High-content single-cell analysis on-chip using a laser microarray scanner

Large-scale investigation of single cell activities and response dynamics in a microarray chip with a microfluidics-fabricated microporous membrane

Microengineering technology involving microfabrication, micropatterning and microfluidics enables promising advances in single cell manipulation and analysis. Herein, we describe a parallel, large-scale, and temporal investigation of diverse single cell activities and response dynamics using a facile-assembled microwell array chip with a microfluidics-molded microporous membrane. We demonstrated that the versatility with respect to geometrical homogeneity and diversity of microporous membrane fabrication, as well as the stability, repeatability, and reproducibility rely on the well-improved molding. Serial and practical operations including controllable single cell trapping, array-like culture or chemical stimulation, and temporal monitoring can be smoothly completed in the chip. We confirmed that the microwell array chip allowed an efficient construction of a single cell array. Using the cell array, on-chip detection of single cell behaviours under various culture and drug therapy conditions to explore phenotypic heterogeneity was achieved in massive and dynamic manners. These achievements provide a facile and reliable methodology for fabricating microporous membranes with precise control and for developing universal microplatforms to perform robust manipulation and versatile analysis of single cells. This work also offers an insight into the development of easy to fabricate/use and market-oriented microsystems for single cell research, pharmaceutical development, and high-throughput screening.

Intracellular near-Infrared Microlaser Probes Based on Organic Microsphere-SiO2 Core-Shell Structures for Cell Tagging and Tracking

Conventional near-infrared (NIR) luminescent probes, such as DsRed and Cy5, utilize spontaneous emission (SE) signals, which are broad (fwhm >50 nm) and often have low quantum yield. Herein, we developed smart NIR intracellular whispering-gallery mode (WGM) microlaser probes made by organic microspheres of (E)-3-(4-(diptolylamino)phenyl)-1-(1-hydroxynaphthalen-2-yl)prop-2-en-1-one (DPHP) coated with a silica shell. The overall small diameter ( D, adjustable between 2 and 10 μm) and the biocompatible silica shell ensure our core-shell microspheres (CSmSPs) to be engulfed in cells as a microlaser operating around 720 nm with a low threshold of 0.78 μJ/cm². Considering that WGM mode spacing depending strongly on its size, it will be possible to distinguish millions of individual macrophages through well-defined WGM lasing peaks (fwhm ≤2 nm) of CSmSPs of different sizes. Furthermore, we monitored the transformation of normal macrophages to foamy ones by encoding them with our NIR CSmSPs microlaser probes, which deliver constant WGM lasing signals with a spectral fluctuation <0.02 nm and excellent stability.

Single-Cell Proteomics for Cancer Immunotherapy

Cancer immunotherapy fights against cancer by modulating the immune response and is delivering encouraging results in clinical treatments. However, it is challenging to achieve durable response in all cancer patients during treatment due to the diversity and dynamic nature of immune system as well as inter- and intratumor heterogeneity. A comprehensive assessment of system immunity and tumor microenvironment is crucial for effective and safe cancer therapy, which can potentially be resolved by single-cell proteomic analysis. Single-cell proteomic technologies enable system-wide profiling of protein levels in a number of single cells within the immune system and tumor microenvironment, and thereby provide direct assessment of the functional state of the immune cells and tumor-immune interaction that could be used to evaluate efficacy of immunotherapy and to improve clinical outcome. In this chapter, we summarized current single-cell proteomic technologies and their applications in cancer immunotherapy.

Microfluidic channel-coupled 3D quartz nanohole arrays for high capture and release efficiency of BT20 cancer cells

Nanostructured materials, such as silicon nanowires, quartz nanostructures, and polymer-modified nanostructures, are a promising new class of materials for the capture and enumeration of very rare tumor cells, including circulating tumor cells (CTCs), to examine their biological characteristics in whole blood of cancer patients. These cells can then be used for transplantation, anti-tumor cell therapy, and cell-secreted protein studies. It is believed that 3-dimensional (3D) nanostructured substrates efficiently enhance cell capture yields due to the increased local contacts between the 3D nanostructures and extracellular extensions of the tumor cells. Recent studies have been performed with enhanced cell capture yields thanks to various nanostructured platforms; however, there remains an urgent need both to capture and release viable rare tumor cells for further molecular (i.e., protein) analysis and to develop patient-specific drugs. Here, we first demonstrate that our 3D quartz nanohole array (QNHA) tumor cell capture and release system allows us not only to selectively capture rare tumor cells, but also to release the cells with high capture and release rates. This system was developed using streptavidin (STR)-functionalized QNHA (STR-QNHA) with a microfluidic channel. Our system has ideal cell-separation yields of as high as 85-91% and high release rates of >90% for the BT20 cell line. We suggest that the use of a microfluidic channel technique coupled with a STR-QNHA cell capture and release chip (STR-QNHA cell chip) would be a powerful and simple process to evaluate the capture, enumeration, and release of CTCs from patient whole blood for studying further cell therapy and tumor-cell-secreted molecules.

Multiplex cell microarrays for high-throughput screening

Microarray technology was developed in the early 1990s to measure the transcription levels of thousands of genes in parallel. The basic premise of high-density arraying has since been expanded to create cell microarrays. Cells on chip are powerful experimental tools for high-throughput and multiplex screening of samples or cellular functions. Miniaturization increases assay throughput while reducing both reagent consumption and cell population heterogeneity effect, making these systems attractive for a wide range of assays, from drug discovery to toxicology, stem cell research and therapy. It is usual to functionalize the surface of a substrate to design cell microarrays. One form of cell microarrays, the transfected cell microarray, wherein plasmid DNA or siRNA spotted on the surface of a substrate is reverse-transfected locally into adherent cells, has become a standard tool for parallel cell-based analysis. With the advent of technology, cells can also be directly spotted onto functionalized surfaces using robotic fluid-dispensing devices or printed directly on bio-ink material. We are providing herein an overview of the latest developments in optical cell microarrays allowing high-throughput and high-content analysis.

A high-content image-based method for quantitatively studying context-dependent cell population dynamics

Tumor progression results from a complex interplay between cellular heterogeneity, treatment response, microenvironment and heterocellular interactions. Existing approaches to characterize this interplay suffer from an inability to distinguish between multiple cell types, often lack environmental context, and are unable to perform multiplex phenotypic profiling of cell populations. Here we present a high-throughput platform for characterizing, with single-cell resolution, the dynamic phenotypic responses (i.e. morphology changes, proliferation, apoptosis) of heterogeneous cell populations both during standard growth and in response to multiple, co-occurring selective pressures. The speed of this platform enables a thorough investigation of the impacts of diverse selective pressures including genetic alterations, therapeutic interventions, heterocellular components and microenvironmental factors. The platform has been applied to both 2D and 3D culture systems and readily distinguishes between (1) cytotoxic versus cytostatic cellular responses; and (2) changes in morphological features over time and in response to perturbation. These important features can directly influence tumor evolution and clinical outcome. Our image-based approach provides a deeper insight into the cellular dynamics and heterogeneity of tumors (or other complex systems), with reduced reagents and time, offering advantages over traditional biological assays.

Interfacing Inorganic Nanowire Arrays and Living Cells for Cellular Function Analysis

Inorganic nanowires are among the most attractive functional materials, which have emerged in the past two decades. They have demonstrated applications in information technology and energy conversion, but their utility in biological or biomedical research remains relatively under-explored. Although nanowire-based sensors have been frequently reported for biomolecular detection, interfacing nanowire arrays and living mammalian cells for the direct analysis of cellular functions is a very recent endeavor. Cell-penetrating nanowires enabled effective delivery of biomolecules, electrical and optical stimulation and recording of intracellular signals over a long period of time. Non-penetrating, high-density nanowire arrays display rich interactions between the nanostructured substrate and the micro/nanoscale features of cell surfaces. Such interactions enable efficient capture of rare cells including circulating tumor cells and trafficking leukocytes from complex biospecimens. It also serves as a platform for probing cell traction force and neuronal guidance. The most recent advances in the field that exploits nanowire arrays (both penetrating and non-penetrating) to perform rapid analysis of cellular functions potentially for disease diagnosis and monitoring are reviewed.

Digital microfluidic immunocytochemistry in single cells

We report a new technique called Digital microfluidic Immunocytochemistry in Single Cells (DISC). DISC automates protocols for cell culture, stimulation and immunocytochemistry, enabling the interrogation of protein phosphorylation on pulsing with stimulus for as little as 3 s. DISC was used to probe the phosphorylation states of platelet-derived growth factor receptor (PDGFR) and the downstream signalling protein, Akt, to evaluate concentration- and time-dependent effects of stimulation. The high time resolution of the technique allowed for surprising new observations-for example, a 10 s pulse stimulus of a low concentration of PDGF is sufficient to cause >30% of adherent fibroblasts to commit to Akt activation. With the ability to quantitatively probe signalling events with high time resolution at the single-cell level, we propose that DISC may be an important new technique for a wide range of applications, especially for screening signalling responses of a heterogeneous cell population.

Nanowire array chips for molecular typing of rare trafficking leukocytes with application to neurodegenerative pathology

Despite the presence of the blood-brain barrier (BBB) that restricts the entry of immune cells and mediators into the central nervous system (CNS), a small number of peripheral leukocytes can traverse the BBB and infiltrate into the CNS. The cerebrospinal fluid (CSF) is one of the major routes through which trafficking leukocytes migrate into the CNS. Therefore, the number of leukocytes and their phenotypic compositions in the CSF may represent important sources to investigate immune-to-brain interactions or diagnose and monitor neurodegenerative diseases. Due to the paucity of trafficking leucocytes in the CSF, a technology capable of efficient isolation, enumeration, and molecular typing of these cells in the clinical settings has not been achieved. In this study, we report on a biofunctionalized silicon nanowire array chip for highly efficient capture and multiplexed phenotyping of rare trafficking leukocytes in small quantities (50 microliters) of clinical CSF specimens collected from neurodegenerative disease patients. The antibody coated 3D nanostructured materials exhibited vastly improved rare cell capture efficiency due to high-affinity binding and enhanced cell-substrate interactions. Moreover, our platform creates multiple cell capture interfaces, each of which can selectively isolate specific leukocyte phenotypes. A comparison with the traditional immunophenotyping using flow cytometry demonstrated that our novel silicon nanowire-based rare cell analysis platform can perform rapid detection and simultaneous molecular characterization of heterogeneous immune cells. Multiplexed molecular typing of rare leukocytes in CSF samples collected from Alzheimer's disease patients revealed the elevation of white blood cell counts and significant alterations in the distribution of major leukocyte phenotypes. Our technology represents a practical tool for potentially diagnosing and monitoring the pathogenesis of neurodegenerative diseases by allowing an effective hematological analysis of the CSF from patients.

Microchip platforms for multiplex single-cell functional proteomics with applications to immunology and cancer research

Single-cell functional proteomics assays can connect genomic information to biological function through quantitative and multiplex protein measurements. Tools for single-cell proteomics have developed rapidly over the past 5 years and are providing approaches for directly elucidating phosphoprotein signaling networks in cancer cells or for capturing high-resolution snapshots of immune system function in patients with various disease conditions. We discuss advances in single-cell proteomics platforms, with an emphasis on microchip methods. These methods can provide a direct correlation of morphological, functional and molecular signatures at the single-cell level. We also provide examples of how those platforms are being applied to both fundamental biology and clinical studies, focusing on immune-system monitoring and phosphoprotein signaling networks in cancer.