Electrosynthesis and binding properties of molecularly imprinted poly-o-phenylenediamine for selective recognition and direct electrochemical detection of myoglobin

Molecular imprinting technology for biomedical applications

Molecularly imprinted polymers (MIPs), a type of biomimetic material, have attracted considerable interest owing to their cost-effectiveness, good physiochemical stability, favourable specificity and selectivity for target analytes, and widely used for various biological applications. It was demonstrated that MIPs with significant selectivity towards protein-based targets could be applied in medicine, diagnostics, proteomics, environmental analysis, sensors, various in vivo and/or in vitro applications, drug delivery systems, etc. This review provides an overview of MIPs dedicated to biomedical applications and insights into perspectives on the application of MIPs in newly emerging areas of biotechnology. Many different protocols applied for the synthesis of MIPs are overviewed in this review. The templates used for molecular imprinting vary from the minor glycosylated glycan-based structures, amino acids, and proteins to whole bacteria, which are also overviewed in this review. Economic, environmental, rapid preparation, stability, and reproducibility have been highlighted as significant advantages of MIPs. Particularly, some specialized MIPs, in addition to molecular recognition properties, can have high catalytic activity, which in some cases could be compared with other bio-catalytic systems. Therefore, such MIPs belong to the class of so-called 'artificial enzymes'. The discussion provided in this manuscript furnishes a comparative analysis of different approaches developed, underlining their relative advantages and disadvantages highlighting trends and possible future directions of MIP technology.

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.

Electrochemical biosensing based comparative study of monoclonal antibodies against SARS-CoV-2 nucleocapsid protein

In this study, we are reporting an electrochemical biosensor for the determination of three different clones of monoclonal antibodies (mAbs) against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) recombinant nucleocapsid protein (rN). The nucleocapsid protein was chosen as a system component identifying and discriminating antibodies that occur after virus infection instead of S protein used in serological tests to measure antibodies raised after vaccination and infection. The sensing platform was based on a screen-printed carbon electrode (SPCE) covered with gold nanoparticles (AuNP) and subsequently modified with a self-assembled monolayer (SAM) to ensure the covalent immobilization of the rN. The interaction between the protein and three clones of mAbs against SARS-CoV-2 rN with clone numbers 4G6, 7F10, and 1A6, were electrochemically registered in the range of concentrations. Three techniques, cyclic voltammetry (CV), differential pulse voltammetry (DPV), and pulse amperometric detection (PAD) were used for the detection. A gradual change in the responses with an increase in mAbs concentration for all techniques was observed. To assess the performance of the developed electrochemical biosensor, 'complexation constant' (KC), limit of detection (LOD), and limit of quantification (LOQ) were calculated for all assessed clones of mAbs and all used techniques. Our results indicated that DPV possessing higher fitting accuracy illustrated more significant differences in KC constants and LOD/LOQ values. According to the DPV results, 7F10 clone was characterized with the highest KC value of 1.47 ± 0.07 μg/mL while the lowest LOD and LOQ values belonged to the 4G6 clone and equaled 0.08 ± 0.01 and 0.25 ± 0.01 μg/mL, respectively. Overall, these results demonstrate the potential of electrochemical techniques for the detection and distinguishing of different clones of mAbs against SARS-CoV-2 nucleocapsid protein.

Protein-imprinted polymers: How far have "plastic antibodies" come?

Antibodies are highly selective and sensitive, making them the gold standard for recognition affinity tools. However, their production cost is high and their downstream processing is time-consuming. Molecularly imprinted polymers (MIPs) are tailor-made by incorporating specific molecular recognition sites in their structure, thus translating into receptor-like activity mode of action. The interest in molecular imprinting technology, applied to biomacromolecules, has increased in the past decade. MIPs, produced using biomolecules as templates, commonly referred to as "plastic antibodies" or "artificial receptors", have been considered as suitable cheaper and easy to produce alternatives to antibodies. Research on MIPs, designed to recognize proteins or peptides is particularly important, with potential contributions towards biomedical applications, namely biosensors and targeted drug delivery systems. This mini review will cover recent advances on (bio)molecular imprinting technology, where proteins or peptides are targeted or mimicked for sensing and therapeutic applications. Polymerization methods are reviewed elsewhere, being out of the scope of this review. Template selection and immobilization approaches, monomers and applications will be discussed, highlighting possible drawbacks and gaps in research.

Molecularly Imprinted Polymer-Based Sensors for the Detection of Skeletal- and Cardiac-Muscle-Related Analytes

Molecularly imprinted polymers (MIPs) are synthetic polymers with specific binding sites that present high affinity and spatial and chemical complementarities to a targeted analyte. They mimic the molecular recognition seen naturally in the antibody/antigen complementarity. Because of their specificity, MIPs can be included in sensors as a recognition element coupled to a transducer part that converts the interaction of MIP/analyte into a quantifiable signal. Such sensors have important applications in the biomedical field in diagnosis and drug discovery, and are a necessary complement of tissue engineering for analyzing the functionalities of the engineered tissues. Therefore, in this review, we provide an overview of MIP sensors that have been used for the detection of skeletal- and cardiac-muscle-related analytes. We organized this review by targeted analytes in alphabetical order. Thus, after an introduction to the fabrication of MIPs, we highlight different types of MIP sensors with an emphasis on recent works and show their great diversity, their fabrication, their linear range for a given analyte, their limit of detection (LOD), specificity, and reproducibility. We conclude the review with future developments and perspectives.

Evaluation of the interaction between SARS-CoV-2 spike glycoproteins and the molecularly imprinted polypyrrole

The SARS-CoV-2 spike glycoprotein (SARS-CoV-2-S) was used as a template molecule and polypyrrole (Ppy) was applied as an electro-generated conducting polymer, which was acting as a matrix for the formation of molecular imprints. Two types of Ppy-layers: molecularly imprinted polypyrrole (MIP-Ppy) and non-imprinted polypyrrole (NIP-Ppy) were electrochemically deposited on the working platinum electrode. The performance of electrodes modified by MIP-Ppy and NIP-Ppy layers was evaluated by pulsed amperometric detection (PAD). During the assessment of measurement results registered by PAD, the integrated Cottrell equation (Anson plot) was used to calculate the amount of charge passed through the MIP-Ppy and NIP-Ppy layers. The interaction between SARS-CoV-2 spike glycoproteins and molecularly imprinted polypyrrole (MIP-Ppy) was assessed by the Anson plot based calculations. This assessment reveals that SARS-CoV-2-S glycoproteins are interacting with MIP-Ppy more strongly than with NIP-Ppy.

Fabrication and Characterization of Acute Myocardial Infarction Myoglobin Biomarker Based on Chromium-Doped Zinc Oxide Nanoparticles

In this article, we describe the fabrication and characterization of a sensor for acute myocardial infarction that detects myoglobin biomarkers using chromium (Cr)-doped zinc oxide (ZnO) nanoparticles (NPs). Pure and Cr-doped ZnO NPs (13 × 10¹⁷, 20 × 10¹⁷, and 32 × 10¹⁷ atoms/cm³ in the solid phase) were synthesized by a facile low-temperature sol-gel method. Synthesized NPs were examined for structure and morphological analysis using various techniques to confirm the successful formation of ZnO NPs. Zeta potential was measured in LB media at a negative value and increased with doping. XPS spectra confirmed the presence of oxygen deficiency in the synthesized material. To fabricate the sensor, synthesized NPs were screen-printed over a pre-fabricated gold-coated working electrode for electrochemical detection of myoglobin (Mb). Cr-doped ZnO NPs doped with 13 × 10¹⁷ Cr atomic/cm³ revealed the highest sensitivity of ~37.97 μA.cm⁻²nM⁻¹ and limit of detection (LOD) of 0.15 nM for Mb with a response time of ≤10 ms. The interference study was carried out with cytochrome c (Cyt-c) due to its resemblance with Mb and human serum albumin (HSA) abundance in the blood and displayed distinct oxidation potential and current values for Mb. Cr-doped ZnO NP-based Mb biosensors showed 3 times higher sensitivity as compared to pure ZnO NP-based sensors.

Development of molecularly imprinted polymer based phase boundaries for sensors design (review)

Achievements in polymer chemistry enables to design artificial phase boundaries modified by imprints of selected molecules and some larger structures. These structures seem very useful for the design of new materials suitable for affinity chromatography and sensors. In this review, we are overviewing the synthesis of molecularly imprinted polymers (MIPs) and the applicability of these MIPs in the design of affinity sensors. Such MIP-based layers or particles can be used as analyte-recognizing parts for sensors and in some cases they can replace very expensive compounds (e.g.: antibodies, receptors etc.), which are recognizing analyte. Many different polymers can be used for the formation of MIPs, but conducing polymers shows the most attractive capabilities for molecular-imprinting by various chemical compounds. Therefore, the application of conducting polymers (e.g.: polypyrrole, polyaniline, polythiophene, poly(3,4-ethylenedioxythiophene), and ortho-phenylenediamine) seems very promising. Polypyrrole is one of the most suitable for the development of MIP-based structures with molecular imprints by analytes of various molecular weights. Overoxiation of polypyrrole enables to increase the selectivity of polypyrrole-based MIPs. Methods used for the synthesis of conducting polymer based MIPs are overviewed. Some methods, which are applied for the transduction of analytical signal, are discussed, and challenges and new trends in MIP-technology are foreseen.

Molecularly Imprinted Polymer-Based Sensors for SARS-CoV-2: Where Are We Now?

Since the first reported case of COVID-19 in 2019 in China and the official declaration from the World Health Organization in March 2021 as a pandemic, fast and accurate diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has played a major role worldwide. For this reason, various methods have been developed, comprising reverse transcriptase-polymerase chain reaction (RT-PCR), immunoassays, clustered regularly interspaced short palindromic repeats (CRISPR), reverse transcription loop-mediated isothermal amplification (RT-LAMP), and bio(mimetic)sensors. Among the developed methods, RT-PCR is so far the gold standard. Herein, we give an overview of the MIP-based sensors utilized since the beginning of the pandemic.

Electroanalytical point-of-care detection of gold standard and emerging cardiac biomarkers for stratification and monitoring in intensive care medicine - a review

Determination of specific cardiac biomarkers (CBs) during the diagnosis and management of adverse cardiovascular events such as acute myocardial infarction (AMI) has become commonplace in emergency department (ED), cardiology and many other ward settings. Cardiac troponins (cTnT and cTnI) and natriuretic peptides (BNP and NT-pro-BNP) are the preferred biomarkers in clinical practice for the diagnostic workup of AMI, acute coronary syndrome (ACS) and other types of myocardial ischaemia and heart failure (HF), while the roles and possible clinical applications of several other potential biomarkers continue to be evaluated and are the subject of several comprehensive reviews. The requirement for rapid, repeated testing of a small number of CBs in ED and cardiology patients has led to the development of point-of-care (PoC) technology to circumvent the need for remote and lengthy testing procedures in the hospital pathology laboratories. Electroanalytical sensing platforms have the potential to meet these requirements. This review aims firstly to reflect on the potential benefits of rapid CB testing in critically ill patients, a very distinct cohort of patients with deranged baseline levels of CBs. We summarise their source and clinical relevance and are the first to report the required analytical ranges for such technology to be of value in this patient cohort. Secondly, we review the current electrochemical approaches, including its sub-variants such as photoelectrochemical and electrochemiluminescence, for the determination  of important CBs highlighting the various strategies used, namely the use of micro- and nanomaterials, to maximise the sensitivities and selectivities of such approaches. Finally, we consider the challenges that must be overcome to allow for the commercialisation of this technology and transition into intensive care medicine.

Recent Advances of Point-of-Care Devices Integrated with Molecularly Imprinted Polymers-Based Biosensors: From Biomolecule Sensing Design to Intraoral Fluid Testing

Recent developments of point-of-care testing (POCT) and in vitro diagnostic medical devices have provided analytical capabilities and reliable diagnostic results for rapid access at or near the patient's location. Nevertheless, the challenges of reliable diagnosis still remain an important factor in actual clinical trials before on-site medical treatment and making clinical decisions. New classes of POCT devices depict precise diagnostic technologies that can detect biomarkers in biofluids such as sweat, tears, saliva or urine. The introduction of a novel molecularly imprinted polymer (MIP) system as an artificial bioreceptor for the POCT devices could be one of the emerging candidates to improve the analytical performance along with physicochemical stability when used in harsh environments. Here, we review the potential availability of MIP-based biorecognition systems as custom artificial receptors with high selectivity and chemical affinity for specific molecules. Further developments to the progress of advanced MIP technology for biomolecule recognition are introduced. Finally, to improve the POCT-based diagnostic system, we summarized the perspectives for high expandability to MIP-based periodontal diagnosis and the future directions of MIP-based biosensors as a wearable format.

Electrochemically Deposited Molecularly Imprinted Polymer-Based Sensors

This review is dedicated to the development of molecularly imprinted polymers (MIPs) and the application of MIPs in sensor design. MIP-based biological recognition parts can replace receptors or antibodies, which are rather expensive. Conducting polymers show unique properties that are applicable in sensor design. Therefore, MIP-based conducting polymers, including polypyrrole, polythiophene, poly(3,4-ethylenedioxythiophene), polyaniline and ortho-phenylenediamine are frequently applied in sensor design. Some other materials that can be molecularly imprinted are also overviewed in this review. Among many imprintable materials conducting polymer, polypyrrole is one of the most suitable for molecular imprinting of various targets ranging from small organics up to rather large proteins. Some attention in this review is dedicated to overview methods applied to design MIP-based sensing structures. Some attention is dedicated to the physicochemical methods applied for the transduction of analytical signals. Expected new trends and horizons in the application of MIP-based structures are also discussed.

Molecularly imprinted polypyrrole based sensor for the detection of SARS-CoV-2 spike glycoprotein

This study describes the application of a polypyrrole-based sensor for the determination of SARS-CoV-2-S spike glycoprotein. The SARS-CoV-2-S spike glycoprotein is a spike protein of the coronavirus SARS-CoV-2 that recently caused the worldwide spread of COVID-19 disease. This study is dedicated to the development of an electrochemical determination method based on the application of molecularly imprinted polymer technology. The electrochemical sensor was designed by molecular imprinting of polypyrrole (Ppy) with SARS-CoV-2-S spike glycoprotein (MIP-Ppy). The electrochemical sensors with MIP-Ppy and with polypyrrole without imprints (NIP-Ppy) layers were electrochemically deposited on a platinum electrode surface by a sequence of potential pulses. The performance of polymer layers was evaluated by pulsed amperometric detection. According to the obtained results, a sensor based on MIP-Ppy is more sensitive to the SARS-CoV-2-S spike glycoprotein than a sensor based on NIP-Ppy. Also, the results demonstrate that the MIP-Ppy layer is more selectively interacting with SARS-CoV-2-S glycoprotein than with bovine serum albumin. This proves that molecularly imprinted MIP-Ppy-based sensors can be applied for the detection of SARS-CoV-2 virus proteins.

Towards deployable electrochemical sensors for per- and polyfluoroalkyl substances (PFAS)

Per- and polyfluoroalkyl substances (PFAS) are an emerging class of pervasive and harmful environmental micropollutant with negative health effects on humans. Therefore, there has been extensive research into the remediation (i.e., the detection, extraction, and destruction) of these chemicals. For efficient extraction and destruction, PFAS contamination must be detected at its onset; however, conventional PFAS detection methods rely on sample collection and transport to a centralized facility for testing, which is expensive and time-consuming. Electrochemistry offers a robust, inexpensive, and deployable sensing strategy that could detect pollution at its onset; however, the electrochemical inactivity of PFAS necessitates the use of a surface functionalization strategy. Molecularly imprinted polymers (MIPs), which are a popular surface functionalization strategy, have been around since the 1980s for specific electrochemical detection and have expanded electrochemical detection to analytes that are not electrochemically active. MIPs have been more recently demonstrated for the detection of a variety of PFAS species, but additional advances must be made for realization of a deployable, electrochemical MIP-based sensor. This Feature highlights the history of MIPs for PFAS detection and our group's recent advances that are essential to enable the creation of a deployable electrochemical PFAS sensor: development of rigorous analytical standards to quantify interferent effects, miniaturization of the detection platform for quantification in river water, the use of ambient O₂ as the mediator molecule for detection, and the development of hardware for in-field multiplexed electrochemical sensing.

Hosseini I, Raeissi K, Karimzadeh F, Jalali M, Kharaziha M, Sheibani S, Shariati L, Presley JF, Vali H, Mahshid S. Gold Nano/Micro-Islands Overcome the Molecularly Imprinted Polymer Limitations to Achieve Ultrasensitive Protein Detection

Here, we report on an electrochemical biosensor based on core-shell structure of gold nano/micro-islands (NMIs) and electropolymerized imprinted ortho-phenylenediamine (o-PD) for detection of heart-fatty acid binding protein (H-FABP). The shape and distribution of NMIs (the core) were tuned by controlled electrodeposition of gold on a thin layer of electrochemically reduced graphene oxide (ERGO). NMIs feature a large active surface area to achieve a low detection limit (2.29 fg mL^-1, a sensitivity of 1.34 × 10¹³ μA mM^-1) and a wide linear range of detection (1 fg mL^-1 to 100 ng mL^-1) in PBS. Facile template H-FABP removal from the layer (the shell) in less than 1 min, high specificity against interference from myoglobin and troponin T, great stability at ambient temperature, and rapidity in detection of H-FABP (approximately 30 s) are other advantages of this biomimetic biosensor. The electrochemical measurements in human serum, human plasma, and bovine serum showed acceptable recovery (between 91.1 ± 1.7 and 112.9 ± 2.1%) in comparison with the ELISA method. Moreover, the performance of the biosensor in clinical serum showed lower detection time and limit of detection against lateral flow assay (LFA) rapid test kits, as a reference method. Ultimately, the proposed biosensor based on the core-shell structure of gold NMIs and MIP opens interesting avenues in the detection of proteins with low cost, high sensitivity and significantstability for clinical applications.

Advances in Molecularly Imprinted Polymers Based Affinity Sensors (Review)

Recent challenges in biomedical diagnostics show that the development of rapid affinity sensors is very important issue. Therefore, in this review we are aiming to outline the most important directions of affinity sensors where polymer-based semiconducting materials are applied. Progress in formation and development of such materials is overviewed and discussed. Some applicability aspects of conducting polymers in the design of affinity sensors are presented. The main attention is focused on bioanalytical application of conducting polymers such as polypyrrole, polyaniline, polythiophene and poly(3,4-ethylenedioxythiophene) ortho-phenylenediamine. In addition, some other polymers and inorganic materials that are suitable for molecular imprinting technology are also overviewed. Polymerization techniques, which are the most suitable for the development of composite structures suitable for affinity sensors are presented. Analytical signal transduction methods applied in affinity sensors based on polymer-based semiconducting materials are discussed. In this review the most attention is focused on the development and application of molecularly imprinted polymer-based structures, which can replace antibodies, receptors, and many others expensive affinity reagents. The applicability of electrochromic polymers in affinity sensor design is envisaged. Sufficient biocompatibility of some conducting polymers enables to apply them as "stealth coatings" in the future implantable affinity-sensors. Some new perspectives and trends in analytical application of polymer-based semiconducting materials are highlighted.

Development of a portable MIP-based electrochemical sensor for detection of SARS-CoV-2 antigen

The current COVID-19 pandemic caused by SARS-CoV-2 coronavirus is expanding around the globe. Hence, accurate and cheap portable sensors are crucially important for the clinical diagnosis of COVID-19. Molecularly imprinted polymers (MIPs) as robust synthetic molecular recognition materials with antibody-like ability to bind and discriminate between molecules can perfectly serve in building selective elements in such sensors. Herein, we report for the first time on the development of a MIP-based electrochemical sensor for detection of SARS-CoV-2 nucleoprotein (ncovNP). A key element of the sensor is a disposable sensor chip - thin film electrode - interfaced with a MIP-endowed selectivity for ncovNP and connected with a portable potentiostat. The resulting ncovNP sensor showed a linear response to ncovNP in the lysis buffer up to 111 fM with a detection and quantification limit of 15 fM and 50 fM, respectively. Notably, the sensor was capable of signaling ncovNP presence in nasopharyngeal swab samples of COVID-19 positive patients. The presented strategy unlocks a new route for the development of rapid COVID-19 diagnostic tools.

Conducting Polymers in the Design of Biosensors and Biofuel Cells

Fast and sensitive determination of biologically active compounds is very important in biomedical diagnostics, the food and beverage industry, and environmental analysis. In this review, the most promising directions in analytical application of conducting polymers (CPs) are outlined. Up to now polyaniline, polypyrrole, polythiophene, and poly(3,4-ethylenedioxythiophene) are the most frequently used CPs in the design of sensors and biosensors; therefore, in this review, main attention is paid to these conducting polymers. The most popular polymerization methods applied for the formation of conducting polymer layers are discussed. The applicability of polypyrrole-based functional layers in the design of electrochemical biosensors and biofuel cells is highlighted. Some signal transduction mechanisms in CP-based sensors and biosensors are discussed. Biocompatibility-related aspects of some conducting polymers are overviewed and some insights into the application of CP-based coatings for the design of implantable sensors and biofuel cells are addressed. New trends and perspectives in the development of sensors based on CPs and their composites with other materials are discussed.

Nanodiamonds and hydrogen-substituted graphdiyne heteronanostructure for the sensitive impedimetric aptasensing of myocardial infarction and cardiac troponin I

A novel heteronanostructure of nanodiamonds (NDs) and hydrogen-substituted graphdiyne (HsGDY) (denoted as HsGDY@NDs) was prepared for the impedimetric aptasensing of biomarkers such as myoglobin (Myo) and cardiac troponin I (cTnI). Basic characterizations revealed that the HsGDY@NDs were composed of nanospheres with sizes of 200-500 nm. In these nanospheres, NDs were embedded within the HsGDY network. The HsGDY@NDs nanostructure, which integrated the good chemical stability and three-dimensional porous networks of HsGDY, and the good biocompatibility and electrochemical activity of NDs, could immobilize diverse aptamer strands and recognize target biomarkers. Compared with HsGDY- and NDs-based aptasensors, the HsGDY@NDs-based aptasensors exhibited superior sensing performances for Myo and cTnI, giving low detection limits of 6.29 and 9.04 fg mL^-1 for cTnI and Myo, respectively. In addition, the HsGDY@NDs-based aptasensors exhibited high selectivity, good stability, reproducibility, and acceptable applicability in real human serum. Thus, the construction of HsGDY@NDs-based aptasensor is expected to broaden the application of porous organic frameworks in the sensing field and provide a prospective approach for the early detection of disease biomarkers.

Functional Polymers Structures for (Bio)Sensing Application-A Review

In this review we present polymeric materials for (bio)sensor technology development. We focused on conductive polymers (conjugated microporous polymer, polymer gels), composites, molecularly imprinted polymers and their influence on the design and fabrication of bio(sensors), which in the future could act as lab-on-a-chip (LOC) devices. LOC instruments enable us to perform a wide range of analysis away from the stationary laboratory. Characterized polymeric species represent promising candidates in biosensor or sensor technology for LOC development, not only for manufacturing these devices, but also as a surface for biologically active materials' immobilization. The presence of biological compounds can improve the sensitivity and selectivity of analytical tools, which in the case of medical diagnostics is extremely important. The described materials are biocompatible, cost-effective, flexible and are an excellent platform for the anchoring of specific compounds.

How Reliable Is the Electrochemical Readout of MIP Sensors?

Electrochemical methods offer the simple characterization of the synthesis of molecularly imprinted polymers (MIPs) and the readouts of target binding. The binding of electroinactive analytes can be detected indirectly by their modulating effect on the diffusional permeability of a redox marker through thin MIP films. However, this process generates an overall signal, which may include nonspecific interactions with the nonimprinted surface and adsorption at the electrode surface in addition to (specific) binding to the cavities. Redox-active low-molecular-weight targets and metalloproteins enable a more specific direct quantification of their binding to MIPs by measuring the faradaic current. The in situ characterization of enzymes, MIP-based mimics of redox enzymes or enzyme-labeled targets, is based on the indication of an electroactive product. This approach allows the determination of both the activity of the bio(mimetic) catalyst and of the substrate concentration.

Molecularly Imprinted Electrochemical Sensors: Analytical and Pharmaceutical Applications Based on Ortho-Phenylenediamine Polymerization

Background:

The molecular imprinting technique has been applied in many fields including separation, artificial antibody mimics, catalysis, sensing studies, and drug delivery. The reasons for the popularity of this technique among the researchers are high selectivity due to the cavities that are formed on the polymer surface for the specific analyte, high robustness, high durability under extreme conditions and low cost. When these advantages are combined with the advantages of electrochemical methods such as rapid response time, ease of use, cheapness and miniaturizability, Molecularly Imprinted Polymer (MIP) based electrochemical sensors turn out to be a widely-preferred sensing tool.

Objective:

This article provides the reader with information on MIP-based electrochemical sensors and reviews the applications of the MIP sensors prepared by electropolymerization of orthophenylenediamine, a monomer whose mechanical and chemical stability is very high.

Results and Conclusion:

The literature survey summarized in this review shows that cyclic voltammetry is the most widely preferred electrochemical technique for electropolymerization of o-PD. The media chosen is generally acetate or phosphate buffers with different pH values. Although there are numerous solvents used for template removal, generally methanol and NaOH have been chosen.

Fluorescent aptasensor based on D-AMA/F-CSC for the sensitive and specific recognition of myoglobin

A novel fluorescent biosensor based on dabcyl [(E)-4-((4-(dimethylamino) phenyl) diazenyl)benzoic acid] -modified anti-Mb aptamer (D-AMA) and 6-FAM(6-carboxyfluorescein) -modified complementary short chain (F-CSC)for the specific and sensitive detection of Mb levels is presented in this study. In PBS buffer solution, D-AMA bound to F-CSC, and then dabcyl quenched the fluorescence of 6-FAM. After adding Mb into the system, D-AMA bound to Mb and separated from F-CSC. The fluorescence of 6-FAM was restored after it separated from dabcyl. The assay exhibited high specificity and sensitivity toward Mb, with a low limit of detection of 0.07 ng/mL (S/N = 3) and linear relationships of 0.1-5 ng/mL. It was further applied to detect Mb levels in spiked human blood sera samples.

Label-free SERS diagnostics of radiation-induced injury via detecting the biomarker Raman signal in the serum and urine bio-samples based on Au-NPs array substrates

A sensitive approach based on surface enhanced Raman spectroscopy (SERS) has been developed to evaluate the radiation caused biological injury. To achieve the effective SERS substrate, canonical anodic aluminum oxide (AAO) templates with regular array of nanotips were fabricated, and by plasma sputtering the gold nanoparticles (Au-NPs) were distributed on the nanotips to form the Au-NPs array with plenty of hotspots. The SERS substrates were utilized to examine the serum samples taken from the mice with the treatment of total body irradiation (TBI) of X-ray. The impact of TBI on the mice was analyzed and it was found that the SERS peak intensity at 532 cm^-1 increased as a function of duration or dose of TBI. We confirmed that this Raman signature belongs to the myoglobin as a biomarker for the muscle damage due to the radiation caused injury. Furthermore, we also tested several blood and urine specimen of cancer patients who received radiotherapy. The results showed that our approach to some extent could distinguish the bio-samples from normal, X-ray treated and untreated individuals. Therefore, the proposed methodology may have the potential for prompt prognosis of radiation injury at early stage.

Synthesis of Zr-coordinated amide porphyrin-based two-dimensional covalent organic framework at liquid-liquid interface for electrochemical sensing of tetracycline

Highly-conductive two-dimensional covalent organic framework (COF) displays prominent applications in various fields of science and technology. This paper reports the design and liquid-liquid interface synthesis of a novel Zr-coordinated amide porphyrin-based 2D COF (Zr-amide-Por-based 2D COF). The COF adopts a graphene-like multilayer structure with the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) band gap of 1.6 eV. The ordered multilayer structure of the amide COF was confirmed through a series of characterization techniques, including scanning electron microscopy, high-resolution transmission electron microscopy, atomic force microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. In particular, the inherent-ordered structure of Zr-amide-Por-based 2D COF with Zr as the catalytically active center confers several distinct advantages to the material, such as high conductivity and high electrocatalysis performance. A molecularly imprinted tetracycline electrochemiluminescence sensor was constructed based on the Zr-amide-Por-based 2D COF, and gate control effect was used as a signal-generation mechanism. Under optimal conditions, the sensor showed a good linear relationship with tetracycline in the concentration range of 5-60 pM, with a detection limit of 2.3 pM. Because the sensor is rapid, cost-efficient, highly sensitive, and specific, it can be considered as a viable platform for veterinary drug residue monitoring.

Evaluation of Molecularly Imprinted Polymers for Point-of-Care Testing for Cardiovascular Disease

Molecular imprinting is a rapidly growing area of interest involving the synthesis of artificial recognition elements that enable the separation of analyte from a sample matrix and its determination. Traditionally, this approach can be successfully applied to small analyte (<1.5 kDa) separation/ extraction, but, more recently it is finding utility in biomimetic sensors. These sensors consist of a recognition element and a transducer similar to their biosensor counterparts, however, the fundamental distinction is that biomimetic sensors employ an artificial recognition element. Molecularly imprinted polymers (MIPs) employed as the recognition elements in biomimetic sensors contain binding sites complementary in shape and functionality to their target analyte. Despite the growing interest in molecularly imprinting techniques, the commercial adoption of this technology is yet to be widely realised for blood sample analysis. This review aims to assess the applicability of this technology for the point-of-care testing (POCT) of cardiovascular disease-related biomarkers. More specifically, molecular imprinting is critically evaluated with respect to the detection of cardiac biomarkers indicative of acute coronary syndrome (ACS), such as the cardiac troponins (cTns). The challenges associated with the synthesis of MIPs for protein detection are outlined, in addition to enhancement techniques that ultimately improve the analytical performance of biomimetic sensors. The mechanism of detection employed to convert the analyte concentration into a measurable signal in biomimetic sensors will be discussed. Furthermore, the analytical performance of these sensors will be compared with biosensors and their potential implementation within clinical settings will be considered. In addition, the most suitable application of these sensors for cardiovascular assessment will be presented.

Dual-modality impedimetric immunosensor for early detection of prostate-specific antigen and myoglobin markers based on antibody-molecularly imprinted polymer

A new dual-modality immunosensor based on molecularly imprinted polymer (MIP) and a nanostructured biosensing layer has fabricated for the simultaneous detection of two important markers including prostate-specific antigen (PSA) and myoglobin (Myo) in human serum and urine samples. In the first step, 3,3'-dithiodipropionic acid di(N-hydroxysuccinimide ester) (DSP) was self-assembled on a gold screen printed electrode (SPE). Then, the target proteins were attached covalently to the DSP-SPE. The imprinted cocktail polymer ((MIP(PSA, Myo)-SPE)) was synthesized at the SPE surface using acrylamide as monomer, N,N'-methylenebisacrylamide as a crosslinker, and PSA and Myo as the templates, respectively. The MIP-SPE was specific for the impedimetric sensing of PSA and Myo. After that, a nanocomposite (NCP) was synthesized based on the decorated magnetite nanoparticles with multi-walled carbon nanotube, graphene oxide and specific antibody for PSA (Ab). Then, NCP incubated with (MIP(PSA, Myo)-SPE. The modified electrodes and synthesized nanoparticles were characterized using electrochemical impedance spectroscopy, dynamic light scattering, surface plasmon resonance and scanning electron microscopy. The limits of detections were found to be 5.4 pg mL^-1 and 0.83 ng mL^-1 with the linear dynamic ranges of 0.01-100 and 1-20000 ng mL^-1 for PSA and Myo, respectively. The ability of proposed biosensor to detect PSA and Myo simultaneously with high sensitivity and specificity offers a powerful opportunity for the new generation of biosensors. This dual-analyte specific receptors-based device is highly desired for the integration with lab-on-chip kits to measure a wide panel of biomarkers present at ultralow levels during early stages of diseases progress.

Fluorometric determination of cardiac myoglobin based on energy transfer from a pyrene-labeled aptamer to graphene oxide

The authors describe a fluorometric assay for cardiac myoglobin (Mb), a marker for myocardial infarction. An Mb-binding aptamer was labeled with pyrene and adsorbed on the surface of graphene oxide (GO) via noncovalent and reversible binding forces. This causes the fluorescence of pyrene (best measured at excitation/emission wavelengths of 275/376 nm) to be quenched. However, fluorescence is restored on addition of pyrene due to the strong affinity between Mb and aptamer which causes its separation from GO. Fluorescence increases linearly in the 5.6-450 pM Mb concentration range, and the lower detection limit is 3.9 pM (S/N = 3). The assay was applied to the determination of cardiac Mb in spiked serum, and satisfactory results were obtained. Graphical abstract Schematic presentation of the detection of Mb (cardiac myoglobin) by using a fluorometric method based on pyrene-modified anti-Mb aptamer and GO (graphene oxide) through fluorescence quenching and subsequent recovery.

Recent Advances in Electrosynthesized Molecularly Imprinted Polymer Sensing Platforms for Bioanalyte Detection

The accurate detection of biological materials has remained at the forefront of scientific research for decades. This includes the detection of molecules, proteins, and bacteria. Biomimetic sensors look to replicate the sensitive and selective mechanisms that are found in biological systems and incorporate these properties into functional sensing platforms. Molecularly imprinted polymers (MIPs) are synthetic receptors that can form high affinity binding sites complementary to the specific analyte of interest. They utilise the shape, size, and functionality to produce sensitive and selective recognition of target analytes. One route of synthesizing MIPs is through electropolymerization, utilising predominantly constant potential methods or cyclic voltammetry. This methodology allows for the formation of a polymer directly onto the surface of a transducer. The thickness, morphology, and topography of the films can be manipulated specifically for each template. Recently, numerous reviews have been published in the production and sensing applications of MIPs; however, there are few reports on the use of electrosynthesized MIPs (eMIPs). The number of publications and citations utilising eMIPs is increasing each year, with a review produced on the topic in 2012. This review will primarily focus on advancements from 2012 in the use of eMIPs in sensing platforms for the detection of biologically relevant materials, including the development of increased polymer layer dimensions for whole bacteria detection and the use of mixed monomer compositions to increase selectivity toward analytes.

Advances in Molecularly Imprinting Technology for Bioanalytical Applications

In recent years, along with the rapid development of relevant biological fields, there has been a tremendous motivation to combine molecular imprinting technology (MIT) with biosensing. In this situation, bioprobes and biosensors based on molecularly imprinted polymers (MIPs) have emerged as a reliable candidate for a comprehensive range of applications, from biomolecule detection to drug tracking. Unlike their precursors such as classic immunosensors based on antibody binding and natural receptor elements, MIPs create complementary cavities with stronger binding affinity, while their intrinsic artificial polymers facilitate their use in harsh environments. The major objective of this work is to review recent MIP bioprobes and biosensors, especially those used for biomolecules and drugs. In this review, MIP bioprobes and biosensors are categorized by sensing method, including optical sensing, electrochemical sensing, gravimetric sensing and magnetic sensing, respectively. The working mechanism(s) of each sensing method are thoroughly discussed. Moreover, this work aims to present the cutting-edge structures and modifiers offering higher properties and performances, and clearly point out recent efforts dedicated to introduce multi-sensing and multi-functional MIP bioprobes and biosensors applicable to interdisciplinary fields.

Molecularly imprinted nanoparticles based plasmonic sensors for real-time Enterococcus faecalis detection

Human fecal contamination poses a crucial environmental and health threat in recent years, resulting in the difficulties of access to clean water. According to the World Health Organization, several fecal bacteria, particularly Enterococci species, are present in human intestinal flora. Enterococcus faecalis (E. faecalis) is one of the indicator bacteria that have been utilized as a pollution indicator in water. However, existing technologies and detection strategies face multiple challenges in terms of low affinity for detection and labelling requirements that limit their access to large scale applications. Here, we present a label-free molecular fingerprinting strategy on a plasmonic sensor to detect E. fecalis from aqueous and seawater samples. The kinetic performance of platform was comprehensively evaluated and the platform provided four orders of magnitude detection range with a low limit of detection (down to ~100 bacteria/mL) and a high correlation coefficient value (> 0.99) in the range of 2 × 10⁴-1 × 10⁸ cfu/mL. The platform also denoted a selectivity and specificity while other bacteria (E. coli, B. subtilis, and S. aureus) samples were applied. Multiple time use and relatively long shelf-life are superior to the existing modality. The presented method is one of the fascinating surface modification technique that utilizes biotarget as a recognition element itself, providing a broad range of versatility to replica other biotargets with different molecular structure, size, and physicochemical properties. Such a reliable and versatile platform would hold potential applications from microbiome characterization to forensics by revitalizing obsolescent detection strategies.

Nanostructured aptamer-based sensing platform for highly sensitive recognition of myoglobin

A composite was prepared from PtSn nanoparticles and carbon nanotubes (PtSnNP/CNTs) and applied to the electrochemical determination of myoglobin (Mb). An Mb-aptamer was immobilized on a glassy carbon electrode (GCE), and hexcyanoferrate was used as an electrochemical probe. The PtSnNP/CNTs were synthesized by a microwave-aided ethylene glycol reduction method. Detection is based on electron transfer inhibition that is caused by the folding and conformational change of the Mb-aptamer in the presence of Mb. The amperometric signal for hexacyanoferrate, best measured at 0.2 V vs. Ag/AgCl depends on the concentration of Mb that interacts with the aptamer on the GCE. This approach is selective and sensitive for Mb due to (a) the highly specific recognition ability of the aptamer for Mb, (b) the powerful electronic properties of carbon nanotubes, (c) the arranged decoration of CNTs with PtSnNPs, and (d), the superior electron transfer to hexacyanoferrate. The assay is highly selective, with linear relationships from 0.01-1 nM and 10 nM-200 nM, and a limit of detection as low as 2.2 ± 0.1 pM. The modified GCE was applied to the quantitation of Mb in spiked human serum samples. Graphical abstract Schematic illustration of the method for Mb detection.

A new composite of graphene and molecularly imprinted polymer based on ionic liquids as functional monomer and cross-linker for electrochemical sensing 6-benzylaminopurine

Molecularly imprinted polymers prepared using traditional functional monomers and cross-linkers exhibit slow binding kinetics, low electrocatalytic activity and adsorption capacity. Herein, we report a new composite of ionic liquid-based graphene and molecularly imprinted polymer (IL-GR-MIP) with high electrocatalytic activity and adsorption capacity to construct an effective electrochemical sensor for 6-benzylaminopurine (6-BAP). Our objective was to enhance the efficiency of the sensor by incorporating more IL in the MIP framework. We synthesized IL-GR-MIP using ionic liquid 1-vinyl-3-butylimidazolium tetrafluoroborate (IL₁) as functional monomer, ionic liquid 1,4-butanediyl-3,3'-bis-l-vinylimidazolium dibromide (IL₂) as cross-linker, 6-BAP as template, and GR as supporter. IL-GR-MIP was characterized by Fourier transform infrared spectroscopy, thermal gravimetric analysis, Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscope. Compared with GR-MIP composites based on methacrylic acid or IL₁ as functional monomer, N, N'-methylenebisacrylamide and ethylene glycol dimethacrylate as cross-linker, the IL-GR-MIP (prepared with ionic liquids as functional monomer and cross-linker) sensor exhibited highest peak current for 6-BAP. The results indicate the ability of IL₂ as cross-linker to enhance electrocatalytic activity and adsorption capacity for 6-BAP of IL-GR-MIP. Under the optimized conditions, the peak current of IL-GR-MIP sensor was linear to 6-BAP concentration in the range of 0.5-50 μM with a detection limit of 0.2 μM (S/N = 3). The IL-GR-MIP sensor exhibited good selectivity with the anti-interference ability of 1000-fold ascorbic acid in 6-BAP determination. Furthermore, we demonstrated practical applicability of IL-GR-MIP sensor in detecting 6-BAP in real samples with satisfactory results.

Influence of Luminol Doping of Poly(o-phenylenediamine) on the Spectral, Morphological, and Fluorescent properties: A Potential Fluorescent Marker for Early detection and Diagnosis of Leishmania donovani

There has been a steady progress in the development of doped conjugated polymers to remarkably improve their photo physical properties for their application as biomarkers. With a view to enhance the spectral, morphological, and photo physical properties of poly(o-phenylenediamine) (POPD), the present work reports the synthesis of poly(o-phenylenediamine) and doping of this polymer using luminol. The formation of luminol-doped POPD was confirmed by infrared and ultraviolet-visible spectroscopies and X-ray diffraction studies. The energy band gap values and oscillator strength of luminol in acidic, basic, and neutral media were computed by density functional theory calculations using the B3LYP/6-31G (d) basis set and were compared with experimental data. The luminol doped POPDs show significant in vitro anti-leishmanial activity. Live cell imaging also proved that these molecules bind with the organelle of Leishmania also. These luminol doped POPDs were found non-toxic at the used concentrations on THP-1 derived human macrophage cells through methyl tetrazolium (MTT) assay. The results revealed that luminol doped POPDs were potentially non-toxic to human cells though exhibited immense potential to be used as a fluorescent marker to label Leishmania donovani for diagnostic and other studies.