The development of folate-functionalised palladium nanoparticles for folate receptor targeting in breast cancer cells.

Folate receptor-targeted therapy has excellent prospects for the treatment of breast cancer. A non-toxic concentration of folate-conjugated palladium-based nanoparticles was used to target the overexpressed folate receptor on breast cancer cells. The folate-conjugated nanoparticles were tailored to accumulate selectively in cancer cells relative to normal cells via the folate receptor. The MDA-MB-231, MDA-MB-468, MCF-7 breast cancer cell lines, and MCF-10A normal cell lines were used in the study. Qualitative and quantitative analysis of nanoparticle cellular uptake and accumulation was conducted using transmission electron microscopy and inductively coupled plasma-optical emission spectroscopy. The findings proved that folate-conjugated palladium nanoparticles successfully and preferentially accumulated in breast cancer cells. We conclude that folate-conjugated palladium nanoparticles can be potentially used to target breast cancer cells for radiopharmaceutical applications.

Pd nanocatalysts adsorbed onto silica nanoparticle coated indium tin oxide: a reusable nanozyme for glucose detection.

Nanozymes are nanomaterials that exhibit enzyme-like activity upon exposure to a substrate solution. The use of noble and platinum group metals enhances enzyme-like catalytic activity. However, noble metals are obtained at a high cost; therefore, their recovery after use is of high importance. Herein, we report the fabrication of indium tin oxide-silica nanoparticles decorated with palladium nanoparticles (ITO-SiO2-prS-PdNPs). The ITO-SiO2-prS-PdNPs were evaluated for peroxidase-like activity toward the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2. A colour change from clear or colourless TMB to blue colour (oxidized TMB products) was observed confirming the peroxidase-like activity. A typical Michaelis-Menten enzyme-like behaviour is observed with Km values of 0.68 mM for H2O2 and 0.47 mM for TMB, which are better than the reported values for horse-radish peroxidase (HRP) for the same substrate. The peroxidase-like activity of ITO-SiO2-prS-PdNPs was found to proceed via the electron-transfer mechanism. The ITO-SiO2-prS-PdNPs were cleaned successfully after each use by rinsing with water and ethanol solution thus making the surface simple and easy to recover and reuse. A reusable and highly selective colorimetric assay for glucose detection based on the peroxidase-like activity of ITO-SiO2-prS-PdNPs gave excellent results. ITO-SiO2-prS-PdNPs exhibited a good linear range of 5.0-30 µM, a low limit of detection (LOD) of 1.84 µM and a limit of quantification (LOQ) of 6.14 µM. Finally, the nanozyme (ITO-SiO2-prS-PdNPs) was successfully used to detect glucose in a complex newborn calf serum (NCS), representing a real sample.

Online regeneration of a piezoelectric and impedimetric immunosensor for the detection of C-reactive protein on the oriented antibody gold surface.

Cardiovascular diseases (CVDs) refer to diseases that affect the heart and blood vessels. CVDs are considered silent killers, which are fatal (death occurs abruptly) particularly when their diagnosis is delayed. Among the biomarkers related to cardiovascular diseases, C-reactive protein (CRP) is expressed or found in high concentrations during a cardiac event. Therefore, CRP is an excellent biomarker to diagnose cardiac events, and therefore quantitative monitoring of CRP is necessary. Herein, we report the fabrication of an immunosensor for the detection and monitoring of CRP. The anti-CRP monoclonal antibody (anti-CRP-mAb), which is specific to the CRP antigen, was immobilized on the surface of gold pre-modified with 4-mercaptophenyl boronic acid (MPBA) to act as a capture antibody. The self-assembled monolayer (SAM) of 4-mercaptophenyl boronic acid (4-MPBA), Au-MPBA, was used for the oriented immobilization of anti-CRP-mAb for piezoelectric (mass-sensitive) and piezoelectric (impedance) measurements. Controlling the orientation of anti-CRP-mAb was crucial to eliminate false positive and negative results during sample analysis. The quartz-crystal microbalance with dissipation (QCM-D) measurements enabled us to follow the covalent immobilization of anti-CRP-mAb on AuCQC-MPBA in real-time. QCM-D was further used to follow the affinity reactions between anti-CRP-mAb and CRP and further with the anti-CRP polyclonal antibody (anti-CRP-pAb). The changes in frequency (Δf, Hz) were related to the changes in the mass (Δm, ng cm-2) of CRP up to a concentration of 0.10 µg mL-1, which is equivalent to 0.10 mg L-1. CRP was detected using the direct affinity immunoassay (anti-CRP-mAb < CRP) and also a sandwich immunoassay using anti-CRP-pAb for signal enhancement. The developed piezoelectric CRP detection protocol was translated to a gold disc electrode for electrochemical impedance spectroscopy (EIS) measurements. The limit of detection (LOD) using both methods was at the µg mL-1 or mg L-1 level. Furthermore, the developed electrode could be regenerated using acidic buffer (0.10 M HCl). The detected signal could be reproduced to within 5% relative standard deviation (% RSD) in buffer and serum samples, showing excellent selectivity and specificity toward CRP.

Reaction of Perrhenate with Phthalocyanine Derivatives in the Presence of Reducing Agents and Rhenium Oxide Nanoparticles in Biomedical Applications.

A novel alternative route to access rhenium(V)-phthalocyanine complexes through direct metalation of metal-free phthalocyanines (H2 Pcs) with a rhenium(VII) salt in the presence of various two-electron reducing agents is presented. Direct ion metalation of tetraamino- or tetranitrophthalocyanine with perrhenate (ReO4- ) in the presence of triphenylphosphine led to oxidative decomposition of the H2 Pcs, giving their respective phthalonitriles. Conversely, treatment of H2 Pcs with ReO4- employing sodium metabisulfite yielded the desired ReV O-Pc complex. Finally, reaction of H2 Pcs with ReO4- and NaBH4 as reducing agent led to the formation of rhenium oxide (Rex Oy ) nanoparticles (NPs). The NP synthesis was optimised, and the Rex Oy NPs were capped with folic acid (FA) conjugated with tetraaminophthalocyanine (TAPc) to enhance their cancer cell targeting ability. The cytotoxicity profile of the resultant Rex Oy -TAPc-FA NPs was assessed and found to be greater than 80 % viability in four cell lines, namely, MDA-MB-231, HCC7, HCC1806 and HEK293T. Non-cytotoxic concentrations were determined and employed in cancer cell localization studies. The particle size effect on localization of NPs was also investigated using confocal fluorescence and transmission electron microscopy. The smaller NPs (≈10 nm) were found to exhibit stronger fluorescence properties than the ≈50 nm NPs and exhibited better cell localization ability than the ≈50 nm NPs.

Ultrasensitive detection of prostate-specific antigen using glucose-encapsulated nanoliposomes anti-PSA polyclonal antibody as detection nanobioprobes.

In this work, the preparation of glucose encapsulating nanoliposomes was achieved using two different lipid formulations, labelled as F1 and F2. Both formulations contained phosphatidylcholine (PC), oleylamido-4-butanoic acid (OABA) and in addition, F1 had cholesterol (CHO) while F2 contained cholesteroyl hemisussinate (CHEMS). These formulations were studied for their pH sensitivity and controlled release of encapsulated glucose for indirect detection of prostate-specific antigen (PSA) using sandwich immunoassay. As a signal generator, encapsulated glucose in nanoliposomes was quantified directly using the personal glucose meter (PGM) and colorimetrically using peroxidase property of horseradish peroxidase (HRP) enzyme and Pd|PdO as nanozymes. Controlled release of the encapsulated glucose was achieved using the pH effect or Triton-X 100 as a surfactant to destabilize the liposomal structure. The F2 formulation showed maximum controlled release at acidic phosphate buffer saline (PBS, pH 5.0). The concentration of encapsulated glucose was found to be high in F2 formulation and these were applied for the indirect detection of PSA. The limit of detection (LOD) values for PSA were found to be 53 fg mL-1, 64 fg mL-1 and 10 fg mL-1 when HRP, Pd|PdO and PGM were respectively used. The detection signal was linear over a wide concentration range for PSA including the clinical range of 4-10 ng mL-1. The HRP system showed low LOD value when compared with Pd|PdO nanozymes. PGM system gave lowest LOD values owing to the sensitivity of the system towards glucose. Pd|PdO nanozyme system showed good stability over a wide temperature up to 80 °C. PGM system required less reaction time (2 min), low reagents and results were readily generated in digital format.

Oriented Antibody Covalent Immobilization for Label-Free Impedimetric Detection of C-Reactive Protein via Direct and Sandwich Immunoassays.

The detection and monitoring of biological markers as disease indicators in a simple manner is a subject of international interest. In this work, we report two simple and sensitive label-free impedimetric immunoassays for the detection of C-reactive protein (CRP). The gold electrode modified with boronic acid-terminated self-assembled monolayers afforded oriented immobilization of capture glycosylated antibody (antihuman CRP monoclonal antibody, mAb). This antibody-modified surface was able to capture human CRP protein, and the impedance signal showed linear dependence with CRP concentration. We confirmed the immobilization of anti-CRP mAb using surface sensitive X-ray photoelectron spectroscopy (XPS) and electrochemical impedance. The oriented covalent immobilization of mAb was achieved using glycosylated Fc (fragment, crystallizable) region specific to boronic acid. The direct immunoassay exhibited a linear curve for concentration range up to 100 ng ml-1. The limit of detection (LoD) of 2.9 ng ml-1, limit of quantification (LoQ) of 9.66 ng ml-1, and sensitivity of 0.585 kΩ ng-1 ml cm-2 were obtained. The sandwich immunoassay was carried out by capturing polyclonal anti-CRP antibody (pAb) onto the CRP antigen immunoreaction. The impedance signal after pAb capture also showed linear dependence with CRP antigen concentration and acted as a CRP antigen detection signal amplifier. The detection of the CRP antigen using sandwich pAb immunoassay improved LoD to 1.2 ng ml-1, LoQ to 3.97 ng ml-1, and enhanced the sensitivity to 0.885 kΩ ng-1 ml cm-2. The real sample analysis, using newborn calf serum, showed excellent selectivity and % recovery for the human CRP ranging from 91.2 to 96.5%. The method was reproducible to 4.5% for direct immunoassay and 2.3% for sandwich immunoassay.

Immunoassay detection of tumor-associated autoantibodies using protein G bioconjugated to nanomagnet-silica decorated with Au@Pd nanoparticles.

A colorimetric immunosensor was developed for the detection of tumor-associated anti-p53 autoantibodies (anti-p53aAbs). The immunosensor platform was prepared by immobilizing human-protein (p53Ag) onto a high binding 96-well plate. The immunoassay was based on the immunometric sandwich protocol, and protein G functionalized nanomagnet-silica nanoparticles decorated with Au@Pd (Fe3O4@SiO2-NH2-Au@Pd0.30NPs-protG) was used as the detection nanobioprobe. The Fe3O4@SiO2-NH2-Au@Pd0.30NPs-protG exhibited a high binding affinity for the captured anti-p53aAbs and high catalytic performance towards the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). The oxidation of TMB resulted in significant color change and a UV-vis absorption signal. The detection was achieved by measuring the changes in UV-Vis absorption as the concentrations of anti-p53aAbs changed. The apparent binding affinity (KD) between the p53aAbs and Fe3O4@SiO2-NH2-Au@Pd0.30NPs-protG was 35.2 ng mL-1. The plot of change in the absorption intensity against the logarithm of anti-p53aAbs was linear within 1.0-500.0 ng mL-1 with a correlation coefficient (R2) of 0.98. The detection limit (LoD) using 3σ was calculated to be 15 pg mL-1, which is lower than the conventional HRP-label based colorimetric immunoassay. The real sample detection was investigated using the serum recovery method. The recovery of the anti-p53aAbs ranges from 98.5% to 105.7%, demonstrating its potential for practical applications.

Solventless synthesis of nanospinel Ni1-x Co x Fe2O4 (0 ≤ x ≤ 1) solid solutions for efficient electrochemical water splitting and supercapacitance.

The formation of solid solutions represents a robust strategy for modulating the electronic properties and improving the electrochemical performance of spinel ferrites. However, solid solutions have been predominantly prepared via wet chemical routes, which involve the use of harmful and/or expensive chemicals. In the present study, a facile, inexpensive and environmentally benign solventless route is employed for the composition-controlled synthesis of nanoscopic Ni1-x Co x Fe2O4 (0 ≤ x ≤ 1) solid solutions. The physicochemical characterization of the samples was performed by p-XRD, SEM, EDX, XPS, TEM, HRTEM and UV-Vis techniques. A systematic investigation was also carried out to elucidate the electrochemical performance of the prepared nanospinels towards energy generation and storage. Based on the results of CV, GCD, and stability tests, the Ni0.4Co0.6Fe2O4 electrode showed the highest performance for the supercapacitor electrode exhibiting a specific capacitance of 237 F g-1, superior energy density of 10.3 W h kg-1 and a high power density with a peak value of 4208 W kg-1, and 100% of its charge storage capacity was retained after 4000 cycles with 97% coulombic efficiency. For HER, the Ni0.6Co0.4Fe2O4 and CoFe2O4 electrodes showed low overpotentials of 168 and 169 mV, respectively, indicating better catalytic activity. For OER, the Ni0.8Co0.2Fe2O4 electrode exhibited a lower overpotential of 320 mV at a current density of 10 mA cm-2, with a Tafel slope of 79 mV dec-1, demonstrating a fast and efficient process. These results indicated that nanospinel ferrite solid solutions could be employed as promising electrode materials for supercapacitor and water splitting applications.

Bimetallic gold and palladium nanoparticles supported on copper oxide nanorods for enhanced H2O2 catalytic reduction and sensing.

The emergence of nanoscience and nanotechnology has revitalised research interest in using copper and its derived nanostructures to find exciting and novel applications. In this work, mono- and bimetallic gold and palladium nanoparticles supported on copper oxide nanorods (CuONRs) were prepared and their catalytic performance towards the reduction of H2O2 to form reactive oxygen radical species (ROS) was evaluated. The characterisation using microscopy and spectroscopic techniques confirms the successful synthesis of CuONRs, CuONRs@Au6NPs, CuONRs@Pd6NPs and CuONRs@Au3Pd3NPs. The efficient generation of ROS was confirmed using UV-vis spectroscopy and 1,3-diphenylisobenzofuran (DPBF) as a radical scavenger. The CuONRs possess excellent catalytic reduction activity for H2O2 by generating ROS. However, CuONRs also have lattice oxygens which do not participate in the catalytic reduction step. The lattice oxygens however allowed for the adsorption of gold and palladium nanoparticles (Au6NPs, Pd6NPs and Au3Pd3NPs) and thus enhanced catalytic reduction of H2O2 to produce ROS. The produced ROS was subsequently involved in the catalytic oxidation of a chromogenic substrate (TMB), resulting in blue coloured diimine (TMBDI) complex which was monitored using UV-vis and could also be observed using the naked eye. The catalyst dependence on pH, temperature, and H2O2 concentration towards efficient ROS generation was investigated. The gold and palladium-supported CuONRs nanocatalysts were evaluated for their potential applications in the fabrication of colorimetric biosensors to detect glucose oxidation by glucose oxidase (GOx). Glucose was used as a model analyte. The enzymatic reaction between GOx and ß-d-glucose produces H2O2 as a by-product, which is then catalytically converted to ROS by the nanoparticles.

Low temperature scalable synthetic approach enabling high bifunctional electrocatalytic performance of NiCo2S4 and CuCo2S4 thiospinels.

Ternary metal sulfides are currently in the spotlight as promising electroactive materials for high-performance energy storage and/or conversion technologies. Extensive research on metal sulfides has indicated that, amongst other factors, the electrochemical properties of the materials are strongly influenced by the synthetic protocol employed. Herein, we report the electrochemical performance of uncapped NiCo2S4 and CuCo2S4 ternary systems prepared via solventless thermolysis of the respective metal ethyl xanthate precursors at 200 and 300 °C. The structural, morphological and compositional properties of the synthesized nanoparticles were examined by powder X-ray diffraction (p-XRD), transmission electron microscopy (TEM), high-resolution TEM, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX) techniques. Electrochemical studies indicate that NiCo2S4 nanoparticles synthesized at 300 °C exhibit superior energy storage characteristics with a high specific capacitance of ca. 2650 F g-1 at 1 mV s-1, as compared to CuCo2S4 nanoparticles, which showcased a specific capacitance of ca. 1700 F g-1 at the same scan rate. At a current density of 0.5 A g-1, NiCo2S4 and CuCo2S4 nanoparticles displayed specific capacitances of 1201 and 475 F g-1, respectively. In contrast, CuCo2S4 nanoparticles presented a higher electrocatalytic activity with low overpotentials of 269 mV for oxygen evolution reaction (OER), and 224 mV for the hydrogen evolution reaction (HER), at 10 mA cm-2. The stability of the catalysts was examined for 2000 cycles in which a negligible change in both OER and HER activities was observed.

Electrografting of 4-Carboxybenzenediazonium on Glassy Carbon Electrode: The Effect of Concentration on the Formation of Mono and Multilayers.

Grafting of electrodes with diazonium salts using cyclic voltammetry (CV) is a well-established procedure for surface modification. However, little is known about the effect of the concentration of the diazonium salt on the number of layers grafted on the electrode surface. In this work, the impact of concentration on the grafting of 4-carboxybenzenediazonium (4-CBD) onto a glassy carbon electrode (GCE) is elucidated. The number of layers grafted on the GCE was linearly dependent on the concentration of 4-CBD and varied between 0.9 and 4.3 when the concentration was varied between 0.050 and 0.30 mmol/L at 0.10 V.s-1. Characterization of modified glassy carbon surface with X-ray photoelectron spectroscopy (XPS) confirmed the grafting of carboxyphenyl layer on the surface. Grafting with 0.15 mmol/L 4-CBD (1 CV cycle) did not form a detectable amount of carboxyphenyl (CP) moieties at the surface, while a single scan with higher concentration (2.5 mmol/L) or multiple scans (22 cycles) gave detectable signals, indicating formation of multilayers. We also demonstrate the possibility of removing the thin layer grafted on a glassy carbon electrode by applying high oxidation potential +1.40 V.

Ultrasensitive detection of anti-p53 autoantibodies based on nanomagnetic capture and separation with fluorescent sensing nanobioprobe for signal amplification.

The detection of biomarkers expressed at early onset of carcinogenesis, hold promise for the identification of subjects with a preclinical malignant tumor. However, these biomarkers exist in bodily fluids at an ultra-low concentration. Therefore, ultrasensitive techniques are required for their detection. This work investigated the detection of anti-p53 autoantibodies (anti-p53aAbs) using nanomagnetic beads capture probe and anti-IgG functionalized-fluorescence nanoparticles as the detection probe. Specificity was achieved by the use of human p53 protein (p53Ag) immobilized onto nanomagnetic beads, blocked with BSA (MB-p53Ag/BSA) for capture and separation. Anti-IgG antibody conjugated FITC-doped silica nanoparticles (FITC@SiO2-NH2-anti-IgGNPs) used as the sensing nanobioprobe. The target anti-p53aAbs from human serum samples is selectively isolated and purified using the MB-p53Ag/BSA. A sandwich-type immunoreaction was achieved via the Fc-specific FITC@SiO2-NH2-anti-IgG binding to the captured anti-p53aAbs. The alkali hydrolysis of the FITC@SiO2-NH2-anti-IgG released FITC molecules, leading to an amplified fluorescence detection signal. The analytical performance evaluated using the FITC@SiO2-NH2-anti-IgGNPs as sensing nanobioprobe, MB-p53Ag/BSA as a nanomagnetic bead, and microwell ELISA plate, MTP-p53Ag/BSA were compared. The proposed immunosensor exhibited linear correlation in two concentration ranges from 1.50 to 500 pg mL-1 and from 0.50 to 100 ng mL-1. The limit of detection (LoD) and limit of quantification were calculated from the lower linear concentration range close to zero (1.50-500 pg mL-1) following a method reported in literature. The LoD was found to be 1.49 pg mL-1 and the limit of quantification was 3.81 pg mL-1. For the microwell ELISA plate assay, the LoD was 42.0 pg mL-1 and the linear range was 1.60-100 ng mL-1. The nanomagnetic capture-based assay time was 50 min, which is quicker than 3 h needed for the microwell ELISA plate assay.

Bioelectrocatalysis and surface analysis of gold coated with nickel oxide/hydroxide and glucose oxidase towards detection of glucose.

The fabricating of metal oxide thin films onto conducting surfaces continues to grow and their potential applications as surfaces for biosensor applications is of paramount importance. The correct orientation of glucose oxidase redox enzymes yields very important biointerfaces capable of selectively detecting d-glucose as a measure of blood sugar for healthy and diabetic sick patients. The electrodeposition of redox enzymes, such as glucose oxidase enzymes, onto gold electrode surfaces pre-modified with nickel oxide was investigated in this work. The surface characterization confirmed the chemical nature, morphology and thin film composition of the modification of bare and modified gold electrodes. The electrodeposition of GOx enzyme onto nickel oxide/hydroxide thin film resulted in a surface with excellent bioelectrocatalytic properties towards the detection of d-glucose. The nickel within the nickel oxide/hydroxide thin film had a Ni(II) oxidation state. A well-defined redox peak of GOx enzyme co-factor (FAD/FADH2) was observed confirming the oriented immobilization onto NiO/Ni(OH)2 conducting surfaces. The amount of GOx enzyme deposited was determined by integrating the charge (Q = 0.368 µF) under the reduction peak and the surface coverage was found to be 1.43 × 10-10 mol. cm-2. A linear plot of electrocatalytic reduction currents against d-glucose concentrations was obtained up to 30.0 mM with a linear correlation coefficient (R2) of 0.99. The limit of detection (LoD) using S/N = 3 was calculated to be 1.54 ± 0.03 mM. The sensitivity of the biosensors was 1.95 ± 0.13 µA.mM.cm-2. The selectivity towards only d-glucose and not ascorbic acid and uric acid was evaluated and the Au-NiO/Ni(OH)2-GOx could not detect 1.0 mM of ascorbic acid and uric acid.

Nanomagnet-Silica Nanoparticles Decorated with Au@Pd for Enhanced Peroxidase-Like Activity and Colorimetric Glucose Sensing.

Nanomagnet-silica shell (Fe3O4@SiO2) decorated with Au@Pd nanoparticles (NPs) were synthesized successfully. The characterization of Fe3O4@SiO2-NH2-Au@PdNPs was achieved using several spectroscopic and microscopic techniques. The quantitative surface analysis was confirmed using X-ray photoelectron spectroscopy. The Fe3O4@SiO2-NH2-Au@Pd0.30NPs exhibited excellent peroxidase-like activity by effectively catalyzing the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2. The absorption peaks at 370 and 652 nm confirmed the peroxidase-like activity of the Fe3O4@SiO2-NH2-Au@Pd0.30NPs. The Michaelis-Menten constant (Km) of 0.350 and 0.090 mM showed strong affinity toward H2O2 and TMB at Fe3O4@SiO2-NH2-Au@Pd0.30NPs. The mechanism of the peroxidase-like activity was found to proceed via an electron transfer process. A simple colorimetric sensor based on glucose oxidase and Fe3O4@SiO2-NH2-Au@Pd0.30NPs showed excellent selectivity and sensitivity towards the detection of glucose. The fabricated glucose biosensor exhibited a wide linear response toward glucose from 0.010 to 60.0 µM with an limit of detection of 60.0 nM and limit of quantification of 200 nM. The colorimetric biosensor based on Fe3O4@SiO2-NH2-Au@Pd0.30NPs as a peroxidase mimic was also successfully applied for the determination of glucose concentrations in serum samples. The synthesized Fe3O4@SiO2-NH2-Au@Pd0.30NPs nanozymes exhibited excellent potential as an alternative to horseradish peroxidase for low-cost glucose monitoring.

Synthesis, characterization of copper oxide-gold nanoalloys and their peroxidase-like activity towards colorimetric detection of hydrogen peroxide and glucose.

Bimetallic copper oxide-gold nanoalloys (CuO-Au nanoalloys) have been prepared and characterized using various techniques confirming their successful synthesis. The peroxidase-like activity of CuO-Au nanoalloys have been investigated and applied towards the colorimetric detection of glucose. CuO-Au nanoalloys as nanoenzymes exhibited peroxidase-like properties which occurred by generating the reactive oxygen species (ROS) due to the catalytic properties of CuO-Au nanoalloys.The generation of ROS was confirmed using radical and/or reactive oxygen species quenching properties of 1,3­diphenylisobenzofuran (DPBF). The rate of production of ROS was higher when CuO-Au nanoalloys were present in a solution containing DPBF and H2O2 (0.1092 min-1). The absorption peak of DPBF at 430 nm decreased confirming the generation of ROS. The CuO-Au nanoalloys were evaluated their potential use for colorimetric detection of glucose. The detection limit for glucose was obtained to be 6.75 µM. The detection of glucose took place in two steps and at different pH conditions, first glucose oxidation by glucose oxidase occurred in physiological pH (7.4) at 37 °C. The optimum conditions for the CuO-Au nanoalloys peroxidase-like activity were obtained at pH 4 and 25 °C. The chromogen, TMB (3,3',5,5'­tetramethylbenzidine) oxidation to blue coloured product TMBDI (3,5,3',5'­tetrabenzidinediimine) occurred with high intensity obtained after 6 min.

Photophysical properties of zinc phthalocyanine-uridine single walled carbon nanotube--conjugates.

The photophysical properties of the conjugate of uridine and zinc mono carboxy phenoxy phthalocyanine (ZnMCPPc-uridine, 4) are reported in this work. The conjugate was also adsorbed onto single walled carbon nanotubes (ZnMCPPc-uridine-SWCNT, 5). The X-ray photoelectron spectroscopy of 4 showed three N 1s peaks while that of 5 showed four N 1s peak, a new peak at 399.4 eV of 5 was assigned to pyrrolidonic nitrogen, due to the interaction of the pyrrolic nitrogen of 4 with the oxygen moiety of SWCNT-COOH in 5. The triplet lifetime, triplet and singlet oxygen quantum yields of the zinc mono carboxy phenoxy phthalocyanine increased by over 40% in the presence of uridine. SWCNTs resulted in only a small quenching of the triplet state parameters of 4.

Electrocatalytic activity of bimetallic Au-Pd nanoparticles in the presence of cobalt tetraaminophthalocyanine.

Au and Pd nanoparticles were individually or together electrodeposited on top of polymerized cobalt tetraaminophthalocyanine (poly-CoTAPc). When Pd and Au nanoparticles are co-deposited together, the electrode is denoted as Au-Pd (co-deposited)/poly-CoTAPc-GCE. X-ray photoelectron spectroscopy (XPS) was used to show the successful deposition of AuNPs, PdNPs and Au-Pd (co-deposited). The scanning electrochemical microscopy showed that Au-Pd (co-deposited)/poly-CoTAPc-GCE (with current range of 9.5-13.5 µA) was more conducting than Au-Pd (co-deposited)-GCE (with current range of 8-12 µA). Electrochemical impedance spectroscopy (EIS) showed that there was less resistance to charge transfer for Au-Pd (co-deposited)/poly-CoTAPc-GCE compared to the rest of the electrodes. Au-Pd (co-deposited)/poly-CoTAPc-GCE showed the best activity for the electrooxidation of hydrazine in terms of limit of detection (0.5 µM), hence shows promise as an electrocatalyst for electrooxidation of hydrazine.

Design and evaluation of an electrochemical immunosensor for measles serodiagnosis using measles-specific Immunoglobulin G antibodies.

The design of electrochemical immunosensors for the detection of measles-specific antibodies is reported. The measles-antigen modified surface was used as an antibody capture surface. The detection of measles-specific IgG antibodies was accomplished using the voltammetric method and horse-radish peroxidase (HRP) labeled secondary antibody (anti-IgG) as a detecting antibody. The potential applications of the designed immunosensor were evaluated in buffer and serum solutions. The immunosensor exhibited good linearity at concentrations less than 100 ng mL(-1) with R(2)=0.997 and the limit of detection of 6.60 ng mL(-1) at 3σ. The potential application of the immunosensor was evaluated in the deliberately infected human and newborn calf serum samples with measles-IgG antibody mimicking real-life samples. The designed electrochemical immunosensor could differentiate between infected and un-infected serum samples as higher catalytic currents were obtained for infected serum samples.

Electrochemical impedimetric immunosensor for the detection of measles-specific IgG antibodies after measles infections.

The detection of measles-specific primary antibodies (IgG) using electrochemical impedimetric immunosensors is reported. The optimum conditions for electrode saturation were reached after 40 min for 1 µg ml(-1) antibody concentrations. Surface roughness using AFM increased with each immobilization or antigen-antibody reaction step clearly confirming the surface modification and recognition between antigen and antibody. The human serum (HS) and new-born calf serum (NCS) spiked with antigen-specific antibody were studied to mimic the real sample analysis. The HS and NCS sera containing antibodies due to measles exhibited correlation between the increasing antibody serum concentrations and the charge-transfer resistance (electrochemically measured). This work clearly showed the potential use of impedance as the preferred electrochemical method for detecting measles-antibodies in label-free manner.

The effects of carbon nanotubes on the electrocatalysis of hydrogen peroxide by metallo-phthalocyanines.

The pre-grafted screen-printed gold electrode modified with phenyl-amino monolayer was investigated for covalent immobilization of phenyl-amine functionalized single-walled carbon nanotubes (PA-SWCNT) and metal tetra-amino phthalocyanine (MTAPc) using Schiff-base reactions with benzene-1,4-dicarbaldehyde (BDCA) as cross-linker. The PA-SWCNT and MTAPc modified electrodes were applied as hybrids for electrochemical sensing of H(2)O(2). The step-by-step fabrication of the electrode was followed using electrochemistry, impedance spectroscopy, scanning electron microscopy and Raman spectroscopy and all these techniques confirmed the fabrication and the immobilization of PA-SWCNT, MnTAPc and CoTAPc onto gold surfaces. The apparent electron transfer constant (k(app)) showed that the carbon nanotubes and metallo-phthalocyanines hybrids possess good electron transfer properties compared to the bare, pre-grafted and the MTAPc modified gold electrode surfaces without PA-SWCNT. The electrochemical sensing of hydrogen peroxide was successful with PA-SWCNT-MTAPc hybrid systems showing higher electrocatalytic currents compared to the other electrodes. The analytical parameters obtained using chronoamperometry gave good linearity at H(2)O(2) concentrations ranging from 1.0 to 30.0 µmol L(-1). The values for the limit of detection (LoD) were found to be of the orders of 10(-7)M using the 3δ for all the electrodes. The PA-SWCNT-MTAPc modified SPAuEs were much more sensitive compared to PA-MTAPc modified SPAuEs.