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Histamine is a heterocyclic amine shaped by decarboxylation of the histidine. It is a compound that lack chromophore and involatile. However, the detection of histamine is imperative due to the characteristic of histamine has given several disadvantages in food industry. This paper describes methods for histamine detection by employing high performance liquid chromatography and gas chromatography. The derivatization techniques required for both methods in order to increase the sensitivity of chromatography analysis. Two derivatizing agents were applied in this study such as 9-flourenilmethyl chloroformate (FMOC – Cl) for HPLC analysis whereas for GC analysis a N,O-bis (trimethylsilyl)acetamide (BSA) was used. Method validation was in accordance to Commission Decision 657/2002/CE. The validation of specificity, linearity, precision, accuracy, detection limit and quantitation limit results indicate that the methods were acceptable. The linear range for both methods were at 0.16 – 5.00 µg∙mL-1. The determination of histamine using GC showed the superiority of this instrument compared to HPLC. Method applicability was also checked on real sample namely mackerel in order to acquire a satisfactory recovery for both methods.

Histamine is an important substance that can be applied as a parameter for allergic reactions and food freshness. This study develops a method to produce a histamine sensor based on electrodes modified using polyurethane-LiClO

Optical biosensor for the detection of formaldehyde has been developed based on the transparent enzymatic stacked membranes system on the glass substrate, and employing optical absorption transducer with H+ ion-selective Nile Blue chromoionophore (NBCM) dye-doped methacrylic acrylic (MB28) copolymer membrane as the optode membrane. Alcohol oxidase (AOx) enzymes were entrapped within the biocompatible sol–gel matrix and deposited on top of the pH optode membrane. As the uppermost catalytic membrane catalyzes the oxidative conversion of formaldehyde to formic acid and hydrogen peroxide, the immobilized NBCM undergoes protonation reaction and forms HNBCM+, the dark blue ion-chromoionophore complex via H+ ion transfer reaction within the soft and flexible MB28 polymeric membrane. This rendered the enzymatic optode membrane absorbed a high yellow light intensity from the light source and exhibited maximum absorption peaks at 610 and 660 nm. Optical evaluation of formaldehyde by means on UV–vis absorption transduction of the enzymatic stacked membranes demonstrated rapid response time of 10 min with high sensitivity, good linearity and high reproducibility across a wide formaldehyde concentration range of 1 × 10−3–1 × 103 mM (R2 = 0.9913), and limit of detection (LOD) at 1 × 10−3 mM, which could be useful for formaldehyde assay in industrial, agricultural, environmental, food and beverages as well as medical samples. The formaldehyde concentration in snapper fish, pomfret fish and threadfin fish samples determined by the proposed optical enzymatic biosensor were very much close to the formaldehyde concentration values determined by the UV–vis spectrophotometric NASH standard method based on the statistical t-test. This suggests that the optical biosensor can be used as a reliable method for quantitative determination of formaldehyde levels in food samples.

Early bacterial infection (BI) identification in resource-limiting Emergency Departments (ED) is challenging, especially in low- and middle-income counties (LMIC). Misdiagnosis predisposes to antibiotic overuse and propagates antimicrobial resistance. This study evaluates new emerging biomarkers, secretory phospholipase A2 group IIA (sPLA2-IIA) and compares with other biomarkers on their performance characteristic of BI detection in Malaysia, an LMIC. A prospective cohort study was conducted involving 151 consecutive patients admitted to the ED. A single measurement was taken upon patient arrival in ED and was analysed for serum levels of sPLA2-IIA, high-sensitive C-reactive protein (CRP), procalcitonin (PCT), neutrophil percentage (N%), and lactate. All biomarkers’ performance was compared for the outcomes using area under the receiver operating characteristic curve (AUROC), sensitivity, and specificity. The performance of sPLA2-IIA (AUROC 0.93 [95% CI: 0.89–0.97]; Sn 80% [95% CI: 72–87]; Sp 94% [95% CI: 81–89]) was the highest among all. It was comparable with high-sensitive CRP (AUROC 0.93 [95% CI: 0.88–0.97]; Sn 75% [95% CI: 66–83]; Sp 91 [95% CI: 77–98]) but had a higher Sn and Sp. The sPLA2-IIA was also found superior to N%, PCT, and lactate. This finding suggested sPLA2-IIA was recommended biomarkers for BI detection in LMIC.

An optical genosensor based on Schiff base complex (Zn2+ salphen) DNA label and acrylic microspheres (AMs) as polymer support of the capturing DNA probe (cpDNA) was developed for dengue virus serotype 2 (DEN-2) detection via reflectance spectrophotometric method. The solid-state optical DNA biosensor showed high selectivity and specificity up to one-base mismatch in the target DNA sequence owing to the salphen chemical structure that is rich in localized electrons, and allowed π-π stacking interaction between stacked base pairs of double-stranded DNA (dsDNA). The reflectometric DNA microsensor demonstrated a broad linear detection range towards DEN-2 DNA from 1 × 10–15 M to 1 × 10−3 M with a low limit of detection (LOD) obtained at 1.21 × 10–16 M. The DNA biosensor gave reproducible optical response with a satisfactory relative standard deviation (RSD) at 3.1%, (n = 3), and the reflectance response was stable even after four regeneration cycles of the DNA biosensor. The optical genosensor was proven comparable with standard reverse transcription polymerase chain reaction (RT-PCR) in detecting DEN-2 genome acquired from clinical samples of serum, urine and saliva of dengue virus infected patients under informed consent. The developed reflectometric DNA biosensor is advantageous in offering an early DEN-2 diagnosis, when fever symptom started to manifest in patient.

An optical biosensor employing immobilized haloalkane dehalogenase (HLD), the halide degrading enzyme for the detection of halogenated organic in environmental water and drinking water samples was developed. The enzymatic biosensor was fabricated by incorporating H+ ion selective chromoionophore ETH5294 and HLD enzyme in a stacked chitosan films system on a glass slide. Hydrolytic dehalogenation of dichloroethane (DCA) by the carbon-halide degrading HLD enzyme resulting in the release of a halogen, a proton and a primary alcohol. The halocarbon concentration was optically transduced by the pH transducer layer as a result of protonation reaction of the chromoionophore pH indicator dye embedded in the underneath layer. The resulting colour change of the protonated chromoionophore was measured by fiber optic reflectance spectrophotometry method. Under optimized conditions the detection limit of the proposed reflectance-based enzymatic biosensor membrane was estimated to be 1 mg L−1 with a wide dynamic linear concentration range of 5–60 mg L−1 DCA (R2 = 0.9792) and satisfactory reproducibility within the relative standard deviation (RSD) range of 3.4–4.3%. Validation test demonstrated that the optical halocarbon biosensor could be a promising tool for rapid (6 min) in situ and direct evaluation of organohalide in river water, tap water and bottled water samples without any sample pre-treatment or extraction steps.

An amperometric DNA biosensor was developed based on a DNA quantification concept involving the adsorption behavior of anthraquinone monosulphonic acid (AQMS). The biosensor was built from a carbon pasted screen-printed electrode coated with silica nanospheres and gold nanoparticles. Silica nanospheres of 65–84 nm were synthesized via sonication and its surface further modified with amine group. Aminated silica nanospheres immobilize amine-functionalized DNA probe covalently via glutaraldehyde linkers while gold nanoparticles used as an effective electron transfer agent. Anionic AQMS can physically adsorb onto cationic aminated silica nanospheres, and the total AQMS adsorption will be reduced if hybridization occurs. Hence, an increasing amount of hybridized DNA cause a declination in differential pulse voltammetric current signal of AQMS at −0.50 V. The biosensor yielded a linear response range of 10−9–0.5 μM (R2 = 0.97) towards DNA target and showed negligible response to mismatched and noncomplemetary DNA. The fabricated DNA biosensor as an early detection and possible noninvasive method for clinical and medical use was successfully performed; with the detection of synthetic DNA target and cDNA that were reverse-transcripted from dengue virus RNA.

A reflectometric biosensor for enzymatic determination of halogenated organic pollutant in environmental water sample was developed. Polyacrylate microspheres modified with succinimide functional groups were employed as the substrate matrix for covalent immobilization of haloalkane dehalogenase (DhlA) enzyme, and ETH5294 Nile Blue chromoionophore (NBC) pH dye was physically immobilized on the acrylic micromatrix to function as an optical proton sensor. The hydrolytic dehalogenation of halocarbon catalyzed by the immobilized DhlA resulting in the release of a halogen and a proton, which protonated the immobilized NBC proton indicator, and a colour change of the biosensor from violet to blue was measured with a reflectance spectrophotometer for indirect quantification of the halogenated hydrocarbon concentration. The enzymatic halocarbon reflectance biosensor exhibited a dynamic linear response range of 1–30 mg L−1 1,2-dichloroethane (DCA) (R2 = 0.9762) with a detection limit of 0.3 mg L−1. The proposed enzymatic biosensor gave rapid response, within 2 min, towards the detection of 50 mg L−1 DCA at 662 nm, and demonstrated stable response up to 6 days of storage period at 4 °C and pH 8.0. Validation between the developed biosensor with standard gas chromatography–electron capture detector (GC-ECD) showed that both methods have a comparable accuracy in detecting halocarbon species.

Ferrocene or ferrocenium has been widely studied in the field of organometallic complexes because of its stable thermodynamic, kinetic and redox properties. Novel hexaferrocenium tri[hexa(isothiocyanato)iron(III)]trihydroxonium (HexaFc) complex was the product from the reaction of ferrocene, maleic acid and ammonium thiocyanate and was confirmed by elemental analysis CHNS, FTIR and single crystal X-ray crystallography. In this study, HexaFc was used for the first time as an electroactive indicator for porcine DNA biosensor. The UV–Vis DNA titrations with this compound showed hypochromism and redshift at 250 nm with increasing DNA concentrations. The binding constant (Kb) for HexaFc complex towards CT-DNA (calf-thymus DNA) was 3.1 × 104 M−1, indicated intercalator behaviour of the complex. To test the usefulness of this complex for DNA biosensor application, a porcine DNA biosensor was constructed. The recognition probes were covalently immobilised onto silica nanospheres (SiNSs) via glutaraldehyde linker on a screen-printed electrode (SPE). After intercalation with the HexaFc complex, the response of the biosensor to the complementary porcine DNA was measured using differential pulse voltammetry. The DNA biosensor demonstrated a linear response range to the complementary porcine DNA from 1 × 10−6 to 1 × 10−3 µM (R2 = 0.9642) with a limit detection of 4.83 × 10−8 µM and the response was stable up to 23 days of storage at 4 °C with 86% of its initial response. The results indicated that HexaFc complex is a feasible indicator for the DNA hybridisation without the use of a chemical label for the detection of porcine DNA.

Abundant of preparatory works have recognized that fluorescent sensors based on 8-aminoquinoline are popular tools to detect Zn2+ ions in environmental and biological applications. Along with these studies, researchers started to introduce a variety of carboxamido group into an 8-aminoquinoline molecule in forming 8-amidoquinoline derivatives. Therefore, this systematic review aims to introduce a general overview of the fluorophore 8-aminoquinoline as Zn2+ receptors and to provide comparisons of collected studies that related to 8-amidoquinoline derivatives as fluorophore probe of the sensor. According to PRISMA systematic searches strategy, 13 articles were analyzed for trends, research designs, results and discussion, subject samples, and remarks or conclusions. We found cross-sectional studies with four aspects in zinc sensing that have been targeted; binding studies via titration, detection's limit, interferences studies, and validation of the study. Hence, this paper also included assessments of those criteria and the trends of development of 8-amidoquinoline derivatives based-zinc fluorescent chemosensor. It also showed that most of the researches conducted in China. In conclusion, this study identified various research designs of fluorescent chemosensors based on 8-amidoquinoline prolong with the effectiveness and potential as a recognition probe to assist the detection of zinc. Hence, elucidation of those derivatives essential to be explored because more studies are needed to improve the sensing criteria of the zinc sensor

Carrageenans are linear sulphated polysaccharides that are commonly added into confectionery products but may exert a detrimental effect to human health. A new and simpler way of carrageenan determination based on an optical sensor utilizing a methylcellulose/poly(n-butyl acrylate) (Mc/PnBA) composite membrane with immobilized methylene blue (MB) was developed. The hydrophilic Mc polymer membrane was successfully modified with a more hydrophobic acrylic polymer. This was to produce an insoluble membrane at room temperature where MB reagent could be immobilized to build an optical sensor for carrageenan analysis. The fluorescence intensity of MB in the composite membrane was found to be proportional to the carrageenan concentrations in a linear manner (1.0–20.0 mg L−1, R2 = 0.992) and with a detection limit at 0.4 mg L−1. Recovery of spiked carrageenan into commercial fruit juice products showed percentage recoveries between 90% and 102%. The optical sensor has the advantages of improved sensitivity and better selectivity to carrageenan when compared to other types of hydrocolloids. Its sensitivity was comparable to most sophisticated techniques for carageenan analysis but better than other types of optical sensors. Thus, this sensor provides a simple, rapid, and sensitive means for carageenan analysis.

Graphene decorated with graphitic nanospheres functionalized with pyrene butyric acid (PBA) is used for the first time to fabricate a DNA biosensor. The electrode was formed by attaching a DNA probe onto PBA, which had been stacked onto a graphene material decorated with graphene nanospheres (GNSs). The nanomaterial was drop-coated onto a carbon screen-printed electrode (SPE) to create the GNS-PBA modified electrode (GNS-PBA/SPE). A simple method was used to produce GNS by annealing graphene oxide (GO) solution at high temperature. Field emission scanning electron micrographs confirmed the presence of a spherical shape of GNS with a diameter range of 40–80 nm. A stable and uniform PBA-modified GNS (GNS-PBA) was obtained with a facile ultrasonication step. Thus allowing aminated DNA probes of genetically modified (GM) soybean to be attached to the nanomaterials to form the DNA biosensor. The GNS-PBA/SPE exhibited excellent electrical conductivity via cyclic voltammetry (CV) and differential pulse voltammetry (DPV) tests using potassium ferricyanide (K3[Fe(CN)6]) as the electroactive probe. By employing an anthraquinone monosulfonic acid (AQMS) redox intercalator as the DNA hybridization indicator, the biosensor response was evaluated using the DPV electrochemical method. A good linear relationship between AQMS oxidation peak current and target DNA concentrations from 1.0 × 10−16 to 1.0 × 10−8 M with a limit of detection (LOD) of less than 1.0 × 10−16 M was obtained. Selectivity experiments revealed that the voltammetric GM DNA biosensor could discriminate complementary sequences of GM soybean from non-complementary sequences and hence good recoveries were obtained for real GM soybean sample analysis. The main advantage of using GNS is an improvement of the DNA biosensor analytical performance.

A DNA micro-optode for dengue virus detection was developed based on the sandwich hybridization strategy of DNAs on succinimide-functionalized poly(n-butyl acrylate) (poly(nBA-NAS)) microspheres. Gold nanoparticles (AuNPs) with an average diameter of ~20 nm were synthesized using a centrifugation-based method and adsorbed on the submicrometer-sized polyelectrolyte-coated poly(styrene-co-acrylic acid) (PSA) latex particles via an electrostatic method. The AuNP&ndash, latex spheres were attached to the thiolated reporter probe (rDNA) by Au&ndash, thiol binding to functionalize as an optical gold&ndash, latex&ndash, rDNA label. The one-step sandwich hybridization recognition involved a pair of a DNA probe, i.e., capture probe (pDNA), and AuNP&ndash, PSA reporter label that flanked the target DNA (complementary DNA (cDNA)). The concentration of dengue virus cDNA was optically transduced by immobilized AuNP&ndash, PSA&ndash, rDNA conjugates as the DNA micro-optode exhibited a violet hue upon the DNA sandwich hybridization reaction, which could be monitored by a fiber-optic reflectance spectrophotometer at 637 nm. The optical genosensor showed a linear reflectance response over a wide cDNA concentration range from 1.0 &times, 10&minus, 21 M to 1.0 &times, 12 M cDNA (R2 = 0.9807) with a limit of detection (LOD) of 1 &times, 29 M. The DNA biosensor was reusable for three consecutive applications after regeneration with mild sodium hydroxide. The sandwich-type optical biosensor was well validated with a molecular reverse transcription polymerase chain reaction (RT-PCR) technique for screening of dengue virus in clinical samples, e.g., serum, urine, and saliva from dengue virus-infected patients under informed consent.

A novel label-free electrochemical DNA biosensor was constructed for the determination of Escherichia coli bacteria in environmental water samples. The aminated DNA probe was immobilized onto hollow silica microspheres (HSMs) functionalized with 3-aminopropyltriethoxysilane and deposited onto a screen-printed electrode (SPE) carbon paste with supported gold nanoparticles (AuNPs). The biosensor was optimized for higher specificity and sensitivity. The label-free E. coli DNA biosensor exhibited a dynamic linear response range of 1 &times, 10&minus, 10 &micro, M to 1 &times, 5 &micro, M (R2 = 0.982), with a limit of detection at 1.95 &times, 15 &micro, M, without a redox mediator. The sensitivity of the developed DNA biosensor was comparable to the non-complementary and single-base mismatched DNA. The DNA biosensor demonstrated a stable response up to 21 days of storage at 4 ℃ and pH 7. The DNA biosensor response was regenerable over three successive regeneration and rehybridization cycles.

Biosensor optik berasaskan hemoglobin (Hb) terpegun pada mikrosfera poli(n-butil akrilat-co-N-akriloksisuksinimida) [poli(nBA-NAS)] telah dibangunkan bagi mengesan kepekatan ion nitrit (NO2-). Kompleks HEM ferum dalam Hb memangkinkan tindak balas penurunan ion NO2- kepada nitrik oksida (NO) lalu bergabung dengan deoksihemoglobin (HbFe2+) membentuk kompleks ferum-nitrosil-hemoglobin (HbFe2+-NO) yang berwarna hijau kekuningan. Spektrofotometer pantulan gentian optik digunakan untuk memantau kepekatan ion NO2- secara kuantitatif berdasarkan perubahan warna Hb terpegun pada mikrosfera poliakrilat daripada perang kemerahan ke hijau kekuningan pada panjang gelombang pantulan maksimum 668 nm. Pencirian terhadap biosensor nitrit reflektometrik melibatkan ujian kesan pH, kesan kepekatan Hb, julat rangsangan linear, kebolehasilan, jangka hayat dan kesan gangguan ion telah dijalankan. Biosensor ion NO2- optik terbangun memaparkan julat linear dinamik daripada 5 hingga 50 mg mL-1 (R2=0.9894) pada pH7.0 dengan had pengesanan (LOD) sebanyak 3.3 mg mL-1 dan nilai sisihan piawai relatif (RSD) kebolehasilan biosensor sebanyak 5.8%. Jangka hayat biosensor optik nitrit tersebut adalah selama 36 hari dan majoriti ion asing yang sering wujud bersama ion NO2- dalam sampel air semula jadi tidak menunjukkan kesan gangguan yang bererti terhadap penentuan ion NO2- menggunakan biosensor optik terbangun kecuali ion Hg2+, Ag+, Br- dan S2-.

A toxicity electrochemical DNA biosensor has been constructed for the detection of carcinogens using 24 base guanine DNA rich single stranded DNA, and methylene blue (MB) as the electroactive indicator. This amine terminated ssDNA was immobilized onto silica nanospheres and deposited on gold nanoparticle modified carbon-paste screen printed electrodes (SPEs). The modified SPE was initially exposed to a carcinogen, followed by immersion in methylene blue for an optimized duration. The biosensor response was measured using differential pulse voltammetry. The performance of the biosensor was identified on several anti-cancer compounds. The toxicity DNA biosensor demonstrated a linear response range to the cadmium chloride from 0.0005 ppm to 0.01 ppm (R2 = 0.928) with a limit of detection at 0.0004 ppm. The biosensor also exhibited its versatility to screen the carcinogenicity of potential anti-cancer compounds.

A microspheres-based microbial optosensor for NO 2 − ion quantitation was constructed by using immobilized Raoutella planticola ( R. planticola ), the bacterium expressing NAD(P)H nitrite reductase (NiR) enzyme, which was isolated from local edible bird’s nest (EBN) via microbial technique. The whole cells and the lipophilic Nile Blue chromoionophore (NBC) were physically adsorbed on the self-adhesive photocurable poly( n -butyl acrylate-co- N -acryloxysuccinimide) [poly(nBA-NAS)] microspheres, whilst the reduced co-enzyme NAD(P)H was covalently immobilized on the succinimide-functionalized acrylic microspheres via peptide link to produce a reagentless nitrite biosensing system. As the microbial bio-optode responded to nitrite through colour change from blue to pink, a facile reflectometric approach was adopted to measure reflectance intensity at 639 nm, before and after reaction with nitrite at optimum pH 8. The optosensor could quantify NO 2 − ion concentration within a dynamic linear response range of 0.5–400 mg L −1 with a limit of detection (LOD) of 0.2 mg L −1 . The large surface area to volume ratio of the acrylic microspheres allowed solid-state diffusional mass transfer of the substrate to occur at micro-bio-optode surface, and an equilibrium response was achieved within 5 min. The practical feasibility of using the bio-optode for nitrite assay in food matrix sample showed good agreement with standard ion chromatography method.

An electrochemical DNA biosensor for DNA determination of genetically modified (GM) soybean (CaMV 35S target genes) was developed utilizing a new detection concept based on the adsoption of anthraquinone‐2‐sulphonic acid (AQMS) on the reduced graphene oxide nano‐particles (rGO) during DNA hybridization events. The aminated DNA probe for CaMV 35S was immobilized onto poly(n‐butyl acrylate) film modified with succinimide functional groups [poly(nBA‐NAS)] via peptide covalent bond. Nanosheets of rGO were entrapped in the poly(nBA‐NAS) film to form a conducting [poly(nBA‐NAS)‐rGO] film of the DNA biosensor. Besides facilitating the electron transfer reactions, the rGO also functioned as an adsorbent for AQMS. The sensing mechanism of the proposed DNA biosensor involved measuring the oxidation current of the AQMS adsorbed on the electrode surface at −0.50 V using differential pulse voltammetry (DPV) before and after a DNA hybridization event. Under optimum conditions, the DNA biosensor demonstrated a linear proportionality between AQMS oxidation signal and logarithm cDNA concentration from 1.0×10−15 M to 1.0×10−8 M target DNA with a detection limit of 6.3×10−16 M. The electrochemical DNA biosensor possessed good selectivity and a shelf life of about 40 days with relative standard deviation of reproducibility obtained in the range of 3.7–4.6% (n=5). Evaluation of the DNA biosensor using GM soybean DNA extracts showed excellent recovery percentages of 97.2–104.0.

Artificial Neural Network (ANN) had been used in this study to extend the response range of the pH indicator. The input from absorbance values of the absorbance spectra of chlorophenol red at different pH was used to train the ANN. During the training process, the coefficient values of the ANN will be adjusted to obtain the desire output. In this research, back propagation algorithm had been used for optimizing the response range of the pH indicator chlorophenol red in solution. The result indicates that the use of ANN enable the pH response range to be extended from 4.8-6.8 to 1.0-10.0.

Multi-wall carbon nanotubes (MWCNTs) were modified to design a new DNA biosensor. Functionalized MWCNTs were equipped with gold nanoparticles (GNPs) (~15nm) (GNP-MWCNTCOOH) to construct DNA biosensors based on carbon-paste screen-printed (SPE) electrodes. GNP attachment onto functionalized MWCNTs was carried out by microwave irradiation and was confirmed by spectroscopic studies and surface analysis. DNA biosensors based on differential pulse voltammetry (DPV) were constructed by immobilizing thiolated single-stranded DNA probes onto GNP-MWCNTCOOH. Ruthenium (III) chloride hexaammoniate [Ru(NH3)6,2Cl-] (RuHex) was used as hybridization redox indicator. RuHex and MWCNT interaction was low in compared to other organic redox hybridization indicators. The linear response range for DNA determination was 1×10-21 to 1×10-9M with a lower detection limit of 1.55×10-21M. Thus, the attachment of GNPs onto functionalized MWCNTs yielded sensitive DNA biosensor with low detection limit and stability more than 30days. Constructed electrode was used to determine gender of arowana fish.

In the title compound, C14H18N2O2S, the piperidine ring has a chair conformation. Its mean plane is twisted with respect to the 4-methoxybenzoyl ring, with a dihedral angle of 63.0 (3)°. The central N—C(=S)—N(H)—C(=O) bridge is twisted with an N—C—N—C torsion angle of 74.8 (6)°. In the crystal, molecules are linked by N—H...O and C—H...O hydrogen bonds, forming chains along thec-axis direction. Adjacent chains are linked by C—H...π interactions, forming layers parallel to theacplane. The layers are linked by offset π–π interactions [intercentroid distance = 3.927 (3) Å], forming a supramolecular three-dimensional structure.

An ultrasensitive electrochemical biosensor for the determination of pathogenic Vibrio cholerae (V. cholerae) DNA was developed based on polystyrene-co-acrylic acid (PSA) latex nanospheres-gold nanoparticles composite (PSA-AuNPs) DNA carrier matrix. Differential pulse voltammetry (DPV) using an electroactive anthraquninone oligonucleotide label was used for measuring the biosensor response. Loading of gold nanoparticles (AuNPs) on the DNA-latex particle electrode has significantly amplified the faradaic current of DNA hybridisation. Together with the use of a reported probe, the biosensor has demonstrated high sensitivity. The DNA biosensor yielded a reproducible and wide linear response range to target DNA from 1.0 × 10−21 to 1.0 × 10−8 M (relative standard deviation, RSD = 4.5%, n = 5) with a limit of detection (LOD) of 1.0 × 10−21 M (R 2 = 0.99). The biosensor obtained satisfactory recovery values between 91 and 109% (n = 3) for the detection of V. cholerae DNA in spiked samples and could be reused for six consecutive DNA assays with a repeatability RSD value of 5% (n = 5). The electrochemical biosensor response was stable and maintainable at 95% of its original response up to 58 days of storage period.

The attractive structural and mechanical properties of cellulose substrates (paper, cloth, and thread), including passive fluid transport, biocompatibility, durability, and flexibility, have attracted researchers in the past few decades to explore them as alternative microfluidic platforms. The incorporation of electrochemical (EC) sensing broadened their use for applications such as clinical diagnosis, pharmaceutical chemical analyses, food quality, and environmental monitoring. This article provides a review on the microfluidic devices constructed on paper, cloth, and thread substrates. It begins with an overview on paper-based microfluidic devices, followed by an in-depth review on the various applications of EC detection incorporated on paper-based microfluidic devices reported to date. The review on paper-based microfluidic devices attempts to convey a few perspective directions that cloth- and thread-based microfluidic devices may take in its development. Finally, the research efforts on the development and evaluation, as well as current limitations of cloth- and thread-based microfluidic devices are discussed. Microfluidic devices constructed on paper, cloth, and thread substrates are still at an early development stage (prototype) requiring several improvements in terms of fabrication, analytical techniques, and performance to become mature platforms that can be adapted and commercialized as real world products. However, they hold a promising potential as wearable devices.

A solid-state DNA optode sensor has been developed based on the employment of glutaraldehyde (GD)-activated aminated silica nanoparticles (SiO2NPs-NH2) DNA carrier matrix, and the newly synthesized yellowish N,N’-bis-5-(hydroxysalicylidene)phenylene-diamine-zinc(II) (i.e. the Zn salphen complex) oligonucleotide label. Some three Schiff base complexes with three different transition metal ions (Zn2+, Ni2+, Cu2+) were synthesized through a simple one-pot reaction (5 h), and characterized by their physical and chemical properties based on FTIR, NMR and ESI–MS analyses. Due to the square planar geometry and aromatic ring structured characteristics of the metal complex intercalators, they could intercalate between DNA bases via π-π stacking interaction, and rendered a yellowish pink hue on the DNA biosensor surface. Reflectometric optimization revealed high selectivity of the nanosilica-based DNA biosensor in the detection of dengue serotype 2 DNA, which capable of discriminating even a single nucleotide mismatch. The optical DNA biosensor demonstrated a linear reflectance response between 1.0 × 10−15 M and 1.0 × 10−11 M cDNA (R2 = 0.9975) with a fast DNA hybridization time of 30 min and a limit of detectable (LOD) DNA concentration as low as 1 zM. In addition, this biosensor showed high shelf life stability with a 20-day operational duration and reusable for five consecutive DNA testings. The proposed optical DNA biosensor offers biosensing performance far superior to that of previously reported electrochemical DNA biosensor for early diagnosis of dengue infection with respect to dynamic linear range, LOD and response time.

The preparation and characterization of a DNA biosensor based on kappa-carrageenan-polypyrrole-gold nanoparticles (KC-PPy-AuNPs) nano-biocomposite is reported to demonstrate an application for gender classification of Arowana fish. Immobilization of the thiol modified Arowana fish ssDNA probe sequence was successfully carried out via covalent attachment to the gold (Au) on the surface of the nano-biocomposite membrane. Under optimum conditions, the DNA biosensor showed a short immobilization and hybridization time with high sensitivity for monitoring the target DNA sequence. The hybridization with the target DNA was determined by monitoring the redox current of anthraquinone-2-sulfonic acid monohydrate sodium salt (AQMS) using differential pulse voltammetry (DPV). The DNA hybridization response gradually increased with increasing concentrations of target DNA from 5 × 10 −18 to 5 × 10 −12 M and the limit of detection was below 5 × 10 −18 M. The application of the DNA biosensor for gender classification of Arowana fish was demonstrated.

The evaluation of chilli hotness using amperometric capsaicin biosensor-based enzyme that was immobilized covalently to the surface of modified acrylic microspheres is the first of its kind presented in this work. The immobilization of enzyme covalently to the surface of microspheres via succinimide groups prevented the leaching of the enzyme. The enzymatic reaction between horseradish peroxidase-capsaicin in the presence of hydrogen peroxide, which was mediated by vinyl ferrocene, enabled the current measurement at a low potential (0.22 V). Besides, the pungency level of the chilli that was proportional to the capsaicin concentration was measured using this method. This biosensor gave a linear response range towards capsaicin from 0.75–24.94 μM (R2 = 0.992) with a detection limit at 0.39 μM. Moreover, the relative standard deviation (RSD) for reproducibility study was 8.2% (n = 7). Therefore, this biosensor was successfully applied for evaluation of chilli hotness in chilli sample, as well as in comparison with a standard method that employed the HPLC method.

A new bioanalytical method for urea determination by using the immobilized urease on the highly luminescent ZnS quantum dots (QDs), which functioned as the pH fluorescent label has been developed. Bioconjugation of ZnS QDs to urease via amide bond was performed to obtain the ZnS QDs-urease bioconjugate. Upon enzymatic hydrolysis of urea by the immobilized urease, a pH change to a more alkaline condition has led to the deprotonation of ZnS QDs, and an increase in the fluorescence intensity can be observed. The fluorescence intensity of the urease conjugated ZnS QDs changed linearly with the urea concentrations between 4 × 10 −9 M and 4 × 10 −3 M (R 2 = 0.992) at pH 6 with a calibration sensitivity of 179.46 intensity/decade. No noticeable influence by the Ca 2+ , Mg 2+ , K + and Na + ions on the response of the fluorescent pH bioprobe. Urea determination in soil sample by using the urea bioprobe was in good agreement with the standard DMAB (p-dimethylaminobenzaldehyde) UV–vis spectrophotometric method. By employing the strategy of ZnS QDs-urease bioconjugation, the stable covalent link between the two substances has appeared to widen the dynamic range and lower the detection limit for urea compared to free enzyme and QDs in solution for bioassay of urea concentration.

The northeast monsoon which occurs from November to March carries heavy rainfall which always result in flood especially to the east coast of Peninsular Malaysia. Pahang was one of the state that severely affected by this flood. Although the heavy rain is the main driver of the flood but human being cannot ignore the other flood drivers especially the river and its nearby environment circumstance which regard the flood event. The objective of this study was to determine the other flood drivers especially the river and its nearby environment circumstance which regard the flood event. The methodologies used in this study involved data collection through literature reviews and flood reports from Drainage and Irrigation Department (DID) and districts and interview to gather more information and verify the issues and other related drivers. The possible drivers of flooding in Pahang that occurred are as follows : 1) High rain intensity (>60 mm/hour, 200 – 450 mm/day) at the upstream that increases the quantity of water in the river and causes it to overflow 2) Water from area that has no drainage connection with the river (lowland, recessed and swamp area) was also flowing out and contributed to the flood 3) The size of the irrigation system is insufficient to bear the water flow rate and the tributary network is unable to withstand the large runoff 4) Increased reclaim of wetland area for development that causes irrigation system to be narrowed and obstructed for the water to flowing in to the tributaries 5) Prevalent forest clearing and logging activity increased the water non-absorbent area 6) Ground cutting for development purpose decreased the rain water absorption into the ground and increased surface water runoff, thus causes the watershed area decrease in its ability to hold water 7) Shallow estuary caused by high sedimentation from various activities leads to slow water conduction flowing from flood area to the sea 8) Most residential area are located at lowland and flood plain region coupled with bad irrigation system especially in big residential area, thus increased the flood risk. Each possible driver of flooding in Pahang that occurred in 2014 has to be discussed further in term of the responsible stakeholders who should involve in the management and maintenance. The heavy rainfall from northeast monsoon which was the main flood driver cannot be avoided but some flood drivers especially the river and its nearby environment that may contribute to higher magnitude of flood can be fixed and controlled by human

The Pahang river basin is the largest river basin in the Pahang State, with total catchment area covering 29300km2. Floods of Pahang river basin have become an annual natural disaster event where all the stakeholders have their own responsibility and parts to take care of it. This study has focused on stakeholders’ response and perspectives to verify the issues on flood disaster of Pahang river basin. The methodology used in this study is the stakeholders’ consultation workshop. This workshop was conducted by involving the stakeholders’ representatives from various agencies. The result from this workshop has revealed the response and perspectives based on the important parts of each stakeholder to face the flood event that occurred in Pahang river basin. Besides, the issues aroused from this workshop have shown the stakeholders’ response and their perspectives on how to reduce the impacts on flood disaster of Pahang river basin. According to the workshop, there are two factors contribute to flood event which are the heavy rainfall and the arising of water level. The causes of these two factors are the reason that we need to involve all aspects in order to reduce the impact of flood disaster. The aspects are to identify the frequent problems to arise during flood event, to improvise the operating systems such as flood forecasting systems, telemetric systems and hydrology system, the plans of each stakeholder on how to cooperate and reduce the impact as one team, to provide the proper flood maps at the study level and to review and verify what are the communities’ complaints and perspectives as they also one of the victims. This study had discussed the proposed actions need to be taken according to the stakeholders’ response and perspectives. The overflow of river water had caused by the low absorption of rainfall from forest which due to deforestation and loggings. The high water level also caused by the high sedimentations which contributed by these activities. The law enforcement with more stringent need to be done on these matters. Besides, the operating systems need to be improvised and added as these approaches can help in reducing the impact of flood events. The flood maps should be provided at study level to identify and produce a valuable case study. Stakeholders’ consultations and involvement are the keys to improvise the weakness on how to cope with the floods event from the early stage. The proposal and implementations of the development should be done by involving the stakeholders’ response and perspectives in any disaster