Engineered multifunctional metal-phenolic nanocoatings for label-free capture and "self-release" of heterogeneous circulating tumor cells

ECL cytosensor for sensitive and label-free detection of circulating tumor cells based on hierarchical flower-like gold microstructures

The development of sensitive and efficient cell sensing strategies to detect circulating tumor cells (CTCs) in peripheral blood is crucial for the early diagnosis and prognostic assessment of cancer clinical treatment. Herein, an array of hierarchical flower-like gold microstructures (HFGMs) with anisotropic nanotips was synthesized by a simple electrodeposition method and used as a capture substrate to construct an ECL cytosensor based on the specific recognition of target cells by aptamers. The complex topography of the HFGMs array not only catalyzed the enhancement of ECL signals, but also induced the cells to generate more filopodia, improving the capture efficiency and shortening the capture time. The effect of topographic roughness on cell growth and adhesion propensity was also investigated, while the cell capture efficiency was proposed to be an important indicator affecting the accuracy of the ECL cytosensor. In addition, the capture of cells on the electrode surface increased the steric hindrance, which caused ECL signal changes in the Ru(bpy)32+ and TPrA system, realizing the quantitative detection of MCF-7 cells. The detection range of the sensor was from 102 to 106 cells mL-1 and the detection limit was 18 cells mL-1. The proposed detection method avoids the process of separation, labeling and counting, which has great potential for sensitive detection in clinical applications.

Tumor Microenvironment-Inspired Glutathione-Responsive Three-Dimensional Fibrous Network for Efficient Trapping and Gentle Release of Circulating Tumor Cells

Detection of circulating tumor cells (CTCs) is important for early cancer diagnosis, prediction of postoperative recurrence, and individualized treatment. However, it is still challenging to achieve efficient capture and gentle release of CTCs from the complex peripheral blood due to their rarity and fragility. Herein, inspired by the three-dimensional (3D) network structure and high glutathione (GSH) level of the tumor microenvironment (TME), a 3D stereo (3D-G@FTP) fibrous network is developed by combining the liquid-assisted electrospinning method, gas foaming technique, and metal-polyphenol coordination interactions to achieve efficient trapping and gentle release of CTCs. Compared with the traditional 2D@FTP fibrous scaffold, the 3D-G@FTP fibrous network could achieve higher capture efficiency (90.4% vs 78.5%) toward cancer cells in a shorter time (30 min vs 90 min). This platform showed superior capture performance toward heterogeneous cancer cells (HepG2, HCT116, HeLa, and A549) in an epithelial cell adhesion molecule (EpCAM)-independent manner. In addition, the captured cells with high cell viability (>90.0%) could be gently released under biologically friendly GSH stimulus. More importantly, the 3D-G@FTP fibrous network could sensitively detect 4-19 CTCs from six kinds of cancer patients' blood samples. We expect this TME-inspired 3D stereo fibrous network integrating efficient trapping, broad-spectrum recognition, and gentle release will promote the development of biomimetic devices for rare cell analysis.

Conductive Nanofibers-Enhanced Microfluidic Device for the Efficient Capture and Electrical Stimulation-Triggered Rapid Release of Circulating Tumor Cells

The effective detection and release of circulating tumor cells (CTCs) are of great significance for cancer diagnosis and monitoring. The microfluidic technique has proved to be a promising method for CTCs isolation and subsequent analysis. However, complex micro-geometries or nanostructures were often constructed and functionalized to improve the capture efficiency, which limited the scale-up for high-throughput production and larger-scale clinical applications. Thus, we designed a simple conductive nanofiber chip (CNF-Chip)-embedded microfluidic device with a herringbone microchannel to achieve the efficient and specific capture and electrical stimulation-triggered rapid release of CTCs. Here, the most used epithelial cell adhesion molecule (EpCAM) was selected as the representative biomarker, and the EpCAM-positive cancer cells were mainly studied. Under the effects of the nanointerface formed by the nanofibers with a rough surface and the herringbone-based high-throughput microfluidic mixing, the local topographic interaction between target cells and nanofibrous substrate in the microfluidic was synergistically enhanced, and the capture efficiency for CTCs was further improved (more than 85%). After capture, the sensitive and rapid release of CTCs (release efficiency above 97%) could be conveniently achieved through the cleavage of the gold-sulfur bond by applying a low voltage (-1.2 V). The device was successfully used for the effective isolation of CTCs in clinical blood samples from cancer patients, indicating the great potential of this CNF-Chip-embedded microfluidic device in clinical applications.

A multifunctional black phosphorus nanosheet-based immunomagnetic bio-interface for heterogeneous circulating tumor cell capture and simultaneous self-identification in gastric cancer patients

A single epithelial cell adhesion molecule (EpCAM) for circulating tumor cell (CTCs) isolation has been proved to be low in efficiency as it fails to recognize EpCAM-negative CTCs. Meanwhile, the current immunocytochemical (ICC) identification strategy for the captured cells is tedious and time-consuming. To address these issues, we designed a dual-labeled fluorescent immunomagnetic nanoprobe (BP-Fe₃O₄-AuNR/Apt), by loading magnetic Fe₃O₄ nanoparticles and gold nanorods (AuNRs) onto black phosphorus (BP) nanosheets and then linking them with Cy3-labeled EpCAM and Texas red-labeled tyrosine protein kinase 7 (PTK7) aptamers, which created a high-performance bio-interface for efficient, heterogeneous CTC capture and rapid self-identification with high accuracy. As few as 5 CTCs could be captured from 1.0 mL PBS, mixed cell solution and lysed blood. What's more, the presence of BP and AuNRs on this capturing interface also allowed us to preliminarily investigate the potential photothermal therapeutic effect of the probe toward CTC elimination. The applicability of the probe was further demonstrated in gastric cancer patients. By detecting the number of CTCs in the blood of gastric cancer patients, the correlations between the CTC number and the disease stage, as well as distant metastasis were systematically explored.

Antifouling Gold-Inlaid BSA Coating for the Highly Efficient Capture of Circulating Tumor Cells

Large amounts of coexisting contamination in complex biofluid samples impede the quantified veracity of biomarkers, which is the key problem for disease confirmation. Herein, amyloid-like transformed bovine serum albumin inlaid with gold nanoparticles was used as a coating (BGC) on a substrate composed of silicon nanowires (SW; BGC-SW) under ambient conditions. After modification with the recognition group, BGC-SW could serve as an outstanding platform for the selective separation and sensitive detection of biomarkers in complicated biosamples. First, the BGC on SW with a large surface area exhibits excellent adhesion resistance. The attached amounts of contaminations in biofluids were decreased by over 78% compared with native bovine serum albumin (BSA) as the blocking agent. This is because the phase-transformed BSA coating provides stronger interactions with the SW than bare BSA, which results in a tighter attachment and more uniform coverage of the BGC. Furthermore, the gold matrix laid inside the antiadhesive coating ensures simple cross-linking with the recognition groups to selectively capture various biomarkers in complex biofluids and create a gentle release method. Circulating tumor cells (CTCs) were chosen as template biomarkers to verify the application of A-BGC-SW (BGC-SW modified with sgc8-aptamer) in various separation processes of untreated biofluids. The results showed that approximately six cells could be captured from a 1 mL fresh blood sample containing only 10 CTCs. The easy fabrication and excellent antiadhesion property endow A-BGC-SW with great potential in the field of biological separation.