In Situ Visualization of RNA-Specific Sialylation on Living Cell Membranes to Explore N-Glycosylation Sites.

The small RNAs on living cell membranes were recently found to be N-glycosylated and terminated with sialic acids, although the glycosylation sites and potential functions remain unclear. Herein, we designed a second-generation hierarchical coding strategy (HieCo 2) for in situ visualization of cell surface RNA-specific sialylation. After covalently binding DNA codes to sialic acids and then binding a DNA code to a target RNA via sequence specificity, cascade decoding processes were performed with subsequent signal amplification that enabled sensitive in situ visualization of low-abundance Y5 RNA-specific sialic acids on living cell membranes. The proposed strategy unveils the number of glycosylation sites on a single RNA and reveals the binding preference of glycosylated RNAs to different sialic acid binding-immunoglobulin lectin-type receptors, demonstrating a new route for exploration of the glycosylated RNA-related biological and pathological processes.

Reticular Ratchets for Directing Electrochemiluminescence.

Electrochemiluminescence (ECL) involves charge transfer between electrochemical redox intermediates to produce an excited state for light emission. Ensuring precise control of charge transfer is essential for decoding ECL fundamentals, yet guidelines on how to achieve this for conventional emitters remain unexplored. Molecular ratchets offer a potential solution, as they enable the directional transfer of energy or chemicals while impeding the reverse movement. Herein, we designed 10 pairs of imine-based covalent organic frameworks as reticular ratchets to delicately manipulate the intrareticular charge transfer for directing ECL transduction from electric and chemical energies. Aligning the donor and acceptor (D-A) directions with the imine dipole effectively facilitates charge migration, whereas reversing the D-A direction impedes it. Notably, the ratchet effect of charge transfer directionality intensified with increasing D-A contrast, resulting in a remarkable 680-fold improvement in the ECL efficiency. Furthermore, dipole-controlled exciton binding energy, electron/hole decay kinetics, and femtosecond transient absorption spectra identified the electron transfer tendency from the N-end toward the C-end of reticular ratchets during ECL transduction. An exponential correlation between the ECL efficiency and the dipole difference was discovered. Our work provides a general approach to manipulate charge transfer and design next-generation electrochemical devices.

Coupled Poly(ethylenimine) Coreactant to Enhance Electrochemiluminescence of Polymer Dots for Array Imaging of Protein Biomarkers.

Traditional electrochemiluminescent (ECL) bioanalysis suffers from the demand for excessive external coreactants and the damage of reaction intermediates. In this work, a poly(ethylenimine) (PEI)-coupled ECL emitter was proposed by covalently coupling tertiary amine-rich PEI to polymer dots (Pdots). The coupled PEI might act as a highly efficient coreactant to enhance the ECL emission of Pdots through intramolecular electron transfer, reducing the electron transfer distance between emitter and coreactant intermediates and avoiding the disadvantages of traditional ECL systems. Through modification of the PEI-Pdots with tDNA, a sequence partially complementary to cDNA that was complementary to the aptamer of target protein biomarker (aDNA), tDNA-PEI-Pdots were obtained. The biosensors were produced using Au/indium tin oxide (ITO) with an aDNA/cDNA hybrid, and an ECL imaging biosensor array was constructed for ultrasensitive detection of protein biomarkers. Using vascular endothelial growth factor 165 (VEGF165) as a protein model, the proposed ECL imaging method containing two simple incubations with target samples and then tDNA-PEI-Pdots showed a detectable range of 1 pg mL-1 to 100 ng mL-1 and a detection limit of 0.71 pg mL-1, as well as excellent performance such as low toxicity, high sensitivity, excellent selectivity, good accuracy, and acceptable fabrication reproducibility. The PEI-coupled Pdots provide a new avenue for the design of ECL emitters and the application of ECL imaging in disease biomarker detection.

Highly Electroactive Co2+-Based Metal-Organic Frameworks as an Efficient Coreaction Accelerator for Amplifying Near-Infrared Electrochemiluminescence of Gold Nanoclusters in Biomarkers Immunoassay.

Metal nanoclusters (NCs) as a new kind of luminophore have acquired sufficient interest, but their widespread application is restricted on account of their relatively low electrochemiluminescence (ECL) efficiency. Then, aqueous metal NCs with high ECL efficiency were strongly anticipated, especially for the ultrasensitive analysis of biomarkers. Herein, a near-infrared (NIR) ECL biosensing strategy for the test of neuron-specific enolase (NSE) was proposed by utilizing N-acetyl-l-cysteine (NAC)- and cysteamine (Cys)-stabilized gold NCs (NAC/Cys-AuNCs) as ECL emitters with the NIR ECL emission around 860 nm and a metal-organic framework/palladium nanocubes (ZIF-67/PdNCs) hybrid as the coreaction accelerator through their admirable electrocatalytic activity. The NIR emission would reduce photochemical injury to the samples and even realize nondestructive analysis with highly strong susceptibility and suitability. Furthermore, the utilization of ZIF-67/PdNCs could improve the ECL response of NAC/Cys-AuNCs by facilitating the oxidation of the coreactant triethylamine (TEA), leading to the production of a larger quantity of reducing intermediate radical TEA•+. Consequently, NAC/Cys-AuNCs with ZIF-67/PdNCs displayed 2.7 fold enhanced ECL emission compared with the single NAC/Cys-AuNCs using TEA as the coreactant. In addition, HWRGWVC (HWR), a heptapeptide, was introduced to immobilize antibodies for the specially binding Fc fragment of the antibodies, which improved the binding efficiency and sensitivity. As a result, a "signal-on" immunosensor for NSE analysis was obtained with an extensive linear range of 0.1 to 5 ng/mL and a low limit of detection (0.033 fg/mL) (S/N = 3). This study provides a wonderful method for the development of an efficient nondestructive immunoassay.

Self-Assembly-Induced Enhancement of Cathodic Electrochemiluminescence of Copper Nanoclusters for a Split-Type Matrix Metalloproteinase 14 Sensing Platform.

The unique optoelectronic and tunable luminescent characteristics of copper nanoclusters (Cu NCs) make them extremely promising as luminophores. However, the limited luminescence intensity and stability of Cu NCs have restricted their application in the field of electrochemiluminescence (ECL). Herein, a self-assembly-induced enhancement strategy was successfully employed to enhance the cathodic ECL performance of flexible ligand-stabilized Cu NCs. Specifically, Cu NCs form ordered sheetlike structures through intermolecular force. The restriction of ligand torsion in this self-assembled structure leads to a significant improvement in the ECL properties of the Cu NCs. Experimental results demonstrate that the assembled nanoscale Cu NC sheets exhibit an approximately three-fold increase in cathodic ECL emission compared to the dispersed state of Cu NCs. Furthermore, assembled nanoscale Cu NCs sheets were utilized as signal probes in conjunction with a specific short peptide derived from the catalytic structural domain of matrix metalloproteinase 14 (MMP 14) as the identification probe, thereby establishing a split-type ECL sensing platform for the quantification of NMP 14. The investigation has revealed the exceptional performance of assembled nanoscale Cu NCs sheets in ECL analysis, thus positioning them as novel and promising signal probes with significant potential in the field of sensing.

Ligation-Based High-Performance Mimetic Enzyme Sensing Platform for Nucleic Acid Detection.

G-quadruplex (G4)/hemin DNAzyme is a promising candidate to substitute horseradish peroxidase in biosensing systems, especially for the detection of nucleic acids. However, the relatively suboptimal catalytic capacity limits its potential applications. This makes it imperative to develop an ideal signal for the construction of highly sensitive biosensing platforms. Herein, we integrated a novel chimeric peptide-DNAzyme (CPDzyme) with the ligase chain reaction (LCR) for the cost-efficient and highly sensitive detection of nucleic acids. By employing microRNA (miRNA) and single-nucleotide polymorphism detection as the model, we designed a G4-forming sequence on the LCR probe with a terminally labeled amino group. Subsequently, asymmetric hemin with carboxylic arms allowed assembly with the LCR products and peptide to form CPDzyme, followed by the magnetic separation of the extraneous components and chemiluminescence detection. Compared with the conventional G4/hemin signaling-based method, the LCR-CPDzyme system demonstrated 3 orders of magnitude improved sensitivity, with accurate quantification of as low as 25 aM miRNA and differentiation of 0.1% of mutant DNA from the pool containing a large amount of wild-type DNA. The proposed LCR-CPDzyme strategy is a potentially powerful method for in vitro diagnostics and serves as a reference for the development of other ligation- or hybridization-based nucleic acid amplification assays.

Bioinspired Dual Hemin-Bonded G-Quadruplex and Histidine-Functionalized Metal-Organic Framework for Sensitive Biosensing.

Biomimetic enzymes have emerged as ideal alternatives to natural enzymes, and there is considerable interest in designing biomimetic enzymes with enhanced catalytic performance to address the low activity of the current biomimetic enzymes. In this study, we proposed a meaningful strategy for constructing an efficient peroxidase-mimicking catalyst, called HhG-MOF, by anchoring histidine (H) and dual hemin-G-quadruplex DNAzyme (double hemin covalently linked to 3' and 5' terminals of G-quadruplex DNA, short as hG) to a mesoporous metal-organic framework (MOF). This design aims to mimic the microenvironment of natural peroxidase. Remarkably, taking a terbium MOF as a typical model, the initial rate of the resulting catalyst was found to be 21.1 and 4.3 times higher than that of Hh-MOF and hG-MOF, respectively. The exceptional catalytic properties of HhG-MOF can be attributed to its strong affinity for substrates. Based on the inhibitory effect of thiocholine (TCh) produced by the reaction between acetylcholinesterase (AChE) and acetylthiocholine, a facile, cost-effective, and sensitive colorimetric method was designed based on HhG-MOF for the measurement of AChE, a marker of several neurological diseases, and its inhibitor. This allowed a linear response in the 0.002 to 1 U L-1 range, with a detection limit of 0.001 U L-1. Furthermore, the prepared sensor demonstrated great selectivity and performed well in real blood samples, suggesting that it holds promise for applications in the clinical field.

Multifunctional Supramolecular Hydrogel Modulated Heterojunction Interface Carrier Transport Engineering Facilitates Sensitive Photoelectrochemical Immunosensing.

Highly responsive interface of semiconductor nanophotoelectrochemical materials provides a broad development prospect for the identification of low-abundance cancer marker molecules. This work innovatively proposes an efficient blank WO3/SnIn4S8 heterojunction interface formed by self-assembly on the working electrode for interface regulation and photoregulation. Different from the traditional biomolecular layered interface, a hydrogel layer containing manganese dioxide with a wide light absorption range is formed at the interface after an accurate response to external immune recognition. The formation of the hydrogel layer hinders the effective contact between the heterojunction interface and the electrolyte solution, and manganese dioxide in the hydrogel layer forms a strong competition between the light source and the substrate photoelectric material. The process effectively improves the carrier recombination efficiency at the interface, reduces the interface reaction kinetics and photoelectric conversion efficiency, and thus provides strong support for target identification. Taking advantage of the process, the resulting biosensors are being explored for sensitive detection of human epidermal growth factor receptor 2, with a limit of detection as low as 0.037 pg/mL. Also, this study contributes to the advancement of photoelectrochemical biosensing technology and opens up new avenues for the development of sensitive and accurate analytical tools in the field of bioanalysis.

Arginine-Modified Hemin Enhances G-Quadruplex DNAzyme Peroxidase Activity for High Sensitivity Detection.

Hemin/G-quadruplex (hG4) complexes are frequently used as artificial peroxidase-like enzymatic systems (termed G4 DNAzymes) in many biosensing applications, in spite of a rather low efficiency, notably in terms of detection limits. To tackle this issue, we report herein a strategy in which hemin is chemically modified with the amino acids found in the active site of parent horseradish peroxidase (HRP), with the aim of recreating an environment conducive to high catalytic activity. When hemin is conjugated with a single arginine, it associates with G4 to create an arginine-hemin/G4 (R-hG4) DNAzyme that exhibits improved catalytic performances, characterized by kinetic analysis and DFT calculations. The practical relevance of this system was demonstrated with the implementation of biosensing assays enabling the chemiluminescent detection of G4-containing DNA and colorimetry detection of the flap endonuclease 1 (FEN1) enzyme with a high efficiency and sensitivity. Our results thus provide a guide for future enzyme engineering campaigns to create ever more efficient peroxidase-mimicking DNA-based systems.

Photocleavable DNA Nanotube-Based Dual-Amplified Resonance Rayleigh Scattering System for MicroRNA Detection Incorporating Molecular Computing-Cascaded Keypad Lock Functionality.

Cascade molecular events in complex systems are of vital importance for enhancing molecular diagnosis and information processing. However, the conversion of a cascaded biosensing system into a multilayer encrypted molecular keypad lock remains a significant challenge in the development of molecular logic devices. In this study, we present a photocleavable DNA nanotube-based dual-amplified resonance Rayleigh scattering (RRS) system for detecting microRNA-126 (miR-126). The cascading dual-amplification biosensing system provides a multilayer-encrypted prototype with the functionality of a molecular computing cascade keypad lock. RRS signals were greatly amplified by using photocleavable DNA nanotubes and enzyme-assisted strand displacement amplification (SDA). In the presence of miR-126, enzyme-assisted SDA produced numerous identical nucleotide fragments as the target, which were then specifically attached to magnetic beads through the DNA nanotube by using a Y-shaped DNA scaffold. Upon ultraviolet irradiation, the DNA nanotube was released into the solution, resulting in an increase in the intensity of the RRS signal. This strategy demonstrated a low limit of detection (0.16 fM) and a wide dynamic range (1 fM to 1 nM) for miR-126. Impressively, the enzyme-assisted SDA offers a molecular computing model for generating the target pool, which serves as the input element for unlocking the system. By cascading the molecular computing process, we successfully constructed a molecular keypad lock with a multilevel authentication technique. The proposed system holds great potential for applications in molecular diagnosis and information security, indicating significant value in integrating molecular circuits for intelligent sensing.

Z-Scheme Heterojunction of Hierarchical Cu2S/CdIn2S4 Hollow Cubes to Boost Photoelectrochemical Performance.

The exaltation of light-harvesting efficiency and the inhibition of fast charge recombination are pivotal to the improvement of photoelectrochemical (PEC) performance. Herein, a direct Z-scheme heterojunction is designed of Cu2S/CdIn2S4 by in situ growth of CdIn2S4 nanosheets on the surface of hollow CuS cubes and then annealing at 400 °C. The constructed Z-scheme heterojunction is demonstrated with electron paramagnetic resonance and redox couple (p-nitrophenol/p-aminophenol) measurements. Under illumination, it shows the photocurrent 6 times larger than that of hollow Cu2S cubes, and affords outstanding PEC performance over the known Cu2S and CdIn2S4-based photocatalysts. X-ray photoelectron spectroscopy and density functional theory results demonstrate a strong internal electric field formed in Cu2S/CdIn2S4 Z-scheme heterojunction, which accelerates the Z-scheme charge migration, thereby promoting electron-hole separation and enhancing their utilization efficiency. Moreover, the hollow structure of Cu2S is conducive to shortening the charge transport distance and improving light-harvesting capability. In proof-of-concept PEC application, a PEC detection method for miRNA-141 based on the sensitivity of benzo-4-chloro-hexadienone to light absorption on Cu2S/CdIn2S4 modified electrode is developed with good selectivity and a limit of detection of 32 aM. This work provides a simple approach for designing photoactive materials with highly efficient PEC performance.

Securing LYTAC with Logic-Identification System for Cancer Cell-Selective Membrane Protein Degradation.

Lysosome-targeting chimera (LYTAC) links proteins of interest (POIs) with lysosome-targeting receptors (LTRs) to achieve membrane protein degradation, which is becoming a promising therapeutic modality. However, cancer cell-selective membrane protein degradation remains a big challenge considering expressions of POIs in both cancer cells and normal cells, as well as broad tissue distribution of LTRs. Here a logic-identification system is designed, termed Logic-TAC, based on cell membrane-guided DNA calculations to secure LYTAC selectively for cancer cells. Logic-TAC is designed as a duplex DNA structure, with both POI and LTR recognition regions sealed to avoid systematic toxicity during administration. MCF-7 and MCF-10A are chosen as sample cancer cell and normal cell respectively. As input 1 for logic-identification, membrane proteins EpCAM, which is highly expressed by MCF-7 but barely by MCF-10A, reacts with Logic-TAC to expose POI recognition region. As input 2 for logic-identification, Logic-TAC binds to POI, membrane protein MUC1, to expose LTR recognition region. As output, MUC1 is connected to LTR and degraded via lysosome pathway selectively for cancer cell MCF-7 with little side effect on normal cell MCF-10A. The logic-identification system also demonstrated satisfactory in vivo therapeutic results, indicating its promising potential in precise targeted therapy.

NIR-II Orthogonal Fluorescent Ratiometric Nanoprobe for In Situ Bioimaging of Carbon Monoxide.

Carbon monoxide (CO) functions as a significant endogenous cell signaling molecule and is strongly associated with many physiological and pathological processes. However, conventional fluorescence imaging in the visible and near-infrared (NIR) I regions suffers autofluorescence background and photon scattering, hindering the accurate detection of CO in vivo. In addition, the complexity of physiological environments leads to fluctuating fluorescence emission. To solve these problems, herein, the NIR-II fluorescent nanoprobe NP-Pd for in vivo ratiometric bioimaging of CO is developed. In the presence of CO, NP-Pd exhibits responsive enhancement in absorption at 808 nm, which amplifies the fluorescence signal of down-conversion nanoparticles (DCNP) at 1060 nm under 808 nm excitation, while the fluorescence signal of DCNP at 1525 nm under 980 nm excitation remains unchanged and serves as an internal standard. Through this orthogonally ratiometric fluorescence strategy, accurate CO bioimaging and precise diagnosis of acute liver injury diseases are achieved in the mouse model experiments, providing a novel tool for the in vivo detection of CO-related diseases.

Reticular Electrochemiluminescence Nanoemitters: Structural Design and Enhancement Mechanism.

ConspectusElectrochemiluminescence (ECL) is a powerful transduction technique, which depends critically on the formation of the excited emitter through the charge transfer between the electrochemical reaction intermediates of the emitter and the co-reactant/emitter. The exploration of ECL mechanisms for conventional nanoemitters is limited due to the uncontrollable charge transfer process. With the development of molecular nanocrystals, reticular structures such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have been utilized as atomically precise semiconducting materials. The long-range order in crystalline frameworks and the tunable coupling among building blocks promote the quick development of electrically conductive frameworks. Especially, the reticular charge transfer can be regulated by both interlayer electron coupling and intralayer topology-templated conjugation. By modulating intramolecular or intermolecular charge mobility, reticular structures could serve as promising candidates for enhancing ECL. Thus, reticular crystalline nanoemitters with different topologies provide a confined platform to understand ECL fundamentals for designing next-generation ECL devices.Aiming at exploring the mechanism of ECL emission, our group has developed a series of ECL nanoemitters as well as enhancement strategies of ECL emission in the past 20 years. A series of water-soluble ligand-capped quantum dots were introduced as ECL nanoemitters to create sensitive analytical methods for detecting and tracing biomarkers. The functionalized polymer dots were also designed as ECL nanoemitters for imaging of membrane proteins with signal transduction strategies of dual resonance energy transfer and dual intramolecular electron transfer. To decode the ECL fundamental and enhancement mechanisms, an electroactive MOF with accurate molecular structure was first constructed with two redox ligands as a highly crystallized ECL nanoemitter in aqueous medium. Through the mixed-ligand approach, luminophores and co-reactants were integrated into one MOF structure for self-enhanced ECL. Furthermore, several donor-acceptor COFs were developed as efficient ECL nanoemitters with tunable intrareticular charge transfer. The atomically precise structure of conductive frameworks established clear correlations between the structure and charge transport in these materials. Therefore, reticular materials as crystalline ECL nanoemitters have demonstrated both proof of concept and mechanistic innovation.In this Account, taking advantage of reticular materials with accurate molecular structure, we survey the design of the electroactive reticular materials including MOFs and COFs as crystalline ECL nanoemitters at the molecular level. The enhancement mechanisms of ECL emission of various topology frameworks are discussed via the regulation of reticular energy transfer and charge transfer and the accumulation of anion/cation radicals. Our perspective on the reticular ECL nanoemitters is also discussed. This Account provides a new avenue for designing molecular crystalline ECL nanoemitters and decoding the fundamentals of ECL detection methods.

Recent Advances in DNA-Based Nanoprobes for In vivo MiRNA Imaging.

As a post transcriptional regulator of gene expression, miRNA is closely related to many major human diseases, especially cancer. Therefore, its precise detection is very important for disease diagnosis and treatment. With the advancement of fluorescent dye and imaging technology, the focus has shifted from in vitro microRNAs (miRNA) detection to in vivo miRNA imaging. This concept review summarizes signal amplification strategies including DNAzyme catalytic reaction, hybrid chain reaction (HCR), catalytic hairpin assembly (CHA) to enhance detection signal of lowly expressed miRNAs; external stimuli of ultraviolet (UV) light or near-infrared region (NIR) light, and internal stimuli such as adenosine triphosphate (ATP), glutathione (GSH), protease and cell membrane protein to prevent nonspecific activation for the avoidance of false positive signal; and the development of fluorescent probes with emission in NIR for in vivo miRNA imaging; as well as rare earth nanoparticle based the second near-infrared window (NIR-II) nanoprobes with excellent tissue penetration and depth for in vivo miRNA imaging. The concept review also indicated current challenges for in vivo miRNA imaging including the dynamic monitoring of miRNA expression change and simultaneous in vivo imaging of multiple miRNAs.

A photoelectrochemical aptasensing platform assembled at the heterojunction interface of Cu3BiS3 sensitized CuV2O6 for bisphenol A.

The interaction between the sensitive interfaces of photoelectrochemical (PEC) semiconductor nanomaterials and microscopic matter creates endless potential for the efficient detection of endocrine disruptor. This work presents the development of a high-efficiency PEC aptasensor for bisphenol A (BPA) monitoring based on Cu3BiS3 sensitized CuV2O6 nanocomposites with exceptional visible-light PEC activity. We implemented the integration of Cu3BiS3 nanosheet photosensitizer to sensitize the CuV2O6 nanowire structure that was synthesized utilizing a facile hydrothermal approach. The band gap alignment between Cu3BiS3 and CuV2O6 facilitated enduring PEC response yielding an efficient interfacial structure. The surface of the CuV2O6/Cu3BiS3 electrode was modified with BPA aptamer, enabling specific binding with BPA and precise quantification of its content. The developed aptamer sensors possess a wide detection range of 5.00 × 10-1 to 5.00 × 104 ng/mL, and a low detection limit of 1.60 × 10-1 ng/mL (at S/N = 3). After undergoing 20 testing cycles and enduring long-term storage, the sensor maintained its stability and showcased excellent repeatability and reproducibility. This study presents a promising methodology for the detection of BPA in environmental settings.

Cancer Cell-Selective PD-L1 Inhibition via a DNA Safety Catch to Enhance Immunotherapy Specificity.

Immune checkpoint protein blockade (ICB) has emerged as a powerful immunotherapy approach, but suppressing immune-related adverse events (irAEs) for noncancerous cells and normal tissues remains challenging. Activatable ICB has been developed with tumor microenvironment highly-expressed molecules as stimuli, but they still lack precision and efficiency considering the diffusion of stimuli molecules in whole tumor tissue. Here we assemble PD-L1 with a duplex DNA strand, termed as "safety catch", to regulate its accessibility for ICB. The safety catch remains at "on" status for noncancerous cells to prevent ICB binding to PD-L1. Cancer cell membrane protein c-Met acts as a trigger protein to react with safety catch, which selectively exposes its hybridization region for ICB reagent. The ICB reagent is a retractable DNA nanostring with repeating hairpin-structural units, whose contraction drives PD-L1 clustering with endocytosis-guided degradation. The safety catch, even remained at "safety on" status, is removed from the cell membrane via a DNA strand displacement reaction to minimize its influence on noncancerous cells. This strategy demonstrates selective and potent immunotherapeutic capabilities only against cancer cells both in vitro and in vivo, and shows effective suppression of irAEs in normal tissues, therefore would become a promising approach for precise immunotherapy in mice.

Ultra-Galactocation to Sialic Acid on Tumor Cells with A Penta-Functional Dendritic Probe for Enhanced Immune-Killing.

Glycans on tumor cell surface have significant impacts in the immune-killing process. Here an ultra-galactocation to sialic acid (Sia) strategy is designed to hugely introduce galactose (Gal) to Sia and on tumor cells in vivo by using a penta-functional dendritic probe (Den@5F), which efficiently enhances the immune-killing of tumor cells. The Den@5F contains five different kinds of functional groups, including Gal, Cy5, amino, phenylboronic acid (PBA) and 4-(4-(hydroxymethyl)-2-methoxy-5-nitrophenoxy) butanoate (mNB), which can be conveniently prepared through a two-step reaction. After injecting into the tumor-bearing mouse, Den@5F can efficiently block Sia through the specific recognition between PBA and Sia on tumor cells and hugely introduce Gal through the subsequent photo-crosslinking between mNB and amino groups to multiply conjugate excessive Den@5Fs. The comprehensively blocked Sia can prevent the immune escape, and the hugely introduced Gal can promote the immune stimulation of the immune cells, which lead to an efficient enhancement of the immune-killing. The proposed strategy provides a significant and promising tool to promote the clinical immunotherapy of tumor.

An In-Situ-Tag-Generation Proximity Labeling Technology for Recording Cellular Interactions.

Obtaining information about cellular interactions is fundamental to the elucidation of physiological and pathological processes. Proximity labeling technologies have been widely used to report cellular interactions in situ; however, the reliance on addition of tag molecules typically restricts their application to regions where tags can readily diffuse, while the application in, for example, solid tissues, is susceptible. Here, we propose an "in-situ-tag-generation mechanism" and develop the GalTag technology based on galactose oxidase (GAO) for recording cellular interactions within three-dimensional biological solid regions. GAO mounted on bait cells can in situ generate bio-orthogonal aldehyde tags as interaction reporters on prey cells. Using GalTag, we monitored the dynamics of cellular interactions and assessed the targeting ability of engineered cells. In particular, we recorded, for the first time, the footprints of Bacillus Calmette-Guérin (BCG) invasion into the bladder tissue of living mice, providing a valuable perspective to elucidate the anti-tumor mechanism of BCG.

Cancer Cell-Selective Membrane Receptor Clustering Driven by VEGF Secretion for In Vivo Therapy.

Clustering of cell membrane receptors regulates cell behaviors. Although receptor clustering plans have achieved wide applications in cancer therapy, it still remains challenging to manipulate receptor clustering selectively for cancer cells with little influence on normal cells. Here, we design a Raji cell Selective MAnipulation of Receptor Clustering (SMARC) strategy for CD20, which is driven by endogenous secretion of Raji cells. Retractable DNA nanostrings with repeating hairpin-structured units are anchored to the cell membrane CD20, which contract in response to Raji cell-secreted vascular endothelial growth factor (VEGF) with corresponding CD20 clustering. The contraction of DNA nanostrings is intensified via a VEGF amplifier including DNA cyclic reactions to continuously trigger the foldings of hairpin-structured units in DNA nanostrings. The SMARC strategy shows selective and efficient apoptosis of Raji cells with little interference to normal B cells and demonstrates good in vivo therapeutic efficacy, which provides a promising tool for precise cancer therapy.