Quantification techniques for circulating tumor cells

Microfluidic technologies in cell isolation and analysis for biomedical applications

Efficient platforms for cell isolation and analysis play an important role in applied and fundamental biomedical studies. As cells commonly have a size of around 10 microns, conventional handling approaches at a large scale are still challenged in precise control and efficient recognition of cells for further performance of isolation and analysis. Microfluidic technologies have become more prominent in highly efficient cell isolation for circulating tumor cells (CTCs) detection, single-cell analysis and stem cell separation, since microfabricated devices allow for the spatial and temporal control of complex biochemistries and geometries by matching cell morphology and hydrodynamic traps in a fluidic network, as well as enabling specific recognition with functional biomolecules in the microchannels. In addition, the fabrication of nano-interfaces in the microchannels has been increasingly emerging as a very powerful strategy for enhancing the capability of cell capture by improving cell-interface interactions. In this review, we focus on highlighting recent advances in microfluidic technologies for cell isolation and analysis. We also describe the general biomedical applications of microfluidic cell isolation and analysis, and finally make a prospective for future studies.

Aptamer-Based Dual-Functional Probe for Rapid and Specific Counting and Imaging of MCF-7 Cells

Development of multimodal detection technologies for accurate diagnosis of cancer at early stages is in great demand. In this work, we report a novel approach using an aptamer-based dual-functional probe for rapid, sensitive, and specific counting and visualization of MCF-7 cells by inductively coupled plasma-mass spectrometry (ICP-MS) and fluorescence imaging. The probe consists of a recognition unit of aptamer to catch cancer cells specifically, a fluorescent dye (FAM) moiety for fluorescence resonance energy transfer (FRET)-based "off-on" fluorescence imaging as well as gold nanoparticles (Au NPs) tag for both ICP-MS quantification and fluorescence quenching. Due to the signal amplification effect and low spectral interference of Au NPs in ICP-MS, an excellent linearity and sensitivity were achieved. Accordingly, a limit of detection of 81 MCF-7 cells and a relative standard deviation of 5.6% (800 cells, n = 7) were obtained. The dynamic linear range was 2 × 10² to 1.2 × 10⁴ cells, and the recoveries in human whole blood were in the range of 98-110%. Overall, the established method provides quantitative and visualized information on MCF-7 cells with a simple and rapid process and paves the way for a promising strategy for biomedical research and clinical diagnostics.

Lab-on-a-Chip Platforms for Detection of Cardiovascular Disease and Cancer Biomarkers

Cardiovascular disease (CVD) and cancer are two leading causes of death worldwide. CVD and cancer share risk factors such as obesity and diabetes mellitus and have common diagnostic biomarkers such as interleukin-6 and C-reactive protein. Thus, timely and accurate diagnosis of these two correlated diseases is of high interest to both the research and healthcare communities. Most conventional methods for CVD and cancer biomarker detection such as microwell plate-based immunoassay and polymerase chain reaction often suffer from high costs, low test speeds, and complicated procedures. Recently, lab-on-a-chip (LoC)-based platforms have been increasingly developed for CVD and cancer biomarker sensing and analysis using various molecular and cell-based diagnostic biomarkers. These new platforms not only enable better sample preparation, chemical manipulation and reaction, high-throughput and portability, but also provide attractive features such as label-free detection and improved sensitivity due to the integration of various novel detection techniques. These features effectively improve the diagnostic test speed and simplify the detection procedure. In addition, microfluidic cell assays and organ-on-chip models offer new potential approaches for CVD and cancer diagnosis. Here we provide a mini-review focusing on recent development of LoC-based methods for CVD and cancer diagnostic biomarker measurements, and our perspectives of the challenges, opportunities and future directions.

High Signal-to-Background Ratio Detection of Cancer Cells with Activatable Strategy Based on Target-Induced Self-Assembly of Split Aptamers

Highly sensitive detection of cancer cells with high signal-to-background ratio (SBR) is still urgently needed. Here, a self-assembling activatable probe (SAAP) based on split aptamers was developed to meet this purpose. The SAAP is formed with quenched fluorescence; only when target cells are present would the split aptamers self-assemble together and thus activate fluorescence by intramolecular and intermolecular fluorescence quenching strategies. As proof of concept, a split aptamer pair stemming from an intact aptamer, ZY11, developed by our lab was selected to construct SAAP. Owing to the design of self-assembly and activation strategy, the SBR of our approach could be raised to ∼40 and achieved a very low detection limit of seven target 7721 cells in 100 μL of binding buffer. Meanwhile, one-step detection of target cells was achieved within 15 min without any washing steps and pretreatment, which shows potential for point-of-care detection. Moreover, we succeeded in the specific recognition of target cells in 50% human serum and mixed cell samples, which indicated this strategy had great advantages in detection in complex biological samples. In addition, dual-signal detection was also successfully implemented, which may be helpful for accurate detection of target cells. Therefore, this rapid, facile, specific, and highly sensitive detection method for cancer cells may provide convenience in cancer research and medical diagnosis.