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

Recent advances in nano/microfluidics-based cell isolation techniques for cancer diagnosis and treatments

Miniaturization has improved significantly in the recent decade, which has enabled the development of numerous microfluidic systems. Microfluidic technologies have shown great potential for separating desired cells from heterogeneous samples, as they offer benefits such as low sample consumption, easy operation, and high separation accuracy. Microfluidic cell separation approaches can be classified into physical (label-free) and biological (labeled) methods based on their working principles. Each method has remarkable and feasible benefits for the purposes of cancer detection and therapy, as well as the challenges that we have discussed in this article. In this review, we present the recent advances in microfluidic cell sorting techniques that incorporate both physical and biological aspects, with an emphasis on the methods by which the cells are separated. We first introduce and discuss the biological cell sorting techniques, followed by the physical cell sorting techniques. Additionally, we explore the role of microfluidics in drug screening, drug delivery, and lab-on-chip (LOC) therapy. In addition, we discuss the challenges and future prospects of integrated microfluidics for cell sorting.

Dislodgement of Hydrogen Bubbles in Microchannels with Embedded Pillars: An Analytical, Experimental, and Numerical Study

Microchannels with integrated pillars have enhanced the production capabilities and performance of various applications due to their high surface-to-volume ratio. However, emerging gas bubbles can become trapped, potentially limiting the functionality or efficiency of the device when scaled down to the low-micrometer scale. Understanding the conditions required to dislodge these bubbles is thus critical for optimizing microfluidic devices with complex physical behaviors. Here an analytical model is presented that outlines the dislodgment conditions and driving forces for such gas-liquid flows. These terms are derived from the gas-liquid interface properties, geometry, and processing parameters. As the density of the pillar arrangement is scaled down, the resistance to bubble dislodgment typically increases. Nevertheless, the bubble is compelled to dislodge at lower pressure loads when critical volumes are reached. This newly discovered effect is particularly noticeable in densely packed arrays and can be explained by the interplay of increased surface tension, geometrical restrictions, and volume-preserving forces. The analytical terms and effects are validated through novel experimental and numerical methods tailored for microchannels in the low-micrometer scale, showing strong agreement.

The Shape Effect of Acoustic Micropillar Array Chips in Flexible Label-Free Separation of Cancer Cells

The precise isolation of circulating tumor cells (CTCs) from blood samples is a potent tool for cancer diagnosis and clinical prognosis. However, CTCs are present in extremely low quantities in the bloodstream, posing a significant challenge to their isolation. In this study, we propose a non-contact acoustic micropillar array (AMPA) chip based on acoustic streaming for the flexible, label-free capture of cancer cells. Three shapes of micropillar array chips (circular, rhombus, and square) were fabricated. The acoustic streaming characteristics generated by the vibration of microstructures of different shapes are studied in depth by combining simulation and experiment. The critical parameters (voltage and flow rate) of the device were systematically investigated using microparticle experiments to optimize capture performance. Subsequently, the capture efficiencies of the three micropillar structures were experimentally evaluated using mouse whole blood samples containing cancer cells. The experimental results revealed that the rhombus microstructure was selected as the optimal shape, demonstrating high capture efficiency (93%) and cell activity (96%). Moreover, the reversibility of the acoustic streaming was harnessed for the flexible release and capture of cancer cells, facilitating optical detection and analysis. This work holds promise for applications in monitoring cancer metastasis, bio-detection, and beyond.

On-chip Raman spectroscopy of live single cells for the staging of oesophageal adenocarcinoma progression

The absence of early diagnosis contributes to oesophageal cancer being the sixth most common cause of global cancer-associated deaths, with a 5-year survival rate of < 20%. Barrett's oesophagus is the main pre-cancerous condition to adenocarcinoma development, characterised by the morphological transition of oesophageal squamous epithelium to metaplastic columnar epithelium. Early tracking and treatment of oesophageal adenocarcinoma could dramatically improve with diagnosis and monitoring of patients with Barrett's Oesophagus. Current diagnostic methods involve invasive techniques such as endoscopies and, with only a few identified biomarkers of disease progression, the detection of oesophageal adenocarcinoma is costly and challenging. In this work, single-cell Raman spectroscopy was combined with microfluidic techniques to characterise the development of oesophageal adenocarcinoma through the progression of healthy epithelial, Barrett's oesophagus and oesophageal adenocarcinoma cell lines. Principal component analysis and linear discriminant analysis were used to classify the different stages of cancer progression. with the ability to differentiate between healthy and cancerous cells with an accuracy of 97%. Whilst the approach could also separate the dysplastic stages from healthy or cancer with high accuracy-the intra-class separation was approximately 68%. Overall, these results highlight the potential for rapid and reliable diagnostic/prognostic screening of Barrett's Oesophagus patients.

A Cascaded Phase-Transfer Microfluidic Chip with Magnetic Probe for High-Activity Sorting, Purification, Release, and Detection of Circulating Tumor Cells

Microfluidic chips have emerged as a promising tool for sorting and enriching circulating tumor cells (CTCs) in blood, while the efficacy and purity of CTC sorting greatly depend on chip design. Herein, a novel cascaded phase-transfer microfluidic chip was developed for high-efficiency sorting, purification, release, and detection of MCF-7 cells (as a model CTC) in blood samples. MCF-7 cells were specifically captured by EpCAM aptamer-modified magnetic beads and then introduced into the designed cascaded phase-transfer microfluidic chip that consisted of three functional regions (sorting, purification, and release zone). In the sorting zone, the MCF-7 cells moved toward the inner wall of the channel and entered the purification zone for primary separation from white blood cells; in the purification zone, the MCF-7 cells were transferred to the phosphate-buffered saline flow under the interaction of Dean forces and central magnetic force, achieving high purification of MCF-7 cells from blood samples; in the release zone, MCF-7 cells were further transferred into the nuclease solution and fixed in groove by the strong magnetic force and hydrodynamic force, and the continuously flowing nuclease solution cleaved the aptamer on the trapped MCF-7 cells, causing gentle release of MCF-7 cells for subsequent inductively coupled plasma mass spectrometry (ICP-MS) detection or further cultivation. By measurement of the endogenous element Zn in the cells using ICP-MS for cell counting, an average cell recovery of 84% for MCF-7 cells was obtained in spiked blood samples. The developed method was applied in the analysis of real blood samples from healthy people and breast cancer patients, and CTCs were successfully detected in all tested patient samples (16/16). Additionally, the removal of the magnetic probes on the cell surface significantly improved cell viability up to 99.3%. Therefore, the developed cascaded phase-transfer microfluidic chip ICP-MS system possessed high integration for CTCs analysis with high cell viability, cell recovery, and purity, showing great advantages in early clinical cancer diagnosis.

Microfluidic-based technologies in cancer liquid biopsy: Unveiling the role of horizontal gene transfer (HGT) materials

Liquid biopsy includes the isolating and analysis of non-solid biological samples enables us to find new ways for molecular profiling, prognostic assessment, and better therapeutic decision-making in cancer patients. Despite the conventional theory of tumor development, a non-vertical transmission of DNA has been reported among cancer cells and between cancer and normal cells. The phenomenon referred to as horizontal gene transfer (HGT) has the ability to amplify the advancement of tumors by disseminating genes that encode molecules conferring benefits to the survival or metastasis of cancer cells. Currently, common liquid biopsy approaches include the analysis of extracellular vesicles (EVs) and tumor-free DNA (tfDNA) derived from primary tumors and their metastatic sites, which are well-known HGT mediators in cancer cells. Current technological and molecular advances expedited the high-throughput and high-sensitive HGT materials analyses by using new technologies, such as microfluidics in liquid biopsies. This review delves into the convergence of microfluidic-based technologies and the investigation of Horizontal Gene Transfer (HGT) materials in cancer liquid biopsy. The integration of microfluidics offers unprecedented advantages such as high sensitivity, rapid analysis, and the ability to analyze rare cell populations. These attributes are instrumental in detecting and characterizing CTCs, circulating nucleic acids, and EVs, which are carriers of genetic cargo that could potentially undergo HGT. The phenomenon of HGT in cancer has raised intriguing questions about its role in driving genomic diversity and acquired drug resistance. By leveraging microfluidic platforms, researchers have been able to capture and analyze individual cells or genetic material with enhanced precision, shedding light on the potential transfer of genetic material between cancer cells and surrounding stromal cells. Furthermore, the application of microfluidics in single-cell sequencing has enabled the elucidation of the genetic changes associated with HGT events, providing insights into the evolution of tumor genomes. This review also discusses the challenges and opportunities in studying HGT materials using microfluidic-based technologies. In conclusion, microfluidic-based technologies have significantly advanced the field of cancer liquid biopsy, enabling the sensitive and accurate detection of HGT materials. As the understanding of HGT's role in tumor evolution and therapy resistance continues to evolve, the synergistic integration of microfluidics and HGT research promises to provide valuable insights into cancer biology, with potential implications for precision oncology and therapeutic strategies.

Dual-source powered nanomotors coupled with dual-targeting ligands for efficient capture and detection of CTCs in whole blood and in vivo tumor imaging

Circulating tumor cells (CTCs) are important biomarkers in cancer diagnosis. However, the specific labeling of CTCs with high capture efficiency in whole blood remains a problem. Herein, a dual-source-driven nanomotor coupled with dual-targeting ligands (CD@NM) was designed for efficient capture, specific imaging and quantitative detection of CTCs. In both water and biological fluid, CD@NMs moved autonomously under the propulsion of a magnetic field and H2O2 solution, which improved the capture efficiency of CTCs to 97.50 ± 2.38%. More importantly, specific labeling of CTCs was achieved by fluorescence quenching and recovery of fluorescent carbon dots modified on the CD@NMs. As a result, the CD@NMs exhibited efficient CTC capture, specific CTC imaging and recognition in whole blood. CD@NMs were also successfully deployed in the specific imaging of tumor tissues in vivo. On this basis, CD@NMs are expected to provide a new platform for tumor diagnosis both in vitro and in vivo.

Cell Culture Model Evolution and Its Impact on Improving Therapy Efficiency in Lung Cancer

Optimizing cell culture conditions is essential to ensure experimental reproducibility. To improve the accuracy of preclinical predictions about the response of tumor cells to different classes of drugs, researchers have used 2D or 3D cell cultures in vitro to mimic the cellular processes occurring in vivo. While 2D cell culture provides valuable information on how therapeutic agents act on tumor cells, it cannot quantify how the tumor microenvironment influences the response to therapy. This review presents the necessary strategies for transitioning from 2D to 3D cell cultures, which have facilitated the rapid evolution of bioengineering techniques, leading to the development of microfluidic technology, including organ-on-chip and tumor-on-chip devices. Additionally, the study aims to highlight the impact of the advent of 3D bioprinting and microfluidic technology and their implications for improving cancer treatment and approaching personalized therapy, especially for lung cancer. Furthermore, implementing microfluidic technology in cancer studies can generate a series of challenges and future perspectives that lead to the discovery of new predictive markers or targets for antitumor treatment.

Immunomagnetic Isolation of HER2-Positive Breast Cancer Cells Using a Microfluidic Device

Analysis of circulating tumor cells (CTCs) as a tool for monitoring metastatic cancers, early diagnosis, and evaluation of disease prognosis paves the way toward personalized cancer treatment. Developing an effective, feasible, and low-cost method to facilitate CTC isolation is, therefore, vital. In the present study, we integrated magnetic nanoparticles (MNPs) with microfluidics and used them for the isolation of HER2-positive breast cancer cells. Iron oxide MNPs were synthesized and functionalized with the anti-HER2 antibody. The chemical conjugation was verified by Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and dynamic light scattering/zeta potential analysis. The specificity of the functionalized NPs for the separation of HER2-positive from HER2-negative cells was demonstrated in an off-chip test setting. The off-chip isolation efficiency was 59.38%. The efficiency of SK-BR-3 cell isolation using a microfluidic chip with a S-shaped microchannel was considerably enhanced to 96% (a flow rate of 0.5 mL/h) without chip clogging. Besides, the analysis time for the on-chip cell separation was 50% faster. The clear advantages of the present microfluidic system offer a competitive solution in clinical applications.

Combined Femtosecond Laser Glass Microprocessing for Liver-on-Chip Device Fabrication

Nowadays, lab-on-chip (LOC) devices are attracting more and more attention since they show vast prospects for various biomedical applications. Usually, an LOC is a small device that serves a single laboratory function. LOCs show massive potential for organ-on-chip (OOC) device manufacturing since they could allow for research on the avoidance of various diseases or the avoidance of drug testing on animals or humans. However, this technology is still under development. The dominant technique for the fabrication of such devices is molding, which is very attractive and efficient for mass production, but has many drawbacks for prototyping. This article suggests a femtosecond laser microprocessing technique for the prototyping of an OOC-type device-a liver-on-chip. We demonstrate the production of liver-on-chip devices out of glass by using femtosecond laser-based selective laser etching (SLE) and laser welding techniques. The fabricated device was tested with HepG2(GS) liver cancer cells. During the test, HepG2(GS) cells proliferated in the chip, thus showing the potential of the suggested technique for further OOC development.

Recent Trends of Microfluidics in Food Science and Technology: Fabrications and Applications

The development of novel materials with microstructures is now a trend in food science and technology. These microscale materials may be applied across all steps in food manufacturing, from raw materials to the final food products, as well as in the packaging, transport, and storage processes. Microfluidics is an advanced technology for controlling fluids in a microscale channel (1~100 μm), which integrates engineering, physics, chemistry, nanotechnology, etc. This technology allows unit operations to occur in devices that are closer in size to the expected structural elements. Therefore, microfluidics is considered a promising technology to develop micro/nanostructures for delivery purposes to improve the quality and safety of foods. This review concentrates on the recent developments of microfluidic systems and their novel applications in food science and technology, including microfibers/films via microfluidic spinning technology for food packaging, droplet microfluidics for food micro-/nanoemulsifications and encapsulations, etc.