Simultaneous detection of MCF-7 and HepG2 cells in blood by ICP-MS with gold nanoparticles and quantum dots as elemental tags

Quantum dots for bone tissue engineering

In confronting the global prevalence of bone-related disorders, bone tissue engineering (BTE) has developed into a critical discipline, seeking innovative materials to revolutionize treatment paradigms. Quantum dots (QDs), nanoscale semiconductor particles with tunable optical properties, are at the cutting edge of improving bone regeneration. This comprehensive review delves into the multifaceted roles that QDs play within the realm of BTE, emphasizing their potential to not only revolutionize imaging but also to osteogenesis, drug delivery, antimicrobial strategies and phototherapy. The customizable nature of QDs, attributed to their size-dependent optical and electronic properties, has been leveraged to develop precise imaging modalities, enabling the visualization of bone growth and scaffold integration at an unprecedented resolution. Their nanoscopic scale facilitates targeted drug delivery systems, ensuring the localized release of therapeutics. QDs also possess the potential to combat infections at bone defect sites, preventing and improving bacterial infections. Additionally, they can be used in phototherapy to stimulate important bone repair processes and work well with the immune system to improve the overall healing environment. In combination with current trendy artificial intelligence (AI) technology, the development of bone organoids can also be combined with QDs. While QDs demonstrate considerable promise in BTE, the transition from laboratory research to clinical application is fraught with challenges. Concerns regarding the biocompatibility, long-term stability of QDs within the biological environment, and the cost-effectiveness of their production pose significant hurdles to their clinical adoption. This review summarizes the potential of QDs in BTE and highlights the challenges that lie ahead. By overcoming these obstacles, more effective, efficient, and personalized bone regeneration strategies will emerge, offering new hope for patients suffering from debilitating bone diseases.

An Integrated Inertial-Magnetophoresis Microfluidic Chip Online-Coupled with ICP-MS for Rapid Separation and Precise Detection of Circulating Tumor Cells

Circulating tumor cells (CTCs) are recognized as promising targets for liquid biopsy, which play an important role in early diagnosis and efficacy monitoring of cancer. However, due to the extreme scarcity of CTCs and partial size overlap between CTCs and white blood cells (WBCs), the separation and detection of CTCs from blood remain a big challenge. To address this issue, we fabricated a microfluidic chip by integrating a passive contraction-expansion array (CEA) inertial sorting zone and an active magnetophoresis zone with the trapezoidal groove and online coupled it with inductively coupled plasma mass spectrometry (ICP-MS) for rapid separation and precise detection of MCF-7 cells (as a model CTC) in blood samples. In the integrated microfluidic chip, most of the small-sized WBCs can be rapidly removed in the circular CEA inertial sorter, while the rest of the magnetically labeled WBCs can be further captured in the trapezoidal groove under the magnetic field. As a result, the rapid separation of MCF-7 cells from blood samples was achieved with an average recovery of 91.6% at a sample flow rate of 200 μL min-1. The developed online integrated inertial-magnetophoresis microfluidic chip-ICP-MS system has been applied for the detection of CTCs in real clinical blood samples with a fast analysis speed (5 min per 1 mL blood). CTCs were detected in all 24 blood samples from patients with different types of cancer, exhibiting excellent application potential in clinical diagnosis.

ICP-MS based detection method combined with Au NP and Ag NP labeling for bacteremia diagnosis

Bacteremia, as a serious infectious disease, has an increasing incidence and a high mortality rate. Early diagnosis and early treatment are crucial for improving the cure rate. In this work, we proposed an inductively coupled plasma mass spectrometry (ICP-MS)-based detection method combined with gold nanoparticle (Au NP) and silver nanoparticle (Ag NP) labeling for the simultaneous detection of Salmonella and Escherichia coli (E. coli O157:H7) in human blood samples. Salmonella and E. coli O157:H7 were captured by magnetic beads coupled with anti-8G3 and anti-7C2, and then specifically labeled by Au NP-anti-5H12 and Ag NP-anti-8B1 respectively, which were used as signal probes for ICP-MS detection. Under the optimal experimental conditions, the limits of detection of 164 CFU mL-1 for Salmonella, 220 CFU mL-1for E. coli O157:H7 and the linear ranges of 400-80,000 CFU mL-1Salmonella, 400-60,000 CFU mL-1 E. coli O157:H7 were obtained. The proposed method can realize the simultaneous detection of two types of pathogenic bacteria in human whole blood in 3.5 h, showing great potential for the rapid diagnosis of bacteremia in clinic.

Using Functionalized Liposomes to Harvest Extracellular Vesicles of Similar Characteristics in Dermal Interstitial Fluid

Extracellular vesicles (EVs) are used by living cells for the purpose of biological information trafficking from parental-to-recipient cells and vice versa. This back-and-forth communication is enabled by two distinct kinds of biomolecules that constitute the cargo of an EV: proteins and nucleic acids. The proteomic-cum-genetic information is mediated by the physiological state of a cell (healthy or otherwise) as much as modulated by the biogenesis pathway of the EV. Therefore, in mirroring the huge diversities of human communications, the proteins and nucleic acids involved in cell communications possess seemingly near limitless diversities, and it is this characteristic that makes EVs so highly heterogeneous. Currently, there is no simple and reliable tool for the selective capture of heterogeneous EVs and the delivery of their undamaged cargo for research in extracellular protein mapping and spatial proteomics studies. Our work is a preliminary attempt to address this issue. We demonstrated our approach by using antibody functionalized liposomes to capture EVs from tumor and healthy cell-lines. To characterize their performance, we presented fluorescence and nanoparticle tracking analysis (NTA) results, TEM images, and Western blotting analysis for EV proteins. We also extracted dermal interstitial fluid (ISF) from healthy individuals and used our functionalized synthetic vesicle (FSV) method to capture EVs from their proteins. We constructed three proteomic sets [EV vs ISF, (FSV+EV) vs ISF, and (FSV+EV) vs EV] from the EV proteins and the free proteins harvested from ISF and compared their differentially expressed proteins (DEPs). The performance of our proposed method is assessed via an analysis of 1095 proteins, together with volcano plots, heatmap, GO annotation, and enriched KEGG pathways and organelle localization results of 213 DEPs.

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

The effective enrichment and hypersensitivity analysis of circulating tumor cells (CTCs) in clinical whole blood samples are highly significant for clinical tumor liquid biopsy. In this study, we established an easy operation and affordable CTCs extraction technique while simultaneously performing the homogeneous inductively coupled plasma mass spectrometry (ICP-MS) determination of CTCs in lung cancer clinical samples based on selective recognition reactions and prereduction phenomena. Our strategy allowed for the pretreatment of whole blood samples in less than 45 min after step-by-step centrifugation, which only required lymphocyte separation solution and erythrocyte lysate. Furthermore, a three-stage signal amplification system consisting of catalytic hairpin assembly (CHA), selective recognition for C-Ag+-C structures and Ag+ of copper sulfide nanoparticles (CuS NPs), and prereduction of Hg2+ through ascorbic acid (AA) was constructed by using mucin 1 as the CTCs marker and the aptamer for identification probes. In optimal conditions, the detection limits of ICP-MS were as low as 0.3 ag/mL for mucin 1 and 0.25 cells/mL for A549 cells. This method analyzed CTCs in 58 clinical samples quantitatively, and the results were consistent with clinical CT images and pathological findings. The area under the curve (AUC) value of the receiver operating characteristic (ROC) curve was 0.957, which provided a specificity of 100% and a sensitivity of 91.5% for the assay. Therefore, the simplicity of the extraction method, the accessibility, and the high sensitivity of the assay method make the strategies attractive for clinical CTCs testing applications.

Single Cell Phenotypic Analysis for Cancer Stem Cell Identification by Dual-Isotope ICP-QMS

Single cell phenotypic analysis is significant for clinical diagnosis, treatment, and prognosis of cancer. Accurate differentiation of cancer stem cell (CSC) subpopulations from a large number of cancer cells may become a cancer surveillance tool and provide important implications for the development of new CSC-targeted therapy strategies. Herein, we report a new approach based on dual-isotope inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) for single cell phenotypic analysis. High-throughput single cell sampling was achieved by a spiral channel microfluidic chip for cell focusing and alignment, and single cell analysis was performed with time-resolved ICP-QMS by identifying the highly specific probes. This enables the monitoring of two surface protein markers (EpCAM and MUC1) of three cell types, i.e., HeLa, MCF-7, and HepG2, at single cell level. The analysis of breast cancer stem cells further confirmed its capability in distinguishing rare cell phenotypes. The present study provides promising possibilities for adopting ICP-QMS in biomedical investigations in terms of cell typing, stemness identification of tumor cells, and cell heterogeneity analysis.

Dual-potential electrochemiluminescence cytosensor based on a metal-organic framework and ABEI-PEI-Au@AgNPs for the simultaneous determination of phosphatidylserine and epidermal growth factor receptors on an apoptotic cell surface

A new electrochemiluminescence (ECL) cytosensor is proposed for the simultaneous determination of phosphatidylserine (PS) and epidermal growth factor receptor (EGFR) based on the ECL signals of metal-organic framework-5 (MOF-5) loaded CdS quantum dots and N-(aminobutyl)-N-(ethylisoluminol)-polyethylenimine capped Au and Ag nanoparticles. Apoptosis promotes the exposure of PS and reduces the expression of EGFR in cell membranes. Two spatially resolved areas on dual-disk glassy carbon electrodes were designed to eliminate the interference from different ECL probes. Using HepG2 cells treated with resveratrol to induce apoptosis, the cytosensor exhibited high sensitivity, simplicity, and high reproducibility, demonstrating its potential in drug screening and rapid apoptotic cell detection. The strategy reported provides a promising platform for the highly sensitive cytosensing and convenient screening of clinically relevant anticancer drugs.

Recent advances in micro-/nanostructure array integrated microfluidic devices for efficient separation of circulating tumor cells

Circulating tumor cells (CTCs) released from the primary tumor to peripheral blood are promising targets for liquid biopsies. Their biological information is vital for early cancer detection, efficacy assessment, and prognostic monitoring. Despite the tremendous clinical applications of CTCs, development of effective separation techniques are still demanding. Traditional separation methods usually use batch processing for enrichment, which inevitably destroy cell integrity and affect the complete information acquisition. Considering the rarity and heterogeneity of CTCs, it is urgent to develop effective separation methods. Microfluidic chips with precise fluid control at the micron level are promising devices for CTC separation. Their further combination with micro-/nanostructure arrays adds more biomolecule binding sites and exhibit unique fluid barrier effect, which significantly improve the CTC capture efficiency, purity, and sensitivity. This review summarized the recent advances in micro-/nanostructure array integrated microfluidic devices for CTC separation, including microrods, nanowires, and 3D micro-/nanostructures. The mechanisms by which these structures contribute to improved capture efficiency are discussed. Two major categories of separation methods, based on the physical and biological properties of CTCs, are discussed separately. Physical separation includes the design and preparation of micro-/nanostructure arrays, while chemical separation additionally involves the selection and modification of specific capture probes. These emerging technologies are expected to become powerful tools for disease diagnosis in the future.

Label-free detection and enumeration of rare circulating tumor cells by bright-field image cytometry and multi-frame image correlation analysis

Identification and enumeration of circulating tumor cells (CTCs) in peripheral blood are proved to correlate with the progress of metastatic cancer and can provide valuable information for diagnosis and monitoring of cancer. Here, we introduce a bright-field image cytometry (BFIC) technique, assisted by a multi-frame image correlation (MFIC) algorithm, as a label-free approach for tumor cell detection in peripheral blood. For this method, images of flowing cells in a wide channel were continuously recorded and cell types were determined simultaneously using a deep neural network of YOLO-V4 with an average precision (AP) of 98.63%, 99.04%, and 98.95% for cancer cell lines HT29, A549, and KYSE30, respectively. The use of the wide microfluidic channel (400 μm width) allowed for a high throughput of 50 000 cells per min without clogging. Then erroneous or missed cell classifications caused by imaging angle differences or accidental misinterpretations in single frames were corrected by the multi-frame correlation analysis. This further improved the AP to 99.40%, 99.52%, and 99.47% for HT29, A549, and KYSE30, respectively. Meanwhile, cell counting was also accomplished in this dynamic process. Moreover, our imaging cytometry method can readily detect as few as 10 tumor cells from 100 000 white blood cells and was unaffected by the EMT process. Furthermore, CTCs from 8 advanced-stage cancer clinical samples were also successfully detected, while none for 6 healthy control subjects. Although this method is implemented for CTCs, it can also be used for the detection of other rare cells.

Simple Amplifier Coupled with a Lanthanide Labeling Strategy for Multiplexed and Specific Quantification of MicroRNAs

Inductively coupled plasma-mass spectrometry (ICP-MS) with elemental labeling is a promising strategy for multiplex microRNA (miRNA) analysis. However, it is still challenging for specific analysis of multiple miRNAs with high homology, and the development of multiplex assays is always limited by the complexity of the sequence design. Herein, a simple and direct ICP-MS-based assay was developed for the simultaneous detection of three miRNAs by combining the lanthanide labeling strategy with entropy-driven catalytic (EDC) amplification. Owing to the specificity of EDC for nucleic acid recognition, it is able to differentiate miRNAs with single-base mutation in each EDC circuit. A universal biotin-labeled DNA strand was designed to hybridize with the DNA substrates for three EDC circuits, targeting miRNA-21, miRNA-155, and miRNA-10b, respectively. All the substrates were loaded on the surface of streptavidin magnetic beads. In the presence of target miRNA, the EDC reaction was initiated, and EDC substrates were dissociated, continuously releasing reporter strands that were labeled with lanthanides (Tb/Ho/Lu). After magnetic separation, the supernatant containing the released reporter strands was introduced into an ICP-MS system for simultaneous detection of ¹⁵⁹Tb/¹⁶⁵Ho/¹⁷⁵Lu and quantification of miRNA-21, miRNA-155, and miRNA-10b, respectively. The limits of detection were 7.4, 7.5, and 11 pmol L^-1 for miRNA-21, miRNA-155, and miRNA-10b, respectively. Overall, this study provides a powerful strategy for simultaneous quantification of multiple miRNAs, with the advantages of flexible probe design, good sensitivity, and excellent specificity.

Facets of ICP-MS and their potential in the medical sciences—Part 2: nanomedicine, immunochemistry, mass cytometry, and bioassays

Inductively coupled–plasma mass spectrometry (ICP-MS) has transformed our knowledge on the role of trace and major elements in biology and has emerged as the most versatile technique in elemental mass spectrometry. The scope of ICP-MS has dramatically changed since its inception, and nowadays, it is a mature platform technology that is compatible with chromatographic and laser ablation (LA) systems. Over the last decades, it kept pace with various technological advances and was inspired by interdisciplinary approaches which endorsed new areas of applications. While the first part of this review was dedicated to fundamentals in ICP-MS, its hyphenated techniques and the application in biomonitoring, isotope ratio analysis, elemental speciation analysis, and elemental bioimaging, this second part will introduce relatively current directions in ICP-MS and their potential to provide novel perspectives in the medical sciences. In this context, current directions for the characterisation of novel nanomaterials which are considered for biomedical applications like drug delivery and imaging platforms will be discussed while considering different facets of ICP-MS including single event analysis and dedicated hyphenated techniques. Subsequently, immunochemistry techniques will be reviewed in their capability to expand the scope of ICP-MS enabling analysis of a large range of biomolecules alongside elements. These methods inspired mass cytometry and imaging mass cytometry and have the potential to transform diagnostics and treatment by offering new paradigms for personalised medicine. Finally, the interlacing of immunochemistry methods, single event analysis, and functional nanomaterials has opened new horizons to design novel bioassays which promise potential as assets for clinical applications and larger screening programs and will be discussed in their capabilities to detect low-level proteins and nucleic acids.

High-Throughput Recognition of Tumor Cells Using Label-Free Elemental Characteristics Based on Interpretable Deep Learning

With cancer seriously hampering the increasing life expectancy of people, developing an instant diagnostic method has become an urgent objective. In this work, we developed a label-free laser-induced breakdown spectroscopy (LIBS) method for high-throughput recognition of tumor cells. LIBS spectra were straightly collected from cells dropped on a silicon substrate and built into a deep learning model for simultaneous classification of various cancers. To interpret the result of the deep learning algorithm, gradient-weighted class activation mapping was utilized to a one-dimensional convolution neural network (1D-CNN), and the saliency maps thus obtained amplified the differences between the spectra of cell lines. Overall results showed that the 1D-CNN algorithms achieved a mean sensitivity of 94.00%, a mean specificity of 98.47%, and a mean accuracy of 97.56%. Thus, the proposed method performed satisfactorily and is seen as an interpretable classification process for cancer cell lines.

Antifouling Electrochemical Biosensor Based on the Designed Functional Peptide and the Electrodeposited Conducting Polymer for CTC Analysis in Human Blood

Circulating tumor cells (CTCs) are considered reliable cancer biomarkers for the liquid biopsy of many types of tumors. The direct detection of CTCs in human blood with normal biosensors, however, remains challenging because of severe biofouling in blood that contains various proteins and a large number of cells. Herein, we report the construction of an antifouling electrochemical biosensor capable of assaying CTCs directly in blood, based on a designed multifunctional peptide and the electrodeposited conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT). The designed peptide possesses antifouling capability in complex biological media and specific recognition ability to capture breast cancer cells MCF-7. Meanwhile, electrodeposited PEDOT can promote electron transfer at the sensing interface, improve the signal-to-noise ratio for the detection, and thus enhance the sensitivity of the biosensor. The integration of the multifunctional peptide and conducting polymer PEDOT ensures that the developed biosensor is able to perform directly in blood samples without purification or separation. The antifouling electrochemical biosensor for the detection of MCF-7 cells exhibits a wide linear range over 4 orders, with a limit of detection (LOD) of 17 cells mL^-1. More interestingly, even when performing in 25% human blood, the biosensor still retains a linear response with an LOD of 22 cells mL^-1, without suffering significantly from biofouling in real blood. This work provides a promising strategy for the direct analysis of CTCs in human blood without a complicated pretreatment, and it may find practical application in the liquid biopsy of cancers.

A homogeneous nucleic acid assay for simultaneous detection of SARS-CoV-2 and influenza A (H3N2) by single-particle inductively coupled plasma mass spectrometry

In recent years, single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) has become a powerful tool for biological quantitative analysis. Homogeneous analysis method requires no separation and washing steps, which is suited for the analysis of highly infectious pathogens, so as to reduce the risk of infection during the operation. SARS-CoV-2 spreads all over the world, and its early infection symptoms are similar to influenza, which brings inconvenience to triage. Therefore, developing novel analytical method for simultaneous detection of multiple viral nucleic acids is essential. Taking the advantages of SP-ICP-MS and homogeneous analysis strategy, a SP-ICP-MS homogeneous nucleic acid assay by using gold nanoparticles (Au NPs) and silver nanoparticles (Ag NPs) probes was established for simultaneous sensitive analysis of SARS-CoV-2 and influenza A (H3N2). In the present of target SARS-CoV-2 or H3N2 nucleic acids, corresponding Au NPs or Ag NPs probes form larger aggregates, resulting in increased pulse signal intensity and reduced pulse signal frequency of the corresponding NPs in SP-ICP-MS measurement. In this assay, the reaction system of Au NPs and Ag NPs probes does not interfere with each other, and there was no separation and washing procedure, which facilitates operation, saves the analysis time, and improves the analysis efficiency. The linear range of this method is 5-1000 pmol L^-1, with low-level limits of quantification of target nucleic acid. The developed SP-ICP-MS simultaneous homogeneous detection method has a good potential for detecting nucleic acid, protein, cell and other biological samples by changing different modification sequences on the NPs probes.

Analysis of arsenic binding proteins in HepG2 cells based on a biotinylated phenylarsenite probe

For a deep understanding of arsenic's mutagenicity, carcinogenicity and teratogenicity, the elucidation of arsenic binding proteins in organisms is a necessary prerequisite. Herein, a biotinylated phenylarsenite (Bio-PAO(III)) probe was synthesized for in situ binding to arsenic binding proteins in HepG2 cells. The Bio-PAO(III)-arsenic binding proteins complexes were captured by the prepared streptavidin-magnetic beads (SA-MBs) by specific interaction of biotin-SA. After magnetic separation, the arsenic binding proteins in the eluent was separated by sodium dodecyl sulfate-polyacrylamide - gel electrophoresis, and the in-gel tryptic digested protein bands were subjected to capillary high performance liquid chromatography coupled with electrospray ionization mass spectrometry analysis. 32 kinds of arsenic binding proteins were identified in HepG2 cells, which could be divided into three groups, structure proteins, enzymes related with tricarboxylic acid cycle and fatty synthesis and transcriptional regulator. Poly [ADP-ribose] polymerase 1 and general transcription factor IIH subunit 1 were identified to bind with arsenicals, which may affect the process of nucleotide excision repair in HepG2 cells.

Aptamer Embedded Arch-Cruciform DNA Assemblies on 2-D VS2 Scaffolds for Sensitive Detection of Breast Cancer Cells

Arch-cruciform DNA are self-assembled on AuNPs/VS₂ scaffold as a highly sensitive and selective electrochemical biosensor for michigan cancer foundation-7 (MCF-7) breast cancer cells. In the construction, arch DNA is formed using two single-strand DNA sequences embedded with the aptamer for MCF-7 cells. In the absence of MCF-7 cells, a cruciform DNA labeled with three terminal biotin is bound to the top of arch DNA, which further combines with streptavidin-labeled horseradish peroxidase (HRP) to catalyze the hydroquinone-H₂O₂ reaction on the electrode surface. The presence of MCF-7 cells can release the cruciform DNA and reduce the amount of immobilized HRP, thus effectively inhibiting enzyme-mediated electrocatalysis. The electrochemical response of the sensor is negatively correlated with the concentration of MCF-7 cells, with a linear range of 10~1 × 10⁵ cells/mL, and a limit of detection as low as 5 cells/mL (S/N = 3). Through two-dimensional materials and enzyme-based dual signal amplification, this biosensor may pave new ways for the highly sensitive detection of tumor cells in real samples.

Multivalent Duplexed-Aptamer Networks Regulated a CRISPR-Cas12a System for Circulating Tumor Cell Detection

Although circulating tumor cells (CTCs) have great potential to act as the mini-invasive liquid biopsy cancer biomarker, a rapid and sensitive CTC detection method remains lacking. CRISPR-Cas12a has recently emerged as a promising tool in biosensing applications with the characteristic of fast detection, easy operation, and high sensitivity. Herein, we reported a CRISPR-Cas12a-based CTC detection sensor that is regulated by the multivalent duplexed-aptamer networks (MDANs). MDANs were synthesized on a magnetic bead surface by rolling circle amplification (RCA), which contain multiple duplexed-aptamer units that allow structure switching induced by cell-binding events. The presence of target cells can trigger the release of free "activator DNA" from the MDANs structure to activate the downstream CRISPR-Cas12a for signal amplification. Furthermore, the 3D DNA network formed by RCA products also provided significantly higher sensitivity than the monovalent aptamer. As a proof-of-concept study, we chose the most widely used sgc8 aptamer that specifically recognizes CCRF-CEM cells to validate the proposed approach. The MDANs-Cas12a system could afford a simple and fast CTC detection workflow with a detection limit of 26 cells mL^-1. We also demonstrated that the MDANs-Cas12a could directly detect the CTCs in human blood samples, indicating a great potential of the MDANs-Cas12a in clinical CTC-based liquid biopsy.

Dual-Multivalent-Aptamer-Conjugated Nanoprobes for Superefficient Discerning of Single Circulating Tumor Cells in a Microfluidic Chip with Inductively Coupled Plasma Mass Spectrometry Detection

The efficient recognition of circulating tumor cells (CTCs) with an aptamer probe confers numerous benefits; however, the stability and binding affinity of aptamers are significantly hampered in real biological sample matrices. Inspired by the efficient preying mechanism by multiplex tubing feet and endoskeletons of sea urchins, we engineered a superefficient biomimetic single-CTC recognition platform by conjugating dual-multivalent-aptamers (DMAs) Sgc8 and SYL3C onto AuNPs to form a sea urchin-like nanoprobe (sea urchin-DMA-AuNPs). Aptamers Sgc8 and SYL3C selectively bind with the biomarker proteins PTK7 and EpCAM expressed on the surface of CTCs. CTCs were captured with 100% efficiency, followed by sorting on a specially designed multifunctional microfluidic configuration, integrating a single-CTC separation unit and a hydrodynamic filtrating purification unit. After sorting, background-free analysis of biomarker proteins in single CTCs was undertaken with inductively coupled plasma mass spectrometry by measuring the amount of ¹⁹⁷Au isotope in sea urchin-DMA-AuNPs. With respect to a single-aptamer nanoprobe/-interface, the dual-aptamer nanoprobe improves the binding efficiency by more than 200% (K_d < 0.35 nM). The microchip facilitates the recognition of single CTCs with a sorting separation rate of 93.6% at a flow rate of 60 μL min^-1, and it exhibits 73.8 ± 5.0% measurement efficiency for single CTCs. The present strategy ensures the manipulation and detection of a single CTC in 100 μL of whole blood within 1 h.

A simple method to assay tumor cells based on target-initiated steric hindrance

We have proposed a simple electrochemical method in this work for the assay of tumor cells through their own steric hindrance effect. Specifically, tumor cells can block the catalysis of terminal deoxynucleotidyl transferase to the aptamer previously immobilized on the electrode surface. By making use of the hindrance effect, cancer cells can be quantitatively analyzed in the range from 1.6 × 102 to 1.6 × 106 cells per mL without complicated design or cumbersome operation, while the detection limit can be about 53 cells per mL. This method can also show satisfactory performance in complex environments, indicating its potential in clinical application.

Recent Development of Nanomaterials-Based Cytosensors for the Detection of Circulating Tumor Cells

The accurate analysis of circulating tumor cells (CTCs) holds great promise in early diagnosis and prognosis of cancers. However, the extremely low abundance of CTCs in peripheral blood samples limits the practical utility of the traditional methods for CTCs detection. Thus, novel and powerful strategies have been proposed for sensitive detection of CTCs. In particular, nanomaterials with exceptional physical and chemical properties have been used to fabricate cytosensors for amplifying the signal and enhancing the sensitivity. In this review, we summarize the recent development of nanomaterials-based optical and electrochemical analytical techniques for CTCs detection, including fluorescence, colorimetry, surface-enhanced Raman scattering, chemiluminescence, electrochemistry, electrochemiluminescence, photoelectrochemistry and so on.

A dual-functional magnetic microsphere for ICP-MS quantification and fluorescence imaging of matrix metalloproteinase 2 in cell secretion

Matrix metalloproteinase 2 (MMP2) plays an important role in tumor growth, invasion and metastasis. In this work, a dual-functional magnetic microsphere probe was designed for ICP-MS quantification and fluorescence imaging of MMP2 in cell secretion. In the designed probe, a NH₂-peptide (-FAM)-biotin was used as a bridge for the combination of carboxylated magnetic beads (MBs-COOH) and streptavidin functionalized gold nanoparticle (Au NP-SA). Initially, the fluorescence of FAM was quenched by Au NP. Since the NH₂-peptide (-FAM)-biotin had a MMP2-specifically recognized sequence, the peptide was specifically cleaved in the presence of MMP2, thus releasing Au NP for the ICP-MS quantification of MMP2 and turning on the fluorescence of FAM for the fluorescence imaging of MMP2. Under the optimal experimental conditions, a linear range of 0.05-50 ng mL^-1 and a limit of detection of 0.02 ng mL^-1 were obtained for MMP2. The relative standard deviation (n = 7, c = 0.1 ng mL^-1) of the proposed method was 5.4%. With good sensitivity and good accuracy, the proposed method realized the quantification and imaging of MMP2 in A549 cell secretion. The proposed method was applied to monitor the expression of MMP2 in the A549 cell secretion under the stimulation of Cd²⁺, providing a new detection strategy in the study of MMP2-related life process.

Microsatellite Instability in Colorectal Cancer Liquid Biopsy-Current Updates on Its Potential in Non-Invasive Detection, Prognosis and as a Predictive Marker

Colorectal cancer (CRC) is the third most commonly-diagnosed cancer in the world and ranked second for cancer-related mortality in humans. Microsatellite instability (MSI) is an indicator for Lynch syndrome (LS), an inherited cancer predisposition, and a prognostic marker which predicts the response to immunotherapy. A recent trend in immunotherapy has transformed cancer treatment to provide medical alternatives that have not existed before. It is believed that MSI-high (MSI-H) CRC patients would benefit from immunotherapy due to their increased immune infiltration and higher neo-antigenic loads. MSI testing such as immunohistochemistry (IHC) and PCR MSI assay has historically been a tissue-based procedure that involves the testing of adequate tissue with a high concentration of cancer cells, in addition to the requirement for paired normal tissues. The invasive nature and specific prerequisite of such tests might hinder its application when surgery is not an option or when the tissues are insufficient. The application of next-generation sequencing, which is highly sensitive, in combination with liquid biopsy, therefore, presents an interesting possibility worth exploring. This review aimed to discuss the current body of evidence supporting the potential of liquid biopsy as a tool for MSI testing in CRC.

Signal amplification strategies for clinical biomarker quantification using elemental mass spectrometry

The current trends in modern medicine towards early diagnosis, or even prognosis, of different diseases have brought about the need for the corresponding biomarker detection at ever lower levels in really complex matrices. To do so, it is necessary to use proper extremely sensitive detection techniques such as elemental mass spectrometry. However, target labelling with metals for subsequent sensitive ICP-MS detection falls short nowadays even if resorting to inorganic nanoparticles containing a high number of detectable elements. Thus, new amplification strategies are being proposed to face this analytical challenge that will be critically discussed in this paper. Fundamentals of different novel strategies developed to achieve signal amplification and sensitive elemental mass spectrometry detection are here discussed. Some representative examples of relevant clinical applications are highlighted, along with future prospects and challenges.

Thermo-responsive imprinted hydrogel with switchable sialic acid recognition for selective cancer cell isolation from blood

In this work, a sialic acid (SA)-imprinted thermo-responsive hydrogel layer was prepared for selective capture and release of cancer cells. The SA-imprinting process was performed at 37 °C using thermo-responsive functional monomer, thus generating switchable SA-recognition sites with potent SA binding at 37 °C and weak binding at a lower temperature (e.g., 25 °C). Since SA is often overexpressed at the glycan terminals of cell membrane proteins or lipids, the SA-imprinted hydrogel layer could be used for selective cancer cell recognition. Our results confirmed that the hydrogel layer could efficiently capture cancer cells from not only the culture medium but also the real blood samples. In addition, the captured cells could be non-invasively released by lowing the temperature. Considering the non-invasive processing mode, considerable capture efficiency, good cell selectivity, as well as the more stable and durable SA-imprinted sites compared to natural antibodies or receptors, this thermo-responsive hydrogel layer could be used as a promising and general platform for cell-based cancer diagnosis.

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Thermo-responsive sialic acid (SA)-imprinted hydrogel layer was prepared.

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The hydrogel layer could efficiently and selective capture cancer cells at 37 °C.

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The captured cancer cells could be released at a lower temperature (e.g., 25 °C).

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The hydrogel layer could be used for capture and release cancer cells from blood.

Construction of a Ternary Complex Based DNA Logic Nanomachine for a Highly Accurate Imaging Analysis of Cancer Cells

Due to the complexity and variability of the cellular metabolic process and the physiological environment inside and outside the cell, higher requirements are needed on the application of DNA molecular logic gate in cell analysis. In addition, heterogeneity of tumor cells tends to lead to false positives in the clinical diagnosis of a single target, even those with the same cancer type. To address these issues above, we have developed a novel DNA molecular logic gate responsive nanomachine for bispecific recognition and computation of cell membranes. Only when two membrane proteins, MUC1 and EpCAM as model proteins, exist simultaneously, the DNA molecular logic gate can be activated to perform "AND" logic operation and generate amplified "ON" fluorescence signal from the cell membrane. Therefore, our proposed dual-specific "recognition-biocomputing" DNA molecular logic gate has achieved highly accurate imaging analysis of dual-target membrane proteins in situ. Furthermore, the logic gate responsive DNA nanomachine can also be used to analyze target cells in complex cell samples with excellent specificity, which will meet the needs of biomedicine and their application in clinical diagnosis and provide new tools for the biomedical application of DNA molecular logic gates in complex cell systems.

A Multifunctional Platform for the Capture, Release, And Enumeration of Circulating Tumor Cells Based on Aptamer Binding, Nicking Endonuclease-Assisted Amplification, And Inductively Coupled Plasma Mass Spectrometry Detection

Inductively coupled plasma mass spectrometry (ICP-MS) combined with element tags has been well designed and extensively applied in cell enumeration. It possesses superior quantitative capability, strong resistance to matrix interference, multiplex detection capability but destructive characteristic. Herein, we constructed an ICP-MS based multifunctional platform for capture, nondestructive enumeration, and release of circulating tumor cells (CTCs). Aptamer on capture probe recognized Mucin 1 (MUC1) on membrane of MCF-7 cells specifically, thus the cells were captured by probe and the Initiator originally hybridized with Aptamer was substituted by MUC1 and released into solution. Then the released Initiator was separated from the captured cells and hybridized with Tb labeled Substrate on detection probe to release a large amount of nicked Tb fragments through the nicking endonuclease assisted amplification for subsequent ICP-MS detection. Meanwhile, cells captured by probe were released by nuclease digestion for further reculture. Such a strategy effectively avoids CTCs destruction resulted from ICP-MS enumeration, increases the detection sensitivity of ICP-MS by involving nicking endonuclease assisted amplification, and realizes cell recovery for further analysis. A limit of detection of 87 MCF-7 cells and a linear range of 250-10 000 MCF-7 cells were realized for ICP-MS enumeration. A cell recovery of 52.7% (with capture and release efficiency of 63.9 and 82.5%, respectively) and a viability of 74.3% were obtained, meanwhile the released cells exhibited strong proliferation ability. This multifunctional platform for CTCs capture, enumeration, and release has great applicable potential in early diagnosis and individual treatment for cancer.

Magneto-controlled aptasensor for simultaneous detection of ochratoxin A and fumonisin B1 using inductively coupled plasma mass spectrometry with multiple metal nanoparticles as element labels

The simultaneous detection of multiple mycotoxins is important for food safety. Here, a magneto-controlled aptasensor for quantitative analysis of ochratoxin A (OTA) and fumonisin B1 (FB1) using inductively coupled plasma mass spectrometry (ICP-MS) with multiple metal nanoparticles as element labels was proposed. Firstly, the OTA aptamer (Apt1) and the FB1 aptamer (Apt2) immobilized on the magnetic beads (MBs) were hybridized with probe DNA1-CdSe quantum dots (pDNA1-QDs) and probe DNA2-Ag nanoparticles (pDNA2-Ag NPs) labels, producing the MBs-Apt1-pDNA1-QDs and MBs-Apt2-pDNA2-Ag NPs conjugates, respectively. Then, the MBs-Apt1-OTA and MBs-Apt2-FB1 conjugates were generated with the addition of targets, resulting the pDNA1-QDs and pDNA2-Ag NPs labels released into the solutions. Finally, the signal intensities of ¹¹¹Cd and ¹⁰⁷Ag were detected by ICP-MS, achieving limits of detection of 0.10 and 0.30 ng mL^-1 for OTA and FB1, respectively. The assay showed high specificity and succeeded in wheat flour. The method provides an ideal model for sensitive analysis of multiple mycotoxins in food samples.

Quantitative Analysis of Salmonella typhimurium Based on Elemental-Tags Laser-Induced Breakdown Spectroscopy

Current rapid bacterial detection methods are dedicated to the classification and identification of bacteria. However, there is still a lack of a method for specific quantitative analysis of certain bacteria. In this work, a method based on elemental-tags laser-induced breakdown spectroscopy (ETLIBS) was developed for the rapid and specific quantitative analysis of Salmonella typhimurium (S. ty). Elemental tags were first synthesized by assembling copper nanoparticles (CuNPs) with poly(thymine) (poly-T) template that linked with the aptamer sequence. Under the specific recognition of the aptamer, S. ty can be fully combined with the elemental tags within 30 min to achieve labeling. Afterward, the silicon nanowires (SiNWs) array modified with Au@Ag nanoparticles (SiNWs-Au@Ag) was employed to capture S. ty in 30 min. Attributed to the rapid analysis superiority of ETLIBS mapping, 100 spectra of SiNWs-Au@Ag/S. ty/CuNPs can be obtained in 5 min. It was found that the peak area of the Cu(I) atomic emission line at 324.75 nm fitted by the Voigt profile was linearly related to the bacterial concentration in the range of 10²-10⁶ CFU/mL(R² = 0.978). Furthermore, ETLIBS mapping achieved a low limit of detection (LOD) of 61 CFU/mL and showed good selectivity to S. ty compared with other bacteria. Besides, the method exhibited preeminent detection performance in spiked samples with the recoveries of 87-113%. With the advantages of rapidity, high efficiency, and specificity, the proposed method is expected to be a powerful tool for bacterial detection.

Biomimetic immunomagnetic gold hybrid nanoparticles coupled with inductively coupled plasma mass spectrometry for the detection of circulating tumor cells

Immunomagnetic beads are important tools for the isolation and detection of circulating tumor cells (CTCs). However, the current immunomagnetic bead technique provides poor CTC separation purity due to nonspecific binding of background cells. Furthermore, immunomagnetic beads have not been appropriately functionalized for enabling CTC analysis and quantification. In this work, bimetallic magnetic gold nanoparticles were prepared and coated with leukocyte membranes to form leukocyte membrane-camouflaged nanoparticles. After conjugation with the antibody of epithelial cell adhesion molecule (EpCAM), the biomimetic immunomagnetic gold nanoparticles (CM-Fe₃O₄@Au-Ab) showed a high specific recognition ability on mock (EpCAM-positive) CTCs and a reduced interaction with leukocytes. We subsequently optimized the conditions for CTC separation, including the concentration of nanoparticles and the incubation time. Under the optimized conditions, CM-Fe₃O₄@Au-Ab exhibited high CTC capture efficiency with negligible background cell binding in mock clinical blood samples. More importantly, gold probes were tagged on the surface of these separated CTCs. When coupled with ICP-MS analysis, the number of CTCs and gold signals exhibited a good linear relationship, and a low limit of detection was obtained, enabling us to estimate the number of CTCs in blood samples. Hence, we expected that CM-Fe₃O₄@Au-Ab could provide an opportunity to surmount the limitations of current CTC detection.

Thiol inhibition of Hg cold vapor generation in SnCl2/NaBH4 system: A homogeneous bioassay for H2O2/glucose and butyrylcholinesterase/pesticide sensing by atomic spectrometry

Recently, the use of atomic spectrometry (AS) for biochemical analysis has attracted considerable attention due to its high sensitivity, selectivity and anti-interference ability. In this work, we conducted a detailed study on a phenomenon of thiol inhibition of mercury (Hg²⁺) cold vapor generation (CVG) and found _L-cysteine (_L-Cys), glutathione (GSH), dithiothreitol, N-Acetyl-L-cysteine, 3-mercaptopropionic acid, β-mercaptoethanol, and NaI can inhibit the CVG of Hg²⁺, while EDTA has no inhibitory effect. Furthermore, changing the content of -SH can effectively adjust the CVG atomic fluorescence spectrometer (CVG-AFS) signal of Hg²⁺. As as a consequence, an AS-based homogeneous bioassay was constructed by adjusting the oxidation ratio and production quantity of -SH in the system. The quantitative analysis of the system was demonstrated by using AFS as a representative detector. Hydrogen peroxide (H₂O₂) and glucose were used as representative analytes for the validation of Hg²⁺ atomic fluorescence signal turn-off strategy, and butyrylcholinesterase (BChE) as well as parathion (organophosphorus pesticides, OPs) as utilized as representative targets for the signal turn-on strategy. Under optimal experimental conditions, the homogeneous CVG-AFS sensor can be successfully used to detect 3 μM H₂O₂, 30 μM glucose, 0.25 U/L BChE, and 0.4 μg/mL parathion. In addition, the detection results of glucose and BChE in human serum samples agreed well with those obtained by using glucometer and kit, showing the promising potential of this method for practical applications. Therefore, this work provides a perspective for the construction of AS-based homogeneous bioassays and shows great potential for the detection of biomarkers.

Detection of HER2+ Breast Cancer Cells using Bioinspired DNA-Based Signal Amplification

Circulating tumor cells (CTC) are promising biomarkers for metastatic cancer detection and monitoring progression. However, detection of CTCs remains challenging due to their low frequency and heterogeneity. Herein, we report a bioinspired approach to detect individual cancer cells, based on a signal amplification cascade using a programmable DNA hybridization chain reaction (HCR) circuit. We applied this approach to detect HER2⁺ cancer cells using the anti‐HER2 antibody (trastuzumab) coupled to initiator DNA eliciting a HCR cascade that leads to a fluorescent signal at the cell surface. At 4 °C, this HCR detection scheme resulted in highly efficient, specific and sensitive signal amplification of the DNA hairpins specifically on the membrane of the HER2⁺ cells in a background of HER2⁻ cells and peripheral blood leukocytes, which remained almost non‐fluorescent. The results indicate that this system offers a new strategy that may be further developed toward an in vitro diagnostic platform for the sensitive and efficient detection of CTC.

Applications of Mass Spectrometry for Clinical Diagnostics: The Influence of Turnaround Time

This critical review discusses how the need for reduced clinical turnaround times has influenced chemical instrumentation. We focus on the development of modern mass spectrometry (MS) and its application in clinical diagnosis. With increased functionality that takes advantage of novel front-end modifications and computational capabilities, MS can now be used for non-traditional clinical analyses, including applications in clinical microbiology for bacteria differentiation and in surgical operation rooms. We summarize here recent developments in the field that have enabled such capabilities, which include miniaturization for point-of-care testing, direct complex mixture analysis via ambient ionization, chemical imaging and profiling, and systems integration.

Dual-mode detection of avian influenza virions (H9N2) by ICP-MS and fluorescence after quantum dot labeling with immuno-rolling circle amplification

Avian influenza virus (AIVs), hosted in poultry, are the pathogens of many poultry diseases and human infections, which bring huge losses to the poultry breeding industry and huge panic to society. Therefore, it is of great significance to establish accurate and sensitive detection methods for AIVs. In this work, a dual-mode detection method based on immuno-rolling circle amplification (immuno-RCA) and quantum dots (QDs) labeling for inductively coupled plasma mass spectrometry (ICP-MS) and fluorescence detection of H9N2 AIV was developed. The dual-mode detection of the QDs by ICP-MS and fluorescence is used to achieve mutual verification within the analysis results, thus improving the accuracy of the method. With the immuno-RCA, the sensitivity of the method was increased by two orders of magnitude. The limit of detection of the proposed method is 17 ng L^-1 and 61 ng L^-1, and the linear range of the proposed method is 0.05-5 ng mL^-1 and 0.1-5 ng mL^-1 with ICP-MS and fluorescence detection, respectively. The relative standard deviation (n = 7) is 4.9% with ICP-MS detection and 3.1% with fluorescence detection. Furthermore, the proposed method was applied to the analysis of chicken serum samples, no significant different was found for two modes detection and the recoveries of the spiking experiments are acceptable, indicating that the method has good practical potential for real sample analysis.

Electrochemical Detection of Circulating Tumor Cells Based on DNA Generated Electrochemical Current and Rolling Circle Amplification

Circulating tumor cells (CTCs) are important indicators for tumor diagnosis and tumor metastasis. However, the extremely low levels of CTCs in peripheral blood challenges the precise detection of CTCs. Herein, we report DNA generated electrochemical current combined with rolling circle amplification (RCA) as well as magnetic nanospheres for highly efficient magnetic capture and ultrasensitive detection of CTCs. The antiepithelial cell adhesion molecule (EpCAM) antibody-modified magnetic nanospheres were used to capture and enrich CTCs. The following binding of an aptamer onto the CTC surface and the subsequent RCA assembled a significant amount of DNA molecules onto the electrode. The reaction of the DNA molecules with molybdate can then form redox molybdophosphate and produce an electrochemical current. Using the breast cancer cell MCF-7 as a model, the sensor displays good performances toward detection of MCF-7 that was spiked into peripheral blood. The signal amplification strategy integrated with a magnetic nanosphere platform exhibits good performance in the efficient capture and detection of CTCs, which may find wide potential in cancer diagnostics and therapeutics.

Cellular interface supported toehold strand displacement cascade for amplified dual-electrochemical signal and its application for tumor cell analysis

In this work, toehold strand displacement cascade (TSDC) has been delicately designed and carried out on the cellular interface for the amplification and output of dual-electrochemical signal. Specifically, antibody cross-linked T strand can recognize cell which is linked with immune-magnetic bead. Subsequently, T strand on the cellular interface can mediate the occurrence of TSDC, resulting the change of SN₃/S1-MB to SN₃/S2-Fc ratio in the supernatant after magnetic separation. The resultant SN₃/S1-MB and SN₃/S2-Fc can be immobilized on the electrode interface through click chemistry and give the amplified double electrochemical signal. So the tumor cell amount can closely correlate with the change of the double signal. Except for output of the double signal for improvement of analytical accuracy, the double magnetic separation not only eliminate the interference of the complicated substances in serum, but also remove the influence of cell on click reaction on the electrode interface. So based on cellular interface supported TSDC for amplified dual-electrochemical signal, the established method has been successfully applied to analyze the tumor cells in serum accurately and sensitively.

Direct Plasmon-Enhanced Electrochemistry for Enabling Ultrasensitive and Label-Free Detection of Circulating Tumor Cells in Blood

In this work, we developed a simple electrochemical method for ultrasensitive and label-free detection of circulating tumor cells (CTCs) based on direct plasmon-enhanced electrochemistry (DPEE). After plasmonic gold nanostars (AuNSs) were modified on the glassy carbon (GC) electrode, the aptamer probe was immobilized on the AuNSs surface, which can selectively capture the CTCs in samples. Upon localized surface plasmon resonance (LSPR) excitation, the electrochemical current response can be enhanced remarkably due to efficient hot electrons transport from AuNSs to the external circuit. The captured cells on the AuNSs surface will influence the hot electrons transport efficiency, leading to a decreased current response. Using ascorbic acid (AA) as the electroactive probe, it was found that the current responses of the AuNSs/GC electrode upon light irradiation decrease with the cell concentration. Due to the special molecular recognition of the aptamer and enhanced electrochemical performance of the plasmon, the proposed method enables an ultrasensitive and label-free detection of CTCs with excellent selectivity. The experimental results show that CCRF-CEM cell concentrations as low as 5 cells/mL can be successfully detected, which is superior to most reported work up to now. Using the present method, MCF-7 cells as low as 10 cells/mL can be also successfully detected, indicating the universality of the proposed method for CTCs detection. Furthermore, the cytosensor can successfully distinguish CTCs from normal cells in blood samples. The as-proposed strategy provides a promising application of DPEE in the development of novel biosensors for nondestructive analysis of biological samples.

Electrochemiluminescence cytosensing platform based on Ru(bpy)32+@silica-Au nanocomposite as luminophore and AuPd nanoparticles as coreaction accelerator for in situ evaluation of intracellular H2O2

An electrochemiluminescence (ECL) cytosensor was fabricated onto a microfluidic paper-based analytical device (μ-PAD) in order to detect hydrogen peroxide (H₂O₂) which was released from tumor cells. The ECL probe Ru(bpy)₃²⁺@silica-Au nanocomposite (Ru@SiO₂-Au) was fabricated and served as ECL reagent. The ECL of Ru@SiO₂-Au nanocomposite was quenched by the ferrocene (Fc). AuPd nanoparticles (AuPd NPs), which were modified on the paper working electrode (PWE), were served as the catalyst of H₂O₂ to produce hydroxyl radicals (•OH) for cleaving Fc-labelled DNA to achieve "signal-on", and AuPd NPs also severed as coreaction accelerator. H₂O₂ was released from cells under the stimulation of phorbol myristate acetate. Fc-labelled DNA strand was cleaved via •OH. Fc molecule departed from the PWE surface, The ECL could be recovered. An ECL cytosensor on a 3D origami device was constructed. The ECL response of the Ru@SiO₂-Au-Fc system was related to the number of cells. The ECL intensity was quantitatively related with the logarithm of MCF-7 cells number and H₂O₂ concentration, the detection limit was 30 cells mL^-1. As a consequence, this work provided a really low-cost and disposable μ-PAD for sensitive detection of intracellular H₂O₂. What's more, this work had potential application value for studying cellular biology and pathophysiology.

Paper-based fluorometric immunodevice with quantum-dot labeled antibodies for simultaneous detection of carcinoembryonic antigen and prostate specific antigen

A method is described for simultaneous fluorometric determination of the biomarkers carcinoembryonic antigen (CEA) and prostate specific antigen (PSA) on the same zone of a paper-based immunodevice. Two kinds of CdTe quantum dots, with respective emission peaks at 525 nm and 605 nm under a single excitation wavelength of 272 nm, were used to label the antibodies against CEA and PSA. Then the capture antibodies of CEA and PSA were immobilized on the same zone of the paper-based device. With the difference of the colors of the quantum dot fluorescence (green and orange), CEA and PSA can be detected on the same zone of the paper-based device. By using of sandwich immunoassay format, CEA and PSA can be simultaneously detected in human serum samples with a linear response in the 1.0-40 ng·mL^-1 concentration range for both. The recovery rates of the serum sample were in the range of 95-105%. The method has the potential of being applied to the simultaneous determination of various other kinds of substances on a single multichannel paper-based chip. Graphical abstract Schematic presentation of the simultaneous fluorometric detection of two cancer biomarkers on the same zone of the paper-based immunodevice is provided. Two kinds of CdTe quantum dots with different emission peaks under the same excitation wavelength are labeled on different detection antibodies.

Advances in isolation and detection of circulating tumor cells based on microfluidics

Circulating tumor cells (CTCs) are the cancer cells that circulate in the peripheral blood after escaping from the original or metastatic tumors. CTCs could be used as non-invasive source of clinical information in early diagnosis of cancer and evaluation of cancer development. In recent years, CTC research has become a hotspot field wherein many novel CTC detection technologies based on microfluidics have been developed. Great advances have been made that exhibit obvious technical advantages, but cannot yet satisfy the current clinical requirements. In this study, we review the main advances in isolation and detection methods of CTC based on microfluidics research over several years, propose five technical indicators for evaluating these methods, and explore the application prospects. We also discuss the concepts, issues, approaches, advantages, limitations, and challenges with an aim of stimulating a broader interest in developing microfluidics-based CTC detection technology.

Near-Infrared Fluorescent Ag2S Nanodot-Based Signal Amplification for Efficient Detection of Circulating Tumor Cells

The level of circulating tumor cells (CTCs) plays a critical role in tumor metastasis and personalized therapy, but it is challenging for highly efficient capture and detection of CTCs because of the extremely low concentration in peripheral blood. Herein, we report near-infrared fluorescent Ag₂S nanodot-based signal amplification combing with immune-magnetic spheres (IMNs) for highly efficient magnetic capture and ultrasensitive fluorescence labeling of CTCs. The near-infrared fluorescent Ag₂S nanoprobe has been successfully constructed through hybridization chain reactions using aptamer-modified Ag₂S nanodots, which can extremely improve the imaging sensitivity and reduce background signal of blood samples. Moreover, the antiepithelial-cell-adhesion-molecule (EpCAM) antibody-labeled magnetic nanospheres have been used for highly capture rare tumor cells in whole blood. The near-infrared nanoprobe with signal amplification and IMNs platform exhibits excellent performance in efficient capture and detection of CTCs, which shows great potential in cancer diagnostics and therapeutics.