Chemi-Northern: a versatile chemiluminescent northern blot method for analysis and quantitation of RNA molecules.

This report describes a chemiluminescence-based detection method for RNAs on northern blots, designated Chemi-Northern. This approach builds on the simplicity and versatility of northern blotting, while dispensing of the need for expensive and cumbersome radioactivity. RNAs are first separated by denaturing gel electrophoresis, transferred to a nylon membrane, and then hybridized to a biotinylated RNA or DNA antisense probe. Streptavidin conjugated with horseradish peroxidase and enhanced chemiluminescence substrate are then used to detect the probe bound to the target RNA. Our results demonstrate the versatility of this method in detecting natural and engineered RNAs expressed in cells, including messenger and noncoding RNAs. We show that Chemi-Northern detection is sensitive and fast, detecting attomole amounts of RNA in as little as 1 sec, with high signal intensity and low background. The dynamic response displays excellent linearity. Using Chemi-Northern, we measure the reproducible, statistically significant reduction of mRNA levels by human sequence-specific RNA-binding proteins, PUM1 and PUM2. Additionally, we measure the interaction of the poly(A) binding protein, PABPC1, with polyadenylated mRNA. Thus, the Chemi-Northern method provides a versatile, simple, and cost-effective method to enable researchers to analyze expression, processing, binding, and decay of RNAs.

Deqformer: high-definition and scalable deep learning probe design method.

Target enrichment sequencing techniques are gaining widespread use in the field of genomics, prized for their economic efficiency and swift processing times. However, their success depends on the performance of probes and the evenness of sequencing depth among each probe. To accurately predict probe coverage depth, a model called Deqformer is proposed in this study. Deqformer utilizes the oligonucleotides sequence of each probe, drawing inspiration from Watson-Crick base pairing and incorporating two BERT encoders to capture the underlying information from the forward and reverse probe strands, respectively. The encoded data are combined with a feed-forward network to make precise predictions of sequencing depth. The performance of Deqformer is evaluated on four different datasets: SNP panel with 38 200 probes, lncRNA panel with 2000 probes, synthetic panel with 5899 probes and HD-Marker panel for Yesso scallop with 11 000 probes. The SNP and synthetic panels achieve impressive factor 3 of accuracy (F3acc) of 96.24% and 99.66% in 5-fold cross-validation. F3acc rates of over 87.33% and 72.56% are obtained when training on the SNP panel and evaluating performance on the lncRNA and HD-Marker datasets, respectively. Our analysis reveals that Deqformer effectively captures hybridization patterns, making it robust for accurate predictions in various scenarios. Deqformer leads to a novel perspective for probe design pipeline, aiming to enhance efficiency and effectiveness in probe design tasks.

Live-cell imaging of human apurinic/apyrimidinic endonuclease 1 in the nucleus and nucleolus using a chaperone@DNA probe.

Human apurinic/apyrimidinic endonuclease 1 (APE1) plays crucial roles in repairing DNA damage and regulating RNA in the nucleus. However, direct visualization of nuclear APE1 in live cells remains challenging. Here, we report a chaperone@DNA probe for live-cell imaging of APE1 in the nucleus and nucleolus in real time. The probe is based on an assembly of phenylboronic acid modified avidin and biotin-labeled DNA containing an abasic site (named PB-ACP), which cleverly protects DNA from being nonspecifically destroyed while enabling targeted delivery of the probe to the nucleus. The PB-ACP construct specifically detects APE1 due to the high binding affinity of APE1 for both avidin and the abasic site in DNA. It is easy to prepare, biocompatible and allowing for long-term observation of APE1 activity. This molecular tool offers a powerful means to investigate the behavior of APE1 in the nuclei of various types of live cells, particularly for the development of improved cancer therapies targeting this protein.

A sensitive and scalable fluorescence anisotropy single stranded RNA targeting approach for monitoring riboswitch conformational states.

The capacity of riboswitches to undergo conformational changes in response to binding their native ligands is closely tied to their functional roles and is an attractive target for antimicrobial drug design. Here, we established a probe-based fluorescence anisotropy assay to monitor riboswitch conformational switching with high sensitivity and throughput. Using the Bacillus subtillis yitJ S-Box (SAM-I), Fusobacterium nucleatum impX RFN element of (FMN) and class-I cyclic-di-GMP from Vibrio cholerae riboswitches as model systems, we developed short fluorescent DNA probes that specifically recognize either ligand-free or -bound riboswitch conformational states. We showed that increasing concentrations of native ligands cause measurable and reproducible changes in fluorescence anisotropy that correlate with riboswitch conformational changes observed by native gel analysis. Furthermore, we applied our assay to several ligand analogues and confirmed that it can discriminate between ligands that bind, triggering the native conformational change, from those that bind without causing the conformational change. This new platform opens the possibility of high-throughput screening compound libraries to identify potential new antibiotics that specifically target functional conformational changes in riboswitches.

Nanomechanoelectrical approach to highly sensitive and specific label-free DNA detection.

Electronic detection of DNA oligomers offers the promise of rapid, miniaturized DNA analysis across various biotechnological applications. However, known all-electrical methods, which solely rely on measuring electrical signals in transducers during probe-target DNA hybridization, are prone to nonspecific electrostatic and electrochemical interactions, subsequently limiting their specificity and detection limit. Here, we demonstrate a nanomechanoelectrical approach that delivers ultra-robust specificity and a 100-fold improvement in detection limit. We drive nanostructural DNA strands tethered to a graphene transistor to oscillate in an alternating electric field and show that the transistor-current spectra are characteristic and indicative of DNA hybridization. We find that the inherent difference in pliability between unpaired and paired DNA strands leads to the spectral characteristics with minimal influence from nonspecific electrostatic and electrochemical interactions, resulting in high selectivity and sensitivity. Our results highlight the potential of high-performance DNA analysis based on miniaturized all-electronic settings.

Nucleic acid hybridization-based detection of pathogenic RNA using microscale thermophoresis.

Infectious diseases are one of the world's leading causes of morbidity. Their rapid spread emphasizes the need for accurate and fast diagnostic methods for large-scale screening. Here, we describe a robust method for the detection of pathogens based on microscale thermophoresis (MST). The method involves the hybridization of a fluorescently labeled DNA probe to a target RNA and the assessment of thermophoretic migration of the resulting complex in solution within a 2 to 30-time window. We found that the thermophoretic migration of the nucleic acid-based probes is primarily determined by the fluorescent molecule used, rather than the nucleic acid sequence of the probe. Furthermore, a panel of uniformly labeled probes that bind to the same target RNA yields a more responsive detection pattern than a single probe, and moreover, can be used for the detection of specific pathogen variants. In addition, intercalating agents (ICA) can be used to alter migration directionality to improve detection sensitivity and resolving power by several orders of magnitude. We show that this approach can rapidly diagnose viral SARS-CoV2, influenza H1N1, artificial pathogen targets, and bacterial infections. Furthermore, it can be used for anti-microbial resistance testing within 2 h, demonstrating its diagnostic potential for early pathogen detection.

Single-molecule RNA in situ detection in clinical FFPE tissue sections by vsmCISH.

Although RNA plays a vital role in gene expression, it is less used as an in situ biomarker for clinical diagnostics than DNA and protein. This is mainly due to technical challenges caused by the low expression level and easy degradation of RNA molecules. To tackle this issue, methods that are sensitive and specific are needed. Here, we present an RNA single-molecule chromogenic in situ hybridization assay based on DNA probe proximity ligation and rolling circle amplification. When the DNA probes hybridize into close proximity to the RNA molecules, they form a V-shape structure and mediate the circularization of circle probes. Thus, our method was termed vsmCISH. We successfully applied our method to assess HER2 mRNA expression status in invasive breast cancer tissue and investigated the utility of albumin mRNA ISH for differentiating primary from metastatic liver cancer. The promising results on clinical samples indicate that our method has great potential for application in diagnosing diseases using RNA biomarkers.

Orientation-Guided Immobilization of Probe DNA on swCNT-FET for Enhancing Sensitivity of EcoRV Detection.

We present a novel approach that integrates electrical measurements with molecular dynamics (MD) simulations to assess the activity of type-II restriction endonucleases, specifically EcoRV. Our approach employs a single-walled carbon nanotube field-effect transistor (swCNT-FET) functionalized with the EcoRV substrate DNA, enabling the detection of enzymatic cleavage events. Notably, we leveraged the methylene blue (MB) tag as an "orientation guide" to immobilize the EcoRV substrate DNA in a specific direction, thereby enhancing the proximity of the DNA cleavage reaction to the swCNT surface and consequently improving the sensitivity in EcoRV detection. We conducted computational modeling to compare the conformations and electrostatic potential (ESP) of MB-tagged DNA with its MB-free counterpart, providing strong support for our electrical measurements. Both conformational and ESP simulations exhibited robust agreement with our experimental data. The inhibitory efficacy of the EcoRV inhibitor aurintricarboxylic acid (ATA) was also evaluated, and the selectivity of the sensing device was examined.

Plug-and-Play Module for Reversible and Continuous Control of DNA Strand Displacement Kinetics.

Regulatory modules for controlling the kinetics of toehold-mediated strand displacement (TMSD) play critical roles in designing dynamic and dissipative DNA chemical reaction networks (CRNs) but are hardwired into sequence designs. Herein, we introduce antitoehold (At), a plug-and-play module for reversible and continuous tuning of TMSD kinetics by temporarily occupying the toehold domain via a metastable duplex and base stacking. We demonstrate that kinetic control can be readily activated or deactivated in real time for any TMSD by simply adding At or anti-At. Continuous tuning of TMSD kinetics can also be achieved by altering the concentration of At. Moreover, the simple addition of At could readily reprogram existing TMSDs into a pulse-generation DNA CRN with continuous tunability. Our At approach also offers a new way for engineering continuously tunable DNA hybridization probes, which may find practical uses for discriminating clinically important mutations. Because of the simplicity, we anticipate that At will find wide applications for engineering DNA CRNs with diverse dynamic and dissipative behaviors, and DNA hybridization probes with tunable affinity and selectivity.

Microfluidic Immunosensing Platform Based on a Rolling Circle Amplification-Assisted DNA Dendrimer Probe for Portable and Sensitive Detection of Allergen-Specific IgE.

The robust point-of-care platform for sensitive, multiplexed, and affordable detection of allergen-specific IgE (sIgE) is an urgent demand in component-resolved diagnostics. Here, we developed a microfluidic immunosensing platform based on a rolling circle amplification-assisted DNA dendrimer probe for sensitive detection of multiple sIgEs. The versatile multichannel microfluidic whole blood analytical device integrates cell filtration, recombinant antigen-modified magnetic enrichment, and DNA dendrimer probe-amplified signal transduction for portable on-chip analysis. Three sIgEs against common oyster allergens were simultaneously detected in blood samples by simple smartphone-based imaging without any pretreatment. The quantitative detection of multiple allergen-specific antibodies on the platform was achieved with limits of detection of less than 50 pg/mL, exhibiting superior sensitivity compared to most point-of-care testing. The detection results of 55 serum samples and 4 whole blood samples were 100% consistent with the ELISA results, confirming the accuracy and stability of our platform. Additionally, the reversible combination of hexahistidine6-tag and Ni-IMAC magbead was elegantly utilized on the immunosensing platform for desired reversibility. With the advantages of general applicability, high sensitivity, and reversibility, the DNA dendrimer-based microfluidic immunosensing platform provides great potential for the portable detection of immune proteins as a point-of-care platform in disease diagnostics and biological analysis.

Ultrasensitive Point-of-Care Detection of Protein Markers Using an Aptamer-CRISPR/Cas12a-Regulated Liquid Crystal Sensor (ALICS).

Despite extensive efforts, point-of-care testing (POCT) of protein markers with high sensitivity and specificity and at a low cost remains challenging. In this work, we developed an aptamer-CRISPR/Cas12a-regulated liquid crystal sensor (ALICS), which achieved ultrasensitive protein detection using a smartphone-coupled portable device. Specifically, a DNA probe that contained an aptamer sequence for the protein target and an activation sequence for the Cas12a-crRNA complex was prefixed on a substrate and was released in the presence of target. The activation sequence of the DNA probe then bound to the Cas12a-crRNA complex to activate the collateral cleavage reaction, producing a bright-to-dark optical change in a DNA-functionalized liquid crystal interface. The optical image was captured by a smartphone for quantification of the target concentration. For the two model proteins, SARS-CoV-2 nucleocapsid protein (N protein) and carcino-embryonic antigen (CEA), ALICS achieved detection limits of 0.4 and 20 pg/mL, respectively, which are higher than the typical sensitivity of the SARS-CoV-2 test and the clinical CEA test. In the clinical sample tests, ALICS also exhibited superior performances compared to those of the commercial ELISA and lateral flow test kits. Overall, ALICS represents an ultrasensitive and cost-effective platform for POCT, showing a great potential for pathogen detection and disease monitoring under resource-limited conditions.

Zipper-Confined DNA Nanoframe for High-Efficient and High-Contrast Imaging of Heterogeneous Tumor Cell.

Current study in the heterogeneity and physiological behavior of tumor cells is limited by the fluorescence in situ hybridization technology in terms of probe assembly efficiency, background suppression capability, and target compatibility. In a typically well-designed assay, hybridization probes are constructed in a confined nanostructure to achieve a rapid assembly for efficient signal response, while the excessively high local concentration between different probes inevitably leads to nonspecific background leakage. Inspired by the fabric zipper, we propose a novel confinement reaction pattern in a zipper-confined DNA nanoframe (ZCDN), where two kinds of hairpin probes are independently anchored respective tracks. The metastable states of the dual tracks can well avoid signal leakage caused by the nonspecific probe configuration change. Biomarker-mediated proximity ligation reduces the local distance of dual tracks, kinetically triggering an efficient allosteric chain reaction between the hairpin probes. This method circumvents nonspecific background leakage while maintaining a high efficiency in responding to targets. ZCDN is employed to track different cancer biomarkers located in both the cytoplasm and cytomembrane, of which the expression level and oligomerization behavior can provide crucial information regarding intratumoral heterogeneity. ZCDN exhibits high target response efficiency and strong background suppression capabilities and is compatible with various types of biological targets, thus providing a desirable tool for advanced molecular diagnostics.

DNA Polymerase-Steered Self-Propelled and Self-Enhanced DNA Walker for Rapid and Distinctly Amplified Electrochemical Sensing.

The development of a simple, rapid, easy-to-operate, and ultrasensitive DNA walker-based sensing system is challenging but would be very intriguing for the enormous applications in biological analysis and disease monitoring. Herein, a new self-propelled and self-enhanced DNA walking strategy was developed on the basis of a simple DNA polymerase-steered conversion from a typical alternate DNA assembly process. The sensing platform was fabricated easily by immobilizing only one hairpin probe (H1) and the sensing process was based on a simple one-step mixing with another hairpin-like DNA probe (H2) and DNA polymerase. The DNA polymerization could achieve target recycling and successive DNA walking steps. Interestingly, along with each DNA walking step, the new DNA walker sequence could be autonomously accumulated for a self-enhanced DNA walking effect. This provided a multilevel signal amplification ability for the ultrasensitive detection of the target with a low detection limit of 0.18 fM. Moreover, it could greatly reduce the reaction time with the sensing process finished within 1 h. The detection selectivity and the applicative potential in a complicated biological matrix were also demonstrated. Furthermore, the flexible control of sensing modes (self-enhanced DNA walking or the alternate DNA assembly) by using DNA polymerase or not offered a powerful means for sensing performance modulation. It thus opens a new avenue toward the development of a DNA walker-based sensing platform with both rapid and ultrasensitive features and might hold a huge potential for point-of-care diagnostic applications.

Lanthanide-Complex-Enhanced Bioorthogonal Branched DNA Amplification.

Fluorescence in situ hybridization (FISH) is a widely used technique for detecting intracellular nucleic acids. However, its effectiveness in detecting low-copy nucleic acids is limited due to its low fluorescence intensity and background autofluorescence. To address these challenges, we present here an approach of lanthanide-complex-enhanced bioorthogonal-branched DNA amplification (LEBODA) with high sensitivity for in situ nuclear acid detection in single cells. The approach capitalizes on two levels of signal amplification. First, it utilizes click chemistry to directly link a substantial number of bridge probes to target-recognizing probes, providing an initial boost in signal intensity. Second, it incorporates high-density lanthanide complexes into each bridge probe, enabling secondary amplifications. Compared to the traditional "double Z" probes used in the RNAscope method, LEBODA exhibits 4 times the single enhancement for RNA detection signal with the click chemistry approach. Using SARS-CoV-2 pseudovirus-infected HeLa cells, we demonstrate the superiority in the detection of viral-infected cells in rare populations as low as 20% infectious rate. More encouragingly, the LEBODA approach can be adapted for DNA-FISH and single-molecule RNA-FISH, as well as other hybridization-based signal amplification methods. This adaptability broadens the potential applications of LEBODA in the sensitive detection of biomolecules, indicating promising prospects for future research and practical use.

Endogenous Enzyme-Driven Amplified DNA Nanocage Probe for Selective and Sensitive Imaging of Mature MicroRNAs in Living Cancer Cells.

Selective and sensitive imaging of intracellular mature microRNAs (miRNAs) is of great importance for biological process study and medical diagnostics. However, this goal remains challenging because of the interference of precursor miRNAs (pre-miRNAs) and the low abundance of mature miRNAs. Herein, we develop an endogenous enzyme-driven amplified DNA nanocage probe (Acage) for the selective and sensitive imaging of mature miRNAs in living cells. The Acage consists of a microRNA-responsive probe, an endogenous enzyme-driven fuel strand, and a DNA nanocage framework with an inner cavity. Benefiting from the size selectivity of DNA nanocage, smaller mature miRNAs rather than larger pre-miRNAs are allowed to enter the cavity of DNA nanocage for molecular recognition; thus, Acage can significantly reduce the signal interference of pre-miRNAs. Moreover, with the driving force of an endogenous enzyme apurinic/apyrimidinic endonuclease 1 (APE1) for efficient signal amplification, Acage enables sensitive intracellular miRNA imaging without an additional external intervention. With these features, Acage was successfully applied for intracellular imaging of mature miRNAs during drug treatment. We believe that this strategy provides a promising pathway for better understanding the functions of mature microRNAs in biological processes and medical diagnostics.

Spherical Nucleic Acid-Mediated Spatial Matching-Guided Nonenzymatic DNA Circuits for the Prediction and Prevention of Malignant Tumor Invasion.

Detection of intracellular miRNAs, especially sensitive imaging of in vivo miRNAs, is vital to the precise prediction and timely prevention of tumorgenesis but remains a technical challenge in terms of nuclease resistance and signal amplification. Here, we demonstrate a gold nanoparticle-based spherical nucleic acid-mediated spatial matching-guided nonenzymatic DNA circuit (SSDC) for efficient screening of intracellular miRNAs and, in turn, finding cancerous tissues in living organisms before the appearance of clinical symptoms. Due to the substantially enhanced nuclease resistance, the false positive signal is avoided even in a complex biological medium. Target miRNA can straighten out the hairpin DNA probe to be linear, allowing the probe to penetrate into the internal region of a core/shell DNA-functionalized signal nanoampfilier and initiate a strand displacement reaction, generating an amplified fluorescence signal. The detection limit is as low as 17 pM, and miRNA imaging is in good accordance with the gold standard polymerase chain reaction method. The ability to image intracellular miRNAs is substantially superior to that of conventional fluorescence in situ hybridization techniques, making in vivo SSDC-based imaging competent for the precise prediction of tumorigenesis. By intratumoral chemotherapy guided by SSDC-based imaging, tumorigenesis and progression are efficiently controlled before the onset of clinical symptoms.

A New SPQC Biosensor for the Detection of a New Target of Escherichia/Shigella Genera Based on a Novel Method of Synthesizing Long-Range DNA.

The rapid and sensitive detection of Escherichia/Shigella genera is crucial for human disease and health. This study introduces a novel series of piezoelectric quartz crystal (SPQC) sensors for detecting Escherichia/Shigella genera. In this innovative biosensor, we propose a new target and novel method for synthesizing long-range DNA. The method relies on the amplification of two DNA probes, referred to as H and P amplification (HPA), resulting in the products of long-range DNA named Sn. The new target was screened from the 16S rRNA gene and utilized as a biomarker. The SPQC sensor operates as follows: the Capture probe is modified on the electrodes. In the presence of a Displace probe and target, the Capture can form a complex with the Displace probe. The resulting complex hybridizes with Sn, bridging the gap between the electrodes. Finally, silver wires are deposited between the electrodes using Sn as a template. This process results in a sensitive response from the SPQC. The detection limit of the SPQC sensor is 1 CFU/mL, and the detection time is within 2 h. This sensor would be of great benefit for food safety monitoring and clinical diagnosis.

DNA Nanospheres Assisted Spatial Confinement Signal Amplification for MicroRNA Imaging in Live Cancer Cells.

DNA assemblies are commonly used in biosensing, particularly for the detection and imaging of microRNAs (miRNAs), which are biomarkers associated with tumor progression. However, the difficulty lies in the exploration of high-sensitivity analytical techniques for miRNA due to its limited presence in living cells. In this study, we introduced a DNA nanosphere (DS) enhanced catalytic hairpin assembly (CHA) system for the detection and imaging of intracellular miR-21. The single-stranded DNA with four palindromic portions and extending sequences at the terminal was annealed for assembling DS, which avoided the complex sequence design and high cost of long DNA strands. Benefiting from the multiple modification sites of DS, functional hairpins H1 (modified with Cy3 and BHQ2) and H2 were grafted onto the surface of DS for assembling DS-H1-H2 using a hybridization reaction. The DS-H1-H2 system utilized spatial confinement and the CHA reaction to amplify fluorescence signals of Cy3. This enabled highly sensitive and rapid detection of miR-21 in the range from 0.05 to 3.5 nM. The system achieved a limit of determination (LOD) of 2.0 pM, which was 56 times lower than that of the control CHA circuit with freedom hairpins. Additionally, the sensitivity was improved by 8 times. Moreover, DS-H1-H2 also showed an excellent imaging capability for endogenous miR-21 in tumor cells. This was due to enhanced cell internalization efficiency, accelerated reaction kinetics, and improved biostability. The imaging strategy was shown to effectively monitor the dynamic content of miR-21 in live cancer cells and differentiate various cells. In general, the simple nanostructure DS not only enhanced the detection and imaging capability of the conventional probe but also could be easily integrated with the reported DNA-free probe, indicating a wide range of potential applications.

Plasmonic Gold Nanostar-Based Probes with Distance-Dependent Plasmon-Enhanced Fluorescence for Ultrasensitive DNA Methyltransferase Assay.

The ultrasensitive DNA methyltransferase (Dam MTase) assay is of high significance for biomedical research and clinical diagnosis because of its profound effect on gene regulation. However, detection sensitivity is still limited by shortcomings, including photobleaching and weak signal intensities of conventional fluorophores at low concentrations. Plasmonic nanostructures with ultrastrong electromagnetic fields and fluorescence enhancement capability that can overcome these intrinsic defects hold great potential for ultrasensitive bioanalysis. Herein, a silica-coated gold nanostars (Au NSTs@SiO2)-based plasmon-enhanced fluorescence (PEF) probe with 20 "hot spots" was developed for ultrasensitive detection of Dam MTase. Here, the Dam Mtase assay was achieved by detecting the byproduct PPi of the rolling circle amplification reaction. It is worth noting that, benefiting from the excellent fluorescence enhancement capability of Au NSTs originating from their 20 "hot spots", the detection limit of Dam Mtase was reduced by nearly 105 times. Moreover, the proposed Au NST-based PEF probe enabled versatile evaluation of Dam MTase inhibitors as well as endogenous Dam MTase detection in GW5100 and JM110 Escherichia coli cell lysates, demonstrating its potential in biomedical analysis.

Triblock PolyA-Mediated Protein Biosensor Based on a Size-Matching Proximity Hybridization Analysis.

The antibodies in the natural biological world utilize bivalency/multivalency to achieve a higher affinity for antigen capture. However, mimicking this mechanism on the electrochemical sensing interface and enhancing biological affinity through precise spatial arrangement of bivalent aptamer probes still pose a challenge. In this study, we have developed a novel self-assembly layer (SAM) incorporating triblock polyA DNA to enable accurate organization of the aptamer probes on the interface, constructing a "lock-and-key-like" proximity hybridization assay (PHA) biosensor. The polyA fragment acts as an anchoring block with a strong affinity for the gold surface. Importantly, it connects the two DNA probes, facilitating one-to-one spatial proximity and enabling a controllable surface arrangement. By precisely adjusting the length of the polyA fragment, we can tailor the distance between the probes to match the molecular dimensions of the target protein. This design effectively enhances the affinity of the aptamers. Notably, our biosensor demonstrates exceptional specificity and sensitivity in detecting PDGF-BB, as confirmed through successful validation using human serum samples. Overall, our biosensor presents a novel and versatile interface for proximity assays, offering a significantly improved surface arrangement and detection performance.