| 1. |
|
|
| 2. |
- Bjelosevic, Haris, et al.
(författare)
-
Synthesis and structural characterisation of novel platinum-based drug candidates with extended functionality by incorporation of bis(diphenylphosphino)ferrocene units as metal chelators
- 2006
-
Ingår i: Tetrahedron. - : Elsevier BV. - 0040-4020. ; 62:18, s. 4519-4527
-
Tidskriftsartikel (refereegranskat)abstract
- Among the metal-based anticancer drugs, cisplatin (cis-diaminedichloroplatinum(II)) is the most widely used species in therapy. Despite its clinical success, cisplatin still suffers in generating resistance, as well as being highly toxic due to poor selectivity between healthy and sick cells. By molecular design it ought to be possible to generate new cis-platinum compounds with increased selectivity and improved cellular behaviour. In this paper, we report a synthetic pathway for construction of derivatives of 1,1'-bis(diphenylphosphino)-ferrocene, together with their corresponding cis-platinum compounds with the aim testing them for their interaction capacity with respect to various DNA models. We also report a synthetic route for a nucleoside-based cis-platinum compound containing a bidentate ferrocenylphosphine derivative connected through a succinamic-based linker to the 5-position of the heterocyclic moiety of uridine. Our preliminary kinetic investigation of 5-{N-[1-[1',2-bis(diphenylphosphino)ferrocenyl]ethyl]1-N'-[prop-2-yn-3-y l]succinamide} uridinedichloroplatinum(II) showed that this compound reacted faster with the phosphorothioate containing oligonucleotides d(T(6)p(S)T-6), with an observed first-order rate constant k(obs) = (1.4 +/- 0.1) X 10(-4) s(-1), compared with the G-N7 target in d(T(7)GGT(7)), for which the observed first-order rate constant is k(obs) = (7.2 +/- 0.5) X 10(-4) s(-1). (c) 2006 Elsevier Ltd. All rights reserved.
|
|
| 3. |
- Heiskanen, Arto, et al.
(författare)
-
Amperometric monitoring of redox activity in living yeast cells: comparison of menadione and menadione sodium bisulfite as electron transfer mediators
- 2004
-
Ingår i: Electrochemistry Communications. - : Elsevier BV. - 1388-2481. ; 6:2, s. 219-224
-
Tidskriftsartikel (refereegranskat)abstract
- An amperometric method was applied for real-time monitoring of intracellular redox enzyme activity. Baker’s yeast (Saccharomyces cerevisiae) cells were immobilized on platinum microband electrodes and mediated anodic currents were measured. The currents were observed in the absence and in the presence of glucose as a source of reducing equivalents, NADH and NADPH. 2-Methyl-1,4-naphthoquinone (menadione, vitamin K3) and water soluble 2-methyl-1,4-naphthoquinone sodium bisulfite (menadione sodium bisulfite MSB) were compared as artificial electron acceptors for their ability to transduce internal cellular redox activity into electrode current. It was found that hydrophobic menadione was superior to its water-soluble bisulfite derivative for probing whole intact cells.
|
|
| 4. |
- Heiskanen, Arto, et al.
(författare)
-
Mediator-assisted simultaneous probing of cytosolic and mitochondrial redox activity in living cells.
- 2009
-
Ingår i: Analytical Biochemistry. - : Elsevier BV. - 1096-0309 .- 0003-2697. ; 384:1, s. 11-19
-
Tidskriftsartikel (refereegranskat)abstract
- This work describes an electron transfer mediator-assisted amperometric flow injection method for assessing redox enzyme activity in different subcellular compartments of the phosphoglucose isomerase deletion mutant strain of Saccharomyces cerevisiae, EBY44. The method is demonstrated using the ferricyanide-menadione double mediator system to study the effect of dicoumarol, an inhibitor of cytosolic and mitochondrial oxidoreductases and an uncoupler of the electron transport chain. Evaluation of the role of NAD(P)H-producing pathways in mediating biological effects is facilitated by introducing either fructose or glucose as the carbon source, yielding either NADH or NADPH through the glycolytic or pentose phosphate pathway, respectively. Respiratory noncompetent cells show greater inhibition of cytosolic menadione-reducing enzymes when NADH rather than NADPH is produced. Spectrophotometric in vitro assays show no difference between the cofactors. Respiratory competent cells show cytosolic inhibition only when NADPH is produced, whereas production of NADH reveals uncoupling at low dicoumarol concentrations and inhibition of complexes III and IV at higher concentrations. Spectrophotometric assays only indicate the presence of cytosolic inhibition regardless of the reduced cofactor used. This article shows the applicability of the amperometric method and emphasizes the significance of determining biological effects of chemicals in living cells.
|
|
| 5. |
- Heiskanen, Arto, et al.
(författare)
-
Monitoring of Saccharomyces cerevisiae Cell Proliferation on Thiol-Modified Planar Gold Microelectrodes Using Impedance Spectroscopy.
- 2008
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 24:16, s. 9066-9073
-
Tidskriftsartikel (refereegranskat)abstract
- An impedance spectroscopic study of the interaction between thiol-modified Au electrodes and Saccharomyces cerevisiae of strain EBY44 revealed that the cells formed an integral part of the interface, modulating the capacitive properties until a complete monolayer was obtained, whereas the charge transfer resistance ( R ct) to the redox process of [Fe(CN)6] (3-/4-) showed a linear relationship to the number of cells even beyond the monolayer coverage. R ct showed strong pH dependence upon increasing the pH of the utilized buffer to 7.2. Upon addition of S. cerevisiae cells at pH 7.2, the obtained value of R ct showed over 560% increase with respect to the value obtained on the same thiol-modified electrode without cells. It was demonstrated that real-time monitoring of S. cerevisiae proliferation, with frequency-normalized imaginary admittance (real capacitance) as the indicator, was possible using a miniaturized culture system, ECIS Cultureware, with integrated planar cysteamine-modified Au microelectrodes. A monolayer coverage was reached after 20-28 h of cultivation, observed as an approximately 15% decrease in the real capacitance of the system.
|
|
| 6. |
- Kostesha, Natalie, et al.
(författare)
-
Real-time detection of cofactor availability in genetically modified living Saccharomyces cerevisiae cells - Simultaneous probing of different geno- and phenotypes.
- 2009
-
Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 76, s. 180-188
-
Tidskriftsartikel (refereegranskat)abstract
- This work describes a mediated amperometric method for simultaneous real-time probing of the NAD(P)H availability in two different phenotypes, fermentative and respiratory, of the phosphoglucose isomerase deletion mutant strain of S. cerevisiae, EBY44 [ENY.WA-1A pgi1-1D::URA3], and its parental strain, ENY.WA-1A. The developed method is based on multichannel detection using microelectrode arrays. Its versatility was demonstrated by using four microelectrode arrays for simultaneously monitoring the NAD(P)H availability of both geno- and phenotypes under the influence of two different carbon sources, glucose and fructose, as well as the cytosolic and mitochondrial inhibitor and uncoupler, dicoumarol. The obtained results indicate that the method is capable of accurately and reproducibly (overall relative standard error of mean 3.2%) mapping the real-time responses of the cells with different genotype-phenotype combinations. The ENY.WA cells showed the same response to glucose and fructose when dicoumarol was used; fermentative cells indicated the presence of cytosolic inhibition and respiratory cells a net effect of mitochondrial uncoupling. EBY44 cells showed cytosolic inhibition with the exception of respiratory cells when fructose was used as carbon source.
|
|
| 7. |
|
|
| 8. |
- Skjolding, Lars Henrik, et al.
(författare)
-
Characterisation of nano-interdigitated electrodes
- 2008
-
Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 100, s. 052045-052045
-
Konferensbidrag (refereegranskat)abstract
- Interdigitated electrodes made up of two individually addressable interdigitated comb-like electrode structures have frequently been suggested as ultra sensitive electrochemical biosensors. Since the signal enhancement effects due to cycling of the reduced and oxidized species are strongly dependent on the inter electrode distances, since the nature of the enhancement is due to overlying diffusion layers, inter digitated electrodes with an electrode separation of less the non emicrometer a redesired for maximum signal amplification. Fabrication of submicron structures can only be made by advanced lithography techniques. By use of electron be amlithography we have fabricated arrays of interdigitated electrodes with an electrode separation distance of 200nm and an electrode finger width of likewise 200nm. The entire electrode structure is 100 micrometre times 100 micrometre, and the active electrode area is dictated by the opening in the passivation layer, that is defined by UV lithography. Here we report measurements of redox cycling of ferrocyanide by coupled cyclic voltammograms, where the potential atone of the working electrodes are varied and either an oxidising or reducing potential is applied to the complimentary interdigitated electrode. The measurements show fast conversion and high collection efficiency round 87% as expected for nano-interdigitated electrodes.
|
|
| 9. |
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
- Spegel, Christer, et al.
(författare)
-
Chip Based Electroanalytical Systems for Cell Analysis
- 2008
-
Ingår i: Electroanalysis. - : Wiley. - 1040-0397 .- 1521-4109. ; 20:6, s. 680-702
-
Forskningsöversikt (refereegranskat)abstract
- This review with 239 references has as its aim to give the reader an introduction to the kinds of methods used for developing microchip based electrode systems as well as to cover the existing literature on electroanalytical systems where microchips play a crucial role for “none-destructive” measurements of processes related to living cells, i.e., systems without lysing the cells. The focus is on chip based amperometric and impedimetric cell analysis systems where measurements utilizing solely carbon fibre microelectrodes (CFME) and other non-chip electrode formats, such as CFME for exocytosis studies and scanning electrochemical microscopy (SECM) studies of living cells have been omitted. Included is also a discussion about some future and emerging nano tools and considerations that might have an impact on the future of “non-destructive” chip based electroanalysis of living cells.
|
|
| 13. |
- Spegel, Christer
(författare)
-
Electrochemical monitoring of living cells
- 2007
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents the utilization of electroanalytical methods for analysis of dynamic cellular processes such as exocytosis, intracellular redox reactions and cell surface interactions. Microchips have been designed and manufactured with the purpose of monitoring dopamine exocytosis from single or a small ensemble of PC12 cells. The electrode surface was modified with self assembled monolayers of thiols in order to improve the electrochemical detection of dopamine. The first generation microchip relied on manual deposition of cells on top of the electrode whereas the second generation was more advanced and allowed the automatic positioning of cells prior to stimulation and measurements of quantal exocytosis. The metabolic properties of the yeast Saccharomyces cerevisiae have been investigated by monitoring intracellular reduction of the lipophilic mediator menadione. By employing a phosphoglucose isomerase deletion mutant, it was possible to determine the influence of the two major metabolic pathways, i.e. the glycolytic and the pentose phosphate pathway, on intracellular menadione reduction. It was found that cells counteracted the oxidative stress imposed on the cells by the mediators by increasing the rate of NADPH producing reactions. The same strain was utilized for the investigation of enzyme inhibition and mitochondrial uncoupling by the anticoagulant dicoumarol. It was found that dicoumarol mainly affected NADH-dependent processes such as cytosolic mediator reduction and mitochondrial respiration. Electrochemical impedance spectroscopy was used to monitor interactions between yeast and thiol modified gold electrodes. The proliferation of S. cerevisiae could be monitored, up to monolayer coverage, by recording the electrode-solution interface capacitance.
|
|
| 14. |
|
|
| 15. |
- Spegel, Christer, et al.
(författare)
-
Fully automated microchip system for the detection of quantal exocytosis from single and small ensembles of cells
- 2008
-
Ingår i: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0189. ; 2:8, s. 323-329
-
Tidskriftsartikel (refereegranskat)abstract
- A lab-on-a-chip device that enables positioning of single or small ensembles of cells on an aperture in close proximity to a mercaptopropionic acid (MPA) modified sensing electrode has been developed and characterized. The microchip was used for the detection of Ca(2+)-dependent quantal catecholamine exocytosis from single as well as small assemblies of rat pheochromocytoma (PC12) cells. The frequency of events increased considerably upon depolarization of the PC12 cell membrane using a high extracelluar concentration of potassium. The number of recorded events could be correlated with the number of cells immobilized on the electrode. Quantal characteristics, such as the number of released molecules per recorded event, are equivalent to data obtained using conventional carbon fiber microelectrodes. The detection sensitivity of the device allows for the detection of less than 10 000 dopamine molecules in a quantal release. The distribution of peak rise-time and full width at half maximum was constant during measurement periods of several minutes demonstrating the stability of the MPA modified surface.
|
|
| 16. |
- Spegel, Christer, et al.
(författare)
-
On-chip determination of dopamine exocytosis using mercaptopropionic acid modified microelectrodes
- 2007
-
Ingår i: Electroanalysis. - : Wiley. - 1040-0397 .- 1521-4109. ; 19:2-3, s. 263-271
-
Tidskriftsartikel (refereegranskat)abstract
- Gold and platinum, which often are used for thin film metallization, are not suitable for the measurement of dopamine (DA), since the oxidation product of DA forms a non-conducting polymer on the electrode surface. In this work several thiols were screened for their ability to prevent this polymerization. It was found that mercaptopropionic acid (MPA) decreased the rate of DA polymerization. MPA, possessing a weak acidic functionality, had the greatest effect on the DA electrochemistry by decreasing electrode passivation, as well as improving reversibility and sensitivity. Modifications of microchip electrodes with MPA did not only improve DA electrochemistry but also significantly increased the storage stability of the transducers. The microchips were ultimately used to detect K+ stimulated quantal release of DA from PC12 cells.
|
|
