A MXene Hydrogel-Based Versatile Microrobot for Controllable Water Pollution Management.

The urgent demand for addressing dye contaminants in water necessitates the development of microrobots that exhibit remote navigation, rapid removal, and molecular identification capabilities. The progress of microrobot development is currently hindered by the scarcity of multifunctional materials. In this study, a plasmonic MXene hydrogel (PM-Gel) is synthesized by combining bimetallic nanocubes and Ti3C2Tx MXene through the rapid gelation of degradable alginate. The hydrogel can efficiently adsorb over 60% of dye contaminants within 2 min, ultimately achieving a removal rate of >90%. Meanwhile, the hydrogel exhibits excellent sensitivity in surface enhanced Raman scattering (SERS) detection, with a limit of detection (LOD) as low as 3.76 am. The properties of the plasmonic hydrogel can be further adjusted for various applications. As a proof-of-concept experiment, thermosensitive polymers and superparamagnetic particles are successfully integrated into this hydrogel to construct a versatile, light-responsive microrobot for dye contaminants. With magnetic and optical actuation, the robot can remotely sample, identify, and remove pollutants in maze-like channels. Moreover, light-driven hydrophilic-hydrophobic switch of the microrobots through photothermal effect can further enhance the adsorption capacity and reduced the dye residue by up to 58%. These findings indicate of a broad application potential in complex real-world environments.

Chemically Powered Nanomotors with Magnetically Responsive Function for Targeted Delivery of Exosomes.

Janus structure plays a crucial role in achieving chemically driven nanomotors with exceptional motion performance. However, Janus-structured chemically driven nanomotors with magnetic responsiveness are commonly fabricated by sputtering metal films. In the study, a self-assembly technique is employed to asymmetrically modify the surfaces of magnetic silica (SiO2@Fe3O4) nanoparticles with platinum nanoparticles, resulting in the formation of this kind nanomotors. Compared to platinum film, platinum nanoparticles exhibit a larger surface area and a higher catalytic activity. Hence, the nanomotors demonstrate improved diffusion capabilities at a significantly lower concentration (0.05%) of hydrogen peroxide (H2O2). Meanwhile, exosomes have gained attention as a potential tool for the efficient delivery of biological therapeutic drugs due to their biocompatibility. However, the clinical applications of exosomes are limited by their restricted tropism. The previously obtained nanomotors are utilized to deliver exosomes, greatly enhancing its targetability. The drug doxorubicin (DOX) is subsequently encapsulated within exosomes, acting as a representative drug model. Under the conditions of H2O2 concentration at the tumor site, the exosomes exhibited a significantly enhanced rate of entry into the breast cancer cells. The utilization of the nanomotors for exosomes presents a novel approach in the development of hybrid chemically and magnetically responsive nanomotors.

Highly Accurate Profiling of Exosome Phenotypes Using Super-resolution Tricolor Fluorescence Co-localization.

Exosomes contain a wealth of proteomic information, presenting promising biomarkers for the noninvasive early diagnosis of diseases, especially cancer. However, it remains a great challenge to accurately and reliably distinguish exosomes secreted from different types of cell lines. Fluorescence immunoassay is frequently used for exosome detection. Nonspecific adsorption in immunoassays is unavoidable and affects the reliability of assay results. Despite the fact that various methods have been proposed to reduce nonspecific adsorption, a more effective method that can eliminate the influence of nonspecific adsorption is still lacking. Here, we report a more convenient way (named SR-TFC) to remove the artifacts caused by nonspecific adsorption, which combines tricolor fluorescence labeling of target exosomes, tricolor super-resolution imaging, and pixel counting. The pixel counting method (named CFPP) is realized by MATLAB and can eliminate nonspecific binding sites at the single-pixel level, which has never been achieved before and could improve the reliability of detection to the maximum extent. Furthermore, as a proof-of-concept, profiling of exosomal membrane proteins and identification of breast cancer subpopulations are demonstrated. To enable multiplex breast cancer phenotypic analysis, three kinds of specific proteins are labeled to obtain the 3D phenotypic information on various exosomes. Breast cancer subtypes can be accurately identified according to the super-resolution images of some clinically relevant exosomal proteins. Worth mentioning is that, by selecting other biomarkers, classification of other cancers could also be realized using SR-TFC. Hence, the present work holds great potential in clinical cancer diagnosis and precision medicine.

Ultrasensitive Detection of Matrix Metalloproteinase 2 Activity Using a Ratiometric Surface-Enhanced Raman Scattering Nanosensor with a Core-Satellite Structure.

Matrix metalloproteinase 2 (MMP-2) has been considered a promising molecular biomarker for cancer diagnosis due to its related dysregulation. In this work, a core-satellite structure-powered ratiometric surface-enhanced Raman scattering (SERS) nanosensor with high sensitivity and specificity to MMP-2 was developed. The SERS nanosensor was composed of a magnetic bead encapsulated within a 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB)-labeled gold shell as the capture core and a 4-mercaptobenzonitrile (MBN)-encoded silver nanoparticle as the signal satellite, which were connected through a peptide substrate of MMP-2. MMP-2-triggered cleavage of peptides from the core surface resulted in a decrease of the SERS intensity of MBN. Since the SERS intensity of DTNB was used as an internal standard, the reliable and sensitive quantification of MMP-2 activity would be realized by the ratiometric SERS signal, with a limit of detection as low as 2.067 ng/mL and a dynamic range from 5 to 100 ng/mL. Importantly, the nanosensor enabled a precise determination of MMP-2 activity in tumor cell secretions, which may provide an avenue for early diagnosis and classification of malignant tumors.

A SERS-assisted 3D organotypic microfluidic chip for in-situ visualization and monitoring breast cancer extravasation process.

Extravasation, as one of the key steps in cancer metastasis, refers to the process where tumor cells escape the bloodstream by crossing the vascular endothelium and invade the targeted tissue, which accounts for the low five-year survival rate of cancer patients. Understanding the mechanism of cancer metastasis and inhibiting extravasation are crucial to improve patient prognosis. Here, a 3D organotypic microfluidic chip combined with SERS-based protein imprinted nanomaterials (SPINs) was proposed to study the extravasation process in vitro. The chip consists of a collagen gel channel and a vascular channel where human vein endothelial cells (HUVECs) and breast cancer cells are injected sequentially to induce extravasation. By comparing two subtypes of breast cancer cells (MCF-7 and MDA-MB-231), we successfully observed the difference in extravasation capabilities between two kinds of cells through fluorescence imaging. Meanwhile, thanks to the high specificity of molecular imprinting technology and the high sensitivity of surface enhanced Raman scattering (SERS), SPINs were utilized to analyze the concentration of several cancer secretions (interleukin-6 and interleukin-8) in complex biological fluid in real-time. Further, our model showed that downregulation of secretions by therapeutic drugs can inhibit the extravasation of breast cancers. This microfluidic model may pave the way for the fundamental research of the cancer metastasis and evaluating the therapeutic efficacy of potential drugs.

A Novel Ion Species- and Ion Concentration-Dependent Anti-Counterfeiting Based on Ratiometric Fluorescence Sensing of CDs@MOF-Nanofibrous Films.

Traditional fluorescent anti-counterfeiting labels based on "on-off" fluorescence can be easily cloned. It is important to explore advanced anti-counterfeiting fluorescent labels with high-level security. Here, a pioneering ion species- and ion concentration-dependent anti-counterfeiting technique is developed. By successive loading Cu2+ -sensitive yellow emitted carbon dots (Y-CDs) and Cu2+ non-sensitive blue emitted carbon dots (B-CDs) into metal-organic frameworks (MOFs) and followed by electrospinning, the B&Y-CDs@MOF-nanofibrous films are prepared. The results show that the use of MOF not only avoids the fluorescence quenching of CDs but also improves the fluorescence stability. The fluorescence Cu2+ -sensitivity of the CDs@MOF-nanofibrous films can be regulated by polymer coating or lamination. The fluorescent label consisting of different Cu2+ -sensitivity films will show Cu2+ concentration-dependent decryption information. Only at a specific ion species and concentration (Cu2+ solution of 40-90 µm), the true information can be read out. Less or more concentration (<40 or >90 µm) will lead to false information. The identification of the real information depends on both the species and the concentration. After Cu2+ treatment, the fluorescence of the label can be recovered by ethylenediaminetetraacetic acid disodium (EDTA-2Na) for further recycling. This work will open up a new door for designing high-level fluorescent anti-counterfeiting labels.

Long-lived SERS Matrix for Real-Time Biochemical Detection Using "Frozen" Transition State.

For the long-time tracking of biological events, maintaining the bioactivity of the analytes during the detection process is essential. Here, we show a versatile surface-enhanced Raman Scattering (SERS) platform, termed a superwettable-omniphobic lubricous porous SERS (SOLP-SERS) substrate. The SOLP-SERS substrate could generate a three-dimensional liquid "hotspots" matrix with an ultra-long lifetime (tens of days) by confining tiny amounts of liquids within the gaps between nanoparticles. Then, the analytes are trapped in the uniform liquid "hotspots", whose bioactivity can be well maintained over a long period of time during SERS detection. Limits of detection down to femtomolar levels were achieved for various molecules. More importantly, SERS signals were uniform within the substrate and remained stable for more than 30 days. As a proof-of-concept experiment, the dynamic detection of the polymerization of Aß peptides into amyloids was monitored by the SOLP-SERS substrate within 48 h. Moreover, the exosomes secreted by breast cancer cells, an important biomarker of cancer, were also measured. These results demonstrate that the SOLP-SERS platform will provide new insights into the development of real-time biochemical sensors with ultrahigh sensitivity.

A 3D-printed SERS bionic taster for dynamic tumor metabolites detection.

The variation of tumor-associated metabolites in extracellular microenvironment timely reflects the development, the progression and the treatment of cancers. Conventional methods for metabolite detection lack the efficiency to grasp the dynamic metabolic alterations. Herein, we developed a SERS bionic taster which enabled real-time analysis of extracellular metabolites. The instant information of cell metabolism was provided by the responsive Raman reporters, which experienced SERS spectral changes upon metabolite activation. Such a SERS sensor was integrated into a 3D-printed fixture which fits the commercial-standard cell culture dishes, allowing in-situ acquisition of the vibrational spectrum. The SERS taster can not only accomplish simultaneous and quantitative analysis of multiple tumor-associated metabolites, but also fulfill the dynamic monitoring of cellular metabolic reprogramming, which is expected to become a promising tool for investigating cancer biology and therapeutics.

A SERS Composite Hydrogel Device for Point-of-Care Analysis of Neurotransmitter in Whole Blood.

Point-of-care analysis of neurotransmitters in body fluids plays a significant role in healthcare improvement. Conventional approaches are limited by time-consuming procedures and usually require laboratory instruments for sample preparation. Herein, we developed a surface enhanced Raman spectroscopy (SERS) composite hydrogel device for the rapid analysis of neurotransmitters in whole blood samples. The PEGDA/SA composite hydrogel enabled fast separation of small molecules from the complex blood matrix, while the plasmonic SERS substrate allowed for the sensitive detection of target molecules. 3D printing was employed to integrate the hydrogel membrane and the SERS substrate into a systematic device. The sensor achieved highly sensitive detection of dopamine in whole blood samples with a limit of detection down to 1 nM. The whole detection process from sample preparation to SERS readout can be finished within 5 min. Due to the simple operation and rapid response, the device shows great potential in point-of-care diagnosis and the monitoring of neurological and cardiovascular diseases and disorders.

Nanoscale imaging of tumor cell exosomes by expansion single molecule localization microscopy (ExSMLM).

Tumor cell exosomes play a very important role in the process of tumor cell proliferation and metastasis. However, due to the nanoscale size and high heterogeneity of exosomes, in-depth understanding of their appearance and biological characteristics is still lacking. Expansion microscopy (ExM) is a method that embeds biological samples in a swellable gel to physically magnify the samples to improve the imaging resolution. Before the emergence of ExM, scientists had invented several super-resolution imaging techniques that could break the diffraction limit. Among them, single molecule localization microscopy (SMLM) usually has the best spatial resolution (20-50 nm). However, considering the small size of exosomes (30-150 nm), the resolution of SMLM is still not high enough for detailed imaging of exosomes. Hence, we propose a tumor cell exosomes imaging method that combines ExM and SMLM (i.e. Expansion SMLM, denoted as ExSMLM), which can realize the expansion and super-resolution imaging of tumor cell exosomes. In this technique, immunofluorescence was first performed to fluorescently label the protein markers on the exosomes, then the exosomes were polymerized into a swellable polyelectrolyte gel. The electrolytic nature of the gel made the fluorescently labeled exosomes undergo isotropic linear physical expansion. The expansion factor obtained in the experiment was about 4.6. Finally, SMLM imaging of the expanded exosomes was performed. Owing to the improved resolution of ExSMLM, nanoscale substructures of closely packed proteins were observed on single exosomes, which has never been achieved before. With such a high resolution, ExSMLM would have a great potential in detailed investigation of exosomes and exosome-related biological processes.

Red Blood Cell Membrane Camouflaged Mesoporous Silica Nanorods as Nanocarriers for Synergistic Chemo-Photothermal Therapy.

In recent years, nanoparticles camouflaged by red blood cell membrane (RBCM) have become a potential nano-drug delivery platform due to their good biocompatibility and immune evasion capability. Here, a multifunctional drug nanocarrier based on RBCM camouflaged mesoporous silica nanorods (MSNR) is presented, which can be used in pH and near-infrared (NIR) light triggered synergistic chemo-photothermal killing of cancer cells. To fabricate such a nanocarrier, MSNR and RBCM were prepared by the sol-gel method and modified hypotonic lysis method, respectively. Drugs were loaded into the pores of MSNR. Finally, RBCM was coated on the surface of MSNR by extrusion through a polycarbonate membrane. The advantages of the nanocarrier include: 1) MSNR can induce more cellular uptake than sphere shaped mesoporous silica nanoparticles. 2) The RBCM can reduce drug leakage and prevent clearance of the nanocarriers by macrophages. 3) By simultaneous loading doxorubicin (DOX) and indocyanine green (ICG), pH and NIR triggered synergistic chemo-photothermal therapy can be realized. In the experiment, we studied the drug releasing and cellular uptake of the nanocarriers in a breast cancer cell line (SKBR3 cells), in which a sufficient killing effect was observed. Such a multifunctional drug nanocarrier holds a broad application prospect in cancer treatment.

Metal nanoprobe-decorated all-inorganic perovskite nanocrystal-based fluorescence-linked immunosorbent assay for the detection of tumor-derived exosomes.

All-inorganic perovskite nanocrystals (CsPbX3 NCs, X = Cl, Br, I) are promising fluorescence materials for biological detection due to their excellent optical properties. However, there is still a challenge to obtain stable CsPbX3 NCs with more biofunctions. Here, we proposed a distinct strategy by absorbing the functionalized metal nanoprobes onto the phospholipid encapsulated CsPbX3 NCs to achieve CsPbX3-metal hybrids as probes for the detection of tumor-derived exosomes. Here, the metal nanoprobes have two functions: first, it endows phospholipid encapsulated CsPbX3 NCs with recognition ability; second, it avoids the fluorescence quenching of CsPbX3 NCs during the biological modification process by using metal nanoparticles as a bridge to connect with CsPbX3 NCs and various biomolecules. The obtained CPXD-AD exhibited a bright fluorescence signal, narrow full width at half-maximum (FWHM), and high specificity. Under optimal conditions, the CPXD-AD-based fluorescence-linked immunosorbent assay (FLISA) was successfully established and used for both qualitative and quantitative detection of tumor-derived exosomes.

Highly sensitive and specific detection of silver ions using a dual-color fluorescence co-localization strategy.

Ag+ ions are widely used in various fields of human life due to their unique properties and they threaten the environment and human health. The traditional methods for Ag+ detection commonly suffer from disadvantages including limited sensitivity, expensive equipment and complicated operating steps. Herein, we developed a highly specific dual-color fluorescence co-localization (DFC) strategy based on the C-Ag+-C structure for Ag+ detection. In this strategy, Ag+ ions can be captured to form C-Ag+-C base pairs, and these ions enable single-stranded DNAs to form double strands. The DFC strategy can exclude nonspecific interaction sites and greatly improve the sensitivity and specificity. By DFC of the QDs and Cy5 linked to the DNA strands, highly sensitive Ag+ detection was achieved in the concentration range from 0.14 pM to 200 nM, with a limit of detection (LOD) of 0.14 pM. Moreover, this method has been applied for the detection of Ag+ ions in real environmental samples with satisfactory recoveries. We believe that the DFC strategy is promising for Ag+ detection.

Fluorescence Super-Resolution Imaging Chip for Gene Silencing Exosomes.

Tumor cell-derived extracellular vesicles and their cargo of bioactive substances have gradually been recognized as novel biomarkers for cancer diagnosis. Meanwhile, the PD-L1 (Programmed Death-Ligand 1) protein, as an immune checkpoint molecule, is highly expressed on certain tumor cells and holds significant potential in immune therapy. In comparison to PD-L1 monoclonal antibodies, the inhibitory effect of PD-L1 siRNA (small interfering RNA) is more advantageous. In this article, we introduced a microfluidic chip integrating cell cultivation and exosome detection modules, which were intended for the investigation of the gene silencing effect of PD-L1 siRNA. Basically, cells were first cultured with PD-L1 siRNA in the chip. Then, the secreted exosomes were detected via super-resolution imaging, to validate the inhibitory effect of siRNA on PD-L1 expression. To be specific, a "sandwich" immunological structure was employed to detect exosomes secreted from HeLa cells. Immunofluorescence staining and DNA-PAINT (DNA Point Accumulation for Imaging in Nanoscale Topography) techniques were utilized to quantitatively analyze the PD-L1 proteins on HeLa exosomes, which enabled precise structural and content analysis of the exosomes. Compared with other existing PD-L1 detection methods, the advantages of our work include, first, the integration of microfluidic chips greatly simplifying the cell culture, gene silencing, and PD-L1 detection procedures. Second, the utilization of DNA-PAINT can provide an ultra-high spatial resolution, which is beneficial for exosomes due to their small sizes. Third, qPAINT could allow quantitative detection of PD-L1 with better precision. Hence, the combination of the microfluidic chip with DNA-PAINT could provide a more powerful integrated platform for the study of PD-L1-related tumor immunotherapy.

In Situ Super-Resolution Imaging of Telomeres with DNA-PAINT.

Telomeres are located at the ends of chromosomes and play an important role in maintaining the integrity of chromosomes and controlling the cycle of cell division. Studies have shown that abnormal telomere length may lead to the occurrence of some diseases. Therefore, accurate measurement of telomere length will be helpful for the prediction and diagnosis of related diseases. DNA point accumulation for imaging in nanoscale topography (PAINT) is an optical super-resolution technology that relies on the instantaneous binding of the fluorescent DNA imaging strand to the target epitope. Here, we present the first demonstration of DNA-PAINT-based in situ super-resolution imaging of telomeres as well as centromeres. For DNA-PAINT imaging, Cy5-labeled telomere DNA (5'-Cy5-TTTTTCCCTAACCCTAA-3') and Cy3-labeled centromere DNA (5'-Cy3-TTTTTAGCTTCTGTCTAGTTT-3') are utilized as the imager strands. Through an improved permeabilization strategy that we proposed, the imager strands can bind with intracellular telomeres and centromeres with high specificity, realizing super-resolution imaging of telomeres and centromeres. To check the applicability of DNA-PAINT in evaluating telomere length, we conducted an experiment using azidothymidine (AZT)-treated tumor cells as the imaging target. The DNA-PAINT imaging results clearly revealed the telomerase inhibition effect of AZT. Compared with single-molecule localization microscopy (SMLM) with peptide nucleic acid (PNA)-based fluorescence in situ hybridization (FISH), our method has the advantages of low cost, low toxicity, and simple equipment. Such a DNA-PAINT-based imaging strategy holds great potential in measuring telomere length with high accuracy, which would play an important role in the study of telomere-related diseases such as cancer.

A Programmable Plasmonic Gas Microsystem for Detecting Arbitrarily Combinated Volatile Organic Compounds (VOCs) with Ultrahigh Resolution.

For gas sensors, the ultrasensitive and highly selective detection of multiple components is of great significance in a wide range of applications extending from environment to healthcare, which is still a long-term challenge due to the single sensing mechanism of most sensors. Here, we combine the advantages of microfluidic chips and surface-enhanced Raman spectroscopy (SERS) spectra to fabricate a smart single-chip for simultaneously detecting an arbitrary combination of VOCs that incorporates different detection units, working on either a physisorption or chemisorption mechanism. Full integration of microfluidic and multiplex nanostructure components on one chip permits programmable design for sensing multifarious volatile compounds, and enables on-chip signal amplifications with increased reproducibility. As a proof-of-principle experiment, we demonstrate the simultaneous identification of 9 different gases that belong to aromatic compounds, aldehydes, ketones, or sulfides in one mixture, with high sensitivity (ppb level), high selectivity, and high robustness (error ∼8%). We further evaluated the application of our universal gas sensor in two scenarios including indoor air pollution monitoring and exhaled breath-based disease diagnosis. We expect that our design will improve the various practical applications of gas sensors.

Quantitative analysis of multiple breast cancer biomarkers using DNA-PAINT.

Immunotherapy has become an efficient treatment method of breast cancer. Detection of proteins such as PD-L1 and CTLA-4, which are important immune checkpoint molecules, is attracting more and more attention as they play key roles in immunotherapy. Here, by combining the high resolution of DNA-PAINT (DNA points accumulation for imaging in nanoscale topography) with the qPAINT quantitative analysis method, accurate spatial localization and absolute quantification of PD-L1 and CTLA-4 on the membrane of breast cancer cells could be achieved. Meanwhile, exchange-PAINT was also conducted to count three other biomarkers (EpCAM, EGFR, and HER2). Simultaneous analysis of these biomarkers can greatly facilitate the differentiation of different kinds of breast cancer. Such a simple quantitative analysis method holds great potential in diagnosis and immunotherapy of cancers.

Wearable SERS Sensor Based on Omnidirectional Plasmonic Nanovoids Array with Ultra-High Sensitivity and Stability.

Surface-enhanced Raman spectroscopy (SERS) is a promising technology for wearable sensors due to its fingerprint spectrum and high detection sensitivity. However, since SERS-activity is sensitive to both the distribution of "hotspots" and excitation angle, it is profoundly challenging to develop a wearable SERS sensor with high stability under various deformations during movements. Herein, inspired by omnidirectional light-harvesting of the compound eye of Xenos Peckii, a wearable SERS sensor is developed using omnidirectional plasmonic nanovoids array (OPNA), which is prepared by assembling a monolayer of metal nanoparticles into the artificial plasmonic compound-eye (APC). Specifically, APC is an interconnected frame containing omnidirectional "pockets" and acts as an "armour", not only rendering a broadband and omnidirectional enhancement of "hotspots" in the delicate nanoparticles array, but also maintaining an integrity of the "hotspots" against external mechanical deformations. Furthermore, an asymmetry super-hydrophilic pattern is fabricated on the surface of OPNA, endowing the hydrophobic OPNA with the ability to spontaneously extract and concentrate the analytes from sweat. Such an armored SERS sensor can enable the wearable and in situ analysis with high sensitivity and stability, exhibiting great potential in point-of-care analysis.

Triple-color fluorescence co-localization of PD-L1-overexpressing cancer exosomes.

Programed cell death ligand 1 (PD-L1) is a protein biomarker overexpressed on exosomes derived from tumor cells. It plays an important role in tumor diagnosis, screening, evaluation of therapeutic efficacy, and prognosis. In this study, a facile method is presented to detect PD-L1-overexpressing cancer exosomes with high specificity and sensitivity. First, gold nanospheres (GNSs) were attached to the bottom of an eight-well chambered slide by electrostatic adsorption, forming the detection substrate. Then, Cy5-labeled CD63 aptamers (i.e., the capture probes) were modified on the GNSs by Au-S bond. After adding samples containing target exosomes which were stained by membrane dyes DiI in advance, FAM-labeled PD-L1 aptamers (i.e., the immunoprobes) were added to recognize PD-L1 on the target exosomes. By triple-color fluorescence co-localization (TFC) of the Cy5, DiI, and FAM channels, highly sensitive and reliable detection of the PD-L1-overexpressing exosomes was achieved in the concentration range 7.78 × 101 to 7.78 × 104 particles/mL with a detection limit down to 6 particles/mL. The advantages of the proposed detection method include the following; first, the detection substrate is easy to prepare and convenient to clean. Second, the TFC strategy can completely exclude nonspecific reaction sites and thus significantly improves the accuracy. Such a facile and reliable detection method holds a great potential in exosome-based cancer theranostics. In this paper, we proposed a triple-color fluorescence co-localization (TFC) strategy to significantly improve the reliability of exosome detection and the detection substrate is easy to prepare and convenient to clean. In addition, the LOD is down to 6 particles/mL, which is quite low compared with other detection methods.

Water-dispersed CsPbBr3 nanocrystals for single molecule localization microscopy with high location accuracy for targeted bioimaging.

Single-molecule localization microscopy (SMLM) is one of the most promising super-resolution imaging techniques for visualizing ultrasmall cellular structures. Here, water-dispersed perovskite CsPbBr3 nanocrystals (CsPbBr3 NCs) fabricated by a one-step mechanochemical method are explored as a SMLM fluorophore for bioimaging. Due to their ultrahigh photoluminescence quantum yield (PLQY), inherent frequent fluorescence blinking, proper duty cycle and long-term photostability, an extremely high location precision of ∼3 nm was achieved, a sixfold enhancement than those reported previously. In addition, the spatial resolution of a SMLM image depends on the size of CsPbBr3 NCs, which is approximately 23 nm. Two closely spaced CsPbBr3 NCs with a gap of 40 nm can be clearly distinguished in the SMLM image. More importantly, unlike most perovskite quantum dots (QDs), one-step mechanochemically prepared CsPbBr3 NCs can retain their excellent fluorescence characteristics even after surface biofunctionalization, greatly reducing the current limitations of perovskite QDs on bioimaging. As an example, cell-derived exosomes (30-150 nm in diameter) labeled with CsPbBr3 NCs were easily identified by SMLM. In addition, after being functionalized with biotin, targeted SMLM imaging of the nuclear lamina or cell membranes of cells was achieved with an enhanced resolution. This work may open up a promising avenue to expand the field of perovskite QD-based SMLM to bioimaging with a high location accuracy.