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

Bio-Tailored Sensing at the Nanoscale: Biochemical Aspects and Applications

The demonstration of the first enzyme-based electrode to detect glucose, published in 1967 by S. J. Updike and G. P. Hicks, kicked off huge efforts in building sensors where biomolecules are exploited as native or modified to achieve new or improved sensing performances. In this growing area, bionanotechnology has become prominent in demonstrating how nanomaterials can be tailored into responsive nanostructures using biomolecules and integrated into sensors to detect different analytes, e.g., biomarkers, antibiotics, toxins and organic compounds as well as whole cells and microorganisms with very high sensitivity. Accounting for the natural affinity between biomolecules and almost every type of nanomaterials and taking advantage of well-known crosslinking strategies to stabilize the resulting hybrid nanostructures, biosensors with broad applications and with unprecedented low detection limits have been realized. This review depicts a comprehensive collection of the most recent biochemical and biophysical strategies for building hybrid devices based on bioconjugated nanomaterials and their applications in label-free detection for diagnostics, food and environmental analysis.

Recent advances in micro-/nanostructure array integrated microfluidic devices for efficient separation of circulating tumor cells

Circulating tumor cells (CTCs) released from the primary tumor to peripheral blood are promising targets for liquid biopsies. Their biological information is vital for early cancer detection, efficacy assessment, and prognostic monitoring. Despite the tremendous clinical applications of CTCs, development of effective separation techniques are still demanding. Traditional separation methods usually use batch processing for enrichment, which inevitably destroy cell integrity and affect the complete information acquisition. Considering the rarity and heterogeneity of CTCs, it is urgent to develop effective separation methods. Microfluidic chips with precise fluid control at the micron level are promising devices for CTC separation. Their further combination with micro-/nanostructure arrays adds more biomolecule binding sites and exhibit unique fluid barrier effect, which significantly improve the CTC capture efficiency, purity, and sensitivity. This review summarized the recent advances in micro-/nanostructure array integrated microfluidic devices for CTC separation, including microrods, nanowires, and 3D micro-/nanostructures. The mechanisms by which these structures contribute to improved capture efficiency are discussed. Two major categories of separation methods, based on the physical and biological properties of CTCs, are discussed separately. Physical separation includes the design and preparation of micro-/nanostructure arrays, while chemical separation additionally involves the selection and modification of specific capture probes. These emerging technologies are expected to become powerful tools for disease diagnosis in the future.

Biomedical Applications of Microfluidic Devices: A Review

Both passive and active microfluidic chips are used in many biomedical and chemical applications to support fluid mixing, particle manipulations, and signal detection. Passive microfluidic devices are geometry-dependent, and their uses are rather limited. Active microfluidic devices include sensors or detectors that transduce chemical, biological, and physical changes into electrical or optical signals. Also, they are transduction devices that detect biological and chemical changes in biomedical applications, and they are highly versatile microfluidic tools for disease diagnosis and organ modeling. This review provides a comprehensive overview of the significant advances that have been made in the development of microfluidics devices. We will discuss the function of microfluidic devices as micromixers or as sorters of cells and substances (e.g., microfiltration, flow or displacement, and trapping). Microfluidic devices are fabricated using a range of techniques, including molding, etching, three-dimensional printing, and nanofabrication. Their broad utility lies in the detection of diagnostic biomarkers and organ-on-chip approaches that permit disease modeling in cancer, as well as uses in neurological, cardiovascular, hepatic, and pulmonary diseases. Biosensor applications allow for point-of-care testing, using assays based on enzymes, nanozymes, antibodies, or nucleic acids (DNA or RNA). An anticipated development in the field includes the optimization of techniques for the fabrication of microfluidic devices using biocompatible materials. These developments will increase biomedical versatility, reduce diagnostic costs, and accelerate diagnosis time of microfluidics technology.

Multifunctional microfluidic chip for cancer diagnosis and treatment

Microfluidic chip is not a chip in the traditional sense. It is technologies that control fluids at the micro level. As a burgeoning biochip, microfluidic chips integrate multiple disciplines, including physiology, pathology, cell biology, biophysics, engineering mechanics, mechanical design, materials science, and so on. The application of microfluidic chip has shown tremendous promise in the field of cancer therapy in the past three decades. Various types of cell and tissue cultures, including 2D cell culture, 3D cell culture and tissue organoid culture could be performed on microfluidic chips. Patient-derived cancer cells and tissues can be cultured on microfluidic chips in a visible, controllable, and high-throughput manner, which greatly advances the process of personalized medicine. Moreover, the functionality of microfluidic chip is greatly expanding due to the customizable nature. In this review, we introduce its application in developing cancer preclinical models, detecting cancer biomarkers, screening anti-cancer drugs, exploring tumor heterogeneity and producing nano-drugs. We highlight the functions and recent development of microfluidic chip to provide references for advancing cancer diagnosis and treatment.

Microfluidic applications on circulating tumor cell isolation and biomimicking of cancer metastasis

The prognosis of malignant tumors is challenged by insufficient means to effectively detect tumors at early stage. Liquid biopsy using circulating tumor cells (CTCs) as biomarkers demonstrates a promising solution to tackle the challenge, because CTCs play a critical role in cancer metastatic process via intravasation, circulation, extravasation, and formation of secondary tumor. However, the effectiveness of the solution is compromised by rarity, heterogeneity, and vulnerability associated with CTCs. Among a plethora of novel approaches for CTC isolation and enrichment, microfluidics leads to isolation and detection of CTCs in a cost-effective and operation-friendly way. Development of microfluidics also makes it feasible to model the cancer metastasis in vitro using a microfluidic system to mimick the in vivo microenvironment, thereby enabling analysis and monitor of tumor metastasis. This paper aims to review the latest advances for exploring the dual-roles microfluidics has played in early cancer diagnosis via CTC isolation and investigating the role of CTCs in cancer metastasis; the merits and drawbacks for dominating microfluidics-based CTC isolation methods are discussed; biomimicking cancer metastasis using microfluidics are presented with example applications on modelling of tumor microenvironment, tumor cell dissemination, tumor migration, and tumor angiogenesis. The future perspectives and challenges are discussed.

Aminophenylboronic Acid-Functionalized Thorny-Trap-Shaped Monolayer Microarray for Efficient Capture and Release of Circulating Tumor Cells

An aminophenylboronic acid (APBA)-functionalized thorny-trap-shaped monolayer microarray as a 3D fractal structures' substrate was fabricated to capture and release circulating tumor cells (CTCs) efficiently. The microarray can not only trap cells inside by microbowls but also enhance the interaction between cell and substrate by providing more binding sites and facilitating the spread of cell filopodias via the growth of nanorods. Modification of APBA enhanced the interaction further by binding with sialic acid of CTCs surface. The special topological structure achieved a high capture efficiency of 79.5%. The captured cancer cells were released without introducing any affinity molecules by a ligand exchange reaction with up to 70% efficiency and good proliferation. This substrate can isolate 33 tumor cells from a mimic blood sample even at a low spiked number of 50 cancer cells. This study provides valuable guidance for isolation and release of CTCs and is significant for the further study of tumors.

Single-cell Analysis with Microfluidic Devices

A microfluidic device as a pivotal research tool in chemistry and life science is now widely recognized. Indeed, microfluidic techniques have made significant advancements in fundamental research, such as the inherent heterogeneity of single-cells studies in cell populations, which would be helpful in understanding cellular molecular mechanisms and clinical diagnosis of major diseases. Single-cell analyses on microdevices have shown great potential for precise fluid control, cell manipulation, and signal output with rapid and high throughput. Moreover, miniaturized devices also have open functions such as integrating with traditional detection methods, for example, optical, electrochemical or mass spectrometry for single-cell analysis. In this review, we summarized recent advances of single-cell analysis based on various microfluidic approaches from different dimensions, such as in vitro, ex vivo, and in vivo analysis of single cells.

Size-matching hierarchical micropillar arrays for detecting circulating tumor cells in breast cancer patients' whole blood

Circulating tumor cells (CTCs) are important markers for cancer diagnosis and treatment, but it is still a challenge to recognize and isolate CTCs because they are very rare in the blood. To selectively recognize CTCs and improve the capture efficiency, micro/nanostructured substrates have been fabricated for this application; however the size of CTCs is often ignored in designing and engineering micro/nanostructured substrates. Herein, a spiky polymer micropillar array is fabricated for capturing CTCs with high efficiency. The surface of the micropillar is cactus-like, and is composed of nanospikes. This hierarchical polymer array is designed according to the size of CTCs, which allows for more interactions of the CTCs with the array by setting the size of gaps among the micropillars to match with the CTCs. This polymer array is created by molding on an ordered silicon array, and then it is coated with an antiepithelial cell adhesion molecule antibody (anti-EpCAM). After co-culture with MCF-7 cells for 45 min, the capture efficiency of this array for CTCs is up to 91% ± 2%. Moreover, the anti-EpCAM modified polymer micropillar arrays present an excellent capacity to isolate CTCs from the whole blood samples of breast cancer patients. This study may provide a new concept for capturing target cells by designing and engineering micro/nanostructured substrates according to the size of target cells.

Multifunctional hybrid graphene oxide for circulating tumor cell isolation and analysis

Even in 21st century, >90% cancer-associated deaths are caused by metastatic disease. Circulating tumor cells (CTCs), which circulate in the blood stream after release from primary tumors, extravasate and form fatal metastases in different organs. Several clinical trials indicate that CTCs can be used as a liquid biopsy of tumors for early diagnosis of cancers. Since CTCs are extremely rare and exhibit heterogeneous biology due to epithelial-mesenchymal transition (EMT), oncologists continue to face enormous challenges in using CTCs as a true "liquid biopsy" for cancer patients. Recent advancements in nanoscience allow us to design nano-architectures with the capability of targeted CTCs isolation and identification. In the current review, we discuss contribution from different groups on the development of graphene oxide based nanoarchitecture for effective isolation and accurate identification of CTCs from whole blood. In the last few years, using zero-dimensional (0D), two dimensional (2D) and three dimensional (3D) multifunctional hybrid graphene oxide (GO), different types of nanoarchitectures have been designed. These nanoarchitectures represent a highly powerful platform for CTC diagnosis. We discuss the major design criteria that have been used to develop hybrid GO nanoarchitectures for selective capture and accurate identification of heterogeneous CTCs from whole blood. At the end, we conclude with the promises, major challenges, and prospect to clinically translate the identification of CTCs using GO based nanotechnology.

TiO2 Nanorod Arrays with Mesoscopic Micro-Nano Interfaces for in Situ Regulation of Cell Morphology and Nucleus Deformation

Cell morphology and nucleus deformation are important when circulating tumor cells break away from the primary tumor and migrate to a distant organ. Cells are sensitive to the microenvironment and respond to the cell-material interfaces. We fabricated TiO₂ nanorod arrays with mesoscopic micro-nano interfaces through a two-step hydrothermal reaction method to induce severe changes in cell morphology and nucleus deformation. The average size of the microscale voids was increased from 5.1 to 10.5 μm when the hydrothermal etching time was increased from 3 to 10 h, whereas the average distances between voids were decreased from 0.88 to 0.40 μm. The nucleus of the MCF-7 cells on the TiO₂ nanorod substrate that was etched for 10 h exhibited a significant deformation, because of the large size of the voids and the small distance between voids. Nucleus defromation was reversible during the cells proliferate process when the cells were cultured on the mesoscopic micro-nano interface.This reversible process was regulated by combining of the uniform pressure applied by the actin cap and the localized pressure applied by the actin underneath the nucleus. Cell morphology and nucleus shape interacted with each other to adapt to the microenvironment. This mesoscopic micro-nano interface provided a new insight into the cell-biomaterial interface to investigate cell behaviors.

Real-Time Continuous Identification of Greenhouse Plant Pathogens Based on Recyclable Microfluidic Bioassay System

The development of a real-time continuous analytical platform for the pathogen detection is of great scientific importance for achieving better disease control and prevention. In this work, we report a rapid and recyclable microfluidic bioassay system constructed from oligonucleotide arrays for selective and sensitive continuous identification of DNA targets of fungal pathogens. We employ the thermal denaturation method to effectively regenerate the oligonucleotide arrays for multiple sample detection, which could considerably reduce the screening effort and costs. The combination of thermal denaturation and laser-induced fluorescence detection technique enables real-time continuous identification of multiple samples (<10 min per sample). As a proof of concept, we have demonstrated that two DNA targets of fungal pathogens (Botrytis cinerea and Didymella bryoniae) can be sequentially analyzed using our rapid microfluidic bioassay system, which provides a new paradigm in the design of microfluidic bioassay system and will be valuable for chemical and biomedical analysis.

Direct Writing of Microfluidic Footpaths by Pyro-EHD Printing

In this study, we report a direct writing method for the fabrication of microfluidic footpaths by pyro-electrohydrodynamic (EHD) jet printing. Here, we propose the use of a nozzle-free three-dimensional printing technique for the fabrication of printed structures that can be embedded in a variety of soft, transparent, flexible, and biocompatible polymers and thus easily integrated into lab-on-chip devices. We prove the advantage of the high resolution and flexibility of pyro-EHD printing for the realization of microfluidic channels well below the standard limit in dimension of conventional ink-jet printing technique and simply adaptable to the end-user desires in terms of geometry and materials. Starting from the description of the innovative approach proposed for the channel fabrication, we demonstrate the design, fabrication, and proof of a microfluidic matrix of interconnected channels. The method described here could be a breakthrough technology for the fabrication of in situ implantable, stretchable, and biocompatible devices, opening new routes in the field of biomedical engineering and wearable electronics.