A novel formaldehyde sensitive biosensor based on bacterial formaldehyde dehydrogenase (FDH) as a bio-recognition element has been developed. The bio-recognition membrane had bi-layer architecture ...and consisted of FDH, cross-linked with albumin, and of the cofactor NAD at a high concentration level (first layer). The second layer was a negatively charged Nafion membrane, which prevented a leakage of negatively charged NAD molecules from the bio-membrane. As transducers, gold electrodes SiO
2/Si/SiO
2/Ti/Au and electrolyte-insulator-semiconductor Si/SiO
2 (EIS) structures have been used. Changes in capacitance and impedance properties of the bio-recognition membrane have been used for monitoring formaldehyde concentration in a bulk solution. It has been shown that formaldehyde can be detected within a concentration range from 1
μM to 20
mM depending on the type of transduction used, with a detection limit of 1 and 100
μM for gold-based and EIS-based transducers, respectively.
Butyryl cholinesterase of different origin along with variations of the time of enzyme immobilization on the potentiometric transducer surface is offered to control the ion sensitive field effect ...transistor (ISFET)-based biosensor sensitivity. Because butyryl cholinesterase has been already used to develop the sensors for heavy metals, organophosphorus/carbamate pesticides, and steroidal glycoalkaloids analysis, the present study has been focused on the investigation and adjustment of the ISFET-based biosensor specificity exclusively to the glycoalkaloids. Utilization of ethylendiaminetetracetate (a complexon of heavy metal ions) and phosphotriesterase (a highly efficient catalyst for the hydrolysis of organophosphorus compounds) enabled the highly specific determination of glycoalkaloids at the background of lead and mercury (up to 500 micromolar of ions concentration) and paraoxon (up to 100 micromolar of pesticide concentration). The developed biosensor has been validated for glycoalkaloids detection in potato varieties cultivated in Ukraine, and the results obtained are compared to those measured by the methods of HPLC and TLC.
The review describes the rationale for the feasibility of assessing the biophoton emissions in chemical and biotechnological research and existing methods. In Part 1, we will present the analysis of ...Meta-Epistemology methods for assessing the biophoton emission. The following stages in the history of the development of methods are identified: First discoveries and formulation of the problem. Pre-paradigm phase. Pre-technical stage (80s of the 18th century – 30s of the 20th century); – Pre-paradigm phase. Technical stage (30s–60s of the XX century); Paradigm scientific phase. The stage of accumulation of scientific data (the 60s–00s of the XX century) is the paradigm scientific phase. Stage of digital technologies and systematic scientific analysis (XXI century). Part 2 will describe the technological features of the methodology and parameters for assessing biophotons, which will allow the use of biophoton emissions in experiments in biotechnological research.
This paper is a review of the authors' publications concerning the development of biosensors based on enzyme field-effect transistors (ENFETs) for direct substrates or inhibitors analysis. Such ...biosensors were designed by using immobilised enzymes and ion-selective field-effect transistors (ISFETs). Highly specific, sensitive, simple, fast and cheap determination of different substances renders them as promising tools in medicine, biotechnology, environmental control, agriculture and the food industry. The biosensors based on ENFETs and direct enzyme analysis for determination of concentrations of different substrates (glucose, urea, penicillin, formaldehyde, creatinine, etc.) have been developed and their laboratory prototypes were fabricated. Improvement of the analytical characteristics of such biosensors may be achieved by using a differential mode of measurement, working solutions with different buffer concentrations and specific agents, negatively or positively charged additional membranes, or genetically modified enzymes. These approaches allow one to decrease the effect of the buffer capacity influence on the sensor response in an aim to increase the sensitivity of the biosensors and to extend their dynamic ranges. Biosensors for the determination of concentrations of different toxic substances (organophosphorous pesticides, heavy metal ions, hypochlorite, glycoalkaloids, etc.) were designed on the basis of reversible and/or irreversible enzyme inhibition effect(s). The conception of an enzymatic multibiosensor for the determination of different toxic substances based on the enzyme inhibition effect is also described. We will discuss the respective advantages and disadvantages of biosensors based on the ENFETs developed and also demonstrate their practical application.
Glucose-sensitive enzyme field effect transistors (ENFETs) modified by an additional Nafion membrane have been developed and used for diluted blood samples analysis. The ENFET was used in the linear ...portion of the calibration curve up to 1.5 mM glucose in a model solution, which corresponds with up to 60 mM glucose in the undiluted samples (dilution 1:40). The high linearity of the Grans curve (factor of linearity is 1.03) obtained by the method of standard additions indicates the high precision of analysis. Glucose concentrations in different blood serum samples determined by ENFETs were compared with those measured by the commercial analyzer ‘Eksan-G’ and colorimetric method (‘Diagluc’ enzymatic kit), and good correlation between these methods was revealed. The high reproducibility and operational stability of the biosensor developed were demonstrated.
A new formaldehyde-selective biosensor was constructed using NAD+- and glutathione-dependent recombinant formaldehyde dehydrogenase as a bio-recognition element immobilised on the surface of ...Si/SiO2/Si3N4 structure. Sensor's response to formaldehyde was evaluated by capacitance measurements. The calibration curves obtained for formaldehyde concentration range from 10μM to 20mM showed a broad linear response with a sensitivity of 31mV/decade and a detection limit about 10μM. It has been shown that the output signal decreases with the increase of borate buffer concentration and the best sensitivity is observed in 2.5mM borate buffer, pH 8.40. The response of the created formaldehyde-sensitive biosensor has also been examined in 2.5mM Tris–HCl buffer, and the shift to the positive bias of the C(V) curves along with the potential axis has been observed, but the sensitivity of the biosensor in this buffer is decreased dramatically to the value of 2.4mV/decade.
The development of sensor microsystems, based on the biological recognition of analytes by sensitive molecules, requires numerical tools for the evaluation of sensor analytical characteristics. A ...digital platform, based on the site-binding model and Mott–Schottky equation, has been developed and used to estimate the responses of semiconductor-based capacitance biosensors for formaldehyde and methylamine determination. It has been demonstrated that the classical site-binding model cannot be applied for the analysis of the sensor behaviour and should be adjusted taking into account the effect of buffer type and its concentration and type as well as membrane composition on the capacitance biosensor response.
Metaphor has been attracting linguists' attention for years, where investigation palm was transferred to a nominal metaphor. Our study aims at describing the metaphorical syntagms, especially a ...predicative syntagm (verbal), and revealing a motivation-demotivation of an element choosing a metaphorical context where semantic and syntactic properties are seen.
Objective of this study is to analyze the range of necrosis after using different freezing times and freeze-thaw cycles during percutaneous cryosurgery, in order to create a suggestion for optimizing ...the technique for lung cryoablation. Six healthy pigs were given a CT scan and histological investigation after percutaneous cryosurgery on both lungs. Three cryoprobes were inserted into both the left and right lungs of each pig, respectively. Cryoablation was performed with two cycles of an active 10-minute freezing using argon in the left lung, each freeze followed by an active 5-minute thaw using helium. In contrast to the left lung cryoablation, the right lungs underwent 3 cycles of freeze/thaw, the first and second cycles consisted of an active 5-minute freezing followed by an active 5-minute thaw, and the third cycle of 10-minute freezing and an active 5-minute thaw. The CT imaging change of an ice ball was continuously observed. The lung tissues were taken 4 hours after cryosurgery on day 3 and on day 7, respectively, for pathological observation. One pig presented acute symptoms including bradycardia and hypothermia 30 minutes after cryosurgery, and died 4 hours after the freezing, and the other 5 pigs experienced a weak condition for 4–6 hours and then exhibited relatively normal behavior and regularly took food. The freezing area (ice ball) on CT imaging during the cryoablation grew gradually in relation to the increase over time, and along with the increase in the number of cycles. The size of the cryolesion on the lung samples became larger than the ice ball during cryosurgery, regardless of whether 2 or 3 freeze-thaw cycles were performed. The area of necrosis histologically gradually increased for the time being. Percutaneous cryosurgery on the lung can achieve complete ablation of targeted tissue. Three freeze-thaw cycles are recommended, and the range of cryoablation may not be mandatory “1 cm safe border” during cryosurgery in order to avoid harming the organ and tissue which is close to the cancer. Correct use of the technique is especially important to treat the lung neoplasms, especially the malignant tumors, which are close to the heart and large vessels.
