| 1. |
- Zhybak, Mikael, et al.
(författare)
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Copper/Nafion/PANI Nanocomposite as an electrochemical transducer for creatinine and urea enzymatic biosensing
- 2014
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Ingår i: <em>24th Anniversary World Congress on Biosensors – Biosensors 2014</em>. - : Elsevier.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Chronic Kidney diseases (CKD) affect, to different degrees, ca. 25 million Americans and 19 million Europeans. Monitoring of creatinine and urea levels is of great importance for a correct evaluation of the status of patients and for their treatment. In this paper, we present the development of creatinine and urea enzymatic biosensors, based on a novel ammonium ion-specific Copper/Nafion/Polyanyline (PANI) nanocomposite electrode (Fig. 1A), and suitable for PoC and decentralised diagnostic applications. . Studies on the nanocomposite electrode revealed its high sensitivity and specificity towards ammonium, in respect to amino acids, creatinine and urea, with response range between 5 and 75 μM (Fig. 1B) and with a detection limit of 1 μM. To demonstrate its suitability as transducer in biosensors, creatinine and urea biosensors were fabricated by immobilising creatinine deiminase or urease, respectively, on the nanocomposite surface. Optimisation of the enzyme immobilisation demonstrated that the incorporation of lactitol markedly improved the stability of the biosensors. The response range of the creatinine biosensor was 2 to 100 μM, which fits well with the normal levels of creatinine in healthy people (30-150 µM).The urea biosensor had a response range of 5 to 100 µM. A limit of quantification of 1 µM was achieved for both the biosensors.Evaluation of the performance of the biosensors in real sample matrices and cross reactivity studies are currently on-going. We envisage that the proposed design will be particularly compatible with fully-printed systems thus offering a viable route to the mass production of inexpensive sensors for mobile health.
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| 2. |
- Zhybak, Mykhailo T., et al.
(författare)
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Amperometric L-arginine biosensor based on a novel recombinant arginine deiminase
- 2017
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Ingår i: Microchimica Acta. - : SPRINGER WIEN. - 0026-3672 .- 1436-5073. ; 184:8, s. 2679-2686
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Tidskriftsartikel (refereegranskat)abstract
- The authors describe an amperometric biosensor for the amino acid L-arginine (L-Arg). It is based on the use of a Nafion/Polyaniline (PANi) composite on a platinum screen-printed electrode (Pt-SPE) using a novel recombinant arginine deiminase isolated from Mycoplasma hominis. The protein was over-expressed, purified and employed as a biorecognition element of the sensor. Enzymatic hydrolysis of L-Arg leads to the formation of ammonium ions which diffuse into the Nafion/PANi layer and induce the electroreduction of PANi at a potential of -0.35 V (vs Ag/AgCl). L-Arg sensitivity is 684 +/- 32 A.M-1.m(-2), and the apparent Michaelis-Menten constant K-M(app)) is 0.31 +/- 0.05 mM. The calibration plot is linear over the range 3-200 mu M L-Arg, the limit of detection is 1 mu M, and the response time (for 90% of the total signal change to occur) is 15 s. The sensor is selective and exhibits good storage stability (amp;gt; 1 month without loss in signal). The biosensor was applied to the analysis of L-Arg in pharmaceutical samples and of ammonium and L-Arg in spiked human plasma obtained from blood of healthy volunteers and those with a hepatic disorder. Data generated were found to be in good agreement with a reference fluorometric enzymatic assay.
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| 3. |
- Zhybak, M.T., et al.
(författare)
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Creatinine and urea biosensors based on a novel ammonium ion-selective copper-polyaniline nano-composite
- 2016
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Ingår i: Biosensors & bioelectronics. - : Elsevier. - 0956-5663 .- 1873-4235. ; 77, s. 505-511
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Tidskriftsartikel (refereegranskat)abstract
- The use of a novel ammonium ion-specific copper-polyaniline nano-composite as transducer for hydrolase-based biosensors is proposed. In this work, a combination of creatinine deaminase and urease has been chosen as a model system to demonstrate the construction of urea and creatinine biosensors to illustrate the principle. Immobilisation of enzymes was shown to be a crucial step in the development of the biosensors; the use of glycerol and lactitol as stabilisers resulted in a significant improvement, especially in the case of the creatinine, of the operational stability of the biosensors (from few hours to at least 3 days). The developed biosensors exhibited high selectivity towards creatinine and urea. The sensitivity was found to be 85±3.4 mA M−1 cm−2 for the creatinine biosensor and 112±3.36 mA M−1 cm−2 for the urea biosensor, with apparent Michaelis–Menten constants (KM,app), obtained from the creatinine and urea calibration curves, of 0.163 mM for creatinine deaminase and 0.139 mM for urease, respectively. The biosensors responded linearly over the concentration range 1–125 µM, with a limit of detection of 0.5 µM and a response time of 15 s.The performance of the biosensors in a real sample matrix, serum, was evaluated and a good correlation with standard spectrophotometric clinical laboratory techniques was found.
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| 4. |
- Zhybak, Mykhailo T., et al.
(författare)
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Direct detection of ammonium ion by means of oxygen electrocatalysis at a copper-polyaniline composite on a screen-printed electrode
- 2016
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Ingår i: Microchimica Acta. - : Springer Science and Business Media LLC. - 0026-3672 .- 1436-5073. ; 183:6, s. 1981-1987
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Tidskriftsartikel (refereegranskat)abstract
- We describe a composite material for use in electrochemical oxygen reduction. A screen-printed electrode (SPE) was consecutively modified with electrodeposited copper, a Nafion membrane and electropolymerized polyaniline (PANi) to give an electrocatalytic composite of type PANi/Nafion/Cu2O/SPE that displays good electrical conductivity at neutral pH values. It is found that the presence of ammonia causes complex formation with Cu(I), and this causes electroreduction of oxygen to result in an increased cathodic current. The finding was applied to the quantification of ammonium ions in the 1 to 1000 μM concentration range by amperometry at −0.45 V (vs. Ag/AgCl). This Faradaic phenomenon offers the advantage of direct voltammetric detection, one of the lowest known limits of detection (0.5 μM), and high sensitivity (250 mA∙M−1∙cm−2). It was applied to the determination of ammonium ion in human serum where it compared well with the photometric routine approach for clinical analysis using glutamate dehydrogenase. [Figure not available: see fulltext.]
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| 5. |
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