Biomedical subjects

S Petronis

Publications and source records attributed to S Petronis.

4 recordsLinked to original sources

PubMed2006

A biocompatible micro cell culture chamber (microCCC) for the culturing and on-line monitoring of eukaryote cells.

We have previously shown that a polymeric (PMMA) chip with medium perfusion and integrated heat regulation provides sufficiently precise heat regulation, pH-control and medium exchange to support cell growth for weeks. However, it was unclear how closely the cells cultured in the chip resembled cells cultured in the culture flask. In the current study, gene expression profiles of cells cultured in the chip were compared with gene expression profiles of cells cultured in culture flasks. The results showed that there were only two genes that were differently expressed in cells grown in the cell culture chip compared to cell culture flasks. The cell culture chip could without further modification support cell growth of two other cell lines. Light coming from the microscope lamp during optical recordings of the cells was the only external factor identified, that could have a negative effect on cell survival. Low grade light exposure was however compatible with optical recordings as well as cell viability. These results strongly indicate that a cell culture chip could be constructed that allowed for on-line optical recording of cellular events without affecting the cell culturing condition compared to cell cultured in culture flasks incubated in a dark and CO2 conditioned incubator.

Caco-2 Cells↗

PubMed2005

Locally Addressable Electrochemical Patterning Technique (LAEPT) applied to poly(L-lysine)-graft-poly(ethylene glycol) adlayers on titanium and silicon oxide surfaces.

The protein-resistant polycationic graft polymer, poly(L-lysine)-g-poly(ethylene glycol) (PLL-g-PEG), was uniformly adsorbed onto a homogenous titanium surface and subsequently subjected to a direct current (dc) voltage. Under the influence of an ascending cathodic and anodic potential, there was a steady and gradual loss of PLL-g-PEG from the conductive titanium surface while no desorption was observed on the insulating silicon oxide substrates. We have implemented this difference in the electrochemical response of PLL-g-PEG on conductive titanium and insulating silicon oxide regions as a biosensing platform for the controlled surface functionalization of the titanium areas while maintaining a protein-resistant background on the silicon oxide regions. A silicon-based substrate was micropatterned into alternating stripes of conductive titanium and insulating silicon oxide with subsequent PLL-g-PEG adsorption onto its surfaces. The surface modified substrate was then subjected to +1800 mV (referenced to the silver electrode). It was observed that the potentiostatic action removed the PLL-g-PEG from the titanium stripes without inducing any polyelectrolyte loss from the silicon oxide regions. Time-of-flight secondary ions mass spectroscopy and fluorescence microscopy qualitatively confirmed the PLL-g-PEG retention on the silicon oxide stripes and its absence on the titanium region. This method, known as "Locally Addressable Electrochemical Patterning Technique" (LAEPT), offers great prospects for biomedical and biosensing applications. In an attempt to elucidate the desorption mechanism of PLL-g-PEG in the presence of an electric field on titanium surface, we have conducted electrochemical impedance spectroscopy experiments on bare titanium substrates. The results showed that electrochemical transformations occurred within the titanium oxide layer; its impedance and polarization resistance were found to decrease steadily upon both cathodic and anodic polarization resulting in the polyelectrolyte desorption from the titanium surface.

Biosensing Techniques↗

PubMed2001

Microstructuring ceramic scaffolds for hepatocyte cell culture.

Both extracorporeal liver support devices and tissue engineering of liver for transplantation require the maintenance of functionality of liver cells (hepatocytes) in cell culture for a long time. One approach to achieve this is to optimize hepatocyte in vitro environment by using a scaffold with topographic structure at sub-millimeter scale which controls cell distribution. Therefore, a set of new type of titania ceramic scaffolds, containing cavities of several sizes, has been produced for deducing the best choice of cavity dimensions for culturing hepatocytes. The aim of this paper is to describe in detail the production methods and characterization of such ceramic scaffolds. Experimental production of the scaffolds consists of microfabrication of silicon templates as well as preparation and molding of titania ceramics. The templates, containing arrays of conical protrusions arranged in close-packed hexagonal order, have been achieved using microfabrication methods of photolithography and anisotropic etching in KOH at 50 degrees C. Protrusion dimensions and overall quality of the templates has been evaluated by scanning electron microscopy. The microfabricated templates have resulted in well-defined and reproducible cavities of corresponding dimensions on the titania ceramic surface after injection-molding. Alternatively, simple embossing of the plastified green ceramics with the silicon templates attached to a metal plate also creates cavities on the ceramic surface. While both methods yield good results, they have different advantages: the injection-molding provides a higher quality of imprints while embossing is quicker and less complicated, and is not limited by dimensions of specific molding equipment.

Journal Article↗

PubMed2000

Design and microstructuring of PDMS surfaces for improved marine biofouling resistance.

In this study room temperature vulcanized (RTV) silicone surfaces with designed surface microstructure and well-defined surface chemistry were prepared. Their resistance to marine macrofouling by barnacles Balanus improvisus was tested in field experiments for deducing optimal surface topography dimensions together with a better understanding of macrofouling mechanisms. Polydimethylsiloxane (PDMS) surfaces were microstructured by casting the PDMS pre-polymer on microfabricated molds. The master molds were made by utilizing photolithography and anisotropic etching of monocrystalline silicon wafers. Several iterative casting steps of PDMS and epoxy were used to produce large quantities of microstructured PDMS samples for field studies. The microstructured PDMS surface consisted of arrays of pyramids or riblets creating a surface arithmetic mean roughness ranging from 5 to 17 microm for different microstructure sizes and geometries, as determined by scanning electron microscopy. Chemophysical properties of the microstructured films were investigated by electron spectroscopy for chemical analysis, time-of-flight secondary ion mass spectroscopy and dynamic contact angle measurements. Films were chemically homogeneous down to the submicron level. Hydrophobicity and contact angle hysteresis increased with increased surface roughness. Field tests on the west coast of Sweden revealed that the microstructure containing the largest riblets (profile height 69 microm) reduced the settling of barnacles by 67%, whereas the smallest pyramids had no significant influence on settling compared to smooth PDMS surfaces. The effect of dimensions and geometry of the surface microstructures on the B. improvisus larvae settling is discussed.

Animals↗