DNA Nanolithography Enables a Highly Ordered Recognition Interface in a Microfluidic Chip for the Efficient Capture and Release of Circulating Tumor Cells

Fabricating Polymeric Micelles with Enrichment and Cavity Effect for In Situ Enzyme Imobilization from Natural Biosystems

Metal-organic frameworks and hydrogen-organic frameworks (MOFs and HOFs) are attractive hosts for enzyme immobilization, but they are limited to immobilizing the purified enzymes, making industrial upscaling unattractive. Herein, aptamer-modified dual thermoresponsive polymeric micelles with switchable self-assembly and core-shell structure are constructed, which enable selective immobilization of trypsin directly from complex biological systems through a cascade operation of separation and immobilization. Their steric self-assembly provides a large amount of adsorption sites on the soluble micellar shell, resulting in high adsorption capacity and excellent selectivity. Meanwhile, their aptamer affinity ligand and cavity maintain the native conformations of trypsin and offer protective effects even in harsh conditions. The maximum adsorption capacity of the polymeric micelles for trypsin was determined to be 197 mg/g at 60 min, superior to those of MOFs and HOFs. 67.2 and 86.6% of its original activity was retained for trypsin immobilized in the cavity under strong alkaline and acidic conditions, respectively.

Investigation of MSC potency metrics via integration of imaging modalities with lipidomic characterization

Mesenchymal stem/stromal cell (MSC) therapies have had limited success so far in clinical trials due in part to heterogeneity in immune-responsive phenotypes. Therefore, techniques to characterize these properties of MSCs are needed during biomanufacturing. Imaging cell shape, or morphology, has been found to be associated with MSC immune responsivity-but a direct relationship between single-cell morphology and function has not been established. We used label-free differential phase contrast imaging and matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) to evaluate single-cell morphology and explore relationships with lipid metabolic immune response. In interferon gamma (IFN-γ)-stimulated MSCs, we found higher lipid abundances from the ceramide-1-phosphate (C1P), phosphatidylcholine (PC), LysoPC, and triglyceride (TAG) families that are involved in cell immune function. Furthermore, we identified differences in lipid signatures in morphologically defined MSC subpopulations. The use of single-cell optical imaging coupled with single-cell spatial lipidomics could assist in optimizing the MSC production process and improve mechanistic understanding of manufacturing process effects on MSC immune activity and heterogeneity.

Sandwich Layer-Modified Ω-Shaped Fiber-Optic LSPR Enables the Development of an Aptasensor for a Cytosensing-Photothermal Therapy Circuit

The metastasis of cancer cells is a principal cause of morbidity and mortality in cancer. The combination of a cytosensor and photothermal therapy (PTT) cannot completely eliminate cancer cells at one time. Hence, this study aimed to design a localized surface plasmonic resonance (LSPR)-based aptasensor for a circuit of cytosensing-PTT (COCP). This was achieved by coating a novel sandwich layer of polydopamine/gold nanoparticles/polydopamine (PDA/AuNPs/PDA) around the Ω-shaped fiber-optic (Ω-FO). The short-wavelength peak of the sandwich layer with strong resonance exhibited a high refractive index sensitivity (RIS). The modification with the T-shaped aptamer endowed FO-LSPR with unique characteristics of time-dependent sensitivity enhancement behavior for a sensitive cytosensor with the lowest limit of detection (LOD) of 13 cells/mL. The long-wavelength resonance peak in the sandwich layer appears in the near-infrared region. Hence, the rate of increased localized temperature of FO-LSPR was 160 and 30-fold higher than that of the bare and PDA-coated FO, indicating strong photothermal conversion efficiency. After considering the localized temperature distribution around the FO under the flow environment, the FO-LSPR-enabled aptasensor killed 77.6% of cancer cells in simulated blood circulation after five cycles of COCP. The FO-LSPR-enabled aptasensor improved the efficiency of the cytosensor and PTT to effectively kill cancer cells, showing significant potential for application in inhibiting cancer metastasis.

Digital Circulating Tumor Cells Quantification

Circulating tumor cells (CTCs) are an emerging but vital biomarker for cancer management. An efficient methodology for accurately quantifying CTCs remains challenging due to their rareness. Here, we develop a digital CTC detection strategy using partitioning instead of enrichment to quantify CTCs. By utilizing the characteristics of droplet microfluidics that can rapidly generate a large number of parallel independent reactors, combined with Poisson distribution, we realize the quantification of CTCs in the blood directly. The limit of detection of our digital CTCs quantification assay is five cells per 5 mL of whole blood. By simultaneously detecting multiple genetic mutations, our approach achieves highly sensitive and specific detection of CTCs in peripheral blood from NSCLC patients (AUC = 1). Our digital platform offers a potential approach and strategy for the quantification of CTCs, which could contribute to the advancement of cancer medical management.

Lowering Entropic Barriers in Triplex DNA Switches Facilitating Biomedical Applications at Physiological pH

Triplex DNA switches are attractive allosteric tools for engineering smart nanodevices, but their poor triplex-forming capacity at physiological conditions limited the practical applications. To address this challenge, we proposed a low-entropy barrier design to facilitate triplex formation by introducing a hairpin duplex linker into the triplex motif, and the resulting triplex switch was termed as CTNSds. Compared to the conventional clamp-like triplex switch, CTNSds increased the triplex-forming ratio from 30 % to 91 % at pH 7.4 and stabilized the triple-helix structure in FBS and cell lysate. CTNSds was also less sensitive to free-energy disturbances, such as lengthening linkers or mismatches in the triple-helix stem. The CTNSds design was utilized to reversibly isolate CTCs from whole blood, achieving high capture efficiencies (>86 %) at pH 7.4 and release efficiencies (>80 %) at pH 8.0. Our approach broadens the potential applications of DNA switches-based switchable nanodevices, showing great promise in biosensing and biomedicine.

Aptamer-Based Nongenetic Reprogramming of CARs Enables Flexible Modulation of T Cell-Mediated Tumor Immunotherapy

Innovating the design of chimeric antigen receptors (CARs) beyond conventional structures would be necessary to address the challenges of efficacy, safety, and applicability in T cell-based cancer therapy, whereas excessive genetic modification might complicate CAR design and manufacturing, and increase gene editing risks. In this work, we used aptamers as the antigen-recognition unit to develop a nongenetic CAR engineering strategy for programming the antitumor activity and specificity of CAR T cells. Our results demonstrated that aptamer-functionalized CAR (Apt-CAR) T cells could be directly activated by recognizing target antigens on cancer cells, and then impart a cytotoxic effect for cancer elimination in vitro and in vivo. The designable antigen recognition capability of Apt-CAR T cells allows for easy modulation of their efficacy and specificity. Additionally, multiple features, e.g., tunable antigen-binding avidity and the tumor microenvironment responsiveness, could be readily integrated into Apt-CAR design without T cell re-engineering, offering a new paradigm for developing adaptable immunotherapeutics.

Functionalized tetrahedral DNA frameworks for the capture of circulating tumor cells

Identification and characterization of circulating tumor cells (CTCs) from blood samples of patients with cancer can help monitor parameters such as disease stage, disease progression and therapeutic efficiency. However, the sensitivity and specificity of current multivalent approaches used for CTC capture is limited by the lack of control over the ligands' position. In this Protocol Update, we describe DNA-tetrahedral frameworks anchored with aptamers that can be configured with user-defined spatial arrangements and stoichiometries. The modified tetrahedral DNA frameworks, termed 'n-simplexes', can be used as probes to specifically target receptor-ligand interactions on the cell membrane. Here, we describe the synthesis and use of n-simplexes that target the epithelial cell adhesion molecule expressed on the surface of CTCs. The characterization of the n-simplexes includes measuring the binding affinity to the membrane receptors as a result of the spatial arrangement and stoichiometry of the aptamers. We further detail the capture of CTCs from patient blood samples. The procedure for the preparation and characterization of n-simplexes requires 11.5 h, CTC capture from clinical samples and data processing requires ~5 h per six samples and the downstream analysis of captured cells typically requires 5.5 h. The protocol is suitable for users with basic expertise in molecular biology and handling of clinical samples.

Revolutionizing targeting precision: microfluidics-enabled smart microcapsules for tailored delivery and controlled release

As promising delivery systems, smart microcapsules have garnered significant attention owing to their targeted delivery loaded with diverse active materials. By precisely manipulating fluids on the micrometer scale, microfluidic has emerged as a powerful tool for tailoring delivery systems based on potential applications. The desirable characteristics of smart microcapsules are associated with encapsulation capacity, targeted delivery capability, and controlled release of encapsulants. In this review, we briefly describe the principles of droplet-based microfluidics for smart microcapsules. Subsequently, we summarize smart microcapsules as delivery systems for efficient encapsulation and focus on target delivery patterns, including passive targets, active targets, and microfluidics-assisted targets. Additionally, based on release mechanisms, we review controlled release modes adjusted by smart membranes and on/off gates. Finally, we discuss existing challenges and potential implications associated with smart microcapsules.

Controllable Assembly of a Quantum Dot-Based Aptasensor Guided by CRISPR/Cas12a for Direct Measurement of Circulating Tumor Cells in Human Blood

Accurate and sensitive analysis of circulating tumor cells (CTCs) in human blood provides a non-invasive approach for the evaluation of cancer metastasis and early cancer diagnosis. Herein, we demonstrate the controllable assembly of a quantum dot (QD)-based aptasensor guided by CRISPR/Cas12a for direct measurement of CTCs in human blood. We introduce a magnetic bead@activator/recognizer duplex core-shell structure to construct a multifunctional platform for the capture and direct detection of CTCs in human blood, without the need for additional CTC release and re-identification steps. Notably, the introduction of magnetic separation ensures that only a target-induced free activator can initiate the downstream catalysis, efficiently avoiding the undesired catalysis triggered by inappropriate recognition of the activator/recognizer duplex structure by crRNAs. This aptasensor achieves high CTC-capture efficiency (82.72%) and sensitive detection of CTCs with a limit of detection of 2 cells mL-1 in human blood, holding great promise for the liquid biopsy of cancers.

Carboxyl graphene modified PEDOT:PSS organic electrochemical transistor for in situ detection of cancer cell morphology

Circulating tumor cells in human peripheral blood play an important role in cancer metastasis. In addition to the size-based and antibody-based capture and separation of cancer cells, their electrical characterization is important for rare cell detection, which can prove fatal in point-of-care testing. Herein, an organic electrochemical transistor (OECT) biosensor made of solution-gated carboxyl graphene mixed with PEDOT:PSS for the detection of cancer cells in situ is reported. Carboxyl graphene was used in this work to modulate cancer cell morphology, which differs significantly from normal blood cells, to achieve rare cancer cell detection. When the concentration of carboxyl graphene mixed in PEDOT:PSS was increased from 0 to 5 mg mL-1, the cancer cell surface area increased from 218 μm2 to 530 μm2, respectively. A change in cell morphology was also detected by the OECT. Negative charges in the cancer cells induced a positive shift in gate voltage, which was approximately 40 mV for spherical-shaped cells. When the cell surface area increased, transfer curves of transistor revealed a negative shift in gate voltage. Therefore, the sensor can be used for in situ detection of cancer cell morphology during the cell capture process, which can be used to identify whether the captured cells are deformable.

Accurate Cancer Screening and Prediction of PD-L1-Guided Immunotherapy Efficacy Using Quantum Dot Nanosphere Self-Assembly and Machine Learning

Accurate quantification of exosomal PD-L1 protein in tumors is closely linked to the response to immunotherapy, but robust methods to achieve high-precision quantitative detection of PD-L1 expression on the surface of circulating exosomes are still lacking. In this work, we developed a signal amplification approach based on aptamer recognition and DNA scaffold hybridization-triggered assembly of quantum dot nanospheres, which enables bicolor phenotyping of exosomes to accurately screen for cancers and predict PD-L1-guided immunotherapeutic effects through machine learning. Through DNA-mediated assembly, we utilized two aptamers for simultaneous ultrasensitive detection of exosomal antigens, which have synergistic roles in tumor diagnosis and treatment prediction, and thus, we achieved better sample classification and prediction through machine-learning algorithms. With a drop of blood, we can distinguish between different cancer patients and healthy individuals and predict the outcome of immunotherapy. This approach provides valuable insights into the development of personalized diagnostics and precision medicine.

Enhanced portable detection for Sars-CoV-2 utilizing DNA tetrahedron-tethered aptamers and a pressure meter

Tethering oligonucleotide aptamers to a DNA tetrahedron structure can enhance the recognition of SARS-CoV-2 spike protein to effectively overcome challenges with its detection in current diagnostic assays. Building on this framework, we have developed a unique portable detection method for COVID-19 that provides exceptional sensitivity and selectivity via pressure meter readout. This innovative assay streamlines the detection process, providing a rapid, sensitive, cost-effective, and user-friendly diagnostic tool. This point-of-care test exhibits high sensitivity and specificity, achieving an impressive detection limit of 0.1 pg mL-1 for the spike protein. The effectiveness of this method was validated using pseudoviruses and oropharyngeal swab samples, and its utility for environmental monitoring is demonstrated by testing sewage samples. With a wide linear range and strong potential for clinical or home application, our assay represents a major innovation in point-of-care diagnostics and provides a vital contribution to the current toolkit for controlling the impacts of COVID-19.

Multivalent DNA Flowers for High-Performance Isolation, Detection, and Release of Tumor-Derived Extracellular Vesicles

Tumor-derived extracellular vesicles (T-EVs) hold great promise for understanding cancer biology and improving cancer diagnostics and therapeutics. Herein, we developed multivalent DNA flowers (DFs) containing repeated and equidistant EpCAM aptamers for the efficient isolation of T-EVs. The multivalent aptamer chains in DFs had good flexibility to adapt to the surface morphology of T-EVs and achieved multivalent ligand-receptor interactions, thus showing enhanced isolation ability compared to monovalent aptamers. Compared with other materials for isolation of EVs, DFs were generated by rolling circle amplification (RCA) and self-assembled into microspheres in a one-pot reaction, and the recognition molecules (aptamers) were directly replicated and assembled during the RCA reaction instead of chemical modification and immobilization on the surface of solid materials. Moreover, as optically transparent biomaterials, the content of EpCAM+ EVs could be directly reflected via membrane-based hydrophobic assembly of signaling modules in DFs@EpCAM+ EVs complex, and we found that the amount of EpCAM+ EVs showed greater accuracy in cancer diagnosis than total EVs (88.3 vs 69.7%) and was also higher than the clinically commonly used marker carcinoembryonic antigen (CEA) (88.3 vs 76.7%). In addition, T-EVs could be released by lysis of DFs with the nuclease, gently and easily, keeping high intact and activity of EVs for downstream biological function studies. These results demonstrated that DFs are efficient and nondestructive tools for isolation, detection, and release of T-EVs.

Interfacial Polymerization Produced Magnetic Particles with Nano-Filopodia for Highly Accurate Liquid Biopsy in the PSA Gray Zone

Magnetic particles are leading separation materials for biological purification and detection. Existing magnetic particles, which almost rely on molecule-level interactions, however, often encounter bottlenecks in highly efficient cell-level separation due to the underestimate of surface structure effects. Here, immune cell-inspired magnetic particles with nano-filopodia (NFMPs) produced by interfacial polymerization for highly efficient capture of circulating tumor cells (CTCs) and further accurate clinical diagnosis of prostate cancer are reported . The unprecedented construction of nano-filopodia on polymer-based magnetic particles is achieved by introducing electrostatic interactions in emulsion interfacial polymerization. Due to the unique nano-filopodia, the NFMPs allow remarkably enhanced CTCs capture efficiency (86.5% ± 2.8%) compared with smooth magnetic particles (SMPs, 35.7% ± 5.7%). Under the assistance of machine learning by combining with prostate-specific antigen (PSA) and free to total PSA (F/T-PSA), the NFMPs strategy demonstrates high sensitivity (100%), high specificity (93.3%), and a high area under the curve (AUC) value (98.1%) for clinical diagnosis of prostate cancer in the PSA gray zone. The NFMPs are anticipated as an efficient platform for CTCs-based liquid biopsy toward early cancer diagnosis and prognosis evaluation.

DNA-Programmed Stem Cell Niches via Orthogonal Extracellular Vesicle-Cell Communications

Extracellular vesicles (EVs) are natural carriers for intercellular transfer of bioactive molecules, which are harnessed for wide biomedical applications. However, a facile yet general approach to engineering interspecies EV-cell communications is still lacking. Here, the use of DNA to encode the heterogeneous interfaces of EVs and cells in a manner free of covalent or genetic modifications is reported, which enables orthogonal EV-cell interkingdom interactions in complex environments. Cholesterol-modified DNA strands and tetrahedral DNA frameworks are employed with complementary sequences to serve as artificial ligands and receptors docking on EVs and living cells, respectively, which can mediate specific yet efficient cellular internalization of EVs via Watson-Crick base pairing. It is shown that based on this system, human cells can adopt EVs derived from the mouse, watermelon, and Escherichia coli. By implementing several EV-cell circuits, it shows that this DNA-programmed system allows orthogonal EV-cell communications in complex environments. This study further demonstrates efficient delivery of EVs with bioactive contents derived from feeder cells toward monkey female germline stem cells (FGSCs), which enables self-renewal and stemness maintenance of the FGSCs without feeder cells. This system may provide a universal platform to customize intercellular exchanges of materials and signals across species and kingdoms.

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.

Isolation of PD-L1 Extracellular Vesicle Subpopulations Using DNA Computation Mediated Microfluidic Tandem Separation

Accurate isolation of targeted extracellular vesicle (EV) is challenging due to the antigenic heterogeneity of EV subpopulations which are from different cell origins. Most EV subpopulations lack a single marker whose expression cleanly distinguishes them from mixed populations of closely related EVs. Here, a modular platform capable of taking multiple binding events as input, performing logic computations, and producing two independent outputs for tandem microchips for EV subpopulation isolation, is developed. Taking advantages of the excellent selectivity of dual-aptamer recognition and the sensitivity of tandem microchips, this method achieves, for the first time, sequential isolation of tumor PD-L1 EVs and non-tumor PD-L1 EVs. As a result, the developed platform can not only effectively distinguish cancer patients from healthy donors but also provides new clues for assessing immune heterogeneity. Moreover, the captured EVs can be released through a DNA hydrolysis reaction with high efficiency, which is compatible with downstream mass spectrometry for EV proteome profiling. Overall, this strategy is expected to isolate different EV subpopulations, translate EVs into reliable clinical biomarkers, and accurately investigate the biological functions of different EV subsets.

Microfluidic systems for particle capture and release: A review

Microfluidic technology has emerged as a promising tool in various applications, including biosensing, disease diagnosis, and environmental monitoring. One of the notable features of microfluidic devices is their ability to selectively capture and release specific cells, biomolecules, bacteria, and particles. Compared to traditional bulk analysis instruments, microfluidic capture-and-release platforms offer several advantages, such as contactless operation, label-free detection, high accuracy, good sensitivity, and minimal reagent requirements. However, despite significant efforts dedicated to developing innovative capture mechanisms in the past, the release and recovery efficiency of trapped particles have often been overlooked. Many previous studies have focused primarily on particle capture techniques and their efficiency, disregarding the crucial role of successful particle release for subsequent analysis. In reality, the ability to effectively release trapped particles is particularly essential to ensure ongoing, high-throughput analysis. To address this gap, this review aims to highlight the importance of both capture and release mechanisms in microfluidic systems and assess their effectiveness. The methods are classified into two categories: those based on physical principles and those using biochemical approaches. Furthermore, the review offers a comprehensive summary of recent applications of microfluidic platforms specifically designed for particle capture and release. It outlines the designs and performance of these devices, highlighting their advantages and limitations in various target applications and purposes. Finally, the review concludes with discussions on the current challenges faced in the field and presents potential future directions.

Bioorthogonal Microbubbles with Antifouling Nanofilm for Instant and Suspended Enrichment of Circulating Tumor Cells

Integrating clinical rare cell enrichment, culture, and single-cell phenotypic profiling is currently hampered by the lack of competent technologies, which typically suffer from weak cell-interface collision affinity, strong nonspecific adsorption, and the potential uptake. Here, we report cells-on-a-bubble, a bioinspired, self-powered bioorthogonal microbubble (click bubble) that leverages a clickable antifouling nanointerface and a DNA-assembled sucker-like polyvalent cell surface, to enable instant and suspended isolation of circulating tumor cells (CTCs) within minutes. Using this biomimetic engineering strategy, click bubbles achieve a capture efficiency of up to 98%, improved by 20% at 15 times faster over their monovalent counterparts. Further, the buoyancy-activated bubble facilitates self-separation, 3D suspension culture, and in situ phenotyping of the captured single cancer cells. By using a multiantibody design, this fast, affordable micromotor-like click bubble enables suspended enrichment of CTCs in a cohort (n = 42) across three cancer types and treatment response evaluation, signifying its great potential to enable single-cell analysis and 3D organoid culture.

Three-Dimensional PLGA Nanofiber-Based Microchip for High-Efficiency Cancer Cell Capture

A 3D network capture substrate based on poly(lactic-co-glycolic acid) (PLGA) nanofibers was studied and successfully used for high-efficiency cancer cell capture. The arc-shaped glass micropillars were prepared by chemical wet etching and soft lithography. PLGA nanofibers were coupled with micropillars by electrospinning. Given the size effect of the microcolumn and PLGA nanofibers, a three-dimensional of micro-nanometer spatial network was prepared to form a network cell trapping substrate. After the modification of a specific anti-EpCAM antibody, MCF-7 cancer cells were captured successfully with a capture efficiency of 91%. Compared with the substrate composed of 2D nanofibers or nanoparticles, the developed 3D structure based on microcolumns and nanofibers had a greater contact probability between cells and the capture substrate, leading to a high capture efficiency. Cell capture based on this method can provide technical support for rare cells in peripheral blood detection, such as circulating tumor cells and circulating fetal nucleated red cells.

Aptamer-Mediated Enrichment of Rare Circulating Fetal Nucleated Red Blood Cells for Noninvasive Prenatal Diagnosis

Isolation of circulating fetal nucleated red blood cells (cfNRBCs) from maternal peripheral blood provides a superior strategy for noninvasive prenatal genetic diagnosis. Recent technical advances in single-cell isolation and genetic analyses have promoted the clinical application of circulating fetal cell-based noninvasive prenatal diagnosis. However, the lack of highly specific ligands for rare circulating fetal cell enrichment from massive maternal cells significantly impedes the clinical transformation progress. In this work, aptamers specific to NRBCs were developed through clinical sample-based cell-SELEX. Herein, the complex clinical system provides natural selection stringency through binding competition between target and background cells, and it empowers aptamers with high specificity. An aptamer-based strategy was also established to isolate cfNRBCs from maternal peripheral blood. Results show the remarkable selectivity and affinity of developed aptamers, enabling efficient enrichment of cfNRBCs from abundant maternal cells. Moreover, screening for fetal sex and trisomy syndrome achieved high accuracy through chromosome analysis of enriched cfNRBCs. To the best of our knowledge, this is the first report to develop aptamer ligands for cfNRBC enrichment, providing an efficient strategy to screen cfNRBC-specific ligands and demonstrating broad application potential for cfNRBC-based noninvasive prenatal diagnosis.

μ-opioid receptor agonist facilitates circulating tumor cell formation in bladder cancer via the MOR/AKT/Slug pathway: a comprehensive study including randomized controlled trial

BACKGROUND

μ-opioid receptor agonists (MORAs) are indispensable for analgesia in bladder cancer (BC) patients, both during surgery and for chronic pain treatment. Whether MORAs affect BC progression and metastasis remains largely unknown. This study focused on the effects of MORAs on the formation of circulating tumor cells (CTCs) in BC and aimed to provide potential therapeutic targets, which would retain the pain-relieving effects of MORAs in BC patients without sacrificing their long-term prognosis.

METHODS

Different preclinical models were used to identify the effects of MORAs on the progression of BC. A novel immunocapture microfluidic chip was utilized to analyze whether MORAs affected the number of CTCs in mouse models and clinical BC patients. Bioinformatic analyses, total transcriptome sequencing, and molecular biology methods were then used to investigate the underlying mechanisms in these models and in BC cell lines.

RESULTS

Mouse models of hematogenous metastasis and in situ BC demonstrated that tumor metastasis was significantly increased after MORA treatment. A significant increase in the number of mesenchymal and/or epithelial CTCs was detected after MORA treatment in both the mouse models and clinical trial patients. Mechanistically, MORAs facilitated the formation of CTCs by activating the MOR/PI3K/AKT/Slug signaling pathway, hereby promoting the epithelial-mesenchymal transition (EMT) of BC cells, as knockdown of MOR, Slug or blockade of PI3K inhibited the EMT process and CTC formation.

CONCLUSION

MORAs promoted BC metastasis by facilitating CTC formation. The EMT-CTC axis could be targeted for preventive measures during MORA treatment to inhibit the associated tumor metastasis or recurrence in BC patients.

Recent progress in aptamer-based microfluidics for the detection of circulating tumor cells and extracellular vesicles

Liquid biopsy is a technology that exhibits potential to detect cancer early, monitor therapies, and predict cancer prognosis due to its unique characteristics, including noninvasive sampling and real-time analysis. Circulating tumor cells (CTCs) and extracellular vesicles (EVs) are two important components of circulating targets, carrying substantial disease-related molecular information and playing a key role in liquid biopsy. Aptamers are single-stranded oligonucleotides with superior affinity and specificity, and they can bind to targets by folding into unique tertiary structures. Aptamer-based microfluidic platforms offer new ways to enhance the purity and capture efficiency of CTCs and EVs by combining the advantages of microfluidic chips as isolation platforms and aptamers as recognition tools. In this review, we first briefly introduce some new strategies for aptamer discovery based on traditional and aptamer-based microfluidic approaches. Then, we subsequently summarize the progress of aptamer-based microfluidics for CTC and EV detection. Finally, we offer an outlook on the future directional challenges of aptamer-based microfluidics for circulating targets in clinical applications.

Dynamic DNA Nanostructures for Cell Manipulation

Dynamic DNA nanostructures are DNA nanostructures with reconfigurable elements that can undergo structural transformations in response to specific stimuli. Thus, anchoring dynamic DNA nanostructures on cell membranes is an attractive and promising strategy for well-controlled cell manipulation. Here, we review the latest progress in dynamic DNA nanostructures for cell manipulation. Commonly used mechanisms for dynamic DNA nanostructures are first introduced. Subsequently, we summarize the anchoring strategies for dynamic DNA nanostructures on cell membranes and list possible applications (including programming cell membrane receptors, controlling ligand activity and drug delivery, capturing and releasing cells, and assembling cells into clusters). Finally, insights into the remaining challenges are presented.

Thermodynamic and Kinetic Modulation of Microfluidic Interfaces by DNA Nanoassembly Mediated Merit-Complementary Heteromultivalency

The multivalent effect is often used to engineer microfluidic affinity interfaces to improve the target separation efficiency. Currently, no design rules exist for thermodynamic and kinetic tuning of properly joining multiple ligands. Herein, we developed a thermodynamic and kinetic modulating strategy of the microfluidic affinity interface via a merit-complementary-heteromultivalent aptamers functionalized DNA nanoassembly. Our strategy is built on the two types of identified aptamers that bind to distinct sites of EpCAM. The aptamer binding of one type is more rapid but less tight, while the other is opposite. By assembling the two types of aptamers together with a tetrahedral DNA framework, we fully exploited these aptamers' merits for tight and rapid recognition of EpCAM, leading to target cell capture with high efficiency and throughput. Our strategy provides a perspective on engineering multivalent recognition molecules through thermodynamic and kinetic tuning.

Facile Preparation of Three-Dimensional Wafer with Interconnected Porous Structure for High-Performance Capture and Nondestructive Release of Circulating Tumor Cells

Efficient isolation and downstream bioinformation analysis of circulating tumor cells (CTCs) in whole blood contribute to the early diagnosis of cancer and investigation of cancer metastasis. However, the separation and release of CTCs remain a great challenge due to the extreme rarity of CTCs and severe interference from other cells in complex clinical samples. Herein, we developed a low-cost and easy-to-fabricate aptamer-functionalized wafer with a three-dimensional (3D) interconnected porous structure by grafting polydopamine (PDA), poly(ethylene glycol) (PEG), and aptamer in sequence (Ni@PDA-PEG-Apt) for the capture and release of CTCs. The Ni@PDA-PEG-Apt wafer integrated the features of Ni foam with a 3D interconnected porous structure offering enough tunnels for cells to flow through and enhancing aptamer-cell contact frequency, the spacer PEG with flexible and high hydrophilic property increasing anti-interference ability and providing the wafer with more binding sites for aptamer, which result in an enhanced capture specificity and efficiency for CTCs. Because of these advantages, the Ni@PDA-PEG-Apt wafer achieved a high capture efficiency of 78.25%. The captured cancer cells were mildly released by endonuclease with up to 61.85% efficiency and good proliferation. Furthermore, tumor cells were injected into mice and experienced circulation in vivo. In blood samples after circulation, 65% of target tumor cells can be efficiently captured by the wafer, followed by released and recultured cells with high viability. Further downstream metabolomics analysis showed that target cancer cells remained with high biological activity and can be well separated from MCF-10A cells based on metabolic profiles by the PCA analysis, indicating the great potential of our strategy for further research on the progression of cancer metastasis. Notably, not only is the wafer cheap with a cost of only 3.58 U.S. dollars and easily prepared by environmental-friendly reagents but also the process of capturing and releasing tumor cells can be completed within an hour, which is beneficial for large-scale clinical use in the future.

Flap Endonuclease-Induced Steric Hindrance Change Enables the Construction of Multiplex and Versatile Lateral Flow Strips for DNA Detection

A lateral flow strip (LFS) is an ideal tool for point-of-care testing (POCT), but traditional LFSs cannot be used for multiplex detection. Herein, a multiplex and versatile LFS based on flap endonuclease 1 (FEN1)-induced steric hindrance change (FISH-LFS) is proposed. In this method, multiplex PCR coupled with cascade invasive reactions was employed to yield single-stranded flaps, which were target-specific but independent of target sequences. Then, the amplicons were applied for FISH-LFS, and the single-stranded flaps would be efficiently captured by the complementary LFS-probes at different test lines. As flaps were cleaved from the specially designed hairpin probes, competition among flaps and hairpin probes would occur in capturing the probes at test lines. We enabled the hairpin probes to flow through the test lines while the flaps to stay at the test lines by making use of the difference in steric hindrance between hairpin probes and flaps. The assay is able to detect as low as two copies of blood pathogens (HBV, HCV, and HIV), to pick up as low as 0.1% mutants from wild-type gDNA, and to genotype 200 copies of SARS-CoV-2 variants α and β within 75 min at a conventional PCR engine. As the method is free of dye, a portable PCR engine could be used for a cost-effective multiplex detection on site. Results using an ultrafast mobile PCR system for FISH-LFS showed that as fast as 30 min was achieved for detecting three pathogens (HBV, HCV, and HIV) in blood, very suitable for POCT of pathogen screening. The method is convenient in operation, simple in instrumentation, specific in genotyping, and very easy in setting up multiplex POCT assays.

Mechanosensing view of SARS-CoV-2 infection by a DNA nano-assembly

The mechanical force between a virus and its host cell plays a critical role in viral infection. However, characterization of the virus-cell mechanical force at the whole-virus level remains a challenge. Herein, we develop a platform in which the virus is anchored with multivalence-controlled aptamers to achieve transfer of the virus-cell mechanical force to a DNA tension gauge tether (Virus-TGT). When the TGT is ruptured, the complex of binding module-virus-cell is detached from the substrate, accompanied by decreased host cell-substrate adhesion, thus revealing the mechanical force between whole-virus and cell. Using Virus-TGT, direct evidence about the biomechanical force between SARS-CoV-2 and the host cell is obtained. The relative mechanical force gap (<10 pN) at the cellular level between the wild-type virus to cell and a variant virus to cell is measured, suggesting a possible positive correlation between virus-cell mechanical force and infectivity. Overall, this strategy provides a new perspective to probe the SARS-CoV-2 mechanical force.

Designer tetrahedral DNA framework-based microfluidic technology for multivalent capture and release of circulating tumor cells

Circulating tumor cells (CTCs) have been recognized as a general biomarker for the early detection, diagnosis and therapy monitoring of cancer. Due to their extreme rarity in peripheral blood, the isolation and analysis of CTCs with high efficiency, high purity and high viability remains a tremendous technological challenge. Herein, we combined tetrahedral DNA framework (TDFs), herringbone channel (HB) chip, together with aptamer-triggered hybridization chain reaction (apt-HCR) to develop an efficient microfluidic system (T-μFS) for capture and release of simulated CTCs. The capture efficiency of MCF-7 ​cells was from 83.3% to 94.2% when the cell numbers ranged from 10 to 10³ using our T-μFS in the whole blood. The release efficiency of the MCF-7 ​cells was 96.2% and the MCF-7 ​cell viability after release was 94.6% using our T-μFS in PBS buffer. Reculture and RT-qPCR studies showed that there was almost no damage by the capture and release treatment for the MCF-7 ​cells viability. These results revealed that our T-μFS could be developed as an integrated and automatic technical platform with great performance for multivalent capture and release of CTCs and have a wide application prospect for tumor liquid biopsy.

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Three-dimensional amine modified tetrahedral DNA frameworks (TDFs) as rigid scaffolds were anchored on the aldehyde modified substrate of HB-chip, which provided the better spatial orientation compared with single-stranded DNA.

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Aptamer partially hybridized to an initiator was employed to trigger HCR reaction, and HCR produced modified long products with multi-branched arms for multivalent binding on TDFs to improve the capture efficiency of CTCs.

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This is the first time that only employed DNA nanostructures in a microfluidic device system to capture CTCs, and all DNA nanostructures could be efficiently removed by enzymes without harming cells.

Reversible and Highly Ordered Biointerfaces for Efficient Capture and Nondestructive Release of Circulating Tumor Cells

The engineering strategy of artificial biointerfaces is vital for governing their performances in bioanalysis and diagnosis. Highly ordered arrangement of affinity ligands on the interface surface facilitates efficient interaction with target molecules, whereas biointerfaces aimed at drug delivery or rare cell isolation require sophisticated stimuli-response mechanisms. However, it is still challenging to facilely fabricate biointerfaces possessing the two features. Herein, we endow a biointerface with both reversibility and capability to orderly assemble affinity ligands by introducing boronic acid moieties alone. By boronate conjugation via glycosylation sites, avidin was well arranged at the surface of boronic acid-decorated carbon nitride nanosheets for the assembly of biotinylated aptamers. The ordered orientation of aptamers largely relieved their inactivation caused by inter-strand entanglement, facilitating significant increase in cell affinity for the isolation of circulating tumor cells (CTCs). The reversible boronate conjugation also facilitated mild release of CTCs by acid fructose with high cell viability. This engineered interface was capable of isolating CTCs from the peripheral blood of tumor-bearing mice and cancer patients. The successful utilization of the isolated CTCs in the downstream drug susceptibility test and mutation analysis demonstrated the clinical potential of this biointerface for the early diagnosis of cancers and precision medicine.

DNA-Programmed Orientation-Ordered Multivalent Microfluidic Interface for Liquid Biopsy

Aptamer-functionalized microfluidic interfaces hold great potential for liquid biopsies owing to their programmable nature. However, most previous studies have focused on development of multivalent aptamers to improve binding affinity, while ignoring aptamer orientation on microfluidic interfaces, resulting in suboptimal accessibility and affinity. Herein, we report a Cubic DNA Nanostructure (CDN)-programmed strategy to precisely control the orientation and valency of the Aptamer on a microfluidic interface (CDN-Apt-Chip) for enhancing the capture and release of circulating tumor cells (CTCs). We demonstrate that the ordered orientation and multivalent configuration can synergistically increase the binding affinity of aptamers toward CTCs. By using CDN-Apt-Chip, we successfully isolated CTCs from the peripheral blood of T-cell leukemia patients and discriminated T-cell leukemia patients from healthy volunteers. Furthermore, the captured CTCs were nondestructively released via nuclease treatment. We then performed T-cell receptor sequencing on the released cells to demonstrate the compatibility with downstream analysis. Overall, this study provides a new paradigm for interface regulation of functional microfluidic chips and advances the clinical translation of aptamer-based liquid biopsy.

Spatial confinement toward creating artificial living systems

Lifeforms are regulated by many physicochemical factors, and these factors could be controlled to play a role in the construction of artificial living systems. Among these factors, spatial confinement is an important one, which mediates biological behaviors at multiscale levels and participates in the biomanufacturing processes accordingly. This review describes how spatial confinement, as a fundamental biological phenomenon, provides cues for the construction of artificial living systems. Current knowledge about the role of spatial confinement in mediating individual cell behavior, collective cellular behavior, and tissue-level behavior are categorized. Endeavors on the synthesis of biomacromolecules, artificial cells, engineered tissues, and organoids in spatially confined bioreactors are then emphasized. After that, we discuss the cutting-edge applications of spatially confined artificial living systems in biomedical fields. Finally, we conclude by assessing the remaining challenges and future trends in the context of fundamental science, technical improvement, and practical applications.

Accurate Isolation of Circulating Tumor Cells via a Heterovalent DNA Framework Recognition Element-Functionalized Microfluidic Chip

Detection of circulating tumor cells (CTCs) has provided a noninvasive and efficient approach for early diagnosis, treatment, and prognosis of cancer. However, efficient capture of CTCs in the clinical environment is very challenging because of the extremely rare and heterogeneous expression of CTCs. Herein, we fabricated a multimarker microfluidic chip for the enrichment of heterogeneous CTCs from peripheral blood samples of breast cancer patients. The multimarker aptamer cocktail DNA nanostructures (TP-multimarker) were modified on a deterministic lateral displacement (DLD)-patterned microfluidic chip to enhance the capture efficiency through the size selection effect of DLD arrays and the synergistic effect of multivalent aptamers. As compared to a monovalent aptamer-modified chip, the multimarker chip exhibits enhanced capture efficiency toward both high and low epithelial cell adhesion molecule expression cell lines, and the DNA nanostructure-functionalized chip enables the accurate capture of different phenotypes of CTCs. In addition, the DNA nanoscaffold makes nucleases more accessible to the aptamers to release cells with molecular integrity and outstanding cell viability.

Unbiased Enrichment of Circulating Tumor Cells Via DNAzyme-Catalyzed Proximal Protein Biotinylation

Circulating tumor cells (CTCs) are noninvasive biomarkers with great potential for assessing neoplastic diseases. However, the enrichment bias toward heterogeneous CTCs remains to be minimized. Herein, a DNAzyme-catalyzed proximal protein biotinylation (DPPB) strategy is established for unbiased CTCs enrichment, employing DNA-framework-based, aptamer-coupled DNAzymes that bind to the surface marker of CTCs and subsequently biotinylated membrane proteins in situ. The DNA framework enables the construction of multivalent DNAzyme and serves as steric hindrance to avoid undesired interaction between DNAzymes and aptamer, leading to efficient binding and biotinylation. Compared with a biotinylated-aptamer strategy, fivefold lower bias of cell subpopulations was achieved by DPPB before and after capture, which enabled a 4.6-fold performance for CTCs analysis in clinic blood samples. DPPB is envisioned to offer a new solution for CTC-based cancer diagnostics.

A dual-recognition-controlled electrochemical biosensor for accurate and sensitive detection of specific circulating tumor cells

Accurate and sensitive assay of specific circulating tumor cells (CTCs) is of importance for the diagnosis, treatment, and metastasis monitoring of cancer. Herein, we have proposed a dual-recognition-controlled electrochemical biosensor in this work for the detection of specific CTCs. To this sensor, two aptamer hairpin probes are designed to be able to separately bind to two adjacent proteins on the cell membrane to activate the associative toehold for strand displacement reaction, which will then trigger a dimer-like rolling cycle amplification reaction, and finally produce significantly amplified electrochemical signals for sensitive quantification of target CTCs. In our design, only the case that the two proteins are simultaneously expressed on the cell membrane can result in obvious signal responses, which may greatly improve the accuracy of CTCs analysis. The proposed biosensor can possess excellent selectivity to distinguish target cells from different cancer cells. Moreover, the combination of rolling cycle amplification and DNA nanostructure capture probes can effectively lower the detection limit to 3 cells mL^-1. Notably, our biosensor can be applied to the assay of the target CTCs in the complex whole blood matrixes, verifying its strong stability and anti-interference. Thus, the as-proposed dual-recognition-controlled electrochemical biosensor may exhibit great promise in clinical cancer diagnosis and personalized medicine.

Recent Advances in Aptamer-Based Liquid Biopsy

Liquid biopsy capable of noninvasive and real-time molecular profiling is considered as a breakthrough technology, endowing an opportunity for precise diagnosis of individual patients. Extracellular vesicles (EVs) and circulating tumor cells (CTCs) consisting of substantial disease-related molecular information play an important role in liquid biopsy. Therefore, it is critically significant to exploit high-performance recognition ligands for efficient isolation and analysis of EVs and CTCs from complex body fluids. Aptamers exhibit extraordinary merits of high specificity and affinity, which are considered as superior recognition ligands for liquid biopsy. In this review, we first summarize recent advanced strategies for the evolution of high-performance aptamers and the construction of various aptamer-based recognition elements. Subsequently, we mainly discuss the isolation and analysis of EVs and CTCs based on the aptamer functioned biomaterials/biointerface. Ultimately, we envision major challenges and future direction of aptamer-based liquid biopsy for clinical utilities.

A CRISPR/Cas12a-responsive dual-aptamer DNA network for specific capture and controllable release of circulating tumor cells

The separation and detection of circulating tumor cells (CTCs) have a significant impact on clinical diagnosis and treatment by providing a predictive diagnosis of primary tumors and tumor metastasis.

Antibody-engineered red blood cell interface for high-performance capture and release of circulating tumor cells

Circulating tumor cells (CTCs), as important liquid biopsy target, can provide valuable information for cancer progress monitoring and individualized treatment. However, current isolation platforms incapable of balancing capture efficiency, specificity, cell viability, and gentle release have restricted the clinical applications of CTCs. Herein, inspired by the structure and functional merits of natural membrane interfaces, we established an antibody-engineered red blood cell (RBC-Ab) affinity interface on microfluidic chip for high-performance isolation and release of CTCs. The lateral fluidity, pliability, and anti-adhesion property of the RBC microfluidic interface enabled efficient CTCs capture (96.5%), high CTCs viability (96.1%), and high CTCs purity (average 4.2-log depletion of leukocytes). More importantly, selective lysis of RBCs by simply changing the salt concentration was utilized to destroy the affinity interface for efficient and gentle release of CTCs without nucleic acid contamination. Using this chip, CTCs were successfully detected in colon cancer samples with 90% sensitivity and 100% specificity (20 patients and 10 healthy individuals). After the release process, KRAS gene mutations of CTCs were identified from all the 5 cancer samples, which was consistent with the results of tissue biopsy. We expect this RBC interface strategy will inspire further biomimetic interface construction for rare cell analysis.

State-of-the-arts techniques and current evolving approaches in the separation and detection of circulating tumor cell

Circulating tumor cells (CTCs) are cancer cells that shed from the primary tumor and then enter the circulatory system, a small part of which may evolve into metastatic cancer under appropriate microenvironment conditions. The detection of CTCs is a truly noninvasive, dynamic monitor for disease changes, which has considerable clinical implications in the selection of targeted drugs. However, their inherent rarity and heterogeneity pose significant challenges to their isolation and detection. Even the "gold standard", CellSearch™, suffers from high expenses, low capture efficiency, and the consumption of time. With the advancement of CTCs analysis technologies in recent years, the yield and efficiency of CTCs enrichment have gradually been improved, as well as detection sensitivity. In this review, the isolation and detection strategies of CTCs have been completely described and the potential directions for future research and development have also been highlighted through analyzing the challenges faced by current strategies.

Recent Advances on Functional Nucleic-Acid Biosensors

In the past few decades, biosensors have been gradually developed for the rapid detection and monitoring of human diseases. Recently, functional nucleic-acid (FNA) biosensors have attracted the attention of scholars due to a series of advantages such as high stability and strong specificity, as well as the significant progress they have made in terms of biomedical applications. However, there are few reports that systematically and comprehensively summarize its working principles, classification and application. In this review, we primarily introduce functional modes of biosensors that combine functional nucleic acids with different signal output modes. In addition, the mechanisms of action of several media of the FNA biosensor are introduced. Finally, the practical application and existing problems of FNA sensors are discussed, and the future development directions and application prospects of functional nucleic acid sensors are prospected.

Evaporation-Induced rGO Coatings for Highly Sensitive and Non-Invasive Diagnosis of Prostate Cancer in the PSA Gray Zone

The prostate-specific antigen (PSA) has been widely used for the early diagnosis of prostate cancer during routine check-ups. However, the low sensitivity of regular PSA tests in the PSA gray zone often means that patients are required to undergo further invasive needle biopsy for the diagnosis of prostate cancer, which may lead to potential overdiagnosis and overtreatment. In this study, a circulating tumor cell (CTC)-chip based on an evaporation-induced reduced graphene oxide (rGO) coating is presented, which enables a highly specific and non-invasive diagnosis of prostate cancer in the PSA gray zone. During the evaporation process of the rGO dispersion, the Marangoni effect induces the self-assembly of a hierarchical micro/nanowrinkled rGO coating, which can capture CTCs after subsequent surface modification of capture agents. Compared to the low diagnostic sensitivity (58.3%) of regular PSA tests, a combination of CTC detection and PSA-based hematological tests via machine-learning analysis can greatly upgrade the diagnostic sensitivity of this disease to 91.7% in clinical trial. Therefore, this study provides a non-invasive alternative with high sensitivity for the diagnosis of prostate cancer in the PSA gray zone.

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.

Dual amplified ratiometric fluorescence ELISA based on G-quadruplex/hemin DNAzyme using tetrahedral DNA nanostructure as scaffold for ultrasensitive detection of dibutyl phthalate in aquatic system

Dibutyl phthalate (DBP) is considered as one of the most widely used phthalate esters (PAEs), which has attracted worldwide concerns because of its potential threats to eco-environments and human health. Systematic investigations of DBP environmental occurrence contribute to the further risk assessment, which depends on effective and available analytical methods. In this study, an amplified ratiometric fluorescence ELISA was established for sensitive and high-throughput detection of DBP in the aquatic system based on a novel tetrahedral DNA nanostructure (TDN)-scaffolded-DNAzyme (Tetrazyme). Wherein, Tetrazyme was prepared by the precise folding of G-quadruplex sequence on three vertex angles of the TDN, together with hemin as the horseradish peroxidase (HRP)-mimicking enzyme. The rigid TDN avoided the local overcrowding effect to provide a reasonable spatial spacing on the interface for G-quadruplex sequence, increasing the collision chance between DNAzyme and substrates, improving the catalytic ability of DNAzyme effectively. Besides, streptavidin (SA) and biotin (bio) were used to anchor TDN and antibody, in which the specific binding of SA/bio could make more Tetrazyme conjugate on each signal element, resulting in the dual signal amplification. Meanwhile, the accuracy and precision were enhanced owing to the inherent built-in rectification to the environment from the dual output ratiometric fluorescence assay. Under the optimized conditions, the detection limit of this proposed method was 0.17 ng/mL (16 times lower than that of conventional ELISA using the same antibody) with a satisfactory accuracy (recoveries, 79.0%- 116.2%; CV, 2.1-6.5%). Overall, this platform provides a promising way for accurate, sensitive and rapid determination of DBP from environmental waters.

AI in Measurement Science

Measurement of biological systems containing biomolecules and bioparticles is a key task in the fields of analytical chemistry, biology, and medicine. Driven by the complex nature of biological systems and unprecedented amounts of measurement data, artificial intelligence (AI) in measurement science has rapidly advanced from the use of silicon-based machine learning (ML) for data mining to the development of molecular computing with improved sensitivity and accuracy. This review presents an overview of fundamental ML methodologies and discusses their applications in disease diagnostics, biomarker discovery, and imaging analysis. We next provide the working principles of molecular computing using logic gates and arithmetical devices, which can be employed for in situ detection, computation, and signal transduction for biological systems. This review concludes by summarizing the strengths and limitations of AI-involved biological measurement in fundamental and applied research.