Electrochemical detection of manganese ions using aptamer-based layers

Heavy metals are one of the major pollutants found in drinking water and their abnormal level may pose a threat to human's health and life. Manganese also belongs to heavy metals group, and it is generally used in production of batteries, fertilizers, and ceramics. Even though, Mn is necessary for proper development of central nervous system, its elevated concentration might lead to certain diseases such as epilepsies, cell death in focal cerebral ischemia as well as neurodegenerative diseases such as Huntington and Alzheimer. Hence, it is crucial to elaborate novel methods for manganese ions detection that could be applied for in situ analysis of water samples. Herein, we present the studies on the electrochemical detection of manganese ions using aptamer-modified electrodes. This is the first attempt of application of aptamer strands as receptor layers for electrochemical analysis of manganese ions and for that purpose gold disk electrodes served as transducers, which were further modified with disulfide - based aptamers and 6-mercapto-1-hexanol blocking agent. The electrochemical measurements concerned the choice of the conditions for formation of aptamer receptor layer as well as the type of redox indicator that served as the source of current signal. The studies referred to the definition of aptasensor working parameters including the verification of the possibility of manganese ion detection in cell culture media. It was shown that it was possible to detect Mn2+ ions within 25 nM-1 μM concentration and the proposed aptasensor exhibited high selectivity towards target analyte for which at least 2 - times higher response was recorded than for interfering ions. Moreover, the possibility of Mn2+ detection in real samples was depicted followed by stability and regeneration studies.

Studies on the Aptasensor Miniaturization for Electrochemical Detection of Lead Ions

Lead poses severe effects on living organisms, and since Pb2+ ions tend to accumulate in different organs, it is crucial to monitor Pb2+ concentration in samples such as water and soil. One of the approaches is the utilization of biosensors combined with aptamer-based layers for the electrochemical detection of lead ions. Herein, we present the studies of applying miniaturized screen-printed transducers as solid surfaces to fabricate aptamer layers. As the research is the direct continuation of our previous studies regarding the use of gold disk electrodes, the working parameters of elaborated aptasensors were defined, including the range of linear response (10-100 nM), selectivity as well as stability, regeneration, and feasibility of application for the analysis of real samples. This was achieved using voltammetric techniques including cyclic and square-wave voltammetry in the presence of methylene blue redox indicator.

Cytotoxicity studies of selected cadmium-based quantum dots on 2D vs. 3D cell cultures

In our work, the cytotoxicity of selected, cadmium-based quantum dots with various surface architectures was studied on 3D spheroids.

C57BL/6J mice as a polygenic developmental model of diet-induced obesity

Susceptibility to obesity changes during the course of life. We utilized the C57BL/6J (B6) and 129S mouse as a genetic model for variation in diet‐induced obesity to define the adiposity phenotypes from birth to maturity at 8 weeks‐of‐age. From birth to 8 weeks‐of‐age, both male and female 129S mice had significantly higher fat mass and adiposity index than B6 mice, although they were not obese. After 8 weeks‐of‐age, B6 had greater adiposity/obesity than 129S mice in response to a high fat (HF). We sought to determine the mechanism activating the fat accumulation in B6 mice at 8‐weeks‐of‐age. We used microarray analysis of gene expression during development of inguinal fat to show that molecular networks of lipogenesis were maximally expressed at 8 weeks‐of‐age. In addition, the DNA methylation analysis of the Sfrp5 promoter and binding of acetylated histones to Sfrp5 and Acly promoter regions showed that major differences in the expression of genes of lipogenesis and chromatin structure occur during development. Differences in lipogenesis networks could account for the strain‐dependent differences in adiposity up to 8 weeks‐of‐age; however, changes in the expression of genes in these networks were not associated with the susceptibility to DIO in B6 male mice beyond 8 weeks‐of‐age.

Content of lead and cadmium in aboveground plant organs of grasses growing on the areas adjacent to a route of big traffic

The effect of traffic on the content of lead and cadmium in grass morphological parts-leaves, shoots, and inflorescences-was studied. The samples were taken on a part of the European route E30 (Siedlce by road). The following plants were tested: Dactylis glomerata, Arrhenatherum elatius, and Alopecurus pratensis. During the flowering of grasses, the plant material was collected at distances of 1, 5, 10, and 15 m from the edge of the road, on the strip of road with a length of 9 km. In the collected plant parts, the content of lead and cadmium using the atomic absorption spectroscopy (AAS) method was determined. The effect of distance from the road on the content of lead and cadmium was evaluated using regression equations. Average lead content in the above parts of tested grass species was 3.56, while cadmium 0.307 mg kg(-1) dry matter (DM). Lead content in plants of Alopecurus pratensis (average 4.11 mg kg(-1) DM) was significantly higher than in other grasses. The lowest cadmium content, significantly different from the other species, was found in plants of Arrhenatherum elatius (0.251 mg kg(-1) DM). Distance of sampling sites from the roadway significantly affects the differences in the content of cadmium and lead in plants. Analyzed aboveground plant organs of studied grasses were significantly different in contents of lead and cadmium. There were species differences in the proportions of cadmium concentration in various organs of plants. The obtained results indicate the possibility of species composition selection of grassland sward in areas with a higher risk of heavy metals associated with dust sedimentation.

Expression of adipocyte biomarkers in a primary cell culture models reflects preweaning adipobiology

A cohort of genes was selected to characterize the adipogenic phenotype in primary cell cultures from three tissue sources. We compared the quantitative expression of biomarkers in culture relative to their expression in vivo because the mere presence or absence of expression is minimally informative. Although all biomarkers analyzed have biochemical functions in adipocytes, the expression of some of the biomarkers varied enormously in culture relative to their expression in the adult fat tissues in vivo, i.e. inguinal fat for white adipocytes and brite cells, interscapular brown adipose tissue for brown adipocytes, and ear mesenchymal stem cells for white adipocytes from adult mice. We propose that the pattern of expression in vitro does not reflect gene expression in the adult mouse; rather it is predominantly the expression pattern of adipose tissue of the developing mouse between birth and weaning. The variation in gene expression among fat depots in both human and rodent has been an extensively studied phenomenon, and as recently reviewed, it is related to subphenotypes associated with immune function, the inflammatory response, fat depot blood flow, and insulin sensitivity. We suggest that adipose tissue biology in the period from birth to weaning is not just a staging platform for the emergence of adult white fat but that it has properties to serve the unique needs of energy metabolism in the newborn. A case in point is the differentiation of brite cells that occurs during this period followed by their involution immediately following weaning.

Polyion selective polymeric membrane-based pulstrode as a detector in flow-injection analysis

A method for the detection of polyions using fully reversible polyion selective polymeric membrane type pulstrodes as detectors in a flow-injection analysis (FIA) system is examined. The detection electrode consists of a plasticized polymeric membrane doped with 10 wt % of tridodecylmethylammonium-dinonylnaphthalene sulfonate (TDMA/DNNS) ion-exchanger salt. The pulse sequence used involves a short (1 s) galvanostatic pulse, an open-circuit pulse (0.5 s) during which the EMF of the cell is measured, and a longer (15 s) potentiostatic pulse to return the membrane to its original chemical composition. It is shown that total pulse sequence times can be optimized to yield reproducible real-time detection of injected samples of protamine and heparin at up to 20 samples/h. Further, it is shown that the same membrane detector can be employed for FIA detection of both polycations at levels ≥10 μg/mL and polyanions at levels of ≥40 μg/mL by changing the direction of the galvanostatic pulse. The methodology described may also be applicable in the detection of polyionic species at low levels in other flowing configurations, such as in liquid chromatography and capillary electrophoresis.

Association between vascular endothelial growth factor and hypertension in children and adolescents type I diabetes mellitus

The aim of the study was to analyse the relationship between the serum level of vascular endothelial growth factor (VEGF) and the incidence of hypertension (HT) in children and adolescents with type I diabetes mellitus (T1DM). One hundred and five patients with T1DM were enrolled in the study. The control group consisted of 30 healthy controls. All the T1DM patients were subjected to biochemical analyses, ophthalmologic examination and 24-h blood pressure monitoring. Besides, all the patients and healthy controls had serum VEGF levels measured with the use of the ELISA methodology. The essence of our research is that patients with T1DM and HT and with microalbuminuria (MA) and diabetic retinopathy (DR) (MA/DR) are characterized by a significantly higher level of VEGF (340.23±93.22 pg ml(-1)) in blood serum in comparison with the group of T1DM patients without HT and MA/DR (183.6±96.6 pg ml(-1)) and with healthy controls (145.32±75.58 pg ml(-1)). In addition, the VEGF level was significantly higher in T1DM patients, who presented all three complications, that is HT, retinopathy and MA in comparison with T1DM patients without HT, but with MA/DR (P=0.036). On the other hand, no statistically significant differences (P=0.19) were noted in the level of VEGF in serum between T1DM patients without HT and MA/DR and the healthy control group. At a further stage of analysis, using the method of multiple regression, it was shown that systolic pressure, HbA1c and duration of disease are independent factors influencing the concentration of VEGF. Summarizing, the measurement of VEGF serum levels allows for the identification of groups of patients who have the highest risk of HT and, subsequently, progression of vascular complications.

Enzymatic detection of glucose using fluoride-selective electrodes with polymeric membranes

The feasibility of using polymeric membrane fluoride-selective electrodes based on zirconium(IV) 5,10,15,20-tetraphenylporphyrin as a detector in a flow-injection analysis (FIA) system for glucose determination was examined. The optimization of enzymatic reactions, FIA system configuration and enzyme-immobilization process was performed. It was shown that the resulting flow-injection system exhibits good working parameters, such as reproducibility, linear range of glucose concentration (3 x 10(-3)-10(-1) M), sampling rate (60 samples per minute) and lifetime (over 1 month). The performance of the polymeric membrane electrode was similar to that of a crystalline LaF(3) electrode. The results of glucose determination in synthetic samples with the proposed system show good agreement with real glucose concentrations.

Optical chloride sensor based on dimer-monomer equilibrium of indium(III) octaethylporphyrin in polymeric film

A novel transduction chemistry for preparing optical anion-selective polymeric films that respond reversibly and selectively to chloride ion activity is demonstrated. The chloride sensors are prepared by casting thin (5-10 microm) plasticized PVC films containing indium(III) octaethylporphyrin hydroxide, along with optimized levels of a lipophilic tetraphenylborate salt, onto glass slides. When bathed in low-pH buffered solutions void of chloride, the porphyrin species spontaneously forms a hydroxide ion-bridged dimer, with the added lipophilic borate species serving as the counteranion for this complex. The maximum for the Soret absorption band of this dimeric species is shifted to 390 nm, from 410 nm for the initial monomeric porphyrin. Increases in chloride ion levels in the bathing solution results in chloride extraction and ligation to the In(III) center, and concomitant breaking of the dimer into monomeric porphyrin species, yielding a decrease in absorbance at 390 nm and an increase in optical signal at 410 nm. Under optimized conditions, optical selectivity coefficients toward chloride over a wide range of other anions (NO3-, ClO4-, SCN-, SO4(2-), F-, Br-, H2PO4-) are measured to be < 10(-3). Of all anions tested, only salicylate yields a slightly greater response than chloride. This selectivity is shown to be adequate for reversible and accurate sensing of chloride levels in diluted serum samples.

Total IgE levels and skin test results in children under three years of age with food hypersensitivity

BACKGROUND

The most common tools of allergologic diagnostics are skin prick tests (SPT) and total serum IgE (IgE(total)) determinations.

MATERIAL/METHODS

The study was carried out in a group of 348 children aged 5 to 36 months. All the children underwent SPT using 12 food allergens and in 229 of them also 9 inhalant allergens were tested. Assessment of test positivity utilized relative criteria, i.e. the result was regarded as positive if a wheal with S surface area exceeding or equal to 0.25 of the surface area S0 of a control wheal was formed. In this study group, 291 had IgE(total) levels determined. They were divided into the groups with elevated and normal IgE(total) levels on the basis of two standards, i.e. the standards recommended by the manufacturer of the test reagents used to determine IgE(total) (BioWhittaker) and the population standards.

RESULTS

Positive SPT results for food allergens were obtained in 15.8% of the examined children, for inhalant ones in 21.8%. The factors taken into account in the analysis of impact on SPT results included age, sex, living place and the use diet. Elevated IgE(total) levels according to the manufacturer's standards were detected in 35.0%, and according to the population standards in 67.0% of the examined children. The obtained positive test results were compared with elevated IgE(total) in the studied patients.

CONCLUSIONS

1. Feasibility of SPT at this age. 2. Determination of normal IgE(total) range in the group of children below three requires further studies.

Total IgE levels in children under three years of age

BACKGROUND

The course of type 1 allergic reaction is a result of complex immune processes in which immunoglobulin E plays a crucial role. The serum level of this immunoglobulin (IgE(total)) is closely related to the age of the patient. The presented paper analyses IgE(total) in children below 3.

MATERIAL/METHODS

The study was carried out in group of 291 patients aged 5-39 months. IgE(total) were determined using the Fluoro-FAST 3M. The analysis took into consideration the age, sex and living place of the examined children.

RESULTS

The artmetic mean of IgE(total) was 38.8 +/- 4.0 IU/ml, the median--12 IU/ml, whereas the 5th and 95th percentile values amounted to 1IU/ml and 185 IU/ml, respectively. According to the standards recommended by the manufacturer of reagents used for determination of IgE(total) (Bio Whittaker), 103 children (35.4%) had elevated serum levels of IgE(total), whereas 196 (67.4%) were found to have elevated IgE(total) according to population standards. The obtained percentage distribution of elevated IgE(total) values in particular age groups is characterized by stepwise changes, observed in the age intervals for which the range of values considered as normal by the manufacturer is changed.

CONCLUSIONS

On the basis of analyzed IgE(total) determinations it has been established that the manufacturer's standards for children aged from 2 to 3 years are overestimated, whereas the population standards seem to be underestimated. Therefore, the determination of IgE(total) normal value range requires further studies.

Influence of nonionic surfactants on the potentiometric response of ion-selective polymeric membrane electrodes designed for blood electrolyte measurements

The effect of the nonionic surfactants Brij 35 and Triton X-100 on the selectivity of neutral carrier-based ion-selective electrodes (ISEs) commonly used for measurements of electrolytes in whole blood is investigated. Studies are conducted with plasticized PVC membranes doped with several neutral ionophores commonly employed to prepare clinically useful potassium, calcium, and sodium ISEs. An observed increase in the electrodes' EMF values upon the addition of surfactant to the test solution suggests a change in the ion selectivity of the polymeric membranes in the presence of Brij 35 or Triton X-100. For membranes doped with K(+)-selective valinomycin, the effect of nonionic surfactants is relatively small. However, in the case of calcium-selective membranes prepared with ETH 1001 and ETH 129, nonionic surfactants, especially Triton X-100, decrease the selectivity for calcium over potassium cations by nearly 1 order of magnitude. Such behavior is even more dramatic for sodium-selective membranes, with the degree of surfactant-induced loss of ion selectivity dependent on the specific sodium ionophore employed, the lipophilic tetraphenylborate derivative content of the membrane, and the surfactant type. A detailed theoretical model is presented to explain the effect of nonionic surfactants on the EMF response function of cation-selective polymeric membrane electrodes. Experimental results are in good agreement with theoretical predictions based on known binding constants for ionophores and surfactants with given cations.