A novel 96-well multielectrode array based impedimetric monitoring platform for comparative drug efficacy analysis on 2D and 3D brain tumor cultures

Organoids for Cancer Research: Advances and Challenges

As 3D culture technology advances, new avenues have opened for the development of physiological human cancer models. These preclinical models provide efficient ways to translate basic cancer research into clinical tumor therapies. Recently, cancer organoids have emerged as a model to dissect the more complex tumor microenvironment. Incorporating cancer organoids into preclinical programs have the potential to increase the success rate of oncology drug development and recapitulate the most efficacious treatment regimens for cancer patients. In this review, four main types of cancer organoids are introduced, their applications, advantages, limitations, and prospects are discussed, as well as the recent application of single-cell RNA-sequencing (scRNA-seq) in exploring cancer organoids to advance this field.

Novel Multiparametric Bioelectronic Measurement System for Monitoring Virus-Induced Alterations in Functional Neuronal Networks

Development and optimisation of bioelectronic monitoring techniques like microelectrode array-based field potential measurement and impedance spectroscopy for the functional, label-free and non-invasive monitoring of in vitro neuronal networks is widely investigated in the field of biosensors. Thus, these techniques were individually used to demonstrate the capabilities of, e.g., detecting compound-induced toxicity in neuronal culture models. In contrast, extended application for investigating the effects of central nervous system infecting viruses are rarely described. In this context, we wanted to analyse the effect of herpesviruses on functional neuronal networks. Therefore, we developed a unique hybrid bioelectronic monitoring platform that allows for performing field potential monitoring and impedance spectroscopy on the same microelectrode. In the first step, a neuronal culture model based on primary hippocampal cells from neonatal rats was established with reproducible and stable synchronised electrophysiological network activity after 21 days of cultivation on microelectrode arrays. For a proof of concept, the pseudorabies model virus PrV Kaplan-ΔgG-GFP was applied and the effect on the neuronal networks was monitored by impedance spectroscopy and field potential measurement for 72 h in a multiparametric mode. Analysis of several bioelectronic parameters revealed a virus concentration-dependent degeneration of the neuronal network within 24-48 h, with a significant early change in electrophysiological activity, subsequently leading to a loss of activity and network synchronicity. In conclusion, we successfully developed a microelectrode array-based hybrid bioelectronic measurement platform for quantitative monitoring of pathologic effects of a herpesvirus on electrophysiological active neuronal networks.

One-step construction of multiplexed enzymatic biosensors using light-addressable electrochemistry on a single silicon photoelectrode

The multiplexed detection of metabolites in parallel within a single biosensor plate is sufficiently valuable but also challenging. Herein, we combine the inherent light addressability of silicon with the high selectivity of enzymes, for the construction of multiplexed photoelectrochemical enzymatic biosensors. To conduct a stable electrochemistry and reagentless biosensing on silicon, a new strategy involving the immobilization of both redox mediators and enzymes using an amide bond-based hydrogel membrane was proposed. The membrane characterization results demonstrated a covalent coupling of ferrocene mediator to hydrogel, in which the mediator acted as not only a signal generator but also a renewable sacrifice agent. By adding corresponding enzymes on different spots of hydrogel membrane modified silicon and recording local photocurrents with a moveable light pointer, this biosensor setup was used successfully to detect multiple metabolites, such as lactate, glucose, and sarcosine, with good analytical performances. The limits of detection of glucose, sarcosine and lactate were found to be 179 μM, 16 μM, and 780 μM with the linear ranges of 0.5-2.5 mM, 0.3-1.5 mM, and 1.0-3.0 mM, respectively. We believe this proof-of-concept study provides a simple and rapid one-step immobilization approach for the fabrication of reagentless enzymatic assays with silicon-based light-addressable electrochemistry.

Microcavity well-plate for automated parallel bioelectronic analysis of 3D cell cultures

Three-dimensional (3D) in vitro cell culture models serve as valuable tools for accurately replicating cellular microenvironments found in vivo. While cell culture technologies are rapidly advancing, the availability of non-invasive, real-time, and label-free analysis methods for 3D cultures remains limited. To meet the demand for higher-throughput drug screening, there is a demanding need for analytical methods that can operate in parallel. Microelectrode systems in combination with microcavity arrays (MCAs), offer the capability of spatially resolved electrochemical impedance analysis and field potential monitoring of 3D cultures. However, the fabrication and handling of small-scale MCAs have been labour-intensive, limiting their broader application. To overcome this challenge, we have established a process for creating MCAs in a standard 96-well plate format using high-precision selective laser etching. In addition, to automate and ensure the accurate placement of 3D cultures on the MCA, we have designed and characterized a plug-in tool using SLA-3D-printing. To characterize our new 96-well plate MCA-based platform, we conducted parallel analyses of human melanoma 3D cultures and monitored the effect of cisplatin in real-time by impedance spectroscopy. In the following we demonstrate the capabilities of the MCA approach by analysing contraction rates of human pluripotent stem cell-derived cardiomyocyte aggregates in response to cardioactive compounds. In summary, our MCA system significantly expands the possibilities for label-free analysis of 3D cell and tissue cultures, offering an order of magnitude higher parallelization capacity than previous devices. This advancement greatly enhances its applicability in real-world settings, such as drug development or clinical diagnostics.

Mind In Vitro Platforms: Versatile, Scalable, Robust, and Open Solutions to Interfacing with Living Neurons

Motivated by the unexplored potential of in vitro neural systems for computing and by the corresponding need of versatile, scalable interfaces for multimodal interaction, an accurate, modular, fully customizable, and portable recording/stimulation solution that can be easily fabricated, robustly operated, and broadly disseminated is presented. This approach entails a reconfigurable platform that works across multiple industry standards and that enables a complete signal chain, from neural substrates sampled through micro-electrode arrays (MEAs) to data acquisition, downstream analysis, and cloud storage. Built-in modularity supports the seamless integration of electrical/optical stimulation and fluidic interfaces. Custom MEA fabrication leverages maskless photolithography, favoring the rapid prototyping of a variety of configurations, spatial topologies, and constitutive materials. Through a dedicated analysis and management software suite, the utility and robustness of this system are demonstrated across neural cultures and applications, including embryonic stem cell-derived and primary neurons, organotypic brain slices, 3D engineered tissue mimics, concurrent calcium imaging, and long-term recording. Overall, this technology, termed "mind in vitro" to underscore the computing inspiration, provides an end-to-end solution that can be widely deployed due to its affordable (>10× cost reduction) and open-source nature, catering to the expanding needs of both conventional and unconventional electrophysiology.

A review of electrochemical impedance as a tool for examining cell biology and subcellular mechanisms: merits, limits, and future prospects

Herein the development of cellular impedance biosensors, electrochemical impedance spectroscopy, and the general principles and terms associated with the cell-electrode interface is reviewed. This family of techniques provides quantitative and sensitive information into cell responses to stimuli in real-time with high temporal resolution. The applications of cell-based impedance biosensors as a readout in cell biology is illustrated with a diverse range of examples. The current state of the field, its limitations, the possible available solutions, and the potential benefits of developing biosensors are discussed.

Preclinical Efficacy and Toxicology Evaluation of RAC1 Inhibitor 1A-116 in Human Glioblastoma Models

Simple Summary

Malignant gliomas are the most common primary central nervous system tumors in adults. Currently, this disease is associated with poor prognosis and is virtually incurable. There is a need to find novel targets and treatments to improve patient survival. This study shows the preclinical evaluation of 1A-116, a Rac1 inhibitor that showed in vitro antitumor activity on glioma cells. We also evaluated 1A-116 in vivo, showing a favorable toxicological profile and antitumor efficacy in an intracranial mouse tumor model. Altogether, our study provides important evidence of 1A-116 as a signal transduction-based precision therapy for glioma and also increases the evidence of Rac1 as a key molecular target in cancer.

Abstract

Malignant gliomas are the most common primary central nervous system tumor in adults. Despite current therapeutics, these tumors are associated with poor prognosis and a median survival of 16 to 19 months. This highlights the need for innovative treatments for this incurable disease. Rac1 has long been associated with tumor progression and plays a key role in glioma’s infiltrative and invasive nature. The aim of this study is to evaluate the 1A-116 molecule, a Rac1 inhibitor, as targeted therapy for this aggressive disease. We found that targeting Rac1 inhibits cell proliferation and cell cycle progression using different in vitro human glioblastoma models. Additionally, we evaluated 1A-116 in vivo, showing a favorable toxicological profile. Using in silico tools, 1A-116 is also predicted to penetrate the blood–brain barrier and present a favorable metabolic fate. In line with these results, 1A-116 i.p daily treatment resulted in a dose-dependent antitumor effect in an orthotopic IDH-wt glioma model. Altogether, our study provides a strong potential for clinical translation of 1A-116 as a signal transduction-based precision therapy for glioma and also increases the evidence of Rac1 as a key molecular target.

Review on the Vascularization of Organoids and Organoids-on-a-hip

The use of human cells for the construction of 3D organ models in vitro based on cell self-assembly and engineering design has recently increased in popularity in the field of biological science. Although the organoids are able to simulate the structures and functions of organs in vitro, the 3D models have difficulty in forming a complex vascular network that can recreate the interaction between tissue and vascular systems. Therefore, organoids are unable to survive, due to the lack of oxygen and nutrients, as well as the accumulation of metabolic waste. Organoids-on-a-chip provides a more controllable and favorable design platform for co-culture of different cells and tissue types in organoid systems, overcoming some of the limitations present in organoid culture. However, the majority of them has vascular networks that are not adequately elaborate to simulate signal communications between bionic microenvironment (e.g., fluid shear force) and multiple organs. Here, we will review the technological progress of the vascularization in organoids and organoids-on-a-chip and the development of intravital 3D and 4D bioprinting as a new way for vascularization, which can aid in further study on tissue or organ development, disease research and regenerative medicine.

Compact 256-channel multi-well microelectrode array system for in vitro neuropharmacology test

Microelectrode arrays (MEAs) have been extensively used to measure extracellular spike activity from cultured neurons using multiple electrodes embedded in a planar glass substrate. This system has been implemented to investigate drug effects by detecting pharmacological perturbation reflected in spontaneous network activity. By configuring multiple wells in an MEA, a high-throughput electrophysiological assay has become available, speeding up drug tests. Despite its merits in acquiring massive amounts of electrophysiological data, the high cost and the bulky size of commercial multi-well MEA systems and most importantly its lack of customizability prevent potential users from fully implementing the system in drug experiments. In this work, we have developed a microelectrode array based drug testing platform by incorporating a custom-made compact 256-channel multi-well MEA in a standard microscope slide and commercial application-specific integrated circuit (ASIC) chip based recording system. We arranged 256 electrodes in 16 wells to maximize data collection from a single chip. The multi-well MEA in this work has a more compact design with reduced chip size compared to previously reported multi-well MEAs. Four synaptic modulators (NMDA, AMPA, bicuculline (BIC) and ATP) were applied to a multi-well MEA and neural spike activity was analyzed to study their neurophysiological effects on cultured neurons. Analyzing various neuropharmacological compounds has become much more accessible by utilizing commercially available digital amplifier chips and customizing a user-preferred analog-front-end interface design with additional benefits in reduced platform size and cost.

PortaDrop: A portable digital microfluidic platform providing versatile opportunities for Lab-On-A-Chip applications

Electrowetting-on-dielectric is a decent technique to manipulate discrete volumes of liquid in form of droplets. In the last decade, electrowetting-on-dielectric systems, also called digital microfluidic systems, became more frequently used for a variety of applications because of their high flexibility and reconfigurability. Thus, one design can be adapted to different assays by only reprogramming. However, this flexibility can only be useful if the entire system is portable and easy to use. This paper presents the development of a portable, stand-alone digital microfluidic system based on a Linux-based operating system running on a Raspberry Pi, which is unique. We present "PortaDrop" exhibiting the following key features: (1) an "all-in-one box" approach, (2) a user-friendly, self-explaining graphical user interface and easy handling, (3) the ability of integrated electrochemical measurements, (4) the ease to implement additional lab equipment via Universal Serial Bus and the General Purpose Interface Bus as well as (5) a standardized experiment documentation. We propose that PortaDrop can be used to carry out experiments in different applications, where small sample volumes in the nanoliter to picoliter range need to be handled an analyzed automatically. As a first application, we present a protocol, where a droplet is consequently exchanged by droplets of another medium using passive dispensing. The exchange is monitored by electrical impedance spectroscopy. It is the first time, the media exchange caused by passive dispensing is characterized by electrochemical impedance spectroscopy. Summarizing, PortaDrop allows easy combination of fluid handling by means of electrowetting and additional sensing.

Parallelized Wireless Sensing System for Continuous Monitoring of Microtissue Spheroids

Currently, the use of electrical readout methods for the investigation of microtissue spheroids in combination with lab automation tools is hindered by the cable connections that are required to interrogate the on-chip-integrated electrodes. To overcome this limitation, we developed a wireless sensor scheme, which can detect the size variation of microtissues during long-term culturing and drug exposure assays. The sensor system includes an interrogation board, which is composed of an inductor-capacitor (LC) readout circuit, and the tissue culture platform with integrated split-ring sensors. The magnetic coupling between the LC circuit and the sensors enables the interrogation of the on-chip sensors without any wire connection to the culture platform. By optimizing the sensor dimensions and the LC resonance frequencies, we were able to avoid cross talk between neighboring sensors. We integrated 12 tissue compartments on a standard microscopy slide with a sensor-to-sensor pitch of 9 mm, which is in accordance with standard 96-well plate dimensions. As a proof-of-concept experiment for the developed system, we monitored continuously and during more than four days the growth inhibition of colon cancer microtissue spheroids that had been exposed to different concentrations of doxorubicin, a chemotherapeutic compound. The stability of the measurements during long-term culturing and the compatibility of the sensor scheme with standard lab equipment offer great potential for automated electrical microtissue spheroid characterization.

Recent Advances in Monitoring Cell Behavior Using Cell-Based Impedance Spectroscopy

Cell-based impedance spectroscopy (CBI) is a powerful tool that uses the principles of electrochemical impedance spectroscopy (EIS) by measuring changes in electrical impedance relative to a voltage applied to a cell layer. CBI provides a promising platform for the detection of several properties of cells including the adhesion, motility, proliferation, viability and metabolism of a cell culture. This review gives a brief overview of the theory, instrumentation, and detection principles of CBI. The recent applications of the technique are given in detail for research into cancer, neurodegenerative diseases, toxicology as well as its application to 2D and 3D in vitro cell cultures. CBI has been established as a biophysical marker to provide quantitative cellular information, which can readily be adapted for single-cell analysis to complement the existing biomarkers for clinical research on disease progression.

Comparison of Drug Inhibitory Effects ([Formula: see text]) in Monolayer and Spheroid Cultures

Traditionally, the monolayer (two-dimensional) cell cultures are used for initial evaluation of the effectiveness of anticancer drugs. In particular, these experiments provide the [Formula: see text] curves that determine drug concentration that can inhibit growth of a tumor colony by half when compared to the cells grown with no exposure to the drug. Low [Formula: see text] value means that the drug is effective at low concentrations, and thus will show lower systemic toxicity when administered to the patient. However, in these experiments cells are grown in a monolayer, all well exposed to the drug, while in vivo tumors expand as three-dimensional multicellular masses, where inner cells have a limited access to the drug. Therefore, we performed computational studies to compare the [Formula: see text] curves for cells grown as a two-dimensional monolayer and a cross section through a three-dimensional spheroid. Our results identified conditions (drug diffusivity, drug action mechanisms and cell proliferation capabilities) under which these [Formula: see text] curves differ significantly. This will help experimentalists to better determine drug dosage for future in vivo experiments and clinical trials.

Understanding the effect of measurement time on drug characterization

In order to determine correct dosage of chemotherapy drugs, the effect of the drug must be properly quantified. There are two important values that characterize the effect of the drug: εmax is the maximum possible effect of a drug, and IC50 is the drug concentration where the effect diminishes by half. There is currently a problem with the way these values are measured because they are time-dependent measurements. We use mathematical models to determine how the εmax and IC50 values depend on measurement time and model choice. Seven ordinary differential equation models (ODE) are used for the mathematical analysis; the exponential, Mendelsohn, logistic, linear, surface, Bertalanffy, and Gompertz models. We use the models to simulate tumor growth in the presence and absence of treatment with a known IC50 and εmax. Using traditional methods, we then calculate the IC50 and εmax values over fifty days to show the time-dependence of these values for all seven mathematical models. The general trend found is that the measured IC50 value decreases and the measured εmax increases with increasing measurement day for most mathematical models. Unfortunately, the measured values of IC50 and εmax rarely matched the values used to generate the data. Our results show that there is no optimal measurement time since models predict that IC50 estimates become more accurate at later measurement times while εmax is more accurate at early measurement times.

Transparent Microelectrode Arrays Fabricated by Ion Beam Assisted Deposition for Neuronal Cell in Vitro Recordings

Microelectrode array (MEA) is a tool used for recording bioelectric signals from electrically active cells in vitro. In this paper, ion beam assisted electron beam deposition (IBAD) has been used for depositing indium tin oxide (ITO) and titanium nitride (TiN) thin films which are applied as transparent track and electrode materials in MEAs. In the first version, both tracks and electrodes were made of ITO to guarantee full transparency and thus optimal imaging capability. In the second version, very thin (20 nm) ITO electrodes were coated with a thin (40 nm) TiN layer to decrease the impedance of Ø30 µm electrodes to one third (1200 kΩ 320 kΩ) while maintaining (partial) transparency. The third version was also composed of transparent ITO tracks, but the measurement properties were optimized by using thick (200 nm) opaque TiN electrodes. In addition to the impedance, the optical transmission and electric noise levels of all three versions were characterized and the functionality of the MEAs was successfully demonstrated using human pluripotent stem cell-derived neuronal cells. To understand more thoroughly the factors contributing to the impedance, MEAs with higher IBAD ITO thickness as well as commercial sputter-deposited and highly conductive ITO were fabricated for comparison. Even if the sheet-resistance of our IBAD ITO thin films is very high compared to the sputtered one, the impedances of the MEAs of each ITO grade were found to be practically equal (e.g., 300-370 kΩ for Ø30 µm electrodes with 40 nm TiN coating). This implies that the increased resistance of the tracks, either caused by lower thickness or lower conductivity, has hardly any contribution to the impedance of the MEA electrodes. The impedance is almost completely defined by the double-layer interface between the electrode top layer and the medium including cells.

Label-Free Bioelectrochemical Methods for Evaluation of Anticancer Drug Effects at a Molecular Level

Cancer is a multifactorial family of diseases that is still a leading cause of death worldwide. More than 100 different types of cancer affecting over 60 human organs are known. Chemotherapy plays a central role for treating cancer. The development of new anticancer drugs or new uses for existing drugs is an exciting and increasing research area. This is particularly important since drug resistance and side effects can limit the efficacy of the chemotherapy. Thus, there is a need for multiplexed, cost-effective, rapid, and novel screening methods that can help to elucidate the mechanism of the action of anticancer drugs and the identification of novel drug candidates. This review focuses on different label-free bioelectrochemical approaches, in particular, impedance-based methods, the solid supported membranes technique, and the DNA-based electrochemical sensor, that can be used to evaluate the effects of anticancer drugs on nucleic acids, membrane transporters, and living cells. Some relevant examples of anticancer drug interactions are presented which demonstrate the usefulness of such methods for the characterization of the mechanism of action of anticancer drugs that are targeted against various biomolecules.

Impedance Spectroscopy as a Tool for Monitoring Performance in 3D Models of Epithelial Tissues

In contrast to traditional 2D cell cultures, both 3D models and organ-on-a-chip devices allow the study of the physiological responses of human cells. These models reconstruct human tissues in conditions closely resembling the body. Translation of these techniques into practice is hindered by associated labor costs, a need which may be remedied by automation. Impedance spectroscopy (IS) is a promising, automation-compatible label-free technology allowing to carry out a wide range of measurements both in real-time and as endpoints. IS has been applied to both the barrier cultures and the 3D constructs. Here we provide an overview of the impedance-based analysis in different setups and discuss its utility for organ-on-a-chip devices. Most attractive features of impedance-based assays are their compatibility with high-throughput format and supports for the measurements in real time with high temporal resolution, which allow tracing of the kinetics. As of now, IS-based techniques are not free of limitations, including imperfect understanding of the parameters that have their effects on the impedance, especially in 3D cell models, and relatively high cost of the consumables. Moreover, as the theory of IS stems from electromagnetic theory and is quite complex, work on popularization and explanation of the method for experimental biologists is required. It is expected that overcoming these limitations will lead to eventual establishing IS based systems as a standard for automated management of cell-based experiments in both academic and industry environments.

Preclinical models for neuroblastoma: Advances and challenges

Neuroblastoma is a paediatric cancer of the sympathetic nervous system and the most common solid tumour of infancy, contributing to 15% of paediatric oncology deaths. Current therapies are not effective in the long-term treatment of almost 80% of patients with this clinically aggressive disease. The primary challenge in the identification and validation of new agents for paediatric drug development is the accurate representation of tumour biology and diversity. In addition to this limitation, the low incidence of neuroblastoma makes the recruitment of eligible patients for early phase clinical trials highly challenging and highlights the need for robust preclinical testing to ensure that the best treatments are selected. The research field requires new preclinical models, technologies, and concepts to tackle these problems. Tissue engineering offers attractive tools to assist in the development of three-dimensional (3D) cell models using various biomaterials and manufacturing approaches that recreate the geometry, mechanics, heterogeneity, metabolic gradients, and cell communication of the native tumour microenvironment. In this review, we discuss current experimental models and assess their abilities to reflect the structural organisation and physiological conditions of the human body, in addition to current and new techniques to recapitulate the tumour niche using tissue-engineered platforms. Finally, we will discuss the possible use of novel 3D in vitro culture systems to address open questions in neuroblastoma biology.

Spheroid-3D and Monolayer-2D Intestinal Electrochemical Biosensor for Toxicity/Viability Testing: Applications in Drug Screening, Food Safety, and Environmental Pollutant Analysis

The rise of three-dimensional cell culture systems that provide in vivo-like environments for pharmaco-toxicological models has prompted the need for simple and robust viability assays suitable for complex cell architectural structures. This study addresses that challenge with the development of an in vitro enzyme based electrochemical sensor for viability/cytotoxicity assessment of two-dimensional (2D) monolayer and three-dimensional (3D) spheroid culture formats. The biosensor measures the cell viability/toxicity via electrochemical monitoring of the enzymatic activity of nonspecific esterases of viable cells, through the hydrolysis of 1-naphthyl acetate to 1-naphthol. The proposed sensor demonstrated strong correlation ( r = 0.979) with viable cell numbers. Furthermore, the model intestinal toxicants diclofenac (DFC, pharmaceutical), okadaic acid (OA, food-safety), and mancozeb (MZB, environmental) were used for the functional evaluation of the proposed sensor using 2D and 3D culture formats. Sensor performance showed high consistency with conventional cell viability/cytotoxicity assays (MTT/CFDA-AM) for all toxicants, with the sensor IC₅₀ values matching the relevant viability LC₅₀ values at the 95% confidence interval range for 2D (DCF: 1.19-1.26 mM, MZB: 10.28-14.18 μM, OA: 40.91-77.13 nM) and 3D culture formats (DCF: 1.02-4.78 mM, MZB: 11.26-15.16 μM, OA: 162.09-179.67 nM). The presented results demonstrate the feasibility of the proposed sensor as a robust endpoint screening tool for both 2D and 3D cytotoxicity assessment.

Monitoring Caco-2 to enterocyte-like cells differentiation by means of electric impedance analysis on printed sensors

BACKGROUND

Colorectal adenocarcinoma cells (Caco-2) are a widely used model of intestinal barrier to study cancer development, toxicological assessments, absorption and metabolism in food science or drug discovery. Caco-2 spontaneously differentiate into a monolayer expressing several specific characteristics, typically showed by mature enterocytes. For in vitro experiments, it is crucial to identify non-invasive and non-destructive techniques able to evaluate the integrity and differentiation of the cells monolayer. Thus, we aimed to assess these properties by analyzing electrical impedance measurements.

METHODS

Caco-2 cells were differentiated for 21 days. The monolayer integrity and differentiation were primarily evaluated by means of morphological, biochemical and molecular data. Impedance measurements in a range of frequencies from 400 Hz to 50 kHz were performed using a dedicated set up, including customized Aerosol Jet Printed carbon-based sensors.

RESULTS

The trends of RI observed at three different frequencies were able to describe cell growth and differentiation. In order to evaluate which frequencies better correlate with cell differentiation, Principal Component Analysis have been employed and the concordance analysis between RI magnitude and morphological, biochemical and molecular data, highlighted 40 kHz as the optimal frequency to assess Caco-2 cells differentiation process.

CONCLUSION

We demonstrated the feasibility and reliability of applying impedance-based measurements not only to provide information about the monolayer status, but also for cell differentiation monitoring.

GENERAL SIGNIFICANCE

This study underlined the possibility to use a dedicated sensor to assess the integrity and differentiation of Caco-2 monolayer, as a reliable non-destructive alternative to conventional approaches.

Induced cross-resistance of BRAFV600E melanoma cells to standard chemotherapeutic dacarbazine after chronic PLX4032 treatment

The maximum response and 10-year survival rate for metastatic melanoma patients treated with standardised chemotherapy is still less than 15% and 10%, respectively. In contrast, oncogene targeting was found a promising tool for killing of BRAF^V600 mutated melanoma cells. Nevertheless, despite improved response and survival rates, resistance acquisition remains an ongoing problem. In this context, the impact of chronic BRAF inhibition on the efficacy of commonly applied cytostatics is still unknown. In our study, human melanoma cells with BRAF^V600E mutation were treated with chemotherapeutics and a BRAF inhibitor. Resistance patterns were analysed by microelectrode array-based impedance spectroscopy, XTT and flow cytometric apoptosis/proliferation assay. BRAF^V600E melanoma cells acquired a time- and concentration-dependent desensitisation up to 100-fold towards oncogene-specific PLX4032 and chemotherapeutic dacarbazine after twelve months treatment. The impact of multiple drug insensitivity on molecular melanoma characteristics was elaborated via mRNA and protein quantification. Following BRAF^V600E targeting, melanoma cells developed an increasingly aggressive, dacarbazine-insensitive phenotype. Thereby, hyperactivated canonical alternative MAPK and bypass PI3K/AKT signalling caused cross-resistance of differently acting drugs. With these results, we are the first to show that long-term melanoma therapy with BRAF inhibitors can prevent further therapeutic success with dacarbazine due to acquisition of cross-resistance.

Micro/nanoelectrochemical probe and chip devices for evaluation of three-dimensional cultured cells

Herein, we present an overview of recent research progress in the development of micro/nanoelectrochemical probe and chip devices for the evaluation of three-dimensional (3D) cultured cells. First, we discuss probe devices: a general outline, evaluation of O₂ consumption, enzyme-modified electrodes, evaluation of endogenous enzyme activity, and the collection of cell components from cell aggregates are discussed. The next section is focused on integrated chip devices: a general outline, electrode array devices, smart electrode array devices, droplet detection of 3D cultured cells, cell manipulation using dielectrophoresis (DEP), and electrodeposited hydrogels used for fabrication of 3D cultured cells on chip devices are discussed. Finally, we provide a summary and discussion of future directions of research in this field.

In vitro field potential monitoring on a multi-microelectrode array for the electrophysiological long-term screening of neural stem cell maturation

Due to the lack of appropriate cell models as well as automated electrophysiology monitoring technologies, the standardized identification of neurotoxic or protective effects in vitro remains a major problem in today's pharmaceutical ingredient development. Over the past few years, in vivo-like human pluripotent stem cell-derived neuronal networks have turned out to be a promising physiological cell source, if the establishment of robust and time-saving functional maturation strategies based on stable and expandable neural progenitor populations can be achieved. Here, we describe a multi-microelectrode array (MMEA)-based bioelectronics platform that was optimized for long-term electrophysiological activity monitoring of neuronal networks via field potential measurements. Differentiation of small molecule-based neuronal progenitors on MMEAs led to functional neurons within 15 days. More strikingly, these functional neuronal cultures could remain electrophysiologically stable on the MMEAs for more than four weeks. The observed electrophysiological properties correlated with the expression of typical neuron subtype markers and were further validated by specific neurotransmitter applications. With our established monitoring platform, we could show for the first time the long-term stability of the neural stem cell-like progenitor population to differentiate to electrophysiologically active dopaminergic neuronal networks for more than 80 passages. In conclusion, we provide a comprehensive long-term stable field potential monitoring platform based on stem cell-derived human neuronal networks that can be automated and up-scaled for standardized high-content screening applications e.g. in the field of neurotoxic and neuroprotective therapeutics identification.

A multidimensional impedance platform for the real-time analysis of single and combination drug pharmacology in patient-derived viable melanoma models

In today's development of anticancer drugs, there is an enormous demand for sensitive, non-invasive real-time screening technologies to identify pharmacodynamics/-kinetics of single and combined drugs with high precision. The combination of sophisticated drug sensitivity testing with advanced in vitro tumor models reflecting heterogeneous tumor behavior in vivo is needed to more reasonably predict therapeutic outcome in vivo. In this study, the benefits of our real-time, non-invasive multidimensional impedance platform over standard in vitro drug sensitivity assays were demonstrated quantitatively using an advanced melanoma model. Detailed pharmacological profiles of clinically established targeted therapeutics in single and combination treatment have been identified in patient tissue and isolated 2D/3D cell line cultures. Impedance spectroscopy revealed significant differences in tissue structure responsible for BRAF inhibitor pharmacokinetics in BRAF^V600E tumor microfragments and cell lines. Remarkably, BRAF-/MEK inhibitor combination treatment of direct patient-derived tissue, but not melanoma cell lines, resulted in short-term antagonistic effects consistent with in vivo findings. In contrast, the clinically validated resistance delay and thus long-term synergy of targeted therapeutics in advanced melanoma models has been demonstrated using impedance technology. The results demonstrate limited clinical transferability of 2D/3D cancer cell line-based chemosensitivity data and underline the importance of in vivo-like direct patient-derived tissue for predictive drug studies. Our non-invasive and highly sensitive multidimensional impedance platform offers great potential for quantifying short- and long-term drug kinetics and synergies to identify the most effective drug combinations in advanced cancer models, thereby improving personalized drug development and treatment planning and ultimately, overall patient outcomes.

The anti-tumorigenic activity of A2M-A lesson from the naked mole-rat

Cancer resistance is a major cause for longevity of the naked mole-rat. Recent liver transcriptome analysis in this animal compared to wild-derived mice revealed higher expression of alpha2-macroglobulin (A2M) and cell adhesion molecules, which contribute to the naked mole-rat’s cancer resistance. Notably, A2M is known to dramatically decrease with age in humans. We hypothesize that this might facilitate tumour development. Here we found that A2M modulates tumour cell adhesion, migration and growth by inhibition of tumour promoting signalling pathways, e.g. PI3K / AKT, SMAD and up-regulated PTEN via down-regulation of miR-21, in vitro and in tumour xenografts. A2M increases the expression of CD29 and CD44 but did not evoke EMT. Transcriptome analysis of A2M-treated tumour cells, xenografts and mouse liver demonstrated a multifaceted regulation of tumour promoting signalling pathways indicating a less tumorigenic environment mediated by A2M. By virtue of these multiple actions the naturally occurring A2M has strong potential as a novel therapeutic agent.

Cell cultures in drug discovery and development: The need of reliable in vitro-in vivo extrapolation for pharmacodynamics and pharmacokinetics assessment

For ethical and cost-related reasons, use of animals for the assessment of mode of action, metabolism and/or toxicity of new drug candidates has been increasingly scrutinized in research and industrial applications. Implementation of the 3 "Rs"¹; rule (Reduction, Replacement, Refinement) through development of in silico or in vitro assays has become an essential element of risk assessment. Physiologically based pharmacokinetic (PBPK²) modeling is the most potent in silico tool used for extrapolation of pharmacokinetic parameters to animal or human models from results obtained in vitro. Although, many types of in vitro assays are conducted during drug development, use of cell cultures is the most reliable one. Two-dimensional (2D) cell cultures have been a part of drug development for many years. Nowadays, their role is decreasing in favor of three-dimensional (3D) cell cultures and co-cultures. 3D cultures exhibit protein expression patterns and intercellular junctions that are closer to in vivo states in comparison to classical monolayer cultures. Co-cultures allow for examinations of the mutual influence of different cell lines. However, the complexity and high costs of co-cultures and 3D equipment exclude such methods from high-throughput screening (HTS).³In vitro absorption, distribution, metabolism, and excretion assessment, as well as drug-drug interaction (DDI), are usually performed with the use of various cell culture based assays. Progress in in silico and in vitro methods can lead to better in vitro-in vivo extrapolation (IVIVE⁴) outcomes and have a potential to contribute towards a significant reduction in the number of laboratory animals needed for drug research. As such, concentrated efforts need to be spent towards the development of an HTS in vitro platform with satisfactory IVIVE features.

Toward modeling the human nervous system in a dish: recent progress and outstanding challenges

Studying the cellular and molecular bases governing development, and normal and abnormal functions of the human CNS is hampered by its complexity and the very limited possibility of experimentally manipulating it in vivo. Development of 3D, tissue-like culture systems offers much promise for boosting our understanding of human neural development, birth defects, neurodegenerative diseases and neural injury, and for providing platforms that will more accurately predict efficacy of putative therapeutic compounds and assess responses to potentially neurotoxic agents. Although novel technological developments and a more interdisciplinary approach to modeling the human CNS are accelerating the pace of discovery, increasing the complexity of in vitro systems increases the ordeals to be overcome to establish highly reproducible models amenable to quantitative analysis.

Quantitative characterization of capsaicin-induced TRPV1 ion channel activation in HEK293 cells by impedance spectroscopy

The analysis of receptor activity, especially in its native cellular environment, has always been of great interest to evaluate its intrinsic but also downstream biological activity. An important group of cellular receptors are ion channels. Since they are involved in a broad range of crucial cell functions, they represent important therapeutic targets. Thus, novel analytical techniques for the quantitative monitoring and screening of biological receptor activity are of great interest. In this context, we developed an impedance spectroscopy-based label-free and non-invasive monitoring system that enabled us to analyze the activation of the transient receptor potential channel Vanilloid 1 (TRPV1) in detail. TRPV1 channel activation by capsaicin resulted in a reproducible impedance decrease. Moreover, concentration response curves with an EC₅₀ value of 0.9 μM could be determined. Control experiments with non TRPV1 channel expressing HEK cells as well as experiments with the TRPV1 channel blocker ruthenium red validated the specificity of the observed impedance decrease. More strikingly, through correlative studies with a cytoskeleton restructuring inhibitor mixture and equivalent circuit analysis of the acquired impedance spectra, we could quantitatively discriminate between the direct TRPV1 channel activation and downstream-induced biological effects. In summary, we developed a quantitative impedimetric monitoring system for the analysis of TRPV1 channel activity as well as downstream-induced biological activity in living cells. It has the capabilities to identify novel ion channel activators as well as inhibitors for the TRPV1 channel but could also easily be applied to other ion channel-based receptors.

A novel 384-multiwell microelectrode array for the impedimetric monitoring of Tau protein induced neurodegenerative processes

Over the last decades, countless bioelectronic monitoring systems were developed for the analysis of cells as well as complex tissues. Most studies addressed the sensitivity and specificity of the bioelectronic detection method in comparison to classical molecular biological assays. In contrast, the up scaling as a prerequisite for the practical application of these novel bioelectronic monitoring systems is mostly only discussed theoretically. In this context, we developed a novel 384-multiwell microelectrode array (MMEA) based measurement system for the sensitive label-free real-time monitoring of neurodegenerative processes by impedance spectroscopy. With respect to the needs of productive screening systems for robust and reproducible measurements on high numbers of plates, we focused on reducing the critical contacting of more than 400 electrodes for a 384-MMEA. Therefore, we introduced an on top array of immersive counter electrodes that are individually addressed by a multiplexer and connected all measurement electrodes on the 384-MMEA to a single contact point. More strikingly, our novel approach provided a comparable signal stability and sensitivity similar to an array with integrated counter electrodes. Next, we optimized a SH-SY5Y cell based tauopathy model by introducing a novel 5-fold Tau mutation eliminating the need of artificial tauopathy induction. In combination with our novel 384-MMEA based measurement system, the concentration and time dependent neuroregenerative effect of the kinase inhibitor SRN-003-556 could be quantitatively monitored. Thus, our novel screening system could be a useful tool to identify and develop potential novel therapeutics in the field of Tau-related neurodegenerative diseases.

3D Tumor Models and Time-Lapse Analysis by Multidimensional Microscopy

The 3D culture is advantageous in reflecting the in vivo condition compared to the 2D culture; however, imaging 3D-cultured cells may be a challenge due to technical restrictions. Recent development of confocal spinning disc microscope system as well as sophisticated software has enabled us to monitor dynamism of cell movement in multiple dimensions. Here we describe the method for time-lapse imaging of 3D-cultured cancer cells co-cultured with non-cancerous cells and discuss current limitations and future perspectives.