Down scaling of microfluidic cell culture and detection devices for electrochemical monitoring is... more Down scaling of microfluidic cell culture and detection devices for electrochemical monitoring is mostly focused on the miniaturization of the microfluidic chips which are often designed for specific applications and therefore they lack functional flexibility. We present a compact microfluidic cell culture and electrochemical analysis platform with in-built fluid handling and detection, enabling complete cell based assays comprising on-line cleaning, sterilization, surface functionalization, cell seeding, cultivation and electrochemical real-time monitoring of cellular dynamics. To demonstrate the versatility and multifunctionality of the platform, we explored amperometric monitoring of intracellular redox activity in yeast (Saccharomyces cerevisiae) and detection of exocytotically released dopamine from rat pheochromocytoma cells (PC12). Electrochemical impedance spectroscopy was used in both applications for monitoring cell sedimentation and adhesion as well as proliferation in th...
Down scaling of microfluidic cell culture and detection devices for electrochemical monitoring is... more Down scaling of microfluidic cell culture and detection devices for electrochemical monitoring is mostly focused on the miniaturization of the microfluidic chips which are often designed for specific applications and therefore they lack functional flexibility. We present a compact microfluidic cell culture and electrochemical analysis platform with in-built fluid handling and detection, enabling complete cell based assays comprising on-line cleaning, sterilization, surface functionalization, cell seeding, cultivation and electrochemical real-time monitoring of cellular dynamics. To demonstrate the versatility and multifunctionality of the platform, we explored amperometric monitoring of intracellular redox activity in yeast (Saccharomyces cerevisiae) and detection of exocytotically released dopamine from rat pheochromocytoma cells (PC12). Electrochemical impedance spectroscopy was used in both applications for monitoring cell sedimentation and adhesion as well as proliferation in th...
A surface modification of interdigitated gold microelectrodes (IDEs) with a doped polypyrrole (PP... more A surface modification of interdigitated gold microelectrodes (IDEs) with a doped polypyrrole (PPy) film for detection of dopamine released from populations of differentiated PC12 cells is presented. A thin PPy layer was potentiostatically electropolymerized from an aqueous pyrrole solution onto electrode surfaces. The conducting polymer film was doped during electropolymerization by introducing counter-ions in the monomer solution. Several counter-ions were tested and the resulting electrode modifications were characterized electrochemically to find the optimal dopant that increases sensitivity in dopamine detection. Overoxidation of the PPy films was shown to contribute to a significant enhancement in sensitivity to dopamine. The changes caused by overoxidation in the electrochemical behavior and electrode morphology were investigated using cyclic voltammetry and SEM as well as AFM, respectively. The optimal dopant for dopamine detection was found to be polystyrene sulfonate anion (PSS(-)). Rat pheochromocytoma (PC12) cells, a suitable model to study exocytotic dopamine release, were differentiated on IDEs functionalized with an overoxidized PSS(-)-doped PPy film. The modified electrodes were used to amperometrically detect dopamine released by populations of cells upon triggering cellular exocytosis with an elevated K(+) concentration. A comparison between the generated current on bare gold electrodes and gold electrodes modified with overoxidized doped PPy illustrates the clear advantage of the modification, yielding 2.6-fold signal amplification. The results also illustrate how to use cell population based dopamine exocytosis measurements to obtain biologically significant information that can be relevant in, for instance, the study of neural stem cell differentiation into dopaminergic neurons.
2012 IEEE Biomedical Circuits and Systems Conference (BioCAS), 2012
ABSTRACT A novel potentiostat containing 54 current amplifiers matched to an array of custom-fabr... more ABSTRACT A novel potentiostat containing 54 current amplifiers matched to an array of custom-fabricated 5μm microelectrodes for electrochemical imaging of released neurotransmitters is presented. The board is integrated with a programmable microfluidic cell culture system and the whole assembly is thin and compact enough to be placed under the objective of a standard microscope for simultaneous optical and electrochemical monitoring. Each channel, scanned every 54μs, features 3pA current resolution over a 5kHz bandwidth, suitable for detecting single exocytotic events. The design and electrical characterization of the system are reported together with its functionality, certified by a 54-pixel electrochemical imaging of the diffusion of a 10μl droplet of a target analyte inside the cell culture chamber.
Black lipid membranes (BLMs) are significant in studies of membrane transport, incorporated prote... more Black lipid membranes (BLMs) are significant in studies of membrane transport, incorporated proteins/ion transporters, and hence in construction of biosensor devices. Although BLMs provide an accepted mimic of cellular membranes, they are inherently fragile. Techniques are developed to stabilize them, such as hydrogel supports. In this paper, we present a reusable device for studies on hydrogel supported (hs) BLMs. These are formed across an ethylene tetrafluoroethylene (ETFE) aperture array supported by the hydrogel, which is during in situ polymerization covalently "sandwiched" between the ETFE substrate and a gold electrode microchip, thus allowing direct electrochemical studies with the integrated working electrodes. Using electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy and contact angle measurements, we demonstrate the optimized chemical modifications of the gold electrode microchips and plasma modification of the ETFE aperture arrays fa...
Structurally patterned pyrolysed three-dimensional carbon scaffolds (p3D-carbon) are fabricated a... more Structurally patterned pyrolysed three-dimensional carbon scaffolds (p3D-carbon) are fabricated and applied for differentiation of human neural stem cells (hNSCs) developed for cell replacement therapy and sensing of released dopamine. In the absence of differentiation factors (DF) the pyrolysed carbon material induces spontaneous hNSC differentiation into mature dopamine-producing neurons and the 3D-topography promotes neurite elongation. In the presence and absence of DF, ≈73–82% of the hNSCs obtain dopaminergic properties on pyrolysed carbon, a to-date unseen efficiency in both two-dimensional (2D) and 3D environment. Due to conductive properties and 3D environment, the p3D-carbon serves as a neurotransmitter trap, enabling electrochemical detection of a significantly larger dopamine fraction released by the hNSC derived neurons than on conventional 2D electrodes. This is the first study of its kind, presenting new conductive 3D scaffolds that provide highly efficient hNSC differ...
We investigated the combined effect of the initial cell density (12 500, 35 000, 75 000, and 100 ... more We investigated the combined effect of the initial cell density (12 500, 35 000, 75 000, and 100 000 cells cm(-2)) and concentration of the anti-cancer drug doxorubicin on HeLa cells by performing time-dependent cytotoxicity assays using real-time electrochemical impedance spectroscopy. A correlation between the rate of cell death and the initial cell seeding density was found at 2.5 μM doxorubicin concentration, whereas this was not observed at 5 or 100 μM. By sensing the changes in the cell-substrate interaction using impedance spectroscopy under static conditions, the onset of cytotoxicity was observed 5 h earlier than when using a standard colorimetric end-point assay (MTS) which measures changes in the mitochondrial metabolism. Furthermore, with the MTS assay no cytotoxicity was observed after 15 h of incubation with 2.5 μM doxorubicin, whereas the impedance showed at this time point cell viability that was below 25%. These results indicate that impedance detection reveals cyto...
ABSTRACT In this work, we compare pyrolyzed carbon derived from the photoresist SU-8 alone or in ... more ABSTRACT In this work, we compare pyrolyzed carbon derived from the photoresist SU-8 alone or in combination with polystyrene and poly(styrene)-block-poly(dimethylsiloxane) copolymer (PS-b-PDMS), to be used as novel materials for micro- and nanoelectrodes. The pyrolyzed carbon films are evaluated with scanning electron microscopy, thermal gravimetric analysis, X-ray photoelectron spectroscopy, contact angle analysis, and Raman spectroscopy. Furthermore, the standard rate constant for electron transfer is determined from cyclic voltammograms and found to be lower for PS-b-PDMS compared to PS and SU-8 films. This may be related to the lower carbon content of PS-b-PDMS, as well as to its higher microstructural disorder.
Down scaling of microfluidic cell culture and detection devices for electrochemical monitoring is... more Down scaling of microfluidic cell culture and detection devices for electrochemical monitoring is mostly focused on the miniaturization of the microfluidic chips which are often designed for specific applications and therefore they lack functional flexibility. We present a compact microfluidic cell culture and electrochemical analysis platform with in-built fluid handling and detection, enabling complete cell based assays comprising on-line cleaning, sterilization, surface functionalization, cell seeding, cultivation and electrochemical real-time monitoring of cellular dynamics. To demonstrate the versatility and multifunctionality of the platform, we explored amperometric monitoring of intracellular redox activity in yeast (Saccharomyces cerevisiae) and detection of exocytotically released dopamine from rat pheochromocytoma cells (PC12). Electrochemical impedance spectroscopy was used in both applications for monitoring cell sedimentation and adhesion as well as proliferation in th...
Down scaling of microfluidic cell culture and detection devices for electrochemical monitoring is... more Down scaling of microfluidic cell culture and detection devices for electrochemical monitoring is mostly focused on the miniaturization of the microfluidic chips which are often designed for specific applications and therefore they lack functional flexibility. We present a compact microfluidic cell culture and electrochemical analysis platform with in-built fluid handling and detection, enabling complete cell based assays comprising on-line cleaning, sterilization, surface functionalization, cell seeding, cultivation and electrochemical real-time monitoring of cellular dynamics. To demonstrate the versatility and multifunctionality of the platform, we explored amperometric monitoring of intracellular redox activity in yeast (Saccharomyces cerevisiae) and detection of exocytotically released dopamine from rat pheochromocytoma cells (PC12). Electrochemical impedance spectroscopy was used in both applications for monitoring cell sedimentation and adhesion as well as proliferation in th...
A surface modification of interdigitated gold microelectrodes (IDEs) with a doped polypyrrole (PP... more A surface modification of interdigitated gold microelectrodes (IDEs) with a doped polypyrrole (PPy) film for detection of dopamine released from populations of differentiated PC12 cells is presented. A thin PPy layer was potentiostatically electropolymerized from an aqueous pyrrole solution onto electrode surfaces. The conducting polymer film was doped during electropolymerization by introducing counter-ions in the monomer solution. Several counter-ions were tested and the resulting electrode modifications were characterized electrochemically to find the optimal dopant that increases sensitivity in dopamine detection. Overoxidation of the PPy films was shown to contribute to a significant enhancement in sensitivity to dopamine. The changes caused by overoxidation in the electrochemical behavior and electrode morphology were investigated using cyclic voltammetry and SEM as well as AFM, respectively. The optimal dopant for dopamine detection was found to be polystyrene sulfonate anion (PSS(-)). Rat pheochromocytoma (PC12) cells, a suitable model to study exocytotic dopamine release, were differentiated on IDEs functionalized with an overoxidized PSS(-)-doped PPy film. The modified electrodes were used to amperometrically detect dopamine released by populations of cells upon triggering cellular exocytosis with an elevated K(+) concentration. A comparison between the generated current on bare gold electrodes and gold electrodes modified with overoxidized doped PPy illustrates the clear advantage of the modification, yielding 2.6-fold signal amplification. The results also illustrate how to use cell population based dopamine exocytosis measurements to obtain biologically significant information that can be relevant in, for instance, the study of neural stem cell differentiation into dopaminergic neurons.
2012 IEEE Biomedical Circuits and Systems Conference (BioCAS), 2012
ABSTRACT A novel potentiostat containing 54 current amplifiers matched to an array of custom-fabr... more ABSTRACT A novel potentiostat containing 54 current amplifiers matched to an array of custom-fabricated 5μm microelectrodes for electrochemical imaging of released neurotransmitters is presented. The board is integrated with a programmable microfluidic cell culture system and the whole assembly is thin and compact enough to be placed under the objective of a standard microscope for simultaneous optical and electrochemical monitoring. Each channel, scanned every 54μs, features 3pA current resolution over a 5kHz bandwidth, suitable for detecting single exocytotic events. The design and electrical characterization of the system are reported together with its functionality, certified by a 54-pixel electrochemical imaging of the diffusion of a 10μl droplet of a target analyte inside the cell culture chamber.
Black lipid membranes (BLMs) are significant in studies of membrane transport, incorporated prote... more Black lipid membranes (BLMs) are significant in studies of membrane transport, incorporated proteins/ion transporters, and hence in construction of biosensor devices. Although BLMs provide an accepted mimic of cellular membranes, they are inherently fragile. Techniques are developed to stabilize them, such as hydrogel supports. In this paper, we present a reusable device for studies on hydrogel supported (hs) BLMs. These are formed across an ethylene tetrafluoroethylene (ETFE) aperture array supported by the hydrogel, which is during in situ polymerization covalently "sandwiched" between the ETFE substrate and a gold electrode microchip, thus allowing direct electrochemical studies with the integrated working electrodes. Using electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy and contact angle measurements, we demonstrate the optimized chemical modifications of the gold electrode microchips and plasma modification of the ETFE aperture arrays fa...
Structurally patterned pyrolysed three-dimensional carbon scaffolds (p3D-carbon) are fabricated a... more Structurally patterned pyrolysed three-dimensional carbon scaffolds (p3D-carbon) are fabricated and applied for differentiation of human neural stem cells (hNSCs) developed for cell replacement therapy and sensing of released dopamine. In the absence of differentiation factors (DF) the pyrolysed carbon material induces spontaneous hNSC differentiation into mature dopamine-producing neurons and the 3D-topography promotes neurite elongation. In the presence and absence of DF, ≈73–82% of the hNSCs obtain dopaminergic properties on pyrolysed carbon, a to-date unseen efficiency in both two-dimensional (2D) and 3D environment. Due to conductive properties and 3D environment, the p3D-carbon serves as a neurotransmitter trap, enabling electrochemical detection of a significantly larger dopamine fraction released by the hNSC derived neurons than on conventional 2D electrodes. This is the first study of its kind, presenting new conductive 3D scaffolds that provide highly efficient hNSC differ...
We investigated the combined effect of the initial cell density (12 500, 35 000, 75 000, and 100 ... more We investigated the combined effect of the initial cell density (12 500, 35 000, 75 000, and 100 000 cells cm(-2)) and concentration of the anti-cancer drug doxorubicin on HeLa cells by performing time-dependent cytotoxicity assays using real-time electrochemical impedance spectroscopy. A correlation between the rate of cell death and the initial cell seeding density was found at 2.5 μM doxorubicin concentration, whereas this was not observed at 5 or 100 μM. By sensing the changes in the cell-substrate interaction using impedance spectroscopy under static conditions, the onset of cytotoxicity was observed 5 h earlier than when using a standard colorimetric end-point assay (MTS) which measures changes in the mitochondrial metabolism. Furthermore, with the MTS assay no cytotoxicity was observed after 15 h of incubation with 2.5 μM doxorubicin, whereas the impedance showed at this time point cell viability that was below 25%. These results indicate that impedance detection reveals cyto...
ABSTRACT In this work, we compare pyrolyzed carbon derived from the photoresist SU-8 alone or in ... more ABSTRACT In this work, we compare pyrolyzed carbon derived from the photoresist SU-8 alone or in combination with polystyrene and poly(styrene)-block-poly(dimethylsiloxane) copolymer (PS-b-PDMS), to be used as novel materials for micro- and nanoelectrodes. The pyrolyzed carbon films are evaluated with scanning electron microscopy, thermal gravimetric analysis, X-ray photoelectron spectroscopy, contact angle analysis, and Raman spectroscopy. Furthermore, the standard rate constant for electron transfer is determined from cyclic voltammograms and found to be lower for PS-b-PDMS compared to PS and SU-8 films. This may be related to the lower carbon content of PS-b-PDMS, as well as to its higher microstructural disorder.
Uploads
Papers