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

Template bacteria-free fabrication of surface imprinted polymer-based biosensor for E. coli detection using photolithographic mimics: Hacking bacterial adhesion

As one class of molecular imprinted polymers (MIPs), surface imprinted polymer (SIP)-based biosensors show great potential in direct whole-bacteria detection. Micro-contact imprinting, that involves stamping the template bacteria immobilized on a substrate into a pre-polymerized polymer matrix, is the most straightforward and prominent method to obtain SIP-based biosensors. However, the major drawbacks of the method arise from the requirement for fresh template bacteria and often non-reproducible bacteria distribution on the stamp substrate. Herein, we developed a positive master stamp containing photolithographic mimics of the template bacteria (E. coli) enabling reproducible fabrication of biomimetic SIP-based biosensors without the need for the "real" bacteria cells. By using atomic force and scanning electron microscopy imaging techniques, respectively, the E. coli-capturing ability of the SIP samples was tested, and compared with non-imprinted polymer (NIP)-based samples and control SIP samples, in which the cavity geometry does not match with E. coli cells. It was revealed that the presence of the biomimetic E. coli imprints with a specifically designed geometry increases the sensor E. coli-capturing ability by an "imprinting factor" of about 3. These findings show the importance of geometry-guided physical recognition in bacterial detection using SIP-based biosensors. In addition, this imprinting strategy was employed to interdigitated electrodes and QCM (quartz crystal microbalance) chips. E. coli detection performance of the sensors was demonstrated with electrochemical impedance spectroscopy (EIS) and QCM measurements with dissipation monitoring technique (QCM-D).

Emerging Biomimetic Sensor Technologies for the Detection of Pathogenic Bacteria: A Commercial Viability Study

Ensuring a rapid and accurate identification of harmful bacteria is crucial in various fields including environmental monitoring, food safety, and clinical diagnostics. Conventional detection methods often suffer from limitations such as long analysis time, complexity, and the need for qualified personnel. Therefore, a lot of research effort is devoted to developing technologies with the potential to revolutionize the detection of pathogenic bacteria by offering rapid, sensitive, and user-friendly platforms for point-of-care analysis. In this light, biosensors have gained significant commercial attention in recent years due to their simplicity, portability, and rapid analysis capabilities. The purpose of this review is to identify a trend by analyzing which biosensor technologies have become commercially successful in the field of bacteria detection. Moreover, we highlight the characteristics that a biosensor must possess to finally arrive in the market and therefore in the hands of the end-user, and we present critical examples of the market applications of various technologies. The aim is to investigate the reason why certain technologies have achieved commercial success and extrapolate these trends to the future economic viability of a new subfield in the world of biosensing: the development of biomimetic sensor platforms. Therefore, an overview of recent advances in the field of biomimetic bacteria detection will be presented, after which the challenges that need to be addressed in the coming years to improve market penetration will be critically evaluated. We will zoom into the current shortcomings of biomimetic sensors based on imprinting technology and aptamers and try to come up with a recommendation for further development based on the trends observed from previous commercial success stories in biosensing.

Synthetic Genes For Dynamic Regulation Of DNA-Based Receptors

We present a strategy to control dynamically the loading and release of molecular ligands from synthetic nucleic acid receptors using in vitro transcription. We demonstrate this by engineering three model synthetic DNA-based receptors: a triplex-forming DNA complex, an ATP-binding aptamer, and a hairpin strand, whose ability to bind their specific ligands can be cotranscriptionally regulated (activated or inhibited) through specific RNA molecules produced by rationally designed synthetic genes. The kinetics of our DNA sensors and their genetically generated inputs can be captured using differential equation models, corroborating the predictability of the approach used. This approach shows that highly programmable nucleic acid receptors can be controlled with molecular instructions provided by dynamic transcriptional systems, illustrating their promise in the context of coupling DNA nanotechnology with biological signaling.

Nanopore surface engineering of molecular imprinted mesoporous organosilica for rapid and selective detection of L-thyroxine

To develop a biosensing platform for precise diagnosis and management of thyroid-related diseases, the sensitive and selective recognition and identification of L-thyroxine (T4), a thyroid hormone, remains challenging. We herein introduce T4-imprinted mesoporous organosilica (T4-IMO) for sensitive and specific detection of T4 via the sophisticated engineering of pore surfaces using additives with different polarities. The pore surface of T4-IMO emitting a stable fluorescence signal is simply modified by fixed additives. Additives embedded in the pore surface promote the rebinding response of T4 into the recognized cavities, subsequently sensitizing T4 detection. Notably, T4-IMO containing abundant fluorine elements on the pore surface shows a high affinity toward T4, remarkably boosting the rebinding capacity. In addition to good selectivity to T4, the "turn-off" fluorescent signal exhibits a linear relationship with the logarithm of T4 concentration in a range of 0-500 nM with a detection limit of 0.47 nM in synthetic urine samples. Our findings can establish an insightful strategy for the rational design of molecular-recognition-based sensor systems for the selective and sensitive detection of target analytes.

Electrochemically Synthesized MIP Sensors: Applications in Healthcare Diagnostics

Early-stage detection and diagnosis of diseases is essential to the prompt commencement of treatment regimens, curbing the spread of the disease, and improving human health. Thus, the accurate detection of disease biomarkers through the development of robust, sensitive, and selective diagnostic tools has remained cutting-edge scientific research for decades. Due to their merits of being selective, stable, simple, and having a low preparation cost, molecularly imprinted polymers (MIPs) are increasingly becoming artificial substitutes for natural receptors in the design of state-of-the-art sensing devices. While there are different MIP preparation approaches, electrochemical synthesis presents a unique and outstanding method for chemical sensing applications, allowing the direct formation of the polymer on the transducer as well as simplicity in tuning the film properties, thus accelerating the trend in the design of commercial MIP-based sensors. This review evaluates recent achievements in the applications of electrosynthesized MIP sensors for clinical analysis of disease biomarkers, identifying major trends and highlighting interesting perspectives on the realization of commercial MIP-endowed testing devices for rapid determination of prevailing diseases.

Imprinted Polymers on the Route to Plastibodies for Biomacromolecules (MIPs), Viruses (VIPs), and Cells (CIPs)

Around 30% of the scientific papers published on imprinted polymers describe the recognition of proteins, nucleic acids, viruses, and cells. The straightforward synthesis from only one up to six functional monomers and the simple integration into a sensor are significant advantages as compared with enzymes or antibodies. Furthermore, they can be synthesized against toxic substances and structures of low immunogenicity and allow multi-analyte measurements via multi-template synthesis. The affinity is sufficiently high for protein biomarkers, DNA, viruses, and cells. However, the cross-reactivity of highly abundant proteins is still a challenge.

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.

Bioanalytical sensors using the heat-transfer method HTM and related techniques

This review provides an overview on bio- and chemosensors based on a thermal transducer platform that monitors the thermal interface resistance R th between a solid chip and the supernatant liquid. The R th parameter responds in a surprisingly strong way to molecular-scale changes at the solid-liquid interface, which can be measured thermometrically, using for instance thermocouples in combination with a controllable heat source. In 2012, the effect was first observed during on-chip denaturation experiments on complementary and mismatched DNA duplexes that differ in their melting temperature. Since then, the concept is addressed as heat-transfer method, in short HTM, and numerous applications of the basic sensing principle were identified. Functionalizing the chip with bioreceptors such as molecularly imprinted polymers makes it possible to detect neurotransmitters, inflammation markers, viruses, and environmental pollutants. In combination with aptamer-type receptors, it is also possible to detect proteins at low concentrations. Changing the receptors to surface-imprinted polymers has opened up new possibilities for quantitative bacterial detection and identification in complex matrices. In receptor-free variants, HTM was successfully used to characterize lipid vesicles and eukaryotic cells (yeast strains, cancer cell lines), the latter showing spontaneous detachment under influence of the temperature gradient inherent to HTM. We will also address modifications to the original HTM technique such as M-HTM, inverted HTM, thermal wave transport analysis TWTA, and the hot-wire principle. The article concludes with an assessment of the possibilities and current limitations of the method, together with a technological forecast.

Molecularly Imprinted Polymers Using Yeast as a Supporting Substrate

Molecularly imprinted polymers (MIPs) have gained significant attention as artificial receptors due to their low cost, mild operating conditions, and excellent selectivity. To optimize the synthesis process and enhance the recognition performance, various support materials for molecular imprinting have been explored as a crucial research direction. Yeast, a biological material, offers advantages such as being green and environmentally friendly, low cost, and easy availability, making it a promising supporting substrate in the molecular imprinting process. We focus on the preparation of different types of MIPs involving yeast and elaborate on the specific roles it plays in each case. Additionally, we discuss the advantages and limitations of yeast in the preparation of MIPs and conclude with the challenges and future development trends of yeast in molecular imprinting research.

Imprinting of nanoparticles in thin films: Quo Vadis?

Nanomaterials, and especially nanoparticles, have been introduced to almost any aspect of our lives. This has caused increasing concern as to their toxicity and adverse effects on the environment and human health. The activity of nanoparticles, including their nanotoxicity, is not only a function of the material they are made of but also their size, shape, and surface properties. It is evident that there is an unmet need for simple approaches to the speciation of nanoparticles, namely to monitor and detect them based on their properties. An appealing method for such speciation involves the imprinting of nanoparticles in soft matrices. The principles of imprinting nanoparticles originate from the molecularly imprinted polymer (MIP) approach. This review summarizes the current status of this emerging field, which bridges between the traditional MIP approach and the imprinting of larger entities such as viruses and bacteria. The concepts of nanoparticle imprinting and the requirement of both physical and chemical matching between the nanoparticles and the matrix are discussed and demonstrated.

Electroactive molecularly imprinted polymer nanoparticles for selective glyphosate determination

Redox-active molecularly imprinted polymer nanoparticles selective for glyphosate, MIP-Gly NPs, were devised, synthesized, and subsequently integrated onto platinum screen-printed electrodes (Pt-SPEs) to fabricate a chemosensor for selective determination of glyphosate (Gly) without the need for redox probe in the test solution. That was because, ferrocenylmethyl methacrylate was added to the polymerization mixtures during the NPs synthesis so that the resulting MIP-Gly NPs contained covalently immobilized ferrocenyl moieties as the reporting redox ingredient, conferring these NPs with electroactive properties. MIP-Gly NPs of four different compositions were evaluated. The herein described approach represents a simple and effective way to endow MIP NPs with electrochemical reporting capabilities with neither the need to functionalize them post-synthesis nor to use electrochemical mediators present in the tested solution during the analyte determinations. MIP-Gly NPs synthesized using allylamine and squaramide-based monomers appeared most selective to Gly. The Pt-SPEs modified with MIP-Gly NPs were characterized with differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Changes in the DPV peak originating from the oxidation of the ferrocenyl moieties in these MIP-Gly NPs served as the analytical signal. The DPV limit of detection and the linear dynamic concentration range for Gly were 3.7 pM and 25 pM-500 pM, respectively. Moreover, the selectivity of the fabricated chemosensors was sufficiently high to determine Gly successfully in spiked river water samples.

Molecularly Imprinted Polymers as Synthetic Antibodies for Protein Recognition: The Next Generation

Molecularly imprinted polymers (MIPs) are chemical antibody mimics obtained by nanomoulding the 3D shape and chemical functionalities of a desired target in a synthetic polymer. Consequently, they possess exquisite molecular recognition cavities for binding the target molecule, often with specificity and affinity similar to those of antigen-antibody interactions. Research on MIPs targeting proteins began in the mid-90s, and this review will evaluate the progress made till now, starting from their synthesis in a monolith bulk format through surface imprinting to biocompatible soluble nanogels prepared by solid-phase synthesis. MIPs in the latter format will be discussed more in detail because of their tremendous potential of replacing antibodies in the biomedical domain like in diagnostics and therapeutics, where the workforce of antibodies is concentrated. Emphasis is also put on the development of epitope imprinting, which consists of imprinting a short surface-exposed fragment of a protein, resulting in MIPs capable of selectively recognizing the whole macromolecule, amidst others in complex biological media, on cells or tissues. Thus selecting the 'best' peptide antigen is crucial and in this context a rational approach, inspired from that used to predict peptide immunogens for peptide antibodies, is described for its unambiguous identification.

A Review on Bio- and Chemosensors for the Detection of Biogenic Amines in Food Safety Applications: The Status in 2022

This article provides an overview on the broad topic of biogenic amines (BAs) that are a persistent concern in the context of food quality and safety. They emerge mainly from the decomposition of amino acids in protein-rich food due to enzymes excreted by pathogenic bacteria that infect food under inappropriate storage conditions. While there are food authority regulations on the maximum allowed amounts of, e.g., histamine in fish, sensitive individuals can still suffer from medical conditions triggered by biogenic amines, and mass outbreaks of scombroid poisoning are reported regularly. We review first the classical techniques used for selective BA detection and quantification in analytical laboratories and focus then on sensor-based solutions aiming at on-site BA detection throughout the food chain. There are receptor-free chemosensors for BA detection and a vastly growing range of bio- and biomimetic sensors that employ receptors to enable selective molecular recognition. Regarding the receptors, we address enzymes, antibodies, molecularly imprinted polymers (MIPs), and aptamers as the most recent class of BA receptors. Furthermore, we address the underlying transducer technologies, including optical, electrochemical, mass-sensitive, and thermal-based sensing principles. The review concludes with an assessment on the persistent limitations of BA sensors, a technological forecast, and thoughts on short-term solutions.

Application of Molecularly Imprinted Electrochemical Biomimetic Sensors for Detecting Small Molecule Food Contaminants

Environmental chemical contaminants in food seriously impact human health and food safety. Successful detection methods can effectively monitor the potential risk of emerging chemical contaminants. Among them, molecularly imprinted polymers (MIPs) based on electrochemical biomimetic sensors overcome many drawbacks of conventional detection methods and offer opportunities to detect contaminants with simple equipment in an efficient, sensitive, and low-cost manner. We searched eligible papers through the Web of Science (2000-2022) and PubMed databases. Then, we introduced the sensing mechanism of MIPs, outlined the sample preparation methods, and summarized the MIP characterization and performance. The classification of electrochemistry, as well as its advantages and disadvantages, are also discussed. Furthermore, the representative application of MIP-based electrochemical biomimetic sensors for detecting small molecular chemical contaminants, such as antibiotics, pesticides, toxins, food additives, illegal additions, organic pollutants, and heavy metal ions in food, is demonstrated. Finally, the conclusions and future perspectives are summarized and discussed.

Advances, applications, and limitations of portable and rapid detection technologies for routinely encountered foodborne pathogens

Traditional foodborne pathogen detection methods are highly dependent on pre-treatment of samples and selective microbiological plating to reliably screen target microorganisms. Inherent limitations of conventional methods include longer turnaround time and high costs, use of bulky equipment, and the need for trained staff in centralized laboratory settings. Researchers have developed stable, reliable, sensitive, and selective, rapid foodborne pathogens detection assays to work around these limitations. Recent advances in rapid diagnostic technologies have shifted to on-site testing, which offers flexibility and ease-of-use, a significant improvement from traditional methods' rigid and cumbersome steps. This comprehensive review aims to thoroughly discuss the recent advances, applications, and limitations of portable and rapid biosensors for routinely encountered foodborne pathogens. It discusses the major differences between biosensing systems based on the molecular interactions of target analytes and biorecognition agents. Though detection limits and costs still need further improvement, reviewed technologies have high potential to assist the food industry in the on-site detection of biological hazards such as foodborne pathogens and toxins to maintain safe and healthy foods. Finally, this review offers targeted recommendations for future development and commercialization of diagnostic technologies specifically for emerging and re-emerging foodborne pathogens.

Overcoming Major Barriers to Developing Successful Sensors for Practical Applications Using Functional Nucleic Acids

For many years, numerous efforts have been focused on the development of sensitive, selective, and practical sensors for environmental monitoring, food safety, and medical diagnostic applications. However, the transition from innovative research to commercial success is relatively sparse. In this review, we identify four scientific barriers and one technical barrier to developing successful sensors for practical applications, including the lack of general methods to (a) generate receptors for a wide range of targets, (b) improve sensor selectivity to overcome interferences, (c) transduce the selective binding to different optical, electrochemical, and other signals, and (d) tune dynamic range to match thresholds of detection required for different targets; and the costly development of a new device. We then summarize solutions to overcome these barriers using sensors based on functional nucleic acids that include DNAzymes, aptamers, and aptazymes and how these sensors are coupled to widely available measurement devices to expand their capabilities and lower the barrier for their practical applications in the field and point-of-care settings.

Imprinted Polydimethylsiloxane-Graphene Oxide Composite Receptor for the Biomimetic Thermal Sensing of Escherichia coli

This work presents an imprinted polymer-based thermal biomimetic sensor for the detection of Escherichia coli. A novel and facile bacteria imprinting protocol for polydimethylsiloxane (PDMS) films was investigated, and these receptor layers were functionalized with graphene oxide (GO) in order to improve the overall sensitivity of the sensor. Upon the recognition and binding of the target to the densely imprinted polymers, a concentration-dependent measurable change in temperature was observed. The limit of detection attained for the sensor employing PDMS-GO imprints was 80 ± 10 CFU/mL, a full order lower than neat PDMS imprints (670 ± 140 CFU/mL), illustrating the beneficial effect of the dopant on the thermo-dynamical properties of the interfacial layer. A parallel benchmarking of the thermal sensor with a commercial impedance analyzer was performed in order to prove the possibility of using the developed PDMS-GO receptors with multiple readout platforms. Moreover, S. aureus, C. sakazakii and an additional E. coli strain were employed as analogue species for the assessment of the selectivity of the device. Finally, because of the potential that this biomimetic platform possesses as a low-cost, rapid, and on-site tool for monitoring E. coli contamination in food safety applications, spiked fruit juice was analyzed as a real sample. Reproducible and sensitive results fulfill the limit requirements of the applicable European microbiological regulation.

Raman Studies on Surface-Imprinted Polymers to Distinguish the Polymer Surface, Imprints, and Different Bacteria

Molecularly imprinted polymers (MIPs) are widely used as robust biomimetic recognition layers in sensing devices targeting a wide variety of analytes including microorganisms such as bacteria. Assessment of imprinting success and selectivity toward the target is of great importance in MIP quality control. We generated Escherichia coli-imprinted poly(styrene-co-DVB) as a model system for bacteria-imprinted polymers via surface imprinting using a glass stamp with covalently immobilized E. coli. Confocal Raman Microscopy was successfully employed to visualize bacteria, imprints, and polymer and to distinguish them from each other. The method has proven highly feasible for assessing if imprinting had been successful. In addition, we developed a method for selectivity investigation of bacteria MIPs based on combining Confocal Raman Microscopy and Partial Least Squares Discriminant Analysis (PLS-DA). The Raman spectra of E. coli and Bacillus cereus were acquired on E. coli-imprinted poly(styrene-co-DVB) and used to establish a PLS-DA model for differentiating between the bacteria species. Model validation demonstrated a correct classification of 95% of Raman spectra, indicating sufficient accuracy of the model for future use in MIP selectivity studies. Simultaneous differentiation of 3 bacteria species (E. coli, B. cereus, and Lactococcus lactis) on E. coli-imprinted poly(styrene-co-DVB) proved more difficult, which might be due to the limited depth resolution of the confocal Raman microscope resulting in the presence of interfering signals from the polymer substrate. It might be possible to overcome this obstacle by selective enhancement of the Raman signals originating from bacteria surfaces, such as tip enhanced Raman spectroscopy.

On the Effect of Soft Molecularly Imprinted Nanoparticles Receptors Combined to Nanoplasmonic Probes for Biomedical Applications

Soft, deformable, molecularly imprinted nanoparticles (nanoMIPs) were combined to nano-plasmonic sensor chips realized on poly (methyl methacrylate) (PMMA) substrates to develop highly sensitive bio/chemical sensors. NanoMIPs (d_mean < 50 nm), which are tailor-made nanoreceptors prepared by a template assisted synthesis, were made selective to bind Bovine Serum Albumin (BSA), and were herein used to functionalize gold optical nanostructures placed on a PMMA substrate, this latter acting as a slab waveguide. We compared nanoMIP-functionalized non-optimized gold nanogratings based on periodic nano-stripes to optimized nanogratings with a deposited ultra-thin MIP layer (<100 nm). The sensors performances were tested by the detection of BSA using the same setup, in which both chips were considered as slab waveguides, with the periodic nano-stripes allocated in a longitudinal orientation with respect to the direction of the input light. Result demonstrated the nanoMIP-non optimized nanogratings showed superior performance with respect to the ultra-thin MIP-optimized nanogratings. The peculiar deformable character of the nano-MIPs enabled to significantly enhance the limit of detection (LOD) of the plasmonic bio/sensor, allowing the detection of the low femtomolar concentration of analyte (LOD ∼ 3 fM), thus outpassing of four orders of magnitude the sensitivies achieved so far on optimized nano-patterned plasmonic platforms functionalized with ultra-thin MIP layers. Thus, deformable nanoMIPs onto non-optimized plasmonic probes permit to attain ultralow detections, down to the quasi-single molecule. As a general consideration, the combination of more plasmonic transducers to different kinds of MIP receptors is discussed as a mean to attain the detection range for the selected application field.

QCM-based assay designs for human serum albumin

Solid-phase synthesis is an elegant way to create molecularly imprinted polymer nanoparticles (nano-MIPs) comprising a single binding site, i.e. mimics of antibodies. When using human serum albumin (HSA) as the template, one achieves nano-MIPs with 53 ± 19 nm diameter, while non-imprinted polymer nanoparticles (nano-NIPs) reach 191 ± 96 nm. Fluorescence assays lead to Stern-Volmer plots revealing selective binding to HSA with selectivity factors of 1.2 compared to bovine serum albumin (BSA), 1.9 for lysozyme, and 4.1 for pepsin. Direct quartz crystal microbalance (QCM) assays confirm these results: nano-MIPs bind to HSA immobilized on QCM surfaces. This opens the way for competitive QCM-based assays for HSA: adding HSA to nanoparticle solutions indeed reduces binding to the QCM surfaces in a concentration-dependent manner. They achieve a limit of detection (LoD) of 80 nM and a limit of quantification (LoQ) of 244 nM. Furthermore, the assay shows recovery rates around 100% for HSA even in the presence of competing analytes.

Molecularly Imprinted Polymer Hydrogel Nanoparticles: Synthetic Antibodies for Cancer Diagnosis and Therapy

Cancer is a leading cause of death worldwide and according to the World Health Organization (WHO) accounted for 10 million deaths in 2020. Promising theranostic (therapy and diagnostic) agents in the treatment of cancer are nanomaterials, which have come to the forefront because of their small size approaching those of protein complexes in the human body, and of their easy functionalization giving access to nanocomposite materials with diverse functions (fluorescence, magnetic, stimuli-responsiveness, etc.), and improved biocompatibility. Among them, affinity nanoparticles, often decorated with highly specific targeting ligands such as antibodies, aptamers, lectins and peptides, have enabled enhanced binding and exquisite recognition of biomarkers overexpressed in cancer cells. In this review, we describe an emerging class of targeting ligands, molecularly imprinted polymer hydrogel nanoparticles for their application in the early detection of disease, with the aim to improve diagnosis and treatment.

Fighting Antibiotic-Resistant Bacteria : Promising Strategies Orchestrated by Molecularly Imprinted Polymers

Infections caused by antibiotic-resistant bacteria are difficult and sometimes impossible to treat, making them one of the major public health problems of our time. We highlight how one unique material , molecularly imprinted polymers (MIPs), can orchestrate several strategies to fight this major societal issue. MIPs are tailor-made biomimetic supramolecular receptors that recognize and bind target molecules with a high affinity and selectivity, comparable to those of antibodies. While research on MIPs for combatting cancer has been constantly flourishing, comprehensive work on their involvement in combatting resistant superbugs has been rather scarce. This review aims at filling this gap. We will describe what are the causes of bacterial resistance and at which level MIPs can deploy their weapons. MIPs' targets can be biofilm constituents, quorum sensing messengers, bacterial surface proteins and antibiotic-deactivating enzymes, among others. We will conclude on the current challenges and future developments in this field.

Biomimetic Sensors to Detect Bioanalytes in Real-Life Samples Using Molecularly Imprinted Polymers: A Review

Molecularly imprinted polymers (MIPs) come with the promise to be highly versatile, useful artificial receptors for sensing a wide variety of analytes. Despite a very large body of literature on imprinting, the number of papers addressing real-life biological samples and analytes is somewhat limited. Furthermore, the topic of MIP-based sensor design is still, rather, in the research stage and lacks wide-spread commercialization. This review summarizes recent advances of MIP-based sensors targeting biological species. It covers systems that are potentially interesting in medical applications/diagnostics, in detecting illicit substances, environmental analysis, and in the quality control of food. The main emphasis is placed on work that demonstrates application in real-life matrices, including those that are diluted in a reasonable manner. Hence, it does not restrict itself to the transducer type, but focusses on both materials and analytical tasks.

Molecularly imprinted polymers in toxicology: a literature survey for the last 5 years

The science of toxicology dates back almost to the beginning of human history. Toxic chemicals, which are encountered in different forms, are always among the chemicals that should be investigated in criminal field, environmental application, pharmaceutic, and even industry, where many researches have been carried out studies for years. Almost all of not only drugs but also industrial dyes have toxic side and direct effects. Environmental micropollutants accumulate in the tissues of all living things, especially plants, and show short- or long-term toxic symptoms. Chemicals in forensic science can be known by detecting the effect they cause to the body with the similar mechanism. It is clear that the best tracking tool among analysis methods is molecularly printed polymer-based analytical setups. Different polymeric combinations of molecularly imprinted polymers allow further study on detection or extraction using chromatographic and spectroscopic instruments. In particular, methods used in forensic medicine can detect trace amounts of poison or biological residues on the scene. Molecularly imprinted polymers are still in their infancy and have many variables that need to be developed. In this review, we summarized how molecular imprinted polymers and toxicology intersect and what has been done about molecular imprinted polymers in toxicology by looking at the studies conducted in the last 5 years.

Enhancing sensitivity of QCM for dengue type 1 virus detection using graphene-based polymer composites

Graphene oxide-molecularly imprinted polymer composites (GO-MIP) have attracted significant attention as recognition materials in sensing due to their outstanding properties in terms of electrical and thermal conductivity, high mechanical modulus, and the comparably straightforward way to functionalize them. The aim of this study was to design a MIP-based sensor recognition material and enhance its sensitivity by blending it with GO for sensing a harmful dengue hemorrhagic fever pathogen, namely the dengue type 1 virus (DENV-1). Polymer composites comprising GO incorporated to an acrylamide (AAM)/methacrylic acid (MAA)/methyl methacrylate (MMA)/N-vinylpyrrolidone (VP) copolymer were synthesized and compared to the “pure” MIP, i.e., the copolymer without GO. The pure polymer revealed a zeta potential of + 9.9 ± 0.5 mV, whereas GO sheets prepared have a zeta potential of − 60.3 ± 2.7 mV. This results in an overall zeta potential of − 11.2 ± 0.2 mV of the composite. Such polymer composites seem appropriate to bind the positively charged DENV-1 particle (+ 42.2 ± 2.8 mV). GO-MIP coated onto 10-MHz quartz crystal microbalance (QCM) sensors indeed revealed two times sensitivity compared to sensors based on the pure MIP. Furthermore, GO-polymer composites revealed imprinting factors of up to 21, compared to 3 of the pure MIP. When plotting the sensor characteristic in a semilogarithmic way, the composite sensor shows the linear response to DENV-1 in the concentration range from 10⁰ to 10³ pfu mL⁻¹. The corresponding limits of detection (S/N = 3) and quantification (S/N = 10) are 0.58 and 1.94 pfu mL⁻¹, respectively. Furthermore, imprinted polymer composites selectively bind DENV-1 without significant interference: DENV-2, DENV-3, DENV-4, respectively, yield 13–16% of DENV-1 signal. The sensor requires only about 15–20 min to obtain a result.

Regenerable ZnO/GaAs Bulk Acoustic Wave Biosensor for Detection of Escherichia coli in "Complex" Biological Medium

A regenerable bulk acoustic wave (BAW) biosensor is developed for the rapid, label-free and selective detection of Escherichia coli in liquid media. The geometry of the biosensor consists of a GaAs membrane coated with a thin film of piezoelectric ZnO on its top surface. A pair of electrodes deposited on the ZnO film allows the generation of BAWs by lateral field excitation. The back surface of the membrane is functionalized with alkanethiol self-assembled monolayers and antibodies against E. coli. The antibody immobilization was investigated as a function of the concentration of antibody suspensions, their pH and incubation time, designed to optimize the immunocapture of bacteria. The performance of the biosensor was evaluated by detection tests in different environments for bacterial suspensions ranging between 10³ and 10⁸ CFU/mL. A linear dependence between the frequency response and the logarithm of E. coli concentration was observed for suspensions ranging between 10³ and 10⁷ CFU/mL, with the limit of detection of the biosensor estimated at 10³ CFU/mL. The 5-fold regeneration and excellent selectivity towards E. coli detected at 10⁴ CFU/mL in a suspension tinted with Bacillus subtilis at 10⁶ CFU/mL illustrate the biosensor potential for the attractive operation in complex biological media.

An Overview of Bio-Inspired Intelligent Imprinted Polymers for Virus Determination

The molecular imprinting polymers (MIPs) have shown their potential in various applications including pharmaceuticals, chemical sensing and biosensing, medical diagnosis, and environmental related issues, owing to their artificial selective biomimetic recognition ability. Despite the challenges posed in the imprinting and recognition of biomacromolecules, the use of MIP for the imprinting of large biomolecular oragnism such as viruses is of huge interest because of the necessity of early diagnosis of virus-induced diseases for clinical and point-of-care (POC) purposes. Thus, many fascinating works have been documented in which such synthetic systems undoubtedly explore a variety of potential implementations, from virus elimination, purification, and diagnosis to virus and bacteria-borne disease therapy. This study is focused comprehensively on the fabrication strategies and their usage in many virus-imprinted works that have appeared in the literature. The drawbacks, challenges, and perspectives are also highlighted.

From Diagnosis to Treatment: Recent Advances in Patient-Friendly Biosensors and Implantable Devices

Patient-friendly medical diagnostics and treatments have been receiving a great deal of interest due to their rapid and cost-effective health care applications with minimized risk of infection, which has the potential to replace conventional hospital-based medical procedures. In particular, the integration of recently developed materials into health care devices allows the rapid development of point-of-care (POC) sensing platforms and implantable devices with special functionalities. In this review, the recent advances in biosensors for patient-friendly diagnosis and implantable devices for patient-friendly treatment are discussed. Comprehensive analysis of portable and wearable biosensing platforms for patient-friendly health monitoring and disease diagnosis is provided, including topics such as materials selection, device structure and integration, and biomarker detection strategies. Moreover, specific challenges related to each biological fluid for wearable biosensor-based POC applications are presented. Also, advances in implantable devices, including recent materials development and wireless communication strategies, are discussed. Furthermore, various patient-friendly surgical and treatment approaches are reviewed, such as minimally invasive insertion and mounting, in vivo electrical and optical modulations, and post-operation health monitoring. Finally, the challenges and future perspectives toward the development of the patient-friendly diagnosis and treatment are provided.

Imprinted Polymers as Synthetic Receptors in Sensors for Food Safety

Foodborne illnesses represent high costs worldwide in terms of medical care and productivity. To ensure safety along the food chain, technologies that help to monitor and improve food preservation have emerged in a multidisciplinary context. These technologies focus on the detection and/or removal of either biological (e.g., bacteria, virus, etc.) or chemical (e.g., drugs and pesticides) safety hazards. Imprinted polymers are synthetic receptors able of recognizing both chemical and biological contaminants. While numerous reviews have focused on the use of these robust materials in extraction and separation applications, little bibliography summarizes the research that has been performed on their coupling to sensing platforms for food safety. The aim of this work is therefore to fill this gap and highlight the multidisciplinary aspects involved in the application of imprinting technology in the whole value chain ranging from IP preparation to integrated sensor systems for the specific recognition and quantification of chemical and microbiological contaminants in food samples.

Molecular imprinting technology for sensing foodborne pathogenic bacteria

Foodborne diseases caused by bacterial pathogens pose a widespread and growing threat to public health in the world. Rapid detection of pathogenic bacteria is of great importance to prevent foodborne diseases and ensure food safety. However, traditional detection methods are time-consuming, labour intensive and expensive. In recent years, many attempts have been made to develop alternative methods for bacterial detection. Biosensors integrated with molecular imprinted polymers (MIPs) and various transducer platforms are among the most promising candidates for the detection of pathogenic bacteria in a highly sensitive, selective and ultra-rapid manner. In this review, we summarize the most recent advances in molecular imprinting for bacterial detection, introduce the underlying recognition mechanisms and highlight the applications of MIP-based biosensors. In addition, the challenges and future perspectives are discussed with the aim of accelerating the development of MIP-based biosensors and extending their applications.

Acoustic radiation-free surface phononic crystal resonator for in-liquid low-noise gravimetric detection

Acoustic wave resonators are promising candidates for gravimetric biosensing. However, they generally suffer from strong acoustic radiation in liquid, which limits their quality factor and increases their frequency noise. This article presents an acoustic radiation-free gravimetric biosensor based on a locally resonant surface phononic crystal (SPC) consisting of periodic high aspect ratio electrodes to address the above issue. The acoustic wave generated in the SPC is slower than the sound wave in water, hence it prevents acoustic propagation in the fluid and results in energy confinement near the electrode surface. This energy confinement results in a significant quality factor improvement and reduces frequency noise. The proposed SPC resonator is numerically studied by finite element analysis and experimentally implemented by an electroplating-based fabrication process. Experimental results show that the SPC resonator exhibits an in-liquid quality factor 15 times higher than a conventional Rayleigh wave resonator at a similar operating frequency. The proposed radiation suppression method using SPC can also be applied in other types of acoustic wave resonators. Thus, this method can serve as a general technique for boosting the in-liquid quality factor and sensing performance of many acoustic biosensors.

Generation of High-Affinity Molecularly Imprinted Nanoparticles for Protein Recognition via a Solid-Phase Synthesis Protocol

Molecularly imprinted polymers are leading technology in the development of protein biomimetics. This chapter describes the protocol for the synthesis of protein imprinted nanoparticles. These materials exhibit exceptional affinity (into the nM/pM range) and selectivity for their target template. The nanoparticles can be developed for a wide range of targets, while exhibiting excellent robustness, solubility, and flexibility in use. They are finding use in the creation of drug delivery vectors and sensing and recognition assays.

Selective capturing and fluorescence “turn on” detection of dibutyl phthalate using a molecular imprinted nanocomposite

Fluorescence-based selective detection of dibutyl phthalate is achieved via a paper-strip-based approach.

MIPs for commercial application in low-cost sensors and assays - An overview of the current status quo

Molecularly imprinted polymers (MIPs) have emerged over the past few decades as interesting synthetic alternatives due to their long-term chemical and physical stability and low-cost synthesis procedure. They have been integrated into many sensing platforms and assay formats for the detection of various targets, ranging from small molecules to macromolecular entities such as pathogens and whole cells. Despite the advantages MIPs have over natural receptors in terms of commercialization, the striking success stories of biosensor applications such as the glucose meter or the self-test for pregnancy have not been matched by MIP-based sensor or detection kits yet. In this review, we zoom in on the commercial potential of MIP technology and aim to summarize the latest developments in their commercialization and integration into sensors and assays with high commercial potential. We will also analyze which bottlenecks are inflicting with commercialization and how recent advances in commercial MIP synthesis could overcome these obstacles in order for MIPs to truly achieve their commercial potential in the near future.

Fluorescent probe sensor based on (R)-(-)-4-phenyl-2-oxazolidone for effective detection of divalent cations

Significant progress attained in sensor science in recent years has resulted in the development of highly efficient fluorescence probes for sensing metal ions. Fluorescent molecular probes based on (R)-(-)-4-phenyl-2-oxazolidone are reported here. Fluorescence studies indicated that the molecular probe could be used successfully to sense divalent metal cations such as Cu²⁺ , Co²⁺ , Pb²⁺ , and Zn²⁺ . The addition of divalent metal cations to the molecular probe produced a specific interaction pattern under UV-visible and fluorescence spectroscopy. These molecules could detect metal cations using fluorescence quenching. Stern-Volmer plots were used to determine quenching rate coefficients, which were calculated to be 2 × 10¹ , 1.06 × 10³ and 7.39 × 10² M^-1 s^-1 for copper, cobalt, and zinc respectively. Calculation of limit of detection for heavy metal cations revealed that the reported molecular probes improved the limit of detection compared with available standard data. Limit of quantitation values were also well within the permissible range. The frontier energy gap of highest occupied molecular orbital to the lowest unoccupied molecular orbital was evaluated using the density functional theory approach and Gaussian 09 W software, which complemented the coordination of azetidinones with divalent metal ions.

Long-period grating fiber-optic sensors exploiting molecularly imprinted TiO2 nanothin films with photocatalytic self-cleaning ability

Highly sensitive and selective long-period grating (LPG) fiber-optic sensors modified with molecularly imprinted TiO₂ nanothin films were fabricated. The films were deposited onto the surface of the optical fiber via liquid-phase deposition (LPD), using tetrakis(N-methylpyridinium-4-yl)porphyrin (TMPyP) as a template. Three LPG resonance bands were monitored during film deposition, which was of duration 4.5 h. Prior to template removal, heat treatment at 60 °C under high-humidity conditions led to an increase in refractive index of the TiO₂ film, evidenced by changes in the central wavelengths of the attenuation bands. After template removal using HCl solution (0.01 M), the TMPyP-imprinted film-modified LPG sensor showed higher sensitivity to the template molecule than to structurally related guest molecules. This was measured at the 1st and 2nd resonance bands, with wavelengths ranging from 690 to 738 nm and 815 to 905 nm, respectively. No selective binding of the template was observed with a non-imprinted TiO₂ film prepared in the same manner. Furthermore, the heat-treated imprinted films exhibited a substantial enhancement of photocatalytic activity for template irradiation. In particular, the self-cleaning property of the imprinted film-modified LPG sensor under ultraviolet irradiation led to highly efficient and selective binding to the template. The mechanism of the interaction between the template and the TiO₂ matrix was investigated by UV-vis and Fourier-transform infrared (FTIR) spectroscopies. Additionally, morphological studies using scanning electron microscopy (SEM) were conducted. Graphical abstract.

Effect of surface functionality of molecularly imprinted composite nanospheres on specific recognition of proteins

The surface functionality of biomaterial plays a primary role in determining its application in biorecognition and drug delivery. In our work, three types of synthetic tailoring polymer nanospheres with hierarchical architecture were constructed to obtain functional polymer layer with disparate chemical motifs for protein adsorption via surface imprinting and grafting copolymerization. In this polymerization system, the structure stability of template protein bovine serum albumin (BSA) is well maintained within a certain range, which facilitated the accurate imprinting and precise identification. A comprehensive protocol for screening different functional layer is proposed through comparing the adsorption behavior, selectivity, identification and responsiveness to medium pH of three functional layers. Our study demonstrates that surface functionality greatly influences the adsorption capacity and selectivity of adsorption material. The functional layer with ionic liquid structure that could only provide multiple non-covalent binding sites is beneficial to the proteins aggregation and extraction, while the anti-nonspecific binding functional layer of biomaterial with zwitterionic structure for specific protein capture is promising to serve as a preferable antigen-antibody communication network, which shows great potential for protein recognition and separation. In summary, our proposed strategy provides a systematic selection criterion of biomaterials for effective application in biosensors.

Bioimprint Mediated Label-Free Isolation of Pancreatic Tumor Cells from a Healthy Peripheral Blood Cell Population

New techniques are required for earlier diagnosis and response to treatment of pancreatic cancer. Here, a label-free approach is reported in which circulating pancreatic tumor cells are isolated from healthy peripheral blood cells via cell bioimprinting technology. The method involves pre-fabrication of pancreatic cell layers and sequential casting of cell surfaces with a series of custom-made resins to produce negative cell imprints. The imprint is functionalized with a combination of polymers to engineer weak attraction to the cells which is further amplified by the increased area of contact with the matching cells. A flow-through bioimprint chip is designed and tested for selectivity toward two pancreatic tumor cell lines, ASPC-1 and Mia-PaCa-2. Healthy human peripheral blood mononuclear cells (PBMCs) are spiked with pancreatic tumor cells at various concentrations. Bioimprints are designed for preferential retention of the matching pancreatic tumor cells and with respect to PBMCs. Tumor bioimprints are capable of capturing and concentrating pancreatic tumor cells from a mixed cell population with increased retention observed with the number of seedings. ASPC-1 bioimprints preferentially retain both types of pancreatic tumor cells. This technology could be relevant for the collection and interrogation of liquid biopsies, early detection, and relapse monitoring of pancreatic cancer patients.

Sensing the classical swine fever virus with molecularly imprinted polymer on quartz crystal microbalance

Classical swine fever (CSF) is a highly contagious and fatal viral disease in pigs caused by the virus of the same name (classical swine fever virus – CSFV). Economical reasons dictate the need for rapid early detection of this pathogen. Herein we report on a sensor for CSFV detection based on a quartz crystal microbalance (QCM) making use of molecularly imprinted polymer (MIP) as the receptor. It relies on a copolymer comprising acrylamide (AAM), methacrylic acid (MAA), methyl methacrylate (MMA), and n-vinylpyrrolidone (VP). SEM images of CSFV MIP reveal cavities on the polymer surface with an average diameter of d = 59 nm, which correlates well with the dimensions of CSFV particles. QCM sensor measurements yield concentration-dependent CSFV sensor responses resulting in LOD = 1.7 μg/mL, LOQ = 5.1 μg/mL and R² = 0.9963. Furthermore, CSFV-MIP sensors selectively bind CSFV with selectivity factors of 2 over porcine respiratory and reproductive virus (PRRSV) and 62 over pseudorabies virus (PRV), respectively. Finally, sensor responses turned out fully reversible.

Molecularly Imprinted Polymers and Surface Imprinted Polymers Based Electrochemical Biosensor for Infectious Diseases

Owing to their merits of simple, fast, sensitive, and low cost, electrochemical biosensors have been widely used for the diagnosis of infectious diseases. As a critical element, the receptor determines the selectivity, stability, and accuracy of the electrochemical biosensors. Molecularly imprinted polymers (MIPs) and surface imprinted polymers (SIPs) have great potential to be robust artificial receptors. Therefore, extensive studies have been reported to develop MIPs/SIPs for the detection of infectious diseases with high selectivity and reliability. In this review, we discuss mechanisms of recognition events between imprinted polymers with different biomarkers, such as signaling molecules, microbial toxins, viruses, and bacterial and fungal cells. Then, various preparation methods of MIPs/SIPs for electrochemical biosensors are summarized. Especially, the methods of electropolymerization and micro-contact imprinting are emphasized. Furthermore, applications of MIPs/SIPs based electrochemical biosensors for infectious disease detection are highlighted. At last, challenges and perspectives are discussed.