Flexible fluidic microchips based on thermoformed and locally modified thin polymer films.

This paper presents a fundamentally new approach for the manufacturing and the possible applications of lab on a chip devices, mainly in the form of disposable fluidic microchips for life sciences applications. The new technology approach is based on a novel microscale thermoforming of thin polymer films as core process. The flexibility not only of the semi-finished but partly also of the finished products in the form of film chips could enable future reel to reel processes in production but also in application. The central so-called 'microthermoforming' process can be surrounded by pairs of associated pre- and postprocesses for micro- and nanopatterned surface and bulk modification or functionalisation of the formed films. This new approach of microscale thermoforming of thin polymer film substrates overlaid with a split local modification of the films is called 'SMART', which stands for 'substrate modification and replication by thermoforming'. In the process, still on the unformed, plane film, the material modifications of the preprocess define the locations where later, then on the spatially formed film, the postprocess generates the final local modifications. So, one can obtain highly resolved modification patterns also on hardly accessible side walls and even behind undercuts. As a first application of the new technology, we present a flexible chip-sized scaffold for three dimensional cell cultivation in the form of a microcontainer array. The spatially warped container walls have been provided with micropores, cell adhesion micropatterns and thin film microelectrodes.

The contribution of neutrophils to reperfusion arrhythmias and a possible role for antiadhesive pharmacological substances.

OBJECTIVES: It is known that neutrophilic leukocytes contribute to cellular damage in the course of cardiac ischemia/reperfusion. A role in arrhythmogenesis, although controversial, has been ascribed in some studies to the leukocytes, but investigations evaluating possible beneficial effects of inhibitors of neutrophil adhesion or transmigration are still missing. METHODS: Isolated spontaneously beating rabbit hearts, perfused with saline solution at constant pressure according to the Langendorff technique, were treated with 15 min infusion of autologous neutrophils. 10 min after the start of this infusion the hearts were submitted to coronary occlusion (LAD) for 30 min followed by 30 min reperfusion. Four experimental groups were investigated: (1) saline-perfused control hearts, (2) leukocyte-perfused hearts, (3) leukocyte-perfused hearts treated with RGDS peptide, (4) leukocyte-perfused hearts treated with chondroitin sulfate C. In all experiments epicardial potential mapping was carried out (256 unipolar leads). At the end of each experiment the hearts were prepared for histology and after staining leukocyte accumulation in the ischemic zone, in the border zone and in the non-ischemic area was evaluated. RESULTS: In leukocyte-perfused hearts submitted to ischemia/reperfusion we found a somewhat enhanced arrhythmogenesis, enhanced ST-segment deviation, and a 2-3-fold increase in leukocyte accumulation in the ischemic and border zone as compared to the non-ischemic tissue as well as increased dispersion of epicardial potential duration especially during reperfusion. These changes and the leukocyte accumulation could be suppressed by treatment with RGDS and to a somewhat lesser extent with chondroitin sulfate C. In addition, arrhythmogenesis could be reduced but not completely suppressed by that treatment. CONCLUSIONS: From these results we conclude that: (a) leukocytes exert an aggravating effect in arrhythmogenesis during ischemia/reperfusion, (b) the arrhythmogenic substrate for this effect may consist of an enhanced dispersion of potential duration and (c) that inhibition of leukocyte accumulation can at least partially reduce arrhythmogenesis and may be of therapeutic interest as an additional treatment.

Intracellular HSP72 detection in HL60 cells using a flow cytometry system based on microfluidic analysis.

HSP72 is an important marker for various environmental stresses and diseases, and many researchers need to detect HSP72 levels in various cells. We have therefore developed an assay to monitor intracellular heat-shock protein 72 expression on a microfluidic Lab-on-a-chip platform. We established this method to detect HSP72 intracellularly by antibody staining with DNA counterstaining. The Lab-on-a-chip technology is simple and efficient when performing flow cytometric assays. By permeabilizing the cells for the delivery of antibodies, we were able to show HSP72 expression after 30 min heat-shock at 44 degrees C and then at various post-incubation times at 37 degrees C. We compared our method to a conventional flow cytometer and an enzyme immunoassay technique.

Acetylsalicylic acid enhances arrhythmogeneity in a model of local ischemia of isolated rabbit hearts.

Acetylsalicylic acid often is used in the treatment and prophylaxis of regional myocardial ischemia and infarction. However, only little is known about its electrophysiological effects and on possible proarrhythmic effects of the drug. Thus, the aim of this study was to evaluate the electrophysiological effects of acetylsalicylic acid in normal isolated saline perfused rabbit hearts and in hearts submitted to regional ischemia. Isolated saline perfused rabbit hearts were treated with increasing concentrations of acetylsalicylic acid (0.05, 0.1, 0.5 and 1 microM). The epicardial activation and repolarisation process were analysed using an epicardial mapping (256 unipolar leads). Activation and repolarisation time were determined for each electrode from which data the 'breakthrough-points' of epicardial activation were determined. At each electrode an activation vector was calculated giving the direction and velocity of the local excitation wave. The similarity of selected heart beats compared to the control was evaluated by determination of the percentage of identical breakthrough-points and of similar vectors (deviation < or = 5 degrees). At each electrode the local epicardial action potential duration was assessed as the activation recovery interval and the standard deviation of the epicardial action potential duration (of 256 leads, = dispersion) was determined. In a second series of experiments 30 min regional ischemia was induced by occlusion of the left descendent coronary artery followed by 30 min reperfusion in the absence or presence of 0.5 microM acetylsalicylic acid or 1 micro/M indomethacin. The degree of ischemia was assessed by the reduction in coronary flow, by the degree of ST-elevation and by the area in which ST-elevation was registered. Under non-ischemic conditions acetylsalicylic acid led to an increase in the epicardial action potential duration (7%), a decrease in the breakthrough-point similarity (by 10%) and vectorfield similarity (by 15%). In control hearts submitted to regional ischemia the similarity of the vectorfields and of the breakthrough-points, as well as the duration of the epicardial action potentials were markedly reduced while the dispersion was greatly increased. In the ischemic region there was a significant ST-deviation from the isoelectrical line. These changes of ST-segments were significantly enhanced by 0.5 microM acetylsalicylic acid, so that in all (7/7) acetylsalicylic acid treated hearts sustained ventricular fibrillation occurred after 20 min ischemia, whereas in the absence of acetylsalicylic acid fibrillation was found in only 2/7 hearts during reperfusion and not during ischemia. 1 microM indomethacin did not cause these changes. In all ischemia/reperfusion series of experiments the reduction in coronary flow and left ventricular pressure by ischemia was of the same degree and we did not observe significant differences in the size of ischemic area. Using 14C-acetylsalicylic acid, an accumulation of acetylsalicylic acid in the ischemic region could be observed. From these results we conclude, that acetylsalicylic acid can induce ventricular fibrillation. Thus, in acute myocardial ischemia, acetylsalicylic acid may have (besides the well known and desired antiaggregatory effects) electrophysiologic side effects which seem to be proarrhythmic in regional ischemia at least in this model.

Enhanced dispersion of epicardial activation-recovery intervals at sites of histological inhomogeneity during regional cardiac ischaemia and reperfusion.

OBJECTIVE: To examine how epicardial activation and repolarisation patterns change in the course of ischaemia, and how these changes are related to the underlying histological structures. METHODS: Langendorff perfused isolated rabbit hearts were submitted to 30 minutes of left anterior descending coronary artery occlusion followed by 30 minutes of reperfusion. A 256 channel epicardial map was plotted during the various experimental phases. Activation time points were determined as t(dU/dtmin) and repolarisation time points as t(dU/dtmax). From these data the local activation-recovery interval (ARI), its dispersion (SD of ARI), and the geometry of the activation spread could be analysed. After the experiments the hearts were processed histologically and the mapping data were projected onto histological slides. RESULTS: There was elevation of the ST segment within the occluded area, which recovered during reperfusion. Within this area, ARI was significantly shortened and its dispersion was maximally enhanced. The enhancement of dispersion was pronounced at sites of histological inhomogeneity like fat, connective tissue, or vessels. There was also a change in the preferential direction of activation spread within the occluded zone with a marked transverse propagation of the activation wave-front, whereas under normal conditions the activation followed the longitudinal fibre axis. In addition, the total activation time in the occluded area was significantly prolonged. CONCLUSIONS: Ischaemia alters the local activation pattern with enhanced dispersion, especially at sites of histological irregularity, transverse shift of the activation waves, and a general slowing of conduction, which may explain the increased susceptibility to arrhythmia in hearts with enhanced histological irregularities--for example, an infarct or in multi-infarcted hearts, or after myocarditis.

Electrocardiological profile and proarrhythmic effects of quinidine, verapamil and their combination: a mapping study.

Quinidine and verapamil are widely used as antiarrhythmic agents and their combination is often used in the treatment of supraventricular tachycardia. This study was undertaken to clarify, whether these drugs exert proarrhythmic effects on the ventricles in therapeutic concentrations and whether possible arrhythmogenic effects might be enhanced by combination. Isolated rabbit hearts perfused according to the Langendorff technique were treated with increasing concentrations of quinidine (0.05 to 3.5 microM) or verapamil (5 to 50 nM) or of their combination (70:1 or 10:1, quinidine:verapamil) corresponding to common low, medium and high free therapeutic concentrations. The epicardial activation process was measured using a computer assisted mapping system for unipolar multichannel recording (256 channels simultaneously). Both substances prolonged the atrioventricular conduction time PQ. This effect was even more pronounced if the 70:1 combination was administered. The activation pattern was altered by both drugs and their combination to the same extent as became obvious from analysis of local activation vectors and of localisation of breakthroughpoints of epicardial activation for heart beats under control conditions and under drug treatment. The epicardial potential durations were prolonged by quinidine and to the same degree by the combinations, but not by verapamil alone. The total activation time was prolonged under the influence of quinidine and if the 70:1 combination was given. Both substances exerted a negative inotropic effect which was enhanced in an additive manner if both drugs were combined. In parallel the coronary flow was diminished.(ABSTRACT TRUNCATED AT 250 WORDS)

Age-related electrophysiological and histological changes in rabbit hearts: age-related changes in electrophysiology.

Because of the known higher incidence of cardiac arrhythmia in aged patients we tried to define the underlying arrhythmogenic substrate by quantifying those electrophysiological alterations in aged rabbit hearts, which are commonly believed to be arrhythmogenic, relating them to histological findings in the same hearts. This is the first investigation that analyses the effect of ageing on the epicardial excitation spreading. Isolated hearts from young (ten weeks) and old (1.5-2 years) white New Zealand rabbits were perfused according to the Langendorff-technique, submitted to epicardial potential mapping for 60 min and investigated histologically. Electrophysiological data in aged hearts showed a) a higher variability of the activation pattern, b) an increased dispersion of the epicardial potential duration; c) a prolongation of the AV-conduction time and of the duration of the epicardial activation signal, which was fractionated in aged hearts. Histological findings showed extensive incorporation of fat cells and connective tissue in ventricular and AV-node tissues, which may explain the prolonged conduction time, and a marked hypertrophy of the ventricular myocytes. The observed high dispersion, the broadened and fractionated epicardial activation signal and the enhanced variability of the activation patterns may be due to the observed long strands of collageneous tissue separating ventricular muscle fibres in aged hearts. These changes help to explain the enhanced susceptibility to arrhythmogenic stimuli with age.

Patterned polymer surfaces for cell culture applications.

We studied the physico/chemical effects of deep UV irradiation of polystyrene, PMMA and polycarbonate with respect to cell adhesion and protein immobilization. Photochemical modifications of the polymer surfaces yielded unstable peroxides and carboxylic acid groups. Patterned enzyme and antibody adsorbates were realized by coupling via carbodiimid activation of the COOH-moities. Hepatoma cells (HepG2) and fibroblasts (L929) adhered in the presence of serum proteins in the culture medium on the irradiated regions of the substrate without any further treatment.

Further development of microstructured culture systems and their use in tissue engineering.

The Forschungszentrum Karlsruhe aims at improving its CellChip. Its main feature is the 1 cm2 core, subdivided into 900 cubic microcontainers (300 x 300 x 300 microns). It is manufactured by injection molding using biodegradable (polylactide) as well as non-degradable (PMMA or PC) polymers. The CellChips will be modified such that membranes will be mounted at the bottom of the CellChip, thus facilitating backend processing. Furthermore, the membranes can be adapted ideally to the assay system of interest by various surface modification techniques.

The three-dimensional cultivation of the carcinoma cell line HepG2 in a perfused chip system leads to a more differentiated phenotype of the cells compared to monolayer culture.

We describe a polymer chip with a grid-like architecture that it is intended for the three-dimensional cultivation of cells with an active nutrient and gas supply. The chip is typically made from polymethyl methacrylate or polycarbonate but can also be manufactured from biodegradable polymers, such as poly(lactic-co-glycolic acid). Different designs of the chip can be realized. In this study, we evaluated a chip with 506 microcontainers of the size of 300 x 300 x 300 microm that are capable of housing up to 6 million cells, and its suitability as a tissue-specific culture system for the carcinoma cell line HepG2 instead of primary liver cells. Related to an earlier study, where we could show the principal suitability of the system for rat primary cells, we here investigated the system's suitability for the human carcinoma cell line HepG2. The carcinoma cells were used in two different types of chip-containing bioreactors. By confocal laser scanning microscopy, we could show that cellular integrity in the chip culture was maintained and that there were no signs of apoptosis as confirmed by the absence of K18 fragmentation. Gene expression analysis of some liver-specific genes revealed a significantly higher expression of the phase II metabolism genes uridine-diphosphate- glucosyl-transferase (UGT1A1) and glutathione-S-transferase (GSTpi1) as a marker. Therefore, we conclude that by using a three-dimensional instead of a conventional monolayer culture system, hepatocellular carcinoma cells display a phenotype that resembles more closely the tissue of origin.

3D tissue culture substrates produced by microthermoforming of pre-processed polymer films.

We describe a new technology based on thermoforming as a microfabrication process. It significantly enhances the tailoring of polymers for three dimensional tissue engineering purposes since for the first time highly resolved surface and bulk modifications prior to a microstructuring process can be realised. In contrast to typical micro moulding techniques, the melting phase is avoided and thus allows the forming of pre-processed polymer films. The polymer is formed in a thermoelastic state without loss of material coherence. Therefore, previously generated modifications can be preserved. To prove the feasibility of our newly developed technique, so called SMART = Substrate Modification And Replication by Thermoforming, polymer films treated by various polymer modification methods, like UV-based patterned films, and films modified by the bombardment with energetic heavy ions, were post-processed by microthermoforming. The preservation of locally applied specific surface and bulk features was demonstrated e.g. by the selective adhesion of cells to patterned microcavity walls.

Semiquantitative reverse transcription-polymerase chain reaction with the Agilent 2100 Bioanalyzer.

We have applied a method to monitor mRNA expression in a semiquantitative fashion on the Agilent 2100 Bioanalyzer. The method was originally described in 1994 by Wong et al. and referred to as the "primer-dropping" method. This polymerase chain reaction (PCR) technique uses multiple sets of primer pairs in a coamplification reaction that amplifies the target of interest within a predetermined range specific for each target. Separation, detection and quantification of PCR products were accomplished using the Agilent 2100 Bioanalyzer in conjunction with the DNA 500 and the DNA 1000 Lab-Chip kits for the detection of DNA fragments with a maximum size of 500 and 1000 bp, respectively. Using primers specific for the inducible form of hsp72 and primers for glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as an internal standard we were able to rapidly monitor and quantify inducible hsp72-mRNA expression.

Influence of oral contraceptive agents on kidney function and protein metabolism.

The present study was an investigation of the effect of oral contraceptives on kidney function as well as a brief examination of protein metabolism, since glomerular filtration rate depends to a large extent on daily protein intake. 28 healthy women not taking contraceptives and 46 healthy women (aged 20-28 y) on one of three different types of oral contraceptive (combination preparations) were investigated [Minulet/Femovan, Marvelon, Diane]. In all groups on oral contraceptives the endogenous creatinine clearance was significantly increased. The potassium excretion rate was significantly elevated in the groups taking Marvelon and Diane, and the sodium excretion rate was significantly increased in those on Minulet/Femovan and Diane. In all groups on contraceptives the albumin excretion rate was numerically but not significantly elevated. No significant differences were found in the daily oral protein intake or the nitrogen excretion rate on comparing the groups taking contraceptives with the control group. However, the ratio nitrogen excretion rate/daily protein intake was significantly increased in those on Minulet/Femovan and Diane. The study has shown that besides their various effects on renal tubular function, oral contraceptives are able to increase the glomerular filtration rate, and certain types have a protein catabolic effect.

[Development of dentition 4 to 6 years of age]. / Beitrag zur Entwicklung des Gebisses im Alter von 4 bis 6 Jahren.

A longitudinal study has been made of the incidence of caries and malocclusion in 361 high-risk children and 180 control children aged between 4 and 6 years. A comparison of the findings obtained from the two groups showed no remarkable differences in the two areas of examination.

[Long-term use of fluoride lacquer in preventive care of school children in area of basic care]. / Langzeiteinsatz von Fluoridlack zur präventiven Betreuung von Schulkindern im Rahmen der Grundbetreuung.

The spread of caries in the city of Rostock was studied from 1979 to 1988 in pupils from classes 1 to 8 where the fluoride varnish application three times a year (Duraphat) was the most important caries prophylaxis measure. All children were included in the evaluation, even those who had entered the school for the first time during the study period and had not had any prior prophylactic treatment. A special study was also made in a single class in the 1st and 6th years, respectively, to compare varnish application by cotton swabs with barrel ampoule injection. A significant reduction in caries was registered in all age groups. The application with barrel ampoule injection proved to be more economical and practical than the cotton swab application. On the whole Duraphat fluoride varnish reasserted its importance in caries prophylaxis and can be regarded as extremely well suited for individual and collective prevention.

[Quality of life of patients with eating disorders. A catamnestic study]. / Lebensqualität essgestörter Patientinnen. Eine Katamneseerhebung.

OBJECTIVE: To assess the eating behaviour, quality of life and changes in life style in 46 female patients with eating disorders, discharged from our psychosomatic unit at least six month ago. METHODS: Patients meeting the criteria for DSM-IV anorexia nervosa or bulimia nervosa completed the "Lancashire Quality of Life Profile" [16] and a questionnaire covering demographic aspects, eating behaviour and changes in life style. RESULTS: Positive changes in eating behaviour correlated with higher quality of life scores in many of the domains assessed, including leisure, financial situation and perceived mental health. These changes also correlated with positive changes in life style in several domains, in particular family situation and leisure activities. CONCLUSIONS: Results show that various connections between eating behaviour and quality of life as well as life style exist, suggesting a treatment concept that emphasizes both clinical symptoms and psycho-social conflicts.

[Results of the treatment of nonlymphoblastic acute leukemia in a pediatric population]. / Resultado del tratamiento de leucemia aguda no linfoblástica en población pediátrica.

On a prospective fashion during approximately two years, 22 pediatric patients with acute non lymphocytic leukemia were evaluated. Of this population the majority had acute mielocytic leukemia, followed by acute myelomonocytic leukemia. Absolutely all patients at the time of diagnosis and subsequently every 4 to 6 weeks had a bone marrow aspiration test. When the patients were first seen, 54% of them presented fever; lymph node enlargement was not a common finding. Only few of this patients presented splenomegaly and/or hepatomegaly. In regards to complete blood counts the most outstanding of its was the presence of leukocyte count above 20000/mm.3 in 8 of this patients. From the 22 patients studied only 21 are evaluable. All 21 patients were treated with a 4 drug combination (modified COAP). Sixteen patients (76%) achieved bone marrow remission, of which only 15 patients (71%) achieved complete remission. The median duration remission was of 9.2 months with a range of 2 to 26 months. At the present time only 7 patients (33%) are alive and on remission. Two more patients are alive but in full relapse. The mortality rate of this study is of 59%. The review of recent chemotherapy reports is presented and the need for further trials is emphasized especially in view of recent papers published in which it appears that better results are being obtained at last in children's acute non lymphocitic leukemia.

A tissue-like culture system using microstructures: influence of extracellular matrix material on cell adhesion and aggregation.

Special microenvironmental conditions are required to induce and/or maintain specific qualities of differentiated cells. An important parameter is the three-dimensional tissue architecture that cannot be reproduced in conventional monolayer systems. Advanced tissue culture systems will meet many of these demands, but may reach their limits, especially when gradients of specific substances over distinct tissue layers must be established for long-term culture. These limitations may be overcome by incorporating microstructures into tissue-like culture systems. The microstructured cell support presented consists of a flat array of 625 cubic microcontainers with porous bottoms, in which cells can be supplied with specific media from both sides of the tissue layer. Permanent cell lines and primary rat hepatocytes have been used to test the culture system. In order to define reproducible conditions for tissue formation and for cell adherence to the structure, several ECM (extracellular matrix) components were tested for coating of microstructured substrata. The described tissue culture system offers great flexibility in adapting the cell support to specific needs.

Microthermoforming as a novel technique for manufacturing scaffolds in tissue engineering (CellChips).

The CellChip is a microstructured polymer scaffold, which favours a three-dimensional cultivation of cells within an array of cubic microcontainers. The manufacturing process used so far is microinjection moulding combined with laser-based perforation. In a first attempt to simplify the process, costly perforation was avoided by using commercially available, inexpensive microfiltration membranes for the bottom of the microcavities. Microthermoforming is a promising novel technique which allows the CellChip to be produced from thin film. Working pressures of approximately 4000 kPa were required for the adequate moulding of 50 microm thick films from three different polymers (polystyrene, polycarbonate, cyclo-olefin polymer). Integrating drafts and chamfers in micromoulds is not going to eliminate an uneven thickness profile, but reduces demoulding forces. Microthermoformed CellChips of polycarbonate were perforated by an ion track technique to guarantee a sufficient supply of medium and gases to the cells. The prestructured CellChips were irradiated with 1460 MeV xenon ions at a fluence of a few 10(6) ions/cm2. The tracks were etched in an aqueous solution of 5 N NaOH at 30 degrees C, which resulted in cylindrical pores approximately 2 microm in diameter. Microinjection-moulded, membrane-bonded and thermoformed CellChips were subjected to comparative examination for viability in a cell culture experiment with parenchymal liver cells (HepG2). The cells stayed viable over a period of more than 20 days. No significant differences in viability between injection-moulded, membrane-bonded, and thermoformed CellChips were observed.