Displaying publications 1 - 20 of 31 in total

  1. Pandian K, Mohana Soundari D, Rudra Showdri P, Kalaiyarasi J, Gopinath SCB
    Mikrochim Acta, 2019 01 07;186(2):54.
    PMID: 30618010 DOI: 10.1007/s00604-018-3117-7
    Differential pulse voltammetry (DPV) was employed for the determination of caffeic acid (CA) in acidic solutions by using a glassy carbon electrode (GCE) modified with a chitosan-protected nanohybrid composed of carbon black and reduced graphene oxide. Electrochemical impedance spectroscopy and cyclic voltammetry were utilized to study the interfacial electron transfer on the modified GCE. Cyclic voltammetry shows that CA exhibits a reversible redox reaction with an oxidation peak at + 0.30 V (vs. Ag/AgCl) and a reduction peak at + 0.24 V in pH 3.0 solution at a scan rate of 50 mV·s-1. Under the optimized experimental conditions, the response to CA is linear in 0.3× 10-9 to 57.3 × 10-5 M concentration range. The limit of detection is 0.03 × 10-9 M (at an S/N ratio of 3), and the electrochemical sensitivity is 5.96 μA∙ μM-1∙cm-2. This sensor for CA displays better sensitivity and a response over a wider concentration range. It was applied to the determination of CA at trace levels in various (spiked) wine samples. Graphical abstract Schematic presentation of a sensitive electrochemical method for the quantitative detection of caffeic acid using chitosan protected carbon black and reduced graphene oxide. It can be used for the quantitative detection of caffeic acid in wine samples.
  2. Ahmad H, Haseen U, Umar K, Ansari MS, Ibrahim MNM
    Mikrochim Acta, 2019 08 27;186(9):649.
    PMID: 31456042 DOI: 10.1007/s00604-019-3753-6
    The authors describe a method for solvent-free mechano-chemical synthesis of a bioinspired sorbent. A 2D ultra-thin carbon sheet similar to graphene oxide was prepared using a natural waste (onion sheet). The formation of 2D carbon sheets was confirmed by Raman spectroscopy, X-ray photoelectron spectroscopy and ATR-IR. The surface morphology was characterized by field emission scanning electron microscopy and high-resolution tunneling electron microscopy. The carbon sheets were decorated with crystalline MnFe2O4 nanoparticles by solid-state reaction at room temperature. The presence of magnetic particles in the final product was confirmed by vibrating sample magnetometry and electron microscopy. The synergistic effect of carbon sheets and MnFe2O4 led to an enhanced sorption of arsenic species compared to bare carbon sheets or to MnFe2O4 nanoparticles. A column was prepared for the simultaneous preconcentration and determination of trace levels of As(III) and As(V) from water samples. The preconcentration factors are between 900 and 833 for As(III) and As(V) species, respectively. The linearity of the calibration plot ranges from 0.4-10 ng mL-1. The detection limits (at 3σ) for both As(III) and As(V) are 30 pg mL-1. The Student's t values for the analysis of spiked samples are lower than the critical Student's t values at a 95% confidence level. The recoveries from spiked water samples range between 99 and 102.8%. Graphical abstract Schematic representation of the preparation of carbon sheets similar to graphene oxide from onion sheaths after pyrolysis at 800 °C. The prepared carbon sheet-MnFe2O4 composite shows excellent arsenic sorption and preconcentration down to the pg mL-1 concentration.
  3. Ramanathan S, Gopinath SCB, Arshad MKM, Poopalan P, Anbu P
    Mikrochim Acta, 2019 07 18;186(8):546.
    PMID: 31321546 DOI: 10.1007/s00604-019-3696-y
    A genomic DNA-based colorimetric assay is described for the detection of the early growth factor receptor (EGFR) mutation, which is the protruding reason for non-small cell lung cancer. A DNA sequence was designed and immobilized on unmodified gold nanoparticles (GNPs). The formation of the respective duplex indicates the presence of an EGFR mutation. It is accompanied by the aggregation of the GNPs in the presence of monovalent ions, and it indicates the presence of an EGFR mutation. This is accompanied by a color change from red (520 nm) to purple (620 nm). Aggregation was evidenced by transmission electron microscopy, scanning electron microscopy and atomic force microscopy. The limit of detection is 313 nM of the mutant target strand. A similar peak shift was observed for 2.5 μM concentrations of wild type target. No significant peak shift was observed with probe and non-complementary DNA. Graphical abstract Schematic representation of high-specific genomic DNA sequence on gold nanoparticle (GNP) aggregation with sodium chloride (NaCl). It illustrates the detection method for EGFR mutation on lung cancer detection. Red and purple colors of tubes represent dispersed and aggregated GNP, respectively.
  4. Lee ST, Rahman R, Muthoosamy K, Mohamed NAH, Su X, Tayyab S, et al.
    Mikrochim Acta, 2019 01 09;186(2):81.
    PMID: 30627857 DOI: 10.1007/s00604-018-3194-7
    A fluorogenic probe has been developed for determination of telomerase activity using chimeric DNA-templated silver nanoclusters (AgNCs). The formation of AgNCs was investigated before (route A) and after (route B) telomerase elongation reaction. Both routes caused selective quenching of the yellow emission of the AgNCs (best measured at excitation/emission wavelength of 470/557 nm) in telomerase-positive samples. The quenching mechanism was studied using synthetically elongated DNA to mimic the telomerase-catalyzed elongation. The findings show that quenching is due to the formation of parallel G-quadruplexes with a -TTA- loop in the telomerase elongated products. The assay was validated using different cancer cell extracts, with intra- and interassay coefficients of variations of <9.8%. The limits of detection for MCF7, RPMI 2650 and HT29 cell lines are 15, 22 and 39 cells/μL. This represents a distinct improvement over the existing telomeric repeat amplification protocol (TRAP) assay in terms of time, sensitivity and cost. Graphical Abstract A method was developed using chimeric DNA-templated silver nanoclusters to detect telomerase activity directly in cell extracts. The sensitivity of this new method outperforms the traditional TRAP assay, and without the need for amplification.
  5. Amiri A, Ghaemi F, Maleki B
    Mikrochim Acta, 2019 02 01;186(3):131.
    PMID: 30707373 DOI: 10.1007/s00604-019-3246-7
    Different types of hybrid nanocomposites were prepared from a copper-based metal-organic framework (MOF-199) and graphene (Gr) or fullerene (Fl). The porosity and quality of the nanocomposites were studied by scanning electron microscopy, transmission electron microscopy and BET surface area analysis. The nanocomposites are shown to be viable sorbents for the dispersive micro solid phase extraction of polycyclic aromatic hydrocarbons (PAHs) from environmental water samples. This is due to (a) the presence of MOF-199 which leads to improved adsorption capacity, and (b) the presence of Gr or Fl on the surface of MOF-199 which enhances the interaction with PAHs. Specifically, acenaphthene, anthracene, benz[a]anthracene, fluorene, naphthalene, 2-methylnaphthalene, and pyrene were studied. A comparison of the sorbents shows MOF-199/Gr to possess the highest adsorption affinity and to be most durable, probably a result of the high porosity of graphene. Following desorption with acetonitrile, the PAHs were quantified by GC with FID detection. Under the optimum conditions, limits of detection (at an S/N ratio of 3) range from 3 to 10 pg mL-1, and the analytical ranges are linear at 0.01-100 ng mL-1 of PAHs. The relative standard deviations for five replicates at two spiking levels (0.03 and 50 ng mL-1) range from 5.0 to 7.4%. The applicability of this method was confirmed by analyzing spiked real water samples, and recoveries are between 91.9 and 99.5%. Graphical abstract Different types of the hybrid nanocomposites of the copper-based metal-organic framework MOF-199 with graphene or fullerene were synthesized and used as sorbent for the dispersive micro solid phase extraction of polycyclic aromatic hydrocarbons in environmental water samples.
  6. Ahmad H, Umar K, Ali SG, Singh P, Islam SS, Khan HM
    Mikrochim Acta, 2018 05 10;185(6):290.
    PMID: 29748777 DOI: 10.1007/s00604-018-2829-z
    A column sorbent for arsenic was obtained through immobilization of highly branched polyethylenimine (PEI) on graphene oxide (GO). The composite material enables speciation of arsenic by tuning the pH of the sample solution which governs the surface charge of the sorbent, depending on whether amino groups (-NH2) are present (at high pH) or ammonium groups (-NH3+; at low pH). The composite can be applied to improved speciation of arsenic (compared to unmodified GO). There is no need for oxidation or reduction of arsenic. A column procedure was applied for the sequestered extraction and speciation of As(III) and As(V) from environmental water samples before their determination by hydride generation-microwave induced plasma-atomic emission spectrometry. The method has a preconcentration factor of 440 for As(III) and of 400 for As(V). The limits of detection (at 3 S/N) are extremely low, being 1.8 ± 0.2 ngL-1 for As(III) and 1.3 ± 0.08 ngL-1 for As(V). This is much lower than the arsenic guideline value of 10 μgL-1 as given by the WHO. Graphical abstract Graphene oxide interconnected with polyethyleneimine has been employed for the speciation and determination of arsenic. Quantitation by atomic emission spectroscopy reveals a high preconcentration factor (440 and 400) and low LODs of 1.8 ± 0.2 and 1.3 ± 0.08 ngL-1for As(III) and As(V), respectively.
  7. Yusoff N, Rameshkumar P, Mohamed Noor A, Huang NM
    Mikrochim Acta, 2018 04 03;185(4):246.
    PMID: 29616348 DOI: 10.1007/s00604-018-2782-x
    An amperometric sensor for L-Cys is described which consists of a glassy carbon electrode (GCE) that was modified with reduced graphene oxide placed in a Nafion film and decorated with palladium nanoparticles (PdNPs). The film was synthesized by a hydrothermal method. The PdNPs have an average diameter of about 10 nm and a spherical shape. The modified GCE gives a linear electro-oxidative response to L-Cys (typically at +0.6 V vs. SCE) within the 0.5 to 10 μM concentration range. Other figures of merit include a response time of less than 2 s, a 0.15 μM lower detection limit (at signal to noise ratio of 3), and an analytical sensitivity of 1.30 μA·μM-1·cm-2. The sensor displays selectivity over ascorbic acid, uric acid, dopamine, hydrogen peroxide, urea, and glucose. The modified GCE was applied to the determination of L-Cys in human urine samples and gave excellent recoveries. Graphical abstract Spherical palladium nanoparticles (PdNPs) on reduced graphene oxide-Nafion (rGO-Nf) films were synthesized using a hydrothermal method. This nanohybrid was used for modifying a glassy carbon electrode to develop a sensor electrode for detecting L-cysteine that has fast response (less than 2 s), low detection limit (0.15 μM), and good sensitivity (0.092 μA μM-1 cm-2).
  8. Goutham S, Bykkam S, Sadasivuni KK, Kumar DS, Ahmadipour M, Ahmad ZA, et al.
    Mikrochim Acta, 2017 12 20;185(1):69.
    PMID: 29594642 DOI: 10.1007/s00604-017-2537-0
    A nanocomposite consisting of a few layers of graphene (FLG) and tin dioxide (SnO2) was prepared by ultrasound-assisted synthesis. The uniform SnO2 nanoparticles (NPs) on the FLG were characterized by X-ray diffraction in terms of lattice and phase structure. The functional groups present in the composite were analyzed by FTIR. Electron microscopy (HR-TEM and FE-SEM) was used to study the morphology. The effect of the fraction of FLG present in the nanocomposite was investigated. Sensitivity, selectivity and reproducibility towards resistive sensing of liquid propane gas (LPG) was characterized by the I-V method. The sensor with 1% of FLG on SnO2 operated at a typical voltage of 1 V performs best in giving a rapid and sensitive response even at 27 °C. This proves that the operating temperature of such sensors can be drastically decreased which is in contrast to conventional metal oxide LPG sensors. Graphical abstract Schematic of a room temperature gas sensor for liquefied petroleum gas (LPG). It is based on the use of a few-layered graphene (1 wt%)/SnO2 nanocomposite that was deposited on an interdigitated electrode (IDEs). A sensing mechanism for LPG detection has been established.
  9. Ranjani B, Kalaiyarasi J, Pavithra L, Devasena T, Pandian K, Gopinath SCB
    Mikrochim Acta, 2018 02 23;185(3):194.
    PMID: 29594516 DOI: 10.1007/s00604-018-2715-8
    A sensing device was constructed for the amperometric determination of nitrite. It is based on the use of titanium dioxide (TiO2) nanotubes template with natural fibers and carrying hemin acting as the electron mediator. A glassy carbon electrode (GCE) was modified with the hemin/TNT nanocomposite. The electrochemical response to nitrite was characterized by impedance spectroscopy and cyclic voltammetry. An amperometric study, performed at a working potential of + 0.75 V (vs. Ag/AgCl), showed the sensor to enable determination of nitrite with a linear response in the 0.6 to 130 μM concentration range and with a 59 nM limit of detection. Corresponding studies by differential study voltammetry (Ep = 0.75 V) exhibited a linear range from 0.6 × 10-6 to 7.3 × 10-5 M with a limit of detection of 84 nM. The sensing device was applied to the determination of nitrite in spiked tap and lake water samples. Graphical abstract Natural fibers templated synthesis of TNT immobilized hemin as electron transfer mediator for quantitative detection of nitrite with detection limit of 59 nM and good electrochemical sensitivity and the method can be used for quantitative determination of nitrite in water samples.
  10. Saad SM, Abdullah J, Rashid SA, Fen YW, Salam F, Yih LH
    Mikrochim Acta, 2019 11 19;186(12):804.
    PMID: 31745737 DOI: 10.1007/s00604-019-3913-8
    A fluorometric assay is described for highly sensitive quantification of Escherichia coli O157:H7. Reporter oligos were immobilized on graphene quantum dots (GQDs), and quencher oligos were immobilized on gold nanoparticles (AuNPs). Target DNA was co-hybridized with reporter oligos on the GQDs and quencher oligos on AuNPs. This triggers quenching of fluorescence (with excitation/emission peaks at 400 nm/530 nm). On introducing target into the system, fluorescence is quenched by up to 95% by 100 nM concentrations of target oligos having 20 bp. The response to the fliC gene of E. coli O157:H7 increases with the logarithm of the concentration in the range from 0.1 nM to 150 nM. The limit of detection is 1.1 ± 0.6 nM for n = 3. The selectivity and specificity of the assay was confirmed by evaluating the various oligos sequences and PCR product (fliC gene) amplified from genomic DNA of the food samples spiked with E. coli O157:H7. Graphical abstractSchematic representation of fluorometric assay for highly sensitive quantification of Escherichia coli O157:H7 based on fluorescence quenching gene assay for fliC gene of E. coli O157:H7.
  11. Mahmoudian MR, Basirun WJ, Woi PM, Hazarkhani H, Alias YB
    Mikrochim Acta, 2019 05 22;186(6):369.
    PMID: 31119482 DOI: 10.1007/s00604-019-3481-y
    The study presents the synthesis of polypyrrole-coated palladium platinum/nitrogen-doped reduced graphene oxide nanocomposites (PdPt-PPy/N-rGO NC) via direct the reduction of Pd(II) and Pt(II) in the presence of pyrrole monomer, N-rGO and L-cysteine as the reducing agent. X-ray diffraction confirmed the presence of metallic Pd and Pt from the reduction of Pd and Pt cations. Transmission electron microscopy images revealed the presence of Pd, Pt and PPy deposition on N-rGO. Impedance spectroscopy results gave a decreased charge transfer resistance due to the presence of N-rGO. The nanocomposites were synthesized with different Pd/Pt ratios (2:1, 1:1 and 1:2). A glassy carbon electrode (GCE) modified with the nanocomposite showed enhanced electrochemical sensing capability for formaldehyde in 0.1 M sulfuric acid solution. Cyclic voltammetry showed an increase in the formaldehyde oxidation peak current at the GCE modified with Pd2Pt1 PPy N-rGO. At a typical potential of 0.45 V (vs. SCE), the sensitivity in the linear segment was 345.8 μA.mM -1. cm-2. The voltammetric response was linear between 0.01 and 0.9 mM formaldehyde concentration range, with a 27 µM detection limit (at S/N = 3). Graphical abstract Schematic presentation of formaldehyde detection by Pd2Pt1-PPy/nitrogen-doped reduced Graphene Oxide Nanocomposite (Pd2Pt1-PPy /N-Gr NC). The decrease of charge transfer resistance and the agglomeration of deposited metals in the presence of N-rGO enhance the current response of the electrochemical sensor.
  12. Parmin NA, Hashim U, Gopinath SCB, Nadzirah S, Rejali Z, Afzan A, et al.
    Mikrochim Acta, 2019 05 08;186(6):336.
    PMID: 31069542 DOI: 10.1007/s00604-019-3445-2
    A gene sensor for rapid detection of the Human Papillomavirus 16 (HPV 16) which is associated with the appearance of cervical cancer was developed. The assay is based on voltammetric determination of HPV 16 DNA by using interdigitated electrodes modified with titanium dioxide nanoparticles. Titanium dioxide nanoparticles (NPs) were used to modify a semiconductor-based interdigitated electrode (IDE). The surface of the NPs was then functionalized with a commercial 24-mer oligomer DNA probe for HPV 16 that was modified at the 5' end with a carboxyl group. If the probe interacts with the HPV 16 ssDNA, the current, best measured at a working voltage of 1.0 V, increases. The gene sensor has has a ∼ 0.1 fM limit of detection which is comparable to other sensors. The dielectric voltammetry analysis was carried out from 0 V to 1 V. The electrochemical sensitivity of the IDE is 2.5 × 10-5 μA·μM-1·cm-2. Graphical abstract Schematic of an interdigitated electrode (IDE) modified with titanium dioxide nanoparticles for voltammetric determination of HPV 16 DNA by using an appropriate DNA probe.
  13. Che Sulaiman IS, Chieng BW, Osman MJ, Ong KK, Rashid JIA, Wan Yunus WMZ, et al.
    Mikrochim Acta, 2020 01 15;187(2):131.
    PMID: 31940088 DOI: 10.1007/s00604-019-3893-8
    This review (with 99 refs.) summarizes the progress that has been made in colorimetric (i.e. spectrophotometric) determination of organophosphate pesticides (OPPs) using gold and silver nanoparticles (NPs). Following an introduction into the field, a first large section covers the types and functions of organophosphate pesticides. Methods for colorimetric (spectrophotometric) measurements including RGB techniques are discussed next. A further section covers the characteristic features of gold and silver-based NPs. Syntheses and modifications of metal NPs are covered in section 5. This is followed by overviews on enzyme inhibition-based assays, aptamer-based assays and chemical (non-enzymatic) assays, and a discussion of specific features of colorimetric assays. Several Tables are presented that give an overview on the wealth of methods and materials. A concluding section addresses current challenges and discusses potential future trends and opportunities. Graphical abstractSchematic representation of organophosphate pesticide determinations based on aggregation of nanoparticles (particular silver or gold nanoparticles). This leads to a color change which can be determined visually and monitored by a red shift in the absorption spectrum.
  14. Letchumanan I, Gopinath SCB, Arshad MKM
    Mikrochim Acta, 2020 01 14;187(2):128.
    PMID: 31938893 DOI: 10.1007/s00604-020-4115-0
    A method is described for the electrochemical determination of squamous cell carcinoma (SCC) antigen, and by testing the effect of 30 nm gold nanoparticles (GNPs). Three comparative studies were performed in the presence and absence of GNPs, and with agglomerated GNPs. The divalent ion Ca(II) was used to induce a strong agglomeration of GNPs, as confirmed by colorimetry and voltammetry. Herein, colorimetry was used to test the best amount of salt needed to aggregate the GNPs. Despite, voltammetry was used to determine the status of biomolecules on the sensor. The topography of the surface of ZnO-coated interdigitated electrodes was analyzed by using 3D-nano profilometry, scanning electron microscopy, atomic force microscopy and high-power microscopy. The interaction between SCC antigen and antibody trigger vibrations on the sensor and cause dipole moment, which was measured using a picoammeter with a linear sweep from 0 to 2 V at 0.01 V step voltage. The sensitivity level was 10 fM by 3σ calculation for the dispersed GNP-conjugated antigen. This indicates a 100-fold enhancement compared to the condition without GNP conjugation. However, the sensitivity level for agglomerated GNPs conjugated antibody was not significant with 100 fM sensitivity. Specificity was tested for other proteins in serum, namely blood clotting factor IX, C-reactive protein, and serum albumin. The SCC antigen was quantified in spiked serum and gave recoveries that ranged between 80 and 90%. Graphical abstractSchematic representation of SCC (squamous cell carcinoma) antigen determination using divalent ion induced agglomerated GNPs. Sensitivity increment depends on the occurrence of more SCC antigen and antibody binding event via GNPs integration. Notably, lower detection limit was achieved at femto molar with proper orientation of biological molecules.
  15. Mohammed Modawe Alshik Edris N, Abdullah J, Kamaruzaman S, Sulaiman Y
    Mikrochim Acta, 2019 03 29;186(4):261.
    PMID: 30927085 DOI: 10.1007/s00604-019-3376-y
    A nanocomposite consisting of electrochemically reduced graphene oxide, poly(Eriochrome black T) and gold nanoparticles (ERGO-pEBT/AuNPs) was prepared for the simultaneous detection of resorcinol (RC), catechol (CC), and hydroquinone (HQ). The electrochemical oxidation of HQ, CC, and RC was analysed by using cyclic voltammetry and differential pulse voltammetry. Three well-separated potentials were found at 166, 277, and 660 mV (vs. Ag/AgCl) for HQ, CC, and RC, respectively The linear ranges were 0.52-31.4, 1.44-31.2, and 3.8-72.2 μM for HQ, CC, and RC, respectively. The limits of detections (LODs) for both individual and simultaneous detections are negligibly different are (15, 8, and 39 nM, respectively). Graphical abstract Voltammetric determination of hydroquinone, catechol, and resorcinol at ERGO-pEBT/AuNPs resulted in high peak currents and outstanding oxidation potential separation of the analytes.
  16. Azri FA, Eissa S, Zourob M, Chinnappan R, Sukor R, Yusof NA, et al.
    Mikrochim Acta, 2020 04 12;187(5):266.
    PMID: 32279134 DOI: 10.1007/s00604-020-4218-7
    An electrochemical aptasensor is described for determination of the phytohormone of zearalenone (ZEA). The gold electrode was modified with ZEA via covalent attachment using cysteamine-hydrochloride and 1,4-phenylene diisocyanate linker. A truncated ZEA aptamer with a dissociation constant of 13.4 ± 2.1 nM was used in an aptasensor. The electrochemical property was investigated using square wave voltammetry for monitoring the change in the electron transfer using the ferro/ferricyanide system as redox probe. Under optimal experimental conditions, the response was best measured at a potential of 0.20 V (vs. Ag/AgCl). The signals depended on the competitive mechanism between the immobilised ZEA and free ZEA for the aptamer binding site. The aptasensor works in the range 0.01 to 1000 ng·mL-1 ZEA concentration, with a detection limit of 0.017 ng·mL-1. High degree of cross-reactivity with the other analogues of ZEA was observed, whereas none towards other mycotoxins. The aptasensor was further applied for the determination of ZEA in the extract of maize grain and showed good recovery percentages between 87 and 110%. Graphical abstract Schematic representation of the electrochemical determination of zearalenone based on indirect competitive assay. Step a Immobilisation of ZEA on the surface of gold electrode via covalent attachment, b competition for the ZEA aptamer binding site between immobilised and free ZEA, and c current signal of the binding event based on SWV technique.
  17. Amiri A, Baghayeri M, Karimabadi F, Ghaemi F, Maleki B
    Mikrochim Acta, 2020 03 10;187(4):213.
    PMID: 32157452 DOI: 10.1007/s00604-020-4193-z
    The stainless steel mesh, in the form of the disk, was coated with graphene oxide and poly(dimethylsiloxane) (GO-PDMS) by sol-gel technique. The coated stainless steel meshes are loaded in the mini-column as solid-phase extraction cartridge for the fast isolation and preconcentration of polycyclic aromatic hydrocarbons (PAHs) from real water samples. The extracted PAHs (naphthalene, acenaphthene, acenaphthylene, anthracene, benz[a]anthracene, fluorene, and pyrene) were quantified by gas chromatography-mass spectrometry. The operation parameters affecting the extraction efficiency including sample volume, desorption conditions, and ionic strength were investigated. At optimized conditions, the linearity of this method is obtained from 0.001 to 20 ng mL-1 with 0.2 to 1.0 pg mL-1 limit of detection. For 5 replicates at 3 spiking levels (0.1, 1, and 10 ng mL-1), the relative standard deviations between 4.0 and 6.3% were achieved. The absolute extraction recovery varied from 89.1 to 94.7%. The enrichment factors were in the range of 2227-2367. The method has been employed in the determination of PAHs in the real water samples including well water, tap water, river water, and wastewater. Relative recoveries are between 95.2 and 100.9%. Graphical abstractSchematic representation of the SPE procedure using the self-assembly SPE cartridge.
  18. Nadzirah S, Hashim U, Gopinath SCB, Parmin NA, Hamzah AA, Yu HW, et al.
    Mikrochim Acta, 2020 03 17;187(4):235.
    PMID: 32185529 DOI: 10.1007/s00604-020-4214-y
    A titanium dioxide nanoparticle (TiO2 NP)-mediated resistive biosensor is described for the determination of DNA fragments of Escherichia coli O157:H7 (E. coli O157:H7). The sol-gel method was used to synthesize the TiO2 NP, and microlithography was applied to fabricate the interdigitated sensor electrodes. Conventional E. coli DNA detections are facing difficulties in long-preparation-and-detection-time (more than 3 days). Hence, electronic biosensor was introduced by measuring the current-voltage (I-V) DNA probe without amplification of DNA fragments. The detection scheme is based on the interaction between the electron flow on the sensor and the introduction of negative charges from DNA probe and target DNA. The biosensor has a sensitivity of 1.67 × 1013 Ω/M and a wide analytical range. The limit detection is down to 1 × 10-11 M of DNA. The sensor possesses outstanding repeatability and reproducibility and is cabable to detect DNA within 15 min in a minute-volume sample (1 μL). Graphical abstract Fig. (a) Graphical illustration of electronic biosensor set up and (b) relationship between limit of detection (LOD) and the unaffected poultry samples on E. coli O157:H7.
  19. Ibrahim I, Lim HN, Huang NM
    Mikrochim Acta, 2019 06 14;186(7):452.
    PMID: 31201543 DOI: 10.1007/s00604-019-3547-x
    A multi-functional hybrid of cellulose acetate with cadmium sulfide and Methylene blue (CA/CdS/MB) in a bead composition was synthesized and investigated as a photosensor-adsorbent for the rapid, selective, and sensitive detection, and adsorption of Cu(II) ions. These hybrid CA-modified beads are composed of multiple adsorption active sites and possess a surface area of 58 cm2 g-1. They are an efficient adsorbent with a maximum adsorption capacity of 0.57 mg g-1. Photoelectrochemical (PEC) detection of Cu(II) was accomplished by modifying the beads on a glassy carbon electrode. The beads containing 20 mmol of sulfur displayed the widest linear analytical range (0.1-290 nM) and the lowest detection limit (16.9 nM) for Cu(II) with high selectivity and reliable reproducibility. The successful application of the beads has provided a new insight for the selection of a responsive photoactive material for a PEC assay, as well as an effective adsorbent material for Cu(II) ions. Graphical abstract A multi-functional hybrid of cellulose acetate with cadmium sulfide and Methylene blue (CA/CdS/MB) in a bead composition was synthesized and investigated as a photosensor-adsorbent for the rapid, selective and sensitive detection and adsorption of Cu(II) ions.
  20. Mohd Azmi UZ, Yusof NA, Abdullah J, Alang Ahmad SA, Mohd Faudzi FN, Ahmad Raston NH, et al.
    Mikrochim Acta, 2021 01 06;188(1):20.
    PMID: 33404779 DOI: 10.1007/s00604-020-04669-x
    An early detection of Mycobacterium tuberculosis is very important to reduce the number of fatal cases and allow for fast recovery. However, the interpretation of the result from smear microscopy requires skilled personnel due to the propensity of the method to produce false-negative results. In this work, a portable, rapid, and simple sandwich-type immunosensor reader has been developed that is able to detect the presence of M. tuberculosis in sputum samples. By using sandwich-type immunosensor, an anti-CFP10-ESAT6 antibody was immobilized onto the graphene/polyaniline (GP/PANI)-modified gold screen-printed electrode. After incubation with the target CFP10-ESAT6 antigen, the iron/gold magnetic nanoparticles (Fe3O4/Au MNPs) conjugated with anti-CFP10-ESAT6 antibody were used to complete the sandwich format. Differential pulse voltammetry (DPV) technique was used to detect the CFP10-ESAT6 antigen at the potential range of 0.0-1.0 V. The detection time is less than 2 h. Under optimal condition, CFP10-ESAT6 antigen was detected in a linear range from 10 to 500 ng mL-1 with a limit of detection at 1.5 ng mL-1. The method developed from this process was then integrated into a portable reader. The performance of the sensor was investigated and compared with the standard methods (culture and smear microscopy). It provides a good correlation (100% sensitivity and 91.7% specificity) with both methods of detection for M. tuberculosis in sputum samples henceforth, demonstrating the potential of the device as a more practical screening tool.Graphical abstract.
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