Smart dual imprinted Origami 3D-ePAD for selective and simultaneous analysis of vanillylmandelic acid and 5-hydroxyindole-3-acetic acid carcinoid cancer biomarkers using graphene quantum dots coated with dual molecularly imprinted polymers.

Measuring the levels of the biomarkers vanillylmandelic acid (VMA) and 5-Hydroxyindole-3-acetic acid (5-HIAA) is a valuable tool for clinical diagnosis not only of neuroblastoma or carcinoid syndrome, but also of essential hypertension, depression, migraine, and Tourette's syndrome. Herein, we explore using graphene quantum dots (GQDs) coated with molecularly imprinted polymer (MIP) as novel dual-imprinted sensors for selective and simultaneous determination of VMA and 5-HIAA in urine and plasma samples. The dual-MIP was successfully coated on the GQDs core via co-polymerization of (3-aminopropyl) triethoxysilane (APTES) and tetraethyl orthosilicate (TEOS), acting as functional and cross-linking monomers, respectively. In addition, we successfully created the dual imprinted VMA and 5-HIAA shell on the GQDs' core via a one-pot synthesis. We fabricated a facile and ready-to-use Origami three-dimensional electrochemical paper-based analytical device (Origami 3D-ePAD) for simultaneous determination of VMA and 5-HIAA using a GQDs@dual-MIP modified graphene electrode (GQDs@dual-MIP/SPGE). The Origami 3D-ePAD was designed to form a voltammetric cell on a three-layer foldable sheet with several advantages. For example, they were quickly assembled and enhanced the device's physical durability with the hydrophobic backup sheet. The developed dual imprinted Origami 3D-ePAD leads to substantially enhanced sensitivity and selectivity to electrochemical signal amplification generated from increasing the electrode-specific surface area, electrocatalytic activity, and the large numbers of dual imprinted sites for VMA and 5-HIAA detection. The synthetic recognition sites are highly selective for 5-HIAA and VMA molecules with an imprinting factor of 8.46 and 7.10, respectively. Quantitative analysis relying on square wave voltammetry reveals excellent linear dynamic ranges of around 0.001-25 µM, with detection limits of 0.023 nM for 5-HIAA and 0.047 nM for VMA (3Sb, n = 3). The Origami 3D-ePAD provides high accuracy and precision (i.e., recovery values of 5-HIAA ranged from 82.98 to 98.40 %, and VMA ranged from 83.28 to 104.39 %), and RSD less than 4.37 %) in urine and plasma samples without any evidence of interference. Hence, it is well suited as a facile and ready-to-use disposable device for point-of-care testing. It is straightforward, cost-effective, reproducible, and stable. Furthermore, it allows for rapid analysis (analysis time ∼20s) useful in medical diagnosis and other relevant fields.

Molecularly Imprinted Nanoparticle Ensembles for Rapidly Identifying S. epidermidis.

Staphylococcus epidermidis (S. epidermidis) belongs to methicillin-resistant bacteria strains that cause severe disease in humans. Herein, molecularly imprinted polymer (MIP) nanoparticles resulting from solid-phase synthesis on entire cells were employed as a sensing material to identify the species. MIP nanoparticles revealed spherical shapes with diameters of approximately 70 nm to 200 nm in scanning electron microscopy (SEM), which atomic force microscopy (AFM) confirmed. The interaction between nanoparticles and bacteria was assessed using height image analysis in AFM. Selective binding between MIP nanoparticles and S. epidermidis leads to uneven surfaces on bacteria. The surface roughness of S. epidermidis cells was increased to approximately 6.3 ± 1.2 nm after binding to MIP nanoparticles from around 1 nm in the case of native cells. This binding behavior is selective: when exposing Escherichia coli and Bacillus subtilis to the same MIP nanoparticle solutions, one cannot observe binding. Fluorescence microscopy confirms both sensitivity and selectivity. Hence, the developed MIP nanoparticles are a promising approach to identify (pathogenic) bacteria species.

Lightning Strike Protection: Current Challenges and Future Possibilities.

An airplane is statistically struck by lightning every year. The need for lightweight aircraft to reduce the production of carbon dioxide has significantly reduced the presence of metals in favour of composites, resulting in lower lightning strike protection efficiency. In this perspective, we critically review the state of technologies in lightning strike protection solutions based on carbon materials, graphene, and MXenes. Furthermore, we comment on possible future research directions in the field.

A simple aptamer/gold nanoparticle aggregation-based colorimetric assay for oxidized low-density lipoprotein determination.

Oxidized low-density lipoprotein (oxLDL) is the leading cause of atherosclerosis and cardiovascular diseases. Here, we created a simple colorimetric assay for sensitive and specific determination of oxLDL using a selective aptamer coupled with salt-induced gold nanoparticle (AuNP) aggregation. The aptamer was chosen by Systematic Evolution of Ligands by Exponential Enrichment to obtain a novel selective sequence towards oxLDL (as 5'-CCATCACGGGGCAGGCGGACAAGGGGTAAGGGCCACATCA-3'). Mixing a 5 µM aptamer solution with an aliquot of a sample containing oxLDL followed by adding AuNP solution (OD = 1) and 80 mmol L-1 NaCl achieved rapid results within 19 min: linear response to oxLDL from 0.002 to 0.5 µmol L-1 with high selectivity, a recovery accuracy of 100-111% at the 95% confidence interval, and within-run and between-run precision of 1-6% and 1-5% coefficient variations, respectively. Artificial serum diluted at least 1:8 with distilled water, analyzed by the aptamer-based colorimetric assay, showed excellent correlation with conventional thiobarbituric acid reactive substances (TBARS) (R2 = 0.9792) as a rapid colorimetric method without the need for sample preparation other than dilution.

Origami 3D-microfluidic paper-based analytical device for detecting carbaryl using mesoporous silica-platinum nanoparticles with a molecularly imprinted polymer shell.

Herein, we present a novel Origami 3D-µPAD for colorimetric carbaryl detection using a super-efficient catalyst, namely mesoporous silica-platinum nanoparticles coated with a molecularly imprinted polymer (MSN-PtNPs@MIP). Morphological and structural characterization reveals that coating MIP on the MSN-PtNPs surface significantly increases the selective area, leading to larger numbers of imprinting sites for improved sensitivity and selectivity in determining carbaryl. The as-prepared MSN-PtNPs@MIP was used for catalytic oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2. Carbaryl selectively binds to the cavities embedded on the MSN-PtNPs surface and subsequently inhibits TMB oxidation leading the color to change to light blue. The change of reaction color from dark blue to light blue depends on the concentration of carbaryl within the 3D-µPAD detection zone. This design integrates the advantages of highly efficient sample delivery through micro channels (top layer) and efficient partition/separation paths (bottom layer) of the cellulose substrate to achieve both improved detection sensitivity and selectivity. Assay on the Origami 3D-µPAD can determine carbaryl by ImageJ detection, over a dynamic range of 0.002-20.00 mg kg-1, with a very low limit of detection at 1.5 ng g-1. The developed 3D-µPAD exhibit high accuracy when applied to detect carbaryl in fruits, with satisfactory recoveries from 90.1% to 104.0% and relative differences from the reference HPLC values less than 5.0%. Furthermore, the fabricated Origami 3D-µPAD provides reliable durability and good reproducibility (3.19% RSD for fifteen devices).

Facile and Compact Electrochemical Paper-Based Analytical Device for Point-of-Care Diagnostic of Dual Carcinogen Oxidative Stress Biomarkers through a Molecularly Imprinted Polymer Coated on Graphene Quantum-Dot Capped Gold.

Nanoscale imprinting significantly increases the specific surface area and recognition capabilities of a molecularly imprinted polymer by improving accessibility to analytes, binding kinetics, and template removal. Herein, we present a novel synthetic route for a dual molecularly imprinted polymer (dual-MIP) of the carcinogen oxidative stress biomarkers 3-nitrotyrosine (3-NT) and 4-nitroquinolin-N-oxide (4-NQO) as coatings on graphene quantum-dot capped gold nanoparticles (GQDs-AuNPs). The dual-MIP was successfully coated on the GQDs-AuNPs core via a (3-mercaptopropyl) trimethoxysilane (MPTMS) linkage and copolymerization with the 3-aminopropyltriethoxysilane (APTMS) functional monomer. In addition, we fabricated a facile and compact three-dimensional electrochemical paper-based analytical device (3D-ePAD) for the simultaneous determination of the dual biomarkers using a GQDs-AuNPs@dual-MIP-modified graphene electrode (GQDs-AuNPs@dual-MIP/SPGE). The developed dual-MIP device provides greatly enhanced electrochemical signal amplification due to the improved electrode-specific surface area, electrocatalytic activity, and the inclusion of large numbers of dual-imprinted sites for 3-NT and 4-NQO detection. Quantitative analysis used square wave voltammetry, with an oxidation current appearing at -0.10 V for 4-NQO and +0.78 V for 3-NT. The dual-MIP sensor revealed excellent linear dynamic ranges of 0.01 to 500 µM for 3-NT and 0.005 to 250 µM for 4-NQO, with detection limits in nanomolar levels for both biomarkers. Furthermore, the dual-MIP sensor for the simultaneous determination of 3-NT and 4-NQO provides high accuracy and precision, with no evidence of interference from urine, serum, or whole blood samples.

Development of Colorimetric Reverse Transcription Loop-Mediated Isothermal Amplification Assay for Detecting Feline Coronavirus.

Feline infectious peritonitis (FIP) is a worldwide fatal disease caused by a mutant feline coronavirus (FCoV). Simple and efficient molecular detection methods are needed. Here, sensitive, specific, rapid, and reliable colorimetric reverse transcription loop-mediated isothermal amplification (RT-LAMP) was developed to detect the ORF1a/1b gene of FCoV from cats with suspected FIP using neutral red as an indicator. Novel LAMP primers were specifically designed based on the gene of interest. The isothermal assay could visually detect FCoV at 58 °C for 50 min. The RT-LAMP assay was highly specific and had no cross-reactivity with other related feline viruses. The detection limit of FCoV detection by RT-LAMP was 20 fg/µL. A blind clinical test (n = 81) of the developed RT-LAMP procedure was in good agreement with the conventional PCR method. In the light of its performance specificity, sensitivity, and easy visualization, this neutral-red-based RT-LAMP approach would be a fruitful alternative molecular diagnostic tool for veterinary inspection of FCoV when combined with nucleotide sequencing or specific PCR to affirm the highly virulent FIP-associated FCoV.

Development and Up-Scaling of Electrochemical Production and Mild Thermal Reduction of Graphene Oxide.

To reduce the global emissions of CO2, the aviation industry largely relies on new light weight materials, which require multifunctional coatings. Graphene and its derivatives are particularly promising for combining light weight applications with functional coatings. Although they have proven to have outstanding properties, graphene and its precursor graphene oxide (GO) remain far from application at the industrial scale since a comprehensive protocol for mass production is still lacking. In this work, we develop and systematically describe a sustainable up-scaling process for the production of GO based on a three-step electrochemical exfoliation method. Surface characterization techniques (XRD, XPS and Raman) allow the understanding of the fast exfoliation rates obtained, and of high conductivities that are up to four orders of magnitude higher compared to GO produced via the commonly used modified Hummers method. Furthermore, we show that a newly developed mild thermal reduction at 250 °C is sufficient to increase conductivity by another order of magnitude, while limiting energy requirements. The proposed GO powder protocol suggests an up-scaling linear relation between the amount of educt surface and volume of electrolyte. This may support the mass production of GO-based coatings for the aviation industry, and address challenges such as low weight, fire, de-icing and lightning strike protection.

Raman and scanning probe microscopy for differentiating surface imprints of E. coli and B. cereus.

Molecularly imprinted polymers (MIPs) are artificial recognition materials mimicking biological recognition entities such as antibodies. The general model of imprinting assumes that functional monomers interact with functional groups present on the target species which leads to cavities complementing the template in surface chemistry and shape thus ensuring recognition. However, to date there is little independent experimental evidence supporting that the surface chemistry in the imprints is tailored to analyte recognition and thus differs from the surface chemistry of the surrounding polymer. Herein, we investigate such chemical differences between imprints of Escherichia coli and Bacillus cereus in poly(styrene-co-DVB) and a commercial acrylate-based polymer by the means of confocal Raman microscopy and PLS-DA. The MIPs were generated using a stamping approach. Peak-force QNM measurements were conducted to rule out residues of bacterial cells in the imprints. While imprints of E. coli and B. cereus could be distinguished based on their Raman spectra in the acrylate-based polymer, differentiation in poly(styrene-co-DVB) was not significant. This could be a result of a higher potential of acrylate functional groups for interacting with lipopolysaccharides and peptidoglycans on bacteria surfaces compared to the phenyl groups of poly(styrene-co-DVB) and emphasizes the importance of the right choice of functional monomers for a specific target analyte.

Investigations on sub-structures within cavities of surface imprinted polymers using AFM and PF-QNM.

Investigations on lithographically formed cavities of surface-imprinted polymers (SIP) can help to gain deeper understanding on cell recognition with SIPs: it is known that surface topography and biomolecules transferred during surface imprinting contribute to cell adhesion. In this work, SIPs synthesized via two different imprinting techniques, namely stamp imprinting and polymerization of Pickering emulsions, were investigated and compared to each other, using atomic force microscopy (AFM) and Peak Force Quantitative Nano Mechanics (PF-QNM). We focused on SIPs based on poly(styrene-co-divinylbenzene) as model polymer and E. coli as model template for cell imprinting. Both imprinting approaches led to cavities that revealed nanostructures within the imprints. Stamp imprinting cavities feature low surface roughness and channel structures that resemble the negative pattern of the bacteria on the stamp and their filaments, while SIPs synthesized via polymerization of Pickering emulsions reveal globular nanostructures accumulating in the imprints. AFM phase imaging and adhesion mapping using PF-QNM show that these globular structures are remainders of the imprinted E. coli cells, most likely lipopolysaccarides, which is not observable in imprints resulting from stamp imprinting.

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.

Smart sensor for assessment of oxidative/nitrative stress biomarkers using a dual-imprinted electrochemical paper-based analytical device.

We present a novel dual-imprinted electrochemical paper-based analytical device (Di-ePAD) to simultaneously determine 8-hydroxy-2'-deoxyguanosine (8-OHdG) and 3-nitrotyrosine (3-NT) and assess oxidative and nitrative biomarkers in urine and plasma samples. The Di-ePAD was designed with hydrophobic barrier layers formed on filter paper to provide three-dimensional circular reservoirs and assembled electrodes. The molecularly imprinted polymer (MIP) was synthesized using a silica nanosphere decorated with silver nanoparticles (SiO2@AgNPs) as a core covered with dual-analyte imprinted sites on the polymer to recognize selectively and bind the target biomarkers. This strategy drives monodispersity and enhances the conductivity of the resulting MIP core-shell products. 3-NT-MIP and 8-OHdG-MIP were synthesized by successively coating the surface of SiO2@AgNPs with l-Cysteine via the thiol group, then terminating with MIP shells. The dual imprinted core-shell composites possess attractive properties for the target biomarkers' sensing, including catalytic activity, selectivity, and good conductivity. The Di-ePAD revealed excellent linear dynamic ranges of 0.01-500 µM for 3-NT and 0.05-500 µM for 8-OHdG, with detection limits of 0.0027 µM for 3-NT and 0.0138 µM for 8-OHdG. This newly developed method based on the synergistic effects of SiO2@AgNPs combined with promising properties of MIP offers outstanding selectivity, sensitivity, reproducibility, simplicity, and low cost for quantitative analysis of 3-NT and 8-OHdG. The proposed Di-ePAD showed good accuracy and precision when applied to actual samples, including urine and serum samples validated by a conventional HPLC method.

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.

In-Situ Monitoring of Real-Time Loop-Mediated Isothermal Amplification with QCM: Detecting Listeria monocytogenes.

Functionalized DNA sequences are promising sensing elements to combine with transducers for bio-sensing specific target microbes. As an application example, this paper demonstrates in situ detection of loop-mediated isothermal amplification products by hybridizing them with thiolated-ssDNA covalently anchored on the electrodes of a quartz crystal microbalance (QCM). Such hybridization leads to a frequency signal, which is suitable for monitoring real-time LAMP amplification based on mass-sensing: it detects interactions between the complementary nucleobases of LAMP products in solution and the thiolated-ssDNA probe sequence on the gold surface. Target DNA LAMP products cause irreversible frequency shifts on the QCM surfaces during hybridization in the kHz range, which result from both changes in mass and charge on the electrode surface. In order to confirm the LAMP assay working in the QCM sensing system at elevated temperature, the sky blue of positive LAMP products solution was achieved by using the Hydroxy Naphthol Blue (HNB) and agarose gel electrophoresis. Since on-QCM sensing of DNA hybridization leads to irreversible sensor responses, this work shows characterization by X-ray photoelectron spectroscopy (XPS) core spectra of S2p, N1s, Mg1s, P2p and C1s. XPS results confirmed that indeed both DNA and by-products of LAMP attached to the surface. Listeria monocytogenes DNA served to study in-situ detection of amplified LAMP products on DNA-functionalized surfaces.

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.

Thin Film Plastic Antibody-Based Microplate Assay for Human Serum Albumin Determination.

Herein we demonstrate molecularly imprinted polymers (MIP) as plastic antibodies for a microplate-based assay. As the most abundant plasma protein, human serum albumin (HSA) was selected as the target analyte model. Thin film MIP was synthesized by the surface molecular imprinting approach using HSA as the template. The optimized polymer consisted of acrylic acid (AA) and N-vinylpyrrolidone (VP) in a 2:3 (w/w) ratio, crosslinked with N,N'-(1,2-dihydroxyethylene) bisacrylamide (DHEBA) and then coated on the microplate well. The binding of MIP toward the bound HSA was achieved via the Bradford reaction. The assay revealed a dynamic detection range toward HSA standards in the clinically relevant 1-10 g/dL range, with a 0.01 g/dL detection limit. HSA-MIP showed minimal interference from other serum protein components: γ-globulin had 11% of the HSA response, α-globulin of high-density lipoprotein had 9%, and ß-globulin of low-density lipoprotein had 7%. The analytical accuracy of the assay was 89-106% at the 95% confidence interval, with precision at 4-9%. The MIP-coated microplate was stored for 2 months at room temperature without losing its binding ability. The results suggest that the thin film plastic antibody system can be successfully applied to analytical/pseudoimmunological HSA determinations in clinical applications.

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.

Direct assessment of very-low-density lipoprotein by mass sensitive sensor with molecularly imprinted polymers.

Very-low-density lipoprotein (VLDL) contributes to the buildup of atherosclerotic plaque in the arteries and can lead to coronary heart disease. In clinical laboratory testing, the cholesterol content of VLDL (VLDL-C) cannot be assessed directly by the enzymatic colorimetric assay as it can for other lipoproteins, due to lack of a specific sample pretreatment technique. VLDL concentration relies on analyzing the endogenous triglycerides (TGs) bound in its particles and then converting to the VLDL-C estimate TGs/5. This estimation is valid for at least 12 h-fasted serum when exogenous TGs attached to chylomicrons (CMs) have been cleared from the circulation. A quartz crystal microbalance (QCM)-based sensor was generated using biomimetic sensing elements as a molecularly imprinted polymer (MIP) to directly measure actual VLDL. A novel VLDL-MIP was synthesized using methacrylic acid (MAA) and N-vinylpyrrolidone (VP) in the ratio 1:1 (v/v) as functional monomers in the presence of N, N'-(1,2-dihydroxyethylene) bis(acrylamide) (DHEBA) as a crosslinking agent. The VLDL-MIP sensor showed high sensitivity with a linear response from 2.5 mg dL-1 to 100 mg dL-1 of VLDL-C with a limit of detection at 1.5 mg dL-1. Recoveries of 96-103% were achieved when the VLDL-MIP sensor was used for VLDL assessment at 38-71 mg dL-1 concentrations. Repeatability and reproducibility of the sensor were very good with coefficients of variation at 1.63-4.74% and 4.25-9.04%, respectively. The sensor demonstrated low cross-reactivity with other lipoproteins; 6-7% of low-density lipoprotein (LDL) signals, 2-4% high-density lipoprotein (HDL), and 1% CMs compared to the signal of VLDL. Sensor results for 12 h-fasted serum and non-fasted serum correlated well with VLDL estimates TGs/5, with coefficients of determination (R2) at 0.9967 and 0.9932, respectively. This new sensor offers a new strategy for direct VLDL assessment from non-fasted serum without other sample pretreatment steps than dilution.

Real-Time Water Quality Monitoring with Chemical Sensors.

Water quality is one of the most critical indicators of environmental pollution and it affects all of us. Water contamination can be accidental or intentional and the consequences are drastic unless the appropriate measures are adopted on the spot. This review provides a critical assessment of the applicability of various technologies for real-time water quality monitoring, focusing on those that have been reportedly tested in real-life scenarios. Specifically, the performance of sensors based on molecularly imprinted polymers is evaluated in detail, also giving insights into their principle of operation, stability in real on-site applications and mass production options. Such characteristics as sensing range and limit of detection are given for the most promising systems, that were verified outside of laboratory conditions. Then, novel trends of using microwave spectroscopy and chemical materials integration for achieving a higher sensitivity to and selectivity of pollutants in water are described.

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.