Glucose biosensor based on nano-SiO2 and “unprotected” Pt nanoclusters

The “unprotected” Pt nanoclusters (average size 2 nm) mixed with the nanoscale SiO₂ particles (average size 13 nm) were used as a glucose oxidase immobilization carrier to fabricate the amperometric glucose biosensor. The bioactivity of glucose oxidase (GOx) immobilized on the composite was maintained and the as-prepared biosensor demonstrated high sensitivity (3.85 μA mM⁻¹) and good stability in glucose solution. The Pt–SiO₂ biosensor showed a detection limit of 1.5 μM with a linear range from 0.27 to 4.08 mM. In addition, the biosensor can be operated under wide pH range (pH 4.9–7.5) without great changes in its sensitivity. Cyclic voltammetry measurements showed a mixed controlled electrode reaction.     

A novel glucose biosensor based on the immobilization of glucose oxidase onto gold nanoparticles-modified Pb nanowires

A novel glucose biosensor was developed, based on the immobilization of glucose oxidase (GOD) with cross-linking in the matrix of bovine serum albumin (BSA) on a Pt electrode, which was modified with gold nanoparticles decorated Pb nanowires (GNPs-Pb NWs). Pb nanowires (Pb NWs) were synthesized by an l-cysteine-assisted self-assembly route, and then gold nanoparticles (GNPs) were attached onto the nanowire surface through –SH–Au specific interaction. The morphological characterization of GNPs-Pb NWs was examined by transmission electron microscopy (TEM). Cyclic voltammetry and chronoamperometry were used to study and to optimize the electrochemical performance of the resulting biosensor. The synergistic effect of Pb NWs and GNPs made the biosensor exhibit excellent electrocatalytic activity and good response performance to glucose. The effects of pH and applied potential on the amperometric response of the biosensor have been systemically studied. In pH 7.0, the biosensor showed the sensitivity of 135.5 μA mM⁻¹ cm⁻², the detection limit of 2 μM (S/N = 3), and the response time <5 s with a linear range of 5–2200 μM. Furthermore, the biosensor exhibits good reproducibility, long-term stability and relative good anti-interference.     

Application of soil slurry respirometry to optimise and subsequently monitor ex situ bioremediation of hydrocarbon-contaminated soils

A protocol to monitor respiration as O₂ consumption in soil slurries using the Strathtox^® respirometer was developed and tested on four soils from brownfield sites. Respiration rates (mg l⁻¹ h⁻¹) of soil slurries in the Strathtox^® were compared with rates (μl min⁻¹) of field moist soils analysed using the Columbus Oxymax^® ER10 respirometer. One of the soils (99612B), historically contaminated with diesel, was further studied by monitoring the effect of inorganic NH₄NO₃ liquid nutrient on enhancing respiration rate. Soil microcosms were monitored continuously on the Oxymax^® or sampled at 24, 48 and 72 h intervals, prepared as soil slurries, and analysed on the Strathtox^®. On the full-scale remediation project (6000 m³) soil 99612B was treated as a biopile with spent mushroom compost (SMC) amendment and respiration rates monitored in samples over an 8-week period. In the laboratory microcosm experiment and full-scale bioremediation treatment described, correlation was found for respiration rates between the two respirometry systems.     

Zinc oxide/redox mediator composite films-based sensor for electrochemical detection of important biomolecules

Electrochemical oxidation of serotonin (SN) onto zinc oxide (ZnO)-coated glassy carbon electrode (GCE) results in the generation of redox mediators (RMs) that are strongly adsorbed on electrode surface. The electrochemical properties of zinc oxide-electrogenerated redox mediator (ZnO/RM) (inorganic/organic) hybrid film-coated electrode has been studied using cyclic voltammetry (CV). The scanning electron microscope (SEM), atomic force microscope (AFM), and electrochemical techniques proved the immobilization of ZnO/RM core/shell microparticles on the electrode surface. The GCE modified with ZnO/RM hybrid film showed two reversible redox peaks in acidic solution, and the redox peaks were found to be pH dependent with slopes of −62 and −60 mV/pH, which are very close to the Nernst behavior. The GCE/ZnO/RM-modified electrode exhibited excellent electrocatalytic activity toward the oxidations of ascorbic acid (AA), dopamine (DA), and uric acid (UA) in 0.1 M phosphate buffer solution (PBS, pH 7.0). Indeed, ZnO/RM-coated GCE separated the anodic oxidation waves of DA, AA, and UA with well-defined peak separations in their mixture solution. Consequently, the GCE/ZnO/RMs were used for simultaneous detection of DA, AA, and UA in their mixture solution. Using CV, calibration curves for DA, AA, and UA were obtained over the range of 6.0 × 10⁻⁶ to 9.6 × 10⁻⁴ M, 1.5 × 10⁻⁵ to 2.4 × 10⁻⁴ M, and 5.0 × 10⁻⁵ to 8 × 10⁻⁴ M with correlation coefficients of 0.992, 0.991, and 0.989, respectively. Moreover, ZnO/RM-modified GCE had good stability and antifouling properties.     

The chlorophenoxy herbicide dicamba and its commercial formulation banvel induce genotoxicity and cytotoxicity in Chinese hamster ovary (CHO) cells

The sister chromatid exchange (SCE) frequency, the cell-cycle progression analysis, and the single cell gel electrophoresis technique (SCGE, comet assay) were employed as genetic end-points to investigate the geno- and citotoxicity exerted by dicamba and one of its commercial formulation banvel^® (dicamba 57.71%) on Chinese hamster ovary (CHO) cells. Log-phase cells were treated with 1.0–500.0 μg/ml of the herbicides and harvested 24 h later for SCE and cell-cycle progression analyses. All concentrations assessed of both test compounds induced higher SCE frequencies over control values. SCEs increased in a non-dose-dependent manner neither for the pure compound (r = 0.48; P > 0.05) nor for the commercial formulation (r = 0.58, P > 0.05). For the 200.0 μg/ml and 500.0 μg/ml dicamba doses and the 500.0 μg/ml banvel^® dose, a significant delay in the cell-cycle progression was found. A regression test showed that the proliferation rate index decreased as a function of either the concentration of dicamba (r = −0.98, P < 0.05) or banvel^® (r = −0.88, P < 0.01) titrated into cultures in the 1.0–500.0 μg/ml dose-range. SCGE performed on CHO cells after a 90 min pulse-treatment of dicamba and banvel^® within a 50.0–500.0 μg/ml dose-range revealed a clear increase in dicamba-induced DNA damage as an enhancement of the proportion of slightly damaged and damaged cells for all concentrations used (P < 0.01); concomitantly, a decrease of undamaged cells was found over control values (P < 0.01). In banvel^®-treated cells, a similar overall result was registered. Dicamba induced a significant increase both in comet length and width over control values (P < 0.01) regardless of its concentration whereas banvel^® induced the same effect only within 100.0–500.0 μg/ml dose range (P < 0.01). As detected by three highly sensitive bioassays, the present results clearly showed the capability of dicamba and banvel^® to induce DNA and cellular damage on CHO cells.     

A sensitive voltammetric sensor for determination of synthetic corticosteroid triamcinolone, abused for doping

Edge plane pyrolytic graphite electrode (EPPGE) modified with single-wall carbon nanotubes (SWNTs) has been used as a sensor to determine triamcinolone, abused by athletes for doping. A comparison of the voltammetric behavior between SWNTs modified EPPGE and fullerene – C₆₀-modified EPPGE indicated that SWNTs modified EPPGE is more sensitive. The electrode exhibited an effective catalytic response with good reproducibility and stability. The effect of several parameters such as pH, square wave frequency and steroid concentration were studied. The square wave voltammetric response of the electrode to triamcinolone is linear in the range 0.1–25 nM with a detection limit and sensitivity of 8.9 × 10⁻¹⁰ M and 2.06 μA nM⁻¹, respectively. The method was applied for the determination of triamcinolone in several commercially available pharmaceuticals and real urine samples obtained from patients undergoing pharmacological treatment with triamcinolone. A comparison of the observed results with HPLC analysis indicated a good agreement. The product obtained after reduction of triamcinolone was also characterized using ¹H NMR and GC–MS and the site of reduction is found to be carbonyl group at position 20. The method described is rapid, simple and accurate and can be easily applied for detecting cases of doping.     

A nano-Ni based ultrasensitive nonenzymatic electrochemical sensor for glucose: Enhancing sensitivity through a nanowire array strategy

Highly ordered Ni nanowire arrays (NiNWAs) were synthesized for the first time using a template-directed electropolymerization strategy with a nanopore polycarbonate (PC) membrane template, and their morphological characterization were examined by scanning electron microscopy (SEM) and transmission electron microscope (TEM). A NiNWAs based electrode shows very high electrochemical activity for electrocatalytic oxidation of glucose in alkaline medium, which has been utilized as the basis of the fabrication of a nonenzymatic biosensor for electrochemical detection of glucose. The biosensor can be applied to the quantification of glucose with a linear range covering from 5.0 × 10⁻⁷ to 7.0 × 10⁻³ M, a high sensitivity of 1043 μA mM⁻¹ cm⁻², and a low detection limit of 1 × 10⁻⁷ M. The experiment results also showed that the sensor exhibits good reproducibility and long-term stability, as well as high selectivity with no interference from other oxidable species.     

Nonenzymatic glucose sensor based on ultrasonic-electrodeposition of bimetallic PtM (M = Ru, Pd and Au) nanoparticles on carbon nanotubes–ionic liquid composite film

We report here for the first time on the fabrication of highly dispersed PtM (M = Ru, Pd and Au) nanoparticles on composite film of multi-walled carbon nanotubes (MWNTs)–ionic liquid (IL, i.e., trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide) by using ultrasonic-electrodeposition method. The PtM nanoparticles are characterized by scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction, and we find that they are well-dispersed and exhibit alloy properties. Electrochemical experiments show that the PtRu(1:1, i.e., ratio of c(H₂PtCl₆)/c(RuCl₃))–MWNT–IL nanocomposite modified glassy carbon electrode (PtRu(1:1)–MWNT–IL/GCE) has smaller electron transfer resistance and larger active surface area than PtRu(1:1)/GCE, PtRu(1:1)–MWNT/GCE, PtPd(1:1)–MWNT–IL/GCE and PtAu(1:1)–MWNT–IL/GCE. The PtRu(1:1)–MWNT–IL/GCE also presents stronger electrocatalytic activity toward the glucose oxidation than other electrodes. At −0.1 V, the electrode responds linearly to glucose up to 15 mM in neutral media, with a detection limit of 0.05 mM (S/N = 3) and detection sensitivity of 10.7 μA cm⁻² mM⁻¹. Meanwhile, the interference of ascorbic acid, uric acid, acetamidophenol and fructose is effectively avoided. The as-made sensor was applied to the determination of glucose in serum and urine samples. The results agreed closely with the results obtained by a hospital. This novel nonenzyme sensor thus has potential application in glucose detection.     

Polycrystalline bismuth oxide films for development of amperometric biosensor for phenolic compounds

An attractive biocomposite based on polycrystalline bismuth oxide (BiO_x) film and polyphenol oxidase (PPO) was proposed for the construction of a mediator-free amperometric biosensor for phenolic compounds in environmental water samples. The phenolic biosensor could be easily achieved by casting the biocomposite on the surface of glassy carbon electrode (GCE) via the cross-linking step by glutaraldehyde. The laboratory-prepared bismuth oxide semiconductor was polymorphism. Its hydrophilicity provided a favorable microenvironment for retaining the biological activity of the immobilized protein. The parameters of the fabrication process and the various experimental variables for the enzyme electrode were optimized. The proposed PPO/BiO_x biosensor provided a linear response to catechol over a concentration range of 4 × 10⁻⁹ M to 1.5 × 10⁻⁵ M with a dramatically developed sensitivity of 11.3 A M⁻¹ cm⁻² and a detection limit of 1 × 10⁻⁹ M based on S/N = 3. In addition, the PPO/BiO_x biocomposite was characterized by scanning electron microscope (SEM), Fourier transform infrared spectra (FTIR) and rotating disk electrode voltammetry.     

Effect of renoguanylin on hydrogen/bicarbonate ion transport in rat renal tubules

Renoguanylin (REN) is a recently described member of the guanylin family, which was first isolated from eels and is expressed in intestinal and specially kidney tissues. In the present work we evaluate the effects of REN on the mechanisms of hydrogen transport in rat renal tubules by the stationary microperfusion method. We evaluated the effect of 1 μM and 10 μM of renoguanylin (REN) on the reabsorption of bicarbonate in proximal and distal segments and found that there was a significant reduction in bicarbonate reabsorption. In proximal segments, REN promoted a significant effect at both 1 and 10 μM concentrations. Comparing control and REN concentration of 1 μM, JHCO₃⁻, nmol cm^− 2 s^− 1 − 1,76 ± 0,11_control × 1,29 ± 0,08_{REN 10 μM}; P < 0.05, was obtained. In distal segments the effect of both concentrations of REN was also effective, being significant e.g. at a concentration of 1 μM (JHCO₃⁻, nmol cm^− 2 s⁻ 1 − 0.80 ± 0.07_control × 0.60 ± 0.06_{REN 1 μM}; P < 0.05), although at a lower level than in the proximal tubule. Our results suggest that the action of REN on hydrogen transport involves the inhibition of Na⁺/H⁺exchanger and H⁺-ATPase in the luminal membrane of the perfused tubules by a PKG dependent pathway.     

Selective electrochemical sensor for folic acid at physiological pH using ultrathin electropolymerized film of functionalized thiadiazole modified glassy carbon electrode

This paper demonstrated the selective determination of folic acid (FA) in the presence of important physiological interferents, ascorbic acid (AA) and uric acid (UA) at physiological pH using electropolymerized film of 5-amino-2-mercapto-1,3,4-thiadiazole (p-AMT) modified glassy carbon (GC) electrode. Bare GC electrode fails to determine the concentration of FA in the presence of AA and UA due to the surface fouling caused by the oxidized products of AA and FA. However, the p-AMT film modified electrode not only separates the voltammetric signals of AA, UA and FA with potential differences of 170 and 410 mV between AA–UA and UA–FA, respectively but also shows higher oxidation current for these analytes. The p-AMT film modified electrode displays an excellent selectivity towards the determination of FA even in the presence of 200-fold AA and 100-fold UA. Using amperometric method, we achieved the lowest detection of 75 nM UA and 100 nM each AA and FA. The amperometric current response was increased linearly with increasing FA concentration in the range of 1.0 × 10⁻⁷–8.0 × 10⁻⁴ M and the detection limit was found to be 2.3 × 10⁻¹⁰ M (S/N = 3). The practical application of the present modified electrode was successfully demonstrated by determining the concentration of FA in human blood serum samples.     

Variation in domoic acid concentration in king scallop (Pecten maximus) from fishing grounds around the Isle of Man

Domoic acid (DA), the toxin responsible for amnesic shellfish poisoning (ASP) can accumulate in king scallop Pecten maximus leading to extensive fishery closures. Approximately 59% of the total value of all fish and shellfish landed in the Isle of Man in 2004 comprised king scallop, hence the economy of the Manx marine sector is particularly susceptible to impacts from this biotoxin. Scallop from fishing grounds around the Isle of Man were sampled in October 2003, June 2004 and October 2004 to determine levels of inter-animal and spatial variability in DA concentration and factors that might influence toxin concentration such as scallop size and water depth. Mean DA concentrations in hepatopancreas ranged from 296.3 μg g⁻¹ to below the detection limit, in gonad from 27.8 μg g⁻¹ to below the limit of detection and in adductor muscle from 7.3 μg g⁻¹ to below the limit of detection. High levels of inter-animal variability of DA concentration in hepatopancreas were recorded; CVs ranging from 16.1% to 70.0%. DA concentrations above 20 μg g⁻¹ were recorded in gonads on all three sampling dates. Scallops from fishing grounds on the east of the Isle of Man were significantly less contaminated than those from the west and southwest. A significant positive correlation between DA concentration and shell length was recorded in some sites, but there was no relationship with water depth. The high inter-animal, spatial and seasonal variability in toxin concentration highlighted the importance of understanding field variability for the development of reliable sampling and management protocols.     

A novel non-enzymatic ECL sensor for glucose using palladium nanoparticles supported on functional carbon nanotubes

A novel non-enzymatic electrochemiluminescence (ECL) sensor based on palladium nanoparticles (PdNPs)–functional carbon nanotubes (FCNTs) was discovered for glucose detection. PdNPs were homogeneously modified on FCNTs using a facile spontaneous redox reaction method. Their morphologies were characterized by transmission electron microscopy (TEM). Based on ECL experimental results, the PdNPs–FCNTs–Nafion film modified electrode displayed high electrocatalytic activity towards the oxidation of glucose. The free radicals generated by the glucose oxidation reacted with the luminol anion (LH⁻), and enhanced the ECL signal. Under the optimized conditions, the linear response of ECL intensity to glucose concentration was valid in the range from 0.5 to 40 μmol L⁻¹ (r² = 0.9974) with a detection limit (S/N = 3) of 0.09 μmol L⁻¹. In addition, the modified electrode presented high resistance towards the poisoning of chloride ion, high selectivity and long-term stability. In order to verify the sensor reliability, it was applied to the determination of glucose in glucose injection samples. The results indicated that the proposed approach provided a highly sensitive, more facile method with good reproducibility for glucose determination, promising the development of a non-enzymatic ECL glucose sensor.     

Response surface design for the optimization of enzymatic detection of mercury in aqueous solution using immobilized urease from vegetable waste

Soluble and alginate immobilized urease was utilized for detection and quantitation of mercury in aqueous samples. Urease from the seeds of pumpkin, being a vegetable waste, was extracted and purified to apparent homogeneity (sp. activity 353 U/mg protein; A₂₈₀/A₂₆₀ = 1.12) by heat treatment at 48 ± 0.1 °C and gel filtration through Sephadex G-200. Homogeneous enzyme preparation was immobilized in 3.5% alginate leading to 86% immobilization, no leaching of enzyme was found over a period of 15 days at 4 °C. Urease catalyzed urea hydrolysis by soluble and immobilized enzyme revealed a clear dependence on the concentration of Hg²⁺. Inhibition caused by Hg²⁺ was non-competitive (K_i = 1.2 × 10⁻¹ μM for soluble and 1.46 × 10⁻¹ μM for alginate immobilized urease.). Time-dependent inhibition both in presence and in absence of Hg²⁺ ion revealed a biphasic inhibition in activity. For optimization of this process response surface methodology (RSM) was utilized where two-level-two-full factorial (2²) central composite design (CCD) has been employed. The regression equation and analysis of variance (ANOVA) were obtained using MINITAB^® 15 software. Predicted values thus obtained were closed to experimental value indicating suitability of the model. 3D response surface plot, iso-response contour plot and process optimization curve were helpful to predict the results by performing only limited set of experiments.     

Blooms of Pseudo-nitzschia and domoic acid in the San Pedro Channel and Los Angeles harbor areas of the Southern California Bight, 2003–2004

Abundances of Pseudo-nitzschia spp. and concentrations of particulate domoic acid (DA) were determined in the Southern California Bight (SCB) along the coasts of Los Angeles and Orange Counties during spring and summer of 2003 and 2004. At least 1500 km² were affected by a toxic event in May/June of 2003 when some of the highest particulate DA concentrations reported for US coastal waters were measured inside the Los Angeles harbor (12.7 μg DA L⁻¹). Particulate DA levels were an order of magnitude lower in spring of 2004 (February and March), but DA concentrations per cell at several sampling stations during 2004 exceeded previously reported maxima for natural populations of Pseudo-nitzschia (mean = 24 pg DA cell⁻¹, range = 0–117 pg DA cell⁻¹). Pseudo-nitzschia australis dominated the Pseudo-nitzschia assemblage in spring 2004. Overall, DA-poisoning was implicated in >1400 mammal stranding incidents within the SCB during 2003 and 2004. Ancillary physical and chemical data obtained during our regional surveys in 2004 revealed that Pseudo-nitzschia abundances, particulate DA and cellular DA concentrations were inversely correlated with concentrations of silicic acid, nitrogen and phosphate, and to specific nutrient ratios. Particulate DA was detected in sediment traps deployed at 550 and 800 m depth during spring of 2004 (0.29–7.6 μg DA (g sediment dry weight)⁻¹). The highest DA concentration in the traps was measured within 1 week of dramatic decreases in the abundances of Pseudo-nitzschia in surface waters. To our knowledge these are the deepest sediment trap collections from which DA has been detected. Sinking of the spring Pseudo-nitzschia bloom may constitute a potentially important link between DA production in surface waters and benthic communities in the coastal ocean near Los Angeles. Our study indicates that toxic blooms of Pseudo-nitzschia are a recurring phenomenon along one of the most densely populated coastal stretches of the SCB and that the severity and magnitude of these events can be comparable to or greater than these events in other geographical regions affected by domoic acid.     

Vitamin B(12) incorporated with multiwalled carbon nanotube composite film for the determination of hydrazine

Electrochemically active composite film containing multiwalled carbon nanotubes (MWCNTs) and vitamin B₁₂ was synthesized on glassy carbon, gold, and indium tin oxide electrodes by the potentiodynamic method. The presence of MWCNTs in the composite film (MWCNT–B₁₂) modified electrode mediates vitamin B₁₂’s redox reaction, whereas vitamin B₁₂’s redox reaction does not occur at bare electrode. The electrochemical impedance spectroscopy studies reveal that MWCNTs present in MWCNT–B₁₂ film enhance electron shuttling between the reactant and electrode surface. The surface morphology of bare electrode, MWCNT film. and MWCNT–B₁₂ composite film was studied using atomic force microscopy, which reveals vitamin B₁₂ incorporated with MWCNTs. The MWCNT–B₁₂ composite film exhibits promising enhanced electrocatalysis toward hydrazine. The electrocatalysis response of hydrazine at MWCNT film and MWCNT–B₁₂ composite film was measured using cyclic voltammetry and amperometric current–time (i–t) curve techniques. The linear concentration range of hydrazine obtained at MWCNT–B₁₂ composite film using the i–t curve technique is 2.0 μM–1.95 mM. Similarly, the sensitivity of MWCNT–B₁₂ composite film for hydrazine determination using the i–t curve technique is 1.32 mA mM⁻¹ cm⁻², and the hydrazine’s limit of detection at MWCNT–B₁₂ composite film is 0.7 μM.     

Glucose biosensor based on immobilization of glucose oxidase in poly(o-aminophenol) film on polypyrrole-Pt nanocomposite modified glassy carbon electrode

Novel Pt nanoclusters embedded polypyrrole nanowires (PPy-Pt) composite was electrosynthesized on a glassy carbon electrode, denoted as PPy-Pt/GCE. A glucose biosensor was further fabricated based on immobilization of glucose oxidase (GOD) in an electropolymerized non-conducting poly(o-aminophenol) (POAP) film that was deposited on the PPy-Pt/GCE. The morphologies of the PPy nanowires and PPy-Pt nanocomposite were characterized by field emission scanning electron microscope (FE-SEM). Effect of experimental conditions involving the cycle numbers for POAP deposition and Pt nanoclusters deposition, applied potential used in glucose determination, temperature and pH value of the detection solution were investigated for optimization. The biosensor exhibited an excellent current response to glucose over a wide linear range from 1.5 × 10⁻⁶ to 1.3 × 10⁻² M (r = 0.9982) with a detection limit of 4.5 × 10⁻⁷ M (s/n = 3). Based on the combination of permselectivity of the POAP and the PPy films, the sensor had good anti-interference ability to ascorbic acid (AA), uric acid (UA) and acetaminophen. The apparent Michaelis–Menten constant (K_m) and the maximum current density (I_m) were estimated to be 23.9 mM and 378 μA/cm², respectively. In addition, the biosensor had also good sensitivity, stability and reproducibility.     

Development and characterization in vitro of a catalase-based biosensor for hydrogen peroxide monitoring

There is increasing evidence that hydrogen peroxide (H₂O₂) may act as a neuromodulator in the brain, as well as contributing to neurodegeneration in diseased states, such as Parkinson's disease. The ability to monitor changes in endogenous H₂O₂ in vivo with high temporal resolution is essential in order to further elucidate the roles of H₂O₂ in the central nervous system. Here, we describe the in vitro characterization of an implantable catalase-based H₂O₂ biosensor. The biosensor comprises two amperometric electrodes, one with catalase immobilized on the surface and one without enzyme (blank). The analytical signal is then the difference between the two electrodes. The H₂O₂ sensitivity of various designs was compared, and ranged from 0 to 56 ± 4 mA cm⁻² M⁻¹. The most successful design incorporated a Nafion^® layer followed by a poly-o-phenylenediamine (PPD) polymer layer. Catalase was adsorbed onto the PPD layer and then cross-linked with glutaraldehyde. The ability of the biosensors to exclude interference from ascorbic acid, and other interference species found in vivo, was also tested. A variety of the catalase-based biosensor designs described here show promise for in vivo monitoring of endogenous H₂O₂ in the brain.     

Electrogenerated chemiluminescence ethanol biosensor based on alcohol dehydrogenase functionalized Ru(bpy)3 doped silica nanoparticles

An ethanol biosensor, based on the electrogenerated chemiluminescence of Ru(bpy)₃²⁺-doped silica nanoparticles (RuSiNPs), was investigated in this study. The biosensor was a modified glassy carbon electrode, where alcohol dehydrogenase was crosslinked to RuSiNPs, and then immobilized on the electrode surface using chitosan. The results indicated that the biosensor exhibited excellent performance during ethanol determination with a wide linear range (10⁻⁷ to 10⁻² M), low detection limit (5.0 × 10⁻⁸ M) and good stability.     

ICChI, a glycosylated chitinase from the latex of Ipomoea carnea

A multi-functional enzyme ICChI with chitinase/lysozyme/exochitinase activity from the latex of Ipomoea carnea subsp. fistulosa was purified to homogeneity using ammonium sulphate precipitation, hydrophobic interaction and size exclusion chromatography. The enzyme is glycosylated (14–15%), has a molecular mass of 34.94 kDa (MALDI–TOF) and an isoelectric point of pH 5.3. The enzyme is stable in pH range 5.0–9.0, 80 °C and the optimal activity is observed at pH 6.0 and 60 °C. Using p-nitrophenyl-N-acetyl-β-d-glucosaminide, the kinetic parameters K_m, V_max, K_cat and specificity constant of the enzyme were calculated as 0.5 mM, 2.5 × 10⁻⁸ mol min⁻¹ μg enzyme⁻¹, 29.0 s⁻¹ and 58.0 mM⁻¹ s⁻¹ respectively. The extinction coefficient was estimated as 20.56 M⁻¹ cm⁻¹. The protein contains eight tryptophan, 20 tyrosine and six cysteine residues forming three disulfide bridges. The polyclonal antibodies raised and immunodiffusion suggests that the antigenic determinants of ICChI are unique. The first fifteen N-terminal residues G–E–I–A–I–Y–W–G–Q–N–G–G–E–G–S exhibited considerable similarity to other known chitinases. Owing to these unique properties the reported enzyme would find applications in agricultural, pharmaceutical, biomedical and biotechnological fields.