Simplified Rapid Enrichment of CTCs and Selective Recognition Prereduction Enable a Homogeneous ICP-MS Liquid Biopsy Strategy of Lung Cancer

Electrochemical cytosensors for non-invasive liquid biopsy: Detection procedures and technologies for circulating tumor cells

Each year, millions of new cancer cases and cancer-related deaths underscore the urgent need for effective, affordable screening methods. Circulating tumor cells (CTCs), which derived from tumors and shedding into bloodstream, are considered promising biomarkers for liquid biopsy due to their unique biological significance and the substantial volume of supporting research. Among many advanced CTCs detection methods, electrochemical sensing is rapidly developing due to their high selectivity, high sensitivity, low cost, and rapid detection capability, well meeting the growing demand for non-invasive liquid biopsy. This review focuses on the entire procedure of detecting CTCs using electrochemical cytosensors, starting from sample preparation, detailing bio-recognition elements for capturing CTCs, highlighting design strategies of cytosensor, and discussing the prospects and challenges of electrochemical cytosensor applications.

DNAzyme and controllable cholesterol stacking DNA machine integrates dual-target recognition CTCs enable homogeneous liquid biopsy of breast cancer

Although circulating tumor cells (CTCs) have demonstrated considerable importance in liquid biopsy, their detection is limited by low concentrations and complex sample components. Herein, we developed a homogeneous, simple, and high-sensitivity strategy targeting breast cancer cells. This method was based on a non-immunological stepwise centrifugation preprocessing approach to isolate CTCs from whole blood. Precise quantification is achieved through the specific binding of aptamers to the overexpressed mucin 1 (MUC1) and human epidermal growth factor receptor 2 (HER2) proteins of breast cancer cells. Subsequently, DNAzyme cleavage and parallel catalytic hairpin assembly (CHA) reactions on the cholesterol-stacking DNA machine were initiated, which opened the hairpin structures T-Hg2+-T and C-Ag+-C, enabling multiple amplifications. This leads to the fluorescence signal reduction from Hg2+-specific carbon dots (CDs) and CdTe quantum dots (QDs) by released ions. This strategy demonstrated a detection performance with a limit of detection (LOD) of 3 cells/mL and a linear range of 5-100 cells/mL. 42 clinical samples have been validated, confirming their consistency with clinical imaging, pathology findings and the folate receptor (FR)-PCR kit results, exhibiting desirable specificity of 100% and sensitivity of 80.6%. These results highlight the promising applicability of our method for diagnosing and monitoring breast cancer.

A Nanoparticle-Coated Cellulose Acetate Membrane for Highly Efficient, Low-Cost Circulating Tumor Cell Detection

Detecting circulating tumor cells has exhibited great significance in treating cancers since its concentration is an index strongly associated with the development and transfer of the tumor. However, the present commercial method for CTC detection is still expensive, because special antibodies and complicated devices must be used for cell separation and imaging. Hence, it is quite necessary to apply alternative materials and methods to decrease the cost of CTC detection. In this article, we coated a cellulose acetate membrane with nanoparticles formed by the polymerization of melamine and furfural, creating a surface with nanoscale roughness for the highly efficient capture of the sparse CTCs in a blood sample. Subsequently, the CTCs on the surface can be quantitatively detected by colorimetry with the aid of a COF-based nanozyme. The detection limit (LOD) can be as low as 3 cells/mL, which is the lowest LOD among the colorimetric methods to our knowledge. Considering the low cost of fabricating the membrane for CTC capture and the robustness of nanozymes compared with natural enzymes, this CTC detection approach displays great potential to decrease the financial burden of commercial CTC detection.

Multi-targeted nanoarrays for early broad-spectrum detection of lung cancer based on blood biopsy of tumor exosomes

Liquid biopsies utilizing tumor exosomes offer a noninvasive approach for cancer diagnosis. However, validation studies consistently report that in the early stages of cancer, the secretion of exosomes by cancer cells is relatively low, while bodily fluids exhibit a high abundance of other interfering biomolecules. Additionally, target mutations or differences in biomarker expression among various lung cancer subtypes may contribute to detection failures. In this study, we propose a targeted nanoarray-based early cancer diagnostic approach for multiple subtypes of lung cancer. The targeted nanoarray was constructed by modifying five targeting aptamers onto mesoporous silica nanoparticles through the conjugation between amino and carboxyl groups. The flow cytometry experiments demonstrated the specific recognition ability of the targeted nanoarray to tumor exosomes in PBS, even at biomarker expression levels as low as 1.5 %. Moreover, the TEM results indicated that the targeted nanoarray could isolate tumor exosomes in the blood of tumor-bearing mice. Furthermore, the targeted nanoarray could detect tumor exosomes in the blood of various lung cancer bearing mice, including at the early stages of cancer, which has just been established for 7 days. Overall, the targeted nanoarray represents a promising tool for the early detection of various subtypes of lung cancer.

Steric Hindrance-Mediated Enzymatic Reaction Enable Homogeneous Dual Fluorescence Indicators Aptasensing of Hepatocellular Carcinoma CTCs

Circulating tumor cells (CTCs) serve as important biomarkers in the liquid biopsy of hepatocellular carcinoma (HCC). Herein, a homogeneous dual fluorescence indicators aptasensing strategy is described for CTCs in HCC, with the core assistance of a steric hindrance-mediated enzymatic reaction. CTCs in the sample could specifically bind to a 5'-biotin-modified glypican-3 (GPC3) aptamer and remove the steric hindrance formed by the biotin-streptavidin system. This influences the efficiency of the terminal deoxynucleotidyl transferase enzymatic reaction. Then, methylene blue (MB) was introduced to react with the main product poly cytosine (polyC) chain, and trivalent cerium ion (Ce3+) was added to react with the byproduct pyrophosphate to form fluorescent pyrophosphate cerium coordination polymeric nanoparticles. Finally, the CTCs were quantified by dual fluorescence indicators analysis. Under optimized conditions, the linear range was 5 to 104 cells/mL, and the limits of detection reached 2 cells/mL. Then, 40 clinical samples (15 healthy and 25 HCC patients) were analyzed. The receiver operating characteristic curve analysis revealed an area under the curve of 0.96, a sensitivity of 92%, and a specificity of 100%. Therefore, this study established a sensitive and accurate CTCs sensing system for clinical HCC patients, promoting early tumor diagnosis.

Self-Assembled DNA Machine and Selective Complexation Recognition Enable Rapid Homogeneous Portable Quantification of Lung Cancer CTCs

In this study, we systematically investigated the interactions between Cu2+ and various biomolecules, including double-stranded DNA, Y-shaped DNA nanospheres, the double strand of the hybridization chain reaction (HCR), the network structure of cross-linked HCR (cHCR), and small molecules (PPi and His), using Cu2+ as an illustrative example. Our research demonstrated that the coordination between Cu2+ and these biomolecules not only is suitable for modulating luminescent material signals through complexation reactions with Cu2+ but also enhances signal intensities in materials based on chemical reactions by increasing spatial site resistance and local concentration. Building upon these findings, we harnessed the potential for signal amplification in self-assembled DNA nanospheres and the selective complexation modulation of calcein in conjunction with the aptamer targeting mucin 1 as a recognition probe. We applied this approach to the analysis of circulating tumor cells, with the lung cancer cell line A549 serving as a representative model. Our assay, utilizing both a fluorometer and a handheld detector, achieved impressive detection limits of ag/ml and single-cell levels for mucin 1 and A549 cells, and this approach was successfully validated using 46 clinical samples, yielding 100% specificity and 86.5% sensitivity. Consequently, our strategy has paved the way for more portable and precise disease diagnosis.

Biomolecules-mediated electrochemical signals of Cu2+: Y-DNA nanomachines enable homogeneous rapid one-step assay of lung cancer circulating tumor cells

This study presents a straightforward efficient technique for extracting circulating tumor cells (CTCs) and a rapid one-step electrochemical method (45 min) for detecting lung cancer A549 cells based on the specific recognition of mucin 1 using aptamers and the modulation of Cu2+ electrochemical signals by biomolecules. The CTCs separation and enrichment process can be completed within 45 min using lymphocyte separation solution (LSS), erythrocyte lysis solution (ELS), and three centrifugations. Besides, the influence of various biomolecules on Cu2+ electrochemical signals is comprehensively discussed, with DNA nanospheres selected as the medium. Three single-stranded DNA sequences were hybridized to form Y-shaped DNA (Y-DNA), creating DNA nanospheres. Upon specific capture of mucin 1 by the aptamer, most DNA nanospheres could form complexes with Cu2+ (DNA nanosphere-Cu2+), significantly reducing the concentration of free Cu2+. Our approach yielded the limit of detection (LOD) of 2 ag/mL for mucin 1 and 1 cell/mL for A549 cells. 39 clinical blood samples were used for further validation, yielding results closely correlated with pathological, computed tomography (CT) scan findings and folate receptor-polymerase chain reaction (FR-PCR) kits. The receiver operating characteristic (ROC) curve displayed an area under the curve (AUC) value of 0.960, demonstrating 100% specificity and 93.1% sensitivity for the assay. Taken together, our findings indicate that this straightforward and efficient pretreatment and rapid, highly sensitive electrochemical assay holds great promise for liquid biopsy-based tumor detection using CTCs.

Cascade signal amplification using Hg2+-induced oxidation of silver nanoparticles and cation exchange reaction for ICP-MS bioassay

Combining the Hg2+-induced oxidization of silver nanoparticles with the cation exchange reaction between Ag+ and CuS nanoparticles for cascade signal amplification, a sensitive, universal and label-free ICP-MS bioassay for nucleic acids and proteins was developed. By replacing the loop sequence of the T-Hg-T hairpin structure with specific sequences or aptamers to different biomarkers, it has great promise for the early detection of biomarkers potentially for diagnosis of cancerous diseases.