A 3D printed centrifugal microfluidic platform for automated colorimetric urinalysis

Colorimetric urinalysis is a commonly performed test for rapid and low-cost diagnosis. Conventional colorimetric urinalysis is manually conducted using dipsticks and suffers from difficulties in control of sample distribution and color interpretation. This paper reports a microfluidic platform for conducting automated colorimetric urinalysis. Centrifugal microfluidic technology was used for regulating the distribution of urine sample in designed volume and time sequence. The prototype of the microfluidic chip was fabricated using 3D printing technology. To test the feasibility of the prototype system, commercial urinalysis strips were integrated with the microfluidic system for detecting glucose, specific gravity, PH, and protein from simulated urine sample. The color change of the strips was recorded using a smartphone and analyzed to quantify the interested parameters. The H (hue), S (saturation) and V (value) coordinates of the HSV color space were extracted and related to the change of the four parameters. The intensity change of V channel showed good representation of the change of glucose concentration and specific gravity. The intensity change of S channel decreased as the increase of PH and protein concentration. The proposed Lab-on-CD platform has potential for automating colorimetric urinalysis to reduce the user errors, thus to made the testing results conducted by non-professionals more reliable.

     

Fabrication, structural characterization and sensing properties of polydiacetylene nanofibers templated from anodized aluminum oxide

Polydiacetylene (PDA), as a unique conjugated polymer, has shown its potential in the application of chem/bio-sensors and optoelectronics. In this work, we first infiltrated PDA monomer (10, 12-pentacosadiynoic acid, PCDA) melt into anodized aluminum oxide template, and then illuminated the infiltrated template with UV light to initiate the polymerization of PCDA. After etching away the aluminum oxide templates, we obtained solid poly-PCDA nanofibers. We found that even tightly confined in template pores with diameter as small as ∼35 nm, PCDA crystals were able to be polymerized through a solid polymerization mechanism induced by UV light. Poly-PCDA nanofibers, both in the released form and embedded in the template, showed characteristic blue to red color change in sensing exposure of organic solvents and temperature increasing, and the red colored fibers possessed strong fluorescence. Moreover, poly-PCDA nanofibers were highly crystalline, and oriented favorably in some certain direction due to the confinement of nanopores, as demonstrated by X-ray diffraction texture analysis and orientation distribution analysis by scanning confocal optical microscopy.     

Modeling antimicrobial effect of different grape pomace and extracts on S.aureus and E.coli in vegetable soup using artificial neural network and fuzzy logic system

In this study, antibacterial activities of the grape pomace powders (GPP) and grape pomace extracts (GPE) of Turkeys’ five different grape varieties (Emir, Gamay, Kalecik Karasi, Narince and Okuzgozu grape varieties) were determined against Staphylococcusaureus and Escherichiacoli in vegetable soup at 2, 5 and 10% concentrations. Antibacterial effects of GPE were more effective than those of the GPP against the bacteria. The bacterial counts decreased with increasing extract concentration. The highest antibacterial activity of the GPE was for Gamay and Kalecik Karasi against both bacteria. The 10% concentration of Gamay GPP completely inhibited S.aureus at the end of 120th h. Compared to E.coli, S.aureus was more sensitive to all GPP and GPE. This bacterium was inhibited by 10% concentrations of all the extracts at the initial storage time. Data were analyzed to predict antibacterial effects of the GPP and GPE against both bacteria by adaptive neuro fuzzy inference system (ANFIS) and artificial neural network (ANN) and multiple linear regression (MLR) models. As a result, ANFIS model was found to be better than the ANN and MLR for predicting antibacterial effects of GPP and GPE against S.aureus and E.coli in the soup.     

A PDMS microfluidic impedance immunosensor for E. coli O157:H7 and Staphylococcus aureus detection via antibody-immobilized nanoporous membrane

In this article, a PDMS microfluidic immunosensor integrated with specific antibody immobilized alumina nanoporous membrane was developed for rapid detection of foodborne pathogens Escherichia coli O157:H7 and Staphylococcus aureus with electrochemical impedance spectrum. Firstly, antibodies to the targeted bacteria were covalently immobilized on the nanoporous alumina membranes via self assembled (3-glycidoxypropyl)trimethoxysilane (GPMS) silane. Then, the impedance spectrum was recorded for bacteria detection ranging from 1 Hz to 100 kHz. The maximum impedance amplitude change for these two food pathogens was around 100 Hz. This microfluidic immunosensor based on nanoporous membrane impedance spectrum could achieve rapid bacteria detection within 2 h with a high sensitivity of 10² CFU/ml. Cross-bacteria experiments for E. coli O157:H7 and S. aureus were also explored to testify the specificity. The results showed that impedance amplitude at 100 Hz had a significant reduction in binding of bacteria when the membrane was exposed to non-specific bacteria.     

用于食品气味快速检测的可视传感器特性研究

针对食品品质快速检测的需求和人工嗅觉技术存在的检测范围窄、受环境湿度影响大等缺陷,根据金属卟啉化合物与有机小分子气体反应后发生颜色变化的原理,筛选二十多种对食品常见气味成分响应的金属卟啉制成可视传感器阵列.以食品腐败的常见特征气体为研究对象,对传感器阵列的选择性、检测范围、水蒸气对传感器的影响等特性进行初步研究.试验结果表明,设计的可视传感器阵列具有良好的选择性、灵敏性、重现性和稳定性,且受环境湿度影响不大,在食品品质的快速检测方面有广泛的应用前景.     

QM/MM investigation of the reaction rates of substrates of 2,3-dimethylmalate lyase: A catabolic protein isolated from Aspergillus niger

Aspergillus niger is an industrially important microorganism used in the production of citric acid. It is a common cause of food spoilage and represents a health issue for patients with compromised immune systems. Recent studies on Aspergillus niger have revealed details on the isocitrate lyase (ICL) superfamily and its role in catabolism, including (2R, 3S)-dimethylmalate lyase (DMML). Members of this and related lyase super families are of considerable interest as potential treatments for bacterial and fungal infections, including Tuberculosis. In our efforts to better understand this class of protein, we investigate the catalytic mechanism of DMML, studying five different substrates and two different active site metals configurations using molecular dynamics (MD) and hybrid quantum mechanics/molecular mechanics (QM/MM) calculations. We show that the predicted barriers to reaction for the substrates show good agreement with the experimental k_cat values. This results help to confirm the validity of the proposed mechanism and open up the possibility of developing novel mechanism based inhibitors specifically for this target.     

Low-cost colorimetric sensor for the quantitative detection of gaseous hydrogen sulfide

A simple, rapid and low-cost method for differentiating a wide range of concentrations of gaseous hydrogen sulfide (H₂S) is described. A large dynamic range (50 ppb to 50 ppm) was successfully classified at ambient temperature using a colorimetric sensor array comprised of chemoresponsive dyes coupled to a commercially available 8-bit flatbed scanner. Principle component analysis of the composite magnitude and kinetics of color change for the array of dye spots over the entire dynamic range resulted in 100% classification. This was achieved by including chemoresponsive dyes which reacted specifically with H₂S at different detection thresholds.     

Exploring the binding sites of Staphylococcus aureus phenylalanine tRNA synthetase: A homology model approach

Increased resistance of MRSA (multidrug resistance Staphylococcus aureus) to anti-infective drugs is a threat to global health necessitating the development of anti-infectives with novel mechanisms of action. Phenylalanine tRNA synthetase (PheRS) is a unique enzyme of the aminoacyl-tRNA synthetases (aaRSs), which are essential enzymes for protein biosynthesis. PheRS is an (αb)₂ tetrameric enzyme composed of two alpha subunits (PheS) and two larger beta subunits (PheT). Our potential target in the drug development for the treatment of MRSA infections is the phenylalanine tRNA synthetase alpha subunit that contains the binding site for the natural substrate. There is no crystal structure available for S. aureus PheRS, therefore comparative structure modeling is required to establish a putative 3D structure for the required enzyme enabling development of new inhibitors with greater selectivity. The S. aureus PheRS alpha subunit homology model was constructed using Molecular Operating Environment (MOE) software. Staphylococcus haemolyticus PheRS was the main template while Thermus thermophilus PheRS was utilised to predict the enzyme binding with tRNA^phe. The model has been evaluated and compared with the main template through Ramachandran plots, Verify 3D and Protein Statistical Analysis (ProSA). The query protein active site was predicted from its sequence using a conservation analysis tool. Docking suitable ligands using MOE into the constructed model were used to assess the predicted active sites. The docked ligands involved the PheRS natural substrate (phenylalanine), phenylalanyl-adenylate and several described S. aureus PheRS inhibitors.     

Centrifugal automation of a triglyceride bioassay on a low-cost hybrid paper-polymer device

We present a novel paper-polymer hybrid construct for the simple automation of fundamental microfluidic operations in a lab-on-a-disc platform. The novel design, we term a paper siphon, consists of chromatographic paper strips embedded along a siphon microchannel. The paper siphon relies on two main interplaying forces to create unique valving and liquid-sampling methods in centrifugal microfluidics. At sufficiently low speeds, the inherent wicking of the paper overcomes the rotationally induced centrifugal force to drive liquids towards inwards positions of the disc. At elevated speeds, the dominant centrifugal force will extract liquid from the siphon paper strip towards the edge of the disc. Distinct modes of flow control have been developed to account for water (reagent) and more viscous plasma samples. The system functionality is demonstrated by the automation of sequential sample preparation steps in a colorimetric triglyceride assay: plasma is metered from a whole blood sample and incubated with a specific enzymatic mixture, followed by detection of triglyceride levels through (off-disc) absorbance measurements. The successful quantification of triglycerides and the simple fabrication offer attractive directions for such hybrid devices in low-cost bioanalysis.     

A vision-taste interference model and the EEG measurement

Taste cognition can be interfered with by visual information, but the mechanism by which this happens has not been clarified. We assumed an interference model in the processes of taste and vision information. The model was tested with frequency analysis on EEG and using the switch response time. The tasks were matched/miss-matched between taste and vision information about orange juice and apple juice. There were changes in the α waves that originated in the visual processing of a juice package, and changes in the β waves that originated in the taste processing. There is the possibility of a parallel processing mechanism in the vision-taste interference.     

Facile method to detect oligonucleotides with functionalized polydiacetylene vesicles

Polydiacetylene vesicles were used to detect oligonucleotides in the present paper. For this system, probe-oligonucleotide-functionalized polydiacetylene vesicles were used as indicators of color transition and amplification tags at the same time in the detection of oligonucleotides. The method described is simple, rapid, and suitable for detection of oligonucleotides by naked eye. The influences of dimyristoylphosphatidylcholine (DMPC) in the color changeable polydiacetylene vesicles on the detection of oligonucleotides were also studied. The experimental results demonstrated that DMPC can effectively adjust the mechanical stress of polydiacetylenic structure and the content of DMPC in polydiacetylene structure is a crucial factor for a more sensitive polydiacetylene-based sensor. The maximum colorimetric response for the detection of oligonucleotides was obtained for the polydiacetylene vesicle composed of TCDA/DMPC/probe-DNA with molar ratio of 0.60:0.39:0.01. Both cases for too much or for too less DMPC in polydiacetylene vesicles are not benefit to the detection for this system. The TEM images further confirmed the results obtained.     

Preparation of Cu2O nano-colloid and its application as selective colorimetric sensor for Ag ion

Current work reports a method of preparation of stable yellow copper (I) oxide, nano-colloid by a solution route using Cu (II) salt solution and sodium borohydride. The reduction process was carried out in a controlled manner in air at around 50 °C in the presence of alginate matrix. The nanophase was characterized by techniques such as electronic spectroscopy, infrared spectroscopy, powder X-ray diffraction and transmission electron microscopy. Sensor property of the colloid for the detection of metal ions such as Ag⁺, Na⁺, K⁺, Ca²⁺, Pb²⁺, Cd²⁺, Zn²⁺, Hg²⁺, Mg²⁺ and As⁵⁺ has been studied at room temperature. A distinct color change from yellow to dark brown was noticed in the case of Ag⁺ ion. This is associated with a shift in ‘λ_max’ value from 448 nm to 478 nm. Whereas, no such significant visible color change was noticed on the addition of solutions containing other metal ions. Thus, in the present study Cu₂O nano-colloid was demonstrated as a highly specific and selective liquid colorimetric sensor for Ag⁺ ion.     

An apple image segmentation method based on a color index obtained by a genetic algorithm

Harvesting and spraying robots based on machine vision have become important in modern agricultural engineering. Fast segmentation of fruit images is the main task of robotic picking and spraying in orchards. In this paper, a color index-based segmentation method for apple images was proposed. It can automatically obtain a specific color index according to the image segmentation task. This method was used to obtain color index and segmentation thresholds for segmenting apple images. The mean pixel segment accuracy, mean intersection over union, mean dice similarity coefficient, and mean segment time was 0.90, 0.81, 0.98, and 20 (ms). The result showed that this method could segment apple in orchard images effectively and fastly. It could be used in precise apple planting management. At the same time, this paper provided a systematic method to get a specific color index.

     

Per-6-ammonium-β-cyclodextrin/p-nitrophenol complex as a colorimetric sensor for phosphate and pyrophosphate anions in water

Using per-6-ammonium-β-cyclodextrin (per-6-NH₃⁺-β-CD) as an anion binding site and p-nitrophenol as a spectroscopic probe, a colorimetric sensor is developed for phosphate and pyrophosphate anions in water. Per-6-NH₃⁺-β-CD forms a 1:2 inclusion complex with p-nitrophenol as characterized by NOESY and ESI-MS spectra and it undergoes a distinct color change from colorless to intense yellow upon exposure to phosphate or pyrophosphate anions over other anions including perchlorate, ATP²⁻, ADP²⁻ and AMP²⁻. The seven ammonium groups of 1, bind phosphate (characterized by ESI-MS) or pyrophosphate anions specifically by electrostatic interaction. This naked eye sensing is significant for very low concentration (5 × 10⁻⁵ M) of anion with 1:2 ratio of host and guest.     

On the parameterized complexity of some optimization problems related to multiple-interval graphs

We show that for any constant t≥2, k-Independent Set and k-Dominating Set in t-track interval graphs are W[1]-hard. This settles an open question recently raised by Fellows, Hermelin, Rosamond, and Vialette. We also give an FPT algorithm for k-Clique in t-interval graphs, parameterized by both k and t, with running time , where n is the number of vertices in the graph. This slightly improves the previous FPT algorithm by Fellows, Hermelin, Rosamond, and Vialette. Finally, we use the W[1]-hardness of k-Independent Set in t-track interval graphs to obtain the first parameterized intractability result for a recent bioinformatics problem called Maximal Strip Recovery (MSR). We show that MSR-d is W[1]-hard for any constant d≥4 when the parameter is either the total length of the strips, or the total number of adjacencies in the strips, or the number of strips in the solution.     

Image recoloring using linear template mapping

We propose an artistic recoloring method that enhances the perception of complex scenes, while preserving the visual quality of the original image. Our algorithm employs the template which contains the information of color theme. The colors of template is selected based on the Munsell color and are designed on the a ^??? b ^??? chromatic plane of the CIE L ^??? a ^??? b ^??? color space. Template can be used to recolor the original image with simpler and more focused color contrasts. The proposed algorithm consists of the three steps. First, we calculate the regression line for the colors on the original image and the template. Then we create a transformation refer to the relationship between the two regression lines. This transformation is used to change the color distribution in the source image. Finally, the transformed color distribution is mapped from the chromatic a ^??? b ^??? plane to become the template.     

A highly sensitive and selective colorimetric and off-on fluorescent chemosensor for Cu based on rhodamine B derivative

A new rhodamine B derivative colorimetric and fluorescent sensor (1) was synthesized by condensation reaction of rhodamine B hydrazide and 2,4-dihydroxybenzaldehyde, which showed reversible and highly selective and sensitive recognition toward Cu²⁺ over other examined metal ions. Upon addition of Cu²⁺, sensor 1 exhibits remarkably enhanced absorbance intensity and color change from colorless to pink in DMSO and MeCN aqueous buffer solution or pure MeCN, and shows significant off-on fluorescence accompanied by color changes from colorless to orange in MeCN. The sensor 1 was also successfully applied to the determination of Cu²⁺ in water samples.     

Fluid flow-based description of the geometrical features in fluidic channels using the Shannon’s information theory: an exploratory study

Microfluidic analytical devices manufactured on paper and similar inexpensive substrates (µ-PADs) have shown considerable promise for disease diagnostics in resource-limited regions. However, current commercialization approaches can be improved substantially by addressing existing technical challenges associated with µ-PADs. Among these, off-device plasma separation from whole blood is a critical challenge in µ-PAD technology that limits commercialization. Existing µ-PADs made by combining multiple components require extra fabrication steps and manufacturing material. Our approach utilizes a two-step plasma process to fabricate single-layer semi-enclosed µ-PADs directly on a commercially available blood plasma separation membrane to incorporate blood plasma separation functionality into the device. The semi-enclosed µ-PADs are bonded with low-cost adhesive plastic tape to provide mechanical support to the device and make it more mechanically robust for field applications. Detection zones of the µ-PADs have also been modified with a cellulose nanocrystal (CNC) to increase colorimetric signal homogeneity, thus enhancing signal quality. The CNC-modified µ-PADs have been used for colorimetric detection of two model analytes (glucose and albumin) in whole blood. Colorimetric signals for both glucose and albumin from whole blood samples were consistent with the calibration curves generated using stock solutions.

     

A highly selective triphenylamine-based indolylmethane derivatives as colorimetric and turn-off fluorimetric sensor toward Cu detection by deprotonation of secondary amines

A new triphenylamine-based fluorogenic probe bearing an indolylmethane unit (R1) was developed as a fluorescent chemosensor with high selectivity toward Cu²⁺ over other cations tested. The new probe R1 only sensed Cu²⁺ among heavy and transition metal (HTM) ions in CH₃CN/H₂O (70/30, v/v) solution. The capture of Cu²⁺ by the receptor resulted in deprotonation of the secondary amine conjugated to the triphenylamine, so that the electron-donation ability of the “N” atom would be greatly enhanced; thus sensor showed a 250 nm change in the new absorption band (from 291 nm to 541 nm) and a large colorimetric response, it also exhibited the large decrease in fluorescence intensity at 378 nm and affinity to Cu²⁺ over other cations such as Hg²⁺, Fe³⁺, Pb²⁺, Zn²⁺, Cd²⁺, Ni²⁺, Co²⁺ and Mn²⁺ make this compound a useful chemosensor for Cu²⁺ detection in CH₃CN/H₂O (70/30, v/v) mixture. The probe R1 (c = 1.0 × 10⁻⁶ M) displayed significant fluorescence change and colorimetric change upon addition of Cu²⁺ among the metal ions examined.