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1

Optical properties of (3-(acetamidomethyl)phenyl)boronic acid and its interactions with selected sugars

Kur K., Przybyt M., Miller E.

Biotechnology and Food Science

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2018

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Vol. 82, nr 1

15--27

EN

(3-(Acetamidomethyl)phenyl)boronic acid (3AAPBA)has at pH 7 absorbance maximum at 270 nm with molar absorbance coefficient 516 M-1cm-1. 3AAPBA exhibits weak fluorescence with maximum at 297 nm and quantum yield 0.062 ± 0.001. Fluorescence decay is monoexponential and the lifetime is 2.05 ± 0.01 ns. Interactions of 3AAPBA with selected sugars were studied by absorbance, steady-state and time-resolved fluorescence measurements. At pH 7 fluorescence of 3AAPBA is quenched only by fructose (with quenching constant 67.9 M-1) and to some extend by galactose. Addition of these two monosaccharides causes also changes of absorbance spectra of 3AAPBA. Acid-base dissociation of free 3AAPBA and its esters with sugars was studied by absorbance and steady-state fluorescence measurements in pH range from 4.5 to 11.00. Esterification of phenylboronic acid derivatives by sugars leads to increased acidity of them. In case of 3AAPBA the obtained values of pK indicate that affinity of studied sugars towards it can be ordered as follows: fructose > galactose > glucose > maltose > lactose > sucrose. At pHs higher than pK the fluorescence decays turn to biexponential with additional shorter component in lifetime which we propose to attribute to anionic form of 3AAPBA or its esters.

2

ZnS Cu-doped quantum dots

Ziółczyk P., Miller E., Przybyt M.

Biotechnology and Food Science

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2014

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Vol. 78, nr 1

53--69

EN

The paper presents a survey of literature on the structure and optical properties of ZnS and copper ion-doped ZnS quantum dots. The effect of other metal dopants on the spectral properties of ZnS:Cu quantum dots was also considered. The influence of such parameters as dopant concentration, temperature of the synthesis and compounds which form or modify the additional layer on dots on spectral properties of the quantum dots was described. Examples of application of ZnS:Cu quantum dots are also given.

3

The study of phenylboronic acid optical properties towards creation of a glucose sensor

Kur-Kowalska K., Przybyt M., Miller E.

Biotechnology and Food Science

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2014

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Vol. 78, nr 2

101--110

EN

The article presents influence of pH and glucose concentration on phenylboronic acid (PBA) fluorescence studied by steady-state and time-resolved measurements. Fluorescence of PBA decreases with growing pH. These changes reflected acid-base equilibrium of PBA and allowed to estimate value of pKd as 9.2, which is comparable with literature data. Fluorescence intensity of phenylboronic acid is quenched in presence of glucose. The effect of quenching is more pronounced with increasing pH. At pH 7 quenching can be described by Stern-Volmer equation, at pH 8 and 9 by modified one. The obtained quenching constants are growing with pH increase. The quenching of phenylboronic acid fluorescence by glucose is a static one, which is confirmed by time-resolved measurements. Two lifetimes were found for fluorescence decay of phenylboronic acid. The lifetimes are practically independent on pH and glucose concentration and also fraction of both lifetimes are nearly the same. The obtained Stern-Volmer constants can be interpreted as apparent equilibrium constants of ester formation between acid and glucose.

4

Lactate biosensors for food industry

Przybyt M.

Biotechnology and Food Science

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2014

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Vol. 78, nr 1

71--88

EN

Lactic acid and lactate fermentation play important role in food and beverages production, control and quality. Analysis of lactate by standard methods is time, work consuming, and cannot be implemented at the production site. The alternative is the use of biosensors for lactate. The article reviews the biosensors for D- and L-lactic assay, their types, construction and application in food analysis area. The special emphasis is given to the commercial biosensor for lactate. The market survey indicates that there is a lack of lactate biosensors addressed to food industry except wine production. QUALI_JUICE project was the practical attempt to use some of the commercial biosensors in production and quality control in fruit juice industry. The results of the project indicates that commercial biosensors can be used after some minor functional adaptation in fruit juice production control. The application of these biosensors can be broadened to the other sectors of food and beverage industry.

5

Potentiometric tungsten electrodes with enzymes immobilised by the sol-gel technique

Przybyt M.

Materials Science

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2003

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Vol. 21, No. 4

417-429

EN

The application of sol-gel transitions in development of potentiometric enzyme electrodes with urease, glucose oxidase and tyrosinase is described. Urease and glucose oxidase electrodes showed features of typical potentiometric electrodes with the response modified by the change of pH. The slopes of calibration curves in semilogarithmic coordinates were lower than the Nernstian values and the dynamic ranges were narrow for both electrodes. The tyrosinase electrode shows response to mono- and o-diphenols. The response of this electrode is not connected with the pH changes. The mechanism of the response of the tyrosinase electrode is discussed; it is proposed that the potential changes reflect the redox state of the enzyme. The electrode responds to reactant concentration (phenol, catechol and some others) even at concentrations 210-6 M. Such a high sensitivity makes the electrode a promising candidate for application in detecting traces of phenols.

6

Behaviour of glucose oxidase during formation and ageing of silica gel studied by fluorescence spectroscopy

Przybyt M.

Materials Science

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2003

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Vol. 21, No. 4

397-416

EN

Glucose oxidase was entrapped in silica gels obtained by the sol-gel process with the retention of a part of its activity. The stability of the enzyme molecule during the sol-gel transition and ageing of the wet gel was followed by the measurement of fluorescence of tryptophan and flavin adeninedinucleotide (FAD). The results indicate unfolding and denaturation of the enzyme protein caused by the changes of microenvironment inside gel, presence of ethanol, decomposition of FAD and photosensitised oxidation of tryptophan by FAD. Among the products of FAD decomposition, alloxazine derivatives were identified through their specific fluorescence characteristics. The results of the observation of the fluorescencje variation and activity assay of the gel are in good agreement. The experiments with the dried gel indicato that illumination is not necessary to sensitise the reaction of oxidation of tryptophane by FAD although In the presence of light the effectiveness of this process is higher. Presumably the decomposition of FAD and tryptophan is not only induced by light but also by the paramagnetic (with free radical character) defects in the gel matrix. This reaction is enhanced by the presence of glucose and depends also on pH of the buffer used in the gel preparation. The products of the enzyme degradation are easily washed out from the gel. Leaching of active enzyme from the gel was also observed.

7

Enzyme electrodes constructed on basis of oxygen electrode with oxidases immobilised by sol-gel technique

Przybyt M., Białkowska B.

Materials Science

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2002

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Vol. 20, No. 2

63-79

EN

In this work, results of immobilisation of enzymes in silica gel on oxygen electrode are reported. As the model enzyme glucose oxidase was used. The influence of the composition of the casting solution (gel precursor, pH of the enzyme solution, sol-buffer ratio) on the electrode response was investigated. Also, the addition of ?-aminopropyltriethoxy silane to the casting solution was checked. The best electrode with stable signal was obtained, when the formed gel was not very rigid (buffer, pH 6 or 7 and high buffer-sol ratio). For the optimal composition of the casting solution, some properties of the glucose electrode were investigated (stability, pH profile and influence of temperature). The method of sol-gel entrappment was also used to obtain the electrodes sensitive for disaccharides by coimmobilisation of invertase, lactase and maltase with glucose oxidase. In addition, preliminary results for other oxidases immobilised by this method are presented.

8

Zastosowanie biosensorów w analizie środków spożywczych Część J. Definicja i zasady działania biosensorów

Przybyt M.

Przemysł Spożywczy

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1999

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T. 53, nr 6

32-35

PL

Przedstawiono możliwości zastosowania biosensorów w analizie żywności. Omówiono definicję biosensora, ich podział oraz zasady działania amperometrycznych elektrod enzymatycznych i sensorów powinowactwa opartych na powierzchniowym rezonansie plazmowym.

EN

Some potential applications of biosensors in food analysis are shown. The definition of a biosensor and classification of these instruments is presented. The operating principles of amperometric enzyme electrodes and affinity sensors using technique of surface plasmon resonance are discussed.

9

Zastosowanie biosensorów w analizie środków spożywczych Część II. Rynek biosensorów

Przybyt M.

Przemysł Spożywczy

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1999

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T. 53, nr 7

35-36

PL

Podano szacunkowy stan rynku biosensorów. Przedstawiono przykłady biosensorów znajdujących się w sprzedaży. Omówiono przykłady zastosowania elektrod enzymatycznych w analizie żywności do oznaczania cukrów, alkoholu, mleczanów, amin i innych. Podano przykłady zastosowania techniki SPR do oznaczania mniejszościowych składników żywności. Pokrótce opisano konstrukcje i zastosowanie "sztucznego nosa".

EN

The state of biosensor market was assayed in the paper. The examples of commercial biosensors were given. The examples of application of enzymatic electrodes to assay sugars, alcohol, lactate, amines and other chemicals in food were discussed. The application of SPR technique in assay of minor constituents of food was presented. The construction and application of "artificial nose" was briefly discussed.

10

Glucose assay in food products in flow system with glucose electrode

Przybyt M.

Zeszyty Naukowe. Chemia Spożywcza i Biotechnologia / Politechnika Łódzka

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1998

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Z. 58

53-67

EN

The application of the galvanic glucose electrode in the flow system to assay glucose concentration in food products is presented. The influence of measurement conditions (temperature, pH, flow rate and sample volume) on the electrode response was studied. The flow system is cheap and easy to handle but needs the exact control of temperature and flow rate. The response time in the optimal conditions is about 5 minutes. Glucose was assayed in juices, honey and drops in the flow system and enzymaticaly with glucose kit showing good correlation of both methods.

PL

Opisane jest zastosowanie galwanicznej elektrody glukozowej w układzie przepływowym. Badano wpływ warunków pomiarowych (temperatury, pH, szybkości przepływu i objętości próbki) na odpowiedź elektrody (wysokość i powierzchnie piku). Stwierdzono, że wszystkie czynniki zwiększające szybkość reakcji na elektrodzie zwiększają jej odpowiedź, skracając jednocześnie czas odpowiedzi i liniowy zakres krzywych kalibracyjnych. Wpływ ten zawsze silniej jest wyrażony dla wysokości piku niż dla jego powierzchni. Badany układ przepływowy jest tani i łatwy w obsłudze ale wymaga dokładnej kontroli temperatury i szybkości przepływu. Czas odpowiedzi elektrody w warunkach optymalnych wynosi około 5 minut. Badano zawartość glukozy w sokach owocowych, miodzie i landrynkach stosując układ przepływowy i test enzymatyczny otrzymując zgodne wyniki.