Capture and stimulated release of circulating tumor cells on polymer-grafted silicon nanostructures

Graphene Oxide Nanosheets Modified with Single-Domain Antibodies for Rapid and Efficient Capture of Cells

Peripheral blood can provide valuable information on an individual's immune status. Cell-based assays typically target leukocytes and their products. Characterization of leukocytes from whole blood requires their separation from the far more numerous red blood cells.1 Current methods to classify leukocytes, such as recovery on antibody-coated beads or fluorescence-activated cell sorting require long sample preparation times and relatively large sample volumes.2 A simple method that enables the characterization of cells from a small peripheral whole blood sample could overcome limitations of current analytical techniques. We describe the development of a simple graphene oxide surface coated with single-domain antibody fragments. This format allows quick and efficient capture of distinct WBC subpopulations from small samples (∼30 μL) of whole blood in a geometry that does not require any specialized equipment such as cell sorters or microfluidic devices.

Thermoresponsive release of viable microfiltrated Circulating Tumor Cells (CTCs) for precision medicine applications

Stimulus responsive release of Circulating Tumor Cells (CTCs), with high recovery rates from their capture platform, is highly desirable for off-chip analyses. Here, we present a temperature responsive polymer coating method to achieve both release as well as culture of viable CTCs captured from patient blood samples.

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.

Capture and Release of Cancer Cells by Combining On-Chip Purification and Off-Chip Enzymatic Treatment

As "liquid biopsies", circulating tumor cells (CTCs) have been thought to hold significant insights for cancer diagnosis and treatment. Despite the advances of microfluidic techniques that improve the capture of CTCs to a certain extent, recovering the captured CTCs with enhanced purity at the same time remains a challenge. Here, by combining on-chip purification and off-chip enzymatic treatment, we demonstrate a two-stage strategy to enhance the purity of captured cancer cells from blood samples. The on-chip purification introduces a stirring flow to increase the capture sensitivity and decrease nonspecifically bounded cells. The off-chip enzymatic treatment enables the cancer cells to be released from the attached magnetic beads, further improving the purity and enabling next reculture. For the proof-of-concept study, spiked cancer cells are successfully obtained from unprocessed whole blood with high recovery rate (∼68%) and purity (∼61%), facilitating subsequent RNA expression analysis.

Rational Design of Materials Interface for Efficient Capture of Circulating Tumor Cells

Originating from primary tumors and penetrating into blood circulation, circulating tumor cells (CTCs) play a vital role in understanding the biology of metastasis and have great potential for early cancer diagnosis, prognosis and personalized therapy. By exploiting the specific biophysical and biochemical properties of CTCs, various material interfaces have been developed for the capture and detection of CTCs from blood. However, due to the extremely low number of CTCs in peripheral blood, there exists a need to improve the efficiency and specificity of the CTC capture and detection. In this regard, a critical review of the numerous reports of advanced platforms for highly efficient and selective capture of CTCs, which have been spurred by recent advances in nanotechnology and microfabrication, is essential. This review gives an overview of unique biophysical and biochemical properties of CTCs, followed by a summary of the key material interfaces recently developed for improved CTC capture and detection, with focus on the use of microfluidics, nanostructured substrates, and miniaturized nuclear magnetic resonance-based systems. Challenges and future perspectives in the design of material interfaces for capture and detection of CTCs in clinical applications are also discussed.

A 3D graphene oxide microchip and a Au-enwrapped silica nanocomposite-based supersandwich cytosensor toward capture and analysis of circulating tumor cells

Determination of the presence and number of circulating tumor cells (CTCs) in peripheral blood can provide clinically important data for prognosis and therapeutic response patterns. In this study, a versatile supersandwich cytosensor was successfully developed for the highly sensitive and selective analysis of CTCs using Au-enwrapped silica nanocomposites (Si/AuNPs) and three-dimensional (3D) microchips. First, 3D microchips were fabricated by a photolithography method. Then, the prepared substrate was applied to bind graphene oxide, streptavidin and biotinylated epithelial-cell adhesion-molecule antibody, resulting in high stability, bioactivity, and capability for CTCs capture. Furthermore, horseradish peroxidase and anti-CA153 were co-linked to the Si/AuNPs for signal amplification. The performance of the cytosensor was evaluated with MCF7 breast cancer cells. Under optimal conditions, the proposed supersandwich cytosensor showed high sensitivity with a wide range of 10(1) to 10(7) cells per mL and a detection limit of 10 cells per mL. More importantly, it could effectively distinguish CTCs from normal cells, which indicated the promising applications of our method for the clinical diagnosis and therapeutic monitoring of cancers.

Development of individualized anti-metastasis strategies by engineering nanomedicines

Metastasis is deadly and also tough to treat as it is much more complicated than the primary tumour. Anti-metastasis approaches available so far are far from being optimal. A variety of nanomedicine formulae provide a plethora of opportunities for developing new strategies and means for tackling metastasis. It should be noted that individualized anti-metastatic nanomedicines are different from common anti-cancer nanomedicines as they specifically target different populations of malignant cells. This review briefly introduces the features of the metastatic cascade, and proposes a series of nanomedicine-based anti-metastasis strategies aiming to block each metastatic step. Moreover, we also concisely introduce the advantages of several promising nanoparticle platforms and their potential for constructing state-of-the-art individualized anti-metastatic nanomedicines.

Capturing Cancer: Emerging Microfluidic Technologies for the Capture and Characterization of Circulating Tumor Cells

Circulating tumor cells (CTCs) escape from primary or metastatic lesions and enter into circulation, carrying significant information of cancer progression and metastasis. Capture of CTCs from the bloodstream and the characterization of these cells hold great significance for the detection, characterization, and monitoring of cancer. Despite the urgent need from clinics, it remains a major challenge to capture and retain these rare cells from human blood with high specificity and yield. Recent exciting advances in micro/nanotechnology, microfluidics, and materials science have enable versatile, robust, and efficient cell isolation and processing through the development of new micro/nanoengineered devices and biomaterials. This review provides a summary of recent progress along this direction, with a focus on emerging methods for CTC capture and processing, and their application in cancer research. Furthermore, classical as well as emerging cellular characterization methods are reviewed to reveal the role of CTCs in cancer progression and metastasis, and hypotheses are proposed in regard to the potential emerging research directions most desired in CTC-related cancer research.

Recent advances in nanotechnology-based detection and separation of circulating tumor cells

Although circulating tumor cells (CTCs) in blood have been widely investigated as a potential biomarker for diagnosis and prognosis of metastatic cancer, their inherent rarity and heterogeneity bring tremendous challenges to develop a CTC detection method with clinically significant specificity and sensitivity. With advances in nanotechnology, a series of new methods that are highly promising have emerged to enable or enhance detection and separation of CTCs from blood. In this review, we systematically categorize nanomaterials, such as gold nanoparticles, magnetic nanoparticles, quantum dots, graphenes/graphene oxides, and dendrimers and stimuli-responsive polymers, used in the newly developed CTC detection methods. This will provide a comprehensive overview of recent advances in the CTC detection achieved through application of nanotechnology as well as the challenges that these existing technologies must overcome to be directly impactful on human health.

Biosensors for Cell Analysis

Biosensors first appeared several decades ago to address the need for monitoring physiological parameters such as oxygen or glucose in biological fluids such as blood. More recently, a new wave of biosensors has emerged in order to provide more nuanced and granular information about the composition and function of living cells. Such biosensors exist at the confluence of technology and medicine and often strive to connect cell phenotype or function to physiological or pathophysiological processes. Our review aims to describe some of the key technological aspects of biosensors being developed for cell analysis. The technological aspects covered in our review include biorecognition elements used for biosensor construction, methods for integrating cells with biosensors, approaches to single-cell analysis, and the use of nanostructured biosensors for cell analysis. Our hope is that the spectrum of possibilities for cell analysis described in this review may pique the interest of biomedical scientists and engineers and may spur new collaborations in the area of using biosensors for cell analysis.

Applications of zero-valent silicon nanostructures in biomedicine

Zero-valent, or elemental, silicon nanostructures exhibit a number of properties that render them attractive for applications in nanomedicine. These materials hold significant promise for improving existing diagnostic and therapeutic techniques. This review summarizes some of the essential aspects of the fabrication techniques used to generate these fascinating nanostructures, comparing their material properties and suitability for biomedical applications. We examine the literature in regards to toxicity, biocompatibility and biodistribution of silicon nanoparticles, nanowires and nanotubes, with an emphasis on surface modification and its influence on cell adhesion and endocytosis. In the final part of this review, our attention is focused on current applications of the fabricated silicon nanostructures in nanomedicine, specifically examining drug and gene delivery, bioimaging and biosensing.

Photoresponsive immunomagnetic nanocarrier for capture and release of rare circulating tumor cells

7-Aminocoumarin compound was synthesized and used as phototrigger to cage EpCAM-antibody to construct a photocontrolled CTCs capture and release system.

Isolation, release and culture of rare circulating tumor cells (CTCs) may, if implemented, promote the progress of individualized anti-tumor therapies. To realize the release of CTCs without disruption of their viability for further culture and analysis, we designed an effective photocontrolled CTC capture/release system by combination of photochemistry and immunomagnetic separation. 7-Aminocoumarin was synthesized as the phototrigger to bridge the connection between the anti-EpCAM antibody and the magnetic beads. The coumarin moieties produced cleavage of a C–O bond under both ultraviolet (UV) and near-infrared (NIR) light illumination, breaking the bridge and releasing CTCs from the immunomagnetic beads. Compared with conventional immunomagnetic separation systems, the negative influence of absorbed immunomagnetic beads on further CTCs culture and analysis was effectively eliminated. The system can specifically recognize 10² MCF-7 cells in 1 mL of human whole blood samples with 90% efficiency and 85% purity. Under the irradiation of UV and NIR light, 73 ± 4% and 52 ± 6% of captured cells were released with a viability of 90% and 97%, respectively. Furthermore, this technique has been used to detect CTCs from whole blood of cancer patients with high purity. This study demonstrates that the photochemical-based immunomagnetic separation method for isolating, releasing and culturing CTCs from clinic patients may provide new opportunities for cancer diagnosis and personalized therapy.

Stimuli-Responsive Surfaces for Tunable and Reversible Control of Wettability

Surfaces with controllable wettability can be fabricated by embedding superhydrophobic particles into stimuli-responsive hydrogels. When the hydrogel changes its size due to a specific stimulus, the wettability of the surface can be reversibly tuned from superhydrophobic to superhydrophilic. This general method is used to fabricate "smart" membranes for controlling the permeability of chemicals under the influence of multiple stimuli simultaneously.

Silicon nanostructures for cancer diagnosis and therapy

The emergence of nanotechnology suggests new and exciting opportunities for early diagnosis and therapy of cancer. During the recent years, silicon-based nanomaterials featuring unique properties have received great attention, showing high promise for myriad biological and biomedical applications. In this review, we will particularly summarize latest representative achievements on the development of silicon nanostructures as a powerful platform for cancer early diagnosis and therapy. First, we introduce the silicon nanomaterial-based biosensors for detecting cancer markers (e.g., proteins, tumor-suppressor genes and telomerase activity, among others) with high sensitivity and selectivity under molecular level. Then, we summarize in vitro and in vivo applications of silicon nanostructures as efficient nanoagents for cancer therapy. Finally, we discuss the future perspective of silicon nanostructures for cancer diagnosis and therapy.

Supramolecular nanosubstrate-mediated delivery for reprogramming and transdifferentiation of mammalian cells

Supramolecular nanosubstrate-mediated delivery (SNSMD) leverages the power of molecular self-assembly and a nanostructured substrate platform for the low toxicity, highly efficient co-delivery of biological factors encapsulated in a nanovector. Human fibroblasts are successfully reprogrammed into induced pluripotent stems and transdifferentiated into induced neuronal-like cells.

Selective Capture and Quick Detection of Targeting Cells with SERS-Coding Microsphere Suspension Chip

Circulating tumor cells (CTCs) captured from blood fluid represent recurrent cancers and metastatic lesions to monitor the situation of cancers. We develop surface-enhanced Raman scattering (SERS)-coding microsphere suspension chip as a new strategy for fast and efficient capture, recovery, and detection of targeting cancer cells. Using HeLa cells as model CTCs, we first utilize folate as a recognition molecule to be immobilized in magnetic composite microspheres for capturing HeLa cells and attaining high capturing efficacy (up to 95%). After capturing cells, the composite microsphere, which utilizes a disulfide bond as crosslinker in the polymer shell and as a spacer for linking folate, can recycle 90% cells within 20 min eluted by glutathion solution. Taking advantage of the SERS with fingerprint features, we characterize captured/recovered cells with the unique signal of report-molecule 4-aminothiophenol through introducing the SERS-coding microsphere suspension chip to CTCs. Finally, the exploratory experiment of sieving cells shows that the magnetic composite microspheres can selectively capture the HeLa cells from samples of mixed cells, indicating that these magnetic composite microspheres have potential in real blood samples for capturing CTCs.

Nanotentacle-structured magnetic particles for efficient capture of circulating tumor cells

Circulating tumor cells (CTCs) have attracted considerable attention as promising markers for diagnosing and monitoring the cancer status. Despite many technological advances in isolating CTCs, the capture efficiency and purity still remain challenges that limit clinical practice. Here, the construction of "nanotentacle"-structured magnetic particles using M13-bacteriophage and their application for the efficient capturing of CTCs is demonstrated. The M13-bacteriophage to magnetic particles followed by modification with PEG is conjugated, and further tethered monoclonal antibodies against the epidermal receptor 2 (HER2). The use of nanotentacle-structured magnetic particles results in a high capture purity (>45%) and efficiency (>90%), even for a smaller number of cancer cells (≈25 cells) in whole blood. Furthermore, the cancer cells captured are shown to maintain a viability of greater than 84%. The approach can be effectively used for capturing CTCs with high efficiency and purity for the diagnosis and monitoring of cancer status.

Silicon-nanowire based attachment of silicon chips for mouse embryo labelling

The adhesion of small silicon chips to cells has many potential applications as direct interconnection of the cells to the external world can be accomplished. Hence, although some typical applications of silicon nanowires integrated into microsystems are focused on achieving a cell-on-a-chip strategy, we are interested in obtaining chip-on-a-cell systems. This paper reports the design, technological development and characterization of polysilicon barcodes featuring silicon nanowires as nanoscale attachment to identify and track living mouse embryos during their in vitro development. The chips are attached to the outer surface of the Zona Pellucida, the cover that surrounds oocytes and embryos, to avoid the direct contact between the chip and the embryo cell membrane. Two attachment methodologies, rolling and pushpin, which allow two entirely different levels of applied forces to attach the chips to living embryos, are evaluated. The former consists of rolling the mouse embryos over one barcode with the silicon nanowires facing upwards, while in the latter, the barcode is pushed against the embryo with a micropipette. The effect on in vitro embryo development and the retention rate related to the calculated applied forces are stated. Field emission scanning electron microscopy inspection, which allowed high-resolution imaging, also confirms the physical attachment of the nanowires with some of them piercing or wrapped by the Zona Pellucida and revealed extraordinary bent silicon nanowires.

Tunable nanostructured coating for the capture and selective release of viable circulating tumor cells

A layer-by-layer gelatin nanocoating is presented for use as a tunable, dual response biomaterial for the capture and release of circulating tumor cells (CTCs) from cancer patient blood. The entire nanocoating can be dissolved from the surface of microfluidic devices through biologically compatible temperature shifts. Alternatively, individual CTCs can be released through locally applied mechanical stress.

Programming thermoresponsiveness of NanoVelcro substrates enables effective purification of circulating tumor cells in lung cancer patients

Unlike tumor biopsies that can be constrained by problems such as sampling bias, circulating tumor cells (CTCs) are regarded as the "liquid biopsy" of the tumor, providing convenient access to all disease sites, including primary tumor and fatal metastases. Although enumerating CTCs is of prognostic significance in solid tumors, it is conceivable that performing molecular and functional analyses on CTCs will reveal much significant insight into tumor biology to guide proper therapeutic intervention. We developed the Thermoresponsive NanoVelcro CTC purification system that can be digitally programmed to achieve an optimal performance for purifying CTCs from non-small cell lung cancer (NSCLC) patients. The performance of this unique CTC purification system was optimized by systematically modulating surface chemistry, flow rates, and heating/cooling cycles. By applying a physiologically endurable stimulation (i.e., temperature between 4 and 37 °C), the mild operational parameters allow minimum disruption to CTCs' viability and molecular integrity. Subsequently, we were able to successfully demonstrate culture expansion and mutational analysis of the CTCs purified by this CTC purification system. Most excitingly, we adopted the combined use of the Thermoresponsive NanoVelcro system with downstream mutational analysis to monitor the disease evolution of an index NSCLC patient, highlighting its translational value in managing NSCLC.

PDMS micropillar-based microchip for efficient cancer cell capture

We introduce a micropillar-based microfluidic device for efficient and rapid cancer cell capture.

Cancer biomarker detection: recent achievements and challenges

We provide an overview covering the existing challenges and latest developments in achieving high selectivity and sensitivity cancer-biomarker detection.

Immobilization of nattokinase-loaded red blood cells on the surface of superhydrophobic polypropylene targeting fibrinolytic performance

A superhydrophobic polypropylene (PP) platform with fibrinolytic ability was fabricated by capturing and releasing nattokinase (NK)-encapsulating red blood cells (RBCs).

An integrated microfluidic chip system for single-cell secretion profiling of rare circulating tumor cells

Genetic and transcriptional profiling, as well as surface marker identification of single circulating tumor cells (CTCs) have been demonstrated. However, quantitatively profiling of functional proteins at single CTC resolution has not yet been achieved, owing to the limited purity of the isolated CTC populations and a lack of single-cell proteomic approaches to handle and analyze rare CTCs. Here, we develop an integrated microfluidic system specifically designed for streamlining isolation, purification and single-cell secretomic profiling of CTCs from whole blood. Key to this platform is the use of photocleavable ssDNA-encoded antibody conjugates to enable a highly purified CTC population with <75 ‘contaminated' blood cells. An enhanced poly-L-lysine barcode pattern is created on the single-cell barcode chip for efficient capture rare CTC cells in microchambers for subsequent secreted protein profiling. This system was extensively evaluated and optimized with EpCAM-positive HCT116 cells seeded into whole blood. Patient blood samples were employed to assess the utility of the system for isolation, purification and single-cell secretion profiling of CTCs. The CTCs present in patient blood samples exhibit highly heterogeneous secretion profile of IL-8 and VEGF. The numbers of secreting CTCs are found not in accordance with CTC enumeration based on immunostaining in the parallel experiments.

Aptamer-functionalized barcode particles for the capture and detection of multiple types of circulating tumor cells

Aptamer-functionalized barcode particles are employed to capture and detect various types of circulating tumor cells (CTCs). The particles are spherical colloidal crystal clusters, and the reflection properties that arise from their structures are how their codes are evaluated. Aptamer functionalization (with TD05, Sgc8, and Sgd5) make the particles interact with specific CTC types; dendrimers are used to amplify the effect of the aptamers, allowing for increased sensitivity, reliability, and specificity in CTC capture, detection, and subsequent release.

Nanotopographic Biomaterials for Isolation of Circulating Tumor Cells

Circulating tumor cells (CTCs) shed from the primary tumor mass and circulating in the bloodstream of patients are believed to be vital to understand of cancer metastasis and progression. Capture and release of CTCs for further enumeration and molecular characterization holds the key for early cancer diagnosis, prognosis and therapy evaluation. However, detection of CTCs is challenging due to their rarity, heterogeneity and the increasing demand of viable CTCs for downstream biological analysis. Nanotopographic biomaterial-based microfluidic systems are emerging as promising tools for CTC capture with improved capture efficiency, purity, throughput and retrieval of viable CTCs. This review offers a brief overview of the recent advances in this field, including CTC detection technologies based on nanotopographic biomaterials and relevant nanofabrication methods. Additionally, the possible intracellular mechanisms of the intrinsic nanotopography sensitive responses that lead to the enhanced CTC capture are explored.

Nanostructure embedded microchips for detection, isolation, and characterization of circulating tumor cells

Circulating tumor cells (CTCs) are cancer cells that break away from either a primary tumor or a metastatic site and circulate in the peripheral blood as the cellular origin of metastasis. With their role as a “tumor liquid biopsy”, CTCs provide convenient access to all disease sites, including that of the primary tumor and the site of fatal metastases. It is conceivable that detecting and analyzing CTCs will provide insightful information in assessing the disease status without the flaws and limitations encountered in performing conventional tumor biopsies. However, identifying CTCs in patient blood samples is technically challenging due to the extremely low abundance of CTCs among a large number of hematologic cells. To address this unmet need, there have been significant research endeavors, especially in the fields of chemistry, materials science, and bioengineering, devoted to developing CTC detection, isolation, and characterization technologies.

Inspired by the nanoscale interactions observed in the tissue microenvironment, our research team at UCLA pioneered a unique concept of “NanoVelcro” cell-affinity substrates, in which CTC capture agent-coated nanostructured substrates were utilized to immobilize CTCs with high efficiency. The working mechanism of NanoVelcro cell-affinity substrates mimics that of Velcro: when the two fabric strips of a Velcro fastener are pressed together, tangling between the hairy surfaces on two strips leads to strong binding. Through continuous evolution, three generations (gens) of NanoVelcro CTC chips have been established to achieve different clinical utilities. The first-gen NanoVelcro chip, composed of a silicon nanowire substrate (SiNS) and an overlaid microfluidic chaotic mixer, was created for CTC enumeration. Side-by-side analytical validation studies using clinical blood samples suggested that the sensitivity of first-gen NanoVelcro chip outperforms that of FDA-approved CellSearch. In conjunction with the use of the laser microdissection (LMD) technique, second-gen NanoVelcro chips (i.e., NanoVelcro-LMD), based on polymer nanosubstrates, were developed for single-CTC isolation. The individually isolated CTCs can be subjected to single-CTC genotyping (e.g., Sanger sequencing and next-generation sequencing, NGS) to verify the CTC’s role as tumor liquid biopsy. Created by grafting of thermoresponsive polymer brushes onto SiNS, third-gen NanoVelcro chips (i.e., Thermoresponsive NanoVelcro) have demonstrated the capture and release of CTCs at 37 and 4 °C, respectively. The temperature-dependent conformational changes of polymer brushes can effectively alter the accessibility of the capture agent on SiNS, allowing for rapid CTC purification with desired viability and molecular integrity.

This Account summarizes the continuous evolution of NanoVelcro CTC assays from the emergence of the original idea all the way to their applications in cancer research. We envision that NanoVelcro CTC assays will lead the way for powerful and cost-efficient diagnostic platforms for researchers to better understand underlying disease mechanisms and for physicians to monitor real-time disease progression.

Microfluidics for single-cell genetic analysis

The ability to correlate single-cell genetic information to cellular phenotypes will provide the kind of detailed insight into human physiology and disease pathways that is not possible to infer from bulk cell analysis. Microfluidic technologies are attractive for single-cell manipulation due to precise handling and low risk of contamination. Additionally, microfluidic single-cell techniques can allow for high-throughput and detailed genetic analyses that increase accuracy and decrease reagent cost compared to bulk techniques. Incorporating these microfluidic platforms into research and clinical laboratory workflows can fill an unmet need in biology, delivering the highly accurate, highly informative data necessary to develop new therapies and monitor patient outcomes. In this perspective, we describe the current and potential future uses of microfluidics at all stages of single-cell genetic analysis, including cell enrichment and capture, single-cell compartmentalization and manipulation, and detection and analyses.

3D bioelectronic interface: capturing circulating tumor cells onto conducting polymer-based micro/nanorod arrays with chemical and topographical control

The three-dimensional (3D) poly(3,4-ethylenedioxythiophene) (PEDOT)-based bioelectronic interfaces (BEIs) with diverse dimensional micro/nanorod array structures, varied surface chemical pro-perties, high electrical conductivity, reversible chemical redox switching, and high optical transparency are used for capturing circulating tumor cells (CTCs). Such 3D PEDOT-based BEIs can function as an efficient clinical diagonstic and therapeutic platform.

Spatially selective release of aptamer-captured cells by temperature mediation

Isolation of cells from heterogeneous biological samples is critical in both basic biological research and clinical diagnostics. Affinity-based methods, such as those that recognise cells by binding antibodies to cell membrane biomarkers, can be used to achieve specific cell isolation. Microfluidic techniques have been employed to achieve more efficient and effective cell isolation. By employing aptamers as surface-immobilised ligands, cells can be easily released and collected after specific capture. However, these methods still have limitations in cell release efficiency and spatial selectivity. This study presents an aptamer-based microfluidic device that not only achieves specific affinity cell capture, but also enables spatially selective temperature-mediated release and retrieval of cells without detectable damage. The specific cell capture is realised by using surface-patterned aptamers in a microchamber on a temperature-control chip. Spatially selective cell release is achieved by utilising a group of microheater and temperature sensor that restricts temperature changes, and therefore the disruption of cell-aptamer interactions, to a design-specified region. Experimental results with CCRF-CEM cells and sgc8c aptamers have demonstrated the specific cell capture and temperature-mediated release of selected groups of cells with negligible disruption to their viability.

Differential detection of tumor cells using a combination of cell rolling, multivalent binding, and multiple antibodies

Effective quantification and in situ identification of circulating tumor cells (CTCs) in blood are still elusive because of the extreme rarity and heterogeneity of the cells. In our previous studies, we developed a novel platform that captures tumor cells at significantly improved efficiency in vitro using a unique biomimetic combination of two physiological processes: E-selectin-induced cell rolling and poly(amidoamine) (PAMAM) dendrimer-mediated strong multivalent binding. Herein, we have engineered a novel multifunctional surface, on the basis of the biomimetic cell capture, through optimized incorporation of multiple antibodies directed to cancer cell-specific surface markers, such as epithelial cell adhesion molecule (EpCAM), human epidermal growth factor receptor-2 (HER-2), and prostate specific antigen (PSA). The surfaces were tested using a series of tumor cells, MDA-PCa-2b, MCF-7, and MDA-MB-361, both in mixture in vitro and after being spiked into human blood. Our multifunctional surface demonstrated highly efficient capture of tumor cells in human blood, achieving up to 82% capture efficiency (∼10-fold enhancement than a surface with the antibodies alone) and up to 90% purity. Furthermore, the multipatterned antibodies allowed differential capturing of the tumor cells. These results support that our multifunctional surface has great potential as an effective platform that accommodates virtually any antibodies, which will likely lead to clinically significant, differential detection of CTCs that are rare and highly heterogeneous.

Dual-aptamer modification generates a unique interface for highly sensitive and specific electrochemical detection of tumor cells

Because circulating tumor cells (CTCs) have been proven to be an important clue of the tumor metastasis, their detection thus plays a pivotal role in the diagnosis and prognosis of cancer. Herein, we fabricate an electrochemical sensor by directly conjugating two cell-specific aptamers, TLS1c and TLS11a, which specifically recognize MEAR cancer cells, to the surface of a glassy carbon electrode (GCE) via the formation of amide bonds. The two aptamers are simultaneously conjugated to the GCE surface via precisely controlled linkers: TLS1c through a flexible linker (a single-stranded DNA T15; ss-TLS1c) and TLS11a through a rigid linker (a double-stranded DNA T15/A15; ds-TLS11a). It is found that such ss-TLS1c/ds-TLS11a dual-modified GCEs show greatly improved sensitivity in comparison with those modified with a single type of aptamer alone or ds-TLS1c/ds-TLS11a with both rigid linkers, suggesting that our optimized, rationally designed electrode-aptamer biosensing interface may enable better recognition and thus more sensitive detection of tumor cells. Through the utilization of this dual-aptamer-modified GCE, as few as a single MEAR cell in 10(9) whole blood cells can be successfully detected with a linear range of 1-14 MEAR cells. Our work demonstrates a rather simple yet well-designed and ultrasensitive tumor cell detection method based on the cell-specific aptamer-modified GCE, showing a promising potential for further CTC-related clinical applications.

Carboxybetaine methacrylate-modified nylon surface for circulating tumor cell capture

Conventional in vitro circulating tumor cell (CTC) detection methods are always limited by blood sample volume because of the requirement of a large amount of blood. The aim of this study was to overcome the limitation by designing and making an in vivo CTC capture device. In this study, we designed and prepared a kind of proper material to serve the purpose of intervention. A method employing 3-aminopropyltriethoxysilane (γ-APS) as the coupling reagent to graft carboxybetaine methacrylate (CBMA) and to immobilize an anti-epithelial cell adhesion molecular (EpCAM) antibody on Nylon was developed. The results of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy proved the successful graft of γ-APS and CBMA to Nylon. Furthermore, the predicted improvement in the biocompatibilities of our modified Nylon was confirmed by water contact angle measurement, bovine serum albumin adhesion, platelet adhesion, plasma recalcification time determination, and cytotoxicity tests. The tumor cells adhesion experiment revealed that Nylon with the antibody immobilized on it had an affinity for EpCAM positive tumor cells higher than that of pristine Nylon. Additionally, the capture ability of the CTCs was demonstrated in a nude mouse tumor model using the interventional device made of the modified Nylon wire. The positive results suggest that CBMA-grafted and anti-EpCAM antibody-immobilized Nylon is a promising new material for in vivo CTC capture devices.

Emerging role of nanomaterials in circulating tumor cell isolation and analysis

Circulating tumor cells (CTCs) are low frequency cells found in the bloodstream after having been shed from a primary tumor. These cells are research targets because of the information they may potentially provide about both an individual cancer as well as the mechanisms through which cancer spreads in the process of metastasis. Established technologies exist for CTC isolation, but the recent progress and future of this field lie in nanomaterials. In this review, we provide perspective into historical CTC capture as well as current research being conducted, emphasizing the significance of the materials being used to fabricate these devices. The modern investigation into CTCs initially featured techniques that have since been commercialized. A major innovation in the field was the development of a microfluidic capture device, first fabricated in silicon and followed up with glass and thermopolymer devices. We then specifically highlight the technologies incorporating magnetic nanoparticles, carbon nanotubes, nanowires, nanopillars, nanofibers, and nanoroughened surfaces, graphene oxide and their fabrication methods. The nanoscale provides a new set of tools that has the potential to overcome current limitations associated with CTC capture and analysis. We believe the current trajectory of the field is in the direction of nanomaterials, allowing the improvements necessary to further CTC research.

Technologies for detection of circulating tumor cells: facts and vision

Hematogeneous tumor cell dissemination is a key step in cancer progression. The detection of CTCs in the peripheral blood of patients with solid epithelial tumors (e.g., breast, prostate, lung and colon cancer) holds great promise, and many exciting technologies have been developed over the past years. However, the detection and molecular characterization of circulating tumor cells (CTCs) remain technically challenging. The identification and characterization of CTCs require extremely sensitive and specific analytical methods, which are usually a combination of complex enrichment and detection procedures. CTCs occur at very low concentrations of one tumor cell in the background of millions of normal blood cells and the epithelial-mesenchymal plasticity of CTCs can hamper their detection by the epithelial markers used in current CTC assays. In the present review, we summarize current methods for the enrichment and detection of CTCs and discuss the key challenges and perspectives of CTC analyses within the context of improved clinical management of cancer patients.

Vertical SiNWAs for biomedical and biotechnology applications

Vertical silicon nanowire arrays (SiNWAs) are considered as one of the most promising nanomaterials.

Dendrimer-functionalized electrospun cellulose acetate nanofibers for targeted cancer cell capture applications

Multifunctional folic acid-functionalized dendrimers can be modified on the surface of electrospun cellulose acetate nanofibers for the specific capture of FAR-overexpressing cancer cells.

Surface design of antibody-immobilized thermoresponsive cell culture dishes for recovering intact cells by low-temperature treatment

Antibody-immobilized thermoresponsive poly(N-isopropylacrylamide-co-2-carboxyisopropylacrylamide) [poly(IPAAm-co-CIPAAm)]-grafted cell culture surfaces were designed to enhance both the initial adhesion of weakly adhering cells and the ability of cells to detach in response to low temperature through the regulation of affinity binding between immobilized antibodies and antigens on the cellular surface. Ty-82 cells and neonatal normal human dermal fibroblasts (NHDFs), which express CD90 on the cell surface, adhered to anti-CD90 antibody-immobilized thermoresponsive surfaces at 37°C, a condition at which the grafted thermoresponsive polymer chains shrank. Adherent Ty-82 cells were detached from the surfaces by lowering the temperature to 20°C and applying external forces, such as pipetting, whereas cultured NHDF sheets spontaneously detached themselves from the surface in response to reduced temperature alone. When the temperature was decreased to 20°C, the swelling of grafted thermoresponsive polymer chains weakened the affinity binding between immobilized antibody and antigen on the cells due to the increasing steric hindrance of the polymer chains around the antigen-recognition site of the immobilized antibodies. No contamination was detected on cells harvested from covalently immobilized antibodies on the culture surfaces by low-temperature treatment, whereas a carryover of the antibody and avidin from the avidin-biotin binding surface was observed. Furthermore, the initial adhesion of adipose tissue-derived cells, which adhere weakly to PIPAAm-grafted surfaces, was enhanced on the antibody-immobilized thermoresponsive surfaces.

High-purity prostate circulating tumor cell isolation by a polymer nanofiber-embedded microchip for whole exome sequencing

Handpick single cancer cells: a modified NanoVelcro Chip is coupled with ArcturusXT laser capture microdissection (LCM) technology to enable the detection and isolation of single circulating tumor cells (CTCs) from patients with prostate cancer (PC). This new approach paves the way for conducting next-generation sequencing (NGS) on single CTCs.