Combination of Magnetic-Beads-Based Multiple Metal Nanoparticles Labeling with Hybridization Chain Reaction Amplification for Simultaneous Detection of Multiple Cancer Cells with Inductively Coupled Plasma Mass Spectrometry

Isolation of aptamers with excellent cross-reactivity and specificity to sulfonamides towards a ratiometric fluorescent aptasensor for the detection of nine sulfonamides in seafood

Sulfonamides (SAs) is a class of antibiotics that extensively used for treating infectious diseases in livestock industries and aquaculture. Thus, it is urgent need to obtain the bio-receptor, which has excellent cross-reactivity and specificity to SAs, for developing high-throughput methods for the determination of multiple SAs even all commonly-used SAs, to realize the quick screening/detection of total SAs in animal-derived foods. We herein isolated several SAs-specific cross-reactive aptamers by using a library-immobilized SELEX with multi-SAs parallel selection strategy. Two of the isolated aptamers (Sul-01 and Sul-04) can specifically recognize and bind seven SAs respectively with higher binding affinity and no interference of non-sulfonamide antibiotics, and thus can be applied as bio-receptors for developing high-throughput aptasensors for the quick screening/detection of multiple SAs. By using the mixture of Sul-01 and Sul-04 as bio-receptor, a ratiometric fluorescent aptasensor was created for the quick detection of nine SAs including sulfamethoxydiazine (SMD), sulfapyridine (SPD), sulfaquinoxaline (SQ), sulfathiazole (ST), sulfamonomethoxine (SMM), sulfamerazine (SMR), sulfaguanidine (SG), sulfamethazine (SMZ) and sulfadiazine (SD) with a detection limit (LOD) of 0.10-0.50 μM, or total of above nine SAs with a LOD of 0.20 μM. The fluorescent aptasensor was successfully applied to detect each or total of SMD, SPD, SQ, ST, SMM, SMR, SG, SMZ and SD in fish samples with a recovery of 83 %-92 % and a relative standard deviation (RSD, n = 5) < 5 %. This study not only provided several promising bio-receptors for the development of diverse high-throughput aptasensors to achieve the quick screening of multiple SAs residues, but also provided a simple, stable and sensitive method for the quick screening of SMD, SPD, SQ, ST, SMM, SMR, SG, SMZ and SD in seafood.

Pathogen detection via inductively coupled plasma mass spectrometry analysis with nanoparticles

Infections caused by viruses and bacteria pose a significant threat to global public health, emphasizing the critical importance of timely and precise detection methods. Inductively coupled plasma mass spectrometry (ICP-MS), a contemporary approach for pathogen detection, offers distinct advantages such as high sensitivity, a wide linear range, and multi-index capabilities. This review elucidates the underexplored application of ICP-MS in conjunction with functional nanoparticles (NPs) for the identification of viruses and bacteria. The review commences with an elucidation of the underlying principles, procedures, target pathogens, and NP requirements for this innovative approach. Subsequently, a thorough analysis of the advantages and limitations associated with these techniques is provided. Furthermore, the review delves into a comprehensive examination of the challenges encountered when utilizing NPs and ICP-MS for pathogen detection, culminating in a forward-looking assessment of the potential pathways for advancement in this domain. Thus, this review contributes novel perspectives to the field of pathogen detection in biomedicine by showcasing the promising synergy of ICP-MS and NPs.

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.

Mass Spectrometry Analysis for Clinical Applications: A Review

Mass spectrometry (MS) has become an attractive analytical method in clinical analysis due to its comprehensive advantages of high sensitivity, high specificity and high throughput. Separation techniques coupled MS detection (e.g., LC-MS/MS) have shown unique advantages over immunoassay and have developed as golden criterion for many clinical applications. This review summarizes the characteristics and applications of MS, and emphasizes the high efficiency of MS in clinical research. In addition, this review also put forward further prospects for the future of mass spectrometry technology, including the introduction of miniature MS instruments, point-of-care detection and high-throughput analysis, to achieve better development of MS technology in various fields of clinical application. Moreover, as ambient ionization mass spectrometry (AIMS) requires little or no sample pretreatment and improves the flux of MS, this review also summarizes its potential applications in clinic.

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.

Metal Nanoparticles as Novel Agents for Lung Cancer Diagnosis and Therapy

Lung cancer is one of the most common malignancies worldwide and contributes to most cancer-related morbidity and mortality cases. During the past decades, the rapid development of nanotechnology has provided opportunities and challenges for lung cancer diagnosis and therapeutics. As one of the most extensively studied nanostructures, metal nanoparticles obtain higher satisfaction in biomedical applications associated with lung cancer. Metal nanoparticles have enhanced almost all major imaging strategies and proved great potential as sensor for detecting cancer-specific biomarkers. Moreover, metal nanoparticles could also improve therapeutic efficiency via better drug delivery, improved radiotherapy, enhanced gene silencing, and facilitated photo-driven treatment. Herein, the recently advanced metal nanoparticles applied in lung cancer therapy and diagnosis are summarized. Future perspective on the direction of metal-based nanomedicine is also discussed. Stimulating more research interests to promote the development of metal nanoparticles in lung cancer is devoted.

A renewable platform based on the entropy-driven catalytic amplification and element labeling inductively coupled plasma mass spectrometry for microRNA analysis

The element labeling inductively coupled plasma mass spectrometry (ICP-MS) strategy has been increasingly applied to the bioanalysis for various bio-targets. Herein, a renewable analysis platform with element labeling ICP-MS was firstly proposed for microRNA (miRNA) analysis. The analysis platform was established on the magnetic bead (MB) with entropy-driven catalytic (EDC) amplification. When the EDC reaction was initiated by target miRNA, numerous strands labeled with Ho element were released from MBs, and ¹⁶⁵Ho in the supernatant detected by ICP-MS could reflect the amount of target miRNA. After detection, the platform was easily regenerated by adding strands to reassemble EDC complex on MBs. This MB platform could be used four times, and the limit of detection for miRNA-155 was 8.4 pmol L^-1. Moreover, the developed regeneration strategy based on EDC reaction can be easily expanded to other renewable analysis platforms, such as, the renewable platform involving EDC and rolling circle amplification technology. Overall, this work proposed a novel regenerated bioanalysis strategy to reduce the consumption of reagent and time for probe preparation, profiting the development of bioassay based on element labeling ICP-MS strategy.

Mass tag-encoded nanointerfaces for multiplexed mass spectrometric analysis and imaging of biomolecules

Revealing multiple biomolecules in the physiopathological environment simultaneously is crucial in biological and biomedical research. Mass spectrometry (MS) features unique technical advantages in multiplexed and label-free analyses. However, owing to comparably low abundance and poor ionization efficiency of target biomolecules, direct MS profiling of these biological species in vitro or in situ remains a challenge. An emerging route to solve this issue is to devise mass tag (MT)-encoded nanointerfaces which specifically convert the abundance or activity of biomolecules into amplified ion signals of mass tags, offering an ideal strategy for synchronous MS assaying and mapping of multiple targets in biofluids, cells and tissues. This review provides a thorough and organized overview of recent advances in MT-encoded nanointerfaces elaborately tailored for several practical applications in multiplexed MS bioanalysis and biomedical research. First, we start with elucidation of the structural characteristics and working principle of MT-encoded nanointerfaces in specific labeling and sensing of multiple biological targets. In addition, we further discuss the application scenarios of MT-encoded nanointerfaces particularly in multiplexed biomarker assays, cell analysis, and tissue imaging. Finally, the current challenges are pointed out and future prospects of these nanointerfaces in MS analysis are forecast.

Broad-Specificity Aptamer of Sulfonamides: Isolation and Its Application in Simultaneous Detection of Multiple Sulfonamides in Fish Sample

Sulfonamide antibiotics (SAs) are widely used in animal husbandry and aquaculture, and the excess residues of SAs in animal-derived foods will harm the health of consumers. In reality, various SAs were alternately used in animal husbandry and aquaculture, and thus, it is urgent need to develop simple and high-throughput methods for simultaneously detecting multiple SAs or groups of SAs in order to realize rapid screening of total SAs residues in animal-derived foods. We herein isolated a broad-specificity aptamer for SAs by using a multi-SAs systematic evolution of ligands by exponential enrichment (SELEX) strategy. The isolated broad-specificity aptamer has a higher binding affinity to five different SAs including sulfaquinoxaline (SQ), sulfamethoxypyridazine (SMPZ), sulfametoxydiazine (SMD), sulfachloropyridazine (SCP), and sulfapyridine (SPD) and, thus, can be used as a bioreceptor for developing various high-throughput methods for the simultaneous detection or rapid screening of above five SAs. Based on the isolated broad-specificity aptamer and Cy7 (diethylthiatricarbocyanine) displacement strategy, a colorimetric aptasensor was developed for the simultaneous detection of SQ, SMPZ, SMD, SCP, and SPD with a visual detection limit of 2.0-5.0 μM and a spectrometry detection limit of 0.2-0.5 μM. The colorimetric aptasensor was successfully used to detect SQ, SMPZ, SMD, SCP, and SPD in fish muscle with a recovery of 82%-92% and a RSD (n = 5) < 7%. The success of this study provided a promising bioreceptor for developing various high-throughput methods for on-site rapid screening of multiple SAs residues, as well as a simple method for the rapid and cost-effective screening of total SQ, SMPZ, SMD, SCP, and SPD in seafood.

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.

Target-modulated competitive binding and exonuclease I-powered strategy for the simultaneous and rapid detection of biological targets

Simultaneous multiple-target detection is essential for the prevention, identification, and treatment of numerous diseases. In this study, a novel strategy based on target-modulated competitive binding and exonuclease I (Exo I)-powered signal molecule release was established with the advantages of rapid response and high selectivity and sensitivity. The strategy holds substantial potential for the development of versatile platforms for the simultaneous detection of biological targets. To mitigate the low load capacity and time-consuming responsive process of the Zr-MOF system, UiO-67 was chosen to replace UiO-66 (a typical Zr-MOF) as the nanocarrier for encapsulating more signal molecules, whereby the assembled double-stranded DNA (dsDNA) structures of UiO-67 acted as gatekeepers to form dsDNA-functionalized MOFs. Additionally, Exo I was introduced into the system to accelerate the release of the signal molecules. In the presence of biological targets, the competitive binding between the targets and aptamers caused the hydrolysis of the free DNA sequence by Exo I, promoting the release of signal molecules and leading to a rapid and significant increase in the fluorescence intensity. For adenosine triphosphate (ATP) and cytochrome c (cyt c), which were chosen as model biological targets, this sensor displayed detection limits as low as 5.03 and 6.11 fM, respectively. Moreover, the developed biosensor was successfully applied to the simultaneous detection of ATP and cyt c in spiked serum samples. Therefore, this strategy provides guidance for further research of biosensors for simultaneous multiple-target detection and propels the application of MOF carriers in biomedicine.

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.

Mass Spectrometric Biosensing: A Powerful Approach for Multiplexed Analysis of Clinical Biomolecules

Rapid and sensitive detection of clinical biomolecules in a multiplexed fashion is of great importance for accurate diagnosis of diseases. Mass spectrometric (MS) approaches are exceptionally suitable for clinical analysis due to its high throughput, high sensitivity, and reliable qualitative and quantitative capabilities. To break through the bottleneck of MS technique for detecting high-molecular-weight substances with low ionization efficiency, the concept of mass spectrometric biosensing has been put forward by adopting mass spectrometric chips to recognize the targets and mass spectrometry to detect the signals switched by the recognition. In this review, the principle of mass spectrometric sensing, the construction of different mass tags used for biosensing, and the typical combination mode of mass spectrometric imaging (MSI) technique are summarized. Future perspectives including the design of portable matching platforms, exploitation of novel mass tags, development of effective signal amplification strategies, and standardization of MSI methodologies are proposed to promote the advancements and practical applications of mass spectrometric biosensing.

Recent Progress in DNA Hybridization Chain Reaction Strategies for Amplified Biosensing

With the continuous development of DNA nanotechnology, various spatial DNA structures and assembly techniques emerge. Hybridization chain reaction (HCR) is a typical example with exciting features and bright prospects in biosensing, which has been intensively investigated in the past decade. In this Spotlight on Applications, we summarize the assembly principles of conventional HCR and some novel forms of linear/nonlinear HCR. With advantages like great assembly kinetics, facile operation, and an enzyme-free and isothermal reaction, these strategies can be integrated with most mainstream reporters (e.g., fluorescence, electrochemistry, and colorimetry) for the ultrasensitive detection of abundant targets. Particularly, we select several representative studies to better illustrate the novel ideas and performances of HCR strategies. Theoretical and practical utilities are confirmed for a range of biosensing applications. In the end, a deep discussion is provided about the challenges and future tasks of this field.

Engineering of nanomaterials for mass spectrometry analysis of biomolecules

Mass spectrometry (MS) based analysis has received intense attention in diverse biological fields. However, direct MS interrogation of target biomolecules in complex biological samples is still challenging, due to the extremely low abundance and poor ionization potency of target biological species. Innovations in nanomaterials create new auxiliary tools for deep and comprehensive MS characterization of biomolecules. More recently, growing research interest has been directed to the compositional and structural engineering of nanomaterials for enriching target biomolecules prior to MS analysis, enhancing the ionization efficiency in MS detection and designing biosensing nanoprobes in sensitive MS readout. In this review, we mainly focus on the recent advances in the engineering of nanomaterials towards their applications in sample pre-treatment, desorption/ionization matrices and ion signal amplification for MS profiling of biomolecules. This review will provide a toolbox of nanomaterials for researchers devoted to developing analytical methods and practical applications in the biological MS field.

Homogeneous Visual and Fluorescence Detection of Circulating Tumor Cells in Clinical Samples via Selective Recognition Reaction and Enzyme-Free Amplification

Here we report a simple all-nucleic-acid enzyme-free catalyzed hairpin assembly assisted amplification strategy with quantum dots (QDs) as the nanoscale signal reporter for homogeneous visual and fluorescent detection of A549 lung cancer cells from clinical blood samples. This work was based on the phenomenon that CdTe QDs can selectively recognize Ag⁺ and C-Ag⁺-C and by using mucin 1 as the circulating tumor cells (CTCs) marker and aptamer as the recognition probe. Under optimized conditions, the limits of detections as low as 0.15 fg/mL of mucin 1 and 3 cells/mL of A549 cells were achieved with fluorescence signals. A 1 fg/mL concentration of mucin 1 and 100 cells/mL of A549 can be distinguished by the naked eye. This method was used to quantitatively analyze CTCs in 51 clinical whole blood samples of patients with lung cancer. The levels of CTCs detected in clinical samples by this method were consistent with those obtained using the folate receptor-polymerase chain reaction clinical test kit and correlated with radiologic and pathological findings.

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.

Dually enhanced homogenous synthesis of molybdophosphate by hybridization chain reaction and enzyme nanotags for the electrochemical bioassay of carcinoembryonic antigen

A magnetic bead (MB)-based sandwich biorecognition reactions is combined with a gold nanoprobe-induced homogenous synthesis of molybdophosphate to develop a novel bioassay method for the electrochemical detection of the tumor biomarker of carcinoembryonic antigen (CEA). The nanoprobe is prepared through the specific loading of numerous alkaline phosphatase (ALP)-functionalized gold nanoparticles (Au NPs) on a double-stranded DNA (dsDNA) produced by the CEA aptamer-triggered hybridization chain reaction (HCR). Both the large amounts of PO₄^3- produced by the ALP catalytic hydrolysis of pyrophosphate and the phosphate backbones of dsDNA can react with the added MoO₄^2- to generate electroactive molybdophosphates. So, the gold nanoprobe was used for signal tracing of the sandwich bioassay of CEA at a constructed antibody-functionalized MB platform. The sensitive electrochemical measurement of molybdophosphate produced from the quantitatively captured nanoprobes at a carbon nanotube-modified electrode (measured at about 0.12 V vs. Ag/AgCl, 3 M KCl) enabled the convenient signal transduction of the method. Due to the dually enhanced synthesis of molybdophosphate by the HCR and multi-enzyme Au NP nanotags, this method shows a wide linear range from 0.05 pg mL^-1 to 10 ng mL^-1 along with a low detection limit of 0.027 pg mL^-1. In addition, the MB-based biorecognition reaction and the homogeneous synthesis of molybdophosphate are much convenient in manipulations. These excellent performances decide the extensive application potentials of the method. Graphical abstract A magnetic bead-based bioassay method was simply developed for the electrochemical detection of carcinoembryonic antigen. The dually enhanced homogenous synthesis of molybdophosphate by hybridization chain reaction (HCR) and enzyme nanotags and the sensitive electrochemical measurement of molybdophosphate at a carbon nanotube (CNT)-electrode enable ultrasensitive signal transduction of the method.

A carbon-based polymer dot sensor for breast cancer detection using peripheral blood immunocytes

We constructed a carbon-based polymer dot (CPD) sensor to detect breast cancer based on the differences of peripheral blood cells, providing a new minimally invasive method for cancer diagnosis. This simple and extensible system exhibits clinically relevant accuracy in terms of cancer identification, making it an attractive strategy for diagnosis and prognosis.

Self-Validated Homogeneous Immunoassay by Single Nanoparticle in-Depth Scrutinization

The most convenient method for the clinical routine analysis of disease biomarkers is homogeneous immunoassay, which minimizes the requirements for automation and time-/lab-consumption. Despite great success, because sample constituents are not removed by a separation or washing step, a major challenge in conducting homogeneous immunoassays for the practical application is the matrix effect-related inaccuracy. Herein, to guarantee an accurate quantification, a self-validated homogeneous immunoassay was proposed, by simultaneously scrutinizing both frequency and intensity of single gold nanoparticles. The two analytical modes of single particle inductively coupled plasma mass spectrometry (ICPMS) correlated well with each other, resulting in a self-validation mechanism for the accurate immunoassay. Both two modes of the proposed method provided linear ranges of 2 orders of magnitude and LODs of pM level. Thanks to the self-validated strategy and the high tolerance of the matrix effect of ICPMS, the proposed homogeneous immunoassay was successfully demonstrated in a series of human serum samples, with results in good accordance with clinical routine methods.

Magnetic Nanoparticles for Nanomedicine

The field of nanomedicine has recently emerged as a product of the expansion of a range of nanotechnologies into biomedical science, pharmacology and clinical practice. Due to the unique properties of nanoparticles and the related nanostructures, their applications to medical diagnostics, imaging, controlled drug and gene delivery, monitoring of therapeutic outcomes, and aiding in medical interventions, provide a new perspective for challenging problems in such demanding issues as those involved in the treatment of cancer or debilitating neurological diseases. In this review, we evaluate the role and contributions that the applications of magnetic nanoparticles (MNPs) have made to various aspects of nanomedicine, including the newest magnetic particle imaging (MPI) technology allowing for outstanding spatial and temporal resolution that enables targeted contrast enhancement and real-time assistance during medical interventions. We also evaluate the applications of MNPs to the development of targeted drug delivery systems with magnetic field guidance/focusing and controlled drug release that mitigate chemotherapeutic drugs’ side effects and damage to healthy cells. These systems enable tackling of multiple drug resistance which develops in cancer cells during chemotherapeutic treatment. Furthermore, the progress in development of ROS- and heat-generating magnetic nanocarriers and magneto-mechanical cancer cell destruction, induced by an external magnetic field, is also discussed. The crucial roles of MNPs in the development of biosensors and microfluidic paper array devices (µPADs) for the detection of cancer biomarkers and circulating tumor cells (CTCs) are also assessed. Future challenges concerning the role and contributions of MNPs to the progress in nanomedicine have been outlined.

A facile deoxyuridine/biotin-modified molecular beacon for simultaneous detection of proteins and nucleic acids via a label-free and background-eliminated fluorescence assay

Simultaneous detection of different types of cancer biomarkers (nucleic acids and proteins) could facilitate early diagnosis of cancer and clinical treatment. Herein, a simultaneous detection platform of proteins and nucleic acids has been developed using a single substrate probe combining a label-free and background-eliminated fluorescence assay. Telomerase and telomerase RNA (TR) were chosen as the models. The molecular beacon (dU-BIO-HP) that contains deoxyuridine/biotin in its side arm, a TR recognition sequence in the loop and a telomerase substrate primer at the stem end was ingeniously designed. In the presence of telomerase, the stem of dU-BIO-HP is elongated by the addition of telomere repeats complementary to the assistant DNA. Furthermore, the formed dsDNA performed as engaging primers to initiate a SDA reaction, generating abundant G-quadruplex monomers. Similarly, on TR, the hybridization between TR and dU-BIO-HP can open its stem, triggering another SDA reaction, producing abundant short ssDNAs. With the G-quadruplex binding with ZnPPIX and ssDNA binding with SG for specific fluorescence responses, the label-free multiple detection can be achieved. In our strategy, the deoxyuridine of dU-BIO-HP acts as a barrier to block the DNA extension due to its strong inhibitory effects on DNA polymerase activity and to make sure that the two SDA reactions occurred independently. The biotin of dU-BIO-HP enables the reduction of the background from the binding between SG, ZnPPIX and dU-BIO-HP through streptavidin-biotin interaction. This method showed an excellent sensitivity with telomerase and TR detection limit of 2.18 HeLa cells per mL and 0.16 × 10^-12 M, respectively. Furthermore, the telomerase and TR in different cell lines have been evaluated as powerful tools for biomedical research and clinical diagnosis.