Enhanced tumor cell isolation by a biomimetic combination of E-selectin and anti-EpCAM: implications for the effective separation of circulating tumor cells (CTCs)

Nanoparticles as a novel key driver for the isolation and detection of circulating tumour cells

Circulating tumour cells (CTCs), derived from primary tumours, play a pivotal role in cancer metastasis by migrating into the peripheral bloodstream. These cells are paramount in clinical research, serving as early diagnostic markers for metastatic cancer. Analysing CTC counts and their biomarker characteristics can provide invaluable insights into tumour identification, profiling, and metastatic capabilities. However, the rarity and diverse nature of CTCs in the bloodstream present significant challenges to their isolation and detection, especially in the initial stages of metastasis. Recent advancements in nanotechnology have led to the development of innovative CTC separation and detection methods. This review focuses on applying nanoparticles, nanomaterials, and microfluidic platforms to simplify the isolation and detection of CTCs. The infusion of nanotechnology in this field marks a crucial turning point, enabling the necessary progress to advance CTC research.

Microfluidic pumps for cell sorting

Microfluidic cell sorting has shown promising advantages over traditional bulky cell sorting equipment and has demonstrated wide-reaching applications in biological research and medical diagnostics. The most important characteristics of a microfluidic cell sorter are its throughput, ease of use, and integration of peripheral equipment onto the chip itself. In this review, we discuss the six most common methods for pumping fluid samples in microfluidic cell sorting devices, present their advantages and drawbacks, and discuss notable examples of their use. Syringe pumps are the most commonly used method for fluid actuation in microfluidic devices because they are easily accessible but they are typically too bulky for portable applications, and they may produce unfavorable flow characteristics. Peristaltic pumps, both on- and off-chip, can produce reversible flow but they suffer from pulsatile flow characteristics, which may not be preferable in many scenarios. Gravity-driven pumping, and similarly hydrostatic pumping, require no energy input but generally produce low throughputs. Centrifugal flow is used to sort cells on the basis of size or density but requires a large external rotor to produce centrifugal force. Electroosmotic pumping is appealing because of its compact size but the high voltages required for fluid flow may be incompatible with live cells. Emerging methods with potential for applications in cell sorting are also discussed. In the future, microfluidic cell sorting methods will trend toward highly integrated systems with high throughputs and low sample volume requirements.

Prospective Characterization of Circulating Tumor Cell Kinetics in Patients With Oligometastatic Disease Receiving Definitive Intent Radiation Therapy

PURPOSE

There are currently no predictive molecular biomarkers to identify patients with oligometastatic disease (OMD) who will benefit from definitive-intent radiation therapy (RT). We prospectively characterized circulating tumor cell (CTC) kinetics in patients with OMD undergoing definitive-intent RT.

METHODS

This prospective correlative biomarker study included patients with any solid malignancy ≤5 metastatic sites in ≤3 anatomic organ systems undergoing definitive-intent RT to all disease sites. Circulating tumor cells (CTCs) were captured and enumerated using a biomimetic cell rolling and nanotechnology-based assay functionalized with antibodies against epithelial cell adhesion molecule, against human epidermal growth factor receptor 2, and against epidermal growth factor receptor before and during RT and at follow-up visits up to 2 years post-RT.

RESULTS

We enrolled 43 patients with a median follow-up of 14.3 months. The pretreatment CTC level (cells captured/mL) was not associated with the number of disease sites (median one metastatic site/patient, range 1-5) or metastasis location (bone, brain, visceral) on Wilcoxon signed-rank test, P > .05. Post-RT, 56% of patients received systemic therapy, and 72% of patients experienced subsequent local or systemic progression. For 90% of patients, a CTC level <15 within 130 days post-RT corresponded to a durable control of irradiated lesions. Patients with a favorable versus an unfavorable clearance profile experienced significantly longer progression-free survival after RT (median 13 v 4 months, log-rank test, P = .0011). On logistic regression, CTC level >15 at a given time point was associated with clinical disease progression within the subsequent 6 months (odds ratio 3.31, P = .007). In 26% of patients with disease progression, a CTC level >15 preceded radiographic or clinical progression.

CONCLUSION

CTCs may serve as a biomarker for disease control in OMD and may predict disease progression before standard assessments for patients receiving diverse cancer-directed therapies.

Circulating tumor cell abundance in head and neck squamous cell carcinoma decreases with successful chemoradiation and cetuximab treatment

Head and neck squamous cell carcinoma (HNSCC) is a common and deadly cancer. Circulating tumor cell (CTC) abundance may a valuable, prognostic biomarker in low- and intermediate-risk patients. However, few technologies have demonstrated success in detecting CTCs in these populations. We prospectively collected longitudinal CTC counts from two cohorts of patients receiving treatments at our institution using a highly sensitive device that purifies CTCs using biomimetic cell rolling and dendrimer-conjugated antibodies. In patients with intermediate risk human papillomavirus (HPV)-positive HNSCC, elevated CTC counts were detected in 13 of 14 subjects at screening with a median of 17 CTC/ml (range 0.2-2986.5). A second cohort of non-metastatic, HPV- HNSCC subjects received cetuximab monotherapy followed by surgical resection. In this cohort, all subjects had elevated baseline CTC counts median of 73 CTC/ml (range 5.4-332.9) with statistically significant declines during treatment. Interestingly, two patients with recurrent disease had elevated CTC counts during and following treatment, which also correlated with growth of size and ki67 expression in the primary tumor. The results suggest that our device may be a valuable tool for evaluating the success of less intensive treatment regimens.

Nanotechnology and machine learning enable circulating tumor cells as a reliable biomarker for radiotherapy responses of gastrointestinal cancer patients

A highly sensitive, circulating tumor cell (CTC)-based liquid biopsy was used to monitor gastrointestinal cancer patients during treatment to determine if CTC abundance was predictive of disease recurrence. The approach used a combination of biomimetic cell rolling on recombinant E-selectin and dendrimer-mediated multivalent immunocapture at the nanoscale to purify CTCs from peripheral blood mononuclear cells. Due to the exceptionally high numbers of CTCs captured, a machine learning algorithm approach was developed to efficiently and reliably quantify abundance of immunocytochemically-labeled cells. A convolutional neural network and logistic regression model achieved 82.9% true-positive identification of CTCs with a false positive rate below 0.1% on a validation set. The approach was then used to quantify CTC abundance in peripheral blood samples from 27 subjects before, during, and following treatments. Samples drawn from the patients either prior to receiving radiotherapy or early in chemotherapy had a median 50 CTC ml-1 whole blood (range 0.6-541.6). We found that the CTC counts drawn 3 months post treatment were predictive of disease progression (p = .045). This approach to quantifying CTC abundance may be a clinically impactful in the timely determination of gastrointestinal cancer progression or response to treatment.

Optimizing Immunofunctionalization and Cell Capture on Micromolded Hydrogels via Controlled Oxygen-Inhibited Photopolymerization

With circulating tumor cells (CTCs) playing a critical role in cancer metastasis, the quantitation and characterization of CTCs promise to provide precise diagnostic and prognostic information in service of personalized therapies. However, as CTCs are extremely rare, high yield, high purity strategies are required to target and isolate CTCs from patient samples. Recently, we demonstrated the selective capture of CTCs upon antibody-functionalized polyethylene glycol diacrylate (PEGDA) hydrogels photopolymerized within polydimethylsiloxane (PDMS) microfluidic molds. Isolated CTC purity was subsequently enriched by selectively releasing desired cells from photodegradable hydrogel capture surfaces. However, the fabrication of these acrylate-based hydrogels by photopolymerization is subject to oxygen inhibition, which dramatically affects the physical and chemical properties of hydrogel interfaces formed in proximity to PDMS boundaries. To evaluate how antibody conjugation density and cell capture is impacted by fabrication parameters affected by oxygen inhibition, PEGDA hydrogel features were polymerized within PDMS micromolds under different UV exposure conditions and linker (acrylate-PEG-biotin) concentrations. Predictions of acrylate conversion throughout the hydrogel feature were performed using a 1D reaction-diffusion model that describes oxygen-inhibited photopolymerization. The functional consequences of photopolymerization parameters and solution stoichiometry on CTC capture were experimentally quantified and evaluated. Results show that hydrogel surfaces polymerized under shorter exposure times and with higher linker concentrations display superior functionalization and higher CTC capture efficiency. Conversely, highly cross-linked hydrogel surfaces polymerized under longer exposure times are insensitive to functionalization and display poor capture, regardless of linker concentration. By highlighting the importance of oxygen-inhibited photopolymerization, these findings provide guidelines to design micromolded hydrogels with controlled ligand expression. In addition to enhancing the selective cell capture capacity of immunofunctional hydrogels, the ability to quantifiably design hydrogel interfaces described here will improve the sensitivity of hydrogel biosensors, provide a platform to finely screen cell-matrix interactions, and generally enhance the fidelity of micromolded hydrogel features.

Facile calcium ion-regulated grafting of dense and highly stretched hyaluronan for selective mediation of cancer cells rolling under high-speed flow

The development of materials that selectively mediate the rolling of cancer cells is important for the high-throughput enrichment of high-speed cancer cells. Here we constructed a dense and stretched low molecular weight hyaluronic acid (HA_9.6k)-modified surface to selectively promote the rolling of CD44-high cancer cells. The HA surface (calcium ion-regulated HA_9.6k surface, Ca-rHA) was fabricated via a calcium ion-regulated method, where calcium ion incorporation induced the shrink of HA_9.6k chains to achieve the highest reported grafting density of about 2.73 ± 0.20 × 10⁴ HA chains μm^-2. Upon the removal of calcium ions, the dense HA_9.6k chains switched to a highly stretched conformation. The high density and flexibility of Ca-rHA bearing abundant binding sites enhanced the rolling of CD44-high cancer cells and reduced the velocity of cells from 1389 µm s^-1 to 99 µm s^-1 (7%), comparable to that of the physiological rolling event and outperforming traditional grafting-to HA and E-selectin, without causing phenotypic changes. When processing complex samples under high-speed flow, Ca-rHA selectively mediated the rolling of cancer cells and enriched their ratio to peripheral blood mononuclear cells from 1:1 to 15:1. As the only reported artificial biomaterial capable of selectively mediating the rolling of cancer cells under a physiological high-speed flow, Ca-rHA holds promise in enriching intact cells for downstream analysis in the clinics by encouraging the surface-cell contacts. STATEMENT OF SIGNIFICANCE: The development of materials that selectively mediate the rolling of cancer cells is important for the high-throughput enrichment of cancer cells rolling under high-speed flow, yet is less reported. To selectively promote the rolling of cancer stem cell marker CD44-high cancer cells, a surface with dense and stretched low molecular weight hyaluronic acid (HA_9.6k) was constructed. With Ca²⁺ regulation, HA_9.6k chains shrank to achieve the highest reported grafting density of 2.73 ± 0.20 × 10⁴ chains μm^-2 and further switched to a highly stretched conformation after the removal of Ca²⁺ ions. As the only reported artificial biomaterial capable of selectively mediating the rolling of cancer cells under a physiological high-speed flow, this Ca²⁺-regulated HA_9.6k surface holds promise in enriching intact cells for downstream analysis in the clinics.

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.

NBD-based synthetic probes for sensing small molecules and proteins: design, sensing mechanisms and biological applications

Compounds with a nitrobenzoxadiazole (NBD) skeleton exhibit prominent useful properties including environmental sensitivity, high reactivity toward amines and biothiols (including H2S) accompanied by distinct colorimetric and fluorescent changes, fluorescence-quenching ability, and small size, all of which facilitate biomolecular sensing and self-assembly. Amines are important biological nucleophiles, and the unique activity of NBD ethers with amines has allowed for site-specific protein labelling and for the detection of enzyme activities. Both H2S and biothiols are involved in a wide range of physiological processes in mammals, and misregulation of these small molecules is associated with numerous diseases including cancers. In this review, we focus on NBD-based synthetic probes as advanced chemical tools for biomolecular sensing. Specifically, we discuss the sensing mechanisms and selectivity of the probes, the design strategies for multi-reactable multi-quenching probes, and the associated biological applications of these important constructs. We also highlight self-assembled NBD-based probes and outline future directions for NBD-based chemosensors. We hope that this comprehensive review will facilitate the development of future probes for investigating and understanding different biological processes and aid the development of potential theranostic agents.

Quantitative Assessment of Periodontal Bacteria Using a Cell-Based Immunoassay with Functionalized Quartz Crystal Microbalance

Periodontal disease is an inflammatory disorder that is triggered by bacterial plaque and causes the destruction of the tooth-supporting tissues leading to tooth loss. Several bacteria species, including Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans, are considered to be associated with severe periodontal conditions. In this study, we demonstrated a quartz crystal microbalance (QCM) immunoassay for quantitative assessment of the periodontal bacteria, A. actinomycetemcomitans. An immunosensor was constructed using a self-assembled monolayer of 11-mercaptoundecanoic acid (11-MUA) on the gold surface of a QCM chip. The 11-MUA layer was evaluated using a cyclic voltammetry technique to determine its mass and packing density. Next, a monoclonal antibody was covalently linked to 11-MUA using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide to act as the biorecognition element. The specificity of the monoclonal antibody was confirmed by an enzyme-linked immunosorbent assay. A calibration curve, for the relationship between the frequency shifts and number of bacteria, was used to calculate the number of A. actinomycetemcomitans bacteria in a test sample. Based on a regression equation, the lower detection limit was 800 cells, with a dynamic range up to 2.32 × 106 cells. Thus, the QCM biosensor in this study provides a sensitive and label-free method for quantitative analysis of periodontal bacteria. The method can be used in various biosensing assays for practical application and routine detection of periodontitis pathogens.

Magnetic Particles for CTC Enrichment

Simple Summary

For the enrichment of very rare cells, such as Circulating Tumor Cells (CTCs), immunomagnetic enrichment is frequently used. For this purpose, magnetic nanoparticles (MNPs) coated with specific antibodies directed against cancer cells are used. In this review, we look at the properties such a particle needs to have in order to be used successfully, and describe the different methods used in the production of such a particle as well as the methods for their separation. Additionally, an overview is given of the antibodies that could potentially be used for this purpose.

Abstract

Here, we review the characteristics and synthesis of magnetic nanoparticles (MNPs) and place these in the context of their usage in the immunomagnetic enrichment of Circulating Tumor Cells (CTCs). The importance of the different characteristics is explained, the need for a very specific enrichment is emphasized and different (commercial) magnetic separation techniques are shown. As the specificity of an MNP is in a large part dependent on the antibody coated onto the particle, different strategies in the coupling of specific antibodies as well as an overview of the available antibodies is given.

Bioimprint Mediated Label-Free Isolation of Pancreatic Tumor Cells from a Healthy Peripheral Blood Cell Population

New techniques are required for earlier diagnosis and response to treatment of pancreatic cancer. Here, a label-free approach is reported in which circulating pancreatic tumor cells are isolated from healthy peripheral blood cells via cell bioimprinting technology. The method involves pre-fabrication of pancreatic cell layers and sequential casting of cell surfaces with a series of custom-made resins to produce negative cell imprints. The imprint is functionalized with a combination of polymers to engineer weak attraction to the cells which is further amplified by the increased area of contact with the matching cells. A flow-through bioimprint chip is designed and tested for selectivity toward two pancreatic tumor cell lines, ASPC-1 and Mia-PaCa-2. Healthy human peripheral blood mononuclear cells (PBMCs) are spiked with pancreatic tumor cells at various concentrations. Bioimprints are designed for preferential retention of the matching pancreatic tumor cells and with respect to PBMCs. Tumor bioimprints are capable of capturing and concentrating pancreatic tumor cells from a mixed cell population with increased retention observed with the number of seedings. ASPC-1 bioimprints preferentially retain both types of pancreatic tumor cells. This technology could be relevant for the collection and interrogation of liquid biopsies, early detection, and relapse monitoring of pancreatic cancer patients.

Surface engineering for efficient capture of circulating tumor cells in renal cell carcinoma: From nanoscale analysis to clinical application

Sensitive detection of circulating tumor cells (CTCs) from patients' peripheral blood facilitates on-demand monitoring of tumor progression. However, clinically significant capture of renal cell carcinoma CTCs (RCC-CTCs) remains elusive due to their heterogenous surface receptor expression. Herein, a novel capture platform is developed to detect RCC-CTCs through integration of dendrimer-mediated multivalent binding, a mixture of antibodies, and biomimetic cell rolling. The nanoscale binding kinetics measured using atomic force microscopy reveal that dendrimer-coated surfaces exhibit an order of magnitude enhancement in off-rate kinetics compared to surface without dendrimers, which translated into cell capture improvements by ~60%. Selectin-induced cell rolling facilitates surface recruitment of cancer cells, further improving cancer cell capture by up to 1.7-fold. Lastly, an antibody cocktail targeting four RCC-CTC surface receptors, which included epithelial cell adhesion molecule (EpCAM), carbonic anhydrase IX (CA9), epidermal growth factor receptor (EGFR), and hepatocyte growth factor receptor (c-Met), improves the capture of RCC cells by up to 80%. The optimal surface configuration outperforms the conventional assay solely relying on EpCAM, as demonstrated by detecting significantly more CTCs in patients' samples (9.8 ± 5.1 vs. 1.8 ± 2.0 CTCs mL-1). These results demonstrate that the newly engineered capture platform effectively detects RCC-CTCs for their potential use as tumor biomarkers.

Recent advances in microfluidic technologies for separation of biological cells

Cell separation has always been a key topic in academic research, especially in the fields of medicine and biology, due to its significance in diagnosis and treatment. Accurate, high-throughput and non-invasive separation of individual cells is key to driving the development of biomedicine and cellular biology. In recent years, a series of researches on the use of microfluidic technologies for cell separation have been conducted to solve bio-related problems. Hence, we present here a comprehensive review on the recent developments of microfluidic technologies for cell separation. In this review, we discuss several cell separation methods, mainly including: physical and biochemical method, their working principles as well as their practical applications. We also analyze the advantages and disadvantages of each method in detail. In addition, the current challenges and future prospects of microfluidic-based cell separation were discussed.

A Review on Microdevices for Isolating Circulating Tumor Cells

Cancer metastasis is the primary cause of high mortality of cancer patients. Enumeration of circulating tumor cells (CTCs) in the bloodstream is a very important indicator to estimate the therapeutic outcome in various metastatic cancers. The aim of this article is to review recent developments on the CTC isolation technologies in microdevices. Based on the categories of biochemical and biophysical isolation approaches, a literature review and in-depth discussion will be included to provide an overview of this challenging topic. The current excellent developments suggest promising CTC isolation methods in order to establish a precise indicator of the therapeutic outcome of cancer patients.

A comparative study on EpCAM antibody immobilization on gold surfaces and microfluidic channels for the detection of circulating tumor cells

Detection of circulating tumor cells (CTCs) from the bloodstream holds great importance to diagnose cancer at early stages. However, CTCs being extremely rare in blood makes them difficult to reach. In this paper, we introduced different surface modification techniques for the enrichment and detection of MCF-7 in microfluidic biosensor applications using gold surface and EpCAM antibody. Mainly, two different mechanisms were employed to immobilize the antibodies; covalent bonding and bioaffinity interaction. Self-assembled monolayers (SAMs) formed on the gold surfaces were treated further for the immobilization of the antibody. The bioaffinity-based studies were performed with streptavidin and biotinylated EpCAM over the SAM coated surfaces. The cell attachment events were monitored using fluorescent microscope. Comparisons were made considering the length and functional end of alkanethiols and the positioning of the antibody. Then, these methods were integrated into a microfluidic channel system. Surface characterizations were performed with X-ray Photoelectron Spectroscopy, Atomic Force Microscopy, and contact angle measurements. The selectivity studies were carried out with EpCAM negative K562 leukaemia cell lines and the experiments were repeated for different types of surfaces, such as glass and polymer. Studies showed that long (n>10) and aromatic ring containing alkanethiols lead to better cell capture events compared to shorter ones. Results obtained from the comparisons are of importance for the gold surface-based microfluidic biosensor designs aimed for CTC detection.

Dendrimer-Based Platform for Effective Capture of Tumor Cells after TGFβ1-Induced Epithelial-Mesenchymal Transition

Detection of circulating tumor cells (CTCs) relying on their expression of epithelial cell markers, such as epithelial cell adhesion molecule (EpCAM), has been commonly used. However, this approach unlikely captures CTCs that have undergone the process of epithelial-mesenchymal transition (EMT). In this study, we have induced EMT of in vitro prostate (PCa) and breast cancer (BCa) cell lines by treatment of transforming growth factor β 1 (TGFβ1), a pleiotropic cytokine with transition-regulating activities. We found that the TGFβ1-treated, post-EMT cells exhibited up to a 45% reduction in binding affinity to antibodies against EpCAM (aEpCAM). To overcome this limitation, we designed our capture platform that integrates a unique combination of biomimetic cell rolling, dendrimer-mediated multivalent binding, and antibody cocktails of aEpCAM/aEGFR/aHER-2. Our capture surfaces resulted in up to 98% capture efficiency of post-EMT cells from mixtures of TGFβ1-treated and untreated cancer cells spiked in culture media and human blood. In a clinical pilot study, our CTC device was also able to capture rare CTCs from PCa patients with significantly enhanced capture sensitivity and purity compared to the control surface with aEpCAM only, demonstrating its potential to provide a reliable detection solution for CTCs regardless of their EMT status.

Recent advances in microfluidic methods in cancer liquid biopsy

Early cancer detection, its monitoring, and therapeutical prediction are highly valuable, though extremely challenging targets in oncology. Significant progress has been made recently, resulting in a group of devices and techniques that are now capable of successfully detecting, interpreting, and monitoring cancer biomarkers in body fluids. Precise information about malignancies can be obtained from liquid biopsies by isolating and analyzing circulating tumor cells (CTCs) or nucleic acids, tumor-derived vesicles or proteins, and metabolites. The current work provides a general overview of the latest on-chip technological developments for cancer liquid biopsy. Current challenges for their translation and their application in various clinical settings are discussed. Microfluidic solutions for each set of biomarkers are compared, and a global overview of the major trends and ongoing research challenges is given. A detailed analysis of the microfluidic isolation of CTCs with recent efforts that aimed at increasing purity and capture efficiency is provided as well. Although CTCs have been the focus of a vast microfluidic research effort as the key element for obtaining relevant information, important clinical insights can also be achieved from alternative biomarkers, such as classical protein biomarkers, exosomes, or circulating-free nucleic acids. Finally, while most work has been devoted to the analysis of blood-based biomarkers, we highlight the less explored potential of urine as an ideal source of molecular cancer biomarkers for point-of-care lab-on-chip devices.

Tumor cell capture from blood by flowing across antibody-coated surfaces

The load of circulating tumor cells (CTC) is related to poor outcomes in cancer patients. A sufficient number of these cells would enable a full characterization of the cancer. An approach to probe larger blood volumes, allowing for the detection of more of these very rare CTC, is the use of leukapheresis. Currently available techniques allow only the analysis of a small portion of leukapheresis products. Here, we present a method that uses flow rather than static conditions which allows processing of larger volumes. We evaluated the conditions needed to isolate tumor cells from blood while passing antibody coated surfaces. Results show that our set-up efficiently captures cancer cells from whole blood. Results show that the optimal velocity at which cells are captured from blood is 0.6 mm s-1. Also, it can be concluded that the VU1D9 antibody targeting the EpCAM antigen has very high capture efficiency. When using an antibody that does not capture 100% of all cells, combining multiple antibodies on the capture surface is very beneficial leading to an increase in cell capture and is therefore worthwhile considering in any cancer cell capture methodology.

Regulation of epithelial migration by epithelial cell adhesion molecule requires its Claudin-7 interaction domain

Epithelial cell adhesion molecule (EpCAM) is a glycoprotein on the surface of epithelial cells that is essential for intestinal epithelial integrity and expressed at high levels in many epithelial derived cancers and circulating tumor cells. Here we show the effect of EpCAM levels on migration of Madin-Darby-Canine Kidney (MDCK) epithelial cells. MDCK cells depleted of EpCAM show increased activation of extracellular signal-regulated kinase (ERK) and of myosin, and increased cell spreading and epithelial sheet migration into a gap. In contrast, over-expression of EpCAM inhibits ERK and myosin activation, and slows epithelial sheet migration. Loss of EpCAM is rescued by EpCAM-YFP mutated in the extracellular domain required for cis-dimerization whereas EpCAM-YFP with a mutation that inhibits Claudin-7 interaction cannot rescue increased ERK, myosin activation, and increased migration in EpCAM-depleted cells. In summary, these results indicate that interaction of EpCAM and Claudin-7 at the cell surface negatively regulates epithelial migration by inhibiting ERK and actomyosin contractility.

Multivalent Binding and Biomimetic Cell Rolling Improves the Sensitivity and Specificity of Circulating Tumor Cell Capture

Purpose: We aimed to examine the effects of multivalent binding and biomimetic cell rolling on the sensitivity and specificity of circulating tumor cell (CTC) capture. We also investigated the clinical significance of CTCs and their kinetic profiles in patients with cancer undergoing radiotherapy treatment.Experimental Design: Patients with histologically confirmed primary carcinoma undergoing radiotherapy, with or without chemotherapy, were eligible for enrollment. Peripheral blood was collected prospectively at up to five time points, including before radiotherapy, at the first week, mid-point and final week of treatment, as well as 4 to 12 weeks after completion of radiotherapy. CTC capture was accomplished using a nanotechnology-based assay (CapioCyte) functionalized with aEpCAM, aHER-2, and aEGFR.Results: CapioCyte was able to detect CTCs in all 24 cancer patients enrolled. Multivalent binding via poly(amidoamine) dendrimers further improved capture sensitivity. We also showed that cell rolling effect can improve CTC capture specificity (% of captured cells that are CK+/CD45-/DAPI+) up to 38%. Among the 18 patients with sequential CTC measurements, the median CTC decreased from 113 CTCs/mL before radiotherapy to 32 CTCs/mL at completion of radiotherapy (P = 0.001). CTCs declined throughout radiotherapy in patients with complete clinical and/or radiographic response, in contrast with an elevation in CTCs at mid or post-radiotherapy in the two patients with known pathologic residual disease.Conclusions: Our study demonstrated that multivalent binding and cell rolling can improve the sensitivity and specificity of CTC capture compared with multivalent binding alone, allowing reliable monitoring of CTC changes during and after treatment. Clin Cancer Res; 24(11); 2539-47. ©2018 AACR.

Efficient Capture and High Activity Release of Circulating Tumor Cells by Using TiO2 Nanorod Arrays Coated with Soluble MnO2 Nanoparticles

Effective capture and release of circulating tumor cells (CTCs) with high viability is still a challenge in medical research. We design a novel approach with efficient yield and high cell activity for the capture and release of CTCs. Our platform is based on TiO₂ nanorod arrays coated with transparent MnO₂ nanoparticles. We use hydrothermal synthesis to prepare TiO₂ nanorod arrays, the MnO₂ nanoparticles are fabricated through in situ self-assembly on the substrate to form a monolayer and etched by oxalic acid with low concentration at room temperature. Up to 92.9% of target cells are isolated from the samples using our capture system and the captured cells can be released from the platform, the saturated release efficiency is 89.9%. Employing lower than 2 × 10^-3 M concentration of oxalic acid to dissolve MnO₂, the viability of MCF-7 cancer cells exceed 90%. Such a combination of the two-dimensional and three-dimensional platforms provides a new approach isolate CTCs from patient blood samples.

Functional Diagnostic and Therapeutic Nanoconstructs for Efficient Probing of Circulating Tumor Cells

The circulation of tumor cells in peripheral blood is mostly recognized as a prerequisite for cancer progression or systemic invasion, and it correlates with the pivotal hallmark of malignancies known as metastasis. Multiple detection schemes for circulating tumor cells (CTCs) have emerged as the most discerning criteria for monitoring the outcome of anticancer therapy. Therefore, there has been a tremendous increase in the use of robust nanostructured platforms for observation of these mobile tumor cells through various simultaneous diagnosis and treatment regimens developed from conventional techniques. This review seeks to give detailed information about the nature of CTCs as well as techniques for exploiting specific biomarkers to help monitor cancer via detection, capturing, and analysis of unstable tumor cells. We will further discuss nanobased diagnostic interventions and novel platforms which have recently been developed from versatile nanomaterials such as polymer nanocomposites, metal organic frameworks, bioderived nanomaterials and other physically responsive particles with desirable intrinsic and external properties. Herein, we will also include in vivo nanotheranostic platforms which have received a lot of attention because of their enormous clinical potential. In all, this review sums up the general potential of key promising nanoinspired systems as well as other advanced strategies under research and those in clinical use.

Noncatalytic Endosialidase Enables Surface Capture of Small-Cell Lung Cancer Cells Utilizing Strong Dendrimer-Mediated Enzyme-Glycoprotein Interactions

Enumeration of circulating tumor cells (CTCs) of small-cell lung cancer (SCLC) patients has been shown to predict the disease progress and long-term survival. Most CTC detection methods rely on epithelial surface markers, such as epithelial cell adhesion molecule (EpCAM). However, this marker in SCLC is reported to be often downregulated after a variety of phenotypic changes, which impairs the reliability of EpCAM-based CTC detections. In this regard, the development of an alternative CTC detection method involving different CTC surface markers is in demand. In this study, we evaluated, for the first time to our knowledge, the feasibility of detecting SCLC CTCs using a noncatalytic endosialidase (EndoN Trap, EndoNt). This noncatalytic enzyme was chosen due to its high affinity to polysialic acid (polySia), a cell-surface glycan, that is highly expressed by SCLC tissue. Furthermore, this enzyme-based system was integrated into our dendrimer-mediated CTC capture platform to further enhance the capture efficiency via multivalent binding. We found that the EndoNt-immobilized surfaces could specifically capture polySia-positive SCLC cells and the binding between SCLC cells and EndoNt surfaces was further stabilized by dendrimer-mediated multivalent binding. When compared to the EpCAM-based capture, EndoNt significantly improved the capture efficiency of polySia-positive SCLC cells under flow due to its higher binding affinity (lower dissociation rate constants). These findings suggest that this enzyme-based CTC capture strategy has the potential to be used as a superior alternative to the commonly used EpCAM-based methods, particularly for those types of cancer that overexpress polySia.

Clinical utility of non-EpCAM based circulating tumor cell assays

Methods enabling the isolation, detection, and characterization of circulating tumor cells (CTCs) in blood have clear potential to facilitate precision medicine approaches in patients with cancer, not only for prognostic purposes but also for prediction of the benefits of specific therapies in oncology. However, current CTC assays, which capture CTCs based on expression of epithelial cell adhesion molecule (EpCAM), fail to capture cells from de-differentiated tumors and carcinomas undergoing loss of the epithelial phenotype during the invasion/metastatic process. To address this limitation, many groups are developing non-EpCAM based CTC assays that incorporate nanotechnology to improve test sensitivity for rare but important cells that may otherwise go undetected, and therefore may improve upon clinical utility. In this review, we outline emerging non-EpCAM based CTC assays utilizing nanotechnology approaches for CTC capture or characterization, including dendrimers, magnetic nanoparticles, gold nanoparticles, negative selection chip or software-based on-slide methods, and nano-scale substrates. In addition, we address challenges that remain for the clinical translation of these platforms.

Integration of biomimicry and nanotechnology for significantly improved detection of circulating tumor cells (CTCs)

Circulating tumor cells (CTCs) have received a great deal of scientific and clinical attention as a biomarker for diagnosis and prognosis of many types of cancer. Given their potential significance in clinics, a variety of detection methods, utilizing the recent advances in nanotechnology and microfluidics, have been introduced in an effort of achieving clinically significant detection of CTCs. However, effective detection and isolation of CTCs still remain a tremendous challenge due to their extreme rarity and phenotypic heterogeneity. Among many approaches that are currently under development, this review paper focuses on a unique, promising approach that takes advantages of naturally occurring processes achievable through application of nanotechnology to realize significant improvement in sensitivity and specificity of CTC capture. We provide an overview of successful outcome of this biomimetic CTC capture system in detection of tumor cells from in vitro, in vivo, and clinical pilot studies. We also emphasize the clinical impact of CTCs as biomarkers in cancer diagnosis and predictive prognosis, which provides a cost-effective, minimally invasive method that potentially replaces or supplements existing methods such as imaging technologies and solid tissue biopsy. In addition, their potential prognostic values as treatment guidelines and that ultimately help to realize personalized therapy are discussed.

Epidermal growth factor receptor-targeted immune magnetic liposomes capture circulating colorectal tumor cells efficiently

AIM

To compare the capacity of newly developed epidermal growth factor receptor (EGFR)-targeted immune magnetic liposomes (EILs) vs epithelial cell adhesion molecule (EpCAM) immunomagnetic beads to capture colorectal circulating tumor cells (CTCs).

METHODS

EILs were prepared using a two-step method, and the magnetic and surface characteristics were confirmed. The efficiency of capturing colorectal CTCs as well as the specificity were compared between EILs and EpCAM magnetic beads.

RESULTS

The obtained EILs had a lipid nanoparticle structure similar to cell membrane. Improved binding with cancer cells was seen in EILs compared with the method of coupling nano/microspheres with antibody. The binding increased as the contact time extended. Compared with EpCAM immunomagnetic beads, EILs captured more CTCs in peripheral blood from colorectal cancer patients. The captured cells showed consistency with clinical diagnosis and pathology. Mutation analysis showed same results between captured CTCs and cancer tissues.

CONCLUSION

EGFR antibody-coated magnetic liposomes show high efficiency and specificity in capturing colorectal CTCs.

Analysis of epoxy functionalized layers synthesized by plasma polymerization of allyl glycidyl ether

The deposition of epoxide groups by plasma polymerization opens new horizons for robust and quick immobilization of biomolecules on any type of substrate.

Preferential capture of EpCAM-expressing extracellular vesicles on solid surfaces coated with an aptamer-conjugated zwitterionic polymer

Extracellular vesicles (EVs) collectively represent small vesicles that are secreted from cells and carry biomolecules (e.g., miRNA, lncRNA, mRNA, proteins, lipids, metabolites, etc.) that originate in those cells. Body fluids, such as blood and saliva, include large numbers of EVs, making them potentially a rich source of diagnostic information. However, these EVs are mixtures of vesicles released from diseased tissues as well as from normal cells. This heterogeneous nature therefore blurs the clinical information obtainable from EV-based diagnosis. Here, we synthesized an EpCAM-affinity coating agent, which consists of a peptide aptamer for EpCAM and a zwitterionic MPC polymer, and have shown that this conjugate endowed the surfaces of inorganic materials with the preferential affinity to EpCAM-expressing EVs. This coating agent, designated as EpiVeta, could be useful as a coating for various diagnostic devices to allow concentration of cancer-related EVs from heterogeneous EV mixtures.

Transferrin-navigation Nano Artificial Antibody Fluorescence Recognition of Circulating Tumor Cells

Specific recognition of circulating tumor cells (CTCs) is of great significance for cancer diagnosis and personalized therapy. The antibodies and aptamer are commonly used for recognition of CTCs, but they often suffer from low stability and high cost. Therefore, chemically stable and low-cost artificial recognition elements are still highly demanded. Herein, we prepared nano artificial antibody based on molecular imprinting and applied for fluorescence recognition of CTCs. Surface imprinting was employed to construct a transferrin (TRA)-imprinted layer on the surface of rhodamine doped silica nanoparticles. Take advantage of the specific interaction between TRA and TRA receptor (overexpressed on cancer cells), the as-prepared TRA-imprinted artificial antibody was allowed for specific targeting cancer cells mediated by TRA. And the average recognition efficiency of the artificial antibody for the cancer cells was 88% through flow cytometry. Finally, the nano artificial antibody was successfully applied to specific identify mimetic CTCs, under the same conditions, the recognition ability of artificial antibody for CTCs was 8 times higher than the white blood cells.

Microfluidic devices to enrich and isolate circulating tumor cells

Given the potential clinical impact of circulating tumor cells (CTCs) in blood as a clinical biomarker for the diagnosis and prognosis of various cancers, a myriad of detection methods for CTCs have been recently introduced. Among those, a series of microfluidic devices are particularly promising as they uniquely offer micro-scale analytical systems that are highlighted by low consumption of samples and reagents, high flexibility to accommodate other cutting-edge technologies, precise and well-defined flow behaviors, and automation capability, presenting significant advantages over conventional larger scale systems. In this review, we highlight the advantages of microfluidic devices and their potential for translation into CTC detection methods, categorized by miniaturization of bench-top analytical instruments, integration capability with nanotechnologies, and in situ or sequential analysis of captured CTCs. This review provides a comprehensive overview of recent advances in CTC detection achieved through application of microfluidic devices and the challenges that these promising technologies must overcome to be clinically impactful.

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 Self-Cleaning TiO2 Nanosisal-like Coating toward Disposing Nanobiochips of Cancer Detection

The advanced nanobiochips have been widely employed in diagnosing some high incidence of diseases because of their portable, low-cost, and highly sensitive features. However, the subsequent disposal of these wastes remains unexposed, probably giving rise to serious environmental pollution and health risks similar to traditional biomedical waste. Here, we have presented a TiO2 nanosisal-like coating for disposing nanobiochip waste via the photoresponsive self-cleaning features of the nanobiochip, demonstrated by the nanochips of cancer detection. Moreover, the high specificity and sensitivity of nanochips can be maintained by integrating unique nanostructured coatings (i.e., nanosisal-like coating) with specific recognition molecules (i.e., anti-EpCAM). Therefore, this study will provide a promising strategy for the design and management of practical nanobiodevices, thereby eliminating the old path "pollute first, clean up later".

Construction of carbon nanotube based nanoarchitectures for selective impedimetric detection of cancer cells in whole blood

A carbon nanotube (CNT) based nanoarchitecture is developed for rapid, sensitive and specific detection of cancer cells by using real time electrical impedance sensing. The sensor is constructed with carbon nanotube (CNT) multilayers and EpCAM (epithelial cell adhesion molecule) antibodies, which are assembled on an indium tin oxide (ITO) electrode surface. The binding of tumor cells to EpCAM antibodies causes increase of the electron-transfer resistance. The electrochemical impedance of the prepared biosensors is linear with the logarithm of concentration of the liver cancer cell line (HepG2) within the concentration range of 10 to 10(5) cells per mL. The detection limit for HepG2 cells is 5 cells per mL. The proposed impedimetric sensing devices allow for sensitive and specific detection of cancer cells in whole-blood samples without any sample pretreatment steps.

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.

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.

A Microfluidic Method for the Selection of Undifferentiated Human Embryonic Stem Cells and in Situ Analysis

Conventional cell-sorting methods such as fluorescence-activated cell sorting (FACS) or magnetic-activated cell sorting (MACS) can suffer from certain shortcomings such as lengthy sample preparation time, cell modification through antibody labeling, and cell damage due to exposure to high shear forces or to attachment of superparamagnetic Microbeads. In light of these drawbacks, we have recently developed a label-free, microfluidic platform that can not only select cells with minimal sample preparation but also enable analysis of cells in situ. We demonstrate the utility of our platform by successfully isolating undifferentiated human embryonic stem cells (hESCs) from a heterogeneous population based on the undifferentiated stem-cell marker SSEA-4. Importantly, we show that, in contrast to MACS or FACS, cells isolated by our method have very high viability (~90%). Overall, our platform technology could likely be applied to other cell types beyond hESCs and to a variety of heterogeneous cell populations in order to select and analyze cells of interest.

Ex vivo and in vivo capture and deactivation of circulating tumor cells by dual-antibody-coated nanomaterials

Circulating tumor cells (CTCs) have been detected by us and others in cancer patient blood. However, little is known about how to specifically capture and deactivate CTCs in vivo, which may lead to successful metastasis prevention in asymptomatic cancer survivors after surgery. We hypothesize that the dual antibody conjugates may have the advantage of capturing CTCs specifically over their single antibody counterparts. Here we show that the surface-functionalized dendrimers can be sequentially coated with two antibodies directed to surface biomarkers (EpCAM and Slex) of human colorectal CTCs. The dual antibody-coated dendrimers exhibit a significantly enhanced specificity in capturing CTCs in the presence of interfering blood cells, and in both eight-patient bloods and nude mice administered with the labeled CTCs in comparison to their single antibody-coated counterparts. The dual antibody-coated conjugates down-regulate the captured CTCs. This study provides the first conceptual evidence that two antibodies can be biocompatibly conjugated to a nanomaterial to capture and down-regulate CTCs in vivo with the enhanced specificity.

Tissue factor-expressing tumor cells can bind to immobilized recombinant tissue factor pathway inhibitor under static and shear conditions in vitro

Mammary tumors and malignant breast cancer cell lines over-express the coagulation factor, tissue factor (TF). High expression of TF is associated with a poor prognosis in breast cancer. Tissue factor pathway inhibitor (TFPI), the endogenous inhibitor of TF, is constitutively expressed on the endothelium. We hypothesized that TF-expressing tumor cells can bind to immobilized recombinant TFPI, leading to arrest of the tumor cells under shear in vitro. We evaluated the adhesion of breast cancer cells to immobilized TFPI under static and shear conditions (0.35 – 1.3 dyn/cm²). We found that high-TF-expressing breast cancer cells, MDA-MB-231 (with a TF density of 460,000/cell), but not low TF-expressing MCF-7 (with a TF density of 1,400/cell), adhered to recombinant TFPI, under static and shear conditions. Adhesion of MDA-MB-231 cells to TFPI required activated factor VII (FVIIa), but not FX, and was inhibited by a factor VIIa-blocking anti-TF antibody. Under shear, adhesion to TFPI was dependent on the TFPI-coating concentration, FVIIa concentration and shear stress, with no observed adhesion at shear stresses greater than 1.0 dyn/cm². This is the first study showing that TF-expressing tumor cells can be captured by immobilized TFPI, a ligand constitutively expressed on the endothelium, under low shear in vitro. Based on our results, we hypothesize that TFPI could be a novel ligand mediating the arrest of TF-expressing tumor cells in high TFPI-expressing vessels under conditions of low shear during metastasis.

Exploring cancer metastasis prevention strategy: interrupting adhesion of cancer cells to vascular endothelia of potential metastatic tissues by antibody-coated nanomaterial

Background

Cancer metastasis caused by circulating tumor cells (CTCs) accounts for 90% cancer-related death worldwide. Blocking the circulation of CTCs in bloodstream and their hetero-adhesion to vascular endothelia of the distant metastatic organs may prevent cancer metastasis. Nanomaterial-based intervention with adhesion between CTCs and endothelia has not been reported. Driven by the novel idea that multivalent conjugation of EpCAM and Slex antibodies to dendrimer surface may enhance the capacity and specificity of the nanomaterial conjugates for capturing and down-regulating colorectal CTCs, we conjugated the dendrimer nanomaterial with the EpCAM and Slex antibodies, and examined the capacity of the dual antibody-coated nanomaterial for their roles in interrupting CTCs-related cancer metastasis.

Results

The antibody-coated nanomaterial was synthesized and characterized. The conjugates specifically bound and captured colon cancer cells SW620. The conjugate inhibited the cells’ viability and their adhesion to fibronectin (Fn)-coated substrate or human umbilical vein endothelial cells (HUVECs) in a concentration-dependent manner. In comparison with SW480 and LoVo cell lines, the activity and adhesion of SW620 to Fn-coated substrate and HUVECs were more specifically inhibited by the dual antibody conjugate because of the higher levels of EpCAM and Slex on SW620 cell surface. The hetero-adhesion between SW620 and Fn-coated substrate, or HUVECs was inhibited by about 60-70%. The dual conjugate showed the inhibition capacity more significant than its corresponding single antibody conjugates.

Conclusions

The present study provides the new evidence that coating nanomaterials with more than one antibody against CTCs may effectively interfere with the interaction between SW620 and HUVECs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12951-015-0072-x) contains supplementary material, which is available to authorized users.

Biomimetic receptors for bioanalyte detection by quartz crystal microbalances - from molecules to cells

A universal label-free detection of bioanalytes can be performed with biomimetic quartz crystal microbalance (QCM) coatings prepared by imprinting strategies. Bulk imprinting was used to detect the endocrine disrupting chemicals (EDCs) known as estradiols. The estrogen 17β-estradiol is one of the most potent EDCs, even at very low concentrations. A highly sensitive, selective and robust QCM sensor was fabricated for real time monitoring of 17β-estradiol in water samples by using molecular imprinted polyurethane. Optimization of porogen (pyrene) and cross-linker (phloroglucinol) levels leads to improved sensitivity, selectivity and response time of the estradiol sensor. Surface imprinting of polyurethane as sensor coating also allowed us to generate interaction sites for the selective recognition of bacteria, even in a very complex mixture of interfering compounds, while they were growing from their spores in nutrient solution. A double molecular imprinting approach was followed to transfer the geometrical features of natural bacteria onto the synthetic polymer to generate biomimetic bacteria. The use of biomimetic bacteria as template makes it possible to prepare multiple sensor coatings with similar sensitivity and selectivity. Thus, cell typing, e.g., differentiation of bacteria strains, bacteria growth profile and extent of their nutrition, can be monitored by biomimetic mass sensors. Obviously, this leads to controlled cell growth in bioreactors.

Nanotechnology applications in diagnosis and treatment of metastasis

The lethality of solid tumors is in large part dependent on their ability to metastasize through hematologic and lymphatic transport pathways. The dissemination of cancer cells from the primary tumor to undergo transport, their ability to survive in transit and then to subsequently form metastatic colonies, is facilitated by a complex concert of signaling pathways and cell–cell and cell–matrix interactions. Elucidating these mechanistic components is highly valuable to guide the development of technologies for efficiently detecting and treating metastasis. To this end, in recent years nanotechnology approaches have provided several unique detection, characterization and treatment strategies. The current article will review these approaches to discuss their promise and challenges, specifically in metastatic cancer, above and beyond the usual nanomedicine applications in cancer therapy.