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.

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.

Prevalence of sick building syndrome in hospital staff and its relationship with indoor environmental quality.

The aim of this study was to determine the prevalence of sick building syndrome (SBS), and its relationship with indoor environmental quality in hospital settings. This cross-sectional study was carried out on 300 hospital staff in Sivas. MM 040 NA Hospital questionnaire was applied. In the hospital indoor environments, air quality (carbon monoxide (CO), carbon dioxide (CO2), oxygen (O2), methane (CH4), hydrogen sulfide (H2S), nitrogen oxides (NOx)), lighting, noise, respirable dust and thermal comfort measurements were made. The prevalence of SBS was determined as 64.7-74.1% in the hospitals. It was found that the risk of SBS was 4.31 times higher for those who complained about variable room temperature and 3.11 times higher for those who complained about noise, and decreased 1.01 times with the increase in lighting level. In order to minimize the risk of SBS, it is thought that all healthcare administrators should be informed about SBS.

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.

Dual functional graphene derivative-based electrochemical platforms for detection of the TP53 gene with single nucleotide polymorphism selectivity in biological samples.

Novel disposable electrochemical DNA sensors were prepared for the detection of a target DNA sequence on the p53 tumor suppressor (TP53) gene. The electrochemical platform consisted of screen-printed carbon electrodes (SPCEs) functionalized with a water-soluble reduced graphene oxide-carboxymethylcellulose (rGO-CMC) hybrid nanomaterial. Two different configurations involving hairpin specific capture probes of different length covalently immobilized through carbodiimide chemistry on the surface of rGO-CMC-modified SPCEs were implemented and compared. Upon hybridization, a streptavidin-peroxidase (Strep-HRP) conjugate was employed as an electrochemical indicator. Hybridization was monitored by recording the amperometric responses measured at -0.10 V (vs an Ag pseudo-reference electrode) upon the addition of 3,3',5,5'-tetramethylbenzidine (TMB) as a redox mediator and H2O2 as an enzyme substrate. The implemented DNA platforms allow single nucleotide polymorphism (SNP) discrimination in cDNAs from human breast cancer cell lines, which makes such platforms excellent as new diagnosis tools in clinical analysis.

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.

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.

Prevalence of Burnout, Depression, Anxiety, Stress, and Hopelessness Among Healthcare Workers in COVID-19 Pandemic in Turkey.

BACKGROUND: This study's aim was to reveal the burnout, depression, anxiety, stress, and hopelessness levels of HCWs in the pandemic period. METHODS: The cross-sectional study was carried out with 1015 HCWs, between September 1 and October 1, 2021, in Turkey. Maslach Burnout Inventory, Beck Hopelessness Scale, and Depression Anxiety Stress Scale-21 (DASS-21) were used. RESULTS: Of the HCWs, 56.7% had moderate/high emotional exhaustion (EE), 35.8% had moderate/high depersonalization (D), 58.0% had low personal accomplishment (PA), 34.9% had high depression, 31.9% had high anxiety, 15.4% had high stress, and 33.3% had moderate/severe hopelessness. Risk factors for EE were working in a public hospital, increased workload intensity, decreased income, and difficulty in procuring personal protective equipment (PPE). Risk factors for D were having a male gender, being under the age of 40, being a physician, working in a public hospital, and difficulty in procuring PPE. Risk factors for depression were being under the age of 40, having contact with COVID-19 patients, and decreased income. Risk factors for anxiety were having a female gender, being under the age of 40, working in a public hospital, having a chronic disease, having contact with COVID-19 patients, and having individuals at high risk for COVID-19 at home. Risk factors for hopelessness were having a female gender, being a physician, and increased income. CONCLUSION: The negative effects of the pandemic, which has been going on for over a year and a half, on the mental health of HCWs were high.

A new voltammetric method for the determination of lercanidipine in biological samples.

Electrochemical behavior and adsorption-diffusion properties of lercanidipine (LCN) on a glassy carbon electrode (GCE) were investigated in a mixture of ethanol-Britton Robinson buffer (BR) using voltammetric methods. From experimental results LCN was found to be reduced irreversibly via a single four-electron process controlled mainly by diffusion with some adsorption contribution at about -0.65 V (vs. Ag/AgCl reference electrode). Therefore, a new, accurate, rapid, selective and simple square-wave cathodic adsorptive stripping voltammetric (SWCAdSV) method could be developed for direct determination of LCN in pharmaceutical preparations, spiked human urine and spiked human serum samples without time-consuming steps prior to drug assay. The peak current of the reduction wave linearly changed with the concentration of LCN in the concentration range between 4.0 × 10-8 molL-1 and 7.6 × 10-6 molL-1 in two different regions where optimum preconcentration potential and optimum preconcentration time were applied as -0.20 V and 90 s, respectively. The limit of detection (LOD) and the limit of quantitation (LOQ) values were found to be 2 × 10-8 molL-1 (0.01 mgL-1) and 6 × 10-8 molL-1 (0.04 mgL-1), respectively. The method was applied to determine the content of LCN in commercial pharmaceutical preparation, spiked human serum and spiked human urine. The method was found to be highly accurate and precise, having a relative standard deviation of less than 10% in all applications.

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%.

The protonation equilibria of selected glycine dipeptides in ethanol-water mixture: solvent composition effect.

Knowledge of the protonation constants of small dipeptide is important, interesting and necessary for complete understanding of the physiochemical behavior of dipeptide. In this study, the protonation constants of some aliphatic dipeptides (Gly-Gly, Gly-Val, Gly-Leu, Gly-Thr, Gly-Phe and Gly-Met) were studied in water and ethanol-water mixtures [20% ethanol-80% water, 40% ethanol-60% water, 60% ethanol-40% water, (v/v)] at 25 +/- 0.1 degrees C under nitrogen atmosphere and ionic strength at 0.10 mol dm(-3) by potentiometry. The constants of the systems were calculated by using BEST computer program, and distribution species diagrams were produced using the SPE computer program. The protonation constants were influenced by changes in solvent composition, and their variations were discussed in terms of solvent and structural properties. The concentration distribution of the various species in ethanol-water mixtures was evaluated.

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 biosensors based on carboxylated multiwalled carbon nanotubes-metal oxide nanoparticles-7,7,8,8-tetracyanoquinodimethane composite for the determination of xanthine.

A comparison of the analytical performances of two xanthine biosensors, based on the use of different metal oxide nanoparticles (MONPs: Co3O4 or Fe3O4)-modified carboxylated multiwalled carbon nanotubes (c-MWCNTs)-7,7',8,8'-tetracyanoquinodimethane (TCNQ)-chitosan (CHIT) composite, is discussed. Xanthine oxidase (XOD) enzyme was covalently attached to c-MWCNTs/MONPs/TCNQ/CHIT/GCE via N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS) chemistry and the electrode surface was further modified with Nafion in order to minimize the effect of possible interfering substances. The results showed that analytical performance of the Fe3O4 based biosensor was better than the Co3O4 based biosensor. The linear working range, limit of detection and sensitivity were found to be 1.9×10-6-2.3×10-4M, 0.20µM (S/N=3), 25.07µAmM-1cm-2 for the Fe3O4 based biosensor and 1.9×10-6-1.2×10-4M, 0.36µM (S/N=3), 13.24µAmM-1cm-2 for the Co3O4 based biosensor, respectively. The purposed biosensors were applied in the determination of xanthine in coffee samples, and satisfactory results were obtained.

Health-related Quality of Life and Associated Factors Among Undergraduate University Students.

OBJECTIVES: The aims of this study were to explore factors associated with health-related quality of life (HRQOL) among students of Cumhuriyet University, Turkey. METHODS: This cross-sectional study involved 1751 undergraduate students. HRQOL was measured using the Turkish version of 36-Item Short Form Health Survey questionnaire. We looked at the effect of sociodemographic characteristics (e.g., gender, age, drinking, and smoking) on the individual HRQOL domains. RESULTS: Place of residency (odds ratio (OR) = 3.947 for role emotion dimension), smoking status (OR = -2.756 for role physical dimension), received amount of pocket money (OR = 2.463 for mental health dimension), and body mass index (OR = 1.463 for mental health dimension) were the factors significantly associated with the HRQOL. CONCLUSIONS: Young students' HRQOL is affected by socioeconomic, demographic, and behavioral factors. To improve student's HRQOL, any health-promoting strategies should focus on modifiable risk factors and socioeconomic supports for students.

Electrochemical investigation of 1,3,5-triphenylformazan and its nitro derivatives in dimethyl sulfoxide.

Cyclic voltammetric (CV) and chronoamperometric (CA) behaviors of 1,3,5-triphenylformazan (TPF), 3-(p-nitrophenyl)-1,5-diphenylformazan (PNF) and 3-(m-nitrophenyl)-1,5-diphenylformazan (MNF) were studied in dimethyl sulfoxide medium. TPF was found to give a single sharp cathodic CV peak corresponding to a gain of one-electron per molecule. The diffusion coefficient and the number of electrons transferred were calculated using the Baranski equation with the CV-data obtained by an ultramicroelectrode. Standard rate constants for the reduction were calculated by the Klingler-Kochi technique. The electrochemical data obtained support the mechanism proposed by Umemoto.

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.