Quantum Dots: A Promising Fluorescent Label for Probing Virus Trafficking

Quantum Dot-Based Three-Dimensional Single-Particle Tracking Characterizes the Evolution of Spatiotemporal Heterogeneity in Necrotic Cells

Cell death is a fundamental biological process with different modes including apoptosis and necrosis. In contrast to programmed apoptosis, necrosis was previously considered disordered and passive, but it is now being realized to be under regulation by certain biological pathways. However, the intracellular dynamics that coordinates with cellular structure changes during necrosis remains unknown, limiting our understanding of the principles of necrosis. Here, we characterized the spatiotemporal intracellular diffusion dynamics in cells undergoing necrosis, using three-dimensional single-particle tracking of quantum dots. We found temporally increased diffusion rates in necrotic cells and spatially enhanced diffusion heterogeneity in the cell periphery, which could be attributed to the reduced molecular crowding resulting from cell swelling and peripheral blebbing, respectively. Moreover, the three-dimensional intracellular diffusion transits from strong anisotropy to nearly isotropy, suggesting a remodeling of the cytoarchitecture that relieves the axial constraint on intracellular diffusion during necrosis. Our results reveal the remarkable alterations of intracellular diffusion dynamics and biophysical properties in necrosis, providing insight into the well-organized nonequilibrium necrotic cell death from a biophysical perspective.

Multihierarchical Regulation To Achieve Quantum Dot Nanospheres with a Photoluminescence Quantum Yield Close to 100

Quantum dots (QDs) exhibit superior brightness and photochemical stability, making them the preferred option for highly sensitive single-molecule detection compared with fluorescent dyes or proteins. Nevertheless, their high surface energy leads to nonspecific adsorption and poor colloidal stability. In the past decades, we have found that QD-based fluorescent nanoparticles (FNs) can not only address these limitations but also enhance detection sensitivity. However, the photoluminescence quantum yield (PLQY) of FNs is significantly lower compared with that of original QDs. It is urgent to develop a strategy to solve the issue, aiming to further enhance detection sensitivity. In this study, we found that the decrease of PLQY of FNs prepared by free radical polymerization was attributed to two factors: (1) generation of defects that can cause nonradiative transitions resulting from QD-ligands desorption and QD-shell oxidation induced by free radicals; (2) self-absorption resulting from aggregation caused by incompatibility of QDs with polymers. Based on these, we proposed a multihierarchical regulation strategy that includes: (1) regulating QD-ligands; (2) precisely controlling free radical concentration; and (3) constructing cross-linked structures of polymer to improve compatibility and to reduce the formation of surface defects. It is crucial to emphasize that the simultaneous coordination of multiple factors is essential. Consequently, a world-record PLQY of 97.6% for FNs was achieved, breaking through the current bottleneck at 65%. The flexible application of this regulatory concept paves the way for the large-scale production of high-brightness QD-polymer complexes, enhancing their potential applications in sensitive biomedical detection.

Analyte-perturbed balance between reducibility and fluorescence of Ti3C2 MXene quantum dots for label-free, dual-mode detection of silver ions

BACKGROUND

As an emerging and attractive low-dimensional functional materials, Ti3C2 MXene quantum dots (QDs) enlarge the toolbox of fluorescence sensing. However, monochromatic fluorescence, which only provide one single signal, is often beset by challenges such as false-positive readouts and limitations in selectivity. Consequently, to improve the sensing accuracy by means of cross-verified dual-signal authentication, the endeavor to engineer dual-mode nanoprobes based on Ti3C2 QDs, incorporating both the capability of fluorescence and an alternative sensing mechanism, emerges as a compelling avenue.

RESULTS

Here, based on the alterations in colorimetric and fluorescent signals of Ti3C2 QDs with the addition of Ag+, we propose a dual-mode sensor obviating the necessity for nanoprobe labeling. Owing to the decent reducibility of Ti3C2 QDs, Ag+ is adsorbed and reduced, resulting in the generation of plasmonic Ag nanoparticles (NPs), which simultaneously trigger colorimetric responses of the solution and enhance the fluorescent emission of Ti3C2 QDs. The confluence of colorimetry and fluorometry within this strategy optimally harnesses the modulating role of the acquired Ag NPs on the reducing capability and fluorescence characteristics of Ti3C2 QDs. The equilibrium imparts versatility and promising prospects to this analyte-triggered label-free method, which enables a remarkable specificity and an excellent detecting limit (0.45 μM) for Ag+.

SIGNIFICANCE

The balance between reducibility and fluorescence of Ti3C2 QDs for dual-mode detection is inventively demonstrated. With the exemplification of a direct influence of both features of the nanoprobe via the introduction of analytes, this study opens the feasibility of the analyte-perturbed felicitous equilibrium, which endows label-free methods with versatility and promising prospects. This design may evoke more biosensing strategies with the function of double-signal mutual verification.

Quantum dots as advanced nanomaterials for food quality and safety applications: A comprehensive review and future perspectives

The importance of food quality and safety lies in ensuring the best product quality to meet consumer demands and public health. Advanced technologies play a crucial role in minimizing the risk of foodborne illnesses, contamination, drug residue, and other potential hazards in food. Significant materials and technological advancements have been made throughout the food supply chain. Among them, quantum dots (QDs), as a class of advanced nanomaterials with unique physicochemical properties, are progressively demonstrating their value in the field of food quality and safety. This review aims to explore cutting-edge research on the different applications of QDs in food quality and safety, including encapsulation of bioactive compounds, detection of food analytes, food preservation and packaging, and intelligent food freshness indicators. Moreover, the modification strategies and potential toxicities of diverse QDs are outlined, which can affect performance and hinder applications in the food industry. The findings suggested that QDs are mainly used in analyte detection and active/intelligent food packaging. Various food analytes can be detected using QD-based sensors, including heavy metal ions, pesticides, antibiotics, microorganisms, additives, and functional components. Moreover, QD incorporation aided in improving the antibacterial and antioxidant activities of film/coatings, resulting in extended shelf life for packaged food. Finally, the perspectives and critical challenges for the productivity, toxicity, and practical application of QDs are also summarized. By consolidating these essential aspects into this review, the way for developing high-performance QD-based nanomaterials is presented for researchers and food technologists to better capitalize upon this technology in food applications.

Putting Hybrid Nanomaterials to Work for Biomedical Applications

Hybrid nanomaterials have found use in many biomedical applications. This article provides a comprehensive review of the principles, techniques, and recent advancements in the design and fabrication of hybrid nanomaterials for biomedicine. We begin with an introduction to the general concept of material hybridization, followed by a discussion of how this approach leads to materials with additional functionality and enhanced performance. We then highlight hybrid nanomaterials in the forms of nanostructures, nanocomposites, metal-organic frameworks, and biohybrids, including their fabrication methods. We also showcase the use of hybrid nanomaterials to advance biomedical engineering in the context of nanomedicine, regenerative medicine, diagnostics, theranostics, and biomanufacturing. Finally, we offer perspectives on challenges and opportunities.

Illuminating bunyavirus entry into host cells with fluorescence

Bunyavirales constitute the largest order of enveloped RNA viruses, many members of which cause severe diseases in humans and domestic animals. In recent decades, innovative fluorescence-based methods have paved the way to visualize and track single fluorescent bunyaviral particles in fixed and live cells. This technological breakthrough has enabled imaging of the early stages of infection and the quantification of every step in the bunyavirus cell entry process. Here, we describe the latest procedures for rendering bunyaviral particles fluorescent and discuss the advantages and disadvantages of each approach in light of the most recent advances in fluorescence detection and monitoring of bunyavirus entry. In this mini-review, we also illustrate how fluorescent viral particles are a powerful tool for deciphering the cellular entry process of bunyaviruses, the vast majority of which have not yet been analyzed.

One-Step Dual-Color Labeling of Viral Envelope and Intraviral Genome with Quantum Dots Harnessing Virus Infection

Labeling the genome and envelope of a virus with multicolor quantum dots (QDs) simultaneously enables real-time monitoring of viral uncoating and genome release, contributing to our understanding of virus infection mechanisms. However, current labeling techniques require genetic modification, which alters the virus's composition and infectivity. To address this, we utilized the CRISPR/Cas13 system and a bioorthogonal metabolic method to label the Japanese encephalitis virus (JEV) genome and envelopes with different-colored QDs in situ. This technique allows one-step two-color labeling of the viral envelope and intraviral genome with QDs harnessing virus infection. In combination with single-virus tracking, we visualized JEV uncoating and genome release in real time near the endoplasmic reticulum of live cells. This labeling strategy allows for real-time visualization of uncoating and genome release at the single-virus level, and it is expected to advance the study of other viral infection mechanisms.

Quantitative single-virus tracking for revealing the dynamics of SARS-CoV-2 fusion with plasma membrane

Viral envelope fusion with the host plasma membrane (PM) for genome release is a hallmark step in the life cycle of many enveloped viruses. This process is regulated by a complex network of biomolecules on the PM, but robust tools to precisely elucidate the dynamic mechanisms of virus-PM fusion events are still lacking. Here, we developed a quantitative single-virus tracking approach based on highly efficient dual-color labelling of viruses and batch trajectory analysis to achieve the spatiotemporal quantification of fusion events. This approach allows us to comprehensively analyze the membrane fusion mechanism utilized by pseudotyped severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) at the single-virus level and precisely elucidate how the relevant biomolecules synergistically regulate the fusion process. Our results revealed that SARS-CoV-2 may promote the formation of supersaturated clusters of cholesterol to facilitate the initiation of the membrane fusion process and accelerate the viral genome release.

Nanotechnology's frontier in combatting infectious and inflammatory diseases: prevention and treatment

Inflammation-associated diseases encompass a range of infectious diseases and non-infectious inflammatory diseases, which continuously pose one of the most serious threats to human health, attributed to factors such as the emergence of new pathogens, increasing drug resistance, changes in living environments and lifestyles, and the aging population. Despite rapid advancements in mechanistic research and drug development for these diseases, current treatments often have limited efficacy and notable side effects, necessitating the development of more effective and targeted anti-inflammatory therapies. In recent years, the rapid development of nanotechnology has provided crucial technological support for the prevention, treatment, and detection of inflammation-associated diseases. Various types of nanoparticles (NPs) play significant roles, serving as vaccine vehicles to enhance immunogenicity and as drug carriers to improve targeting and bioavailability. NPs can also directly combat pathogens and inflammation. In addition, nanotechnology has facilitated the development of biosensors for pathogen detection and imaging techniques for inflammatory diseases. This review categorizes and characterizes different types of NPs, summarizes their applications in the prevention, treatment, and detection of infectious and inflammatory diseases. It also discusses the challenges associated with clinical translation in this field and explores the latest developments and prospects. In conclusion, nanotechnology opens up new possibilities for the comprehensive management of infectious and inflammatory diseases.

Real-Time Dissection of the Exosome Pathway for Influenza Virus Infection

Exosomes play an important role in the spread of viral infections and immune escape. However, the exact ability and mechanisms by which exosomes produced during viral infections (vExos) infect host cells are still not fully understood. In this study, we developed a dual-color exosome labeling strategy that simultaneously labels the external and internal structures of exosomes with quantum dots to enable in situ monitoring of the transport process of vExos in live cells using the single-particle tracking technique. Our finding revealed that vExos contains the complete influenza A virus (IAV) genome and viral ribonucleoprotein complexes (vRNPs) proteins but lacks viral envelope proteins. Notably, these vExos have the ability to infect cells and produce progeny viruses. We also found that vExos are transported in three stages, slow-fast-slow, and move to the perinuclear region via microfilaments and microtubules. About 30% of internalized vExos shed the external membrane and release the internal vRNPs into the cytoplasm by fusion with endolysosomes. This study suggested that vExos plays a supporting role in IAV infection by assisting with IAV propagation in a virus-independent manner. It emphasizes the need to consider the infectious potential of vExos and draws attention to the potential risk of exosomes produced by viral infections.

Living virus-based nanohybrids for biomedical applications

Living viruses characterized by distinctive biological functions including specific targeting, gene invasion, immune modulation, and so forth have been receiving intensive attention from researchers worldwide owing to their promising potential for producing numerous theranostic modalities against diverse pathological conditions. Nevertheless, concerns during applications, such as rapid immune clearance, altering immune activation modes, insufficient gene transduction efficiency, and so forth, highlight the crucial issues of excessive therapeutic doses and the associated biosafety risks. To address these concerns, synthetic nanomaterials featuring unique physical/chemical properties are frequently exploited as efficient drug delivery vehicles or treatments in biomedical domains. By constant endeavor, researchers nowadays can create adaptable living virus-based nanohybrids (LVN) that not only overcome the limitations of virotherapy, but also combine the benefits of natural substances and nanotechnology to produce novel and promising therapeutic and diagnostic agents. In this review, we discuss the fundamental physiochemical properties of the viruses, and briefly outline the basic construction methodologies of LVN. We then emphasize their distinct diagnostic and therapeutic performances for various diseases. Furthermore, we survey the foreseeable challenges and future perspectives in this interdisciplinary area to offer insights. This article is categorized under: Biology-Inspired Nanomaterials > Protein and Virus-Based Structures Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Real-Time Imaging of Single Viral mRNA Translation in Live Cells Using CRISPR/dCas13

Translation is one of the many critical cellular activities regulated by viruses following host-cell invasion, and studies of viral mRNA translation kinetics and subcellular localization require techniques for the dynamic, real-time visualization of translation. However, conventional tools for imaging mRNA translation often require coding region modifications that may affect native translation. Here, we achieve dynamic imaging of translation with a tool that labels target mRNAs with unmodified coding regions using a CRISPR/dCas13 system with specific complementary paired guide RNAs. This system enables a real-time dynamic visualization of the translation process and is a promising tool for further investigations of the mechanisms of translation.

Controllable Regulation of Ag2 S Quantum-Dot-Mediated Protein Nanoassemblies for Imaging-Guided Synergistic PDT/PTT/Chemotherapy against Hypoxic Tumor

The combination of phototherapy and chemotherapy holds great potential for cancer treatment, while hypoxia in tumor as well as unexpected drug release largely restricts anticancer therapy. Inspired by the natural intelligence, herein, for the first time, a "bottom-up" protein self-assembly strategy mediated by near-infrared (NIR) quantum dots (QDs) with multicharged electrostatic interactions is presented to develop a tumor microenvironment (TME)-responsive theranostic nanoplatform for imaging-guided synergistic photodynamic therapy (PDT)/photothermal therapy (PTT)/chemotherapy. Catalase (CAT) possesses diverse surface charge distribution under different pH conditions. After modification by chlorin e6 (Ce6), the formulated CAT-Ce6 with patchy negative charges can be assembled with NIR Ag2 S QDs by regulating their electrostatic interactions, allowing for effective incorporation of specific anticancer drug oxaliplatin (Oxa). Such Ag2 S@CAT-Ce6@Oxa nanosystems are able to visualize nanoparticle (NP) accumulation to guide subsequent phototherapy, together with significant alleviation of tumor hypoxia to further enhance PDT. Moreover, the acidic TME triggers controllable disassembly through weakening the CAT surface charge to disrupt electrostatic interactions, allowing for sustained drug release. Both in vitro and in vivo results demonstrate remarkable inhibition of colorectal tumor growth with a synergistic effect. Overall, this multicharged electrostatic protein self-assembly strategy provides a versatile platform for realizing TME-specific theranostics with high efficiency and safety, promising for clinical translation.

Nanoprobe-based molecular imaging for tumor stratification

The responses of patients to tumor therapies vary due to tumor heterogeneity. Tumor stratification has been attracting increasing attention for accurately distinguishing between responders to treatment and non-responders. Nanoprobes with unique physical and chemical properties have great potential for patient stratification. This review begins by describing the features and design principles of nanoprobes that can visualize specific cell types and biomarkers and release inflammatory factors during or before tumor treatment. Then, we focus on the recent advancements in using nanoprobes to stratify various therapeutic modalities, including chemotherapy, radiotherapy (RT), photothermal therapy (PTT), photodynamic therapy (PDT), chemodynamic therapy (CDT), ferroptosis, and immunotherapy. The main challenges and perspectives of nanoprobes in cancer stratification are also discussed to facilitate probe development and clinical applications.

CRISPR/Cas-Based Techniques for Live-Cell Imaging and Bioanalysis

CRISPR/Cas systems have found widespread applications in gene editing due to their high accuracy, high programmability, ease of use, and affordability. Benefiting from the cleavage properties (trans- or cis-) of Cas enzymes, the scope of CRISPR/Cas systems has expanded beyond gene editing and they have been utilized in various fields, particularly in live-cell imaging and bioanalysis. In this review, we summarize some fundamental working mechanisms and concepts of the CRISPR/Cas systems, describe the recent advances and design principles of CRISPR/Cas mediated techniques employed in live-cell imaging and bioanalysis, highlight the main applications in the imaging and biosensing of a wide range of molecular targets, and discuss the challenges and prospects of CRISPR/Cas systems in live-cell imaging and biosensing. By illustrating the imaging and bio-sensing processes, we hope this review will guide the best use of the CRISPR/Cas in imaging and quantifying biological and clinical elements and inspire new ideas for better tool design in live-cell imaging and bioanalysis.

Biosynthesis of Quantum Dots and Their Therapeutic Applications in the Diagnosis and Treatment of Cancer and SARS-CoV-2

Quantum dots (QDs) are semiconductor materials that range from 2 nm to 10 nm. These nanomaterials (NMs) are smaller and have more unique properties compared to conventional nanoparticles (NPs). One of the unique properties of QDs is their special optoelectronic properties, making it possible to apply these NMs in bioimaging. Different size and shape QDs, which are used in various fields such as bioimaging, biosensing, cancer therapy, and drug delivery, have so far been produced by chemical methods. However, chemical synthesis provides expensive routes and causes serious environmental and health issues. Therefore, various biological systems such as bacteria, fungi, yeasts, algae, and plants are considered as potent eco-friendly green nanofactories for the biosynthesis of QDs, which are both economic and environmentally safe. The review aims to provide a descriptive overview of the various microbial agents for the synthesis of QDs and their biomedical applications for the diagnosis and treatment of cancer and SARS-CoV-2.

Exploring the multifunctional roles of quantum dots for unlocking the future of biology and medicine

With recent advancements in nanomedicines and their associated research with biological fields, their translation into clinically-applicable products is still below promises. Quantum dots (QDs) have received immense research attention and investment in the four decades since their discovery. We explored the extensive biomedical applications of QDs, viz. Bio-imaging, drug research, drug delivery, immune assays, biosensors, gene therapy, diagnostics, their toxic effects, and bio-compatibility. We unravelled the possibility of using emerging data-driven methodologies (bigdata, artificial intelligence, machine learning, high-throughput experimentation, computational automation) as excellent sources for time, space, and complexity optimization. We also discussed ongoing clinical trials, related challenges, and the technical aspects that should be considered to improve the clinical fate of QDs and promising future research directions.

Nanoparticle Spikes Enhance Cellular Uptake via Regulating Myosin IIA Recruitment

Spike-like nanostructures are omnipresent in natural and artificial systems. Although biorecognition of nanostructures to cellular receptors has been indicated as the primary factor for virus infection pathways, how the spiky morphology of DNA-modified nanoparticles affects their cellular uptake and intracellular fate remains to be explored. Here, we design dually emissive gold nanoparticles with varied spikiness (from 0 to 2) to probe the interactions of spiky nanoparticles with cells. We discovered that nanospikes at the nanoparticle regulated myosin IIA recruitment at the cell membrane during cellular uptake, thereby enhancing cellular uptake efficiency, as revealed by dual-modality (plasmonic and fluorescence) imaging. Furthermore, the spiky nanoparticles also exhibited facilitated endocytosis dynamics, as revealed by real-time dark-field microscopy (DFM) imaging and colorimetry-based classification algorithms. These findings highlight the crucial role of the spiky morphology in regulating the intracellular fate of nanoparticles, which may shed light on engineering theranostic nanocarriers.

Smart Nanomaterials in Cancer Theranostics: Challenges and Opportunities

Cancer is ranked as the second leading cause of death globally. Traditional cancer therapies including chemotherapy are flawed, with off-target and on-target toxicities on the normal cells, requiring newer strategies to improve cell selective targeting. The application of nanomaterial has been extensively studied and explored as chemical biology tools in cancer theranostics. It shows greater applications toward stability, biocompatibility, and increased cell permeability, resulting in precise targeting, and mitigating the shortcomings of traditional cancer therapies. The nanoplatform offers an exciting opportunity to gain targeting strategies and multifunctionality. The advent of nanotechnology, in particular the development of smart nanomaterials, has transformed cancer diagnosis and treatment. The large surface area of nanoparticles is enough to encapsulate many molecules and the ability to functionalize with various biosubstrates such as DNA, RNA, aptamers, and antibodies, which helps in theranostic action. Comparatively, biologically derived nanomaterials perceive advantages over the nanomaterials produced by conventional methods in terms of economy, ease of production, and reduced toxicity. The present review summarizes various techniques in cancer theranostics and emphasizes the applications of smart nanomaterials (such as organic nanoparticles (NPs), inorganic NPs, and carbon-based NPs). We also critically discussed the advantages and challenges impeding their translation in cancer treatment and diagnostic applications. This review concludes that the use of smart nanomaterials could significantly improve cancer theranostics and will facilitate new dimensions for tumor detection and therapy.

Purified fluorescent nanohybrids based on quantum dot-HER2-antibody for breast tumor target imaging

Quantum dots (QDs) have been widely used for bioimaging in vivo because of their excellent optical properties. As part of the preparation process of QD-based nanohybrids, purification is an important step for minimizing contaminants and improving the quality of the product. In this work, we describe high-performance size exclusion chromatography (HPSEC) used to purify nanohybrids of CdSe/ZnS QDs and anti-human epidermal growth factor receptor 2 antibodies (QD-HER2-Ab). The unbound antibody and suspended agglomerates were removed from freshly prepared QD-HER2-Ab via HPSEC. Pure and homogeneous QD-HER2-Ab were then used as immunofluorescence target imaging bioprobes in vivo. The QD-HER2-Ab did not cause any obvious acute toxicity in mice one week after a single intravenous injection of 15 nmol/kg. The purified QD-HER2-Ab bioprobes showed high tumor targeting ability in a human breast tumor xenograft nude mouse model (24 h after injected) with the possibility of in vivo immunofluorescence tumor imaging. The immunofluorescence imaging background signal and acute toxicity in vivo were minimized because of the reduction of residual QDs. HPSEC-purified QD-HER2-Ab is an accurate and convenient tool for in vivo tumor target imaging and HER2 detection, thus providing a basis for the purification of other QD-based bioprobes.

Simultaneous labeling and multicolor fluorescence imaging of multiple immune cells on liver frozen section by polychromatic quantum dots below freezing points

A method for simultaneous labeling and multicolor fluorescence imaging of different hepatic immune cells below freezing point is established based on quantum dots. In the experiment, carbon quantum dots with emission wavelength of 435 nm, CdTe@CdS quantum dots at 542 nm and CdSe@ZnS quantum dots at 604 nm are synthesized respectively, it is found that when the mass fractions of KCl (as antifreeze) are 12 %, 14 %, and 12 %, respectively, the three quantum dot dispersion systems remain liquid state at -20 °C. After they are conjugated with the corresponding secondary antibodies, agarose gel electrophoresis, circular dichroism and capillary electrophoresis confirm the effectiveness of conjugation. By indirect immunofluorescence method, the above three quantum dot fluorescent probes are used to simultaneously and specifically target a variety of liver immune cells, and the multi-color simultaneous imaging of different liver immune cells is realized under the same excitation wavelength, it is found that hepatic macrophages are arranged radially in the liver, hepatic stellate cells present punctate distribution, and hepatic sinusoidal endothelial cells present circular distribution, which is consistent with the results of H&E staining and ultrathin section TEM. This study provides an important technical means for elucidating the structure and function of the liver.

In Vivo Precision Evaluation of Lymphatic Function by SWIR Luminescence Imaging with PbS Quantum Dots

Advancements in lymphography technology are essential for comprehensive investigation of the lymphatic system and its function. Here, a shortwave infrared (SWIR) luminescence imaging of lymphatic vessels is proposed in both normal and lymphatic dysfunction in rat models with PbS quantum dots (PbS Qdots). The lymphography with PbS Qdots can clearly and rapidly demonstrate the normal lymphatic morphology in both the tail and hind limb. More importantly, compared to ICG, SWIR luminescence imaging with PbS Qdots can easily identify the dominant lymphatic vessel and node with higher luminescence signal in rats. Moreover, lymphatic pump is identified as segment contracting sections with a size of ≈1 cm in rat by in vivo SWIR lymphograhy, which propose a direct feature for precise evaluation of lymphatic function. Notably, in vivo SWIR luminescence imaging with PbS Qdots also clearly deciphers the in vivo pattern of morphological and function recovery from lymphatic system in rat model. In summary, SWIR luminescence imaging with PbS Qdots can improve the lymphography and thus deepen the understanding of the morphology and structure of the lymphatic system as well as lymphatic function such as lymphatic pump, which will facilitate the diagnosis of lymphatic dysfunction in the future.

A fluorescent lateral flow immunoassay based on CdSe/CdS/ZnS quantum dots for sensitive detection of olaquindox in feedstuff

A portable fluorescence immunosensor based on the CdSe/CdS/ZnS quantum dots (QDs) with multiple-shell structure was fabricated for the precise quantification of olaquindox (OLA). The QDs labeled anti-OLA antibody used as bioprobe played an important role in the design and preparation of a lateral flow test strip. Due to the strong fluorescent intensity of QDs, the sensitivity is greatly improved. The quantitative results were obtained using a fluorescent strip scan reader within 8 min, and the calculated limit of detection for OLA at 0.12 µg/kg, which was 2.7 times more sensitive than that of the conventional colloidal gold-based strips method. Acceptable recovery of 85.0%-95.5% was obtained by the spiked samples. This newly established QDs-based strip immunoassay method is suitable for the on-site detection and rapid initial screening of OLA in swine feedstuff, and is potentially applied for the detection of other veterinary drugs to ensure food safety.

Molecularly Imprinted Polymer-Based Luminescent Chemosensors

Molecularly imprinted polymer (MIP)-based luminescent chemosensors combine the advantages of the highly specific molecular recognition of the imprinting sites and the high sensitivity with the luminescence detection. These advantages have drawn great attention during the past two decades. Luminescent molecularly imprinted polymers (luminescent MIPs) towards different targeted analytes are constructed with different strategies, such as the incorporation of luminescent functional monomers, physical entrapment, covalent attachment of luminescent signaling elements on the MIPs, and surface-imprinting polymerization on the luminescent nanomaterials. In this review, we will discuss the design strategies and sensing approaches of luminescent MIP-based chemosensors, as well as their selected applications in biosensing, bioimaging, food safety, and clinical diagnosis. The limitations and prospects for the future development of MIP-based luminescent chemosensors will also be discussed.

Single-virus tracking with quantum dots in live cells

Single-virus tracking (SVT) offers the opportunity to monitor the journey of individual viruses in real time and to explore the interactions between viral and cellular structures in live cells, which can assist in characterizing the complex infection process and revealing the associated dynamic mechanisms. However, the low brightness and poor photostability of conventional fluorescent tags (e.g., organic dyes and fluorescent proteins) greatly limit the development of the SVT technique, and challenges remain in performing multicolor SVT over long periods of time. Owing to the outstanding photostability, high brightness and narrow emission with tunable color range of quantum dots (QDs), QD-based SVT (QSVT) enables us to follow the fate of individual viruses interacting with different cellular structures at the single-virus level for milliseconds to hours, providing more accurate and detailed information regarding viral infection in live cells. So far, the QSVT technique has yielded spectacular achievements in uncovering the mechanisms associated with virus entry, trafficking and egress. Here, we provide a detailed protocol for QSVT implementation using the viruses that we have previously studied systematically as an example. The specific procedures for performing QSVT experiments in live cells are described, including virus preparation, the QD labeling strategies, imaging approaches, image processing and data analysis. The protocol takes 1-2 weeks from the preparation of viruses and cellular specimens to image acquisition, and 1 d for image processing and data analysis.

Surface decorated quantum dots: Synthesis, properties and role in herbal therapy

Quantum dots are the serendipitous outcome of materials research. It is the tiny carbonaceous nanoparticles with diameters ranging from 1 to 10 nm. This review is a brief discussion of the synthesis, properties, and biomedical applicability of quantum dots, especially in herbal therapy. As quantum dots are highly polar, they can be surface decorated with several kinds of polar functionalities, such as polymeric molecules, small functional molecules, and so on. The review also consists of the basic physical and optical properties of quantum dots and their excitation-dependent properties in the application section. We focus on therapeutics, where quantum dots are used as drugs or imaging probes. Nanoprobes for several diagnostics are quite new in the biomedical research domain. Quantum dot-based nanoprobes are in high demand due to their excellent fluorescence, non-bleaching nature, biocompatibility, anchoring feasibility for several analytes, and fast point-of-care sensibility. Lastly, we also included a discussion on quantum dot-based drug delivery as phytomedicine.

Dual ligand-capped gold nanoclusters for the smart detection of specific reactive oxygen species

Quantitative detection of different types of reactive oxygen species (ROS) is vital for understanding the crucial roles of them in biological processes. However, few researches achieved the detection of multiple types of ROS with one probe until now. Given this, we designed and prepared fluorescent gold nanoclusters capped by dual ligand bovine serum albumin and lysozyme (BSA-LYS-AuNCs), which could detect 3 specific types of ROS based on its different fluorescent responses to H₂O₂, •OH and ClO^-, respectively. The limit of detection (LOD) of H₂O₂, •OH, and ClO^- was as low as 0.82 μM, 0.45 μM, and 0.62 μM. Moreover, as an important ROS type, ClO^- was detected with high sensitivity and low LOD by BSA-LYS-AuNCs. It was also proved that the crosslinking of protein mainly contributed to the unique fluorescent characteristics of the probe exposing to ClO^-. Furthermore, the fluorescent probe achieved the smart detection of hROS (including •OH and ClO^-) and wROS (the form of H₂O₂) in the real sample, which could also been applied specifically to the detection of antioxidants, e.g. ascorbic acid. The gold nanoclusters developed have high potential for the smart detection of multiple ROS in the body fluid of organisms.

Current progress of nanomedicine for prostate cancer diagnosis and treatment

Prostate cancer (PCa) is the most common new cancer case and the second most fatal malignancy in men. Surgery, endocrine therapy, radiotherapy and chemotherapy are the main clinical treatment options for PCa. However, most prostate cancers can develop into castration-resistant prostate cancer (CRPC), and due to the invasiveness of prostate cancer cells, they become resistant to different treatments and activate tumor-promoting signaling pathways, thereby inducing chemoresistance, radioresistance, ADT resistance, and immune resistance. Nanotechnology, which can combine treatment with diagnostic imaging tools, is emerging as a promising treatment modality in prostate cancer therapy. Nanoparticles can not only promote their accumulation at the pathological site through passive targeting techniques for enhanced permeability and retention (EPR), but also provide additional advantages for active targeting using different ligands. This property results in a reduced drug dose to achieve the desired effect, a longer duration of action within the tumor and fewer side effects on healthy tissues. In addition, nanotechnology can create good synergy with radiotherapy, chemotherapy, thermotherapy, photodynamic therapy and gene therapy to enhance their therapeutic effects with greater scope, and reduce the resistance of prostate cancer. In this article, we intend to review and discuss the latest technologies regarding the use of nanomaterials as therapeutic and diagnostic tools for prostate cancer.

Manipulating Reaction Intermediates to Aqueous-Phase ZnSe Magic-Size Clusters and Quantum Dots at Room Temperature

It is not resolved which model describes better the aqueous-phase nucleation and growth of semiconductor quantum dots (QDs), the classical one-step one or the nonclassical multi-step one. Here, we design a room-temperature reaction to trap reaction intermediates in the prenucleation stage of ZnSe QDs (as a model system). We show that the trapped intermediate can transform to magic-size clusters (MSCs) via intra-molecular reorganization and can fragment to enable the growth of QDs. The MSCs exhibit a sharp optical absorption peaking at 299 nm, labelled MSC-299. The intermediate, the precursor compound (PC-299) of MSC-299, is optically transparent at 299 nm and to longer wavelengths. This intermediate forms in various Zn and Se reaction systems. The present study provides unambiguous evidence that the nonclassical and classical pathways are both necessary to explain the nucleation and growth of aqueous-phase QDs, with the former pathway favored more by high reaction concentrations.

In-site electrophoretic elution of excessive fluorescein isothiocyanate from fluorescent particles in gel for image analysis

去除荧光标记后残余荧光染料可以提高荧光颗粒检测的灵敏度、准确度和效率。该文发展了一种原位电泳洗脱(electrophoretic elution, EE)模型,用于在荧光标记后快速去除多余的荧光探针,实现荧光颗粒的灵敏检测。将牛血清蛋白(BSA)和磁珠(MBs)作为模式蛋白和微颗粒,混合孵育获得MBs-BSA,用异硫氰酸荧光素(FITC)对MBs-BSA标记,得到MBs-BSA_FITC复合物。将含有多余FITC的MBs-BSA_FITC溶液与低凝聚温度琼脂糖凝胶溶液按1:5的体积比混合,并将混合物凝胶和纯琼脂糖凝胶分段填充到电泳通道中。电泳过程中,利用颗粒尺寸与凝胶孔径的差异来保留MBs-BSA_FITC,同时将游离的FITC洗脱。经过30 min的电泳洗脱,通道内多余的FITC清除率达到97.6%,同时目标颗粒荧光信号保留了27.8%。成像系统曝光时间为1.35 s时,电泳洗脱将颗粒与背景的荧光信号比(P/B ratio, PBr)从1.08增加到12.2。CCD相机的曝光时间增加到2.35 s,可以将PBr提高到15.5,可进一步实现对微弱荧光亮点的高灵敏检测。该模型有以下优点:(1)能对颗粒表面非特异性吸附的FITC实现有效洗脱,提高了检测的特异性;(2)能够将97%以上的游离FITC清除;(3) 30 min内能够使凝胶内的背景荧光大幅降低,提高了PBr和检测灵敏度。因此,该方法具有在凝胶中进行基于磁珠/荧光颗粒点的免疫检测、在免疫电泳或凝胶电泳中对蛋白质/核酸条带进行荧光染色等领域的应用潜力。

Quantum Dots with a Compact Amphiphilic Zwitterionic Coating

Generally speaking, it is difficult to keep nanomaterials encapsulated in amphiphilic polymers like octylamine-grafted poly(acrylic acid) (OPA) compact in coating-layer, with a small hydrodynamic size. Here, we prepared stable hydrophilic quantum dots (QDs) via encapsulation in ∼3 nm-long amphiphilic and zwitterionic (AZ) molecules. After encapsulation with AZ molecules, the coated QDs are only 2.1 nm thicker in coating, instead of 5.4 nm with OPA. Meanwhile, the hydrodynamic sizes of CdSe/CdS, ZnCdSeS, ZnCdSe/ZnS, and CdSe/ZnS QDs encapsulated in AZ molecules (AZ-QDs) are less than 15 nm, and 6-7 nm smaller than those of QDs in OPA (OPA-QDs). Notably, both extracellular and intracellular nonspecific binding of AZ-QDs is approximately 100-folds lower than that of OPA-QDs.

Quantum Dots Tracking Endocytosis and Transport of Proteins Displayed by Mammalian Cells

Mammalian cell display technology uses eukaryotic protein expression system to display proteins on cell surfaces and has become an important method in biological research. Although mammalian cell display technology has many advantages and development potential, certain attributes of the displayed protein remain uncharacterized, such as whether the displayed proteins re-enter the cell and how displayed proteins move into the cell. Here, we present the endocytosis mechanism, motility behavior, and transport kinetics of displayed proteins determined using HaloTag as the displayed protein and quantum dot-based single-particle tracking. The displayed protein enters the cell through clathrin-mediated endocytosis and is transported through the cell in three stages, which is dependent on microfilaments and microtubules. The dynamic information obtained in this study provides answers to questions about endocytosis and postendocytosis transport of displayed proteins and, therefore, is expected to facilitate the development of surface display technology.

Imaging of Hepatitis B Virus Nucleic Acids: Current Advances and Challenges

Hepatitis B virus infections are the main reason for hepatocellular carcinoma development. Current treatment reduces the viral load but rarely leads to virus elimination. Despite its medical importance, little is known about infection dynamics on the cellular level not at least due to technical obstacles. Regardless of infections leading to extreme viral loads, which may reach 10¹⁰ virions per mL serum, hepatitis B viruses are of low abundance and productivity in individual cells. Imaging of the infections in cells is thus a particular challenge especially for cccDNA that exists only in a few copies. The review describes the significance of microscopical approaches on genome and transcript detection for understanding hepatitis B virus infections, implications for understanding treatment outcomes, and recent microscopical approaches, which have not been applied in HBV research.

Single-Particle Tracking Reveals the Interplay between HIV-1 Reverse Transcription and Uncoating

Reverse transcription uses the reverse transcriptase enzyme to synthesize deoxyribonucleic acid (DNA) from a ribonucleic acid (RNA) template. This plays an essential role in viral replication. There are still, however, many unknown facts regarding the timing and dynamic processes involved in this life stage. Here, three types of dual-fluorescence human immunodeficiency virus type-1 (HIV-1) particles were constructed with high infectivity, and the sequential process of reverse transcription was observed by real-time imaging of a single HIV-1 particle. Viral uncoating occurred at 60-120 min post infection. Subsequently, at 120-180 min post infection, the viral genome was separated into two parts and reverse-transcribed to generate a DNA product. Nevirapine (NVP), a reverse transcriptase inhibitor, can delay the dynamic process. This study revealed a delicate, sequential, and complex relationship between uncoating and reverse transcription, which may facilitate the development of antiviral drugs.

A highly selective and sensitive CdS fluorescent quantum dot for the simultaneous detection of multiple pesticides

We presented one-pot prepared CdS fluorescent quantum dots (QDs) which can sensitively and selectively detect three different organic pesticides.