Immunodetection and counting of circulating tumor cells (HepG2) by combining gold nanoparticle labeling, rolling circle amplification and ICP-MS detection of gold

Label-free detection of biomolecules using inductively coupled plasma mass spectrometry (ICP-MS)

Bioassays using inductively coupled plasma mass spectrometry (ICP-MS) have gained increasing attention because of the high sensitivity of ICP-MS and the various strategies of labeling biomolecules with detectable metal tags. The classic strategy to tag the target biomolecules is through direct antibody-antigen interaction and DNA hybridization, and requires the separation of the bound from the unbound tags. Label-free ICP-MS techniques for biomolecular assays do not require direct labeling: they generate detectable metal ions indirectly from specific biomolecular reactions, such as enzymatic cleavage. Here, we highlight the development of three main strategies of label-free ICP-MS assays for biomolecules: (1) enzymatic cleavage of metal-labeled substrates, (2) release of immobilized metal ions from the DNA backbone, and (3) nucleic acid amplification-assisted aggregation and release of metal tags to achieve amplified detection. We briefly describe the fundamental basis of these label-free ICP-MS assays and discuss the benefits and drawbacks of various designs. Future research is needed to reduce non-specific adsorption and minimize background and interference. Analytical innovations are also required to confront challenges faced by in vivo applications.

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.

Study on the detection of anthrax by ICP-MS based on gold nanoparticle labeling

BACKGROUND

In recent years, inductively coupled plasma mass spectrometry (ICP-MS) has been widely used in the field of molecular biology because of its unique advantages. Anthrax is a widespread and long-standing infectious disease, which affects and restricts people's work and life seriously.

OBJECTIVE

The study goal is to develop a new method for the detection of anthrax.

METHODS

A rapid, sensitive and accurate method for the detection of anthrax characteristic DNA was proposed by combing gold nanoparticles (AuNPs) and inductively coupled plasma mass spectrometry.

RESULTS

The linear range of this method is 100-2500 pmol/L and the limit of detection of 16.61 pmol/L.

CONCLUSION

The proposed method has numerous advantages, including simplicity of operation, high sensitivity, and specificity, which provides a new idea for the detection of anthrax. Importantly, this methodology has good potential for the detection of other biological substances such as bacteria and viruses by changing the modification sequence on the nanoparticle probe.

Multifunctional Au nano-bridged nanogap probes as ICP-MS/SERS dual-signal tags and signal amplifiers for bacteria discriminating, quantitative detecting and photothermal bactericidal activity

Ultra-sensitive detection of pathogenic bacteria is of great significance in the early stage of bacterial infections and treatment. In this work, we report a novel strategy using multifunctional Au nano-bridged nanogap nanoparticles (Au NNPs)-based sandwich nanocomposites, that made of Concanavalin A-conjugated Fe₃O₄@SiO₂ NPs (ConA-Fe₃O₄@SiO₂ NPs)/bacteria/aptamer-modified Au NNPs (apt-Au NNPs), for bacteria discrimination and quantitative detection by surface-enhanced Raman scattering (SERS) and inductively coupled plasma mass spectrometry (ICP-MS), and subsequently photothermal antibacterial assay. The sandwich nanocomposite consists of ConA-Fe₃O₄@SiO₂ NPs to magnetically enrich and photothermal killing bacteria, and dual-signal tags of apt-Au NNPs for both SERS sensing and ICP-MS quantification. This strategy can specifically distinguish different kinds of pathogenic bacteria, and provided a good linear relationship of Staphylococcus aureus (S. aureus) in the range from 50 to 10⁴ CFU/mL with a detection limit of 11 CFU/mL, as well as realized ultralow amounts of bacterial detection in serum sample with high accuracy. Based on the quantitative detection, high antibacterial efficiency was monitored by ICP-MS. Overall, the established method combines bacteria discrimination, quantitative detection, and photothermal elimination with a simple and rapid process, which provides a novel way for the early diagnosis and treatment of bacterial infection.

Noninvasive Optical Isolation and Identification of Circulating Tumor Cells Engineered by Fluorescent Microspheres

Circulating tumor cells (CTCs) are rare, meaning that current isolation strategies can hardly satisfy efficiency and cell biocompatibility requirements, which hinders clinical applications. In addition, the selected cells require immunofluorescence identification, which is a time-consuming and expensive process. Here, we developed a method to simultaneously separate and identify CTCs by the integration of optical force and fluorescent microspheres. Our method achieved high-purity separation of CTCs without damage through light manipulation and avoided additional immunofluorescence staining procedures, thus achieving rapid identification of sorted cells. White blood cells (WBCs) and CTCs are similar in size and density, which creates difficulties in distinguishing them optically. Therefore, fluorescent PS microspheres with high refractive index (RI) are designed here to capture the CTCs (PS-CTCs) and increase the average index of refraction of PS-CTCs. In optofluidic chips, PS-CTCs were propelled to the collection channel from the sample mixture, under the radiation of light force. Cells from the collection outlet were easily identified under a fluorescence microscope due to the fluorescence signals of PS microspheres. This method provides an approach for the sorting and identification of CTCs, which holds great potential for clinical applications in early diagnosis of disease.

Nanotechnology in emerging liquid biopsy applications

Liquid biopsy is considered as the most attractive alternative to traditional tissue biopsies. The major advantages of this approach lie in the non-invasive procedure, the rapidness of sample collection and the potential for early cancer diagnosis and real-time monitoring of the disease and the treatment response. Nanotechnology has dynamically emerged in a wide range of applications in the field of liquid biopsy. The benefits of using nanomaterials for biosensing include high sensitivity and detectability, simplicity in many cases, rapid analysis, the low cost of the analysis and the potential for portability and personalized medicine. The present paper reports on the nanomaterial-based methods and biosensors that have been developed for liquid biopsy applications. Most of the nanomaterials used exhibit great analytical performance; moreover, extremely low limits of detection have been achieved for all studied targets. This review will provide scientists with a comprehensive overview of all the nanomaterials and techniques that have been developed for liquid biopsy applications. A comparison of the developed methods in terms of detectability, dynamic range, time-length of the analysis and multiplicity, is also provided.

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.

Recent advances in rolling circle amplification-based biosensing strategies-A review

Rolling circle amplification (RCA) is an efficient enzymatic isothermal reaction that using circular probe as a template to generate long tandem single-stranded DNA or RNA products under the initiation of short DNA or RNA primers. As a simplified derivative of natural rolling circle replication which synthesizes copies of circular nucleic acids molecules such as plasmids, RCA amplifies the circular template rapidly without thermal cycling and finds various applications in molecular biology. Compared with other amplification strategies, RCA has many obvious advantages. Firstly, because of the strict complementarity required in ligation of a padlock probe, it endows the RCA reaction with high specificity and can even be utilized to distinguish single base mismatches. Secondly, through the introduction of multiple primers, exponential amplification can be achieved easily and leads to a good sensitivity. Thirdly, RCA products can be customized by manipulating circular templates to generate functional nucleic acids such as aptamer, DNAzymes and restriction enzyme sites. Moreover, the RCA has good biocompatibility and is especially suitable for in situ detection. Therefore, RCA has attracted considerable attention as an efficient and potential tool for highly sensitive detection of biomarkers. Herein, we comprehensively introduce the fundamental principles of RCA technology, summarize it from three aspects including initiation mode, amplification mode and signal output mode, and discuss the recent application of RCA-based biosensor in this review.

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.

Electrochemical assay for analysis of circulation tumor cells based on isolation of the cell with magnetic nanoparticles and reaction of DNA with molybdate

A universal strategy was developed for the analysis of circulating tumor cells (CTCs) based on reaction of DNA in the cells with molybdate. Initially, CTCs were enriched and isolated from samples by magnetic nanoparticles. Then, after killing the isolated cells by heat treatment, the cell membrane was raptured, and the DNA molecules contained in the cells were released. The following reaction of the released DNA molecules with molybdate can form redox molybdophosphate, resulting in electrochemical current. This electrochemical assay can be applied to the detection of different CTCs as long as the CTCs can be isolated from the samples, with a universal signal detection method, without additional signal amplification strategies. Breast cancer cell MCF-7 was chosen as a model CTC for this study. At a working potential of 0.2 V vs. Ag/AgCl electrode, the electrochemical current is linearly related to the MCF-7 cell concentration from 5 to 1000 cells mL^-1 with a limit of detection of 2 cells mL^-1. The assay was successfully applied for detection of MCF-7 in human blood samples. This electrochemical assay can be applied for detection of different CTCs and also for simultaneous detection of CTCs. Graphical abstract A universal strategy was developed for the analysis of circulating tumor cells (CTCs) based on reaction of DNA contained in the cells with molybdate.

Colorimetric nanoplatform for visual determination of cancer cells via target-catalyzed hairpin assembly actuated aggregation of gold nanoparticles

According to aptamer-mediated hairpin DNA cascade amplifier and gold nanoparticles aggregation, an optical platform for cancer cells determination has been proposed. High-affinity chimeric aptamers were used for cancer cell detection and also as an initiator for beginning hairpin assembly to construct three-way junction (3WJ) nanostructures. These three hairpins were modified at 3' ends with biotin. In the presence of target cell, chimeric aptamer binds to its ligand on cell surface and initiates 3WJ nanostructures formation. These 3WJ nanostructures interact with streptavidin-modified gold nanoparticles (AuNPs) via non-covalent biotin-streptavidin interactions and create a crossover lattice of nanoparticles. This event leads to AuNPs aggregation and red-shifting. The results were confirmed by gel electrophoresis and UV-visible spectrophotometry. The dynamic range of this assay is 25 to 10⁷ cells with a detection limit of 10 cells which is respectively 9 and 4 times more significant than the sensitivity of AuNP-based approaches without amplification and enzyme-mediated signal amplification. Graphical abstract.

Aptamer-based photoelectrochemical assay for the determination of MCF-7

In this work, an aptamer-based photoelectrochemical (PEC) assay is reported for the determination of MCF-7 breast cancer cells using hexagonal carbon nitride tubes (HCNTs) as photoactive material. The aptamer immobilized on the HCNT surface can specifically bind with mucin 1 protein (MUC1) that is overexpressed on the surface of MCF-7 cell. Thus, the PEC assay has high specificity for the determination of MCF-7. The determination of MCF-7 is due to the binding of MCF-7 onto HCNT that suppressed the photocurrent intensity. The PEC assay displays good performances for MCF-7 determination with a linear range from 1 × 10² to 1 × 10⁵ cell mL^-1 and limit of detection down to 17 cells mL^-1. Meanwhile, the PEC assay can distinguish MCF-7 from normal cells in blood samples, which may have potential applications in cancer diagnostics and therapeutics.

PdIrBP mesoporous nanospheres combined with superconductive carbon black for the electrochemical determination and collection of circulating tumor cells

An integrated electrochemical immunoassay is described for the determination of circulating tumor cells (CTCs). For the first time, Ketjen black (KB), which is a superconductive carbon material, was incorporated with Au nanoparticles (AuNPs) and used to modify the surface of gold electrodes. A cocktail of anti-epithelial cell adhesion molecules (EpCAM) and anti-vimentin antibodies was chosen to capture the CTCs. Palladium-iridium-boron-phosphorus alloy-modified mesoporous nanospheres (PdIrBPMNS) served as a catalytic tag to amplify the current signal. Glycine-HCl (Gly-HCl) was used as an antibody eluent to release and collect the captured CTCs from the electrodes for further clinical research without compromising cell viability. The response of the method increased linearly from 10 to 1 × 10⁶ cells mL^-1 CTCs, while the detection limit was calculated to be as low as 2 cells mL^-1. This method was successfully used to determine CTCs in spiked blood samples and demonstrated good recovery. Graphical abstractKetjen black/AuNPs was incorporated in the electrochemical platform to enhance the electron transfer ability of the electrode surface. PdIrBP mesoporous nanospheres were used to amplify DPV signal in this assay. The introduction of Gly-HCl realized nondestructive recovery of circulating tumor cells.

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.