A poly(arylene ethynylene)-based microfluidic fluorescence sensor array for discrimination of polycyclic aromatic hydrocarbons.

Polycyclic aromatic hydrocarbons (PAHs) are persistent contaminants in the environment. Several of them have carcinogenic properties. There is considerable interest in their sensitive low-cost detection and monitoring. We present a simple paper-based microfluidic sensor for the rapid detection of PAHs. Craft punch patterning generated multiple detection zones inhabited by fluorescent poly(arylene ethynylene)s (PAEs). Changes in fluorescence image and/or intensity of the sensor array were recorded using a smartphone camera. The RGB color values of the photographed images were extracted through ImageJ software. 10 different PAHs were correctly identified using Principal Component Analysis and discrimination analysis (PCA-DA). 100% classification accuracy was achieved for model training, whereas validating the PCA-DA model by cross-validation resulted in 93% classification accuracy for 5.0 mg L-1 analyte.

Fluorescent Carbon Dots Prepared from Hazelnut Kohl as an Affordable Probe for Determination of Dopamine.

In this investigation, a simple, green and facile fluorescence mrtod using carbon dots (CDs) of hazelnut kohl is described for selective detection of dopamine (DA). The sensing system is based on hazelnut kohl (the black soot of kohl) which is used as a carbon source. Generally, kohl is a traditional eye cosmetic that used in different parts of the world and synthesized by the combustion process like burning natural materials. Here, it has been proven that black soot (kohl) obtained from hazelnut has a carbon dot structure and can be used for sensory applications. Some characterization methods are carried out to reveal the kohl structure. Also, the photoluminescence properties of the prepared CDs of kohl are investigated. It is found that the size of CDs is 2-4 nm. Besides, under the optimal conditions, the fluorescence of CDs is used for DA determination. CDs fluorescence intensity is decreased linearly with the increase of DA concentration. By using the fluorescence dependency toward the DA concentration, DA can be determined in the range 0.5-30 µM with the limit of detection of 0.30 µM. Finally, this method is successfully applied to discriminate the DA in the real samples (healthy human serum and cerebrospinal fluid (CSF)) which shows acceptable efficiently for diagnostic purposes. The fluorescence of carbon dots, prepared from Hazelnut Kohl, is quenched in the presence of dopamine.

Evaluation of adulteration in distillate samples of Rosa damascena Mill using colorimetric sensor arrays, chemometric tools and dispersive liquid-liquid microextraction-GC-MS.

INTRODUCTION: Rosa damascena Mill distillate and its essential oil are widely used in cosmetics, perfumes and food industries. Therefore, the methods of detection for its authentication is an important issue. OBJECTIVES: We suggest colorimetric sensor array and chemometric methods to discriminate natural Rosa distillate from synthetic adulterates. MATERIAL AND METHODS: The colour responses of 20 indicators spotted on polyvinylidene fluoride (PVDF) substrate were monitored with a flatbed scanner; then their digital representation was analysed with principal component analysis (PCA), partial least squares-discriminant analysis (PLS-DA) and soft independent modelling of class analogy (SIMCA). RESULTS: Accurate discrimination of the diluted- and synthetic-mixture samples from the original ones was achieved by PLS-DA and SIMCA models with error rate of 0.01 and 0, specificity of 0.98 and 1, sensitivity of 1 and 1, and accuracy of 0.98 and 0.96, respectively. Discrimination of the synthetic adulterate from the original samples was achieved with error rate of 0.03 and 0.03, specificity of 0.94 and 0.93, sensitivity of 1 and 1, and accuracy of 0.93 and 0.71 with PLS-DA and SIMCA models, respectively. Moreover, the chemical constituents of the samples were analysed using dispersive liquid-liquid microextraction and gas chromatography-mass spectrometry (GC-MS). The main constituents of the distillate were geraniol, citronellol, and phenylethyl alcohol in different percentages, in both original and synthetic adulterate samples. CONCLUSION: These results point out the successful combination of colorimetric sensor array and PLS-DA and SIMCA as a fast, sensitive and inexpensive screening tool for discrimination of original samples of R. damascena Mill distillate from those prepared from synthetic Rosa essential oils.

Accessory mutations balance the marginal stability of the HIV-1 protease in drug resistance.

The HIV-1 protease is a major target of inhibitor drugs in AIDS therapies. The therapies are impaired by mutations of the HIV-1 protease that can lead to resistance to protease inhibitors. These mutations are classified into major mutations, which usually occur first and clearly reduce the susceptibility to protease inhibitors, and minor, accessory mutations that occur later and individually do not substantially affect the susceptibility to inhibitors. Major mutations are predominantly located in the active site of the HIV-1 protease and can directly interfere with inhibitor binding. Minor mutations, in contrast, are typically located distal to the active site. A central question is how these distal mutations contribute to resistance development. In this article, we present a systematic computational investigation of stability changes caused by major and minor mutations of the HIV-1 protease. As most small single-domain proteins, the HIV-1 protease is only marginally stable. Mutations that destabilize the folded, active state of the protease therefore can shift the conformational equilibrium towards the unfolded, inactive state. We find that the most frequent major mutations destabilize the HIV-1 protease, whereas roughly half of the frequent minor mutations are stabilizing. An analysis of protease sequences from patients in treatment indicates that the stabilizing minor mutations are frequently correlated with destabilizing major mutations, and that highly resistant HIV-1 proteases exhibit significant fractions of stabilizing mutations. Our results thus indicate a central role of minor mutations in balancing the marginal stability of the protease against the destabilization induced by the most frequent major mutations.

Quantitative sequence-activity modeling of ACE peptide originated from milk using ACC-QTMS amino acid indices.

Up to now, numerous peptides/hydrolysates derived from casein and whey protein have shown angiotensin-I-converting enzyme (ACE) inhibitory. In this research, quantum topological molecular similarity (QTMS) indices of amino acids were utilized in quantitative sequence-activity modeling (QSAM) to predict the activity of a set of milk-driven peptides with ACE inhibition. Since the derived peptides have not the same number of residues, we overcame this issue by auto cross covariance (ACC) methodology. Then, some QSAMs were built to predict the pIC50 value of ACE peptides derived from Bovine Casein and Whey. The model established an acceptable relationship between the selected variables and the pIC50 of the peptides. To estimate the performance of the developed models, casein and whey proteins from human, goat, bovine and sheep were virtually broken by trypsin and chymotrypsin enzymes and the ACE activity of the resultant virtual peptides were predicted and some new ACE peptides were proposed.

Cycloplatinated(II) Derivatives of Mercaptopurine Capable of Binding Interactions with HSA/DNA.

In this study, two new bis-cyclometalated Pt(II) complexes, [Pt(C^N)(S^N)] [S^N = deprotonated 6-mercaptopurine (6-MP) and C^N = deprotonated 2-phenylpyridine (ppy), 2a; C^N = deprotonated benzo[h]quinoline (bhq), 2b], are synthesized by the reaction of [PtR(SMe2)(C^N)] (R = Me or p-MeC6H4) with 1 equiv of 6-mercaptopurine (6-HMP) at room temperature. The complexes are fully characterized using 1H and 13C NMR spectroscopies, electrospray ionization mass spectrometry, and elemental analysis. Biomolecular interaction of complex 2a with human serum albumin (HSA) is studied by fluorescence, UV-vis, and circular dichroism (CD) spectroscopies. The binding constants (Kb) and number of binding sites (n) are evaluated using the Stern-Volmer equation. The intrinsic fluorescence of protein is quenched by a static quenching mechanism, with a binding constant of Kb ∼ 105 reflecting a high affinity of complex 2a for HSA. The thermodynamic parameters (ΔH°, ΔG°, and ΔS°) indicate that the interaction is a spontaneous process and hydrophobic forces play a main role in the reaction. The displacement experiments demonstrate that the reactive binding sites of HSA to complex 2a are mainly located within its hydrophobic cavity in subdomain IIA (site I). Synchronous fluorescence spectra reveal that complex 2a affected the microenvironment of tryptophan-214 residues in subdomain IIA of HSA. In the case of interaction of complex 2b and HSA, because of overlapping of the emission spectra of complex 2b with HSA, chemometric approaches are applied. The results indicate significant interaction between the tryptophan residue of HSA and complex 2b. Moreover, the binding of Pt(II) complexes 2a and 2b causes a reduction of the α-helix content of HSA, as obtained by far-UV CD spectroscopy. The average binding distance (r) between Pt(II) complexes and HSA is obtained by Förster's resonance energy-transfer theory. Also, a molecular docking simulation reveals that π-π-stacking and hydrophobic interactions between these complexes and HSA are significant. Furthermore, the interactions of platinum complexes, 2, with calf-thymus DNA (CT-DNA) are investigated. The UV-vis results and ethidium bromide competitive studies support an intercalative interaction of both Pt(II) complexes with DNA. The new complexes 2 are also screened for anticancer activities. The results show that complexes 2 exhibit significant anticancer activity against the K562 (chronic myelogenous leukemia) cell line.

Colorimetric and visual determination of hydrogen peroxide and glucose by applying paper-based closed bipolar electrochemistry.

A disposable paper-based bipolar electrochemical biosensor is reported for determination of glucose. The closed bipolar electrochemical cell is fabricated on a small part of paper using a laser printing-based process for paper hydrophobization. The bipolar and driving electrodes are provided by pressing the writing pencil HB on the paper. The mechanism of sensing of glucose is oxidation of the analyte in the sensing cell using glucose oxidase followed by reduction of the produced H2O2 by application of an external potential (10.0 V). This causes the oxidation of K4Fe(CN)6 in the presence of Fe(II) ions and subsequent formation of Prussian Blue (PB) particles in the reporting cell. The intensity of the blue color in the reporting cell is used as a visual and colorimetric signal that can be digitally read using a scanner of digital camera. The parameters affecting the performance of the device were optimized using experimental design and chemometrics modeling. The P-BPE represents a very wide response range that extends from 0.1 mmol.L-1 to 4.0 mol.L-1 in the case of hydrogen peroxide, and from 0.1 to 50 mmol.L-1 in the case of glucose. The limit of detections for hydrogen peroxide and glucose are 4.9 µmol.L-1 and 70 µmol.L-1 respectively. Graphical abstract Analyte solution (H2O2) and deionized water is injected to the sensing and the reporting cells respectively. By applying of an external potential, H2O2 reduction and potassium ferrocyanide (K4Fe(CN)6) oxidation is performed. This provides the appropriate condition for Prussian blue (PB) production (dark blue) in the reporting cell.

Determination of enantiomeric excess of some amino acids by second-order calibration of kinetic-fluorescence data.

In this investigation a new non-separative kinetic-spectroflourimetric method is proposed for the determination of lysine (lys), leucine (leu) and phenylalanine (phe) enantiomers as their o-phthaldialdehyde (OPA) derivatives in the presence of an optically active chiral thiol compound, 1-mercapto-2-propanol (MP). At ambient temperature and in the borate buffer media of pH 9.6, MP, OPA, as highly selective fluorogenic reagents, and amino acid (AA) enantiomers reacts with each other to yield two fluorescent diasteriomers of D and L-AA with maximum difference in fluorescence intensity at about 450 nm. To achieve information from the small spectral changes, the data are analyzed by Multivariate Curve Resolution Alternating Least Squares (MCR-ALS) method. Linear calibration curves are achieved to distinct D and L-lys, leu and phe in different mole ratios by applying appropriate constraints in MCR-ALS procedures. This is the first application of MCR-ALS in determination of enantiomeric excess (ee) using OPA/MP adduct as chiral reagent, which benefits from direct time dependent-fluorescence spectral analysis and does not require prior separation of chiral analytes. Both the cross-validated correlation coefficient (Q2) and root mean squares error of prediction (RMSEP) indicated satisfactory prediction ability of this method.

An optoelectronic tongue based on an array of gold and silver nanoparticles for analysis of natural, synthetic and biological antioxidants.

A colorimetric array, which can discriminate 20 food antioxidants of natural, synthetic and biological groups, is described. It consists of gold and silver nanoparticles that were synthesized using six different reducing and/or capping agents. The function of the array relies on the interaction of the antioxidants with the nanoparticles which causes aggregation or morphological changes. This, in turn, causes a change in the sensors' colors. The array produces a unique combination of colors for each antioxidant. The resulting colorations are determined by recording the absorbances of the arrays at wavelengths of 405, 450, 490 and 630 nm, or by capturing the images with a digital camera. The discriminatory ability of the array is investigated by principle component analysis and hierarchical cluster analysis. The method was applied to quantitative assay of gallic acid, caffeic acid, catechin, dopamine, citric acid, butylated hydroxytoluene and ascorbic acid. The respective limits of detection are 4.2, 13, 53, 6.9, 47, 3.5 and 43 nM, respectively. The simultaneous determination of 5 different antioxidants is achieved utilizing partial least square regression. The root mean square errors for prediction of the test set are 0.0650, 0.0782, 0.811, 0.0206 and 0.135 nM for gallic acid, catechin, butylated hydroxytoluene, dopamine, and ascorbic acid, respectively. This method demonstrates excellent potential for analysis of antioxidants in beverages such as tea and lemon juice. Graphical abstract Schematic of a method for the simultaneous determination of several antioxidants based on changes in the color of gold and silver nanoparticles. The antioxidants cause aggregation and/or morphological changes which can be detected by using both image analysis or by colorimetry.

Synthesis and biological evaluation of quinazolinone-based hydrazones with potential use in Alzheimer's disease.

Discovering multifunctional agents for the treatment of Alzheimer's disease (AD) is an attractive therapeutic approach. BACE1 (ß-site amyloid precursor protein cleaving enzyme 1) inhibitors may play a pivotal role in treating AD. Therefore, the discovery of novel non-peptide BACE1 inhibitors with desirable blood brain barrier permeability is a favorable approach for treatment. Moreover, the antioxidant potential of a drug could serve as an added value for designing dual-acting therapeutic agents. Here, we report the design, synthesis and biological evaluation of quinazolinone-hydrazone derivatives as new multi-target candidates for the treatment of AD. The compounds were investigated for their in vitro BACE1 inhibitory potential using a FRET-based enzymatic assay and also screened for antioxidant activity using DPPH. Among them, compound 4h bearing a 2,3-dichlorophenyl moiety showed the highest activity with an IC50 value of 3.7µM against BACE1. In addition, compound 4i with a 2,4-dihydroxyphenyl scaffold demonstrated moderate BACE1 inhibitory activity (IC50=27.6µM) with a significant antioxidant effect (IC50=8.4µM). Furthermore, docking studies revealed strong interaction between compound 4h and the key residues of BACE1 active site. These results demonstrate that quinazolinone-hydrazone derivatives represent a valuable scaffold for the discovery of novel non-peptidic BACE1 inhibitors.

Evaluation of long-heating kinetic process of edible oils using ATR-FTIR and chemometrics tools.

Long thermal oxidative kinetic and stability of four different edible oils (colza, corn, frying, sunflower) from various brands were surveyed with the use of attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) combined with multivariate curve resolution-alternative least square (MCR-ALS). Sampling from the heated oils (at 170 °C) was performed each 3 h during a 36-h period. Changes in the ATR-FTIR spectra of the oil samples in the range of 4000-550 cm-1 were followed as a function of heating time. MCR-ALS was utilized to resolve the concentration and spectral profiles of three detected kinetic components. Three variations in resolved concentration profiles were related to the thermal-deduction of triacylglycerol of unsaturated acid, appearance of hydroperoxides form of triacylglycerols and generation of secondary oxidation products. The kinetic profiles of these species were dependent on the type of oil. The proposed method can define a new way to monitor the oils' quality.

How conformational changes can affect catalysis, inhibition and drug resistance of enzymes with induced-fit binding mechanism such as the HIV-1 protease.

A central question is how the conformational changes of proteins affect their function and the inhibition of this function by drug molecules. Many enzymes change from an open to a closed conformation upon binding of substrate or inhibitor molecules. These conformational changes have been suggested to follow an induced-fit mechanism in which the molecules first bind in the open conformation in those cases where binding in the closed conformation appears to be sterically obstructed such as for the HIV-1 protease. In this article, we present a general model for the catalysis and inhibition of enzymes with induced-fit binding mechanism. We derive general expressions that specify how the overall catalytic rate of the enzymes depends on the rates for binding, for the conformational changes, and for the chemical reaction. Based on these expressions, we analyze the effect of mutations that mainly shift the conformational equilibrium on catalysis and inhibition. If the overall catalytic rate is limited by product unbinding, we find that mutations that destabilize the closed conformation relative to the open conformation increase the catalytic rate in the presence of inhibitors by a factor exp(ΔΔGC/RT) where ΔΔGC is the mutation-induced shift of the free-energy difference between the conformations. This increase in the catalytic rate due to changes in the conformational equilibrium is independent of the inhibitor molecule and, thus, may help to understand how non-active-site mutations can contribute to the multi-drug-resistance that has been observed for the HIV-1 protease. A comparison to experimental data for the non-active-site mutation L90M of the HIV-1 protease indicates that the mutation slightly destabilizes the closed conformation of the enzyme. This article is part of a Special Issue entitled: The emerging dynamic view of proteins: Protein plasticity in allostery, evolution and self-assembly.

Photodegradation study of nystatin by UV-Vis spectrophotometry and chemometrics modeling.

Nystatin, one of the tetraene antifungal antibiotics, is very sensitive to light. Thus, when nystatin is exposed to natural daylight, it is photodegraded to products of lower biological activity. In this work, the photodegradation kinetics of nystatin was monitored by a UV-Vis spectrophotometry method. The absorbance spectra of the nystatin, exposed to a 366 nm UV lamp, were recorded at different periods of time. By application of factor analysis to the absorbance data matrix, three absorbing chemical species, coexisting in the reaction system, were detected. The soft-modeling multivariate curve resolution-alternating least squares analysis of the evolutionary absorbance data revealed that nystatin undergoes photodegradation in a two-step consecutive manner. Hard-modeling data analysis suggested that reaction has first-order kinetics in the first step and zero-order kinetics in the second step. The reaction rate constants of the first and second steps were estimated as 0.0929 (+/-0.0076) and 0.0052 (+/-0.0016)/min, respectively. Finally, the pure spectra of the resolved chemical species were calculated.

Discrimination of bottled mineral water from tap water using a Dip-Type colorimetric paper-based sensor array and chemometrics.

Mineral water is a natural water that originated from an underground water table, a well, or a natural spring which is considered microbiologically intact. The revenue from the bottled mineral water industry will be USD 342.40 billion in 2023, and it is expected to grow at a compound annual growth rate (CAGR) of 5.24 %. Consequently, the discrimination of original bottled mineral water from tap water is an important issue that requires designing sensors for simple and portable identification of these two types of water. In this work, we have developed a Dip-Type colorimetric paper-based sensor array with three organic dyes (Bromothymol Blue, Bromophenol Blue, and Methyl Red) followed by chemometrics' pattern recognition methods (PCA and LDA) for discrimination of original bottled mineral waters from tap waters based on differences in ion variety and ion quantity. Forty brands of mineral water and twenty-six Tap water samples from different regions of Shiraz and other Iranian cities were analyzed by this sensor array. Moreover, these experiments were performed in two consecutive years to check the versatility of the sensor with seasonal changes in waters. This sensor array was able to discriminate these two water types from each other with an accuracy of > 95 % based on the analysis of 85 water samples.

Rapid detection and quantification of milk adulterants using a nanoclusters-based fluorescent optical tongue.

A paper-based sensor array consisting of eight nanoclusters (NCs) combined with multivariate analysis was used as a rapid method for the determination of animal sources of milk; goat, camel, sheep and cow. It was also used to detect and quantify three adulterants including sodium hypochlorite, hydrogen peroxide and formaldehyde in milk. The changes in fluorescence intensity of the NCs were quantified using a smartphone when the sensor array was immersed in the milk samples. The device generated a specific colorimetric signature for milk samples from different animals and for different adulterants. This allowed simultaneous identification of animal and adulterant sources with 100% accuracy. The device was found to be capable of accurately measuring the level of contaminants with a detection limit as low as 0.01% using partial least squares regression. In conclusion, a paper-based optical tongue device has been developed for the detection of adulterants in milk with point-of-need capability.

Rapid determination of hippuric acid as an exposure biomarker of toluene using a colorimetric assay and comparison with high-performance liquid chromatography.

Occupational exposure to toluene is associated with health risks that require reliable monitoring methods. Hippuric acid (HA), a urinary metabolite of toluene, serves as a valuable biomarker for such exposure. Colorimetric methods for the quantitative determination of HA have gained prominence due to their simplicity, cost-effectiveness, and suitability for field application. In the present study, a simple colorimetric technique was optimized for the determination of HA in the urine sample, and compared with a usual HPLC technique. The central composite design (CCD) was applied to examine the effective parameters on the colorimetric determination of HA. The calibration curve for HA was established within the concentration range of 6 to 100 mg L-1 with R2 = 0.97. The detection limit (LOD) and quantification limit (LOQ) were determined to be 1.8 mg L-1 and 6 mg L-1 respectively. The relative standard deviation (RSD%) was less than 5%, and the recovery% (R%) was 90.5-100.1. The overall results showed good agreement between the colorimetric and HPLC results. There was a significant relationship between the results obtained from HPLC and colorimetric methods especially for higher concentration levels of HA (≥ 500 mg/g creatinine). In conclusion, our optimized colorimetric method is a simple, cost-effective, and rapid method for determination of HA in occupational exposure, which is comparable with the HPLC technique.

Paper and nylon based optical tongues with poly(p-phenyleneethynylene)-fluorophores efficiently discriminate nitroarene-based explosives and pollutants.

Discrimination of nitroarenes with hydrophobic dyes in a polar (H2O) environment is difficult but possible via a lab-on-chip, with polymeric dyes immobilized on paper or nylon membranes. Here arrays of 12 hydrophobic poly(p-phenyleneethynylene)s (PPEs), are assembled into a chemical tongue to detect/discriminate nitroarenes in water. The changes in fluorescence image of the PPEs when interacting with solutions of the nitroarenes were recorded and converted into color difference maps, followed by cluster analysis methods. The variable selection method for both paper and nylon devices selects a handful of PPEs at different pH-values that discriminate nitroaromatics reliably. The paper-based chemical tongue could accurately discriminate all studied nitroarenes whereas the nylon-based devices represented distinguishable optical signature for picric acid and 2,4,6-trinitrotoluene (TNT) with high accuracy.

pH-independent optical sensing of heparin based on ionic liquid-capped gold nanoparticles.

A simple pH-independent optical method for the sensing of heparin, as a biomedically important polyionic drug, based on aggregation of gold nanoparticles (AuNPs) is described. The polyanionic heparin induces the aggregation of positively charged ionic liquid stabilized AuNPs, which results in a shift in the surface plasmon band and a consequent color change of the AuNPs from red to blue. The color change was monitored using UV-vis spectrophotometry and image analysis methods. The aggregation was confirmed by transmission electron microscopic measurements. The degree of aggregation was found to be proportional to the concentration of the added heparin, allowing its quantitative detection. The change in the absorbance and color-value has been used to monitor the concentration of heparin. This optical method can quantify heparin as low as 0.010 µg mL(-1) and the calibration is linear for a wide range of concentration.

Design and synthesis of novel 3,5-bis-N-(aryl/heteroaryl) carbamoyl-4-aryl-1,4-dihydropyridines as small molecule BACE-1 inhibitors.

Alzheimer disease (AD) is a neuronal dementia for which no treatment has been consolidated yet. Major pathologic hallmark of AD is the aggregated extracellular amyloid-ß plaques in the brains of disease sufferers. Aß-peptide is a major component of amyloid plaques and is produced from amyloid precursor protein (APP) via the proteolysis action. An aspartyl protease known as ß-site amyloid precursor protein cleaving enzyme (BACE-1) is responsible for this proteolytic action. Distinctive role of BACE-1 in AD pathogenesis has made it a validated target to develop anti-Alzheimer agents. Our structure-based virtual screening method led to the synthesis of novel 3,5-bis-N-(aryl/heteroaryl) carbamoyl-4-aryl-1,4-dihydropyridine BACE-1 inhibitors (6a-6p; in vitro hits). Molecular docking and DFT-based ab initio studies using B3LYP functional in association with triple-ζ basis set (TZV) proposed binding mode and binding energies of ligands in the active site of the receptor. In vitro BACE-1 inhibitory activities were determined by enzymatic fluorescence resonance energy transfer (FRET) assay. Most of the synthesized dihydropyridine scaffolds were active against BACE-1 while 6d, 6k, 6n and 6a were found to be the most potent molecules with IC50 values of 4.21, 4.27, 4.66 and 6.78 µM, respectively. Superior BACE-1 inhibitory activities were observed for dihydropyridine derivatives containing fused/nonfused thiazole containing groups, possibly attributing to the additional interactions with S2-S3 subpocket residues. Relatively reliable correlation between calculated binding energies and experimental BACE-1 inhibitory activities was achieved (R(2)=0.51). Moreover, compounds 6d, 6k, 6n and 6a exhibited relatively no calcium channel blocking activity with regard to nifedipine suggesting them as appropriate candidates for further modification(s) to BACE-1 inhibitory scaffolds.

Pronounced effect of lamination on plasma separation from whole blood by microfluidic paper-based analytical devices.

Many diseases are detected through blood tests. Currently, most blood tests are done on plasma instead of whole blood because of the interference of blood cells on detection results. Here, we developed a laminated microfluidic paper-based analytical device (L-µPAD) for the separation of plasma from whole blood without using plasma separation membrane (PSM). A lateral flow design consisting of a circular sampling zone and rectangular detection zone was patterned on the paper substrate using laser printing technology. The µPAD was then laminated after impregnation with KCl solution. Lamination and electrolyte addition represented synergistic effects on the separation by controlling the pore size of the paper. In addition, by preventing evaporation on one hand and squeezing paper pores on the other hand, lamination caused longer movement of the separated plasma, the longest plasma path reported so far. The separation process was monitored using colorimetric reagent bromocresol green and scanning electron microscopy. The process of separation was completed in less than 90s without significant hemolysis and the separated plasma was far from the interfering effect of red blood cells. We used the device for the determination of serum albumin. However, it represents the potential for point-of-care testing in multi-assay experiments too.