Progression of respiratory syncytial virus infection monitored by fluorescent quantum dot probes

Lipid-mediated biosynthetic labeling strategy for in vivo dynamic tracing of avian influenza virus infection

Monitoring the infection behavior of avian influenza viruses is crucial for understanding viral pathogenesis and preventing its epidemics among people. A number of viral labeling methods have been utilized for tracking viral infection process, but most of them are laborious or decreasing viral activity. Herein we explored a lipid biosynthetic labeling strategy for dynamical tracking the infection of H5N1 pseudotype virus (H5N1p) in host. Biotinylated lipids (biotinyl Cap-PE) were successfully incorporated into viral envelope when it underwent budding process by taking advantage of host cell-derived lipid metabolism. Biotin-H5N1p virus was effectively in situ-labeled with streptavidin-modified near-infrared quantum dots (NIR SA-QDs) using streptavidin-biotin conjugation with well-preserved virus activities. Dual-labeled imaging obviously shows that H5N1p viruses are primarily taken up in host cells via clathrin-mediated endocytosis. In animal models, Virus-conjugated NIR QDs displayed extraordinary photoluminescence, superior stability, and tissue penetration in lung, allowing us to long-term monitor respiratory viral infection in a noninvasive manner. Importantly, the co-localization of viral hemagglutinin protein and QDs in infected lung further conformed the dynamic infection process of virus in vivo. Hence, this in situ QD-labeling strategy based on cell natural biosynthesis provides a brand-new and reliable tool for noninvasion visualizing viral infection in body in a real-time manner.

Advances and Challenges of Fluorescent Nanomaterials for Synthesis and Biomedical Applications

With the rapid development of nanotechnology, new types of fluorescent nanomaterials (FNMs) have been springing up in the past two decades. The nanometer scale endows FNMs with unique optical properties which play a critical role in their applications in bioimaging and fluorescence-dependent detections. However, since low selectivity as well as low photoluminescence efficiency of fluorescent nanomaterials hinders their applications in imaging and detection to some extent, scientists are still in search of synthesizing new FNMs with better properties. In this review, a variety of fluorescent nanoparticles are summarized including semiconductor quantum dots, carbon dots, carbon nanoparticles, carbon nanotubes, graphene-based nanomaterials, noble metal nanoparticles, silica nanoparticles, phosphors and organic frameworks. We highlight the recent advances of the latest developments in the synthesis of FNMs and their applications in the biomedical field in recent years. Furthermore, the main theories, methods, and limitations of the synthesis and applications of FNMs have been reviewed and discussed. In addition, challenges in synthesis and biomedical applications are systematically summarized as well. The future directions and perspectives of FNMs in clinical applications are also presented.

Nanoscience and quantum science-led biocidal and antiviral strategies

The severe acute respiratory syndrome coronavirus (SARS-CoV-2) caused the COVID-19 pandemic. According to the World Health Organization, this pandemic continues to be a serious threat to public health due to the worldwide spread of variants and their higher rate of transmissibility. A range of measures are necessary to slow the pandemic and save lives, which include constant evaluation and the careful adjustment of public-health responses augmented by medical treatments, vaccines and protective gear. It is hypothesized that nanostructured particulates underpinned by nanoscience and quantum science yield high-performing antiviral strategies, which can be applied in preventive, diagnostic, and therapeutic applications such as face masks, respirators, COVID test kits, vaccines, and drugs. This review is aimed at providing comprehensive and cohesive perspectives on various nanostructures that are suited to intensifying and amplifying the effectiveness of antiviral strategies. Growing scientific literature over the past eighteen months indicates that quantum dots, iron oxide, silicon oxide, polymeric and metallic nanoparticles have been employed in COVID-19 diagnostic assays, vaccines, and personal protective equipment (PPE). Quantum dots have displayed their suitability as more sensitive imaging probes in diagnostics and prognostics, and as controlled drug-release carriers that target the virus. Nanoscience and quantum science have assisted the design of advanced vaccine delivery since nanostructured materials are suited for antigen delivery, as mimics of viral structures and as adjuvants. Furthermore, the quantum science- and nanoscience-supported tailored functionalization of nanostructured materials offers insight and pathways to deal with future pandemics. This review seeks to illustrate several examples, and to explain the underpinning quantum science and nanoscience phenomena, which include wave functions, electrostatic interactions, van der Waals forces, thermal and electrodynamic fluctuations, dispersion forces, local field-enhancement effects, and the generation of reactive oxygen species (ROS). This review discusses how nanostructured materials are helpful in the detection, prevention, and treatment of the SARS-CoV-2 infection, other known viral infection diseases, and future pandemics.

Nanotechnology-based approaches for emerging and re-emerging viruses: Special emphasis on COVID-19

In recent decades, the major concern of emerging and re-emerging viral diseases has become an increasingly important area of public health concern, and it is of significance to anticipate future pandemic that would inevitably threaten human lives. The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a newly emerged virus that causes mild to severe pneumonia. Coronavirus disease (COVID-19) became a very much concerned issue worldwide after its super-spread across the globe and emerging viral diseases have not got specific and reliable diagnostic and treatments. As the COVID-19 pandemic brings about a massive life-loss across the globe, there is an unmet need to discover a promising and typically effective diagnosis and treatment to prevent super-spreading and mortality from being decreased or even eliminated. This study was carried out to overview nanotechnology-based diagnostic and treatment approaches for emerging and re-emerging viruses with the current treatment of the disease and shed light on nanotechnology's remarkable potential to provide more effective treatment and prevention to a special focus on recently emerged coronavirus.

Recent advances in the detection of respiratory virus infection in humans

Respiratory tract viral infection caused by viruses or bacteria is one of the most common diseases in human worldwide, while those caused by emerging viruses, such as the novel coronavirus, 2019‐nCoV that caused the pneumonia outbreak in Wuhan, China most recently, have posed great threats to global public health. Identification of the causative viral pathogens of respiratory tract viral infections is important to select an appropriate treatment, save people's lives, stop the epidemics, and avoid unnecessary use of antibiotics. Conventional diagnostic tests, such as the assays for rapid detection of antiviral antibodies or viral antigens, are widely used in many clinical laboratories. With the development of modern technologies, new diagnostic strategies, including multiplex nucleic acid amplification and microarray‐based assays, are emerging. This review summarizes currently available and novel emerging diagnostic methods for the detection of common respiratory viruses, such as influenza virus, human respiratory syncytial virus, coronavirus, human adenovirus, and human rhinovirus. Multiplex assays for simultaneous detection of multiple respiratory viruses are also described. It is anticipated that such data will assist researchers and clinicians to develop appropriate diagnostic strategies for timely and effective detection of respiratory virus infections.

Respiratory tract viral infection including 2019‐nCoV poses great threats worldwide. Currently available and novel emerging diagnostic methods are summarized for several common respiratory viruses, including influenza virus, human respiratory syncytial virus, coronavirus, human adenovirus and human rhinovirus. Multiplex assays for simultaneous detection of multiple respiratory viruses are also described. This review is aimed to assist researchers and clinicians to develop timely and effective diagnostic strategies to detect respiratory virus infections.

Nano-based approach to combat emerging viral (NIPAH virus) infection

Emergence of new virus and their heterogeneity are growing at an alarming rate. Sudden outburst of Nipah virus (NiV) has raised serious question about their instant management using conventional medication and diagnostic measures. A coherent strategy with versatility and comprehensive perspective to confront the rising distress could perhaps be effectuated by implementation of nanotechnology. But in concurrent to resourceful and precise execution of nano-based medication, there is an ultimate need of concrete understanding of the NIV pathogenesis. Moreover, to amplify the effectiveness of nano-based approach in a conquest against NiV, a list of developed nanosystem with antiviral activity is also a prerequisite. Therefore the present review provides a meticulous cognizance of cellular and molecular pathogenesis of NiV. Conventional as well several nano-based diagnosis experimentations against viruses have been discussed. Lastly, potential efficacy of different forms of nano-based systems as convenient means to shield mankind against NiV has also been introduced.

An ultrasensitive and simple assay for the Hepatitis C virus using a reduced graphene oxide-assisted hybridization chain reaction

Hepatitis C virus (HCV) is a major cause of chronic liver disease, which affects 2–3% of the world population.

Detection Methodologies for Pathogen and Toxins: A Review

Pathogen and toxin-contaminated foods and beverages are a major source of illnesses, even death, and have a significant economic impact worldwide. Human health is always under a potential threat, including from biological warfare, due to these dangerous pathogens. The agricultural and food production chain consists of many steps such as harvesting, handling, processing, packaging, storage, distribution, preparation, and consumption. Each step is susceptible to threats of environmental contamination or failure to safeguard the processes. The production process can be controlled in the food and agricultural sector, where smart sensors can play a major role, ensuring greater food quality and safety by low cost, fast, reliable, and profitable methods of detection. Techniques for the detection of pathogens and toxins may vary in cost, size, and specificity, speed of response, sensitivity, and precision. Smart sensors can detect, analyse and quantify at molecular levels contents of different biological origin and ensure quality of foods against spiking with pesticides, fertilizers, dioxin, modified organisms, anti-nutrients, allergens, drugs and so on. This paper reviews different methodologies to detect pathogens and toxins in foods and beverages.

DNA-AuNP networks on cell membranes as a protective barrier to inhibit viral attachment, entry and budding

Viral infections have caused numerous diseases and deaths worldwide. Due to the emergence of new viruses and frequent virus variation, conventional antiviral strategies that directly target viral or cellular proteins are limited because of the specificity, drug resistance and rapid clearance from the human body. Therefore, developing safe and potent antiviral agents with activity against viral infection at multiple points in the viral life cycle remains a major challenge. In this report, we propose a new modality to inhibit viral infection by fabricating DNA conjugated gold nanoparticle (DNA-AuNP) networks on cell membranes as a protective barrier. The DNA-AuNPs networks were found, via a plaque formation assay and viral titers, to have potent antiviral ability and protect host cells from human respiratory syncytial virus (RSV). Confocal immunofluorescence image analysis showed 80 ± 3.8% of viral attachment, 91.1 ± 0.9% of viral entry and 87.9 ± 2.8% of viral budding were inhibited by the DNA-AuNP networks, which were further confirmed by real-time fluorescence imaging of the RSV infection process. The antiviral activity of the networks may be attributed to steric effects, the disruption of membrane glycoproteins and limited fusion of cell membrane bilayers, all of which play important roles in viral infection. Therefore, our results suggest that the DNA-AuNP networks have not only prophylactic effects to inhibit virus attachment and entry, but also therapeutic effects to inhibit viral budding and cell-to-cell spread. More importantly, this proof-of-principle study provides a pathway for the development of a universal, broad-spectrum antiviral therapy.

Quantum dot induced cellular perturbations involving varying toxicity pathways

Quantum dots (QD) with varying surface chemistry can have an impact on cellular uptake and a range of indicators for cell perturbation.

Noninvasive visualization of respiratory viral infection using bioorthogonal conjugated near-infrared-emitting quantum dots

Highly pathogenic avian influenza A viruses are emerging pandemic threats in human beings. Monitoring the in vivo dynamics of avian influenza viruses is extremely important for understanding viral pathogenesis and developing antiviral drugs. Although a number of technologies have been applied for tracking viral infection in vivo, most of them are laborious with unsatisfactory detection sensitivity. Herein we labeled avian influenza H5N1 pseudotype virus (H5N1p) with near-infrared (NIR)-emitting QDs by bioorthogonal chemistry. The conjugation of QDs onto H5N1p was highly efficient with superior stability both in vitro and in vivo. Furthermore, QD-labeled H5N1p (QD-H5N1p) demonstrated bright and sustained fluorescent signals in mouse lung tissues, allowing us to visualize respiratory viral infection in a noninvasive and real-time manner. The fluorescence signals of QD-H5N1p in lung were correlated with the severity of virus infection and significantly attenuated by antiviral agents, such as oseltamivir carboxylate and mouse antiserum against H5N1p. The biodistribution of QD-H5N1p in lungs and other organs could be easily quantified by measuring fluorescent signals and cadmium concentration of virus-conjugated QDs in tissues. Hence, virus labeling with NIR QDs provides a simple, reliable, and quantitative strategy for tracking respiratory viral infection and for antiviral drug screening.

Recent advances in diagnosis, prevention, and treatment of human respiratory syncytial virus

Human respiratory syncytial virus (RSV) is a common cause of respiratory infection in infants and the elderly, leading to significant morbidity and mortality. The interdisciplinary fields, especially biotechnology and nanotechnology, have facilitated the development of modern detection systems for RSV. Many anti-RSV compounds like fusion inhibitors and RNAi molecules have been successful in laboratory and clinical trials. But, currently, there are no effective drugs for RSV infection even after decades of research. Effective diagnosis can result in effective treatment, but the progress in both of these facets must be concurrent. The development in prevention and treatment measures for RSV is at appreciable pace, but the implementation into clinical practice still seems a challenge. This review attempts to present the promising diverse research approaches and advancements in the area of diagnosis, prevention, and treatment that contribute to RSV management.

Recent advances in optical biosensors for environmental monitoring and early warning

The growing number of pollutants requires the development of innovative analytical devices that are precise, sensitive, specific, rapid, and easy-to-use to meet the increasing demand for legislative actions on environmental pollution control and early warning. Optical biosensors, as a powerful alternative to conventional analytical techniques, enable the highly sensitive, real-time, and high-frequency monitoring of pollutants without extensive sample preparation. This article reviews important advances in functional biorecognition materials (e.g., enzymes, aptamers, DNAzymes, antibodies and whole cells) that facilitate the increasing application of optical biosensors. This work further examines the significant improvements in optical biosensor instrumentation and their environmental applications. Innovative developments of optical biosensors for environmental pollution control and early warning are also discussed.

Detecting respiratory syncytial virus using nanoparticle-amplified immuno-PCR

Early-stage detection is essential for effective treatment of pediatric virus infections. In traditional -immuno-PCR, a single antibody recognition event is associated with one to three DNA tags, which are subsequently amplified by PCR. In this protocol, we describe a nanoparticle-amplified immuno-PCR assay that combines antibody recognition of traditional ELISA with a 50-fold nanoparticle valence amplification step followed by amplification by traditional PCR. The assay detects a respiratory syncytial virus (RSV) surface fusion protein using a Synagis antibody bound to a 15 nm gold nanoparticle co-functionalized with thiolated DNA complementary to a hybridized 76-base Tag DNA. The Tag DNA to Synagis ratio is 50 to 1. The presence of virus particles triggers the formation of a "sandwich" complex comprised of the gold nanoparticle construct, virus, and a 1 μm antibody-functionalized magnetic particle used for extraction. Virus-containing complexes are isolated using a magnet, DNA tags released by heating to 95 °C, and detected via real-time PCR. The limit of detection of the nanoparticle-amplified immuno-PCR assay was compared to traditional ELISA and traditional RT-PCR using RSV-infected HEp-2 cell extracts. Nanoparticle-amplified immuno-PCR showed a ∼4,000-fold improvement in the limit of detection compared to ELISA and a fourfold improvement in the limit of detection compared to traditional RT-PCR. Nanoparticle-amplified immuno-PCR offers a viable platform for the development of an early-stage diagnostics requiring an exceptionally low limit of detection.

Quantum dots: synthesis, bioapplications, and toxicity

This review introduces quantum dots (QDs) and explores their properties, synthesis, applications, delivery systems in biology, and their toxicity. QDs are one of the first nanotechnologies to be integrated with the biological sciences and are widely anticipated to eventually find application in a number of commercial consumer and clinical products. They exhibit unique luminescence characteristics and electronic properties such as wide and continuous absorption spectra, narrow emission spectra, and high light stability. The application of QDs, as a new technology for biosystems, has been typically studied on mammalian cells. Due to the small structures of QDs, some physical properties such as optical and electron transport characteristics are quite different from those of the bulk materials.

Hybrid nanoparticles for detection and treatment of cancer

There is currently considerable effort to incorporate both diagnostic and therapeutic functions into a single nanoscale system for the more effective treatment of cancer. Nanoparticles have great potential to achieve such dual functions, particularly if more than one type of nanostructure can be incorporated in a nanoassembly, referred to in this review as a hybrid nanoparticle. Here we review recent developments in the synthesis and evaluation of such hybrid nanoparticles based on two design strategies (barge vs. tanker), in which liposomal, micellar, porous silica, polymeric, viral, noble metal, and nanotube systems are incorporated either within (barge) or at the surface of (tanker) a nanoparticle. We highlight the design factors that should be considered to obtain effective nanodevices for cancer detection and treatment.

Quantum dot-aptamer nanoprobes for recognizing and labeling influenza A virus particles

The fluorescence labeling of viruses is a useful technology for virus detection and imaging. By combining the excellent fluorescence properties of quantum dots (QDs) with the high affinity and specificity of aptamers, we constructed a QD-aptamer probe. The aptamer A22, against the hemagglutinin of influenza A virus, was linked to QDs, producing the QD-A22 probe. Fluorescence imaging and transmission electron microscopy showed that the QD-A22 probe could specifically recognize and label influenza A virus particles. This QD labeling technique provides a new strategy for labeling virus particles for virus detection and imaging.

Biocompatible quantum dots for biological applications

Semiconductor quantum dots are quickly becoming a critical diagnostic tool for discerning cellular function at the molecular level. Their high brightness, long-lasting, size-tunable, and narrow luminescence set them apart from conventional fluorescence dyes. Quantum dots are being developed for a variety of biologically oriented applications, including fluorescent assays for drug discovery, disease detection, single protein tracking, and intracellular reporting. This review introduces the science behind quantum dots and describes how they are made biologically compatible. Several applications are also included, illustrating strategies toward target specificity, and are followed by a discussion on the limitations of quantum dot approaches. The article is concluded with a look at the future direction of quantum dots.

Detecting RNA viruses in living mammalian cells by fluorescence microscopy

Traditional methods that rely on viral isolation and culture techniques continue to be the gold standards used for detection of infectious viral particles. However, new techniques that rely on visualization of live cells can shed light on understanding virus-host interaction for early stage detection and potential drug discovery. Live-cell imaging techniques that incorporate fluorescent probes into viral components provide opportunities for understanding mRNA expression, interaction, and virus movement and localization. Other viral replication events inside a host cell can be exploited for non-invasive detection, such as single-virus tracking, which does not inhibit viral infectivity or cellular function. This review highlights some of the recent advances made using these novel approaches for visualization of viral entry and replication in live cells.

Detection of respiratory syncytial virus using nanoparticle amplified immuno-polymerase chain reaction

In traditional immuno-polymerase chain reaction (immuno-PCR), a single antibody recognition event is associated with one to three DNA tags, which are subsequently amplified by PCR. Here we describe a nanoparticle-amplified immuno-PCR (NPA-IPCR) assay that combines antibody recognition of enzyme-linked immunosorbent assay (ELISA) with a 50-fold nanoparticle valence amplification step prior to tag amplification by PCR. The assay detects a respiratory syncytial virus (RSV) surface protein using an antibody bound to a 15-nm gold nanoparticle cofunctionalized with thiolated DNA complementary to a hybridized 76-base tag DNA with a tag DNA/antibody ratio of 50:1. The presence of virus particles triggers the formation of a "sandwich" complex composed of the gold nanoparticle construct, virus, and an antibody-functionalized magnetic particle used for extraction. After extraction, DNA tags are released by heating to 95°C and detected via real-time PCR. The limit of detection of the assay was compared with ELISA and reversion transcription (RT) PCR using RSV-infected HEp-2 cell extracts. NPA-IPCR showed an approximately 4000-fold improvement in the limit of detection compared with ELISA and a 4-fold improvement compared with viral RNA extraction followed by traditional RT-PCR. NPA-IPCR offers a viable platform for the development of early-stage diagnostics requiring an exceptionally low limit of detection.

On Ultrasmall Nanocrystals

Ultrasmall nanocrystals are a growing sub-class of traditional nanocrystals that exhibit new properties at diameters typically below 2 nm. In this review, we define what constitutes an ultrasmall nanoparticle while distinguishing between ultrasmall and magic-size nanoparticles. After a brief overview of ultrasmall nanoparticles, including ultrasmall gold clusters, our recent work is presented covering the optical properties, structure, and application of ultrasmall CdSe nanocrystals. This unique material has potential application in solid state lighting due to its balanced white emission. This section is followed by a discussion on the blurring boundary between what can be considered a nanoparticle and a molecule.

Monitoring viral RNA in infected cells with LNA flow-FISH

We previously showed the feasibility of using locked nucleic acid (LNA) for flow cytometric-fluorescence in situ hybridization (LNA flow-FISH) detection of a target cellular mRNA. Here we demonstrate how the method can be used to monitor viral RNA in infected cells. We compared the results of the LNA flow-FISH with other methods of quantifying virus replication, including the use of an enhanced green fluorescent protein (EGFP) viral construct and quantitative reverse-transcription polymerase chain reaction. We found that an LNA probe complementary to Sindbis virus RNA is able to track the increase in viral RNA over time in early infection. In addition, this method is comparable to the EGFP construct in sensitivity, with both peaking around 3 h and at the same level of infected cells. Finally, we observed that the LNA flow-FISH method responds to the decrease in levels of viral RNA caused by antiviral medication. This technique represents a straightforward way to monitor viral infection in cells and is easily applicable to any virus.

Hairpin DNA-functionalized gold colloids for the imaging of mRNA in live cells

A strategy is presented for the live cell imaging of messenger RNA using hairpin DNA-functionalized gold nanoparticles (hAuNP). hAuNP improve upon technologies for studying RNA trafficking by their efficient internalization within live cells without transfection reagents, improved resistance to DNase degradation, low cytotoxicity, and the incorporation of hairpin DNA molecular beacons to confer high specificity and sensitivity to the target mRNA sequence. Furthermore, the targeted nanoparticle-beacon construct, once bound to the target mRNA sequence, remains hybridized to the target, enabling spatial and temporal studies of RNA trafficking and downstream analysis. Targeted hAuNP exhibited high specificity for glyceraldehyde 3-phosphate dehydrogenase (GADPH) mRNA in live normal HEp-2 cells and respiratory syncytial virus (RSV) mRNA in live RSV-infected HEp-2 cells with high target to background ratios. Multiplexed fluorescence imaging of distinct mRNAs in live cells and simultaneous imaging of mRNAs with immunofluorescently stained protein targets in fixed cells was enabled by appropriate selection of molecular beacon fluorophores. Pharmacologic analysis suggested that hAuNP were internalized within cells via membrane-nanoparticle interactions. hAuNP are a promising approach for the real-time analysis of mRNA transport and processing in live cells for elucidation of biological processes and disease pathogenesis.

Nanoparticle detection of respiratory infection

Respiratory viruses are a constant concern for all demographics. Examples include established viruses such as respiratory syncytial virus (RSV), the leading cause of respiratory infection in infants and young children, and emerging viruses such as severe acute respiratory syndrome (SARS), which reached near pandemic levels in 2003, or H1N1 (swine) influenza. Despite this prevalence, traditional methods of virus detection are typically labor intensive and require several days to successfully confirm infection. Recently, however, nanoparticle‐based detection strategies have been employed in an effort to develop detection assays that are both sensitive and expedient. Each of these platforms capitalizes on the unique properties of nanoparticles for the detection of respiratory viruses. In this article, several nanoparticle‐based scaffolds are discussed.Gold nanoparticles (AuNPs) have been functionalized with virus specific antibodies or oligonucleotides. In each of these constructs, AuNPs act as both an easily conjugated scaffolding system for biological molecules and a powerful fluorescence quencher. AuNPs have also been immobilized and used as electrochemical transducers. They efficiently serve as a conducting interface of electrocatalyic activity making them a powerful tool in this application. Quantum dots (QDs) posses unique fluorescence properties that have also been explored for their application to virus detection when combined with direct antibody conjugation or streptavidin‐biotin binding systems. QDs have an advantage over many traditional fluorophores because their fluorescence properties can be finely tuned and they are resistant to photobleaching. The development of these nanoparticle‐based detection strategies holds the potential to be a powerful method to quickly and easily confirm respiratory virus infection. WIREs Nanomed Nanobiotechnol 2010 2 277–290

This article is categorized under: 1

Diagnostic Tools > In Vitro Nanoparticle-Based Sensing

2

Therapeutic Approaches and Drug Discovery > Nanomedicine for Respiratory Disease

4-N-pyridin-2-yl-benzamide nanotubes compatible with mouse stem cell and oral delivery in Drosophila

p-aminobenzoic acid (PABA), a structural moiety of many commercial drugs, is self-assembled with linker alkyl side chains to form tubular nanostructures. The tubes exhibited fluorescence either intrinsic or from fluorescent molecules embedded in the wall during self-assembly. Uptake and inter-cellular delivery of the conjugated nanotubes in human cancer cells and in mouse embryonic stem cells were demonstrated by fluorescence imaging and flow cytometry. Biocompatibility, cytotoxicity and clearance were monitored both ex vivo in mouse multipotent embryonic stem cells and in vivo in adult Drosophila. Accumulation of nanotubes had no adverse effects and abnormalities on stem cell morphology and proliferation rate. A distinct distribution of two separate nanotubes in various internal organs of Drosophila interprets that accumulation of nanomaterials might be interdependent on the side chain modifications and physiological settings of cell or tissue types. Unlike carbon nanomaterials, exposure of PABA nanotubes does not produce any hazards including locomotion defects and mortality of adult flies. Despite differential uptake and clearance from multiple live tissues, the use of self-assembled nanotubes can add new dimensions and scope to the development of dual-purpose oral carriers for the fulfilment of many biological promises.

Nanobioimaging and sensing of infectious diseases

New methods to identify trace amount of infectious pathogens rapidly, accurately and with high sensitivity are in constant demand to prevent epidemics and loss of lives. Early detection of these pathogens to prevent, treat and contain the spread of infections is crucial. Therefore, there is a need and urgency for sensitive, specific, accurate, easy-to-use diagnostic tests. Versatile biofunctionalized engineered nanomaterials are proving to be promising in meeting these needs in diagnosing the pathogens in food, blood and clinical samples. The unique optical and magnetic properties of the nanoscale materials have been put to use for the diagnostics. In this review, we focus on the developments of the fluorescent nanoparticles, metallic nanostructures and superparamagnetic nanoparticles for bioimaging and detection of infectious microorganisms. The various nanodiagnostic assays developed to image, detect and capture infectious virus and bacteria in solutions, food or biological samples in vitro and in vivo are presented and their relevance to developing countries is discussed.

Real-time visualization of prion transport in single live cells using quantum dots

Prion diseases are fatal neurodegenerative disorders resulting from structural conversion of the cellular isoform of PrP(C) to the infectious scrapie isoform PrP(Sc). It is believed that such structural alteration may occur within the internalization pathway. However, there is no direct evidence to support this hypothesis. Employing quantum dots (QDs) as a probe, we have recorded a real-time movie demonstrating the process of prion internalization in a living cell for the first time. The entire internalization process can be divided into four discrete but connected stages. In addition, using methyl-beta-cyclodextrin to disrupt cell membrane cholesterol, we show that lipid rafts play an important role in locating cellular PrP(C) to the cell membrane and in initiating PrP(C) endocytosis.

Emerging molecular assays for detection and characterization of respiratory viruses

This article describes several emerging molecular assays that have potential applications in the diagnosis and monitoring of respiratory viral infections. These techniques include direct nucleic acid detection by quantum dots, loop-mediated isothermal amplification, multiplex ligation-dependent probe amplification, amplification using arbitrary primers, target-enriched multiplexing amplification, pyrosequencing, padlock probes, solid and suspension microarrays, and mass spectrometry. Several of these systems already are commercially available to provide multiplex amplification and high-throughput detection and identification of a panel of respiratory viral pathogens. Further validation and implementation of such emerging molecular assays in routine clinical virology services will enhance the rapid diagnosis of respiratory viral infections and improve patient care.

Quantum dot-based HIV capture and imaging in a microfluidic channel

Globally, over 33.2 million people who mostly live in developing countries with limited access to the appropriate medical care suffer from the human immunodeficiency virus (HIV) infection. We developed an on-chip HIV capture and imaging method using quantum dots (Qdots) from fingerprick volume (10 microl) of unprocessed HIV-infected patient whole blood in anti-gp120 antibody-immobilized microfluidic chip. Two-color Qdots (Qdot525 and Qdot655 streptavidin conjugates) were used to identify the captured HIV by simultaneous labeling the envelope gp120 glycoprotein and its high-mannose glycans. This dual-stain imaging technique using Qdots provides a new and effective tool for accurate identification of HIV particles from patient whole blood without any pre-processing. This on-chip HIV capture and imaging platform creates new avenues for point-of-care diagnostics and monitoring applications of infectious diseases.

Immune response induced by fluorescent nanocrystal quantum dots in vitro and in vivo

Fluorescent nanocrystal quantum dots (QDs) are widely used as novel tools in various biological fields including cellular biology, molecular biology, and even in basic and clinical medical fields, due to their far brighter photoemission and photostability. Although many amounts of biological studies, including in vivo experiments, were circumstantially investigated, there is no informative report that investigates whether the QDs affect the mammalian immune system. This study investigated the immune response and biological behavior of QDs in vitro and in vivo. The immune response to QDs by both lymphocytes and kinds of macrophages in vitro and in vivo was investigated. Co-culture of QDs with immune cells showed that apparently normal production of cytokines and chemokines in both mouse CD4+ lymphocytes and peritoneal F4/80+ macrophages (PM phi). In addition, the bionanocomplex of QDs with enhanced-green-fluorescent-protein (eGFP)-encoding nucleotides successfully induced the expression of eGFP protein by PM phi. However, direct injection of QD+nucleotides bionanocomplex aqueous solution into the peritoneal cavity of mice resulted in the inflammation with the infiltration of inflammatory cells into the peritoneal cavity. Furthermore, QD+nucleotides bionanocomplex (but not QD bionanocomplex without nucleotides), induced the production of both proinflammatory cytokines and chemokines by PM phi in vitro. These results indicated that QDs covered with nucleotides caused the peritoneal inflammation in vivo via activation of PM phi and probably nonimmune cells. Taken together, these data indicated that QDs affect the proliferation of immune cells, but not in immune response including cytokine production. We propose here that all nanotechnology researchers should confirm the biological responses of their nanoscale products, because the biological response against nanoscale products can be occurred by not only in immune cells but also other nonimmune cells.

Micro- and nanotechnology for viral detection

Since the identification of viruses at the start of the 20th century, detecting their presence has presented great challenges. In the past two decades, there has been significant progress in viral detection methods for clinical diagnosis and environmental monitoring. The earliest advances were in molecular biology and imaging techniques. Advances in microfabrication and nanotechnology have now begun to play an important role in viral detection, and improving the detection limit, operational simplicity, and cost-effectiveness of viral diagnostics. Here we provide an overview of recent advances, focusing especially on advances in simple, device-based approaches for viral detection.

Potential clinical applications of quantum dots

The use of luminescent colloidal quantum dots in biological investigations has increased dramatically over the past several years due to their unique size-dependent optical properties and recent advances in biofunctionalization. In this review, we describe the methods for generating high-quality nanocrystals and report on current and potential uses of these versatile materials. Numerous examples are provided in several key areas including cell labeling, biosensing, in vivo imaging, bimodal magnetic-luminescent imaging, and diagnostics. We also explore toxicity issues surrounding these materials and speculate about the future uses of quantum dots in a clinical setting.

Site-specific labeling of enveloped viruses with quantum dots for single virus tracking

This study reports a general method of labeling enveloped viruses with semiconductor quantum dots (QDs) for use in single virus trafficking studies. Retroviruses, including human immunodeficiency virus (HIV), could be successfully tagged with QDs through the membrane incorporation of a short acceptor peptide (AP) that is susceptible to site-specific biotinylation and attachment of streptavidin-conjugated QDs. It was found that this AP tag-based QD labeling had little effect on the viral infectivity and allowed for the study of the kinetics of the internalization of the recombinant lentivirus enveloped with vesicular stomatitis virus glycoprotein (VSVG) into the early endosomes. It also allows for the live cell imaging of the trafficking of labeled virus to the Rab5(+) endosomal compartments. This study further demonstrated by direct visualization of QD-labeled virus that VSVG-pseudotyped lentivirus enters cells independent of clatherin- and caveolin-pathways, while the entry of VSVG-pseudotyped retrovirus occurs via the clathrin pathway. The studies monitoring HIV particles using QD-labeling showed that we could detect single virions on the surface of target cells expressing either CD4/CCR5 or DC-SIGN. Further internalization studies of QD-HIV evidently showed that the clathrin pathway is the major route for DC-SIGN-mediated uptake of viruses. Taken together, our data demonstrate the potential of this QD-labeling for visualizing the dynamic interactions between viruses and target cell structures.

Virus assay using antibody-functionalized peptide nanotubes

Robust trace-level detection of viruses is crucial to meet urgent needs in fighting the spread of disease or detecting bioterrorism events. We report a new method for rapid and highly sensitive detection of viruses utilizing fluorescent antibody nanotubes. When viral pathogens were mixed with these antibody nanotubes, the nanotubes rapidly aggregated around the viruses to form a networking structure. Trace quantities of viruses such as herpes simplex virus type 2, adenovirus, vaccinia and influenza type B were detected on attomolar order by changes in fluorescence and light scattering intensities associated with aggregation of dye-loaded antibody nanotubes around viruses. High specificity of each antibody nanotube toward its targeted virus was demonstrated by quantifying concentrations of two different viruses in mixtures. This antibody nanotube assay detects targeted pathogens within 30 minutes after incubation with antibody nanotubes. This antibody nanotube assay could fill a pressing need to detect and quantify viruses both rapidly and sensitively.

Crossbar assembly of antibody-functionalized peptide nanotubes via biomimetic molecular recognition

Previously, a large scale assembly of nanowires in a parallel array configuration has been demonstrated, and one type of nanowire could interconnect two electrodes in the high-wire density. However, to assemble nanowires into practical logic-gate configurations in integrated circuits, we need more than the parallel assembly of nanowires. For example, when the assembling nanowires are monopolar semiconductors, logic gates such as AND, OR and NOR are to be assembled necessarily from two types of semiconducting nanowires, n-type and p-type, and some of these nanowires must cross perpendicularly to form a crossbar geometry for the logical operation. In this paper, the crossbar assembly of antibody-functionalized peptide nanotubes was demonstrated by a new biomimetic bottom-up technique. Molecular recognition between antigens and antibodies enabled two types of the antibody-functionalized bionanotubes to place them onto targeted locations on substrates, where their complementary antigens were patterned. When two rectangular pads of antigens, human IgG and mouse IgG, were patterned perpendicularly on an Au substrate by nanolithography and then the antihuman IgG nanotubes and the antimouse IgG nanotubes were incubated on this substrate in solution, these bionanotubes were attached onto corresponding locations to form the crossbar configuration.