Effective reduction of non-specific binding of blood cells in a microfluidic chip for isolation of rare cancer cells

Antifouling modification for high-performance isolation of circulating tumor cells

Circulating tumor cells (CTCs), which shed from solid tumor tissue into blood circulatory system, have attracted wide attention as a biomarker in the early diagnosis and prognosis of cancer. Given their potential significance in clinics, many platforms have been developed to separate CTCs. However, the high-performance isolation of CTCs remains significant challenges including achieving the sensitivity and specificity necessary due to their extreme rarity and severe biofouling in blood, such as billions of background cells and various proteins. With the advancement of CTCs detection technologies in recent years, the highly efficient and highly specific detection platforms for CTCs have gradually been developed, resulting in improving CTC capture efficiency, purity and sensitivity. In this review, we systematically describe the current strategies with surface modifications by utilizing the antifouling property of polymer, peptide, protein and cell membrane for high-performance enrichment of CTCs. To wrap up, we discuss the substantial challenges facing by current technologies and the potential directions for future research and development.

Multilayer Soft Photolithography Fabrication of Microfluidic Devices Using a Custom-Built Wafer-Scale PDMS Slab Aligner and Cost-Efficient Equipment

We present a robust, low-cost fabrication method for implementation in multilayer soft photolithography to create a PDMS microfluidic chip with features possessing multiple height levels. This fabrication method requires neither a cleanroom facility nor an expensive UV exposure machine. The central part of the method stays on the alignment of numerous PDMS slabs on a wafer-scale instead of applying an alignment for a photomask positioned right above a prior exposure layer using a sophisticated mask aligner. We used a manual XYZR stage attached to a vacuum tweezer to manipulate the top PDMS slab. The bottom PDMS slab sat on a rotational stage to conveniently align with the top part. The movement of the two slabs was observed by a monocular scope with a coaxial light source. As an illustration of the potential of this system for fast and low-cost multilayer microfluidic device production, we demonstrate the microfabrication of a 3D microfluidic chaotic mixer. A discussion on another alternative method for the fabrication of multiple height levels is also presented, namely the micromilling approach.

A micropillar array-based microfluidic chip for label-free separation of circulating tumor cells: The best micropillar geometry?

INTRODUCTION

The information derived from the number and characteristics of circulating tumor cells (CTCs), is crucial to ensure appropriate cancer treatment monitoring. Currently, diverse microfluidic platforms have been developed for isolating CTCs from blood, but it remains a challenge to develop a low-cost, practical, and efficient strategy.

OBJECTIVES

This study aimed to isolate CTCs from the blood of cancer patients via introducing a new and efficient micropillar array-based microfluidic chip (MPA-Chip), as well as providing prognostic information and monitoring the treatment efficacy in cancer patients.

METHODS

We fabricated a microfluidic chip (MPA-Chip) containing arrays of micropillars with different geometries (lozenge, rectangle, circle, and triangle). We conducted numerical simulations to compare velocity and pressure profiles inside the micropillar arrays. Also, we experimentally evaluated the capture efficiency and purity of the geometries using breast and prostate cancer cell lines as well as a blood sample. Moreover, the device's performance was validated on 12 patients with breast cancer (BC) in different states.

RESULTS

The lozenge geometry was selected as the most effective and optimized micropillar design for CTCs isolation, providing high capture efficiency (>85 %), purity (>90 %), and viability (97 %). Furthermore, the lozenge MPA-chip was successfully validated by the detection of CTCs from 12 breast cancer (BC) patients, with non-metastatic (median number of 6 CTCs) and metastatic (median number of 25 CTCs) diseases, showing different prognoses. Also, increasing the chemotherapy period resulted in a decrease in the number of captured CTCs from 23 to 7 for the metastatic patient. The MPA-Chip size was only 0.25 cm² and the throughput of a single chip was 0.5 ml/h, which can be increased by multiple MPA-Chips in parallel.

CONCLUSION

The lozenge MPA-Chip presented a novel micropillar geometry for on-chip CTC isolation, detection, and staining, and in the future, the possibilities can be extended to the culture of the CTCs.

Hedgehog-inspired immunomagnetic beads for high-efficient capture and release of exosomes

Exosomes are small extracellular vesicles secreted by cells. They play an important regulatory role in the physiological and pathological processes of the body, and participate in the occurrence and development of many diseases. Although tumor-derived exosomes have been used as biomarkers for cancer detection, it is still a huge challenge to efficiently capture and release functionally complete exosomes. In our research, inspired by the structure of hedgehog burrs, we proposed immunomagnetic hedgehog particles (IMHPs) to efficiently capture and release exosomes. In general, after the assembly of one-dimensional nanostructural TiO₂ bundles into hedgehog TiO₂ particles with 356.12 ± 38.32 nm spikes, magnetic responsive nanoparticles (Fe₃O₄, ∼20 nm), an antifouling polyethylene glycol (PEG) component containing a redox responsive disulfide linkage and anti-CD63 antibody were introduced stepwise to functionalize hedgehog particles and generate IMHPs (1.23 ± 0.18 μm). Due to their unique topological structures, exosomes were positively selected with an exosomal marker (CD63) and negatively selected by depleting environmental pollutants (protein precipitates, cell debris) with the nano-spikes. These prepared IMHPs were successfully applied to capture exosomes from MCF-7 cells, with a capture efficiency of 91.70%. Then, tris (2-carboxyethyl) phosphine hydrochloride (TCEP) was used to reduce the disulfide bond to release exosomes, and the release efficiency was up to 82.45%. The exosomes that experienced successive immunomagnetic separation and release well maintained their structural integrity and good bioactivity to promote MCF-7 cell migration, as compared with those exosomes separated by the classic ultracentrifugation approach. These results also indicated that IMHPs would have broad prospects in biomedicine and clinical applications, where highly efficient and non-destructive separation of bio-substances (cells, extracellular vesicles, etc.) is critically required.

Peptide-Grafted Microspheres for Mesenchymal Stem Cell Sorting and Expansion by Selective Adhesion

Mesenchymal stem cells (MSCs) have considerable value in regenerative medicine because of their unique properties such as pluripotency, self-renewal ability, and low immunogenicity. Isolation and purification are prerequisites for various biomedical applications of MSCs, and traditional sorting methods are often expensive, complicated, and difficult to apply on a large scale. In addition to purification, the requirement for expansion of cells also limits the further application of MSCs. The purpose of this study was to develop a unique magnetic sorting microsphere to obtain relatively pure and high-yield MSCs in an economical and effective way, that can also be used for the expansion of MSCs. Poly (ethylene glycol) (PEG)-based anti-adhesive treatment of the prepared oleic acid grafted Fe3O4-poly (lactic-co-glycolic acid) magnetic microspheres was performed, and then E7 peptide was covalently grafted onto the treated microspheres. Upon a series of characterization, the magnetic microspheres were of uniform size, and cells were unable to adhere to the PEG-treated surface. E7 grafting significantly improved cell adhesion and proliferation. The results obtained from separate culture of various cell types as well as static or dynamic co-culture showed that selective adhesion of MSCs was observed on the magnetic sorting microspheres. Furthermore, the cells expanded on the microspheres maintained their phenotype and typical differentiation potentials. The magnetic properties of the microspheres enabled sampling, distribution, and transfer of cells without the usage of trypsin digestion. And it facilitated the separation of cells and microspheres for harvesting of MSCs after digestion. These findings have promising prospects for MSC research and clinical applications.

Layer-by-layer assembly methods and their biomedical applications

Various biomedical applications arising due to the development of different LbL assembly methods with unique process properties.

Modification of Hemodialysis Membranes for Efficient Circulating Tumor Cell Capture for Cancer Therapy

Background: It is well known that more than 90% of cancer deaths are due to metastases. However, the entire tumorigenesis process is not fully understood, and it is evident that cells spreading from the primary tumor play a key role in initiating the metastatic process. Tumor proliferation and invasion also elevate the concentration of regular and irregular metabolites in the serum, which may alter the normal function of the entire human homeostasis and possibly causes cancer metabolism syndrome, also referred to as cachexia. Methods: We report on the modification of commercially available hemodialysis membranes to selectively capture circulating tumor cells from the blood stream by means of immobilized human anti-EpCAM antibodies on the inner surface of the fibers. All critical steps are described that required in situ addition of the immuno-affinity feature to hemodialyzer cartridges in order to capture EpCAM positive circulating tumor cells, which represents ~80% of cancer cell types. Results: The cell capture efficiency of the suggested technology was demonstrated by spiking HCT116 cancer cells both into buffer solution and whole blood and run through on the modified cartridge. Flow cytometry was used to quantitatively evaluate the cell clearance performance of the approach. Conclusions: The suggested modification has no significant effect on the porous structure of the hemodialysis membranes; it keeps its cytokine removal capability, addressing cachexia simultaneously with CTC removal.

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.

Graphene Oxide-Based Biosensors for Liquid Biopsies in Cancer Diagnosis

Liquid biopsies use blood or urine as test samples, which are able to be continuously collected in a non-invasive manner. The analysis of cancer-related biomarkers such as circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), microRNA, and exosomes provides important information in early cancer diagnosis, tumor metastasis detection, and postoperative recurrence monitoring assist with clinical diagnosis. However, low concentrations of some tumor markers, such as CTCs, ctDNA, and microRNA, in the blood limit its applications in clinical detection and analysis. Nanomaterials based on graphene oxide have good physicochemical properties and are now widely used in biomedical detection technologies. These materials have properties including good hydrophilicity, mechanical flexibility, electrical conductivity, biocompatibility, and optical performance. Moreover, utilizing graphene oxide as a biosensor interface has effectively improved the sensitivity and specificity of biosensors for cancer detection. In this review, we discuss various cancer detection technologies regarding graphene oxide and discuss the prospects and challenges of this technology.

Simulation of circulating tumor cell transport and adhesion in cell suspensions in microfluidic devices

Understanding cell transport and adhesion dynamics under flow is important for many biotransport problems. We investigated the influence of cell size, ligand coating density, micropost size, and intercellular collisions on circulating tumor cell adhesion and transport in microfluidic devices. The cells were modeled as coarse-grained cell membranes and the adhesion was modeled as pairwise interacting potentials, while the fluid was solved using the lattice Boltzmann method. The coupling between the cell and the fluid was achieved through the immersed boundary method. The cell showed transient rolling adhesion in high shear regions and firm adhesion in low shear regions. The adhesive force for rolling cells on a micropost was increasing before the cell reached the crest of the post and then decreasing afterward. The adhesive strength for cells increases with ligand coating density. Cell trajectories in a microfluidic device with a shifted post design were studied as well. At low concentrations, the majority of the cells follow streamlines closely. However, the intercellular collision and collision from red blood cells impacted the cell trajectories. An L 2 norm of | e | was defined to characterize the difference between the cell trajectories and the associated streamlines. It was shown that | e | L 2 increases with micropost sizes and cell concentrations.

Electrochemical paper-based microfluidic device for high throughput multiplexed analysis

A disposable microfluidic electrochemical paper-based device for multiplexed analysis based on sixteen independent microfluidic channels with electrochemical detection is proposed. A major advantage of this work was the non-necessary use of a wax printer for devices manufacturing which has a high cost of operation. In addition, a commercial multiplexing module was used that has the multiplexing capability of 8-16 channels and, for the first time using this module, the strategy of multiplexing both the working and reference electrodes were used. These sixteen channels with the respective sensors can be operated employing one or multiple electrochemical techniques with good repeatability and reproducibility for high throughput analysis. As a proof of concept, the electrochemical performance of device was tested with ferrocenecarboxylic acid solution employing cyclic voltammetry, square-wave voltammetry, differential-pulse voltammetry and chronoamperometry. This innovative sensing platform presented capacity of production in large scale and application for clinical tests with safety and short time of assays. A biosensor was constructed using glucose oxidase on the platform for the glucose determination in urine as a non-invasive strategy. The analytical curve was linear in the glucose concentration range from 1.0 × 10^-4 mol L^-1 to 4 × 10^-2 mol L^-1, with a limit of detection of 3 × 10^-5 mol L^-1.

Layer-by-layer assembly of nanofilms to control cell functions

Control of cell functions by layer-by-layer assembly has a great challenge in tissue engineering and biomedical applications. We summarize current hot approaches in this review.