Cell-Based Microarrays for In Vitro Toxicology

Single-Cell Array Enhanced Cell Damage Recognition Using Artificial Intelligence for Anticancer Drug Discovery

This work developed a cell damage recognition method based on single-cell arrays using an artificial intelligence tool. The method uses micropatterns (single-cell micropatches and microwells) to isolate each cell in an ordered array to minimize cell overlapping and to maintain cell contours. After exposure to a therapeutic drug (e.g., doxorubicin), a large number of single cells are monitored, and the cell damage levels are determined with both morphology and intensity changes in reactive oxygen species recorded under fluorescence microscopy. The convolutional neural network model is trained by the time-series cancer cell images before and after low and high concentrations of drug exposure. The trained model can identify cancer cell status (live/dead) and classify damage levels (major/moderate/minor) with high accuracy. The single-cell pattern allows cells physically segmented at the single-cell level, which not only eliminates the need for computational cell segmentation but also reduces background noise and neighboring interference, which highly enhances the accuracy of analysis via image recognition. The single-cell array accelerates the computational analysis for toxicity with a trained AI model, which can be used to predict cell damage response for screening potential anticancer drugs.

MEL regulates miR-21 and let-7b through the STAT3 cascade in the follicular granulosa cells of Tibetan sheep

Under physiological and pathological conditions, melatonin (MEL) can regulate microRNA (miRNA) expression. However, the mechanisms underlying the regulatory effects of MEL on miRNAs in ovaries are not understood. Firstly, by using fluorescence in situ hybridisation, we found that in ovaries and follicular granulosa cells (FGCs), MT1 co-located with miR-21 and let-7b. Additionally, immunofluorescence revealed that MT1, STAT3, c-MYC and LIN28 proteins co-located. The mRNA and protein levels of STAT3, c-MYC and LIN28 increased under treatment with 10^-7 M MEL. MEL induced an increase in miR-21 and a decrease in let-7b. The LIN28/let-7b and STAT3/miR-21 axes are related to cell differentiation, apoptosis and proliferation. We explored whether the STAT3/c-MYC/LIN28 pathway was involved in miRNA regulation by MEL to explore the putative mechanism of the above relationship. AG490, an inhibitor of the STAT3 pathway, was added before MEL treatment. AG490 inhibited the MEL-induced increases in STAT3, c-MYC, LIN28 and MT1 and changes in miRNA. Through live-cell detection, we discovered that MEL enhanced the proliferation of FGCs. However, the ki67 protein levels decreased when AG490 was added in advance. Furthermore, the dual-luciferase reporter assay verified that STAT3, LIN28 and MT1 were target genes of let-7b. Furthermore, STAT3 and SMAD7 were target genes of miR-21. In addition, the protein levels of the STAT3, c-MYC, LIN28 and MEL receptors decreased when let-7b was overexpressed in FGCs. Overall, MEL might regulate miRNA expression through the STAT3 pathway. In addition, a negative feedback loop between the STAT3 and miR-21 formed; MEL and let-7b antagonized each other in FGCs. These findings may provide a theoretical basis for improving the reproductive performance of Tibetan sheep through MEL and miRNAs.

Quantification of PD-1/PD-L1 Interaction between Membranes from PBMCs and Melanoma Samples Using Cell Membrane Microarray and Time-Resolved Förster Resonance Energy Transfer

Melanoma is a carcinoma known to evade the host immune defenses via the downregulation of the immune response. One of the molecules involved in this mechanism is programmed cell death ligand 1 (PD-L1), which interacts with its receptor, programmed cell death protein 1 (PD-1), expressed on T cells, leading to a reduction in cytokine release and cytotoxic activity, as well as a halt in T-cell proliferation. The approved therapeutic monoclonal antibodies, such as pembrolizumab, target the PD-1/PD-L1 interaction and are revolutionizing cancer treatments. We developed an assay that provides a quantitative readout of PD-1/PD-L1 interactive states between cell membranes of human immune cells (peripheral blood mononuclear cells, PBMCs) and PD-L1-expressing samples. For this purpose, cell membrane microarrays (CMMAs) were developed from membranes isolated from a HT144 cell line and melanoma samples, and PD-L1 expression was quantified using immunofluorescence (IF). CMMAs were incubated with cell membranes of PBMCs expressing PD-1, and the interaction with PD-L1 was quantified by time-resolved Förster resonance energy transfer, in the presence and absence of pembrolizumab as a blocking drug. The developed assay was able to quantify the PD-1/PD-L1 interaction, and this engagement was disrupted in the presence of the blocking antibody. This demonstrates the potential of the method to analyze monoclonal antibody drugs, as well as the functional states of immune checkpoint regulators. Furthermore, our findings provide evidence to support the future implementation of this methodology for both drug discovery and immune system monitoring in cancer, transplantation, and inflammatory and autoimmune diseases.

Advanced Optogenetic-Based Biosensing and Related Biomaterials

The ability to stimulate mammalian cells with light, brought along by optogenetic control, has significantly broadened our understanding of electrically excitable tissues. Backed by advanced (bio)materials, it has recently paved the way towards novel biosensing concepts supporting bio-analytics applications transversal to the main biomedical stream. The advancements concerning enabling biomaterials and related novel biosensing concepts involving optogenetics are reviewed with particular focus on the use of engineered cells for cell-based sensing platforms and the available toolbox (from mere actuators and reporters to novel multifunctional opto-chemogenetic tools) for optogenetic-enabled real-time cellular diagnostics and biosensor development. The key advantages of these modified cell-based biosensors concern both significantly faster (minutes instead of hours) and higher sensitivity detection of low concentrations of bioactive/toxic analytes (below the threshold concentrations in classical cellular sensors) as well as improved standardization as warranted by unified analytic platforms. These novel multimodal functional electro-optical label-free assays are reviewed among the key elements for optogenetic-based biosensing standardization. This focused review is a potential guide for materials researchers interested in biosensing based on light-responsive biomaterials and related analytic tools.

Cellular sensing platform with enhanced sensitivity based on optogenetic modulation of cell homeostasis

We demonstrate a new biosensing concept with impact on the development of rapid, point of need cell based sensing with boosted sensitivity and wide relevance for bioanalysis. It involves optogenetic stimulation of cells stably transfected to express light sensitive protein channels for optical control of membrane potential and of ion homeostasis. Time-lapse impedance measurements are used to reveal cell dynamics changes encompassing cellular responses to bioactive stimuli and optically induced homeostasis disturbances. We prove that light driven perturbations of cell membrane potential induce homeostatic reactions and modulate transduction mechanisms that amplify cellular response to bioactive compounds. This allows cell based biosensors to respond more rapidly and sensitively to low concentrations of bioactive/toxic analytes: statistically relevant impedance changes are recorded in less than 30 min, in comparison with >8 h in the best alternative reported tests for the same low concentration (e.g. a concentration of 25 μM CdCl2, lower than the threshold concentration in classical cellular sensors). Comparative analysis of model bioactive/toxic compounds (ouabain and CdCl2) demonstrates that cellular reactivity can be boosted by light driven perturbations of cellular homeostasis and that this biosensing concept is able to discriminate analytes with different modes of action (i.e. CdCl2 toxicity versus ion pump inhibition by ouabain), a significant advance against state of the art cell based sensors.

Electrochemiluminescent detection of Escherichia coli O157:H7 based on Ru(bpy)3 2+/ZnO nanorod arrays

Foodborne pathogens are perpetual threats to human and animal health. Detection of pathogens requires accurate, sensitive, rapid and point-of-care diagnostic assays. In this study, we described a simple and sensitive electrochemiluminescent (ECL) assay to detect the deadly bacteria Escherichia coli O157:H7 by [Formula: see text]-coated ZnO nanorods arrays (NAs). The [Formula: see text]-coated ZnO NAs were fabricated by immobilizing [Formula: see text] on ZnO NAs with a large specific surface area and good conductivity. An [Formula: see text]-2-(dibutylamino)-ethanol (DBAE) system coated on ZnO NAs exhibits high ECL intensity, rapid response and good stability. This system was further developed as an ECL immunosensor used in the detection of E. coli O157:H7. The proposed ECL immunosensor exhibits a broad detection range within the scope of 200-100 000 CFU ml^-1 and quite a low detection limit of 143 CFU ml^-1. The high specificity, remarkable reproducibility and good stability offer a sensitive, selective, and convenient pathway for detecting E. coli O157:H7 in the field of food safety and clinical diagnosis.

Current status of water environment and their microbial biosensor techniques - Part II: Recent trends in microbial biosensor development

In Part I of the present review series, I presented the current state of the water environment by focusing on Japanese cases and discussed the need to further develop microbial biosensor technologies for the actual water environment. I comprehensively present trends after approximately 2010 in microbial biosensor development for the water environment. In the first section, after briefly summarizing historical studies, recent studies on microbial biosensor principles are introduced. In the second section, recent application studies for the water environment are also introduced. Finally, I conclude the present review series by describing the need to further develop microbial biosensor technologies. Graphical abstract Current water pollution indirectly occurs by anthropogenic eutrophication (Part I). Recent trends in microbial biosensor development for water environment are described in part II of the present review series.

Next-Generation Live-Cell Microarray Technologies

Over the last decades the application of cell-based assays and in vitro cell culture systems has fundamentally transformed our understanding of biological functions on a cellular and organism level. The resulting ubiquitous usage of cell-based assays in today's scientific world has therefore generated a need for advanced in vitro diagnostic systems. This increased demand has further led to the development of miniaturized live-cell microarrays for biomedical applications including high-throughput screening tools and microfluidic systems. The greatest benefit of miniaturized cell analysis systems is the ability to provide quantitative data in real time with high reliability and sensitivity, which are key parameters for any cell-based assay. An additional advantage of live-cell microarrays is their inherent capability for large-scale screening of single cells, multicell populations, as well as spheroids.

Cell Microarray Technologies for High-Throughput Cell-Based Biosensors

Due to the recent demand for high-throughput cellular assays, a lot of efforts have been made on miniaturization of cell-based biosensors by preparing cell microarrays. Various microfabrication technologies have been used to generate cell microarrays, where cells of different phenotypes are immobilized either on a flat substrate (positional array) or on particles (solution or suspension array) to achieve multiplexed and high-throughput cell-based biosensing. After introducing the fabrication methods for preparation of the positional and suspension cell microarrays, this review discusses the applications of the cell microarray including toxicology, drug discovery and detection of toxic agents.

TIRF high-content assay development for the evaluation of drug efficacy of chemotherapeutic agents against EGFR-/HER2-positive breast cancer cell lines

Elevated expression of epidermal growth factor receptor (EGFR) is reported to be associated with poor prognosis in breast cancer. EGFR subtype identification plays a crucial role in deciding the drug combination to treat the cancer patients. Conventional application of immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) produces more discordance results in EGFR subtype identification of cancer specimens. The present study is designed to develop an analytical method for simultaneous identification of cell surface biomarkers and quantitative estimation of drug efficacy in cancer specimens. For this study, we have utilized a total internal reflection fluorescence microscope (TIRFM), Qdot molecular probes and chemotherapeutic agent camptothecin (CPT)-treated breast cancer cell lines namely MCF-7, SK-BR-3 and JIMT-1. Highly sensitive detection signals with low background noise generated from the evanescent field excitation of TIRFM make it a highly suitable tool to detect the cell surface biomarkers in living cells. Moreover, single wavelength excitation of Qdot probes offers multicolour imaging with strong emission brightness. In the present study, TIRF high-content imaging system simultaneously showed the expression pattern of EGFRs and EC50 value for CPT-induced apoptosis and necrosis in MCF-7, SK-BR-3 and JIMT-1 cancer cell lines.