-imprinted polymer (Cs/GM-NIP) were investigated, and the CdTe QDs@luminol and Cs/GM-MIP were characterized by UV-vis, FTIR, SEM and TEM. The proposed sensor can detect chrysoidine within a linear range of 1.0×10(-7) - 1.0×10(-5) mol/L with a detection limit of 3.2×10(-8) mol/L (3δ) due to considerable chemiluminescence signal enhancement of the CdTe quantum dots@luminol detector and the high selectivity of the Cs/GM-MIP system. Under the optimal conditions of CL, the CdTe QDs@luminol-Cs/GM-MIP-CL sensor was used for chrysoidine determination in samples with satisfactory recoveries in the range of 90-107%.

Molecularly imprinted polymers for the analysis and removal of polychlorinated aromatic compounds in the environment: a review

Molecularly imprinted polymers selective to polychlorinated aromatic compounds for application in environmental studies.

Molecular imprinting: perspectives and applications

This critical review presents a survey of recent developments in technologies and strategies for the preparation of MIPs, followed by the application of MIPs in sample pretreatment, chromatographic separation and chemical sensing.

Well-defined nanostructured surface-imprinted polymers for the highly selective enrichment of low-abundance protein in mammalian cell extract

A new approach for the adsorption and enrichment of natural low-abundance protein by using nanostructured surface-imprinted polymers is presented.

Nanomaterials-Tools, Technology and Methodology of Nanotechnology Based Biomedical Systems for Diagnostics and Therapy

Nanomedicine helps to fight diseases at the cellular and molecular level by utilizing unique properties of quasi-atomic particles at a size scale ranging from 1 to 100 nm. Nanoparticles are used in therapeutic and diagnostic approaches, referred to as theranostics. The aim of this review is to illustrate the application of general principles of nanotechnology to select examples of life sciences, molecular medicine and bio-assays. Critical aspects relating to those examples are discussed.

Current trends in the development of molecularly imprinted polymers in CEC

This review focused on the developments in the field of molecularly imprinted polymers (MIPs) for CEC since 2009. New preparation techniques of MIP-based CEC, such as, portable microchip with macroporous monolithic imprinted microchannel, and low cross-linking MIPs based on liquid crystalline monomers, were discussed. Using selected cases rather than a comprehensive review of the entire field, our goal is to highlight the studies of the interest with an emphasis on recent work, and offers suggestions for future development in the field of imprinted materials for CEC separation.