Disposable biosensor based on nanodiamond particles, ionic liquid and poly-l-lysine for determination of phenolic compounds.

This study describes the development of a highly sensitive amperometric biosensor for the analysis of phenolic compounds such as catechol. The biosensor architecture is based on the immobilization of tyrosinase (Tyr) on a screen-printed carbon electrode (SPE) modified with nanodiamond particles (ND), 1-butyl-3-methylimidazolium hexafluorophosphate (IL) and poly-l-lysine (PLL). Surface morphologies of the electrodes during the modification process were evaluated by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical characteristics of the modified electrodes. Owing to the synergistic effect of the modification materials, the Tyr/PLL/ND-IL/SPE exhibited high sensitivity (328.2 µA mM-1) towards catechol with a wide linear range (5.0 × 10-8 - 1.2 × 10-5 M) and low detection limit (1.1 × 10-8 M). Furthermore, the method demonstrated good reproducibility and stability. The amperometric response of the biosensor towards other phenolic compounds such as bisphenol A, phenol, p-nitrophenol, m-cresol, p-cresol and o-cresol was also investigated. The analytical applicability of the biosensor was tested by the analysis of catechol in tap water. The results of the tap water analysis showed that the Tyr/PLL/ND-IL/SPE can be used as a practical and effective method for catechol determination.

Disposable biosensor based on ionic liquid, carbon nanofiber and poly(glutamic acid) for tyramine determination.

In this study, an electrochemical biosensor based on carbon nanofibers (CNF), ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (IL), poly(glutamic acid) (PGA) and tyrosinase (Tyr) modified screen printed carbon electrode (SPE) was constructed for tyramine determination. Optimum experimental parameters such as CNF and IL amount, polymerization conditions of glutamic acid, enzyme loading, pH of test solution and operating potential were explored. The construction steps of the Tyr/PGA/CNF-IL/SPE were pursued by scanning electron microscopy and cyclic voltammetry. The Tyr/PGA/CNF-IL/SPE biosensor exhibited linear response to tyramine in the range of 2.0 × 10-7 - 4.8 × 10-5 M with a low detection limit of 9.1 × 10-8 M and sensitivity of 302.6 µA mM-1. The other advantages of Tyr/PGA/CNF-IL/SPE include its high reproducibility, good stability and anti-interference ability. The presented biosensor was also applied for tyramine determination in malt drink and pickle juice samples and mean analytical recoveries of spiked tyramine were calculated as 100.6% and 100.4% respectively.

Disposable glutamate biosensor based on platinum nanoparticles, carbon quantum dots and poly-L-aspartic acid.

This study reports the design and development of a disposable amperometric biosensor for the determination of L-glutamate. Glutamate oxidase (GlOx) was immobilized onto a screen-printed carbon electrode (SPE) modified with poly-L-Aspartic acid (PAsp), carbon quantum dots (CQD), and platinum nanoparticles (PtNP) for the construction of the biosensor. The surface composition of the modified SPE was optimized using the one variable at a time method. The morphological properties of the biosensor were characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The electrochemical behavior of the modified electrodes was studied by cyclic voltammetry. Under the optimized experimental conditions the linear working range, detection limit and sensitivity of the GlOx/PtNP/CQD/PAsp/SPE were found to be 1.0 - 140 µM, 0.3 µM and 0.002 µA µM-1, respectively. The GlOx/PtNP/CQD/PAsp/SPE biosensor also exhibited good measurement repeatability. The as-developed biosensor was applied for the determination of L-glutamate in spiked serum samples and the average analytical recovery of added glutamate was 98.9 ± 3.9%.

Electrochemical (bio)sensors based on carbon quantum dots, ionic liquid and gold nanoparticles for bisphenol A.

Electrochemical (bio)sensors were developed for bisphenol A (BPA) determination. Screen printed carbon electrode (SPCE) was modified with ionic liquid 1- butyl-3-methylimidazolium tetrafluoroborate (IL), carbon quantum dots (CQD) and gold nanoparticles (AuNP) for the fabrication of the BPA sensor. Electrode surface composition was optimized for the deposition time of AuNP, amount of CQD and percentage of IL using the central composite design (CCD) method. The results of the CCD study indicated that maximum amperometric response was recorded when 9.8 µg CQD, 3% IL and 284 s AuNP deposition time were used in modification. Tyrosinase (Ty) was further modified on the AuNP/CQD-IL/SPCE to fabricate the biosensor. Analytical performance characteristics of the BPA sensor were investigated by differential pulse anodic adsorptive stripping voltammetry and the AuNP/CQD-IL/SPCE sensor exhibited a linear response to BPA in the range of 2.0 × 10-8 - 3.6 × 10-6 M with a detection limit of 1.1 × 10-8 M. Amperometric measurements showed that the linear dynamic range and detection limit of the Ty/AuNP/CQD-IL/SPCE were 2.0 × 10-8 - 4.0 × 10-6 M and 6.2 × 10-9 M, respectively. Analytical performance characteristics such as sensitivity, reproducibility and selectivity were investigated for the presented (bio)sensors. The analytical applicability of the (bio)sensors to the analysis of BPA in mineral water samples was also tested.

An amperometric biosensor based on poly(L-aspartic acid), nanodiamond particles, carbon nanofiber, and ascorbate oxidase-modified glassy carbon electrode for the determination of L-ascorbic acid.

An amperometric L-ascorbic acid biosensor utilizing ascorbate oxidase (AOx) immobilized onto poly(L-aspartic acid) (P(L-Asp)) film was fabricated on carbon nanofiber (CNF) and nanodiamond particle (ND)-modified glassy carbon electrode (GCE). Effects of AOx, ND, and CNF amounts were investigated by monitoring the response currents of the biosensor at different amounts of AOx, ND, and CNF. The electropolymerization step of L-aspartic acid on CNF-ND/GCE surface was also optimized. Scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) techniques were used to enlighten the modification steps of the biosensor. The effects of pH and applied potential were studied in detail to achieve the best analytical performance. Under optimized experimental conditions, the AOx/P(L-Asp)/ND-CNF/GCE biosensor showed a linear response to L-ascorbic acid in the range of 2.0 × 10-7-1.8 × 10-3 M with a detection limit of 1.0 × 10-7 M and sensitivity of 105.0 µAmM-1 cm-2. The novel biosensing platform showed good reproducibility and selectivity. The strong interaction between AOx and the P(L-Asp)/ND-CNF matrix was revealed by the high repeatability (3.4%) and good operational stability. The AOx/P(L-Asp)/ND-CNF/GCE biosensor was successfully applied to the determination of L-ascorbic acid in vitamin C effervescent tablet and pharmaceutical powder containing ascorbic acid with good results, which makes it a promising approach for quantification of L-ascorbic acid. Graphical abstract.

Amperometric biogenic amine biosensors based on Prussian blue, indium tin oxide nanoparticles and diamine oxidase- or monoamine oxidase-modified electrodes.

Biogenic amine biosensors, based on screen-printed carbon electrodes (SPCE) modified with Prussian blue (PB) and indium tin oxide nanoparticles (ITONP), are reported. PB/ITONP-modified SPCE was further modified with diamine oxidase (DAO) or monoamine oxidase (MAO) enzymes to construct the biosensors. The morphology of the modified electrodes was studied by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to enlighten the electrochemical properties of the modified electrodes at each step of biosensor fabrication. Electrode surface composition and experimental conditions were optimized and analytical performance characteristics of the biosensors were studied. Several biogenic amines were tested and both biosensors responded to histamine, putrescine and cadaverine. DAO/ITONP/PB/SPCE biosensor exhibited the highest response to histamine 6.0 × 10-6-6.9 × 10-4 M with a sensitivity of 1.84 µA mM-1. On the other hand, the highest sensitivity was obtained for cadaverine with the MAO/ITONP/PB/SPCE biosensor. The analytical utility of the presented biosensors were illustrated by the determination of cadaverine and histamine in cheese sample.

Application of central composite design for the optimization of electrode surface composition for glucose biosensor fabrication.

The use of a central composite design (CCD) for the optimization of electrode surface composition and its application to develop an amperometric glucose biosensor as a model system are described. A five-level three-factorial CCD was applied to determine the optimum electrode surface composition for three critical variables: amounts of carboxylated multiwall carbon nanotubes (c-MWCNT), titanium dioxide nanoparticles (TiO2NP), and glucose oxidase (GOx). The statistical significance of the model and factors were evaluated using the variance analysis (ANOVA) at 95% of confidence level. The optimized electrode surface composition was used for the fabrication of the glucose biosensor. The resulting biosensor showed linear response to glucose from 2.0 × 10-5 to 1.9 × 10-3 M with a detection limit of 2.1 × 10-6 M and sensitivity of 168.5 µA mM-1 cm-2 under optimal experimental conditions. Analytical performance parameters of the biosensor were also compared with those obtained with the glucose biosensors fabricated using the electrode compositions optimized by conventional one factor-at-a-time method and 22 CCD (for c-MWCNT and TiO2NP amounts). The optimization of the critical variables, achieved by CDD, leads us to fabricate the glucose biosensor in the best electrode surface composition which was promoted by the improved analytical performance. The proposed biosensor was applied to the analysis of glucose in serum samples and the obtained results were well correlated with the results of reference method. Graphical abstract ᅟ.

Amperometric L-lysine enzyme electrodes based on carbon nanotube/redox polymer and graphene/carbon nanotube/redox polymer composites.

Highly sensitive L-lysine enzyme electrodes were constructed by using poly(vinylferrocene)-multiwalled carbon nanotubes-gelatine (PVF/MWCNTs-GEL) and poly(vinylferrocene)-multiwalled carbon nanotubes-gelatine-graphene (PVF/MWCNTs-GEL/GR) composites as sensing interfaces and their performances were evaluated. Lysine oxidase (LO) was immobilized onto the composite modified glassy carbon electrodes (GCE) by crosslinking using glutaraldehyde and bovine serum albumin. Effects of pH value, enzyme loading, applied potential, electrode composition, and interfering substances on the amperometric response of the enzyme electrodes were discussed. The analytical characteristics of the enzyme electrodes were also investigated. The linear range, detection limit, and sensitivity of the LO/PVF/MWCNTs-GEL/GCE were 9.9 × 10-7-7.0 × 10-4 M, 1.8 × 10-7 M (S/N = 3), and 13.51 µA mM-1 cm-2, respectively. PVF/MWCNTs-GEL/GR-based L-lysine enzyme electrode showed a short response time (<5 s) and a linear detection range from 9.9 × 10-7 to 7.0 × 10-4 M with good sensitivity of 17.8 µA mM-1 cm-2 and a low detection limit of 9.2 × 10-8 M. The PVF/MWCNTs-GEL/GR composite-based L-lysine enzyme electrode exhibited about 1.3-fold higher sensitivity than its MWCNTs-based counterpart and its detection limit was superior to the MWCNTs-based one. In addition, enzyme electrodes were successfully applied to determine L-lysine in pharmaceutical sample and cheese.

Electrochemical biosensing of galactose based on carbon materials: graphene versus multi-walled carbon nanotubes.

In this study, two enzyme electrodes based on graphene (GR), Co3O4 nanoparticles and chitosan (CS) or multi-walled carbon nanotubes (MWCNTs), Co3O4 nanoparticles, and CS, were fabricated as novel biosensing platforms for galactose determination, and their performances were compared. Galactose oxidase (GaOx) was immobilized onto the electrode surfaces by crosslinking with glutaraldehyde. Optimum working conditions of the biosensors were investigated and the analytical performance of the biosensors was compared with respect to detection limit, linearity, repeatability, and stability. The MWCNTs-based galactose biosensor provided about 1.6-fold higher sensitivity than its graphene counterpart. Moreover, the linear working range and detection limit of the MWCNTs-based galactose biosensor was superior to the graphene-modified biosensor. The successful application of the purposed biosensors for galactose biosensing in human serum samples was also investigated.

Amperometric biosensor for xanthine determination based on Fe3O4 nanoparticles.

An amperometric xanthine biosensor was developed based on the immobilization of xanthine oxidase (XO) into the Fe3O4 nanoparticles modified carbon paste. Electron transfer properties of unmodified and Fe3O4 nanoparticles modified carbon paste electrodes were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Fe3O4 nanoparticles increased electroactive surface area of the electrode and electron transfer at solution/electrode interface. Optimum pH, nanoparticle loading and enzyme loading were found to be 6.0; 14.2% and 0.6 Unit XO respectively. Fe3O4 nanoparticles modified carbon paste enzyme electrode allowed xanthine determination at -0.20 V, thus minimizing the potential interferences from electrochemically oxidizable substances such as ascorbic acid and uric acid. A linear relationship was obtained in the concentration range from 7.4 × 10-7 mol L-1 to 7.5 × 10-5 mol L-1 and a detection limit of 2.0 × 10-7 mol L-1. The biosensor was used for determination of xanthine in urine samples and the results indicate that the biosensor is effective for the detection of xanthine.

Evaluation of the uncertainty budget for 226Ra analysis in water samples.

An alpha spectrometric method for the rapid determination of 226Ra isotope in water samples is presented. The method is based on the co-precipitation of (Ba)(Ra)SO4 for source preparation. The parameters contributing to the uncertainty budget are investigated. Geometry factor (solid angle / 4pi) was used instead of 226Ra standard disc for the determination of detector efficiency. The analytical method has been successfully applied to the determination of 226Ra for water samples in proficiency tests organized by International Atomic Energy Agency (IAEA) and National Physical Laboratory (NPL). The proposed method also showed high reproducibility.

Electrochemical determination of aripiprazole based on aluminium oxide nanoparticles modified carbon paste electrode.

The electrochemical oxidation of aripiprazole was explored at a carbon paste electrode modified with aluminium oxide nanoparticles by cyclic voltammetry and square-wave anodic adsorptive stripping voltammetry. Experimental parameters such as carbon paste composition, scan rate, buffer pH, accumulation time, and accumulation potential were optimized in order to obtain high analytical performance. The incorporation of aluminium oxide nanoparticles into the carbon paste matrix enhanced the effective surface area of the carbon paste electrode and improved the sensitivity. On the aluminium oxide nanoparticles modified carbon paste electrode, aripiprazole exhibited an irreversible anodic peak at +1.17 V in pH 1.8 BR buffer solution. Under optimum conditions, the peak current exhibited a linear dependence with aripiprazole concentration between 0.03 and 8.0 µM with a detection limit of 0.006 µM. The analytical applicability of the voltammetric method was evaluated by quantification of ARP in human serum samples and pharmaceutical formulations.

Amperometric enzyme electrodes for xanthine determination with different mediators.

Two new amperometric carbon paste enzyme electrodes were developed for xanthine determination. 1,4-benzoquinone and poly(vinylferrocene) (PVF) were investigated as mediators. The parameters affecting the analytical performance of the enzyme electrode have been investigated in detail and optimized for modified enzyme electrodes. 1,4-benzoquinone modified enzyme electrode (BQ-CPEE) exhibited linear response from 1.9 × 10-7 M to 5.5 × 10-6 M and from 5.2 × 10-5 M to 8.2 × 10-4 M with a good detection limit of 1.0 × 10-7 M. The linear working range of the PVF modified enzyme electrode was between 1.9 × 10-7-2.1 × 10-6 M, 1.9 × 10-6-1.0 × 10-5 M and 1.1 × 10-4-8.8 × 10-4 M with a detection limit of 1.0 × 10-7 M. Hypoxanthine response of the electrodes was also determined. Modified enzyme electrodes were used for xanthine determination in real samples and good recoveries were obtained.

Disposable biogenic amine biosensors for histamine determination in fish.

This study presents the development of disposable biosensors employed in the determination of histamine in fish samples. Screen printed carbon electrodes (SPCEs) were first modified with a mixture of titanium dioxide nanoparticles (TiO2), carboxylated multiwalled carbon nanotubes (c-MWCNTs), hexaammineruthenium(iii) chloride (RU) and chitosan (CS). Diamine oxidase (DAO) or monoamine oxidase (MAO) enzymes were further immobilized onto the TiO2-c-MWCNT-RU-CS/SPCEs via 1-ethyl-3-(dimethylaminopropyl) carbodiimide hydrochloride (EDC) and hydroxysuccinimide (NHS) chemistry for the fabrication of the biosensors. The morphological and electrochemical properties of the proposed biosensors were studied using scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, cyclic voltammetry (CV), chronoamperometry and electrochemical impedance spectroscopy (EIS). A performance comparison of two biosensors indicated that the one based on DAO had a linear concentration range from 9.9 × 10-6 to 1.1 × 10-3 M and the other based on MAO, from 5.6 × 10-5 to 1.1 × 10-3 M for histamine. The sensitivity of the DAO based biosensor was almost 1.5 times higher than that of the MAO based biosensor. The proposed biosensors were successfully employed to determine histamine in fish samples and the recoveries were between 100.0% and 104.6%.

Graphene and tricobalt tetraoxide nanoparticles based biosensor for electrochemical glutamate sensing.

An amperometric biosensor based on tricobalt tetraoxide nanoparticles (Co3O4), graphene (GR), and chitosan (CS) nanocomposite modified glassy carbon electrode (GCE) for sensitive determination of glutamate was fabricated. Scanning electron microscopy was implemented to characterize morphology of the nanocomposite. The biosensor showed optimum response within 25 s at pH 7.5 and 37 °C, at +0.70 V. The linear working range of biosensor for glutamate was from 4.0 × 10-6 to 6.0 × 10-4 M with a detection limit of 2.0 × 10-6 M and sensitivity of 0.73 µA/mM or 7.37 µA/mMcm2. The relatively low Michaelis-Menten constant (1.09 mM) suggested enhanced enzyme affinity to glutamate. The glutamate biosensor lost 45% of its initial activity after three weeks.

Amperometric uric acid biosensor based on poly(vinylferrocene)-gelatin-carboxylated multiwalled carbon nanotube modified glassy carbon electrode.

In this study, a new uric acid biosensor was constructed based on ferrocene containing polymer poly(vinylferrocene) (PVF), carboxylated multiwalled carbon nanotubes (c-MWCNT) and gelatin (GEL) modified glassy carbon electrode (GCE). Uricase enzyme (UOx) was immobilized covalently through N-ethyl-N'-(3-dimethyaminopropyl) carbodiimide (EDC) and N-hydroxyl succinimide (NHS) chemistry onto c-MWCNT/GEL/PVF/GCE. The c-MWCNT/GEL/PVF composite was characterized by scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. Various experimental parameters such as pH, applied potential, enzyme loading, PVF and c-MWCNT concentration were investigated in detail. Under the optimal conditions the dynamic linear range of uric acid was 2.0×10(-7) M-7.1×10(-4) M (R=0.9993) with the detection limit low to 2.3×10(-8) M. With good selectivity and sensitivity, the biosensor was successfully applied to determine the uric acid in human serum. The results of the biosensor were in good agreement with those obtained from standard method. Therefore, the presented biosensor could be a good promise for practical applications in real samples.

Determination of plutonium isotopes in bilberry using liquid scintillation spectrometry and alpha-particle spectrometry.

This paper presents α-particle spectrometry and liquid scintillation spectrometry methods to determine plutonium isotopes in bilberry. The analytical procedure involves sample preparation steps for ashing, digestion of bilberry samples, radiochemical separation of plutonium radioisotopes and their measurement. The validity of the method was checked for coherence using the ζ test, z-test, relative bias and relative uncertainty outlier tests. The results indicated that the recommended procedures for both measurement systems could be successfully applied for the accurate determination of plutonium activities in bilberry samples.

A review of enzymatic uric acid biosensors based on amperometric detection.

This review summarizes the studies carried on the development of amperometric uric acid biosensors over the past twenty years. Sensing principles, enzyme immobilization techniques, the electrode types, different approaches and various matrices used for biosensor fabrication are presented along with their benefits and limitations. Uric acid biosensors based on different modes of transducing devices such as optical, potentiometric, conductometric are also referred.

Amperometric carbon paste enzyme electrodes with Fe(3)O(4) nanoparticles and 1,4-benzoquinone for glucose determination.

Two new amperometric carbon paste enzyme electrodes including Fe(3)O(4) nanoparticles with and without 1,4-benzoquinone were developed for glucose determination. Electron transfer properties of unmodified and Fe(3)O(4) nanoparticles and/or 1,4-benzoquinone modified carbon paste electrodes were investigated in 0.1 M KCl support electrolyte containing Fe(CN)6(3-/4-) as redox probe by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods. Fe(3)O(4) nanoparticles increased electron transfer at solution/electrode interface. The parameters affecting the analytical performance of the enzyme electrode have been investigated in detail and optimized for Fe(3)O(4) nanoparticle modified enzyme electrode (Fe(3)O(4)-CPEE). Fe(3)O(4) nanoparticles and 1,4-benzoquinone modified enzyme electrode (BQ-Fe(3)O(4)-CPEE) exhibited linear response from 1.9 × 10(-7) M to 3.7 × 10(-6) M, from 7.2 × 10(-6) M to 1.5 × 10(-4) M and from 1.3 × 10(-3) M to 1.2 × 10(-2) M with an excellent detection limit of 1.9 × 10(-8) M. BQ-Fe(3)O(4)-CPEE was used for determination of glucose in serum samples and results were in good agreement with those obtained by spectrophotometric method.

An Fe3O4-nanoparticles-based amperometric biosensor for creatine determination.

An amperometric biosensor for the detection of creatine was designed, based on carbon paste electrode modified with Fe(3)O(4) nanoparticles. Electron transfer properties of unmodified and Fe(3)O(4)-nanoparticles-modified carbon paste electrodes were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods. Fe(3)O(4) nanoparticles increased the surface area and electric conductivity of the electrode, thus enhancing the sensitivity of the electrode. Optimum pH, buffer concentration, working potential and enzyme loading were selected as 7.0; 0.05 mol L(-1); +0.30 V and 2.0 Unit creatinase (CI), 1.0 Unit sarcosine oxidase (SO), respectively. The purposed biosensor exhibited linear response from 2.0 × 10(-7) mol L(-1) to 3.8 × 10(-6) mol L(-1) and from 9.0 × 10(-6) mol L(-1) to 1.2 × 10(-4) mol L(-1) with a detection limit of 2.0 × 10(-7) mol L(-1). Biosensor was used for determination of creatine in commercial creatine powder samples and showed a good sensing performance.