Molecularly Imprinted Polymer Film Research Articles

An all-in-one approach for self-powered sensing: A methanol fuel cell modified with a molecularly imprinted polymer for cancer biomarker detection

• A hybrid methanol fuel cell operating with a biosensor. • One electrode of the fuel cell is the biosensing element. • A molecularly-imprinted polymer tailored in situ for carcinoembryonic antigen. • The overall power of the hybrid cell is carcinoembryonic antigen concentration dependent. • This hybrid fuel cell pursues an application in point-of-care. This work describes the development of an innovative electrochemical biosensor comprehending a passive direct methanol fuel cell (DMFC) assembly, modified by a layer of a molecularly imprinted polymer (MIP) on a carbon fabric anode electrode containing Pt/Ru nanoparticles. This MIP film was prepared from poly(3,4-ethylenedioxythiophene) (PEDOT) and polypyrrole (PPy) obtained by in situ electropolymerization of the corresponding monomers on the anode electrode surface. This MIP film is designed to detect an important cancer biomarker- carcinoembryonic antigen (CEA). This innovative, all-in-one device works in a simple way. First, CEA is incubated on the anode container of the fuel cell, then methanol is added, followed by the response evaluation (polarization curves determination). As CEA selectively interacts with the MIP film, it blocks the methanol's access to the Pt catalyst, remains specific bonded, and interferes with the subsequent polarization curves of the DMFC. Polarization curves obtained in the presence of standard solutions prepared in buffer and human serum confirmed linear responses of log CEA concentration ranging from 30 to 30 000 ng/mL in both media. The biosensor DMFC showed a sensitive response with a detection limit of 4.41 ng/mL when an aqueous 0.05 M methanol solution was used as fuel. When methanol was replaced by an ethanol solution of the same concentration (using the same setup developed for the DMFC), the lower detection limit of 3.52 ng/mL was obtained. Overall, the obtained results show that methanol/ethanol fuel cells operating without flow-through can be successfully used for the fabrication of self-powered biosensors. The novel biosensor concept presented here is simple, inexpensive, and effective, and can be further developed to meet point-of-care requirements.

Selective Impedimetric Chemosensing of Carcinogenic Heterocyclic Aromatic Amine in Pork by dsDNA-Mimicking Molecularly Imprinted Polymer Film-Coated Electrodes.

Inspired by the easy intercalation of quinoxaline heterocyclic aromatic amines (HAAs) in double-stranded DNA (dsDNA), we synthesized a nucleobase-functionalized molecularly imprinted polymer (MIP) as the recognition unit of an impedimetric chemosensor for the selective determination of a 2-amino-3,7,8-trimethyl-3H-imidazo[4,5-f]quinoxaline (7,8-DiMeIQx) HAA. HAAs are generated in meat and fish processed at high temperatures. They are considered to be potent hazardous carcinogens. The MIP film was prepared by potentiodynamic electropolymerization of a pre-polymerization complex of two adenine- and one thymine-substituted bis(2,2′-bithien-5-yl)methane functional monomer molecules with one 7,8-DiMeIQx template molecule, in the presence of the 2,4,5,2′,4′,5′-hexa(thiophene-2-yl)-3,3′-bithiophene cross-linking monomer, in solution. The as-formed MIP chemosensor allowed for the selective impedimetric determination of 7,8-DiMeIQx in the 47 to 400 μM linear dynamic concentration range with a limit of detection of 15.5 μM. The chemosensor was successfully applied for 7,8-DiMeIQx determination in the pork meat extract as a proof of concept.

An ultrasensitive molecularly imprinted polymer-based electrochemical sensor for the determination of SARS-CoV-2-RBD by using macroporous gold screen-printed electrode

Herein, a novel molecularly imprinted polymer (MIP) based electrochemical sensor for the determination of the receptor-binding domain of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2-RBD) has been developed. For this purpose, first, a macroporous gold screen-printed electrode (MP-Au-SPE) has been fabricated. The MIP was then synthesized on the surface of the MP-Au-SPE through the electro-polymerization of ortho-phenylenediamine in the presence of SARS-CoV-2-RBD molecules as matrix polymer, and template molecules, respectively. During the fabrication process, the SARS-CoV-2-RBD molecules were embedded in the polymer matrix. Subsequently, the template molecules were removed from the electrode by using alkaline ethanol. The template molecules removal was studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), and attenuated total reflectance spectroscopy (ATR). The fabricated MIP film acted as an artificial recognition element for the measurement of SARS-CoV-2-RBD. The EIS technique was used for the measurement of the SARS-CoV-2-RBD in the saliva solution. The electron transfer resistance (Ret) of the MIP-based sensor in a ferri/ferrocyanide solution increased as the SARS-CoV-2-RBD concentration increased due to the occupation of the imprinted cavities by the SARS-CoV-2-RBD. The MIP-based sensor exhibited a good response to the SARS-CoV-2-RBD in the concentration range between 2.0 and 40.0 pg mL-1 with a limit of detection of 0.7 pg mL-1. The obtained results showed that the fabricated MIP sensor has high selectivity sensitivity, and stability.

Preparation of molecularly imprinted polymers-functionalized silica nanoparticles for the separation and recognition of aristolochic acids

马兜铃酸是马兜铃科植物中含有硝基菲羧酸基团的一类物质,被广泛应用于各种疾病的治疗,研究表明含有马兜铃酸的植物或植物衍生产品对人体有害,需要监测药物中马兜铃酸的存在。分子印迹聚合物对目标物的高亲和力使其特别适合作为吸附剂从混合物中去除和识别目标物。以SiO2胶体纳米颗粒为基底,利用表面分子印迹的方法合成了核-壳结构SiO2表面印迹纳米颗粒(SiO2@MIP NPs)。采用紫外可见光谱研究了模板分子马兜铃酸Ⅰ和功能单体丙烯酸、甲基丙烯酸、2-乙烯基吡啶、丙烯酰胺及甲基丙烯酰胺的作用,发现2-乙烯基吡啶与马兜铃酸Ⅰ的作用最强,被选为制备印迹聚合物的单体。采用傅立叶变换红外光谱仪(FT-IR)、透射电子显微镜(TEM)、热重分析仪、氮气吸附比表面分析仪对分子印迹聚合物进行了表征。TEM显示印迹纳米颗粒的粒径在270 nm左右,分子印迹层的厚度为35 nm,有利于模板分子的传输。TEM、FT-IR和热重分析仪的结果均证明实验成功合成了分子印迹聚合物。实验进一步研究了印迹聚合物SiO2@MIP NPs和非印迹聚合物SiO2@NIP NPs的吸附性能,并结合SiO2@MIP NPs和SiO2@NIP NPs的比表面积和孔径测定数据,发现SiO2@MIP NPs表面的印迹位点是导致二者吸附差异的主要原因。SiO2@MIP NPs和SiO2@NIP NPs的动力学吸附表明SiO2@MIP NPs具有快的吸附平衡时间(120 s),而且SiO2@MIP NPs的吸附行为符合Langmuir单分子层吸附。SiO2@MIP NPs的选择性通过印迹因子(IF)和选择性系数(SC)来评价。实验结果表明,SiO2@MIP NPs具有高的印迹因子(4.9),对模板结构类似物有较好的选择性,选择系数为2.3~6.6。最后将制备的SiO2@MIP NPs作为吸附剂用于加标中药样品川木通的预处理,用HPLC进行分析测定,方法的回收率为73%~83%,实验结果显示SiO2@MIP NPs可作为高选择性材料用于中药中马兜铃酸的选择性分离分析。

Molecular imprinting of hemispherical pore-structured thin films via colloidal lithography for gaseous formaldehyde Gravimetric sensing

In this study, formaldehyde (HCHO)-imprinted hemispherical pore-patterned thin films, consisting of poly(2-(trifluoromethyl)acrylic acid–co–ethylene glycol dimethacrylate–co–styrene) (poly(TFMAA–co–EGDMA–co–ST)), were fabricated using the design of molecularly imprinted polymers (MIPs) and a subsequent lithographic micro/nanoimprinting method to amplify HCHO sensing signals in quartz crystal microbalance (QCM) sensors. Its molecular imprinting condition was optimized by controlling the added amount of a ST monomer in a MIP precursor solution. From the resonant frequency change with respect to HCHO adsorption, the imprinting factor of the porous MIP film was calculated to have a value of 2.38 and the sensitivity (0.132 mg g−1 ppm−1) of the porous MIP film exhibited markedly improved characteristics with respect to the porous non-imprinted polymer (NIP) film (0.05 mg g−1 ppm−1). The selectivity of the MIP-QCM sensors for the detection of HCHO was examined in the presence of other analogous toxic gases such as hydrogen chloride and hydrogen fluoride. The HCHO-absorbed porous MIP film had higher selective features with selectivity coefficients (k* ≈ 3.83 (HCl) and 4.46 (HF)) than porous NIP films (k* ≈ 1.53 (HCl) and 2.20 (HF)). Moreover, the relative selectivity of the porous MIP film appeared to be 2.03–2.5, which was higher than those of the planar MIP film (1.70–1.73).

RETRACTED: CdSe Quantum Dot Nanoparticles: Synthesis and Application in the Development of Molecularly Imprinted Polymer-Based Dual Optical Sensors

In this study, two types of CdSe, including nanoparticles and quantum dots, were synthesized. CdSe quantum dot nanoparticles were prepared via the hydrothermal technique at 140 °C for 8 h. The prepared CdSe materials were used as fluorimetric sensors aimed at the simultaneous analysis and detection of methamphetamine (Metha) as well as carbamazepine (Carba) drugs. Besides, the fluorimetric sensor was assembled depending on molecularly imprinted polymer (MIP) films with two sizes of cadmium selenide quantum dots as fluorophores source. The mechanistic synthesis of the fluorimetric sensor was based on covering the CdSe quantum dot nanoparticle surfaces with MIP film; afterward, a mixture of powdered yellow-CdSe@MIPs (y-CdSe@MIPs) and red-CdSe@MIPs (r-CdSe@MIPs) nanocomposites was applied for the simultaneous optical determination of Metha and Carba. Under optimal conditions, detection limits (DL) of 0.15 and 0.2 nM, as well as linear dynamic ranges (LDR) of 0.5 and 260 nM were acquired for Metha and Carba, respectively. Additionally, the application of the offered optical dual sensor was studied in human blood plasma as well as urine analytes.

Electropolymerization of molecularly imprinted polypyrrole film on multiwalled carbon nanotube surface for highly selective and stable determination of carcinogenic amaranth

A novel amaranth electrochemical sensor was produced by electrodepositing a molecularly imprinted polypyrrole film in the presence of amaranth on a multi-walled carbon nanotube (MWCNT) surface. Template molecules were completely eluted through an innovative strategy that only requires the application of a fixed electrical potential in a blank phosphate buffer solution. Obviously, this strategy is much faster and more eco-friendly. The molecularly imprinted polymer (MIP)-based electrochemical sensor was systematically investigated by scanning electron microscopy, atomic force microscopy, X-ray diffraction, cyclic voltammetry, and electrochemical impedance spectroscopy. The resultant MIP/MWCNT modified glass carbon electrode (MIP/MWCNT/GCE) shows satisfactory electroactive surface area and charge transfer resistance. As expected, the electrochemical response signals were significantly amplified at the MIP/MWCNT/GCE. Under optimal conditions, the proposed MIP/MWCNT/GCE exhibits extraordinarily good analytical performance for amaranth detection, with two wide detection ranges (0.007 μM to 1.0 μM, and 0.40 μM to 17 μM) and detection possible down to 0.4 nM. Moreover, the polypyrrole MIP films show high binding affinity and specifically identifies amaranth molecules, enabling the robust detection of amaranth in a complicated matrix with excellent selectivity, reproducibility, and stability. The proposed sensor achieves accurate detection of amaranth concentration in various fruit drinks with acceptable recovery.

Molecularly Imprinted Electrochemical Sensor Based on 3D Wormlike PEDOT-PPy Polymer for the Sensitive Determination of Rutin in Flos Sophorae Immaturus

A molecularly imprinted polymer (MIP) with 3D worm-like nanorod structures was constructed by cyclic voltammetry (CV) polymerization, using 3,4-ethylenedioxythiophene (EDOT) and pyrrole (Py) as bifunctional monomers, and rutin as the template on a glassy carbon electrode (GCE). The optimum polymerization conditions of MIP were obtained by the orthogonal test. The range analysis suggested that the potential range was the most influential factor. Compared with MIP/1.5 and MIP/1.9, the MIP films prepared in the potential range of 0–1.7 V (MIP/1.7) had better current response to rutin, faster charge transfer rate and higher doping levels by differential pulse voltammetry (DPV), Chronocoulometry and X-ray photoelectron spectroscopy (XPS) analysis. Rutin could be detected in the concentration range of 0.5 nM to 1 μM, and 5 to 50 μM with the low detection limit as 0.24 nM (S/N = 3). Moreover, MIP/1.7 exhibited 3-fold increase current response toward rutin by DPV when compared with the corresponding non-imprinted polymer (NIP), revealing the success of the imprinting. This sensor also exhibited high selectivity, good long-term stability, and acceptable reproducibility. The rutin content in Flos Sophorae Immaturus (FSI) was 25.37% with good accuracy.

Self-Reporting Molecularly Imprinted Polymer with Covalently Immobilized Ferrocene Redox Probe for Selective Electrochemical Sensing of P-Synephrine

Molecularly imprinted polymers (MIPs) belong to the illustrious examples of bio-mimicking recognizing materials.1 They have found numerous applications in the fabrication of selective chemosensors.2 Their analytical parameters, such as sensitivity, selectivity, and detectability, are almost as high as those of biosensors. Additionally, MIP based chemosensors are superior to biosensors concerning their ease of fabrication, durability, and tolerance to harsh conditions, including elevated or decreased temperature, high ionic strength, extreme pH values, the presence of heavy metal ions and organic solvents in the samples. Conductive MIPs have recently become more frequently applied. That is mainly due to the easy control of MIPs deposition as thin films by electropolymerization.3 For the electrochemical determination of non-electroactive analytes, some external redox probe is usually added to the test solution. It is assumed that target analyte molecules' binding into molecular cavities causes MIP film swelling or shrinking. According to the so-called "gate effect" mechanism, this polymer "breathing" causes changes in the redox probe permeability through an MIP film, thus changing faradaic current corresponding to the redox probe's reduction or oxidation in cyclic voltammetry (CV) and differential pulse voltammetry (DPV) determinations.4-5 This mechanism is operative for nonconductive MIP films. Another mechanism may be considered for surface imprinted macromolecular compounds, e.g., proteins. A drop in the faradaic current of the redox probe accompanying protein adsorption originates from physical blocking of the electrode surface by their bulky nonconductive molecules.6 But both of these mechanisms seem to be invalid in case of electrochemical sensors based on conductive MIP films. In our previous studies, we demonstrated that a drop in the DPV current, caused by the appearance in a solution of an analyte, at conductive MIP film-coated electrodes might originate not from hindering the diffusion of the redox probe through the film but from changes in electrochemical properties of the film itself 7. Suppose the redox probe diffusion through the MIP film is not a decisive parameter for the faradaic current involving. Then, in the, e.g., DPV, determinations of electroinactive analytes at conductive MIP film-coated electrodes, this diffusion may be eliminated. For that the redox probe could be immobilized inside the MIP film matrix. Herein, we propose to deposit a self-reporting MIP film and apply it for fabrication of the selective electrochemical sensor determining the target analyte in the redox probe free test solutions. For that purpose, a ferrocene redox probe was covalently immobilized in a bis-bithiophene polymer molecularly imprinted with the p-synephrine template. Simultaneously, this polymer was deposited on the Pt electrode as a thin film. After the template extraction from the film, the analyte was determined with differential pulse voltammetry (DPV) in a redox probe free solution. That was possible because the internal ferrocene redox probe generated the DPV analytical signal. The thickness and morphology of the film were crucial for the sensor's performance. The mechanism of this redox self-reporting MIP film-based chemosensor was examined with electrochemical methods, simultaneous piezomicrogravimetry and electrochemistry at an electrochemical quartz crystal microbalance, and surface plasmon resonance spectroscopy. The devised chemosensor was applied for selective p-synephrine determination in a concentration range of 2.0 to 75 nM. References Cieplak, M.; Kutner, W., Artificial biosensors: How can molecular imprinting mimic biorecognition? Trends Biotechnol. 2016, 34 (11), 922-941. Uzun, L.; Turner, A. P. F., Molecularly-imprinted polymer sensors: realising their potential. Biosens. Bioelectron. 2016, 76, 131-144. Huynh, T.-P.; Sharma, P. S.; Sosnowska, M.; D'Souza, F.; Kutner, W., Functionalized polythiophenes: Recognition materials for chemosensors and biosensors of superior sensitivity, selectivity, and detectability. Prog. Polym. Sci. 2015, 47, 1-25. Yoshimi, Y.; Narimatsu, A.; Nakayama, K.; Sekine, S.; Hattori, K.; Sakai, K., Development of an enzyme-free glucose sensor using the gate effect of a molecularly imprinted polymer. J. Artif. Organs 2009, 12 (4), 264-270. Sharma, P. S.; Garcia-Cruz, A.; Cieplak, M.; Noworyta, K. R.; Kutner, W., 'Gate effect' in molecularly imprinted polymers: the current state of understanding. Curr. Opin. Electroche. 2019, 16, 50-56. Moreira, F. T. C.; Dutra, R. A. F.; Noronha, J. P. C.; Fernandes, J. C. S.; Sales, M. G. F., Novel biosensing device for point-of-care applications with plastic antibodies grown on Au-screen printed electrodes. Sens. Actuators, B 2013, 182, 733-740. Lach, P.; Cieplak, M.; Majewska, M.; Noworyta, K. R.; Sharma, P. S.; Kutner, W., "Gate Effect" in p-Synephrine Electrochemical Sensing with a Molecularly Imprinted Polymer and Redox Probes. Anal. Chem. 2019, 91 (12), 7546-7553. Figure 1

Nano Gold-Doped Molecularly Imprinted Polymer for Enhanced Electrochemical Detection of Hormone Cortisol

Introduction Insufficient or elevated hormone cortisol levels triggered by physical or psychological stress can cause several health problems, such as Addison's disease, Cushing's syndrome, and chronic fatigue syndrome. High serum cortisol levels are also related to increased mortality in COVID-19 patients. Thus, sensitive cortisol detection can provide an early indication for critical patients and monitor treatment efficacy. The physiological range of salivary cortisol fluctuates in a circadian rhythm between sub-nanomolar to nanomolar range. Late-night salivary cortisol concentration in the range of 2.76-166 nM was determined for clinically confirmed Cushing’s patients. A proper cortisol test requires mapping a patient’s cortisol levels over cycle of 24 hours. Most of the reported cortisol immunosensors involve biological receptors, such as antibodies, which are expensive, require refrigerated transportation and storage, and suffer from steric hindrance arising from antibody-small molecule interactions [1]. Cortisol immunoassays also suffer from a slow response (30 min to 5 hr) and cross-reactivity with structurally similar hormones, such as prednisolone and progesterone.Alternatively, the biorecognition can be realized using molecularly imprinted polymer (MIP), which provides artificial binding sites and cavities in polymer for target-specific binding. MIP holds numerous advantages over antibodies, including longer lifetimes, higher stability, and cost-effectiveness [2]. Yet, there remain several issues in the MIP-based biosensors. For instance, conventional particle-based MIP requires a time-consuming and tedious polymerization process. The coating of such MIP tends to result in an uncontrolled thickness, slow diffusion process for targets, and inefficient signal transduction and limited sensitivity. We overcome these shortcomings by creating controllable MIP thin films with target selective binding sites through electropolymerization. We also dope the MIP with nano gold to enhance the sensitivity of cortisol detection. Method The MIP was formed directly onto a gold nanoparticle-deposited glassy carbon electrode (GCE) through one-step voltammetric electropolymerization (inset to Figure 1a) with a mixture of o-phenylenediamine (o-PD) and HAuCl4 in the presence of cortisol template. Imprinted cortisol molecules were eluted by washing in an ethanol solution to create cortisol specific imprinting sites into the Au-poly-o-PD composite film. For the control experiment, a non-imprinted polymer (NIP) film was also prepared under the same process conditions in the absence of templates. We controlled the process conditions (e.g., the ratio of monomer/ HAuCl4/ template, number of polymerization cycles, pH, elution buffer, elution, and reaction time) to optimize the performance of the MIP sensor. The sensor's electrochemical responses were performed with cyclic voltammetry (CV) and square wave voltammetry (SWV). Results and Discussion The MIP film can be produced by electropolymerization within 20 min to achieve reproducible and controllable characteristics. During electropolymerization, AuNPs grow and anchor to the polymeric framework, possibly through the abundant amine groups on o-PD. This hybrid metal-polymer composite film could increase the electron transfer rate for the reaction with the redox reagents and thus enhance the sensitivity of cortisol detection. During electrodeposition, cortisol molecules were imprinted into composite film, which can be attributed to the H-bond between the hydroxyl groups on cortisol and amine groups on o-PD. The sensing mechanism relies on the change in redox current peak measured in the presence of the redox reagents, K3Fe(CN)6 and K4Fe(CN)6. The current decreases with the increase of the target cortisol binding on the MIP that hinders the redox reagents' access to the electrode. The CV curves in Figure 1a characterize the sensor electrode during MIP fabrication and cortisol sensing. The proposed sensor responds to cortisol detection within 8 min. The peak currents decrease with the increase in cortisol concentration (Figure 1b) due to the reduced number of imprinted cavities. The sensor exhibits a dynamic range of detection covering the physiological cortisol level from 10 pM to 100 nM with a detection limit of 1.5 pM, while the NIP shows negligible change under various cortisol concentrations (Figure 1c). Figure 1d shows that the cortisol MIP sensor also exhibits a highly selective detection against several structurally similar hormones, including estriol, estrone, progesterone, and β-estradiol. Conclusions We demonstrate nano gold-doped MIP electrode for sensitive, rapid, and selective detection of the hormone cortisol. The cost-effective, robust sensor provides an alternative to the conventional immunoassay and holds great potential for point-of-care cortisol detection.

Protein-imprinted polymer films prepared via cavity-selective multi-step post-imprinting modifications for highly selective protein recognition.

The use of molecularly imprinted polymers (MIPs) for achieving synthetic receptors capable of selective molecular recognition is promising; however, these polymers exhibit low selectivity derived from the heterogeneity of their created, imprinted cavities. To achieve highly selective protein recognition, we herein report the cavity-selective, multi-step, post-imprinting modification of MIPs. An MIP film for lysozyme was prepared by the copolymerization of {[2-(2-methacrylamido)ethyldithio]ethylcarbamoyl}methoxy acetic acid, a functional monomer possessing a modifiable disulfide bond, with acrylamide and N,N'-methylenebisacrylamide in the presence of lysozyme. After the removal of lysozyme, the disulfide bonds were cleaved by treatment with a reductant. A low concentration of lysozyme was then added to occupy the high-affinity cavities of the polymer and sterically protect the thiol groups within them. A poly(ethylene glycol)-based capping agent was reacted with the thiol groups residing in low-affinity cavities to hinder them. After the regeneration of the high-affinity cavities by washing out the bound lysozyme, the remaining thiol groups were reacted with 3-(2-pyridyldithio)propionic acid to introduce interacting groups, which produced capped MIPs. Comparing the capped and uncapped MIPs revealed that off-target protein binding was effectively suppressed by the capping treatment without any reduction in binding affinity (1.1 × 109M-1). Further investigation revealed that the lysozyme concentration during the capping process is critical for the selectivity of the capped MIP. In this case, highly selective MIPs were achieved when the lowest lysozyme concentration (100nM) was used. This facile process for creating highly selective, synthetic polymer receptors is a powerful approach for achieving plastic antibodies.

Molecularly imprinted polymer amalgamation on narrow-gapped Archimedean-spiral interdigitated electrodes: resistance to electrolyte fouling in acidic medium.

Aconventional photolithography technique was used to fabricate three types of Archimedean-spiral interdigitated electrodes (AIDEs) containing concentric interlocking electrodes with different electrode and gap sizes, i.e., 150μm (D1), 100μm (D2), and 50μm (D3). The precision of the fabrication was validated by surface topography using scanning electron microscopy, high power microscopy, 3D-nano profilometry, and atomic force microscopy. These AIDEs were fabricated with a tolerance of ± 6nm in dimensions. The insignificant current variation at thepico-ampere range for all bare AIDEs further proved the reproducibility of the device. The large gap sized AIDE (D1) is insensitive to acidic medium, whereas D2 and D3 are insensitive to alkali medium. D2 was the best with regard toits electrical characterization. Furthermore, uniformly synthesized molecularly imprinted polymer (MIP) nanoparticles prepared with human blood clotting factor IX and its aptamer were inthe size range 140 to 160nm, attached on the sensing surface and characterized. The average thickness of deposited MIP film was 1.7μm. EDX data shows the prominent peaks for silicon and aluminum substrates as 61.79 and 22.52%, respectively. The MIP nanoparticles-deposited sensor surface was characterized by applying it inelectrolyte solutions, and smooth curves with the current flow wereobserved at pH lower than 8 and discriminated against alkali media. Thisstudy provides a new MIP amalgamated AIDE with nano-gapped fingers enabling analysis of other biomaterials due to its operation in an ideal buffer range.

Detection of canine and equine procalcitonin for sepsis diagnosis in veterinary clinic by the development of novel MIP-based SPR biosensors

Procalcitonin (PCT) has emerged as a promising biomarker for the rapid identification of sepsis both in human and veterinary medicine. Nevertheless, the only analytical method currently available for the detection of PCT in veterinary species, is represented by immunoassays, useful only for research purposes. In this work, we report the development of two biosensors which utilize molecularly imprinted polymers (MIPs) for the detection of canine and equine PCT. Dopamine (DA) and norepinephrine (NE) were used as monomers for the synthesis of the MIP films on surface plasmon resonance (SPR) gold chips and the imprinting efficiency of canine and equine PCT in terms of binding affinity toward the analyte, selectivity, and sensitivity were compared. After optimization in buffer conditions, PCTs calibration was successfully achieved also in animal plasma, with good specificity and reproducibility. More effective protein binding and imprinting was obtained with polynorepinephrine (PNE) for both PCTs, and the SPR biosensors were able to detect the biomarkers in plasma with a LOD of 15 ng mL−1 and 30 ng mL−1 respectively for equine and canine PCT.

Cobalt(II)-ion-exchanged Zn-bio-MOF-1 derived CoS/ZnS composites modified electrochemical sensor for chloroneb detection by differential pulse voltammetry.

For the first time CoS-nanoparticles attached ZnS rods (CoS/ZnS composites) have been synthesizedusing cobalt(II)-ion-exchanged zinc-based biological metal-organic framework-1 (Zn-bio-MOF-1) as precursors by a solvothermal method. Among them, the cobalt(II)-ion-exchanged Zn-bio-MOF-1 was obtained by exchanging the dimethylammonium cations (Me2NH2+) of Zn-bio-MOF-1 with cobalt ions. A novel electrochemical sensor based on CoS/ZnS composites and molecularly imprinted polymers (MIPs) was proposed for rapid, sensitive, and highly selective detection of organochlorine pesticide chloroneb. The MIP film was obtained by cyclic voltammetry (CV), and differential pulse voltammetry (DPV) was used to detect chloroneb. Under the optimal conditions, the oxidation peak current density of chloroneb was linearly related to the concentration from 0.003 to 0.2μM and 0.2 to 3.2μM with a detection limit of 0.87nM (S/N = 3) and a sensitivity of 52.27 μA·μM-1·cm-2. The proposed sensor exhibits a favorable selectivity, stability, and reproducibility, and was applied to detect chloroneb residues in licorice, cucumber, river water, and soil samples with satisfactory results.Graphical abstract.

SPR-Optical Fiber-Molecularly Imprinted Polymer Sensor for the Detection of Furfural in Wine.

A surface plasmon resonance (SPR) platform, based on a D-shaped plastic optical fiber (POF), combined with a biomimetic receptor, i.e., a molecularly imprinted polymer (MIP), is proposed to detect furfural (2-furaldheide, 2-FAL) in fermented beverages like wine. MIPs have been demonstrated to be a very convenient biomimetic receptor in the proposed sensing device, being easy and rapid to develop, suitable for on-site determinations at low concentrations, and cheap. Moreover, the MIP film thickness can be changed to modulate the sensing parameters. The possibility of performing single drop measurements is a further favorable aspect for practical applications. For example, the use of an SPR-MIP sensor for the analysis of 2-FAL in a real life matrix such as wine is proposed, obtaining a low detection limit of 0.004 mg L−1. The determination of 2-FAL in fermented beverages is becoming a crucial task, mainly for the effects of the furanic compounds on the flavor of food and their toxic and carcinogenic effect on human beings.

Improving Surface Imprinting Effect by Reducing Nonspecific Adsorption on Non-Imprinted Polymer Films for 2,4-D Herbicide Sensors

Surface imprinting used for template recognition in nanocavities can be controlled and improved by surface morphological changes. Generally, the lithographic technique is used for surface patterning concerning sensing signal amplification in molecularly imprinted polymer (MIP) thin films. In this paper, we describe the effects of silanized silica molds on sensing the properties of MIP films. Porous imprinted poly(MAA–co–EGDMA) films were lithographically fabricated using silanized or non-treated normal silica replica molds to detect 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide as the standard template. The silanized mold MIP film (st-MIP) (Δf = −1021 Hz) exhibited a better sensing response than the non-treated normal MIP (n-MIP) (Δf = −978 Hz) because the imprinting effects, which occurred via functional groups on the silica surface, could be reduced through silane modification. Particularly, two non-imprinted (NIP) films (st-NIP and n-NIP) exhibited significantly different sensing responses. The st-NIP (Δfst-NIP = −332 Hz) films exhibited lower Δf values than the n-NIP film (Δfn-NIP = −610 Hz) owing to the remarkably reduced functionality against nonspecific adsorption. This phenomenon led to different imprinting factor (IF) values for the two MIP films (IFst-MIP = 3.38 and IFn-MIP = 1.86), which was calculated from the adsorbed 2,4-D mass per poly(MAA–co–EGDMA) unit weight (i.e., QMIP/QNIP). Moreover, it was found that the st-MIP film had better selectivity than the n-MIP film based on the sensing response of analogous herbicide solutions. As a result, it was revealed that the patterned molds’ chemical surface modification, which controls the surface functionality of imprinted films during photopolymerization, plays a role in fabricating enhanced sensing properties in patterned MIP films.

Enabling the Selective Detection of Endocrine-Disrupting Chemicals via Molecularly Surface-Imprinted "Coffee Rings".

Molecularly imprinted polymers (MIPs) represent an intriguing class of synthetic materials that can selectively recognize and bind chemical or biological molecules in a variety of value-added applications in sensors, catalysis, drug delivery, antibodies, and receptors. In this context, many advanced methods of implementing functional MIP materials have been actively studied. Herein, we report a robust strategy to produce highly ordered arrays of surface-imprinted polymer patterns with unprecedented regularity for MIP-based sensor platform, which involves the controlled evaporative self-assembly process of MIP precursor solution in a confined geometry consisting of a spherical lens on a flat Si substrate (i.e., sphere-on-flat geometry) to synergistically utilize the "coffee-ring" effect and repetitive stick-slip motions of the three-phase contact line simply by solvent evaporation. Highly ordered arrays of the ring-patterned MIP films are then polymerized under UV irradiation to achieve semi-interpenetrating polymer networks. The extraction of templated target molecules from the surface-imprinted ring-patterned MIP films leaves behind copious cavities for the recognizable specific "memory sites" to efficiently detect small molecules. As a result, the elaborated surface structuring effect, sensitivity, and specific selectivity of the coffee-ring-based MIP sensors are scrutinized by capitalizing on an endocrine-disrupting chemical, 2,4-dichlorophenoxyacetic acid (2,4-D), as an example. Clearly, the evaporative self-assembly of nonvolatile solutes in a confined geometry renders the creation of familiar yet ordered coffee-ring-like patterns for a wide range of applications, including sensors, scaffolds for cell motility, templates, substrates for neuron guidance, etc., thereby dispensing with the need of multistep lithography techniques and external fields.

Innovative screen-printed electrodes on cork composite substrates applied to sulfadiazine electrochemical sensing

Abstract This work reports the first use of cork as substrate to produce 3-electrode electrochemical devices, which may be very important to conduct sustainable worldwide biochemical testing in point-of-care. It consists of laminated cork covered by a thin-film of an insulating resin and printed in a 3-electrode system format. Silver ink was used to print electrical tracks and the reference electrode, while carbon ink was used to print working and auxiliary electrodes. The analytical performance of the cork-based devices was and compared to other common supports, as PET and ceramics in the form of screen-printed electrodes (SPEs). The cork-based devices displayed higher current values and better reversibility features and were able to undergo stable modification with conductive nanomaterials. They were further applied to detect sulfadiazine (SDZ), an antibiotic of human use that is also an environmental contaminant, by modifying the working electrode with a molecularly imprinted polymer (MIP) layer obtained by electropolymerization of pyrrol. The results confirmed the ability of the MIP film to detect SDZ selectively and showed reproducible increasing current signals for increasing concentrations of SDZ, from 8.0 to 186.0 μM. Direct comparison with commercial carbon SPEs showed greater sensitivity for the cork-based SPEs, with 10× lower limits of detection. Overall, cork-based devices are a valuable alternative to currently available SPEs systems, considering environment and cost features and also the analytical gains of this approach. These are especially important in times where a global biochemical testing became necessary for improved public health management.

A Molecularly Imprinted Electrochemical Luminescence Sensor for Detection of Gibberellin Based on Energy Transfer

A molecularly imprinted sensor was fabricated, and a method of enhancing the electrochemiluminescence (ECL) signal of Ru(bpy) 3 Cl 2 using resonance energy transfer (RET) method was established for ultra-sensitive determination of gibberellin (GA3). Au-doped g-C 3 N 4 (g-C 3 N 4 /Au) material was prepared on the surface of glassy carbon electrode (GCE), and then o -phenylenediamine was electropolymerized to achieve a molecularly imprinted polymer (MIP) film. Elution was performed with a methanol-acetic acid eluent to obtain a cavity that specifically recognized GA3. In the experiment, Ru(bpy) 3 2+ was used as the probe and g-C 3 N 4 /Au was used as the energy donor. The RET between Ru(bpy) 3 2+ and g-C 3 N 4 /Au was used to enhance the ECL intensity of Ru(bpy) 3 2+ . In addition, ECL-RET was combined with molecular imprinting technology to improve the selectivity of the sensor. With the increase of the concentration of GA3 in the sample, the molecularly imprinted cavities recombined with GA3 which made the ECL intensity gradually decrease. Under the optimized conditions, it was found that the there was a linear relationship between ECL intensities and the GA3 concentrations in the range of 4.00 × 10 −14 − 7.00 × 10 −11 mol/L, and the detection limit was 1.64 × 10 –14 mol/L (DL = 3 S / K ). The sensor was successfully applied to the detection of GA3 in beer, and the recoveries were 95.7%–103.7%. A molecularly imprinted sensor was fabricated for gibberellin (GA3) determination by electrochemiluminescence resonance energy transfer (ECL-RET) method. g-C 3 N 4 /Au was modified on a glassy carbon electrode, and then a MIP film was synthesized on its surface. The ECL signal of Ru(bpy) 3 Cl 2 probe was enhanced significantly by ECL-RET system, by which the g-C 3 N 4 /Au donor transferred energy to the Ru(bpy) 3 Cl 2 acceptor. High sensitivity was achieved for GA3 detection with a detection limit of 1.64 × 10 -14 mol/L.

Non-enzymatic lactose molecularly imprinted sensor based on disposable graphite paper electrode

Lactose (LAC) is a disaccharide - major sugar, present in milk and dairy products. LAC content is an important indicator of milk quality and abnormalities in food industries, as well as in human and animal health. The present study reports the development of an innovative imprinted voltammetric sensor for sensitive detection of LAC. The sensor was constructed using electropolymerized pyrrole (Py) molecularly imprinted polymer (MIP) on graphite paper electrode (PE). The MIP film was constructed through the electrosynthesis of polypyrrole (PPy) in the presence of LAC (template molecule) on PE (PPy/PE). To optimize the detection conditions, several factors affecting the PPy/PE sensor performance were assessed by multivariate methods (Plackett–Burman design and central composite design). Under optimized conditions, the proposed analytical method was applied for LAC detection in whole and LAC-free milks, where it demonstrated high sensitivity and selectivity, with two dynamic linear ranges of concentration (1.0–10 nmol L−1 and 25–125 nmol L−1) and a detection limit of 0.88 nmol L−1. The MIP sensor showed selective molecular recognition for LAC in the presence of structurally related molecules. The proposed PPy/PE sensor exhibited good stability, as well as excellent reproducibility and repeatability. Based on the results obtained, the PPy/PE is found to be highly promising for sensitive detection of LAC.