Dual targeting negative enrichment strategy for highly sensitive and purity detection of CTCs

Circulating tumor cells (CTCs) have significant clinical value in early tumor detection, dynamic monitoring and immunotherapy. CTC detection stands out as a leading non-invasive approach for tumor diagnostics and therapeutics. However, the high heterogeneity of CTCs and the occurrence of epithelial-mesenchymal transition (EMT) during metastasis pose challenges to methods relying on EpCAM-positive enrichment. To address these limitations, a method based on negative enrichment of CTCs using specific leukocyte targets has been developed. In this study, aiming to overcome the low purity associated with immunomagnetic beads targeting solely the leukocyte common antigen CD45, we introduced CD66b-modified immunomagnetic beads. CD66b, a specific target for neutrophils with abundant residues, was chosen as a complementary approach. The process involved initial collection of nucleated cells from whole blood samples using density gradient centrifugation. Subsequently, magnetically labeled leukocytes were removed by magnetic field, enabling the capture of CTCs with higher sensitivity and purity while retaining their activity. Finally, we selected 20 clinical blood samples from patients with various cancers to validate the effectiveness of this strategy, providing a new generalized tool for the clinical detection of CTCs.

Microfluidic-SERS Technologies for CTC: A Perspective on Clinical Translation

Enumeration and phenotypic profiling of circulating tumor cells (CTCs) provide critical information for clinical diagnosis and treatment monitoring in cancer. To achieve this goal, an integrated system is needed to efficiently isolate CTCs from patient samples and sensitively evaluate their phenotypes. Such integration would comprise a high-throughput single-cell processing unit for the isolation and manipulation of CTCs and a sensitive and multiplexed quantitation unit to detect clinically relevant signals from these cells. Surface-enhanced Raman scattering (SERS) has been used as an analytical method for molecular profiling and in vitro cancer diagnosis. More recently, its multiplexing capability and power to create distinct molecular signatures against their targets have garnered attention. Here, we share our insights into the combined power of microfluidics and SERS in realizing CTC isolation, enumeration, and detection from a clinical translation perspective. We highlight the key operational factors in CTC microfluidic processing and SERS detection from patient samples. We further discuss microfluidic-SERS integration and its clinical utility as a paradigm shift in clinical CTC-based cancer diagnosis and prognostication. Finally, we summarize the challenges and attempt to look forward to what lies ahead of us in potentially translating the technique into real clinical applications.

Application of functional peptides in the electrochemical and optical biosensing of cancer biomarkers

Early screening and diagnosis are the most effective ways to prevent the occurrence and progression of cancers, thus many biosensing strategies have been developed to achieve economic, rapid, and effective detection of various cancer biomarkers. Recently, functional peptides have been gaining increasing attention in cancer-related biosensing due to their advantageous features of a simple structure, ease of synthesis and modification, high stability, and good biorecognition, self-assembly and antifouling capabilities. Functional peptides can not only act as recognition ligands or enzyme substrates for the selective identification of different cancer biomarkers but also function as interfacial materials or self-assembly units to improve the biosensing performances. In this review, we summarize the recent advances in functional peptide-based biosensing of cancer biomarkers according to the used techniques and the roles of peptides. Particular attention is focused on the use of electrochemical and optical techniques, both of which are the most commonly used techniques in the field of biosensing. The challenges and promising prospects of functional peptide-based biosensors in clinical diagnosis are also discussed.

Tailored point-of-care biosensors for liquid biopsy in the field of oncology

In the field of cancer detection, technologies to analyze tumors using biomarkers circulating in fluids such as blood have developed rapidly based on liquid biopsy. A proactive approach to early cancer detection can lead to more effective treatments with minimal side effects and better long-term patient survival. However, early detection of cancer is hindered by the existing limitations of conventional cancer diagnostic methods. To enable early diagnosis and regular monitoring and improve automation, the development of integrated point-of-care (POC) and biosensors is needed. This is expected to fundamentally change the diagnosis, management, and monitoring of response to treatment of cancer. POC-based techniques will provide a way to avoid complications that occur after invasive tissue biopsy, such as bleeding, infection, and pain. The aim of this study is to provide a comprehensive view of biosensors and their clinical relevance in oncology for the detection of biomarkers with liquid biopsies of proteins, miRNA, ctDNA, exosomes, and cancer cells. The preceding discussion also illustrates the changing landscape of liquid biopsy-based cancer diagnosis through nanomaterials, machine learning, artificial intelligence, wearable devices, and sensors, many of which apply POC design principles. With the advent of sensitive, selective, and timely detection of cancer, we see the field of POC technology for cancer detection and treatment undergoing a positive paradigm shift in the foreseeable future.

A Liquid Interfacial SERS Platform on a Nanoparticle Array Stabilized by Rigid Probes for the Quantification of Norepinephrine in Rat Brain Microdialysates

For the reliable determination of trace chemicals in the brain, we created a SERS platform based on a functionalized AuNPs array formed at a liquid/liquid interface in a uniform fashion over a large substrate area through ternary regulations for real-time quantification of trace norepinephrine (NE). The rigid molecule, 4-(thiophen-3-ylethynyl)-benzaldehyde (RP1) was designed and co-assembled at AuNPs with 4-mercaptophenylboronic acid (MPBA) to chemically define NE via dual recognition. Meanwhile, the rigid structure assembly of RP1 and MPBA efficiently fixed the interparticle gap, guaranteeing reproducible SERS analysis. Furthermore, the Raman peak of C≡C group in the silent region was taken as a response element to further improve the accuracy. Combined with microdialysis, this SERS platform was developed for in-the-field testing of NE in rat brain microdialysates following anxiety.

New horizons in the identification of circulating tumor cells (CTCs): An emerging paradigm shift in cytosensors

Circulating tumor cells (CTCs) are cancer cells that are shed from a primary tumor into the bloodstream and function as seeds for cancer metastasis at distant locations. Enrichment and identification methods of CTCs in the blood of patients plays an important role in diagnostic assessments and personalized treatments of cancer. However, the current traditional identification methods not only impact the viability of cells, but also cannot determine the type of cancer cells when the disease is unknown. Hence, new methods to identify CTCs are urgently needed. In this context, many advanced and safe technologies have emerged to distinguish between cancer cells and blood cells, and to distinguish specific types of cancer cells. In this review, at first we have briefly discussed recent advances in technologies related to the enrichment of CTCs, which lay a good foundation for the identification of CTCs. Next, we have summarized state-of-the-art technologies to confirm whether a given cell is indeed a tumor cell and determine the type of tumor cell. Finally, the challenges for application and potential directions of the current identification methods in clinical analysis of CTCs have been discussed.

Modulation of Biological Responses of Tumor Cells Adhered to Poly(2-methoxyethyl acrylate) with Increasing Cell Viability under Serum-Free Conditions

Circulating tumor cells in body fluids are important biomarkers in cancer diagnosis. The culture of tumor cells isolated from body fluids can provide intrinsic information about tumors and can be used to screen for the best anticancer drugs. However, the culture of primary tumor cells has been hindered by their low viability and difficulties in recapitulating the phenotype of primary tumors in in vitro culture. The culture of tumor cells under serum-free conditions is one of the methodologies to maintain the phenotype and genotype of primary tumors. Poly(2-methoxyethyl acrylate) (PMEA)-coated substrates have been investigated to prolong the proliferation of tumor cells under serum-free conditions. In this study, we investigated the detailed behavior and the mechanism of the increase in tumor cell viability after adherence to PMEA substrates. The blebbing formation of tumor cells on PMEA was attributed not to apoptosis but to the low adhesion strength of cells on PMEA. Moreover, blebbing tumor cells showed amoeboid movement and formed clusters with other cells via N-cadherin, leading to an increase in tumor cell viability. Furthermore, the behaviors of tumor cells adhered to PMEA under serum-free conditions were involved in the activation of the PI3K and Rho-associated protein kinase pathways. Thus, we propose that PMEA would be suitable for the development of devices to cultivate primary tumor cells under serum-free conditions for the label-free diagnosis of cancer.

Detection of the effect of polydopamine (PDA)-coated polydimethylsiloxane (PDMS) substrates on the release of H2O2 from a single HeLa cell

Endogenous H₂O₂ generated by a single HeLa cell that was adhered on the PDA-coated PDMS substrates under 25 mM glucose culture conditions was detected using a home-built photoelectric dual detection platform. With PMA as the stimulus, the cell released a small amount of H₂O₂ and its mitochondrial membrane potential (MMP) decrease was smaller, compared with that on the PDMS substrates.

Ultradense Erythrocyte Bionic Layer Used to Capture Circulating Tumor Cells and Plasma-Assisted High-Purity Release

The isolation and detection of rare circulating tumor cells (CTCs) from patient peripheral blood can help early diagnosis of cancer and evaluation of therapeutic outcomes. At present, most of the available strategies for enriching CTCs face serious problems with purity due to the nonspecific interactions between the capture medium and leukocytes. Inspired by the immune evasion ability of homologous red blood cells (RBCs), we modified the tumor-targeting molecule folic acid (FA) on the surface of RBCs by hydrophobic interactions. Under the treatment of polybrene, the charges on the surface of RBCs are neutralized, which reduces the mutual repulsion force. Furthermore, RBCs treated with polyethylene also have excellent deformability, thereby enabling engineered RBCs to form a dense bionic layer on the adhesive glass slide, which can greatly inhibit the nonspecific adhesion of leukocytes. The bionic layer can achieve high-purity enrichment of tumor cells in phosphate-buffered saline (PBS), and we can achieve high-activity release in plasma. The cell count showed over 80% capture efficiency and over 70% release rate, and the purity of CTCs obtained in the artificial blood sample after release was higher than 90%. The RBC bionic surface coating is notably cost-effective and highly applicable for CTC isolation in clinic practice, and thus provides new prospects for designing cell-material interfaces for advanced cell-based biomedical studies in the future.

Aptamer-based nanostructured interfaces for the detection and release of circulating tumor cells

Analysis of circulating tumor cells (CTCs) can provide significant clinical information for tumors, which has proven to be helpful for cancer diagnosis, prognosis monitoring, treatment efficacy, and personalized therapy. However, CTCs are an extremely rare cell population, which challenges the isolation of CTCs from patient blood. Over the last few decades, many strategies for CTC detection have been developed based on the physical and biological properties of CTCs. Among them, nanostructured interfaces have been widely applied as CTC detection platforms to overcome the current limitations associated with CTC capture. Furthermore, aptamers have attracted significant attention in the detection of CTCs due to their advantages, including good affinity, low cost, easy modification, excellent stability, and low immunogenicity. In addition, effective and nondestructive release of CTCs can be achieved by aptamer-mediated methods that are used under mild conditions. Herein, we review some progress in the detection and release of CTCs through aptamer-functionalized nanostructured interfaces.

Tannic Acid (TA)-Functionalized Magnetic Nanoparticles for EpCAM-Independent Circulating Tumor Cell (CTC) Isolation from Patients with Different Cancers

The majority of current methods of isolating circulating tumor cells (CTCs) rely on a biomarker. However, the isolation efficiency may be compromised due to the heterogeneity of CTCs. In this work, a simple and broad-spectrum method is established to efficiently isolate the heterogeneous CTCs from patient blood samples using tannic acid (TA)-functionalized magnetic nanoparticles (MNPs). The TA-functionalized MNPs (MNPs-TA) inhibit the nonspecific adhesion of peripheral blood mononuclear cell (PBMC) and enhance cancer cell capture, resulting from the unique interaction between TA and glycocalyx on cancer cells. The MNPs-TA was demonstrated to effectively capture seven kinds of cancer cells (HeLa, PC-3, T24, MAD-MB-231, MCF-7, HT1080, A549) from artificial samples (62.3-93.7%). Moreover, this epithelial cell adhesion molecule (EpCAM)-independent CTC isolation method was also tested using clinical blood samples from patients with different cancers (21 patients), which may provide a universal tool to detect CTCs in the clinic.

Target-triggered configuration change of DNA tetrahedron for SERS assay of microRNA 122

A surface-enhanced Raman scattering (SERS) method is proposed for the assay of microRNA 122 based on configuration change of DNA tetrahedron. Firstly, a DNA tetrahedron was self-assembled with one vertex labeled with toluidine blue (TB). Then, it was immobilized on the porous Ni/SiO₂@PEI@Au as a SERS platform, which was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). At this time, the DNA tetrahedron was contracted; so, the TB is close to AuNPs and the Raman signal is high. When target microRNA 122 existed, with the nicking enzyme amplification strategy, a great deal of DNA signal chains (S5) was obtained, which can extend the contracted DNA tetrahedron and change it into a three-dimensional DNA tetrahedron. In this case, the TB was far from AuNPs, resulting in a lower Raman signal. Due to the configuration change of DNA tetrahedron, the Raman signal at 1624 cm^-1 (with the excitation wavelength of 633 nm) has a linear relationship with the logarithm concentration of microRNA 122. This SERS assay has high sensitivity for microRNA 122 with a determination range from 0.01 aM to 10 fM and a detection limit of 0.009 aM. The recoveries from spiked samples were in the range 95 to 109%. This SERS strategy is designed based on the target-triggered configuration change of DNA tetrahedron, which can give new insight for DNA structures in bioanalysis. Graphical abstract A sensitive surface-enhanced Raman scattering (SERS) biosensor was developed to detect microRNA 122 using the configuration change of DNA tetrahedron to indirectly control the position of TB and hot spot.