Self-Matching Assembly of Chiral Gold Nanoparticles Leads to High Optical Asymmetry and Sensitive Detection of Adenosine Triphosphate.

To achieve chiral amplification, life uses small chiral molecules as building blocks to construct hierarchical chiral architectures that can realize advanced physiological functions. Inspired by the chiral amplification strategy of nature, we herein demonstrate that the chiral assembly of chiral gold nanorods (GNRs) leads to enhanced optical asymmetry factors (g-factors), up to 0.24. The assembly of chiral GNRs, dictated by structural self-matching, leads to g-factors with over 100-fold higher values than those of individual chiral GNRs, as confirmed by numerical simulations. Moreover, the efficient optical asymmetry of chiral GNR assemblies enables their application as highly sensitive sensors of adenosine triphosphate (ATP detection limit of 1.0 µM), with selectivity against adenosine diphosphate and adenosine monophosphate.

An ultra-small organic dye nanocluster for enhancing NIR-II imaging-guided surgery outcomes.

PURPOSE: The accuracy of surgery for patients with solid tumors can be greatly improved through fluorescence-guided surgery (FGS). However, existing FGS technologies have limitations due to their low penetration depth and sensitivity/selectivity, which are particularly prevalent in the relatively short imaging window (< 900 nm). A solution to these issues is near-infrared-II (NIR-II) FGS, which benefits from low autofluorescence and scattering under the long imaging window (> 900 nm). However, the inherent self-assembly of organic dyes has led to high accumulation in main organs, resulting in significant background signals and potential long-term toxicity. METHODS: We rationalize the donor structure of donor-acceptor-donor-based dyes to control the self-assembly process to form an ultra-small dye nanocluster, thus facilitating renal excretion and minimizing background signals. RESULTS: Our dye nanocluster can not only show clear vessel imaging, tumor and tumor sentinel lymph nodes definition, but also achieve high-performance NIR-II imaging-guided surgery of tumor-positive sentinel lymph nodes. CONCLUSION: In summary, our study demonstrates that the dye nanocluster-based NIR-II FGS has substantially improved outcomes for radical lymphadenectomy.

Unlocking lysosomal acidity to activate membranolytic module for accurately cancer theranostics.

Chemotherapy drug efflux, toxic side effects, and low efficacy against drug-resistant cells have plagued safe and efficient cancer theranostics. However, the materials or methods that resolve these defects all-in-one are scarce. Here, a new cancer theranostics strategy is proposed by utilizing changes in lysosomal acidity in cancer cells to activate the membranolytic model to overcome these obstacles together. Therefore, a simple fluorescent anthracene derivative Lyso-Mito is developed, which has a perfect pKa (4.62) value that falls between the pH of lysosomes in cancer and normal cells. Lyso-Mito itself can precisely target and convert the pH perturbation of lysosomes in cancer cells to fluorescent response and membranolytic module activity to accomplish the low drug efflux, weak toxic side effects, and low drug-resistant cancer diagnosis and treatment without linking other functional units or any additional assistance. Hereby, a new cancer theranostics strategy of integrating organelle microenvironment and the membranolytic model is realized.

NIR-II nanoprobes for investigating the glymphatic system function under anesthesia and stroke injury.

The glymphatic system plays an important role in the transportation of cerebrospinal fluid (CSF) and the clearance of metabolite waste in brain. However, current imaging modalities for studying the glymphatic system are limited. Herein, we apply NIR-II nanoprobes with non-invasive and high-contrast advantages to comprehensively explore the function of glymphatic system in mice under anesthesia and cerebral ischemia-reperfusion injury conditions. Our results show that the supplement drug dexmedetomidine (Dex) enhances CSF influx in the brain, decreases its outflow to mandibular lymph nodes, and leads to significant differences in CSF accumulation pattern in the spine compared to isoflurane (ISO) alone, while both ISO and Dex do not affect the clearance of tracer-filled CSF into blood circulation. Notably, we confirm the compromised glymphatic function after cerebral ischemia-reperfusion injury, leading to impaired glymphatic influx and reduced glymphatic efflux. This technique has great potential to elucidate the underlying mechanisms between the glymphatic system and central nervous system diseases.

NIR-II Imaging and Sandwiched Plasmonic Biosensor for Ultrasensitive Intraoperative Definition of Tumor-Invaded Lymph Nodes.

Radical lymphadenectomy remains the cornerstone of preventing tumor metastasis through the lymphatic system. Current surgical resection of lymph nodes (LNs) based on fluorescence-guided surgery (FGS) suffers from low sensitivity/selectivity with only qualitative information, hampering accurate intraoperative decision-making. Herein, we develop a modularized theranostic system including NIR-II FGS and a sandwiched plasmonic chip (SPC). Intraoperative NIR-II FGS and detection of tumor-positive lymph nodes were performed on the gastric tumor to determine the feasibility of the modularized theranostic system in defining LN metastasis. Under the NIR-II imaging window, the orthotopic tumor and sentinel lymph nodes (SLNs) were successfully excised without ambient light interference in the operating room. Importantly, the SPC biosensor achieved 100% sensitivity and 100% specificity for tumor markers and realized rapid and high-throughput intraoperative SLN detection. We propose the synergetic design of combining the NIR-II FGS and suitable biosensor will substantially improve the efficiency of cancer diagnosis and therapy follow-up.

Three-Dimensional Histological Electrophoresis for High-Throughput Cancer Margin Detection in Multiple Types of Tumor Specimens.

Accurate identification of tumor margins during cancer surgeries relies on a rapid detection technique that can perform high-throughput detection of multiple suspected tumor lesions at the same time. Unfortunately, the conventional histopathological analysis of frozen tissue sections, which is considered the gold standard, often demonstrates considerable variability, especially in many regions without adequate access to trained pathologists. Therefore, there is a clinical need for a multitumor-suitable complementary tool that can accurately and high-throughput assess tumor margins in every direction within the surgically resected tissue. We herein describe a high-throughput three-dimensional (3D) histological electrophoresis device that uses tumor-specific proteins to identify and contour tumor margins intraoperatively. Testing on seven cell-line xenograft models and human cervical cancer models (representing five types of tissues) demonstrated the high-throughput detection utility of this approach. We anticipate that the 3D histological electrophoresis device will improve the accuracy and efficiency of diagnosing a wide range of cancers.

Naked-Eye Readable Microarray for Rapid Profiling of Antibodies against Multiple SARS-CoV-2 Variants.

Novel high-throughput protein detection technologies are critically needed for population-based large-scale SARS-CoV-2 antibody detection as well as for monitoring quality and duration of immunity against virus variants. Current protein microarray techniques rely heavily on labeled transduction methods that require sophisticated instruments and complex operations, limiting their clinical potential, particularly for point-of-care (POC) applications. Here, we developed a label-free and naked-eye readable microarray (NRM) based on a thickness-sensing plasmon ruler, enabling antibody profiling within 30 min. The NRM chips provide 100% accuracy for neutralizing antibody detection by efficiently screening antigen types and experimental conditions and allow for the profiling of antibodies against multiple SARS-CoV-2 variants in clinical samples. We further established a flexible "barcode" NRM assay with a simple tape-based operation, enabling an effective smartphone-based readout and analysis. These results demonstrate new strategies for high-throughput protein detection and highlight the potential of novel protein microarray techniques for realistic clinical applications.

The Formation Mechanism of Carbonized Polymer Dots: Crosslinking-Induced Nucleation and Carbonization.

Carbon dots (CDs), as a kind of zero-dimensional nanomaterials, have been widely synthesized by bottom-up methods from various precursors. However, the formation mechanism is still unclear and controversial, which also brings difficulty to the regulation of structures and properties. Only some tentative formation processes were postulated by analyzing the products obtained at different reaction times and temperatures. Here, the effect of crosslinking on the formation of carbonized polymer dots (CPDs) is explored. Crosslinking-induced nucleation and carbonization (CINC) is proposed as the driving force for the formation of CPDs. Under hydrothermal synthesis, the precursors are initiated to polymerize and crosslink. The crosslinking brings higher hydrophobicity to generate the hydrophilic/hydrophobic microphase separation, which promotes dehydration and carbonization resulting in the formation of CPDs. Based on the principle of CINC, the influence factors of size are also revealed. Moreover, the dissipative particle dynamics (DPD) simulation is employed to support this formation mechanism. This concept of CINC will bring light to the formation process of CPDs, as well as facilitate the regulation of CPDs' size and photoluminescence.

Dye-Triplet-Sensitized Downshifting Nanoprobes with Ratiometric Dual-NIR-IIb Emission for Accurate In Vivo Detection.

Despite the emerging near-infrared-IIb (NIR-IIb, 1500-1700 nm) bioimaging significantly improving the in vivo penetration depth and resolution, quantitative detection with accuracy remains challenging due to its inhomogeneous fluorescence signal attenuation in biological tissue. Here, ratiometric dual-NIR-IIb in vivo detection with excitation wavelengths of 808 and 980 nm is presented using analyte-responsive dye-triplet-sensitized downshifting nanoprobes (DSNPs). NIR cyanine dye IR-808, a recognizer of biomarker hypochlorite (ClO-), is introduced to trigger a triplet energy transfer process from the dye to Er3+ ions of DSNPs under 808 nm excitation, facilitating the formation of an analyte-responsive 1525 nm NIR-IIb assay channel. Meanwhile, DSNPs also enable emitting intrinsic nonanalyte-dependent downshifting fluorescence at the same NIR-IIb window under 980 nm excitation, serving as a self-calibrated signal to alleviate the interference from the probe amount and depth. Due to the two detected emissions sharing identical light propagation and scattering, the ratiometric NIR-IIb signal is demonstrated to ignore the depth of penetration in biotissue. The arthritis lesions are distinguished from normal tissue using ratiometric probes, and the amount of ClO- can be accurately output by the established detection curves.

Carbonized Polymer Dots Assemble in Proton-Conducting Channels to Enhance the Conductivity and Selectivity Simultaneously for High-Performance Fuel Cells.

Fabricating polymer electrolyte membranes (PEMs) simultaneously with high ion conductivity and selectivity has always been an ultimate goal in many membrane-integrated systems for energy conversion and storage. Constructing broader ion-conducting channels usually enables high-efficient ion conductivity while often bringing increased crossover of other ions or molecules simultaneously, resulting in decreased selectivity. Here, the ultra-small carbon dots (CDs) with the selective barriers are self-assembled within proton-conducting channels of PEMs through electrostatic interaction to enhance the proton conductivity and selectivity simultaneously. The functional CDs regulate the nanophase separation of PEMs and optimize the hydration proton network enabling higher-efficient proton transport. Meanwhile, the CDs within proton-conducting channels prevent fuel from permeating selectively due to their repelling and spatial hindrance against fuel molecules, resulting in highly enhanced selectivity. Benefiting from the improved conductivity and selectivity, the open-circuit voltage and maximum power density of the direct methanol fuel cell (DMFC) equipped with the hybrid membranes raised by 23% and 93%, respectively. This work brings new insight to optimize polymer membranes for efficient and selective transport of ions or small molecules, solving the trade-off of conductivity and selectivity.

NIR-II Imaging-Guided Mitochondrial-Targeting Organic Nanoparticles for Multimodal Synergistic Tumor Therapy.

Effectively interfering energy metabolism in tumor cells and simultaneously activating the in vivo immune system to perform immune attacks are meaningful for tumor treatment. However, precisely targeted therapy is still a huge challenge. Herein, a mitochondrial-targeting phototheranostic system, FE-T nanoparticles (FE-T NPs) are developed to damage mitochondria in tumor cells and change the tumor immunosuppressive microenvironment. FE-T NPs are engineered by encapsulating the near-infrared (NIR) absorbed photosensitizer IR-FE-TPP within amphiphilic copolymer DSPE-SS-PEG-COOH for high-performing with simultaneous mitochondrial-targeting, near-infrared II (NIR-II) fluorescence imaging, and synchronous photothermal therapy (PTT) /photodynamic therapy (PDT) /immune therapy (IMT). In tumor treatment, the disulfide in the copolymer can be cleaved by excess intracellular glutathione (GSH) to release IR-FE-TPP and accumulate in mitochondria. After 808 nm irradiation, the mitochondrial localization of FE-T NPs generated reactive oxygen species (ROS), and hyperthermia, leading to mitochondrial dysfunction, photoinductive apoptosis, and immunogenic cell death (ICD). Notably, in situ enhanced PDT/PTT in vivo via mitochondrial-targeting with FE-T NPs boosts highly efficient ICD toward excellent antitumor immune response. FE-T NPs provide an effective mitochondrial-targeting phototheranostic nanoplatform for imaging-guided tumor therapy.

High-precision detection and navigation surgery of colorectal cancer micrometastases.

Surgical resection is an effective treatment for colorectal cancer (CRC) patients, whereas occult metastases hinder the curative effect. Currently, there is no effective method to achieve intraoperatively diagnosis of tumor-positive lymph nodes (LNs). Herein, we adopt a near-infrared-II (NIR-II) organic donor-pi-acceptor-pi-donor probe FE-2PEG, which exhibits bright fluorescence over 1100 nm, excellent photostability, blood circulation time, and biocompatibility, to achieve high-performance bioimaging with improved temporal and spatial resolution. Importantly, the FE-2PEG shows efficient passive enrichment in orthotopic CRC, metastatic mesenteric LNs, and peritoneal metastases by enhanced permeability and retention effect. Under NIR-II fluorescence-guided surgery (FGS), the peritoneal micrometastases were resected with a sensitivity of 94.51%, specificity of 86.59%, positive predictive value (PPV) of 96.57%, and negative predictive value of 79.78%. The PPV still achieves 96.07% even for micrometastases less than 3 mm. Pathological staining and NIR-II microscopy imaging proved that FE-2PEG could successfully delineate the boundary between the tumor and normal tissues. Dual-color NIR-II imaging strategy with FE-2PEG (1100 ~ 1300 nm) and PbS@CdS quantum dots (> 1500 nm) successfully protects both blood supply and normal tissues during surgery. The NIR-II-based FGS provides a promising prospect for precise intraoperative diagnosis and minimally invasive surgery of CRC.

Ultrabright Renal-Clearable Cyanine-Protein Nanoprobes for High-Quality NIR-II Angiography and Lymphography.

The renal-clearable aspect of imaging agent with minimum toxicity issues and side effects is essential for clinical translation, yet clinical near-infrared-I/II (NIR-I/II) fluorophores with timely renal-clearance pathways are very limited. Herein, we rationally develop the cyanine-protein composite strategy through covalent bonding of ß-lactoglobulin (ß-LG) and chloride-cyanine dye to produce a brilliant and stable NIR-I/II fluorophore (e.g., ß-LG@IR-780). The ß-LG acts as a protecting shell with small molecular weight (18.4 kDa) and ultrasmall size (<5 nm), thus endowing the ß-LG@IR-780 with excellent biocompatibility and renal excretion. Our ß-LG@IR-780 probe enables noninvasive and precise NIR-II visualization of the physiological and pathological conditions of the vascular and lymphatic drainage system, facilitating intraoperative imaging-guided surgery and postoperative noninvasive monitoring. The minimum accumulation of our probes in the main organs improves the overall biosafety. This study provides a facile methodology for new-generation NIR-II fluorophores and largely improves the brightness and pharmacokinetics of small molecular dyes.

Thickness-Sensing Sandwiched Plasmonic Biosensors Enable Label-Free Naked-Eye Antibody Quantification.

Clinical serology assays for detecting the antibodies of the virus are time-consuming, are less sensitive/selective, or rely on sophisticated detection instruments. Here, we develop a sandwiched plasmonic biosensor (SPB) for supersensitive thickness-sensing via utilizing the distance-dependent electromagnetic coupling in sandwiched plasmonic nanostructures. SPBs quantitatively amplify the thickness changes on the nanoscale range (sensitivity: ∼2% nm-1) into macroscopically visible signals, thereby enabling the rapid, label-free, and naked-eye detection of targeted biomolecular species (via the thickness change caused by immunobinding events). As a proof of concept, this assay affords a broad dynamic range (7 orders of magnitude) and a low LOD (∼0.3 pM), allowing for the extremely accurate SARS-CoV-2 antibody quantification (sensitivity/specificity: 100%/∼99%, with a portable optical fiber device). This strategy is suitable for high-throughput multiplexed detection and smartphone-based sensing at the point-of-care, which can be expanded for various sensing applications beyond the fields of viral infections and vaccination.

Bright quantum dots emitting at ∼1,600 nm in the NIR-IIb window for deep tissue fluorescence imaging.

With suppressed photon scattering and diminished autofluorescence, in vivo fluorescence imaging in the 1,500- to 1,700-nm range of the near-IR (NIR) spectrum (NIR-IIb window) can afford high clarity and deep tissue penetration. However, there has been a lack of NIR-IIb fluorescent probes with sufficient brightness and aqueous stability. Here, we present a bright fluorescent probe emitting at ∼1,600 nm based on core/shell lead sulfide/cadmium sulfide (CdS) quantum dots (CSQDs) synthesized in organic phase. The CdS shell plays a critical role of protecting the lead sulfide (PbS) core from oxidation and retaining its bright fluorescence through the process of amphiphilic polymer coating and transferring to water needed for imparting aqueous stability and compatibility. The resulting CSQDs with a branched PEG outer layer exhibited a long blood circulation half-life of 7 hours and enabled through-skin, real-time imaging of blood flows in mouse vasculatures at an unprecedented 60 frames per second (fps) speed by detecting ∼1,600-nm fluorescence under 808-nm excitation. It also allowed through-skin in vivo confocal 3D imaging of tumor vasculatures in mice with an imaging depth of ∼1.2 mm. The PEG-CSQDs accumulated in tumor effectively through the enhanced permeation and retention effect, affording a high tumor-to-normal tissue ratio up to ∼32 owing to the bright ∼1,600-nm emission and nearly zero autofluorescence background resulting from a large ∼800-nm Stoke's shift. The aqueous-compatible CSQDs are excreted through the biliary pathway without causing obvious toxicity effects, suggesting a useful class of ∼1,600-nm emitting probes for biomedical research.

Noninvasive In Vivo Imaging in the Second Near-Infrared Window by Inorganic Nanoparticle-Based Fluorescent Probes.

The fluorescence imaging in the second near-infrared window (NIR-II, 1000-1700 nm) has emerged as a new method for in vivo imaging and attracted considerable attention in the past decade. Owing to the suppressed photon scattering and diminished autofluorescence, in vivo fluorescence imaging in NIR-II window can afford deep tissue penetration depth with high clarity. Inorganic nanoparticle-based fluorescent probes in the NIR-II window have greatly prospered the field into a development stage because of their superior traits, including adjustable emission covering the whole NIR-II window and abundant surface functional groups that facilitate chemical modification and bioconjugation, etc. In this Feature, we introduce the unique imaging performance of the NIR-II optical window and highlight the latest development of noninvasive biological fluorescent imaging in NIR-II window using inorganic nanoparticle-based probes. A perspective on the challenge and future direction of inorganic nanoparticle-based NIR-II probes is also discussed.

Molecular imaging of biological systems with a clickable dye in the broad 800- to 1,700-nm near-infrared window.

Fluorescence imaging multiplicity of biological systems is an area of intense focus, currently limited to fluorescence channels in the visible and first near-infrared (NIR-I; ∼700-900 nm) spectral regions. The development of conjugatable fluorophores with longer wavelength emission is highly desired to afford more targeting channels, reduce background autofluorescence, and achieve deeper tissue imaging depths. We have developed NIR-II (1,000-1,700 nm) molecular imaging agents with a bright NIR-II fluorophore through high-efficiency click chemistry to specific molecular antibodies. Relying on buoyant density differences during density gradient ultracentrifugation separations, highly pure NIR-II fluorophore-antibody conjugates emitting ∼1,100 nm were obtained for use as molecular-specific NIR-II probes. This facilitated 3D staining of ∼170-µm histological brain tissues sections on a home-built confocal microscope, demonstrating multicolor molecular imaging across both the NIR-I and NIR-II windows (800-1,700 nm).

Crosslink-Enhanced Emission Effect on Luminescence in Polymers: Advances and Perspectives.

The crosslink-enhanced emission effect was first proposed to explore the strong luminescence of nonconjugated polymer dots possessing only either non-emissive or weakly emissive sub-luminophores. Interesting phenomena in recent research indicate such enhancement caused by extensive crosslinking appears in diverse luminescent polymers with sub-luminophores (electron-rich heteroatomic moieties) or luminophores (conjugated π domains). This enhancement can promote the emission from nonluminous to luminous, from weakly luminous to strongly luminous, and even convert the pathway of radiative transitions. The concept of the crosslink-enhanced emission effect should be updated and extended to an in-depth spatial effect, such as electron overlap and energy splitting in confined domains by effective crosslinking, more than initial immobilization. This Minireview outlines the development of the crosslink-enhanced emission effect from the perspective of the detailed classification, inherent mechanism and applicable systems. An outlook on the further exploration and application of this theory are also proposed.

Exceedingly Small Gadolinium Oxide Nanoparticles with Remarkable Relaxivities for Magnetic Resonance Imaging of Tumors.

Gd chelates have occupied most of the market of magnetic resonance imaging (MRI) contrast agents for decades. However, there have been some problems (nephrotoxicity, non-specificity, and low r1 ) that limit their applications. Herein, a wet-chemical method is proposed for facile synthesis of poly(acrylic acid) (PAA) stabilized exceedingly small gadolinium oxide nanoparticles (ES-GON-PAA) with an excellent water dispersibility and a size smaller than 2.0 nm, which is a powerful T1 -weighted MRI contrast agent for diagnosis of diseases due to its remarkable relaxivities (r1 = 70.2 ± 1.8 mM-1 s-1 , and r2 /r1 = 1.02 ± 0.03, at 1.5 T). The r1 is much higher and the r2 /r1 is lower than that of the commercial Gd chelates and reported gadolinium oxide nanoparticles (GONs). Further ES-GON-PAA is developed with conjugation of RGD2 (RGD dimer) (i.e., ES-GON-PAA@RGD2) for T1 -weighted MRI of tumors that overexpress RGD receptors (i.e., integrin αv ß3 ). The maximum signal enhancement (ΔSNR) for T1 -weighted MRI of tumors reaches up to 372 ± 56% at 2 h post-injection of ES-GON-PAA@RGD2, which is much higher than commercial Gd-chelates (<80%). Due to the high biocompatibility and high tumor accumulation, ES-GON-PAA@RGD2 with remarkable relaxivities is a promising and powerful T1 -weighted MRI contrast agent.

An Albumin Sandwich Enhances in Vivo Circulation and Stability of Metabolically Labile Peptides.

The effectiveness of numerous molecular drugs is hampered by their poor pharmacokinetics. Different from previous approaches with limited effectiveness, most recently, emerging high-affinity albumin binding moieties (ABMs) for in vivo hitchhiking of endogenous albumin opens up an avenue to chaperone small molecules for long-acting therapeutics. Although several FDA-approved fatty acids have shown prolonged residence and therapeutic effect, an easily synthesized, water-soluble, and high-efficiency ABM with versatile drug loading ability is urgently needed to improve the therapeutic efficacy of short-lived constructs. We herein identified an ideal bivalent Evans blue derivative, denoted as N(tEB)2, as a smart ABM-delivery platform to chaperone short-lived molecules, through both computational modeling screening and efficient synthetic schemes. The optimal N(tEB)2 could reversibly link two molecules of albumin through its two binding heads with a preferable spacer, resulting in significantly extended circulation half-life of a preloaded cargo and water-soluble. Notably, this in situ dimerization of albumin was able to sandwich peptide therapeutics to protect them from proteolysis. As an application, we conjugated N(tEB)2 with exendin-4 for long-acting glucose control in a diabetic mouse model, and it was superior to both previously tested NtEB-exendin-4 (Abextide) and the newly FDA-approved semaglutide, which has been arguably the best commercial weekly formula so far. Hence, this novel albumin binder has excellent clinical potential for next-generation biomimetic drug delivery systems.