Publications by authors named "Joachim Wiest"

12 Publications

  • Page 1 of 1

Tissue-on-a-Chip: Microphysiometry With Human 3D Models on Transwell Inserts.

Front Bioeng Biotechnol 2020 4;8:760. Epub 2020 Aug 4.

cellasys GmbH, Kronburg, Germany.

Microphysiometry has proved to be a useful tool for monitoring the energy metabolism of living cells and their interactions with other cells. The technique has mainly been used for monitoring two-dimensional (2D) monolayers of cells. Recently, our group showed that it is also possible to monitor the extracellular acidification rate and transepithelial electrical resistance (TEER) of 3D skin constructs in an automated assay maintaining an air-liquid interface (ALI) with a BioChip extended by 3D-printed encapsulation. In this work, we present an optimized multichannel intestine-on-a-chip for monitoring the TEER of the commercially available 3D small intestinal tissue model (EpiIntestinal from MatTek). Experiments are performed for 1 day, during which a 60 min cycle is repeated periodically. Each cycle consists of three parts: (1) maintain ALI; (2) application of the measurement medium or test substance; and (3) the rinse cycle. A cytotoxic and barrier-disrupting benchmark chemical (0.2% sodium dodecyl sulfate) was applied after 8 h of initial equilibration. This caused time-dependent reduction of the TEER, which could not be observed with typical cytotoxicity measurement methods. This work represents a proof-of-principle of multichannel time-resolved TEER monitoring of a 3D intestine model using an automated ALI. Reconstructed human tissue combined with the Intelligent Mobile Lab for Diagnostic technology represents a promising research tool for use in toxicology, cellular metabolism studies, and drug absorption research.
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http://dx.doi.org/10.3389/fbioe.2020.00760DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7417452PMC
August 2020

Proliferation characteristics of cells cultured under periodic versus static conditions.

Cytotechnology 2019 Feb 4;71(1):443-452. Epub 2018 Dec 4.

Cellasys GmbH, Kronburg, Germany.

In vitro culture models have become an indispensable tool for assessing a vast variety of biological questions in many scientific fields. However, common in vitro cultures are maintained under static conditions, which do not reflect the in vivo situation and create a non-physiological environment. To assess whether the growth characteristics of cells cultured at pulsed-perfused versus static conditions differ, we observed the growth of differentially cultured cells in vitro by life-cell time-lapse imaging of recombinant HEK293 cells, stably expressing yellow fluorescent protein. Cells were grown for ~ 30 h at 37 °C and ambient CO concentration in biochips mounted into a custom-designed 3D printed carrier and were imaged at a rate of ten images per hour using a fluorescence microscope with environment control infrastructure. Cells in one chip were maintained under static conditions whereas cells in another chip were recurrently perfused with fresh media. Generated image series were quantitatively analyzed using a custom-modified cell detection software. Imaging data averaged from four biological replicates per culturing condition demonstrate that cells cultured under conventional conditions exhibit an exponential growth rate. In contrast, cells cultured in periodic mode exhibited a non-exponential growth rate. Our data clearly indicate differential growth characteristics of cells cultured under periodic versus static conditions highlighting the impact of the culture conditions on the physiology of cells in vitro.
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http://dx.doi.org/10.1007/s10616-018-0263-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6368509PMC
February 2019

Skin-on-a-Chip: Transepithelial Electrical Resistance and Extracellular Acidification Measurements through an Automated Air-Liquid Interface.

Genes (Basel) 2018 Feb 21;9(2). Epub 2018 Feb 21.

cellasys GmbH, 87758 Kronburg, Germany.

Skin is a critical organ that plays a crucial role in defending the internal organs of the body. For this reason, extensive work has gone into creating artificial models of the epidermis for in vitro skin toxicity tests. These tissue models, called reconstructed human epidermis (RhE), are used by researchers in the pharmaceutical, cosmetic, and environmental arenas to evaluate skin toxicity upon exposure to xenobiotics. Here, we present a label-free solution that leverages the use of the intelligent mobile lab for in vitro diagnostics (IMOLA-IVD), a noninvasive, sensor-based platform, to monitor the transepithelial electrical resistance (TEER) of RhE models and adherent cells cultured on porous membrane inserts. Murine fibroblasts cultured on polycarbonate membranes were first used as a test model to optimize procedures using a custom BioChip encapsulation design, as well as dual fluidic configurations, for continuous and automated perfusion of membrane-bound cultures. Extracellular acidification rate (EAR) and TEER of membrane-bound L929 cells were monitored. The developed protocol was then used to monitor the TEER of MatTek EpiDerm RhE models over a period of 48 hours. TEER and EAR measurements demonstrated that the designed system is capable of maintaining stable cultures on the chip, monitoring metabolic parameters, and revealing tissue breakdown over time.
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http://dx.doi.org/10.3390/genes9020114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5852610PMC
February 2018

A novel lab-on-a-chip platform for spheroid metabolism monitoring.

Cytotechnology 2018 Feb 14;70(1):375-386. Epub 2017 Oct 14.

cellasys GmbH - R&D, Ohmstraße 8, 80802, Munich, Germany.

Sensor-based cellular microphysiometry is a technique that allows non-invasive, label-free, real-time monitoring of living cells that can greatly improve the predictability of toxicology testing by removing the influence of biochemical labels. In this work, the Intelligent Mobile Lab for In Vitro Diagnostics (IMOLA-IVD) was utilized to perform cellular microphysiometry on 3D multicellular spheroids. Using a commercial 3D printer, 3 × 3 microwell arrays were fabricated to maintain nine previously cultured HepG2 spheroids on a single BioChip. Integrated layers above and under the spheroids allowed fluidic contact between spheroids in microwells and BioChip sensors while preventing wash out from medium perfusion. Spheroid culturing protocols were optimized to grow spheroids to a diameter of around 620 μm prior to transfer onto BioChips. An ON/OFF pump cycling protocol was developed to optimize spheroid culture within the designed microwells, intermittently perfuse spheroids with fresh culture medium, and measure the extracellular acidification rate (EAR) and oxygen uptake rate (OUR) with the BioChips of the IMOLA-IVD platform. In a proof-of-concept experiment, spheroids were perfused for 36 h with cell culture medium before being exposed to medium with 1% sodium dodecyl sulphate (SDS) to lyse cells as a positive control. These microphysiometry studies revealed a repeatable pattern of extracellular acidification throughout the experiment, indicating the ability to monitor real-time metabolic activity of spheroids embedded in the newly designed tissue encapsulation. After perfusion for 36 h with medium, SDS exposure resulted in an instant decrease in EAR and OUR signals from 37 mV/h (± 5) to 8 mV/h (± 8) and from 308 mV/h (± 21) to -2 mV/h (± 13), respectively. The presented spheroid monitoring system holds great potential as a method to automate screening and analysis of pharmaceutical agents using 3D multicellular spheroid models.
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http://dx.doi.org/10.1007/s10616-017-0152-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5809666PMC
February 2018

Fetal Bovine Serum (FBS): Past - Present - Future.

ALTEX 2018 9;35(1):99-118. Epub 2017 Aug 9.

Division of Physiology, Medical University Innsbruck, Innsbruck, Austria.

The supplementation of culture medium with fetal bovine serum (FBS, also referred to as "fetal calf serum") is still common practice in cell culture applications. Due to a number of disadvantages in terms of quality and reproducibility of in vitro data, animal welfare concerns, and in light of recent cases of fraudulent marketing, the search for alternatives and the development of serum-free medium formulations has gained global attention. Here, we report on the 3rd Workshop on FBS, Serum Alternatives and Serum-free Media, where regulatory aspects, the serum dilemma, alternatives to FBS, case-studies of serum-free in vitro applications, and the establishment of serum-free databases were discussed. The whole process of obtaining blood from a living calf fetus to using the FBS produced from it for scientific purposes is de facto not yet legally regulated despite the existing EU-Directive 2010/63/EU on the use of animals for scientific purposes. Together with the above-mentioned challenges, several strategies have been developed to reduce or replace FBS in cell culture media in terms of the 3Rs (Refinement, Reduction, Replacement). Most recently, releasates of activated human donor thrombocytes (human platelet lysates) have been shown to be one of the most promising serum alternatives when chemically-defined media are not yet an option. Additionally, new developments in cell-based assay techniques, advanced organ-on-chip and microphysiological systems are covered in this report. Chemically-defined serum-free media are shown to be the ultimate goal for the majority of culture systems, and examples are discussed.
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http://dx.doi.org/10.14573/altex.1705101DOI Listing
August 2018

Automated transepithelial electrical resistance measurements of the EpiDerm reconstructed human epidermis model.

Annu Int Conf IEEE Eng Med Biol Soc 2016 Aug;2016:469-472

Understanding the effect of exogenous substances on human skin is critical for toxicology assessment. To address this, numerous artificial models of the topmost layer of human skin, so-called reconstructed human epidermis (RhE), have been created in an attempt to produce a clear analogue for testing. Unfortunately, current testing modalities still rely on endpoint assays and are not capable of monitoring time-resolved changes in barrier function without using numerous redundant samples. In this work, a novel, time-resolved approach is realized by monitoring the transepithelial electrical resistance (TEER) of MatTek EpiDerm® reconstructed human epidermis model, utilizing an automated protocol with the Intelligent Mobile Lab for in vitro diagnostics (IMOLA-IVD).
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http://dx.doi.org/10.1109/EMBC.2016.7590741DOI Listing
August 2016

Data Processing in Cellular Microphysiometry.

IEEE Trans Biomed Eng 2016 11 23;63(11):2368-2375. Epub 2016 Feb 23.

Goal: This contribution points out the need for well-defined and documented data processing protocols in microphysiometry, an evolving field of label-free cell assays. The sensitivity of the obtained cell metabolic rates toward different routines of raw data processing is evaluated.

Methods: A standard microphysiometric experiment structured in discrete measurement intervals was performed on a platform with a pH- and O -sensor readout. It is evaluated using three different data evaluation protocols, based on A) fast Fourier transformation of such dynamics, B) linear regression (LIN) of pH(t) and O(t) dynamics, and C) numerical simulation (SIM) with a subsequent fitting of dynamics for parameter estimation.

Results: We propose a sequence of well documented steps for an organized processing of raw sensor data. Figures of merit for the quality of raw data and the performance of data processing are provided. To estimate metabolic rates, a reaction-diffusion modeling approach is recommended if the necessary model input parameters such as the distribution of the active biomass, sensor response time, and material properties are available.

Conclusion: The information about cellular metabolic activity contained by measured sensor data dynamics is superimposed by manifold sources of error. Careful consideration of data processing is necessary to eliminate these errors as much as possible and to avoid an incorrect interpretation of data.
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http://dx.doi.org/10.1109/TBME.2016.2533868DOI Listing
November 2016

Biology-inspired microphysiological system approaches to solve the prediction dilemma of substance testing.

ALTEX 2016 15;33(3):272-321. Epub 2016 May 15.

The Institute for Human Organ and Disease Model Technologies, Leiden, The Netherlands.

The recent advent of microphysiological systems - microfluidic biomimetic devices that aspire to emulate the biology of human tissues, organs and circulation in vitro - is envisaged to enable a global paradigm shift in drug development. An extraordinary US governmental initiative and various dedicated research programs in Europe and Asia have led recently to the first cutting-edge achievements of human single-organ and multi-organ engineering based on microphysiological systems. The expectation is that test systems established on this basis would model various disease stages, and predict toxicity, immunogenicity, ADME profiles and treatment efficacy prior to clinical testing. Consequently, this technology could significantly affect the way drug substances are developed in the future. Furthermore, microphysiological system-based assays may revolutionize our current global programs of prioritization of hazard characterization for any new substances to be used, for example, in agriculture, food, ecosystems or cosmetics, thus, replacing laboratory animal models used currently. Thirty-six experts from academia, industry and regulatory bodies present here the results of an intensive workshop (held in June 2015, Berlin, Germany). They review the status quo of microphysiological systems available today against industry needs, and assess the broad variety of approaches with fit-for-purpose potential in the drug development cycle. Feasible technical solutions to reach the next levels of human biology in vitro are proposed. Furthermore, key organ-on-a-chip case studies, as well as various national and international programs are highlighted. Finally, a roadmap into the future is outlined, to allow for more predictive and regulatory-accepted substance testing on a global scale.
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http://dx.doi.org/10.14573/altex.1603161DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5396467PMC
January 2017

Application of algae-biosensor for environmental monitoring.

Annu Int Conf IEEE Eng Med Biol Soc 2015 ;2015:7099-102

Environmental problems including water and air pollution, over fertilization, insufficient wastewater treatment and even ecological disaster are receiving greater attention in the technical and scientific area. In this paper, a method for water quality monitoring using living green algae (Chlorella Kessleri) with the help of the intelligent mobile lab (IMOLA) is presented. This measurement used two IMOLA systems for measurement and reference simultaneously to verify changes due to pollution inside the measurement system. The IMOLA includes light emitting diodes to stimulate photosynthesis of the living algae immobilized on a biochip containing a dissolved oxygen microsensor. A fluid system is used to transport algae culture medium in a stop and go mode; 600s ON, 300s OFF, while the oxygen concentration of the water probe is measured. When the pump stops, the increase in dissolved oxygen concentration due to photosynthesis is detected. In case of a pollutant being transported toward the algae, this can be detected by monitoring the photosynthetic activity. Monitoring pollution is shown by adding emulsion of 0,5mL of Indonesian crude palm oil and 10mL algae medium to the water probe in the biosensor.
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http://dx.doi.org/10.1109/EMBC.2015.7320028DOI Listing
September 2016

Online, label-free monitoring of organ-on-a-chip models: The case for microphysiometry.

Annu Int Conf IEEE Eng Med Biol Soc 2015 ;2015:7091-4

Primarily composed of cells on a porous membrane embedded in microfluidic channels, organ-on-a-Chip (OOC) models are coming into the spotlight as an innovative, new approach to in vitro modeling. However, more work is required to understand the impact OOCs have on cellular function including basal metabolism, barrier resistance and oxygen consumption. Electrochemical sensor-based cellular microphysiometry provides a noninvasive, real-time methodology for monitoring these attribute and can be applied to develop robust, automated assays for organ toxicology, but only few to date have been used with OOCs. In this presentation, we define organ-on-a-chip systems, outline which have been studied with integrated sensors, and present a novel method to study cells cultured directly on a porous membrane.
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http://dx.doi.org/10.1109/EMBC.2015.7320026DOI Listing
September 2016

Model-based analysis on the influence of spatial frequency selection in spatial frequency domain imaging.

Appl Opt 2015 Aug;54(22):6725-31

Frequency variation in spatial frequency domain imaging is a powerful tool for adjusting the penetration depth of the imaging signal and the parameter sensitivity toward absorption and diffusive and subdiffusive scattering. Through our computational analysis, using an analytical solution of the radiative transfer equation, we add quantitation to this tool by linking the different spatial frequency regimes to their relative information content and to their absolute depth sensitivity. Special focus is placed on high spatial frequencies by analysis of the phase function parameter γ and its significance and ambiguity in describing subdiffusive scattering.
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http://dx.doi.org/10.1364/AO.54.006725DOI Listing
August 2015

Cellular signaling: aspects for tumor diagnosis and therapy.

Biomed Tech (Berl) 2007 Feb;52(1):164-8

Heinz-Nixdorf-Lehrstuhl für Medizinische Elektronik, Technische Universität München, München, Germany.

Cells are organic microsystems with functional compartments interconnected by complex signal chains. Intracellular signaling routes and signal reception from the extracellular environment are characterized by redundancy, i.e., parallel pathways exist. If a cell is exposed to an external "signal input", the signal processing elements within the cell provide a response that will be a pattern of reactions manifest as a metabolic, morphologic or electric "signal output". Cell-chip hybrid structures are miniaturized analytical systems with the capability to monitor such cell responses in real time and under continuous control of the environmental conditions. A system analysis approach gives an idea of how the biological component of these hybrid structures works. This is exemplified by the putative role of the microenvironmental pH as a parameter of the utmost importance for the malignant "mode" of tumor cells, which can be monitored and modeled on such hybrid structures.
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http://dx.doi.org/10.1515/BMT.2007.030DOI Listing
February 2007