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Two novel and low cost liquid-liquid extraction methods for the separation of bismuth(III) at trace level from aqueous medium have been developed. The two methods were based upon the formation of yellow colored ternary complex ion associates of tetraiodobismuth(III) complex anion, BiI4 - with the ion-pairing reagent 2,3,5-tetraphenyltetrazoliumchloride (Tz+.Cl-) and 1, 10 phenanthroline (Phen) in sulfuric acid medium. The effect of various parameters e.g. pH, organic solvent, shaking time, etc. on the preconcentration of bismuth(III) from the aqueous media by the reagent was investigated. The developed colored complex ion associates [Tz+.BiI4 -] and [Phen+.BiI4 -] were extracted quantitatively into acetone-chloroform (1:1v/v) and methylisobutylketone (MIBK), respectively. The compositions of the formed complex ion associates [Tz+.BiI4 -] and [Phen+.BiI4 -] were determined by the Job's method at 500 and 490 nm, respectively. The plots of bismuth(III) concentration (0-17 μg mL-1) versus absorbance of the associates at 500 and 490 nm were linear with good correlation coefficient (R²=0.998). The developed method of the ion associate [Tz+.BiI4 -] two methods was applied successfully for the analysis of bismuth in water. [ABSTRACT FROM AUTHOR]

The use of lateral flow assays exploiting antibodies is well established in different fields due to their advantages, which include low cost, ease of production and rapid response, with the only required end-user intervention being sample addition. In recent years, aptamer-based lateral flow assays are garnering increasing interest offering a highly cost-effective and more flexible alternative to antibodies. In this review, an overview of the aptamer-based lateral flow assays developed to date is provided, highlighting the advantages of using aptamers and their ability to be incorporated into formats not possible with antibodies. [ABSTRACT FROM AUTHOR]

Detection of alpha-l-fucosidase has been shown to have relevance in diagnosing hepatocellular carcinoma. Few assays have been developed to measure this enzyme, with most relying on colorimetric techniques involving the enzyme's kinetics. While these assays are facile and quick, the sensitivity is not always sufficient for early tumor detection. To improve upon previous assays for alpha-l-fucosidase, a fluorescence based immunoassay was produced implementing an alpha-l-fucosidase specific antibody (FUCA2). The immobilization of the alpha-l-fucosidase-specific antibody onto a quartz slide was investigated with several bioconjugation approaches and an immunoassay for detection of alpha-l-fucosidase was produced. The immunoassay was utilized to produce calibration curves for quantifying alpha-l-fucosidase concentrations in both PBS and human blood serum. A detection limit of 10 nM was found using human blood serum, which is well below the diagnostic cutoff point of 80 nM. [ABSTRACT FROM AUTHOR]

In this work we report the mapping of the binding site of the only progesterone aptamer published to date, in an approach referred to as aptatope mapping. By linking the binding data obtained from microscale thermophoresis analysis to the structural differences on the ring structure of a range of steroids, we elucidated the moieties involved in aptamer-progesterone binding. This approach can be further exploited for the characterization of aptamer specificity and ultimately facilitate the development of aptamer-based assays depending on the desired specificity. [ABSTRACT FROM AUTHOR]

Alpha-l-fucosidase is a known biomarker for hepatocellular carcinoma that has shown great potential in diagnostics. Most of the focus for this enzyme has been on the free form found in serum; however, little is known of the properties of the minor portion of membrane-bound alpha-l-fucosidase. To better understand the properties of membrane-bound alpha-l-fucosidase, this enzyme was surveyed at the air-water interface. Alpha-l-fucosidase is able to form a stable Langmuir monolayer, which was confirmed through surface-pressure and surface-potential area isotherms, as well as infrared reflection-absorption spectroscopy (IRRAS). Furthermore, an interaction between the alpha-l-fucosidase Langmuir monolayer and a specific antibody for this enzyme, FUCA2, was observed. [ABSTRACT FROM AUTHOR]

The chromogenic reagent 4,4′-dichloro(3-mercapto-1,5-diphenylformazan), Cl 2 H 2 D Z , forms a yellow–red-coloured complex with selenium(IV). The produced complex species was extracted quantitatively into n -hexane, and its absorbance was measured at 416  nm. The chemical composition of the extracted selenium(IV)-Cl 2 H 2 D Z chelate and the molar absorptivity at 416  nm were found to be [SeO (Cl 2 HD Z ) 2 ] and 9  ×  10 4   L  mol -1   cm -1 , respectively. The values of the extraction constants ( K D , K ex , β ) enable a convenient application of the proposed system for the liquid–liquid extraction procedure and sequential spectrophotometric determination of traces of inorganic selenium(IV) and/or selenium(VI) after reduction of the later to selenium(IV) with HCl (6  M). Beer's law and Ringbom's plots were obeyed in the concentration range 0.01–20 and 0.5–19  µg  mL -1 of selenium(IV), respectively, with a relative standard deviation of 2.2%. The proposed method has been successfully applied to the determination of selenium(IV) or (VI) and total inorganic selenium(IV) and (VI) in tap and freshwater samples. [ABSTRACT FROM AUTHOR]

Due to the extreme infectivity of Yersinia pestis it poses a serious threat as a potential biowarfare agent, which can be rapidly and facilely disseminated. A cost-effective and specific method for its rapid detection at extremely low levels is required, in order to facilitate a timely intervention for containment. Here, we report an ultrasensitive method exploiting a combination of isothermal nucleic acid amplification with a tailed forward primer and biotinylated dNTPs, which is performed in less than 30 min. The polymerase chain reaction (PCR) and enzyme linked oligonucleotide assay (ELONA) were used to optimise assay parameters for implementation on the LFA, and achieved detection limits of 45 pM and 940 fM using SA-HRP and SA-polyHRP, respectively. Replacing PCR with isothermal amplification, namely recombinase polymerase amplification, similar signals were obtained (314 fM), with just 15 min of amplification. The lateral flow detection of the isothermally amplified and labelled amplicon was then explored and detection limits of 7 fM and 0.63 fg achieved for synthetic and genomic DNA, respectively. The incorporation of biotinylated dNTPs and their exploitation for the ultrasensitive molecular detection of a nucleic acid target has been demonstrated and this generic platform can be exploited for a multitude of diverse real life applications. Image 1 • Ultrasensitive molecular detection of Yersinia pestis using biotinylated dNTPs and tailed primer is demonstrated. • Optimisation of ratio of biotinylated dNTPs: natural dNTPs is carried out using PCR and ELONA. • Optimised parameters were exploited using RPA. • Lateral flow assays for detection of single tailed amplicon and biotinylated dNTPs with SA-AuNPs was developed. • Real samples were tested. [ABSTRACT FROM AUTHOR]

This study investigates the surface chemistry properties of the tyrosinase enzyme Langmuir monolayer at air-aqueous interface using sodium chloride in the subphase to induce the surface activity of the enzyme. Investigation of surface packing and stability of the tyrosinase Langmuir monolayer were performed using surface chemistry experiments while spectroscopic analysis was done to study enzyme conformation. It was found that the tyrosinase enzyme forms a fluid film at air-aqueous interface with good stability as shown by compression-decompression cycles experiments and stability measurements at various surface pressures. UV-vis absorption and fluorescence measurements at different surface pressures revealed that the Langmuir monolayer has good homogeneity with no evidence of aggregates during compression. To gain insight on the conformation of tyrosinase Langmuir monolayer p-polarized infrared-reflection absorption spectroscopy was used. It was found that at high surface pressures the predominant secondary structures were β-sheets while at lower surface pressure both α -helices and β-sheets were present. The circular dichroism spectra were obtained by transferring the Langmuir monolayer at 10 mN.m−1 to a solid quartz support (Langmuir-Blodgett film, LB film), which showed that the major conformation present were α-helices. Images from the immobilized LB films were obtained using atomic force microscopy which showed homogenous and regular deposition with a mean thickness ranging from 3 to 4 nm. [ABSTRACT FROM AUTHOR]

Highlights • Duplex PCR amplification of pork in beef and chicken products. • Tailed primers allow the generation of duplex flanked by single stranded tails. • Enzyme-linked oligonucleotide assay for direct detection via hybridisation of PCR products. • Sensitivity of 71–188 pg of genomic DNA from each species was achieved. • The presence of 0.5–1% pork in binary DNA add-mixtures and in raw meat mixtures could be detected. Abstract In this work, a duplex PCR–Enzyme Linked Oligonucleotide Assay (ELONA) is reported for the sensitive and reliable detection of pork adulteration in beef and chicken products, two of the most widely consumed meat types in the world. The strategy relies on the use of species-specific tailed primers for duplex amplification and simple dilution of the PCR reactions for direct colorimetric detection via hybridization, eliminating the need for any other post-amplification steps. A high sensitivity was achieved, with as low as 71–188 pg of genomic DNA able to be detected using mixtures of control DNA from each species. The strategy was validated using DNA add-mixtures as well as DNA extracted from raw meat mixtures and 0.5–1% w/w pork could be easily detected when mixed with beef or chicken. The proposed approach is simple, sensitive and cost-effective compared to equivalent commercial kits suitable for detecting adulterant pork levels in meat products. [ABSTRACT FROM AUTHOR]

Abstract Hepatocellular carcinoma (HCC) is among the leading causes of mortality in the world. The detection of HCC in its early stage is the key for early treatment and thus the improvement of the chances of survival. Among the various methods of HCC screening, assays based on the detection of biomarker that is specific to HCC such as alpha- l -fucosidase (AFU) have been regarded as the most prominent methods. In this regards, a new assay for the detection of AFU to screen HCC was developed. This assay was based on the energy transfer between carbon dots (C-dots) and gold nanoparticles (AuNPs), the concentration of AFU could be monitored by the degree of C-dots fluorescence quenching due to the energy transfer. With this assay, a limit of detection of 3.4 nM (well below the diagnostic cutoff point of 80 nM), and a broad linear range of detection from 11.3 to 200 nM were achieved. We also demonstrate the determination of the concentration of AFU in human blood serum. Graphical abstract Image 1 Highlights • Energy transfer between carbon dots and AuNPs was used to design assay for the detection of alpha- l -fucosidase. • A sandwich assay was designed by combining polyclonal antibody coated AuNPs with monoclonal antibody attached to carbon dots. • A limit of detection of 3.4 nM and linear range from 11.3 to 200 nM were achieved. [ABSTRACT FROM AUTHOR]

Cholera and milder diarrheal disease are caused by Vibrio cholerae and enterotoxigenic Escherichia coli and are still a prominent public health concern. Evaluation of suspicious isolates is essential for the rapid containment of acute diarrhea outbreaks or prevention of epidemic cholera. Existing detection techniques require expensive equipment, trained personnel and are time-consuming. Antibody-based methods are also available, but cost and stability issues can limit their applications for point-of-care testing. This study focused on the selection of single stranded DNA aptamers as simpler, more stable and more cost-effective alternatives to antibodies for the co-detection of AB 5 toxins secreted by enterobacteria causing acute diarrheal infections. Cholera toxin and Escherichia coli heat-labile enterotoxin, the key toxigenicity biomarkers of these bacteria, were immobilized on magnetic beads and were used in a SELEX-based selection strategy. This led to the enrichment of sequences with a high % GC content and a dominant G-rich motif as revealed by Next Generation Sequencing. Enriched sequences were confirmed to fold into G-quadruplex structures and the binding of one of the most abundant candidates to the two enterotoxins was confirmed. Ongoing work is focused on the development of monitoring tools for potential environmental surveillance of epidemic cholera and milder diarrheal disease. [Display omitted] • Vibrio cholerae toxin and Escherichia coli heat-labile enterotoxin were targeted for aptamer development. • Magnetic-bead SELEX was performed and combined with Next Generation Sequencing for sequence analysis. • Enrichment in common enterotoxin-binding sequences containing a dominant G-rich motif was observed. • The folding of G-rich enriched sequences into G-quadruplex structures was confirmed. • A G-quadruplex aptamer with good binding affinity for both AB 5 enterotoxins was identified. [ABSTRACT FROM AUTHOR]

The interface of nucleic acids and nanomaterials is among the most promising fields in recent years. Considerable efforts have been devoted to the development of novel systems based on the two components for various promising applications such as sensing, bioimaging, drug delivery, and theranostics. However, the determination of nucleic acid concentration in these systems remains as a challenge due to the interference of nanoparticles. To this end, we developed a simple, yet reliable, method to quantify the nucleic acid concentration in their nanoparticle or polymer conjugates based on circular dichroism (CD) spectroscopy. In this paper, three nucleic acids, namely, DNA sodium salt from calf thymus (NaDNA), DNA from herring sperm (hsDNA), and ribonucleic acid from torula yeast (tyRNA), were noncovalently conjugated to three nanoparticles. The concentrations of the three nucleic acids in their nanoparticle conjugates were successfully determined on the basis of CD spectra calibration curves. [ABSTRACT FROM AUTHOR]

Carbon dots, a recent member of the renowned carbon-based nanomaterials family, have attracted significant interest from various fields. The extraordinary properties, including excellent photoluminescence, high biocompatibility, and tunable surface functionalities as well as the abundant and inexpensive nature, have led to remarkable bioapplications in bioimaging, drug delivery, and theranostics development. In this article, studies on the interaction of C-dots with biomacromolecules are reviewed first, and recent developments of C-dots for target-specific bioimaging, drug delivery as well as theranostics development are highlighted and discussed. [ABSTRACT FROM AUTHOR]

The rapid and sensitive detection of small molecules is garnering increasing importance, and aptamers show great promise in replacing expensive, elaborate detection platforms exploiting chromatographic separation or antibody-based assays. The characterization of aptamer interaction with small molecule targets is not facile, and there is a mature need for a rapid, high-throughput technique for the analysis of aptamer-small molecule kinetics and affinity. In this work we present methodologies for the evaluation of aptamer-small molecule interactions, using the aptamers reported against the steroid 17β-estradiol as a model system. Microscale thermophoresis, apta-PCR affinity assay and surface plasmon resonance were explored to evaluate the reported aptamers’ binding properties in terms of affinity and specificity, and were demonstrated to be successfully applied to the analysis of aptamer-small molecule interactions. [ABSTRACT FROM AUTHOR]

In this work, different methodologies were evaluated in search of robust, simple, rapid, ultrasensitive, and user-friendly lateral flow aptamer assays. In one approach, we developed a competitive based lateral flow aptamer assay, in which β-conglutin immobilized on the test line of a nitrocellulose membrane and β-conglutin in the test sample compete for binding to AuNP labeled aptamer. The control line exploits an immobilized DNA probe complementary to the labeled aptamer, forcing displacement of the aptamer from the β-conglutin-aptamer complex. In a second approach, the competition for aptamer binding takes place off-strip, and following competition, aptamer bound to the immobilized β-conglutin is eluted and used as a template for isothermal recombinase polymerase amplification, exploiting tailed primers, resulting in an amplicon of a duplex flanked by single stranded DNA tails. The amplicon is rapidly and quantitatively detected using a nucleic acid lateral flow with an immobilized capture probe and a gold nanoparticle labeled reporter probe. The competitive lateral flow is completed in just 5 min, achieving a detection limit of 55 pM (l.l finol), and the combined competitive-amplification lateral flow requires just 30 min, with a detection limit of 9 fM (0.17 amol). [ABSTRACT FROM AUTHOR]

Peptides and proteins have become very promising drug candidates in recent decades due to their unique properties. However, the application of these drugs has been limited by their high enzymatic susceptibility, low membrane permeability and poor bioavailability when administered orally. Considerable efforts have been made to design and develop drug delivery systems that could transport peptides and proteins to targeted area. Although it is of great importance to determine the composition after loading a drug to the carrier, the ability to do so is significantly limited by current analytical methods. In this letter, five important proteins, α 1 -antitrypsin, hemoglobin human, human serum albumin, human transferrin and r-globulin were chemically conjugated to two model drug carriers, namely carbon dots and polymer O-(2-carboxyethyl) polyethylene glycol. A simple yet convenient method based on circular dichroism spectroscopy was developed to determine the compositions of the various protein-carrier conjugates. [ABSTRACT FROM AUTHOR]

The illicit use of anabolic androgenic steroids (AAS) as performance-enhancing drugs remains a global issue threatening not only the credibility of competitive sports but also public health due to the well-documented adverse effects they elicit. AAS abuse is not restricted only to professional sports, but also extends to recreational athletes and adolescents as well as in livestock production as growth-promoting agents. Testosterone and nandrolone are among the AAS most frequently exploited. Gas chromatography-mass spectrometry is the reference method for AAS detection, but it is strictly laboratory-based and cannot be performed on-site. The great potential of aptamers in bioanalytical applications and specifically for the development of simple analytical tools suitable for on-site analysis has been extensively documented. In this report, we describe the selection and identification of aptamers binding nandrolone, exhibiting affinity dissociation constants in the low nanomolar range. A label-free colorimetric assay based on gold nanoparticles was developed using one of these novel aptamers for the detection of nandrolone and/or its metabolites. The assay could be deployed for the rapid, on-site, facile and cost-effective screening of samples and provide qualitative visual results with a red to purple/blue color change being indicative of a positive result. [Display omitted] • Selection of novel aptamers binding to nandrolone by sepharose-SELEX. • High binding affinity of the selected aptamers demonstrated with different assays. • Development of a colorimetric gold nanoparticles-aptamer assay for nandrolone. • No cross-reactivity of the assay with endogenous steroids. • Use for screening suspicious samples for presence of nandrolone and its metabolites. [ABSTRACT FROM AUTHOR]

[Display omitted] • Boronic acid modification of C. vulgaris improves the crosslinking with redox polymer. • The bioanode's action spectrum confirms the photosystems as electron source. • Scanning photoelectrochemical microscopy suggests O 2 consumption upon illumination. • The bioanode is coupled to a bilirubin oxidase biocathode for a proof-of-concept biophotovoltaic cell. Green microalgae are gaining attention in the renewable energy field due to their ability to convert light into energy in biophotovoltaic (BPV) cells. The poor exogenous electron transfer kinetics of such microorganisms requires the use of redox mediators to improve the performance of related biodevices. Redox polymers are advantageous in the development of subcellular-based BPV devices by providing an improved electron transfer while simultaneously serving as immobilization matrix. However, these surface-confined redox mediators have been rarely used in microorganism-based BPVs. Since electron transfer relies on the proximity between cells and the redox centres at the polymer matrix, the development of molecularly tailored surfaces is of great significance to fabricate more efficient BPV cells. We propose a bioanode integrating Chlorella vulgaris embedded in an Os complex-modified redox polymer. Chlorella vulgaris cells are functionalized with 3-aminophenylboronic acid that exhibits high affinity to saccharides in the cell wall as a basis for an improved integration with the redox polymer. Maximum photocurrents of (5 ± 1) µA cm−2 are achieved. The developed bioanode is further coupled to a bilirubin oxidase-based biocathode for a proof-of-concept BPV cell. The obtained results encourage the optimization of electron-transfer pathways toward the development of advanced microalgae-based biophotovoltaic devices. [ABSTRACT FROM AUTHOR]

Mycotoxins are toxic compounds produced by fungi, which represent a risk to the food and feed supply chain, having an impact on health and economies. A high percentage of feed samples have been reported to be contaminated with more than one type of mycotoxin. Systematic, cost-effective and simple tools for testing are critical to achieve a rapid and accurate screening of food and feed quality. In this review, we describe the various aptamers that have been selected against mycotoxins and their incorporation into optical and electrochemical aptasensors, outlining the strategies exploited, highlighting the advantages and disadvantages of each approach. The review also discusses the different materials used and the immobilization methods employed, with the aim of achieving the highest sensitivity and selectivity. [Display omitted] • Review of aptasensors for the detection of mycotoxins. • Detection of Patulin, T-2 toxin, Aflatoxin B1, Aflatoxin B2, Zearalenone, Fumonisin B1, Ochratoxin. • Examples of optical and electrochemical aptasensors as well as lateral flow assays. • Presentation of different materials and immobilization approaches for aptasensor development. [ABSTRACT FROM AUTHOR]

The development of a gold nanoparticle aptamer assay is persued for rapid and sensitive determination of histamine in foodstuffs, which could be deployed for on-site use. The assay is based on a histamine-specific aptamer and gold nanoparticles and the salt-induced aggregation of the particles in the presence of histamine indicated by the color change from red to blue. Gold nanoparticle size, salt type, and concentration as well as aptamer concentration were optimized, and using optimum conditions, a limit of detection of 8 nM (~ 0.05 mg/kg) was obtained. Finally, the aptamer AuNP assay was applied to the determination of histamine in quality control fish samples. The histamine levels of these samples had previously been determined using HPLC and commercial ELISA kits by numerous independent laboratories and a good correlation was obtained. The developed AuNP assay is rapid, sensitive, and reproducible. [ABSTRACT FROM AUTHOR]

Sensitive, specific, rapid, inexpensive and easy-to-use nucleic acid tests for use at the point-of-need are critical for the emerging field of personalised medicine for which companion diagnostics are essential, as well as for application in low resource settings. Here we report on the development of a point-of-care nucleic acid lateral flow test for the direct detection of isothermally amplified DNA. The recombinase polymerase amplification method is modified slightly to use tailed primers, resulting in an amplicon with a duplex flanked by two single stranded DNA tails. This tailed amplicon facilitates detection via hybridisation to a surface immobilised oligonucleotide capture probe and a gold nanoparticle labelled reporter probe. A detection limit of 1 × 10−11 M (190 amol), equivalent to 8.67 × 105 copies of DNA was achieved, with the entire assay, both amplification and detection, being completed in less than 15 minutes at a constant temperature of 37 °C. The use of the tailed primers obviates the need for hapten labelling and consequent use of capture and reporter antibodies, whilst also avoiding the need for any post-amplification processing for the generation of single stranded DNA, thus presenting an assay that can facilely find application at the point of need. [ABSTRACT FROM AUTHOR]