Enzymatic cleavage of uracil-containing single-stranded DNA linkers for the efficient release of affinity-selected circulating tumor cells

Exploiting epoxy-rich poly(ethylene glycol) films for highly selective ssDNA sensing via electrochemical impedance spectroscopy

This study introduces an alternative approach to immobilize thiolated single-stranded DNA (ssDNA) for the DNA sensing. In contrast to the standard, monomolecular assembly of such moieties on gold substrate, over the thiolate-gold anchors, we propose to use bioinert, porous polyethylene glycol (PEG) films as a 3D template for ssDNA immobilization. The latter process relies on the reaction between the thiol group of the respectively decorated ssDNA and the epoxy groups in the epoxy-rich PEG matrix. The immobilization process and subsequent hybridization ability of the resulting sensing assembly were monitored using cyclic voltammetry and electrochemical impedance spectroscopy, with the latter tool proving itself as the most suitable transduction technique. Electrochemical data confirmed the successful immobilization of thiol-decorated ssDNA probes into the PEG matrix over the thiol-epoxy linkage as well as high hybridization efficiency, selectivity, and sensitivity of the resulting DNA sensor. Whereas this sensor was equivalent to the direct ssDNA assembly in terms of the efficiency, it exhibited a better selectivity and bioinert properties in view of the bioinert character of the PEG matrix. The above findings place PEG films as a promising platform for highly selective ssDNA sensing, leveraging their flexible chemistry, 3D character, and bioinert properties.

In-plane Extended Nano-coulter Counter (XnCC) for the Label-free Electrical Detection of Biological Particles

We report an in-plane extended nanopore Coulter counter (XnCC) chip fabricated in a thermoplastic via imprinting. The fabrication of the sensor utilized both photolithography and focused ion beam milling to make the microfluidic network and the in-plane pore sensor, respectively, in Si from which UV resin stamps were generated followed by thermal imprinting to produce the final device in the appropriate plastic (cyclic olefin polymer, COP). As an example of the utility of this in-plane extended nanopore sensor, we enumerated SARS-CoV-2 viral particles (VPs) affinity-selected from saliva and extracellular vesicles (EVs) affinity-selected from plasma samples secured from mouse models exposed to different ionizing radiation doses.

Microfluidic Approaches for Affinity-Based Exosome Separation

As a subspecies of extracellular vesicles (EVs), exosomes have provided promising results in diagnostic and theranostic applications in recent years. The nanometer-sized exosomes can be extracted by liquid biopsy from almost all body fluids, making them especially suitable for mainly non-invasive point-of-care (POC) applications. To achieve this, exosomes must first be separated from the respective biofluid. Impurities with similar properties, heterogeneity of exosome characteristics, and time-related biofouling complicate the separation. This practical review presents the state-of-the-art methods available for the separation of exosomes. Furthermore, it is shown how new separation methods can be developed. A particular focus lies on the fabrication and design of microfluidic devices using highly selective affinity separation. Due to their compactness, quick analysis time and portable form factor, these microfluidic devices are particularly suitable to deliver fast and reliable results for POC applications. For these devices, new manufacturing methods (e.g., laminating, replica molding and 3D printing) that use low-cost materials and do not require clean rooms are presented. Additionally, special flow routes and patterns that increase contact surfaces, as well as residence time, and thus improve affinity purification are displayed. Finally, various analyses are shown that can be used to evaluate the separation results of a newly developed device. Overall, this review paper provides a toolbox for developing new microfluidic affinity devices for exosome separation.

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.

Affinity enrichment of extracellular vesicles from plasma reveals mRNA changes associated with acute ischemic stroke

Currently there is no in vitro diagnostic test for acute ischemic stroke (AIS), yet rapid diagnosis is crucial for effective thrombolytic treatment. We previously demonstrated the utility of CD8(+) T-cells’ mRNA expression for AIS detection; however extracellular vesicles (EVs) were not evaluated as a source of mRNA for AIS testing. We now report a microfluidic device for the rapid and efficient affinity-enrichment of CD8(+) EVs and subsequent EV’s mRNA analysis using droplet digital PCR (ddPCR). The microfluidic device contains a dense array of micropillars modified with anti-CD8α monoclonal antibodies that enriched 158 ± 10 nm sized EVs at 4.3 ± 2.1 × 10⁹ particles/100 µL of plasma. Analysis of mRNA from CD8(+) EVs and their parental T-cells revealed correlation in the expression for AIS-specific genes in both cell lines and healthy donors. In a blinded study, 80% test positivity for AIS patients and controls was revealed with a total analysis time of 3.7 h.

Wijerathne et al develop an approach to quantify mRNA amounts in extracellular vesicles (EVs) from plasma using a microfluidics device to enrich EVs. They show this method allows for the correlation of specific mRNAs with acute ischemic stroke pointing towards potential clinical use.

Visible photorelease of liquid biopsy markers following microfluidic affinity-enrichment

We detail a heterobifunctional, 7-aminocoumarin photocleavable (PC) linker with unique properties to covalently attach Abs to surfaces and subsequently release them with visible light (400-450 nm). The PC linker allowed rapid (2 min) and efficient (>90%) release of CTCs and EVs without damaging their molecular cargo.

Label-free counting of affinity-enriched circulating tumor cells (CTCs) using a thermoplastic micro-Coulter counter (μCC)

Coulter counters are used for counting particles and biological cells. Most Coulter counters are designed to analyze a sample without the ability to pre-process the sample prior to counting. For the analysis of rare cells, such as circulating tumor cells (CTCs), it is not uncommon to require enrichment before counting due to the modest throughput of μCCs and the high abundance of interfering cells, such as blood cells. We report a microfluidic-based Coulter Counter (μCC) fabricated using simple, low-cost techniques for counting rare cells that can be interfaced to sample pre- and/or post-processing units. In the current work, a microfluidic device for the affinity-based enrichment of CTCs from whole blood into a relatively small volume of ∼10 μL was interfaced to the μCC to allow for exhaustive counting of single CTCs following release of the CTCs from the enrichment chip. When integrated to the CTC affinity enrichment chip, the μCC could count the CTCs without loss and the cells could be collected for downstream molecular profiling or culturing if required. The μCC sensor counting efficiency was >93% and inter-chip variability was ∼1%.

Godwin A, L. Hupert M, A. Witek M, A. Soper S. Microfluidic Device for On-Chip Immunophenotyping and Cytogenetic Analysis of Rare Biological Cells

The role of circulating plasma cells (CPCs) and circulating leukemic cells (CLCs) as biomarkers for several blood cancers, such as multiple myeloma and leukemia, respectively, have recently been reported. These markers can be attractive due to the minimally invasive nature of their acquisition through a blood draw (i.e., liquid biopsy), negating the need for painful bone marrow biopsies. CPCs or CLCs can be used for cellular/molecular analyses as well, such as immunophenotyping or fluorescence in situ hybridization (FISH). FISH, which is typically carried out on slides involving complex workflows, becomes problematic when operating on CLCs or CPCs due to their relatively modest numbers. Here, we present a microfluidic device for characterizing CPCs and CLCs using immunofluorescence or FISH that have been enriched from peripheral blood using a different microfluidic device. The microfluidic possessed an array of cross-channels (2-4 µm in depth and width) that interconnected a series of input and output fluidic channels. Placing a cover plate over the device formed microtraps, the size of which was defined by the width and depth of the cross-channels. This microfluidic chip allowed for automation of immunofluorescence and FISH, requiring the use of small volumes of reagents, such as antibodies and probes, as compared to slide-based immunophenotyping and FISH. In addition, the device could secure FISH results in <4 h compared to 2-3 days for conventional FISH.

Circulating Tumor Cell Detection In Epithelial Ovarian Cancer Using Dual-Component Antibodies Targeting EpCAM And FRα

Purpose

Circulating tumor cell (CTC) detection methods based on epithelial cell adhesion molecule (EpCAM) have low detection rates in epithelial ovarian cancer (EOC). Meanwhile, folate receptor alpha (FRα) has high expression in EOC cells. We explored the feasibility of combining FRα and EpCAM as CTC capture targets in EOC.

Patients and methods

EpCAM and FRα antibodies were linked to magnetic nanospheres (MNs) using the principle of carbodiimide chemistry. Blood samples from healthy donor spiked with A2780 ovarian cancer cells were used for detecting the capture rate. Ninety-five blood samples from 30 patients with EOC were used for comparing the positive rate of detection when using anti-EpCAM-MNs alone with that when using combination of anti-EpCAM-MNs and anti-FRα-MNs. Samples from 28 patients initially diagnosed with EOC and 20 patients with ovarian benign disease were used for evaluating the sensitivity and specificity of combination of anti-EpCAM-MNs and anti-FRα-MNs.

Results

Regression analysis between the number of recovered and that of spiked A2780 cells revealed y_EpCAM = 0.535x (R² = 0.99), y_FRα = 0.901x (R² = 0.99), and y_EpCAM+FRα = 0.928x (R² = 0.99). In mixtures of A2780 and MCF7 cells, the capture rate was 92% using the combination of anti-EpCAM-MNs and anti-FRα-MNs, exceeding the rate when using anti-EpCAM-MNs or anti-FRα-MNs alone by approximately 20% (P < 0.01). The combination of anti-EpCAM-MNs and anti-FRα-MNs showed a significantly increased positive rate of CTC detection in EOC patients compared with anti-EpCAM-MNs alone (χ² = 14.45, P < 0.001). Sensitivity values were 0.536 and 0.75 and specificity values were 0.9 and 0.85 when using anti-EpCAM-MNs alone and when using the combination of anti-EpCAM-MNs and anti-FRα-MNs, respectively.

Conclusion

The combination of FRα and EpCAM is feasible as a CTC capture target of CTC detection in patients with EOC.

Time-Delayed Integration-Spectral Flow Cytometer (TDI-SFC) for Low-Abundance-Cell Immunophenotyping

We describe a unique flow cytometer (TDI-SFC) for the immunophenotyping of low-abundance cells, particularly when cell counts are sample-limited and operationally difficult for analysis by fluorescence microscopy (>100 cells) or multiparameter flow cytometry (MFC, <10 000 cells). TDI-SFC combines the high spectral resolution of spectral flow cytometry (SFC) with a CCD operated in time-delayed integration (TDI) for improved duty cycle and sensitivity. Cells were focused with a 1D-sheathing microfluidic device, and fluorescence emission generated from a 488 nm laser was collected by epi-illumination and dispersed along one axis of a CCD by a spectrograph. Along the other axis, the CCD's shift rate was clocked at a rate that closely matched the cells' velocity through the field of view. This TDI-SFC format allowed the CCD shutter to remain open during signal acquisition, providing a duty cycle ∼100% and assurance that ∼95% cells were interrogated. We used fluorescent beads to optimize synchronization of TDI clocking with the sheathed-cell velocity and to improve sensitivity via the excitation intensity, epi-illumination numerical aperture, and integration time. TDI achieved integrated signals of 106 counts at a signal-to-noise ratio (SNR) of 610 for beads corresponding to a load of 4 × 105 antibodies. We also evaluated multiplexing capabilities by spectral deconvolution and undertook a proof-of-concept application to immunophenotype low-abundance cells; the demonstration consisted of immunophenotyping a model cell line, in this case SUP-B15 cells representing B-cell acute lymphoblastic leukemia (B-ALL). The B-ALL cell line was stained against a leukemic marker (terminal deoxynucleotidyl transferase, TdT), and we successfully used spectral unmixing to discriminate TdT(+) cells from TdT(-) cells even at low cell counts (∼100 cells). The TDI-SFC could potentially be used in any application requiring the immunophenotyping of low-abundance cells, such as in monitoring measurable residual disease in acute leukemias following affinity enrichment of circulating leukemia cells from peripheral blood.

Microfluidic technologies for circulating tumor cell isolation

Metastasis is the main cause of tumor-related death, and the dispersal of tumor cells through the circulatory system is a critical step in the metastatic process. Early detection and analysis of circulating tumor cells (CTCs) is therefore important for early diagnosis, prognosis, and effective treatment of cancer, enabling favorable clinical outcomes in cancer patients. Accurate and reliable methods for isolating and detecting CTCs are necessary to obtain this clinical information. Over the past two decades, microfluidic technologies have demonstrated great potential for isolating and detecting CTCs from blood. The present paper reviews current advanced microfluidic technologies for isolating CTCs based on various biological and physical principles, and discusses their fundamental advantages and drawbacks for subsequent cellular and molecular assays. Owing to significant genetic heterogeneity among CTCs, microfluidic technologies for isolating individual CTCs have recently been developed. We discuss these single-cell isolation methods, as well as approaches to overcoming the limitations of current microfluidic CTC isolation technologies. Finally, we provide an overview of future innovative microfluidic platforms.

Immunofunctional photodegradable poly(ethylene glycol) hydrogel surfaces for the capture and release of rare cells

Circulating tumor cells (CTCs) play a central role in cancer metastasis and represent a rich source of data for cancer prognostics and therapeutic guidance. Reliable CTC recovery from whole blood therefore promises a less invasive and more sensitive approach to cancer diagnosis and progression tracking. CTCs, however, are exceedingly rare in whole blood, making their quantitative recovery challenging. Several techniques capable of isolating these rare cells have been introduced and validated, yet most suffer from low CTC purity or viability, both of which are essential to develop a clinically viable CTC isolation platform. To address these limitations, we introduce a patterned, immunofunctional, photodegradable poly(ethylene glycol) (PEG) hydrogel capture surface for the isolation and selective release of rare cell populations. Flat and herringbone capture surfaces were successfully patterned via PDMS micromolding and photopolymerization of photolabile PEG hydrogels. Patterned herringbone surfaces, designed to convectively transport cells to the capture surface, exhibited improved capture density relative to flat surfaces for target cell capture from buffer, buffy coat, and whole blood. Uniquely, captured cells were released for collection by degrading the hydrogel capture surface with either bulk or targeted irradiation with cytocompatible doses of long wavelength UV light. Recovered cells remained viable following capture and release and exhibited similar growth rates as untreated control cells. The implementation of molded photodegradable PEG hydrogels as a CTC capture surface provides a micropatternable, cytocompatible platform that imparts the unique ability to recover pure, viable CTC samples by selectively releasing target cells.

Template-Independent Enzymatic Oligonucleotide Synthesis (TiEOS): Its History, Prospects, and Challenges

There is a growing demand for sustainable methods in research and development, where instead of hazardous chemicals, an aqueous medium is chosen to perform biological reactions. In this Perspective, we examine the history and current methodology of using enzymes to generate artificial single-stranded DNA. By using traditional solid-phase phosphoramidite chemistry as a metric, we also explore criteria for the method of template-independent enzymatic oligonucleotide synthesis (TiEOS). As its key component, we delve into the biology of one of the most enigmatic enzymes, terminal deoxynucleotidyl transferase (TdT). As TdT is found to exponentially increase antigen receptor diversity in the vertebrate immune system by adding nucleotides in a template-free manner, researchers have exploited this function as an alternative to the phosphoramidite synthesis method. Though TdT is currently the preferred enzyme for TiEOS, its random nucleotide incorporation presents a barrier in synthesis automation. Taking a closer look at the TiEOS cycle, particularly the coupling step, we find it is comprised of additions > n+1 and deletions. By tapping into the physical and biochemical properties of TdT, we strive to further elucidate its mercurial behavior and offer ways to better optimize TiEOS for production-grade oligonucleotide synthesis.

Isolation of circulating plasma cells from blood of patients diagnosed with clonal plasma cell disorders using cell selection microfluidics

Blood samples from patients with plasma cell disorders were analysed for the presence of circulating plasma cells (CPCs) using a microfluidic device modified with monoclonal anti-CD138 antibodies. CPCs were immuno-phenotyped using a CD38/CD56/CD45 panel and identified in 78% of patients with monoclonal gammopathy of undetermined significance (MGUS), all patients with smouldering and symptomatic multiple myeloma (MM), and none in the controls. The burden of CPCs was higher in patients with symptomatic MM compared with MGUS and smouldering MM (p < 0.05). FISH analysis revealed the presence of chromosome 13 deletions in CPCs that correlated with bone marrow results. Point mutations in KRAS were identified, including different mutations from sub-clones derived from the same patient. The microfluidic assay represents a highly sensitive method for enumerating CPCs and allows for the cytogenetic and molecular characterization of CPCs.

Combined use of EpCAM and FRα enables the high-efficiency capture of circulating tumor cells in non-small cell lung cancer

Circulating tumor cells (CTCs) provide a new approach for auxiliary diagnosis, therapeutic effect evaluation, and prognosis prediction for cancer patients. The epithelial cell adhesion molecule (EpCAM)-based separation method (CellSearch) showed good clinical use in multiple types of cancer. Nevertheless, some non-small cell lung cancer (NSCLC) tumor cells have a lower expression of EpCAM and are less frequently detected by CellSearch. Here, we present a highly sensitive immunomagnetic separation method to capture CTCs based on two cell surface markers for NSCLC, EpCAM and Folate receptor alpha (FRα). Our method has been demonstrated to be more efficient in capturing NSCLC cells (P < 0.01) by enriching three types of CTCs: EpCAM⁺/FRα^-/low, EpCAM^-/low/FRα⁺, and EPCAM⁺/FRα⁺. In 41 NSCLC patients, a significantly higher CTC capture rate (48.78% vs. 73.17%) was obtained, and by using a cutoff value of 0 CTC per 2 ml of blood, the sensitivities were 53.66% and 75.61% and the specificities were 100% and 90% for anti-EpCAM-MNs or a combination of anti-EpCAM-MNs and anti-FRα-MNs, respectively. Compared with the tumor-specific LT-PCR based on FRα, our method can isolate intact FRα⁺ CTCs, and it is advantageous for additional CTC-related downstream analysis. Our results provide a new method to increase the CTC capture efficiency of NSCLC.

Circulating Tumor Cells and Implications of the Epithelial-to-Mesenchymal Transition

The majority of cancer-related deaths result from metastasis, the process by which cancer cells escape the primary tumor site and enter into the blood circulation in order to disseminate to secondary locations throughout the body. Tumor cells found within the circulation are referred to as circulating tumor cells (CTCs), and their detection and enumeration correlate with poor prognosis. The epithelial-to-mesenchymal transition (EMT) is a dynamic process that imparts epithelial cells with mesenchymal-like properties, thus facilitating tumor cell dissemination and contributing to metastasis. However, EMT also results in the downregulation of various epithelial proteins typically utilized by CTC technologies for enrichment and detection of these rare cells, resulting in reduced detection of some CTCs, potentially those with a more metastatic phenotype. In addition to the current clinical role of CTCs as a prognostic biomarker, they also have potential as a predictive biomarker via CTC characterization. However, CTC characterization is complicated by the unknown biological significance of CTCs possessing an EMT-like phenotype, and the ability to capture and understand this CTC subpopulation is an essential step in the utilization of CTCs for patient management. This chapter will review the process of EMT and its contribution to metastasis; discusses current and future clinical applications of CTCs; and describes both traditional and novel methods for CTC enrichment, detection, and characterization with a specific focus on CTCs with an EMT phenotype.

Discrete microfluidics for the isolation of circulating tumor cell subpopulations targeting fibroblast activation protein alpha and epithelial cell adhesion molecule

Circulating tumor cells consist of phenotypically distinct subpopulations that originate from the tumor microenvironment. We report a circulating tumor cell dual selection assay that uses discrete microfluidics to select circulating tumor cell subpopulations from a single blood sample; circulating tumor cells expressing the established marker epithelial cell adhesion molecule and a new marker, fibroblast activation protein alpha, were evaluated. Both circulating tumor cell subpopulations were detected in metastatic ovarian, colorectal, prostate, breast, and pancreatic cancer patients and 90% of the isolated circulating tumor cells did not co-express both antigens. Clinical sensitivities of 100% showed substantial improvement compared to epithelial cell adhesion molecule selection alone. Owing to high purity (>80%) of the selected circulating tumor cells, molecular analysis of both circulating tumor cell subpopulations was carried out in bulk, including next generation sequencing, mutation analysis, and gene expression. Results suggested fibroblast activation protein alpha and epithelial cell adhesion molecule circulating tumor cells are distinct subpopulations and the use of these in concert can provide information needed to navigate through cancer disease management challenges.

Materials and microfluidics: enabling the efficient isolation and analysis of circulating tumour cells

We present a critical review of microfluidic technologies and material effects on the analyses of circulating tumour cells (CTCs) selected from the peripheral blood of cancer patients. CTCs are a minimally invasive source of clinical information that can be used to prognose patient outcome, monitor minimal residual disease, assess tumour resistance to therapeutic agents, and potentially screen individuals for the early diagnosis of cancer. The performance of CTC isolation technologies depends on microfluidic architectures, the underlying principles of isolation, and the choice of materials. We present a critical review of the fundamental principles used in these technologies and discuss their performance. We also give context to how CTC isolation technologies enable downstream analysis of selected CTCs in terms of detecting genetic mutations and gene expression that could be used to gain information that may affect patient outcome.

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.

Chitosan Nanofibers for Specific Capture and Nondestructive Release of CTCs Assisted by pCBMA Brushes

Over the last decade, significant progress has been made to develop sensitive devices for the capture of circulating tumor cells (CTCs) from blood of cancer patients. However, simple capture and counting of CTCs cannot provide effective information for understanding the biology of them. In this work, a functional biointerface is fabricated for specific capture and nondestructive release of CTCs from blood samples. A nanostrucure of porous network based on chitosan nanofibers is fabricated by electrospinning, to mimic the function of extracellular matrices, and then the poly(carboxybetaine methacrylate) (pCBMA) brushes integrating onto nanofiber interface provide the effect of interfacial properties to control nonspecific cell adhesion and the multivalent immobilization of aptamers to induce high efficient and specific CTC capture. Furthermore, a complementary sequence is used to efficiently hybridize with the aptamer to achieve nondestructive release of the captured target cells, assisted by the flexible space provided by pCBMA brushes. This work also shows how nanostructure and the interface molecules regulate the morphology of the captured CTCs, and reveals the importance of the controllable cell morphology on biointerface for an effective nondestructive release of the captured CTCs.

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.

Microfluidics for the detection of minimal residual disease in acute myeloid leukemia patients using circulating leukemic cells selected from blood

We report a highly sensitive microfluidic assay to detect minimal residual disease (MRD) in patients with acute myeloid leukemia (AML) that samples peripheral blood to search for circulating leukemic cells (CLCs). Antibodies immobilized within three separate microfluidic devices affinity-selected CLC subpopulations directly from peripheral blood without requiring pre-processing. The microfluidic devices targeted CD33, CD34, and CD117 cell surface antigens commonly expressed by AML leukemic cells so that each subpopulation's CLC numbers could be tracked to determine the onset of relapse. Staining against aberrant markers (e.g. CD7, CD56) identified low levels (11-2684 mL(-1)) of CLCs. The commonly used platforms for the detection of MRD for AML patients are multi-parameter flow cytometry (MFC), typically from highly invasive bone marrow biopsies, or PCR from blood samples, which is limited to <50% of AML patients. In contrast, the microfluidic assay is a highly sensitive blood test that permits frequent sampling for >90% of all AML patients using the markers selected for this study (selection markers CD33, CD34, CD117 and aberrant markers such as CD7 and CD56). We present data from AML patients after stem cell transplant (SCT) therapy using our assay. We observed high agreement of the microfluidic assay with therapeutic treatment and overall outcome. We could detect MRD at an earlier stage compared to both MFC and PCR directly from peripheral blood, obviating the need for a painful bone marrow biopsy. Using the microfluidic assay, we detected MRD 28 days following one patient's SCT and the onset of relapse at day 57, while PCR from a bone marrow biopsy did not detect MRD until day 85 for the same patient. Earlier detection of MRD in AML post-SCT enabled by peripheral blood sampling using the microfluidic assay we report herein can influence curative clinical decisions for AML patients.

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.