An optical DNA biosensor based on fluorescence resonance energy transfer
(FRET) utilizing synthes... more An optical DNA biosensor based on fluorescence resonance energy transfer (FRET) utilizing synthesized quantum dot (QD) has been developed for the detection of specific-sequence of DNA for Ganoderma boninense, an oil palm pathogen. Modified QD that contained carboxylic groups was conjugated with a single-stranded DNA probe (ssDNA) via amide-linkage. Hybridization of the target DNA with conjugated QD-ssDNA and reporter probe labeled with Cy5 allows for the detection of related synthetic DNA sequence of Ganoderma boninense gene based on FRET signals. Detection of FRET emission before and after hybridization was confirmed through the capability of the system to produce FRET at 680 nm for hybridized sandwich with complementary target DNA. No FRET emission was observed for non-complementary system. Hybridization time, temperature and effect of different concentration of target DNA were studied in order to optimize the developed system. The developed biosensor has shown high sensitivity with detection limit of 3.55 × 10−9 M. TEM results show that the particle size of QD varies in the range between 5 to 8 nm after ligand modification and conjugation with ssDNA. This approach is capable of providing a simple, rapid and sensitive method for detection of related synthetic DNA sequence of Ganoderma boninense.
Although nanoparticle-enhanced biosensors have been extensively researched,
few studies have syst... more Although nanoparticle-enhanced biosensors have been extensively researched, few studies have systematically characterized the roles of nanoparticles in enhancing biosensor functionality. This paper describes a successful new method in which DNA binds directly to iron oxide nanoparticles for use in an optical biosensor. A wide variety of nanoparticles with different properties have found broad application in biosensors because their small physical size presents unique chemical, physical, and electronic properties that are different from those of bulk materials. Of all nanoparticles, magnetic nanoparticles are proving to be a versatile tool, an excellent case in point being in DNA bioassays, where magnetic nanoparticles are often used for optimization of the hybridization and separation of target DNA. A critical step in the successful construction of a DNA biosensor is the efficient attachment of biomolecules to the surface of magnetic nanoparticles. To date, most methods of synthesizing these nanoparticles have led to the formation of hydrophobic particles that require additional surface modifications. As a result, the surface to volume ratio decreases and nonspecific bindings may occur so that the sensitivity and efficiency of the device deteriorates. A new method of large-scale synthesis of iron oxide (Fe3O4) OPEN ACCESS Molecules 2014, 19 4356 nanoparticles which results in the magnetite particles being in aqueous phase, was employed in this study. Small modifications were applied to design an optical DNA nanosensor based on sandwich hybridization. Characterization of the synthesized particles was carried out using a variety of techniques and CdSe/ZnS core-shell quantum dots were used as the reporter markers in a spectrofluorophotometer. We showed conclusively that DNA binds to the surface of ironoxide nanoparticles without further surface modifications and that these magnetic nanoparticles can be efficiently utilized as biomolecule carriers in biosensing devices.
The oil palm, an economically important tree, has been one of the world’s major sources of edible... more The oil palm, an economically important tree, has been one of the world’s major sources of edible oil and a significant precursor of biodiesel fuel. Unfortunately, it now faces the threat of a devastating disease. Many researchers have identified Ganoderma boninense as the major pathogen that affects the oil palm tree and eventually kills it. But identification of the pathogen is just the first step. No single method has yet been able to halt the continuing spread of the disease. This paper discusses the modes of infection and transmission of Ganoderma boninense and suggests techniques for its early detection. Additionally, the paper proposes some possible ways of controlling the disease. Such measures, if implemented, could contribute significantly to the sustainability of the palm oil industry in South East Asia
In this paper, the electrochemical behavior of myricetin on a gold nanoparticle/ethylenediamine/m... more In this paper, the electrochemical behavior of myricetin on a gold nanoparticle/ethylenediamine/multi-walled carbonnanotube modified glassy carbon electrode (AuNPs/en/MWCNTs/GCE) has been investigated. Myricetin effectively accumulated on the AuNPs/en/MWCNTs/GCE and caused a pair of irreversible redox peaks at around 0.408 V and 0.191 V (vs. Ag/AgCl) in 0.1 mol L21 phosphate buffer solution (pH 3.5) for oxidation and reduction reactions respectively. The heights of the redox peaks were significantly higher on AuNPs/en/MWNTs/GCE compare with MWCNTs/GC and there was no peak on bare GC. The electron-transfer reaction for myricetin on the surface of electrochemical sensor was controlled by adsorption. Some parameters including pH, accumulation potential, accumulation time and scan rate have been optimized. Under the optimum conditions, anodic peak current was proportional to myricetin concentration in the dynamic range of 5.061028 to 4.061025 mol L21 with the detection limit of 1.261028 mol L21 . The proposed method was successfully used for the determination of myricetin content in tea and fruit juices.
A label-free optical detection method based on PNA/DNA hybridization using unmodified gold nanopa... more A label-free optical detection method based on PNA/DNA hybridization using unmodified gold nanoparticles (AuNPs) for dengue virus detection has been successfully developed. In this study, no immobilization method is involved and the hybridization of PNA/DNA occurs directly in solution. Unmodified AuNPs undergo immediate aggregation in the presence of neutral charge peptide nucleic acid (PNA) due to the coating of PNA on AuNPs surface. However, in the presence of complementary targets DNA, the hybridization of PNA probe with target DNA forms negatively charged complexes due to the negatively charged phosphate backbone of the target DNA.The negatively charged complexes adsorbed onto the AuNPs surface ensure sufficient charge repulsion, need for AuNPs dispersion, and stability in solution. The detection procedure is a naked eye method based on immediate color changes and also through UV-vis adsorption spectra. The selectivity of the proposed method was studied successfully by single base mismatch and noncomplementary target DNA.
There have been a number of studies which
deal with either toxic or non-toxic nature of superpara... more There have been a number of studies which deal with either toxic or non-toxic nature of superparamagnetic iron oxide nanoparticles (SPIONs); however, there is no clear cut information about their exact behavior and the reasons for its dual action. The objective of the present study was to investigate the SPIONs having similar oxidation states, but varying surface ligands and their role in terms of protecting the iron-mediated toxic responses. The four different SPIONs includes: (i) SPIONs containing oleic acid (SPIONs-1), (ii) SPIONs without any surface ligand (SPIONs-2), (iii) SPIONs containing cysteamine ligand (SPIONs-3), and (iv) SPIONs having both of oleic acid and cysteamine ligand. The particle size, surface functionality, and electronic oxidation states were con- firmed by the HRTEM, FT-IR, and XPS analysis, respectively. On in vitro testing of all four SPIONs with H9c2 cardiomyocyte cell line, the SPIONs-2 without any surface ligand found to exhibit significant decrease in the viability of cells at a concentration of 200 lg mL-1 for 16-h exposure period. Further investigation of toxicity mechanism resulted in the fact that the SPIONs-2 involved in the formation of ROS due to the role played by the more electron deficient Fe3? form of iron, there by decreased the glutathione release, increased DNA cleavage, and disrupted the mitochondrial transmembrane potential. However, the presence of unsaturation and/or thiol group (–SH) containing ligands on other SPIONs protected the cardiac cells from undergoing ROS-induced oxidative stress. Further, the results of the study confirming the importance of having unsaturated double bonds and/or –SH group possessing ligands onto the surface of SPIONs by means of protecting the cells from the influence of electron deficient Fe3? state of iron.
In the present work, nanohybrid of an anticancer drug, doxorubicin (Dox) loaded gold-coated super... more In the present work, nanohybrid of an anticancer drug, doxorubicin (Dox) loaded gold-coated superparamagnetic iron oxide nanoparticles (SPIONs@Au) were prepared for a combination therapy of cancer by means of both hyperthermia and drug delivery. The Dox molecules were conjugated to SPIONs@Au nanoparticles with the help of cysteamine (Cyst) as a non-covalent space linker and the Dox loading efficiency was investigated to be as high as 0.32 mg/mg. Thus synthesized particles were characterized by HRTEM, UV–Vis, FT-IR, SQUID magnetic studies and further tested for heat and drug release at low frequency oscillatory magnetic fields. The hyperthermia studies investigated to be strongly influenced by the applied frequency and the solvents used. The Dox delivery studies indicated that the drug release efficacy is strongly improved by maintaining the acidic pH conditions and the oscillatory magnetic fields, i.e. an enhancement in the Dox release was observed from the oscillation of particles due to the applied frequency, and is not effected by heating of the solution. Finally, the in vitro cell viability and proliferation studies were conducted using two different immortalized cell lines containing a cancerous (MCF-7 breast cancer) and non-cancerous H9c2 cardiac cell type.
This work describes the incorporation of SiNWs/AuNPs composite as a sensing material for DNA dete... more This work describes the incorporation of SiNWs/AuNPs composite as a sensing material for DNA detection on indium tin-oxide (ITO) coated glass slide. The morphology of SiNWs/AuNPs composite as the modifier layer on ITO was studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The morphological studies clearly showed that SiNWs were successfully decorated with 20 nm-AuNPs using selfassembly monolayer (SAM) technique. The effective surface area for SiNWs/AuNPs-modified ITO enhanced about 10 times compared with bare ITO electrode. SiNWs/AuNPs nanocomposite was further explored as a matrix for DNA probe immobilization in detection of dengue virus as a bio-sensing model to evaluate its performance in electrochemical sensors. The hybridization of complementary DNA was monitored by differential pulse voltammetry (DPV) using methylene blue (MB) as the redox indicator. The fabricated biosensor was able to discriminate significantly complementary, non-complementary and single-base mismatch oligonucleotides. The electrochemical biosensor was sensitive to target DNA related to dengue virus in the range of 9.0–178.0 ng/ml with detection limit of 3.5 ng/ml. In addition, SiNWs/AuNPs-modified ITO, regenerated up to 8 times and its stability was up to 10 weeks at 4 °C in silica gel.
In this study, a disposable screen-printed gold electrode
(SPGE) utilized of silicon nanowires (S... more In this study, a disposable screen-printed gold electrode (SPGE) utilized of silicon nanowires (SiNWs) and gold nanoparticles as sensing material was fabricated for detection of DNA oligomers related to dengue virus. Firstly, SiNWs/AuNPs-SPGE was developed by the dispersion of SiNWs in 3-Aminopropyltriethoxysilane (APTES, 0.5 %) onto bare SPGE. Secondly, the AuNPs decoration on SiNWs-SPGE surface was functionalized using dithiopropionic acid (DTPA) through a self-assembly monolayer (SAM) technique. The electrochemical response of methylene blue (MB) as a redox indicator towards synthetic DNA oligomer after hybridization on SiNWs/AuNPs-SPGE was recorded by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The results demonstrated that the reduction peak current of MB was significantly decreased after DNA hybridization process. In addition, the developed biosensor showed a good storage stability and could achieve a linear range of 1.0 × 10-11-1.0 × 10-7 M (R= 0.98) with the detection limit of 1.63× 10-12 M.
tThis paper describes how the sensitivity of an optical DNA nanosensor based on MNPs and QDs wase... more tThis paper describes how the sensitivity of an optical DNA nanosensor based on MNPs and QDs wasenhanced by using computer simulations including an innovative software, Grasshopper. The data usedwas derived from a previously constructed mechanism which, although successful in detecting targetDNA qualitatively, raised some areas for further investigation.By adjusting the relative proportions of DNA probes, MNPs and QDs in the model, we were able tosimulate a range of different reactions in the sensor and to measure them quantitatively. We were ableto observe MNPs and QDs binding to more than one strand of DNA and to better understand how theynetwork in different concentrations of the solution. We found a direct correlation coefficient of 0.9666between the fluorescent intensity of the CdSe/ZnS QDs and the concentration of tDNA within the rangeof 1 × 10−6–3.9 × 10−9M.To optimize the sensor further, we also modified the hybridization procedure, breaking it into twosteps. This produced a very satisfactory LOD calculation of 1.75 × 10−9M.Finally, when we applied the 2 step hybridization procedure we were able to improve the sensitivityof the optical nanosensor up to 20% furthur.
A novelopticaldetectionsystemconsistingofcombinationofuricase/HRP–CdS quantumdots(QDs)for
the det... more A novelopticaldetectionsystemconsistingofcombinationofuricase/HRP–CdS quantumdots(QDs)for the determinationofuricacidinurinesampleisdescribed.TheQDswasusedasanindicatortoreveal fluorescence propertyofthesystemresultingfromenzymaticreactionofuricaseandHRP(horseradish peroxidase),whichisinvolvedinoxidizinguricacidtoallaintoinandhydrogenperoxide.Thehydrogen peroxideproducedwasabletoquenchtheQDs fluorescence, whichwasproportionaltouricacid concentration. Thesystemdemonstratedsufficient activityofuricaseandHRPataratioof5U:5UandpH 7.0.Thelinearityofthesystemtowarduricacidwasintheconcentrationrangeof125–1000 mM with detection limitof125 mM.
A new electrochemical sensor based on
screen-printed electrode (SPE) gold nanoparticles (AuNPs)
h... more A new electrochemical sensor based on screen-printed electrode (SPE) gold nanoparticles (AuNPs) has been fabricated for determination of Pb(II) ion by anodic stripping voltammetry in Tris-HCl (pH 5) solution. In this medium, Pb(II) ion was preconcentrated on SPE modified with AuNPs and stripped anodically in linear sweep voltammetry mode, with a peak potential at −0.5 V. The effect of various parameters (pH, supporting electrolyte composition, deposition potential, deposition time, and scan rate) on the sensitivity was studied. Under controlled deposition time for 240 s, the detection limit (3 s) was 1.3-ng ml−1 Pb(II) and the calibration curve was linear up to 30 μg ml−1. The procedure was applied to the determination of Pb(II) ion in tap water with satisfactory results. The prepared modified electrode shows several advantages such as high sensitivity, long-time stability, wide linear range, and ease of preparation.
An artificial neural network (ANN) has been applied for determination of V(V) by using a new reag... more An artificial neural network (ANN) has been applied for determination of V(V) by using a new reagent, fatty hydroxamic acid. Spectra obtained from the V(V)-FHA complex at several selected wavelengths are used as the input data for the ANN. The V(V)-FHA complex shows a limited linear dynamic range of V(V) concentration of 0.01 - 250 mg/L. After training with ANN,
Little work has been reported on the development of solid state metal ion sensor based on the use... more Little work has been reported on the development of solid state metal ion sensor based on the use of amino acids and peptides. This review covers literature on the use of amino acids and peptides (short peptide, oligopeptide and cyclic peptide) as a recognition molecule for metal detection system. Amino acids and peptides offer a high degree of selectivity, good limit of detection and high sensitivity towards detection of metal ion.
An optical DNA biosensor based on fluorescence resonance energy transfer
(FRET) utilizing synthes... more An optical DNA biosensor based on fluorescence resonance energy transfer (FRET) utilizing synthesized quantum dot (QD) has been developed for the detection of specific-sequence of DNA for Ganoderma boninense, an oil palm pathogen. Modified QD that contained carboxylic groups was conjugated with a single-stranded DNA probe (ssDNA) via amide-linkage. Hybridization of the target DNA with conjugated QD-ssDNA and reporter probe labeled with Cy5 allows for the detection of related synthetic DNA sequence of Ganoderma boninense gene based on FRET signals. Detection of FRET emission before and after hybridization was confirmed through the capability of the system to produce FRET at 680 nm for hybridized sandwich with complementary target DNA. No FRET emission was observed for non-complementary system. Hybridization time, temperature and effect of different concentration of target DNA were studied in order to optimize the developed system. The developed biosensor has shown high sensitivity with detection limit of 3.55 × 10−9 M. TEM results show that the particle size of QD varies in the range between 5 to 8 nm after ligand modification and conjugation with ssDNA. This approach is capable of providing a simple, rapid and sensitive method for detection of related synthetic DNA sequence of Ganoderma boninense.
Although nanoparticle-enhanced biosensors have been extensively researched,
few studies have syst... more Although nanoparticle-enhanced biosensors have been extensively researched, few studies have systematically characterized the roles of nanoparticles in enhancing biosensor functionality. This paper describes a successful new method in which DNA binds directly to iron oxide nanoparticles for use in an optical biosensor. A wide variety of nanoparticles with different properties have found broad application in biosensors because their small physical size presents unique chemical, physical, and electronic properties that are different from those of bulk materials. Of all nanoparticles, magnetic nanoparticles are proving to be a versatile tool, an excellent case in point being in DNA bioassays, where magnetic nanoparticles are often used for optimization of the hybridization and separation of target DNA. A critical step in the successful construction of a DNA biosensor is the efficient attachment of biomolecules to the surface of magnetic nanoparticles. To date, most methods of synthesizing these nanoparticles have led to the formation of hydrophobic particles that require additional surface modifications. As a result, the surface to volume ratio decreases and nonspecific bindings may occur so that the sensitivity and efficiency of the device deteriorates. A new method of large-scale synthesis of iron oxide (Fe3O4) OPEN ACCESS Molecules 2014, 19 4356 nanoparticles which results in the magnetite particles being in aqueous phase, was employed in this study. Small modifications were applied to design an optical DNA nanosensor based on sandwich hybridization. Characterization of the synthesized particles was carried out using a variety of techniques and CdSe/ZnS core-shell quantum dots were used as the reporter markers in a spectrofluorophotometer. We showed conclusively that DNA binds to the surface of ironoxide nanoparticles without further surface modifications and that these magnetic nanoparticles can be efficiently utilized as biomolecule carriers in biosensing devices.
The oil palm, an economically important tree, has been one of the world’s major sources of edible... more The oil palm, an economically important tree, has been one of the world’s major sources of edible oil and a significant precursor of biodiesel fuel. Unfortunately, it now faces the threat of a devastating disease. Many researchers have identified Ganoderma boninense as the major pathogen that affects the oil palm tree and eventually kills it. But identification of the pathogen is just the first step. No single method has yet been able to halt the continuing spread of the disease. This paper discusses the modes of infection and transmission of Ganoderma boninense and suggests techniques for its early detection. Additionally, the paper proposes some possible ways of controlling the disease. Such measures, if implemented, could contribute significantly to the sustainability of the palm oil industry in South East Asia
In this paper, the electrochemical behavior of myricetin on a gold nanoparticle/ethylenediamine/m... more In this paper, the electrochemical behavior of myricetin on a gold nanoparticle/ethylenediamine/multi-walled carbonnanotube modified glassy carbon electrode (AuNPs/en/MWCNTs/GCE) has been investigated. Myricetin effectively accumulated on the AuNPs/en/MWCNTs/GCE and caused a pair of irreversible redox peaks at around 0.408 V and 0.191 V (vs. Ag/AgCl) in 0.1 mol L21 phosphate buffer solution (pH 3.5) for oxidation and reduction reactions respectively. The heights of the redox peaks were significantly higher on AuNPs/en/MWNTs/GCE compare with MWCNTs/GC and there was no peak on bare GC. The electron-transfer reaction for myricetin on the surface of electrochemical sensor was controlled by adsorption. Some parameters including pH, accumulation potential, accumulation time and scan rate have been optimized. Under the optimum conditions, anodic peak current was proportional to myricetin concentration in the dynamic range of 5.061028 to 4.061025 mol L21 with the detection limit of 1.261028 mol L21 . The proposed method was successfully used for the determination of myricetin content in tea and fruit juices.
A label-free optical detection method based on PNA/DNA hybridization using unmodified gold nanopa... more A label-free optical detection method based on PNA/DNA hybridization using unmodified gold nanoparticles (AuNPs) for dengue virus detection has been successfully developed. In this study, no immobilization method is involved and the hybridization of PNA/DNA occurs directly in solution. Unmodified AuNPs undergo immediate aggregation in the presence of neutral charge peptide nucleic acid (PNA) due to the coating of PNA on AuNPs surface. However, in the presence of complementary targets DNA, the hybridization of PNA probe with target DNA forms negatively charged complexes due to the negatively charged phosphate backbone of the target DNA.The negatively charged complexes adsorbed onto the AuNPs surface ensure sufficient charge repulsion, need for AuNPs dispersion, and stability in solution. The detection procedure is a naked eye method based on immediate color changes and also through UV-vis adsorption spectra. The selectivity of the proposed method was studied successfully by single base mismatch and noncomplementary target DNA.
There have been a number of studies which
deal with either toxic or non-toxic nature of superpara... more There have been a number of studies which deal with either toxic or non-toxic nature of superparamagnetic iron oxide nanoparticles (SPIONs); however, there is no clear cut information about their exact behavior and the reasons for its dual action. The objective of the present study was to investigate the SPIONs having similar oxidation states, but varying surface ligands and their role in terms of protecting the iron-mediated toxic responses. The four different SPIONs includes: (i) SPIONs containing oleic acid (SPIONs-1), (ii) SPIONs without any surface ligand (SPIONs-2), (iii) SPIONs containing cysteamine ligand (SPIONs-3), and (iv) SPIONs having both of oleic acid and cysteamine ligand. The particle size, surface functionality, and electronic oxidation states were con- firmed by the HRTEM, FT-IR, and XPS analysis, respectively. On in vitro testing of all four SPIONs with H9c2 cardiomyocyte cell line, the SPIONs-2 without any surface ligand found to exhibit significant decrease in the viability of cells at a concentration of 200 lg mL-1 for 16-h exposure period. Further investigation of toxicity mechanism resulted in the fact that the SPIONs-2 involved in the formation of ROS due to the role played by the more electron deficient Fe3? form of iron, there by decreased the glutathione release, increased DNA cleavage, and disrupted the mitochondrial transmembrane potential. However, the presence of unsaturation and/or thiol group (–SH) containing ligands on other SPIONs protected the cardiac cells from undergoing ROS-induced oxidative stress. Further, the results of the study confirming the importance of having unsaturated double bonds and/or –SH group possessing ligands onto the surface of SPIONs by means of protecting the cells from the influence of electron deficient Fe3? state of iron.
In the present work, nanohybrid of an anticancer drug, doxorubicin (Dox) loaded gold-coated super... more In the present work, nanohybrid of an anticancer drug, doxorubicin (Dox) loaded gold-coated superparamagnetic iron oxide nanoparticles (SPIONs@Au) were prepared for a combination therapy of cancer by means of both hyperthermia and drug delivery. The Dox molecules were conjugated to SPIONs@Au nanoparticles with the help of cysteamine (Cyst) as a non-covalent space linker and the Dox loading efficiency was investigated to be as high as 0.32 mg/mg. Thus synthesized particles were characterized by HRTEM, UV–Vis, FT-IR, SQUID magnetic studies and further tested for heat and drug release at low frequency oscillatory magnetic fields. The hyperthermia studies investigated to be strongly influenced by the applied frequency and the solvents used. The Dox delivery studies indicated that the drug release efficacy is strongly improved by maintaining the acidic pH conditions and the oscillatory magnetic fields, i.e. an enhancement in the Dox release was observed from the oscillation of particles due to the applied frequency, and is not effected by heating of the solution. Finally, the in vitro cell viability and proliferation studies were conducted using two different immortalized cell lines containing a cancerous (MCF-7 breast cancer) and non-cancerous H9c2 cardiac cell type.
This work describes the incorporation of SiNWs/AuNPs composite as a sensing material for DNA dete... more This work describes the incorporation of SiNWs/AuNPs composite as a sensing material for DNA detection on indium tin-oxide (ITO) coated glass slide. The morphology of SiNWs/AuNPs composite as the modifier layer on ITO was studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The morphological studies clearly showed that SiNWs were successfully decorated with 20 nm-AuNPs using selfassembly monolayer (SAM) technique. The effective surface area for SiNWs/AuNPs-modified ITO enhanced about 10 times compared with bare ITO electrode. SiNWs/AuNPs nanocomposite was further explored as a matrix for DNA probe immobilization in detection of dengue virus as a bio-sensing model to evaluate its performance in electrochemical sensors. The hybridization of complementary DNA was monitored by differential pulse voltammetry (DPV) using methylene blue (MB) as the redox indicator. The fabricated biosensor was able to discriminate significantly complementary, non-complementary and single-base mismatch oligonucleotides. The electrochemical biosensor was sensitive to target DNA related to dengue virus in the range of 9.0–178.0 ng/ml with detection limit of 3.5 ng/ml. In addition, SiNWs/AuNPs-modified ITO, regenerated up to 8 times and its stability was up to 10 weeks at 4 °C in silica gel.
In this study, a disposable screen-printed gold electrode
(SPGE) utilized of silicon nanowires (S... more In this study, a disposable screen-printed gold electrode (SPGE) utilized of silicon nanowires (SiNWs) and gold nanoparticles as sensing material was fabricated for detection of DNA oligomers related to dengue virus. Firstly, SiNWs/AuNPs-SPGE was developed by the dispersion of SiNWs in 3-Aminopropyltriethoxysilane (APTES, 0.5 %) onto bare SPGE. Secondly, the AuNPs decoration on SiNWs-SPGE surface was functionalized using dithiopropionic acid (DTPA) through a self-assembly monolayer (SAM) technique. The electrochemical response of methylene blue (MB) as a redox indicator towards synthetic DNA oligomer after hybridization on SiNWs/AuNPs-SPGE was recorded by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The results demonstrated that the reduction peak current of MB was significantly decreased after DNA hybridization process. In addition, the developed biosensor showed a good storage stability and could achieve a linear range of 1.0 × 10-11-1.0 × 10-7 M (R= 0.98) with the detection limit of 1.63× 10-12 M.
tThis paper describes how the sensitivity of an optical DNA nanosensor based on MNPs and QDs wase... more tThis paper describes how the sensitivity of an optical DNA nanosensor based on MNPs and QDs wasenhanced by using computer simulations including an innovative software, Grasshopper. The data usedwas derived from a previously constructed mechanism which, although successful in detecting targetDNA qualitatively, raised some areas for further investigation.By adjusting the relative proportions of DNA probes, MNPs and QDs in the model, we were able tosimulate a range of different reactions in the sensor and to measure them quantitatively. We were ableto observe MNPs and QDs binding to more than one strand of DNA and to better understand how theynetwork in different concentrations of the solution. We found a direct correlation coefficient of 0.9666between the fluorescent intensity of the CdSe/ZnS QDs and the concentration of tDNA within the rangeof 1 × 10−6–3.9 × 10−9M.To optimize the sensor further, we also modified the hybridization procedure, breaking it into twosteps. This produced a very satisfactory LOD calculation of 1.75 × 10−9M.Finally, when we applied the 2 step hybridization procedure we were able to improve the sensitivityof the optical nanosensor up to 20% furthur.
A novelopticaldetectionsystemconsistingofcombinationofuricase/HRP–CdS quantumdots(QDs)for
the det... more A novelopticaldetectionsystemconsistingofcombinationofuricase/HRP–CdS quantumdots(QDs)for the determinationofuricacidinurinesampleisdescribed.TheQDswasusedasanindicatortoreveal fluorescence propertyofthesystemresultingfromenzymaticreactionofuricaseandHRP(horseradish peroxidase),whichisinvolvedinoxidizinguricacidtoallaintoinandhydrogenperoxide.Thehydrogen peroxideproducedwasabletoquenchtheQDs fluorescence, whichwasproportionaltouricacid concentration. Thesystemdemonstratedsufficient activityofuricaseandHRPataratioof5U:5UandpH 7.0.Thelinearityofthesystemtowarduricacidwasintheconcentrationrangeof125–1000 mM with detection limitof125 mM.
A new electrochemical sensor based on
screen-printed electrode (SPE) gold nanoparticles (AuNPs)
h... more A new electrochemical sensor based on screen-printed electrode (SPE) gold nanoparticles (AuNPs) has been fabricated for determination of Pb(II) ion by anodic stripping voltammetry in Tris-HCl (pH 5) solution. In this medium, Pb(II) ion was preconcentrated on SPE modified with AuNPs and stripped anodically in linear sweep voltammetry mode, with a peak potential at −0.5 V. The effect of various parameters (pH, supporting electrolyte composition, deposition potential, deposition time, and scan rate) on the sensitivity was studied. Under controlled deposition time for 240 s, the detection limit (3 s) was 1.3-ng ml−1 Pb(II) and the calibration curve was linear up to 30 μg ml−1. The procedure was applied to the determination of Pb(II) ion in tap water with satisfactory results. The prepared modified electrode shows several advantages such as high sensitivity, long-time stability, wide linear range, and ease of preparation.
An artificial neural network (ANN) has been applied for determination of V(V) by using a new reag... more An artificial neural network (ANN) has been applied for determination of V(V) by using a new reagent, fatty hydroxamic acid. Spectra obtained from the V(V)-FHA complex at several selected wavelengths are used as the input data for the ANN. The V(V)-FHA complex shows a limited linear dynamic range of V(V) concentration of 0.01 - 250 mg/L. After training with ANN,
Little work has been reported on the development of solid state metal ion sensor based on the use... more Little work has been reported on the development of solid state metal ion sensor based on the use of amino acids and peptides. This review covers literature on the use of amino acids and peptides (short peptide, oligopeptide and cyclic peptide) as a recognition molecule for metal detection system. Amino acids and peptides offer a high degree of selectivity, good limit of detection and high sensitivity towards detection of metal ion.
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(FRET) utilizing synthesized quantum dot (QD) has been developed for the detection of
specific-sequence of DNA for Ganoderma boninense, an oil palm pathogen. Modified QD
that contained carboxylic groups was conjugated with a single-stranded DNA probe
(ssDNA) via amide-linkage. Hybridization of the target DNA with conjugated QD-ssDNA
and reporter probe labeled with Cy5 allows for the detection of related synthetic DNA
sequence of Ganoderma boninense gene based on FRET signals. Detection of FRET
emission before and after hybridization was confirmed through the capability of the system
to produce FRET at 680 nm for hybridized sandwich with complementary target DNA.
No FRET emission was observed for non-complementary system. Hybridization time,
temperature and effect of different concentration of target DNA were studied in order to
optimize the developed system. The developed biosensor has shown high sensitivity with
detection limit of 3.55 × 10−9 M. TEM results show that the particle size of QD varies in the
range between 5 to 8 nm after ligand modification and conjugation with ssDNA. This
approach is capable of providing a simple, rapid and sensitive method for detection of
related synthetic DNA sequence of Ganoderma boninense.
few studies have systematically characterized the roles of nanoparticles in enhancing biosensor
functionality. This paper describes a successful new method in which DNA binds directly
to iron oxide nanoparticles for use in an optical biosensor. A wide variety of nanoparticles
with different properties have found broad application in biosensors because their small
physical size presents unique chemical, physical, and electronic properties that are different
from those of bulk materials. Of all nanoparticles, magnetic nanoparticles are proving to be
a versatile tool, an excellent case in point being in DNA bioassays, where magnetic
nanoparticles are often used for optimization of the hybridization and separation of target
DNA. A critical step in the successful construction of a DNA biosensor is the efficient
attachment of biomolecules to the surface of magnetic nanoparticles. To date, most
methods of synthesizing these nanoparticles have led to the formation of hydrophobic
particles that require additional surface modifications. As a result, the surface to volume
ratio decreases and nonspecific bindings may occur so that the sensitivity and efficiency of
the device deteriorates. A new method of large-scale synthesis of iron oxide (Fe3O4)
OPEN ACCESS
Molecules 2014, 19 4356
nanoparticles which results in the magnetite particles being in aqueous phase, was employed
in this study. Small modifications were applied to design an optical DNA nanosensor based
on sandwich hybridization. Characterization of the synthesized particles was carried out using
a variety of techniques and CdSe/ZnS core-shell quantum dots were used as the reporter
markers in a spectrofluorophotometer. We showed conclusively that DNA binds to the surface
of ironoxide nanoparticles without further surface modifications and that these magnetic
nanoparticles can be efficiently utilized as biomolecule carriers in biosensing devices.
significant precursor of biodiesel fuel. Unfortunately, it now faces the threat of a devastating disease. Many
researchers have identified Ganoderma boninense as the major pathogen that affects the oil palm tree and
eventually kills it. But identification of the pathogen is just the first step. No single method has yet been able to halt
the continuing spread of the disease. This paper discusses the modes of infection and transmission of Ganoderma
boninense and suggests techniques for its early detection. Additionally, the paper proposes some possible ways of
controlling the disease. Such measures, if implemented, could contribute significantly to the sustainability of the
palm oil industry in South East Asia
modified glassy carbon electrode (AuNPs/en/MWCNTs/GCE) has been investigated. Myricetin effectively
accumulated on the AuNPs/en/MWCNTs/GCE and caused a pair of irreversible redox peaks at around 0.408 V and 0.191 V
(vs. Ag/AgCl) in 0.1 mol L21 phosphate buffer solution (pH 3.5) for oxidation and reduction reactions respectively. The
heights of the redox peaks were significantly higher on AuNPs/en/MWNTs/GCE compare with MWCNTs/GC and there was
no peak on bare GC. The electron-transfer reaction for myricetin on the surface of electrochemical sensor was controlled by
adsorption. Some parameters including pH, accumulation potential, accumulation time and scan rate have been optimized.
Under the optimum conditions, anodic peak current was proportional to myricetin concentration in the dynamic range of
5.061028 to 4.061025 mol L21 with the detection limit of 1.261028 mol L21
. The proposed method was successfully used
for the determination of myricetin content in tea and fruit juices.
virus detection has been successfully developed. In this study, no immobilization method is involved and the hybridization of
PNA/DNA occurs directly in solution. Unmodified AuNPs undergo immediate aggregation in the presence of neutral charge
peptide nucleic acid (PNA) due to the coating of PNA on AuNPs surface. However, in the presence of complementary targets DNA,
the hybridization of PNA probe with target DNA forms negatively charged complexes due to the negatively charged phosphate
backbone of the target DNA.The negatively charged complexes adsorbed onto the AuNPs surface ensure sufficient charge repulsion,
need for AuNPs dispersion, and stability in solution. The detection procedure is a naked eye method based on immediate color
changes and also through UV-vis adsorption spectra. The selectivity of the proposed method was studied successfully by single
base mismatch and noncomplementary target DNA.
deal with either toxic or non-toxic nature of superparamagnetic
iron oxide nanoparticles (SPIONs); however,
there is no clear cut information about their exact behavior
and the reasons for its dual action. The objective of the
present study was to investigate the SPIONs having similar
oxidation states, but varying surface ligands and their role
in terms of protecting the iron-mediated toxic responses.
The four different SPIONs includes: (i) SPIONs containing
oleic acid (SPIONs-1), (ii) SPIONs without any surface
ligand (SPIONs-2), (iii) SPIONs containing cysteamine
ligand (SPIONs-3), and (iv) SPIONs having both of oleic
acid and cysteamine ligand. The particle size, surface
functionality, and electronic oxidation states were con-
firmed by the HRTEM, FT-IR, and XPS analysis, respectively.
On in vitro testing of all four SPIONs with H9c2
cardiomyocyte cell line, the SPIONs-2 without any surface
ligand found to exhibit significant decrease in the viability
of cells at a concentration of 200 lg mL-1 for 16-h
exposure period. Further investigation of toxicity mechanism
resulted in the fact that the SPIONs-2 involved in the
formation of ROS due to the role played by the more
electron deficient Fe3? form of iron, there by decreased the
glutathione release, increased DNA cleavage, and disrupted
the mitochondrial transmembrane potential. However,
the presence of unsaturation and/or thiol group (–SH)
containing ligands on other SPIONs protected the cardiac
cells from undergoing ROS-induced oxidative stress. Further,
the results of the study confirming the importance of
having unsaturated double bonds and/or –SH group possessing
ligands onto the surface of SPIONs by means of
protecting the cells from the influence of electron deficient
Fe3? state of iron.
iron oxide nanoparticles (SPIONs@Au) were prepared for a combination therapy of cancer by
means of both hyperthermia and drug delivery. The Dox molecules were conjugated to SPIONs@Au nanoparticles
with the help of cysteamine (Cyst) as a non-covalent space linker and the Dox loading efficiency
was investigated to be as high as 0.32 mg/mg. Thus synthesized particles were characterized by HRTEM,
UV–Vis, FT-IR, SQUID magnetic studies and further tested for heat and drug release at low frequency
oscillatory magnetic fields. The hyperthermia studies investigated to be strongly influenced by the
applied frequency and the solvents used. The Dox delivery studies indicated that the drug release efficacy
is strongly improved by maintaining the acidic pH conditions and the oscillatory magnetic fields, i.e. an
enhancement in the Dox release was observed from the oscillation of particles due to the applied frequency,
and is not effected by heating of the solution. Finally, the in vitro cell viability and proliferation
studies were conducted using two different immortalized cell lines containing a cancerous (MCF-7 breast
cancer) and non-cancerous H9c2 cardiac cell type.
tin-oxide (ITO) coated glass slide. The morphology of SiNWs/AuNPs composite as the modifier layer on ITO
was studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The morphological
studies clearly showed that SiNWs were successfully decorated with 20 nm-AuNPs using selfassembly
monolayer (SAM) technique. The effective surface area for SiNWs/AuNPs-modified ITO enhanced
about 10 times compared with bare ITO electrode. SiNWs/AuNPs nanocomposite was further explored as a matrix
for DNA probe immobilization in detection of dengue virus as a bio-sensing model to evaluate its performance
in electrochemical sensors. The hybridization of complementary DNA was monitored by differential
pulse voltammetry (DPV) using methylene blue (MB) as the redox indicator. The fabricated biosensor
was able to discriminate significantly complementary, non-complementary and single-base mismatch oligonucleotides.
The electrochemical biosensor was sensitive to target DNA related to dengue virus in the range of
9.0–178.0 ng/ml with detection limit of 3.5 ng/ml. In addition, SiNWs/AuNPs-modified ITO, regenerated up to
8 times and its stability was up to 10 weeks at 4 °C in silica gel.
(SPGE) utilized of silicon nanowires (SiNWs) and gold nanoparticles as
sensing material was fabricated for detection of DNA oligomers related
to dengue virus. Firstly, SiNWs/AuNPs-SPGE was developed by the
dispersion of SiNWs in 3-Aminopropyltriethoxysilane (APTES, 0.5 %)
onto bare SPGE. Secondly, the AuNPs decoration on SiNWs-SPGE
surface was functionalized using dithiopropionic acid (DTPA) through a
self-assembly monolayer (SAM) technique. The electrochemical response
of methylene blue (MB) as a redox indicator towards synthetic DNA
oligomer after hybridization on SiNWs/AuNPs-SPGE was recorded by
cyclic voltammetry (CV) and differential pulse voltammetry (DPV)
techniques. The results demonstrated that the reduction peak current of
MB was significantly decreased after DNA hybridization process. In
addition, the developed biosensor showed a good storage stability and
could achieve a linear range of 1.0 × 10-11-1.0 × 10-7 M (R= 0.98) with the
detection limit of 1.63× 10-12 M.
the determinationofuricacidinurinesampleisdescribed.TheQDswasusedasanindicatortoreveal
fluorescence propertyofthesystemresultingfromenzymaticreactionofuricaseandHRP(horseradish
peroxidase),whichisinvolvedinoxidizinguricacidtoallaintoinandhydrogenperoxide.Thehydrogen
peroxideproducedwasabletoquenchtheQDs fluorescence, whichwasproportionaltouricacid
concentration. Thesystemdemonstratedsufficient activityofuricaseandHRPataratioof5U:5UandpH
7.0.Thelinearityofthesystemtowarduricacidwasintheconcentrationrangeof125–1000 mM with
detection limitof125 mM.
screen-printed electrode (SPE) gold nanoparticles (AuNPs)
has been fabricated for determination of Pb(II) ion by anodic
stripping voltammetry in Tris-HCl (pH 5) solution. In this
medium, Pb(II) ion was preconcentrated on SPE modified with
AuNPs and stripped anodically in linear sweep voltammetry
mode, with a peak potential at −0.5 V. The effect of various
parameters (pH, supporting electrolyte composition, deposition
potential, deposition time, and scan rate) on the sensitivity was
studied. Under controlled deposition time for 240 s, the detection
limit (3 s) was 1.3-ng ml−1 Pb(II) and the calibration curve
was linear up to 30 μg ml−1. The procedure was applied to the
determination of Pb(II) ion in tap water with satisfactory results.
The prepared modified electrode shows several advantages such
as high sensitivity, long-time stability, wide linear range, and
ease of preparation.
(FRET) utilizing synthesized quantum dot (QD) has been developed for the detection of
specific-sequence of DNA for Ganoderma boninense, an oil palm pathogen. Modified QD
that contained carboxylic groups was conjugated with a single-stranded DNA probe
(ssDNA) via amide-linkage. Hybridization of the target DNA with conjugated QD-ssDNA
and reporter probe labeled with Cy5 allows for the detection of related synthetic DNA
sequence of Ganoderma boninense gene based on FRET signals. Detection of FRET
emission before and after hybridization was confirmed through the capability of the system
to produce FRET at 680 nm for hybridized sandwich with complementary target DNA.
No FRET emission was observed for non-complementary system. Hybridization time,
temperature and effect of different concentration of target DNA were studied in order to
optimize the developed system. The developed biosensor has shown high sensitivity with
detection limit of 3.55 × 10−9 M. TEM results show that the particle size of QD varies in the
range between 5 to 8 nm after ligand modification and conjugation with ssDNA. This
approach is capable of providing a simple, rapid and sensitive method for detection of
related synthetic DNA sequence of Ganoderma boninense.
few studies have systematically characterized the roles of nanoparticles in enhancing biosensor
functionality. This paper describes a successful new method in which DNA binds directly
to iron oxide nanoparticles for use in an optical biosensor. A wide variety of nanoparticles
with different properties have found broad application in biosensors because their small
physical size presents unique chemical, physical, and electronic properties that are different
from those of bulk materials. Of all nanoparticles, magnetic nanoparticles are proving to be
a versatile tool, an excellent case in point being in DNA bioassays, where magnetic
nanoparticles are often used for optimization of the hybridization and separation of target
DNA. A critical step in the successful construction of a DNA biosensor is the efficient
attachment of biomolecules to the surface of magnetic nanoparticles. To date, most
methods of synthesizing these nanoparticles have led to the formation of hydrophobic
particles that require additional surface modifications. As a result, the surface to volume
ratio decreases and nonspecific bindings may occur so that the sensitivity and efficiency of
the device deteriorates. A new method of large-scale synthesis of iron oxide (Fe3O4)
OPEN ACCESS
Molecules 2014, 19 4356
nanoparticles which results in the magnetite particles being in aqueous phase, was employed
in this study. Small modifications were applied to design an optical DNA nanosensor based
on sandwich hybridization. Characterization of the synthesized particles was carried out using
a variety of techniques and CdSe/ZnS core-shell quantum dots were used as the reporter
markers in a spectrofluorophotometer. We showed conclusively that DNA binds to the surface
of ironoxide nanoparticles without further surface modifications and that these magnetic
nanoparticles can be efficiently utilized as biomolecule carriers in biosensing devices.
significant precursor of biodiesel fuel. Unfortunately, it now faces the threat of a devastating disease. Many
researchers have identified Ganoderma boninense as the major pathogen that affects the oil palm tree and
eventually kills it. But identification of the pathogen is just the first step. No single method has yet been able to halt
the continuing spread of the disease. This paper discusses the modes of infection and transmission of Ganoderma
boninense and suggests techniques for its early detection. Additionally, the paper proposes some possible ways of
controlling the disease. Such measures, if implemented, could contribute significantly to the sustainability of the
palm oil industry in South East Asia
modified glassy carbon electrode (AuNPs/en/MWCNTs/GCE) has been investigated. Myricetin effectively
accumulated on the AuNPs/en/MWCNTs/GCE and caused a pair of irreversible redox peaks at around 0.408 V and 0.191 V
(vs. Ag/AgCl) in 0.1 mol L21 phosphate buffer solution (pH 3.5) for oxidation and reduction reactions respectively. The
heights of the redox peaks were significantly higher on AuNPs/en/MWNTs/GCE compare with MWCNTs/GC and there was
no peak on bare GC. The electron-transfer reaction for myricetin on the surface of electrochemical sensor was controlled by
adsorption. Some parameters including pH, accumulation potential, accumulation time and scan rate have been optimized.
Under the optimum conditions, anodic peak current was proportional to myricetin concentration in the dynamic range of
5.061028 to 4.061025 mol L21 with the detection limit of 1.261028 mol L21
. The proposed method was successfully used
for the determination of myricetin content in tea and fruit juices.
virus detection has been successfully developed. In this study, no immobilization method is involved and the hybridization of
PNA/DNA occurs directly in solution. Unmodified AuNPs undergo immediate aggregation in the presence of neutral charge
peptide nucleic acid (PNA) due to the coating of PNA on AuNPs surface. However, in the presence of complementary targets DNA,
the hybridization of PNA probe with target DNA forms negatively charged complexes due to the negatively charged phosphate
backbone of the target DNA.The negatively charged complexes adsorbed onto the AuNPs surface ensure sufficient charge repulsion,
need for AuNPs dispersion, and stability in solution. The detection procedure is a naked eye method based on immediate color
changes and also through UV-vis adsorption spectra. The selectivity of the proposed method was studied successfully by single
base mismatch and noncomplementary target DNA.
deal with either toxic or non-toxic nature of superparamagnetic
iron oxide nanoparticles (SPIONs); however,
there is no clear cut information about their exact behavior
and the reasons for its dual action. The objective of the
present study was to investigate the SPIONs having similar
oxidation states, but varying surface ligands and their role
in terms of protecting the iron-mediated toxic responses.
The four different SPIONs includes: (i) SPIONs containing
oleic acid (SPIONs-1), (ii) SPIONs without any surface
ligand (SPIONs-2), (iii) SPIONs containing cysteamine
ligand (SPIONs-3), and (iv) SPIONs having both of oleic
acid and cysteamine ligand. The particle size, surface
functionality, and electronic oxidation states were con-
firmed by the HRTEM, FT-IR, and XPS analysis, respectively.
On in vitro testing of all four SPIONs with H9c2
cardiomyocyte cell line, the SPIONs-2 without any surface
ligand found to exhibit significant decrease in the viability
of cells at a concentration of 200 lg mL-1 for 16-h
exposure period. Further investigation of toxicity mechanism
resulted in the fact that the SPIONs-2 involved in the
formation of ROS due to the role played by the more
electron deficient Fe3? form of iron, there by decreased the
glutathione release, increased DNA cleavage, and disrupted
the mitochondrial transmembrane potential. However,
the presence of unsaturation and/or thiol group (–SH)
containing ligands on other SPIONs protected the cardiac
cells from undergoing ROS-induced oxidative stress. Further,
the results of the study confirming the importance of
having unsaturated double bonds and/or –SH group possessing
ligands onto the surface of SPIONs by means of
protecting the cells from the influence of electron deficient
Fe3? state of iron.
iron oxide nanoparticles (SPIONs@Au) were prepared for a combination therapy of cancer by
means of both hyperthermia and drug delivery. The Dox molecules were conjugated to SPIONs@Au nanoparticles
with the help of cysteamine (Cyst) as a non-covalent space linker and the Dox loading efficiency
was investigated to be as high as 0.32 mg/mg. Thus synthesized particles were characterized by HRTEM,
UV–Vis, FT-IR, SQUID magnetic studies and further tested for heat and drug release at low frequency
oscillatory magnetic fields. The hyperthermia studies investigated to be strongly influenced by the
applied frequency and the solvents used. The Dox delivery studies indicated that the drug release efficacy
is strongly improved by maintaining the acidic pH conditions and the oscillatory magnetic fields, i.e. an
enhancement in the Dox release was observed from the oscillation of particles due to the applied frequency,
and is not effected by heating of the solution. Finally, the in vitro cell viability and proliferation
studies were conducted using two different immortalized cell lines containing a cancerous (MCF-7 breast
cancer) and non-cancerous H9c2 cardiac cell type.
tin-oxide (ITO) coated glass slide. The morphology of SiNWs/AuNPs composite as the modifier layer on ITO
was studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The morphological
studies clearly showed that SiNWs were successfully decorated with 20 nm-AuNPs using selfassembly
monolayer (SAM) technique. The effective surface area for SiNWs/AuNPs-modified ITO enhanced
about 10 times compared with bare ITO electrode. SiNWs/AuNPs nanocomposite was further explored as a matrix
for DNA probe immobilization in detection of dengue virus as a bio-sensing model to evaluate its performance
in electrochemical sensors. The hybridization of complementary DNA was monitored by differential
pulse voltammetry (DPV) using methylene blue (MB) as the redox indicator. The fabricated biosensor
was able to discriminate significantly complementary, non-complementary and single-base mismatch oligonucleotides.
The electrochemical biosensor was sensitive to target DNA related to dengue virus in the range of
9.0–178.0 ng/ml with detection limit of 3.5 ng/ml. In addition, SiNWs/AuNPs-modified ITO, regenerated up to
8 times and its stability was up to 10 weeks at 4 °C in silica gel.
(SPGE) utilized of silicon nanowires (SiNWs) and gold nanoparticles as
sensing material was fabricated for detection of DNA oligomers related
to dengue virus. Firstly, SiNWs/AuNPs-SPGE was developed by the
dispersion of SiNWs in 3-Aminopropyltriethoxysilane (APTES, 0.5 %)
onto bare SPGE. Secondly, the AuNPs decoration on SiNWs-SPGE
surface was functionalized using dithiopropionic acid (DTPA) through a
self-assembly monolayer (SAM) technique. The electrochemical response
of methylene blue (MB) as a redox indicator towards synthetic DNA
oligomer after hybridization on SiNWs/AuNPs-SPGE was recorded by
cyclic voltammetry (CV) and differential pulse voltammetry (DPV)
techniques. The results demonstrated that the reduction peak current of
MB was significantly decreased after DNA hybridization process. In
addition, the developed biosensor showed a good storage stability and
could achieve a linear range of 1.0 × 10-11-1.0 × 10-7 M (R= 0.98) with the
detection limit of 1.63× 10-12 M.
the determinationofuricacidinurinesampleisdescribed.TheQDswasusedasanindicatortoreveal
fluorescence propertyofthesystemresultingfromenzymaticreactionofuricaseandHRP(horseradish
peroxidase),whichisinvolvedinoxidizinguricacidtoallaintoinandhydrogenperoxide.Thehydrogen
peroxideproducedwasabletoquenchtheQDs fluorescence, whichwasproportionaltouricacid
concentration. Thesystemdemonstratedsufficient activityofuricaseandHRPataratioof5U:5UandpH
7.0.Thelinearityofthesystemtowarduricacidwasintheconcentrationrangeof125–1000 mM with
detection limitof125 mM.
screen-printed electrode (SPE) gold nanoparticles (AuNPs)
has been fabricated for determination of Pb(II) ion by anodic
stripping voltammetry in Tris-HCl (pH 5) solution. In this
medium, Pb(II) ion was preconcentrated on SPE modified with
AuNPs and stripped anodically in linear sweep voltammetry
mode, with a peak potential at −0.5 V. The effect of various
parameters (pH, supporting electrolyte composition, deposition
potential, deposition time, and scan rate) on the sensitivity was
studied. Under controlled deposition time for 240 s, the detection
limit (3 s) was 1.3-ng ml−1 Pb(II) and the calibration curve
was linear up to 30 μg ml−1. The procedure was applied to the
determination of Pb(II) ion in tap water with satisfactory results.
The prepared modified electrode shows several advantages such
as high sensitivity, long-time stability, wide linear range, and
ease of preparation.