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

Neutrophil membrane-coated immunomagnetic nanoparticles for efficient isolation and analysis of circulating tumor cells

The isolation and analysis of scarce circulating tumor cells (CTCs) with immunomagnetic nanoparticles (IMNs) have shown promising outcomes in noninvasive cancer diagnosis. However, the IMNs adsorb nonspecific proteins after entering into biofluids and the formed protein coronas cover surface targeting ligands, limiting the detection efficiency of IMNs. In addition, the interaction between surface targeting ligands and white blood cells (WBCs) significantly limits the purity of CTCs isolated by IMNs. Furthermore, the interfacial collision of nanoparticles and cells has negative effects on the viability of isolated CTCs. All of these limitations synthetically restrict the isolation and analysis of rare CTCs for early diagnosis and precision medicine. Here, we proposed that surface functionalization of IMNs with neutrophil membranes can simultaneously reduce nonspecific protein adsorption, enhance the interaction with CTCs, reduce the distraction from WBCs, and improve the viability of isolated CTCs. In spiked blood samples, our neutrophil membrane-coated IMNs (Neu-IMNs) exhibited a superior separation efficiency from 41.36% to 96.82% and an improved purity from 40.25% to 90.68% when compared to bare IMNs. Additionally, we successfully isolated CTCs in 19 out of total 20 blood samples from breast cancer patients using Neu-IMNs and further confirmed the feasibility of the isolated CTCs for downstream cell sequencing. Our work provides a new perspective on engineered IMNs for efficient isolation and analysis of CTCs, paving the way for early noninvasive diagnosis of cancer.

Nanomaterial-Based Immunocapture Platforms for the Recognition, Isolation, and Detection of Circulating Tumor Cells

Circulating tumor cells (CTCs) are a type of cancer cells that circulate in the peripheral blood after breaking away from solid tumors and are essential for the establishment of distant metastasis. Up to 90% of cancer-related deaths are caused by metastatic cancer. As a new type of liquid biopsy, detecting and analyzing CTCs will provide insightful information for cancer diagnosis, especially the in-time disease status, which would avoid some flaws and limitations of invasive tissue biopsy. However, due to the extremely low levels of CTCs among a large number of hematologic cells, choosing immunocapture platforms for CTC detection and isolation will achieve good performance with high purity, selectivity, and viability. These properties are directly associated with precise downstream analysis of CTC profiling. Recently, inspired by the nanoscale interactions of cells in the tissue microenvironment, platforms based on nanomaterials have been widely explored to efficiently enrich and sensitively detect CTCs. In this review, various immunocapture platforms based on different nanomaterials for efficient isolation and sensitive detection of CTCs are outlined and discussed. First, the design principles of immunoaffinity nanomaterials are introduced in detail. Second, the immunocapture and release of platforms based on nanomaterials ranging from nanoparticles, nanostructured substrates, and immunoaffinity microfluidic chips are summarized. Third, recent advances in single-cell release and analysis of CTCs are introduced. Finally, some perspectives and challenges are provided in future trends of CTC studies.

Recent Advances in Aptamer-Based Liquid Biopsy

Liquid biopsy capable of noninvasive and real-time molecular profiling is considered as a breakthrough technology, endowing an opportunity for precise diagnosis of individual patients. Extracellular vesicles (EVs) and circulating tumor cells (CTCs) consisting of substantial disease-related molecular information play an important role in liquid biopsy. Therefore, it is critically significant to exploit high-performance recognition ligands for efficient isolation and analysis of EVs and CTCs from complex body fluids. Aptamers exhibit extraordinary merits of high specificity and affinity, which are considered as superior recognition ligands for liquid biopsy. In this review, we first summarize recent advanced strategies for the evolution of high-performance aptamers and the construction of various aptamer-based recognition elements. Subsequently, we mainly discuss the isolation and analysis of EVs and CTCs based on the aptamer functioned biomaterials/biointerface. Ultimately, we envision major challenges and future direction of aptamer-based liquid biopsy for clinical utilities.

Liquid biopsy in chronic liver disease

Chronic liver diseases account for a considerable toll of incapacities, suffering, deaths, and resources of the nation's health systems. They can be prevented, treated or even cured when the diagnosis is made on time. Traditional liver biopsy remains the gold standard to diagnose liver diseases, but it has several limitations. Liquid biopsy is emerging as a superior alternative to surgical biopsy given that it surpasses the limitations: it is more convenient, readily and repeatedly accessible, safe, cheap, and provides a more detailed molecular and cellular representation of the individual patient's disease. Progress in understanding the molecular and cellular bases of diseased tissues and organs that normally release cells and cellular components into the bloodstream is catapulting liquid biopsy as a source of biomarkers for diagnosis, prognosis, and prediction of therapeutic response, thus supporting the realization of the promises of precision medicine. The review aims to summarize the evidence of the usefulness of liquid biopsy in liver diseases, including the presence of different biomarkers as circulating epithelial cells, cell-free nucleic acids, specific species of DNA and RNA, and the content of extracellular vesicles.

Hyaluronic acid-functionalized redox responsive immunomagnetic nanocarrier for circulating tumor cell capture and release

Detection of circulating tumor cells (CTCs) in peripheral blood holds significant insights for cancer diagnosis, prognosis evaluation, and precision medicine. To efficiently capture and release CTCs with high viability, we reported the development of hyaluronic acid (HA)-functionalized redox responsive immunomagnetic nanocarrier (Fe₃O₄@SiO₂-SS-HA). First, Fe₃O₄nanoparticles were prepared and modified with tetraethyl orthosilicate (TEOS), 3-mercaptopropyltrimethoxysilane (MPTMS) and 2,2'-dithiodipyridine (DDPy) to form the magnetic substrate (Fe₃O₄@SiO₂-SSPy). Modified with targeted segment HA-functionalized L-cysteine ethyl ester hydrochloride (HA-Cys) via disulfide exchange reaction, the Fe₃O₄@SiO₂-SS-HA was formed. The nanocarrier with prominent magnetic property, targeting ligand, and redox-sensitive disulfide linkages was able to specially capture MCF-7 cells with an efficiency of 92% and effectively release captured cells with an efficiency of 81.4%. Furthermore, the Fe₃O₄@SiO₂-SS-HA could successfully be used for the capture of MCF-7 cells, and the captured cells could be diferntiated from the blood cells. Almost all of released tumor cells kept good viability and a robust proliferative capacity after being re-cultured. It is likely that the as-prepared nanocarrier will serve as a new weapon against CD44 receptor-overexpressed cancer cells.

Nucleic Acid Tests for Clinical Translation

Nucleic acids, including deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), are natural biopolymers composed of nucleotides that store, transmit, and express genetic information. Overexpressed or underexpressed as well as mutated nucleic acids have been implicated in many diseases. Therefore, nucleic acid tests (NATs) are extremely important. Inspired by intracellular DNA replication and RNA transcription, in vitro NATs have been extensively developed to improve the detection specificity, sensitivity, and simplicity. The principles of NATs can be in general classified into three categories: nucleic acid hybridization, thermal-cycle or isothermal amplification, and signal amplification. Driven by pressing needs in clinical diagnosis and prevention of infectious diseases, NATs have evolved to be a rapidly advancing field. During the past ten years, an explosive increase of research interest in both basic research and clinical translation has been witnessed. In this review, we aim to provide comprehensive coverage of the progress to analyze nucleic acids, use nucleic acids as recognition probes, construct detection devices based on nucleic acids, and utilize nucleic acids in clinical diagnosis and other important fields. We also discuss the new frontiers in the field and the challenges to be addressed.

A Three-Dimensional Conductive Scaffold Microchip for Effective Capture and Recovery of Circulating Tumor Cells with High Purity

Effective acquirement of highly pure circulating tumor cells (CTCs) is very important for CTC-related research. However, it is a great challenge since abundant white blood cells (WBCs) are always co-collected with CTCs because of nonspecific bonding or low depletion rate of WBCs in various CTC isolation platforms. Herein, we designed a three-dimensional (3D) conductive scaffold microchip for highly effective capture and electrochemical release of CTCs with high purity. The conductive 3D scaffold was prepared by dense immobilization of gold nanotubes (Au NTs) on porous polydimethylsiloxane and was functionalized with a CTC-specific biomolecule facilitated by a Au-S bond before embedding into a microfluidic device. The spatially distributed 3D macroporous structure compelled cells to change migration from linear to chaotic and the densely covered Au NTs enhanced the topographic interaction between cells and the substrate, thus synergistically improving the CTC capture efficiency. The Au NT-coated 3D scaffold had good electrical conductivity and the Au-S bond was breakable by voltage exposure so that captured CTCs could be specifically released by electrochemical stimulation while nonspecifically bonded WBCs were not responsive to this process, facilitating recovery of CTCs with high purity. The 3D conductive scaffold microchip was successfully applied to obtain highly pure CTCs from cancer patients' blood, benefiting the downstream analysis of CTCs.

Aptamer-Based Detection of Circulating Targets for Precision Medicine

The past decade has witnessed ongoing progress in precision medicine to improve human health. As an emerging diagnostic technique, liquid biopsy can provide real-time, comprehensive, dynamic physiological and pathological information in a noninvasive manner, opening a new window for precision medicine. Liquid biopsy depends on the sensitive and reliable detection of circulating targets (e.g., cells, extracellular vesicles, proteins, microRNAs) from body fluids, the performance of which is largely governed by recognition ligands. Aptamers are single-stranded functional oligonucleotides, capable of folding into unique tertiary structures to bind to their targets with superior specificity and affinity. Their mature evolution procedure, facile modification, and affinity regulation, as well as versatile structural design and engineering, make aptamers ideal recognition ligands for liquid biopsy. In this review, we present a broad overview of aptamer-based liquid biopsy techniques for precision medicine. We begin with recent advances in aptamer selection, followed by a summary of state-of-the-art strategies for multivalent aptamer assembly and aptamer interface modification. We will further describe aptamer-based micro-/nanoisolation platforms, aptamer-enabled release methods, and aptamer-assisted signal amplification and detection strategies. Finally, we present our perspectives regarding the opportunities and challenges of aptamer-based liquid biopsy for precision medicine.

Multi-layer assembly of cellulose nanofibrils in a microfluidic device for the selective capture and release of viable tumor cells from whole blood

According to reports by the World Health Organization (WHO), cancer-related deaths reached almost 10 million in 2018. Nearly 65% of these deaths occurred in low- to middle-income countries, a trend that is bound to increase since cancer diagnostics are not currently considered a priority in resource-limited settings (RLS). Thus, cost-effective and specific cancer screening and diagnostics tools are in high demand, particularly in RLS. The selective isolation and up-concentration of rare cells while maintaining cell viability and preventing phenotypic changes is a powerful tool to allow accurate and sensitive downstream analysis. Here, multi-layer cellulose nanofibril-based coatings functionalized with anti-EpCAM antibodies on the surface of disposable microfluidic devices were optimized for specific capture of target cells, followed by efficient release without significant adverse effects. HCT 116 colon cancer cells were captured in a single step with >97% efficiency at 41.25 μL min-1 and, when spiked in whole blood, an average enrichment factor of ∼200-fold relative to white blood cells was achieved. The release of cells was performed by enzymatic digestion of the cellulose nanofibrils which had a negligible impact on cell viability. In particular, >80% of the cells were recovered with at least 97% viability in less than 30 min. Such performance paves the way to expand and improve clinical diagnostic applications by simplifying the isolation of circulating tumor cells (CTCs) and other rare cells directly from whole blood.

Nanotechnology-Assisted Isolation and Analysis of Circulating Tumor Cells on Microfluidic Devices

Circulating tumor cells (CTCs), a type of cancer cell that spreads from primary tumors into human peripheral blood and are considered as a new biomarker of cancer liquid biopsy. It provides the direction for understanding the biology of cancer metastasis and progression. Isolation and analysis of CTCs offer the possibility for early cancer detection and dynamic prognosis monitoring. The extremely low quantity and high heterogeneity of CTCs are the major challenges for the application of CTCs in liquid biopsy. There have been significant research endeavors to develop efficient and reliable approaches to CTC isolation and analysis in the past few decades. With the advancement of microfabrication and nanomaterials, a variety of approaches have now emerged for CTC isolation and analysis on microfluidic platforms combined with nanotechnology. These new approaches show advantages in terms of cell capture efficiency, purity, detection sensitivity and specificity. This review focuses on recent progress in the field of nanotechnology-assisted microfluidics for CTC isolation and detection. Firstly, CTC isolation approaches using nanomaterial-based microfluidic devices are summarized and discussed. The different strategies for CTC release from the devices are specifically outlined. In addition, existing nanotechnology-assisted methods for CTC downstream analysis are summarized. Some perspectives are discussed on the challenges of current methods for CTC studies and promising research directions.

A Multifunctional Platform for the Capture, Release, And Enumeration of Circulating Tumor Cells Based on Aptamer Binding, Nicking Endonuclease-Assisted Amplification, And Inductively Coupled Plasma Mass Spectrometry Detection

Inductively coupled plasma mass spectrometry (ICP-MS) combined with element tags has been well designed and extensively applied in cell enumeration. It possesses superior quantitative capability, strong resistance to matrix interference, multiplex detection capability but destructive characteristic. Herein, we constructed an ICP-MS based multifunctional platform for capture, nondestructive enumeration, and release of circulating tumor cells (CTCs). Aptamer on capture probe recognized Mucin 1 (MUC1) on membrane of MCF-7 cells specifically, thus the cells were captured by probe and the Initiator originally hybridized with Aptamer was substituted by MUC1 and released into solution. Then the released Initiator was separated from the captured cells and hybridized with Tb labeled Substrate on detection probe to release a large amount of nicked Tb fragments through the nicking endonuclease assisted amplification for subsequent ICP-MS detection. Meanwhile, cells captured by probe were released by nuclease digestion for further reculture. Such a strategy effectively avoids CTCs destruction resulted from ICP-MS enumeration, increases the detection sensitivity of ICP-MS by involving nicking endonuclease assisted amplification, and realizes cell recovery for further analysis. A limit of detection of 87 MCF-7 cells and a linear range of 250-10 000 MCF-7 cells were realized for ICP-MS enumeration. A cell recovery of 52.7% (with capture and release efficiency of 63.9 and 82.5%, respectively) and a viability of 74.3% were obtained, meanwhile the released cells exhibited strong proliferation ability. This multifunctional platform for CTCs capture, enumeration, and release has great applicable potential in early diagnosis and individual treatment for cancer.

Differentiation and targeting of HT 29 cancer cells based on folate bioreceptor using cysteamine functionalized gold nano-leaf

Cancer is one of the main causes of death worldwide. To decrease the mortality of cancer, early stage detection of cancer is of great importance. An innovative platform was developed for differentiation and detection of HT 29 cancer cells based on interactions between folate (FA) and folate receptors (FRs) of the membrane of cancer cells. In summary, FA and cysteamine (CA)-functionalized gold nanoparticles (AuNPs) were synthesized and characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS) and Fourier-transform infrared (IR) spectroscopy. Also, the surface charge was determined by measuring of the zeta potential. Fluorescence imaging and flow cytometry analyses were used to approve the selective uptake of the synthesized probe to the cancer cells. HEK 293 FR-negative cells were applied to assess the selectivity of AuNPs/CA/FA towards FR-negative cells. The differential pulse voltammetry (DPV) technique was used to determine the HT 29 cells from 250 to 5000 cells/mL with a lower limit of quantification (LLOQ) of 250 cells/mL. The produced AuNPs/CA/FA based nanoprobe could not only detect the signaling of HT 29 cells but also improve the specificity of cytosensor towards FR-positive cancer cells. According to the obtained results, the newly developed nano-probe could be used as a portable biomedical device for cancer diagnosis.

Antibody-Functional Microsphere-Integrated Filter Chip with Inertial Microflow for Size-Immune-Capturing and Digital Detection of Circulating Tumor Cells

Circulating tumor cells (CTCs) in blood is the direct cause of tumor metastasis. The isolation and detection of CTCs in the whole blood is very important and of clinical value in early diagnosis, postoperative review, and personalized treatment. It is difficult to separate all types of CTCs that efficiently rely on a single path due to cancer cell heterogenicity. Here, we designed a new kind of "filter chip" for the retention of CTCs with very high efficiency by integrating the effects of cell size and specific antigens on the surface of tumor cells. The filter chip consists of a semicircle arc and arrays and can separate large-scale CTC microspheres, which combined with CTCs automatically. We synthesized interfacial zinc oxide coating with nanostructure on the surface of the microsphere to increase the specific surface area to enhance the capturing efficiency of CTCs. Microspheres, trapped in the arrays, would entrap CTCs, too. The combination of the three kinds of strategies resulted in more than 90% capture efficiency of different tumor cell lines. Furthermore, it is easy to find and isolate the circulating tumor cells from the chip as tumor cells would be fixed inside the structure of a filter chip. To avoid the high background contamination when a few CTCs are surrounded by millions of nontarget cells, a digital detection method was applied to improve the detection sensitivity. The CTCs in the whole blood were specifically labeled by the antibody-DNA conjugates and detected via the DNA of the conjugates with a signal amplification. The strategy of the antibody-functional microsphere-integrated microchip for cell sorting and detection of CTCs may find broad implications that favor the fundamental cancer biology research, the precise diagnosis, and monitoring of cancer in the clinics.

Biomimetic Immunomagnetic Nanoparticles with Minimal Nonspecific Biomolecule Adsorption for Enhanced Isolation of Circulating Tumor Cells

Immunomagnetic micro/nanoparticles (IMNs) have been widely used to isolate rare circulating tumor cells (CTCs) from blood samples for early diagnosis of cancers. However, when entering into biofluids, IMNs nonspecifically adsorb biomolecules and the in situ formed biomolecule corona covers IMN surface ligands and weakens the targeting capabilities of IMNs. In this work, we demonstrated that by surface coating of IMNs with red blood cell (RBC)-derived vesicles, the obtained biomimetic particles (RBC-IMNs) basically adsorb no biomolecules and maintain the CTC targeting ability when exposed to plasma. Compared to IMNs, RBC-IMNs exhibited an excellent cell isolation efficiency in spiked blood samples, which was improved to 95.71% from 60.22%. Furthermore, by using RBC-IMNs, we successfully isolated CTCs in 28 out of 30 prostate cancer patient blood samples and further showed the robustness of RBC-IMNs in downstream cell sequencing. The work presented here provides a new insight into developing targeted nanomaterials for biological and medical applications.

Multifunctional Hybrid Magnetic Microgel Synthesis for Immune-Based Isolation and Post-Isolation Culture of Tumor Cells

Circulating tumor cells are of utmost importance among various biomarkers in liquid biopsies as a prognosis indicator of metastasis as well as in chemotherapeutic monitoring. This study introduces an efficient tool composed of soft nano/hybrid immune microgels for magnetic isolation of targeted tumor cells. The development process involves the in situ synthesis of magnetic nanoparticles within the three-dimensional matrix of thermoresponsive microgels. Surface modification and anti-EpCAM conjugation are adjusted by changing the temperature, and a conjugation efficiency of around 70% is achieved by using a protein G linker. Anti-EpCAM-conjugated nano/hybrid magnetic microgels are used to isolate EpCAM-expressing breast adenocarcinoma MCF-7 cells from culture media and whole blood with an efficiency of 75 and 70%, respectively. Furthermore, we demonstrate the ability of the hybrid microgels to isolate cancer cells with a purity of 65% and culture the cells post-isolation for further drug studies. The multifunctional hybrid microcarriers reported in this work can be potentially used for continuous monitoring of cancers and in personalized medicine.

Liquid biopsy in hepatocellular carcinoma: circulating tumor cells and circulating tumor DNA

Hepatocellular carcinoma (HCC) is one of the most common cancers and a leading cause of death worldwide. Due to latent liver disease, late diagnosis, and nonresponse to systemic treatments, surgical resection and/or biopsy specimens are still generally considered as the gold standard by clinicians for clinical decision-making until now. Since the conventional tissue biopsy is invasive and contains small tissue samples, it is unable to represent tumor heterogeneity or monitor dynamic tumor progression. Therefore, it is imperative to find a new less invasive or noninvasive diagnostic strategy to detect HCC at an early stage and to monitor HCC recurrence. Over the past years, a new diagnostic concept known as “liquid biopsy” has emerged with substantial attention. Liquid biopsy is noninvasive and allows repeated analyses to monitor tumor recurrence, metastasis or treatment responses in real time. With the advanced development of new molecular techniques, HCC circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA) detection have achieved interesting and encouraging results. In this review, we focus on the clinical applications of CTCs and ctDNA as key components of liquid biopsy in HCC patients.

Capture and "self-release" of circulating tumor cells using metal-organic framework materials

Capturing circulating tumor cells (CTCs) from peripheral blood for subsequent analyses has shown potential in precision medicine for cancer patients. Broad as the prospect is, there are still some challenges that hamper its clinical applications. One of the challenges is to maintain the viability of the captured cells during the capturing and releasing processes. Herein, we have described a composite material that could encapsulate a magnetic Fe3O4 core in a MIL-100 shell (MMs), which could respond to pH changes and modify the anti-EpCAM antibody (anti-EpCAM-MMs) on the surface of MIL-100. After the anti-EpCAM-MMs captured the cells, there was no need for additional conditions but with the acidic environment during the cell culture process, MIL-100 could realize automatic degradation, leading to cell self-release. This self-release model could not only improve the cell viability, but could also reduce the steps of the release process and save human and material resources simultaneously. In addition, we combined clinical patients' case diagnosis with the DNA sequencing and next generation of RNA sequencing technologies in the hope of precision medicine for patients in the future.

Microfluidic Immiscible Phase Filtration System for the Isolation of Small Numbers of Cells from Whole Blood

Isolation of circulating tumor cells (CTCs) has generated clinical and academic interest due to the important role that CTCs play in cancer metastasis and diagnosis. Here, we present a PDMS and glass prototype of a microfluidic device for the immunomagnetic, immiscible phase filtration based capture, and isolation of MCF-7 breast cancer cells, from various sample matrices including PBS-based buffer, blood plasma, and unprocessed whole blood. Following optimization of surface energy of an oil-water interface, microfluidic geometry, and bead-binding kinematics, our microfluidic device achieved 95 ± 4% recovery of target cells from PBS-based buffer with 95% purity, 90 ± 3% recovery of target cells from blood plasma and recovery of ~70 ± 5% from unprocessed whole blood with purity >99% with 1 ml blood samples with 1,000 spiked target cells. From quantitative studies to assess the nonspecific carryover of contaminants from whole blood, we found that our system accomplishes a >175 fold depletion in platelets, >900 fold depletion in erythrocytes, and >1,700 fold depletion in leukocytes with respect to unprocessed whole blood, enabling us to avoid sample pre-processing. In addition, we found that ~95% of the isolated target cells were viable, making them suitable for subsequent molecular and cellular studies. We quantify and propose mechanisms for the carryover of platelet, erythrocyte, and leukocyte contamination in purified samples, rather than relying on sample pre-processing. These results validate the continued study of our platform for extraction of CTCs from patient samples and other rare cell isolation applications. © 2019 International Society for Advancement of Cytometry.

A Microwell-Assisted Multiaptamer Immunomagnetic Platform for Capture and Genetic Analysis of Circulating Tumor Cells

Detection of circulating tumor cells (CTCs) in peripheral blood is of paramount significance for cancer diagnosis, progress evaluation, and individualized therapy. However, the rareness and heterogeneity of CTCs introduces significant challenges in the capture of cancer cells as well as downstream genetic analysis. In this work, a microwell-assisted multiaptamer immunomagnetic platform (MMAIP) is proposed for highly efficient capture of CTCs with minimum influence of heterogeneity. Assisted by a microwell chip, the purity of CTCs is greatly improved, thus meeting the requirement of downstream gene analysis. This is, as far as is known, the first aptamer based platform enabling mutation analysis of the captured CTCs from cancer patients, which will contribute to the practical application of aptamers in clinics.

A simple pyramid-shaped microchamber towards highly efficient isolation of circulating tumor cells from breast cancer patients

Isolation and detection of circulating tumor cells (CTCs) has showed a great clinical impact for tumor diagnosis and treatment monitoring. Despite significant progresses of the existing technologies, feasible and cost-effective CTC isolation techniques are more desirable. In this study, a novel method was developed for highly efficient isolation of CTCs from breast cancer patients based on biophysical properties using a pyramid-shaped microchamber. Through optimization tests, the outlet height of 6 μm and the flow rate of 200 μL/min were chosen as the optimal conditions. The capture efficiencies of more than 85% were achieved for cancer cell lines (SKBR3, BGC823, PC3, and H1975) spiked in DMEM and healthy blood samples without clogging issue. In clinic assay, the platform identified CTCs in 13 of 20 breast cancer patients (65%) with an average of 4.25 ± 4.96 CTCs/2 mL, whereas only one cell was recognized as CTC in 1 of 15 healthy blood samples. The statistical analyses results demonstrated that both CTC positive rate and CTC counts were positive correlated with TNM stage (p < 0.001; p = 0.02, respectively). This microfluidic platform successfully demonstrated the clinical feasibility of CTC isolation and would hold great potential of clinical application in predicting and monitoring the prognosis of cancer patients.

Advances in liquid biopsy on-chip for cancer management: Technologies, biomarkers, and clinical analysis

Liquid biopsy, as a minimally invasive method of gleaning insight into the dynamics of diseases through a patient fluid sample, has been growing in popularity for cancer diagnosis, prognosis, and monitoring. While many technologies have been developed and validated in research laboratories, there has also been a push to expand these technologies into other clinical settings and as point of care devices. In this article, we discuss and evaluate microchip-based technologies for circulating tumor cell (CTC), exosome, and circulating tumor nucleic acid (ctNA) capture, detection, and analysis. Such integrated systems streamline otherwise multiple-step, manual operations to get a sample-to-answer quantitation. In addition, analysis of disease biomarkers is suited to point of care settings because of ease of use, low consumption of sample and reagents, and high throughput. We also cover the basics of biomarkers and their detection in biological fluid samples suitable for liquid biopsy on-chip. We focus on emerging technologies that process a small patient sample with high spatial-temporal resolution and derive clinically meaningful results through on-chip biomarker sensing and downstream molecular analysis in a simple workflow. This critical review is meant as a resource for those interested in developing technologies for capture, detection, and analysis platforms for liquid biopsy in a variety of settings.

Molecular Profiling of Pooled Circulating Tumor Cells from Prostate Cancer Patients Using a Dual-Antibody-Functionalized Microfluidic Device

To capture both epithelial and mesenchymal subpopulations of CTCs at different metastatic stages of PCa patients, here we constructed a novel dual-antibody-functionalized microfluidic device by employing antibodies against PSMA and EpCAM. In vitro experiments with the dual capture system for capturing both LnCAP and LnCAP-EMT cells have shown significantly enhanced capture efficiency as compared to that of the EpCAM single capture system. Furthermore, the dual capture system could successfully identify CTCs in 20 out of 24 (83.3%) PCa patients, and the CTCs counts from the dual capture system were statistically correlated with the TNM stage of patients ( P < 0.05), while conventional diagnostic methods, such as serum PSA level and Gleason score, failed to correlate to patient TNM stages. To further explore potential clinical application of our dual capture system, captured CTCs were recovered and subjected to qRT-PCR to quantify known factors involved in PCa development and therapy. The results demonstrated that the combined detection of SChLAP1 and PSA in CTCs is a potential marker for identifying patients with metastatic PCa, while detection of AR and PD-L1 in CTCs may have the potential to determine the sensitivity of PCa patients to androgen deprivation therapy and immunotherapy, respectively. Taken together, the dual-antibody-functionalized microfluidic device established in our study overcomes the limitations of some CTC capture platforms that only detect epithelial or mesenchymal CTCs in PCa patients, and detection of the PCa-related RNA signatures from purified CTCs holds great promise to offer warnings for early metastasis of PCa and may provide guidance for therapy decisions.

Stem-like plasticity and heterogeneity of circulating tumor cells: current status and prospect challenges in liver cancer

Poor prognosis and high recurrence remain leading causes of primary liver cancerassociated mortality. The spread of circulating tumor cells (CTCs) in the blood plays a major role in the initiation of metastasis and tumor recurrence after surgery. Nevertheless, only a subset of CTCs can survive, migrate to distant sites and establish secondary tumors. Consistent with cancer stem cell (CSC) hypothesis, stem-like CTCs might represent a potential source for cancer relapse and distant metastasis. Thus, identification of stem-like metastasis-initiating CTC-subset may provide useful clinically prognostic information. This review will emphasize the most relevant findings of CTCs in the context of stem-like biology associated to liver carcinogenesis. In this view, the emerging field of stem-like CTCs may deliver substantial contribution in liver cancer field in order to move to personalized approaches for diagnosis, prognosis and therapy.

Rapid and highly efficient capture and release of cancer cells using polymeric microfibers immobilized with enzyme-cleavable peptides

Circulating tumor cells (CTCs) are tumor cells present in the blood. CTCs have attracted much attention as a new tumor marker, because their analysis provides useful information for monitoring cancer progress. In this study, we developed cell-capture and release methods using three-dimensional (3D) microfiber fabrics without damaging the cells. Using functional peptides containing sequences from a polystyrene-binding site and a cleavable site for collagenase type IV, immobilized antibodies on the peptides were able to specifically capture MCF-7 cells in a few minutes and release the captured cells from 3D microfiber fabrics incorporating a vacuum system. The efficiency of cell capture was around 80% and that of the cell release was over 90%. The released cells proliferated normally in culture medium, suggesting that our system will be applicable for the culture and analysis of CTCs.

STATEMENT OF SIGNIFICANCE

In this paper, we report cell-capture and release methods using enzyme-cleavable peptides immobilized on microfiber fabrics which has microporous polymeric three-dimensional structures. Detachment and collection of the selectively captured cancer cells are required for ex vivo culture and their further analysis, whereas the cell detachment methods developed so far might cause cell damage, even if cell viability is high enough. Therefore, specific attachment and gentle detachment from the device are required for the accurate analysis of cells. In this study, for capture and release of cancer cells we designed the peptide cleavable by collagenase type IV, which has no target molecule in cells. Our system will be useful for further CTC analysis and might lead to more accurate cancer diagnosis.

Highly efficient isolation and release of circulating tumor cells based on size-dependent filtration and degradable ZnO nanorods substrate in a wedge-shaped microfluidic chip

Circulating tumor cells (CTCs) have been regarded as the major cause of metastasis, holding significant insights for tumor diagnosis and treatment. Although many efforts have been made to develop methods for CTC isolation and release in microfluidic system, it remains significant challenges to realize highly efficient isolation and gentle release of CTCs for further cellular and bio-molecular analyses. In this study, we demonstrate a novel method for CTC isolation and release using a simple wedge-shaped microfluidic chip embedding degradable znic oxide nanorods (ZnNRs) substrate. By integrating size-dependent filtration with degradable nanostructured substrate, the capture efficiencies over 87.5% were achieved for SKBR3, PC3, HepG2 and A549 cancer cells spiked in healthy blood sample with the flow rate of 100 μL min^-1. By dissolving ZnNRs substrate with an extremely low concentration of phosphoric acid (12.5 mM), up to 85.6% of the captured SKBR3 cells were released after reverse injection with flow rate of 100 μL min^-1 for 15 min, which exhibited around 73.6% cell viability within 1 h after release to around 93.9% after re-cultured for 3 days. It is conceivable that our microfluidic device has great potentials in carrying on cell-based biomedical studies and guiding individualized treatment in the future.

Multifunctional Nanofibers for Specific Purification and Release of CTCs

Recovering pure and viable circulating tumor cells (CTCs) from blood has been a challenging task for molecular characterization and functional analysis, which has attracted wide attention these days. Herein, we fabricate a thermoresponsive chitosan nanofiber substrate to effectively capture, purify, and release the target cancer cells, assisted by PNIPAAm brushes and DNA hybridization. The PNIPAAm brushes are designed to enable WBCs to detach from aptamer-PNIPAAm-chitosan-nanofiber (aptamer-P-CNFs) surfaces during the conformational transition. Meanwhile these specific captured CTCs are retained at a high purity. Moreover, effective and intact release of CTCs from the substrates without any foreign agents is realized by complementary sequences efficiently hybridizing with aptamers, and the specific cell release makes CTCs further purified. The present work provides a new strategy in the design of biointerface for recovering target CTCs from whole blood samples with high purity.

Aptamer-functionalized nano/micro-materials for clinical diagnosis: isolation, release and bioanalysis of circulating tumor cells

Detection of rare circulating tumor cells (CTCs) in peripheral blood is a challenging, but necessary, task in order to diagnose early onset of metastatic cancer and to monitor treatment efficacy. Over the last decade, step-up produced aptamers have attracted great attention in clinical diagnosis. They have offered great promise for a broader range of cell-specific recognition and isolation. In particular, aptamer-functionalized magnetic particles for selective extraction of target CTCs have shown reduced damage to cells and relatively simple operation. Also, efforts to develop aptamer-functionalized microchannel/microstructures able to efficiently isolate target CTCs are continuing, and these efforts have brought more advanced geometrically designed substrates. Various aptamer-mediated cell release techniques are being developed to enable subsequent biological studies. This article reviews some of these advances in aptamer-functionalized nano/micro-materials for CTCs isolation and methods for releasing captured CTCs from aptamer-functionalized surfaces. Biological studies of CTCs after release are also discussed.

Rhipsalis (Cactaceae)-like Hierarchical Structure Based Microfluidic Chip for Highly Efficient Isolation of Rare Cancer Cells

The circulating tumor cells (CTCs), originating from the primary tumor, play a vital role in cancer diagnosis, prognosis, disease monitoring, and precise therapy. However, the CTCs are extremely rare in the peripheral bloodstream and hard to be isolated. To overcome current limitations associated with CTC capture and analysis, the strategy incorporating nanostructures with microfluidic devices receives wide attention. Here, we demonstrated a three-dimensional microfluidic device (Rm-chip) for capturing cancer cells with high efficiency by integrating a novel hierarchical structure, the "Rhipsalis (Cactaceae)"-like micropillar array, into the Rm-chip. The PDMS micropillar array was fabricated by soft-lithography and rapid prototyping method, which was then conformally plated with a thin gold layer through electroless plating. EpCAM antibody was modified onto the surface of the micropillars through the thiol-oligonucleotide linkers in order to release captured cancer cells by DNase I treatment. The antibody-functionalized device achieved an average capture efficiency of 88% in PBS and 83.7% in whole blood samples. We believe the Rm-chip provided a convenient, economical, and versatile approach for cell analysis with wide potential applications.

Smart Thin Hydrogel Coatings Harnessing Hydrophobicity and Topography to Capture and Release Cancer Cells

Smart thin hydrogel coatings are fabricated to capture and release targeted cancer cells by simultaneously tuning surface hydrophobicity and topography. At physiological temperature, the targeted cancer cells are captured on the hydrophobic and wrinkled coating surface. At room temperature, the captured cells are released from the hydrophilic and smooth coating surface.

Aptamer-Mediated Transparent-Biocompatible Nanostructured Surfaces for Hepotocellular Circulating Tumor Cells Enrichment

Circulating tumor cells (CTCs) have been considered as the origin of cancer metastasis. Thus, detection of CTCs in peripheral blood is of great value in different types of solid tumors. However, owing to extremely low abundance of CTCs, detection of them has been technically challenging. To establish a simple and efficient method for CTCs detection in patients with hepatocellular carcinoma (HCC), we applied biocompatible and transparent HA/CTS (Hydroxyapatite/chitosan) nanofilm to achieve enhanced topographic interactions with nanoscale cellular surface components, and we used sLex-AP (aptamer for carbohydrate sialyl Lewis X) to coat onto HA/CTS nanofilm for efficient capture of HCC CTCs, these two functional components combined to form our CTC-^BioTChip platform. Using this platform, we realized HCC CTCs' capture and identification, the average recovery rate was 61.6% or more at each spiking level. Importantly, our platform identified CTCs (2±2 per 2 mL) in 25 of 42 (59.5%) HCC patients. Moreover, both the positivity rate and the number of detected CTCs were significantly correlated with tumor size, portal vein tumor thrombus, and the TNM (tumor-node-metastasis) stage. In summary, our CTC-^BioTChip platform provides a new method allowing for simple but efficient detection of CTCs in HCC patients, and it holds potential of clinically usefulness in monitoring HCC prognosis and guiding individualized treatment in the future.

Liquid Biopsy of Hepatocellular Carcinoma: Circulating Tumor-Derived Biomarkers

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related death worldwide due to latent liver disease, late diagnosis, and nonresponse to systemic treatments. Till now, surgical and/or biopsy specimens are still generally used as a gold standard by the clinicians for clinical decision-making. However, apart from their invasive characteristics, tumor biopsy only mirrors a single spot of the tumor, failing to reflect current cancer dynamics and progression. Therefore, it is imperative to develop new diagnostic strategies with significant effectiveness and reliability to monitor high-risk populations and detect HCC at an early stage. In the past decade, the potent utilities of “liquid biopsy” have attracted intense concern and were developed to evaluate cancer progression in several clinical trials. “Liquid biopsies” represent a series of noninvasive tests that detect cancer byproducts easily accessible in peripheral blood, mainly including circulating tumor cells (CTCs) and cell-free nucleic acids (cfNAs) that are shed into the blood from the tumor sites. In this review, we focus on the recent developments in the field of “liquid biopsy” as well as the diagnostic and prognostic significance of CTCs and cfNAs in HCC patients.

Lactose-Functionalized Gold Nanorods for Sensitive and Rapid Serological Diagnosis of Cancer

Timely and accurate diagnosis of cancer is crucial to cancer treatment. However, serological diagnosis of cancer still faces great challenge because the conventional methodology based on the enzyme-linked immune sorbent assay (ELISA) is costly, time-consuming, and complicated, involving multiple steps. Herein, lactose-functionalized gold nanorods (Lac-GNRs) are fabricated as efficient biosensors to detect cancerous conditions based on the unique surface plasmon resonance properties of GNRs and high specificity of lactose to the galectin-1 cancer biomarker. A trace concentration of galectin-1 as small as 10(-13) M can be detected by Lac-GNRs. The comparative study among BSA, galectin-3, and galectin-1 demonstrates the good specificity of Lac-GNRs to galectin-1 either in aqueous solutions or in the complex and heterogeneous serum specimens. Clinical tests show that the Lac-GNRs biosensors can readily distinguish the serums of cancer patients from those of healthy persons simply by using a microplate reader or even direct visual observation. The Lac-GNRs biosensing platform is highly efficient and easy to use and have great potential in rapid screening of cancer patients.