Novel formaldehyde-sensitive conductometric biosensors have been developed that are based on commercial bacterial formaldehyde dehydrogenase (FDH) from
Pseudomonas putida
and recombinant formaldehyde ...dehydrogenase (rFDH) from the yeast
Hansenula polymorpha
as the bio-recognition elements. The bio-recognition membranes have mono-layer architecture and consist of enzyme cross-linked with albumin and of the cofactors NAD (for FDH-based sensor) or NAD and glutathione (for rFDH-based sensor). This architecture of the biosensor allows the determination of formaldehyde without adding NAD and glutathione to the analyzed sample at every analysis and conducting measurements on the same transducer without cofactors regeneration since the bio-membrane contains it at high concentration (100 mM for NAD and 20 mM for glutathione). The response is linear in the range from 10 to 200 mM of formaldehyde concentration depending on the enzyme used. The dependence of the biosensor output signals on pH and buffer concentration as well as operational/storage stability and selectivity/specificity of the developed conductometric biosensors have been investigated. The relative standard deviation of the intra-sensor response did not exceed 4% and 10% for rFDH- and FDH-based sensors, respectively. The relative standard deviation of the inter-sensor response constituted 20% for both dehydrogenases used. The biosensors have been validated for formaldehyde detection in some real samples of pharmaceutical (Formidron), disinfectant (Descoton forte) and an industrial product (Formalin). A good correlation does exist between the concentration values measured by the conductometric biosensor developed in this work, an enzymatic method, amperometric biosensors developed earlier, and standard analytical methods of formaldehyde determination.
The possibility to use enzyme field effect transistors for determination of total glycoalkaloids content in real potato samples, without any pre-treatment, has been shown. A measurement protocol for ...such detection has been developed. The possibility and effectiveness of total glycoalkaloids determination in juice samples from different varieties of potatoes with biosensor based on butyryl cholinesterase was evaluated using two biosensor approaches: the method of standard additions and calibration curve application. A good correlation between results obtained with two biosensor approaches and routinely used method have been demonstrated. The biosensor methods proposed are cheap, easy to operate and requires a short analysis time compared to traditional methods for glycoalkaloids determination.
The paper is a review of the researches of Biomolecular Electronics Laboratory concerning the development of biosensors based on electrochemical transducers (amperometric and conductometric ...electrodes, potentiometric pH-sensitive field effect transistors) and different biorecognition molecules (enzymes, cells, antibodies), biomimics (molecularly imprinted polymers), as sensitive elements for direct analysis of substrates or inhibitory analysis of toxicants. Highly specific, sensitive, simple, fast and cheap detection of different substances renders them as promising tools for needs of health care, environmental control, biotechnology, agriculture and food industries. Diverse biosensor formats for direct determination of different analytes and inhibitory enzyme analysis of a number of toxins have been designed and developed. Improvement of their analytical characteristics may be achieved by using differential mode of measurement, negatively or positively charged additional semipermeable membranes, nanomaterials of different origin, genetically modified enzymes. These approaches have been aimed at increasing the sensitivity, selectivity and stability of the biosensors and extending their dynamic ranges. During the last 25 years more than 50 laboratory prototypes of biosensor systems based on mono- and multibiosensors for direct determination of a variety of metabolites and inhibitory analysis of different toxic substances were created. Some of them were tested in real samples analysis. The advantages and disadvantages of the biosensors developed are discussed. The possibility of their practical application is considered.
Media reports of scientific research are a pervasive and important source of new scientific knowledge. Evaluating conclusions found in those reports is an important form of scientific literacy. We ...examined the types of requests for information made by university students as they evaluated scientific news briefs. Students generated a variety of requests for information, focusing more often on HOW the research was conducted and WHY the results might have occurred. Fewer requests were made for information about WHAT was found, WHO conducted the research, and WHERE it was conducted. Least frequent were requests about related research. This pattern of findings may reflect emphasis of instruction in science classrooms. Requests appeared to be influenced by three dimensions of news briefs: plausibility of the conclusion; typicality (the degree to which the phenomena described are typical in biology, chemistry, and physics); and personal familiarity with the phenomena. Individual differences in age, number of science courses completed in university, and degree of belief in paranormal events were correlated with the types of requests made. Models of the evaluative process are needed to gain additional insights into how students' knowledge, dimensions of text, and personal characteristics interact in the course of learning. (Autorenreferat übernommen. Copyright John Wiley & Sons, Inc.).
A cell biosensor specific for formaldehyde was developed using double-mutant cells of the methylotrophic yeast Hansenula polymorpha A3-11. The activities of some of the enzymes in the metabolic ...pathway of the wild-strain cells were deliberately suppressed by introducing respective genetic blocks to optimize the selectivity and acidification rate. Mutant yeast cells produced in this way were immobilized in Ca-alginate gel on the gate of a pH-sensitive field effect transistor. The local acidification of the extracellular medium due to specific conversion of formaldehyde was recorded. The steady-state response time of the biosensor was 2-3 min, i.e., about 10 times shorter than the response time for the alcohol-specific cell biosensors described earlier. The linear dynamic range of the sensor's response corresponds to formaldehyde concentrations of 2 to 200 mM. The operational stability of the sensor was not less than 4 h. The biosensor demonstrated high specificity to formaldehyde with no response to several organic acids, methanol, and other alcohols, except for low sensitivity to ethanol. The influence of sample buffer capacity and pH on the sensor response, as well as thermostability, was investigated.
An extended definition of the term metabolic engineering is given and its successful use in the construction of biorecognition elements of sensors is demonstrated. It is shown that genetic and ...chemical modifications of methylotrophic yeast cells provide directed changes in their physiological responses towards methanol, ethanol and formaldehyde resulting in enhanced selectivity and shorter time response of the corresponding potentiometric and amperometric biosensors.
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