Novel nanosensors for rapid analysis of telomerase activity

Electron-transfer quenching of nucleic acid-functionalized CdSe/ZnS quantum dots by doxorubicin: a versatile system for the optical detection of DNA, aptamer-substrate complexes and telomerase activity

The optical detection of DNA or the sensing of low-molecular-weight substrates or proteins by aptamer nucleic acids is a long term challenge in the design of biosensors. Similarly, the detection of the telomerase activity, a versatile biomarker of cancer cells, is important for rapid cancer diagnostics. We implement the luminescence quenching of the CdSe/ZnS quantum dots (QDs) as a versatile process to develop DNA sensors and aptasensors, and to design an analytical platform for the detection of telomerase activity. The formation of nucleic acid duplexes on QDs, or the assembly of aptamer-substrate complexes on the QDs (substrate=cocaine or thrombin) is accompanied by the intercalation of doxorubicin (DB) into the duplex domains of the resulting recognition complexes. The intercalated DB quenches the luminescence of the QDs, thus leading to the detection readout signal. Similarly, the telomerase-induced formation of the telomere chains on the QDs is followed by the hybridization of nucleic-acid units complementary to the telomere repeat units, and the intercalation of DB into the resulting duplex structure. The resulting luminescence quenching of the QDs provides an indicating signal for the activity of telomerase.

The assembly state between magnetic nanosensors and their targets orchestrates their magnetic relaxation response

The target-induced clustering of magnetic nanoparticles is typically used for the identification of clinically relevant targets and events. A decrease in the water proton transverse NMR relaxation time, or T(2), is observed upon clustering, allowing the sensitive and accurate detection of target molecules. We have discovered a new mechanistically unique nanoparticle-target interaction resulting in a T(2) increase and demonstrate herein that this increase, and its associated r(2) relaxivity decrease, are also observed upon the interaction of the nanoparticles with ligands or molecular entities. Small molecules, proteins, and a 15-bp nucleic acid sequence were chemically conjugated to polyacrylic-acid-coated iron oxide nanoparticles, and all decreased the original nanoparticle r(2) value. Further experiments established that the r(2) decrease was inversely proportional to the number of ligands bound to the nanoparticle and the molecular weight of the bound ligand. Additional experiments revealed that the T(2)-increasing mechanism was kinetically faster than the conventional clustering mechanism. Most importantly, under conditions that result in T(2) increases, as little as 5.3 fmol of Bacillus anthracis plasmid DNA (pX01 and pX02), 8 pmol of the cholera toxin B subunit (Ctb), and even a few cancer cells in blood were detected. Transition from the binding to the clustering mechanism was observed in the carbohydrate-, Ctb-, and DNA-sensing systems, simply by increasing the target concentration significantly above the nanoparticle concentration, or using Ctb in its pentameric form as opposed to its monomer. Collectively, these results demonstrate that the molecular architectures resulting from the interaction between magnetic nanosensors and their targets directly govern water proton NMR relaxation. We attribute the observed T(2) increases to the bound target molecules partially obstructing the diffusion of solvent water molecules through the superparamagnetic iron oxide nanoparticles' outer relaxation spheres. Finally, we anticipate that this novel interaction can be incorporated into new clinical and field detection applications, due to its faster kinetics relative to the conventional nanoparticle-clustering assays.

Identification of molecular-mimicry-based ligands for cholera diagnostics using magnetic relaxation

When covalently bound to an appropriate ligand, iron oxide nanoparticles can bind to a specific target of interest. This interaction can be detected through changes in the solution's spin-spin relaxation times (T2) via magnetic relaxation measurements. In this report, a strategy of molecular mimicry was used in order to identify targeting ligands that bind to the cholera toxin B subunit (CTB). The cellular CTB-receptor, ganglioside GM1, contains a pentasaccharide moiety consisting in part of galactose and glucose units. We therefore predicted that CTB would recognize carbohydrate-conjugated iron oxide nanoparticles as GM1 mimics, thus producing a detectable change in the T2 relaxation times. Magnetic relaxation experiments demonstrated that CTB interacted with the galactose-conjugated nanoparticles. This interaction was confirmed via surface plasmon resonance studies using either the free or nanoparticle-conjugated galactose molecule. The galactose-conjugated nanoparticles were then used as CTB sensors achieving a detection limit of 40 pM. Via magnetic relaxation studies, we found that CTB also interacted with dextran-coated nanoparticles, and surface plasmon resonance studies also confirmed this interaction. Additional experiments demonstrated that the dextran-coated nanoparticle can also be used as CTB sensors and that dextran can prevent the internalization of CTB into GM1-expressing cells. Our work indicates that magnetic nanoparticle conjugates and magnetic relaxation detection can be used as a simple and fast method to identify targeting ligands via molecular mimicry. Furthermore, our results show that the dextran-coated nanoparticles represent a low-cost approach for CTB detection.

Magnetic nanoparticle biosensors

One of the major challenges in medicine is the rapid and accurate measurement of protein biomarkers, cells, and pathogens in biological samples. A number of new diagnostic platforms have recently been developed to measure biomolecules and cells with high sensitivity that could enable early disease detection or provide valuable insights into biology at the systems level. Most biological samples exhibit negligible magnetic susceptibility; therefore, magnetic nanoparticles have been used for diverse applications including biosensing, magnetic separation, and thermal ablation therapy. This review focuses on the use of magnetic nanoparticles for detection of biomolecules and cells based on magnetic resonance effects using a general detection platform termed diagnostic magnetic resonance (DMR). DMR technology encompasses numerous assay configurations and sensing principles, and to date magnetic nanoparticle biosensors have been designed to detect a wide range of targets including DNA/mRNA, proteins, enzymes, drugs, pathogens, and tumor cells. The core principle behind DMR is the use of magnetic nanoparticles as proximity sensors that modulate the spin-spin relaxation time of neighboring water molecules, which can be quantified using clinical MRI scanners or benchtop nuclear magnetic resonance (NMR) relaxometers. Recently, the capabilities of DMR technology were advanced considerably with the development of miniaturized, chip-based NMR (microNMR) detector systems that are capable of performing highly sensitive measurements on microliter sample volumes and in multiplexed format. With these and future advances in mind, DMR biosensor technology holds considerable promise to provide a high-throughput, low-cost, and portable platform for large scale molecular and cellular screening in clinical and point-of-care settings.

Preparation of cellulose magnetic microspheres with "the smallest critical size" and their application for microbial immunocapture

The goal of this paper is to introduce a universal method for quantitative control of the particle size of magnetic cellulose microspheres (MCMS) and to produce an optimal antibody absorption capability as an aid in the research of new applications of MCMS in immunomagnetic capture. In this study, "the smallest critical size theory" (TSCS) was proposed, tested, and confirmed by IgG-carrying capability measurements, magnetic response analysis, immunomagnetic capture, and PCR identification of bacteria. A Gaussian expression was proposed and used to guide the preparation of MCMS of the smallest critical size (SCS). The results showed that the diameter of the SCS of MCMS in this study was 5.82 mum, while the IgG absorption capability of the MCMS with SCS was 186.8 mg/mL. In addition, its high sensitivity and the efficiency of immunomagnetic capture of Salmonella bacteria exhibited another new application for MCMS.

Emerging nanotechnology-based strategies for the identification of microbial pathogenesis

Infectious diseases are still a major healthcare problem. From food intoxication and contaminated water, to hospital-acquired diseases and pandemics, infectious agents cause disease throughout the world. Despite advancements in pathogens' identification, some of the gold-standard diagnostic methods have limitations, including laborious sample preparation, bulky instrumentation and slow data readout. In addition, new field-deployable diagnostic modalities are urgently needed in first responder and point-of-care applications. Apart from compact, these sensors must be sensitive, specific, robust and fast, in order to facilitate detection of the pathogen even in remote rural areas. Considering these characteristics, researchers have utilized innovative approaches by employing the unique properties of nanomaterials in order to achieve detection of infectious agents, even in complex media like blood. From gold nanoparticles and their plasmonic shifts to iron oxide nanoparticles and changes in magnetic properties, detection of pathogens, toxins, antigens and nucleic acids has been achieved with impressive detection thresholds. Additionally, as bacteria become resistant to antibiotics, nanotechnology has achieved the rapid determination of bacterial drug susceptibility and resistance using novel methods, such as amperometry and magnetic relaxation. Overall, these promising results hint to the adoption of nanotechnology-based diagnostics for the diagnosis of infectious diseases in diverse settings throughout the globe, preventing epidemics and safeguarding human and economic wellness.

Invitro application of gold nanoprobes in live neurons for phenotypical classification, connectivity assessment, and electrophysiological recording

Thermoregulatory neurons in the preoptic area of the anterior hypothalamus (POA) form synaptic networks, which affect responses that regulate body temperature. To characterize these pathways of activation, projections to effector control areas, like the dorsomedial hypothalamus (DMH), require labeling in live tissue slices. Traditional fluorescent dyes label axon terminals near an injection site, but unfortunately, also that of nearby fibers of passage. Here, we describe a novel methodology for retrograde labeling of neurons in vitro, which will allow for further electrophysiological recording. To determine if POA neurons project to the DMH, we have used nanometer-sized, gold nanoprobes, which provide for specific neuronal entry, via synapses in close proximity to the injection site. Upon neuronal entry, these nanoprobe complexes diffuse to the soma, where they are readily visualized and quantified. We found that conjugation of these gold nanoprobes with VGLUT-2 antibodies and polyethyleneimine (PEI) facilitates neuronal entry and a high level of labeling efficacy. This novel method, adapted from emerging cancer therapy technologies, is highly specific for determining axon terminal projections within particular neuronal populations, while maintaining neuronal viability for targeted live cell electrophysiological recording.

Magnetic nanoparticles for biomedical NMR-based diagnostics

Rapid and accurate measurements of protein biomarkers, pathogens and cells in biological samples could provide useful information for early disease diagnosis, treatment monitoring, and design of personalized medicine. In general, biological samples have only negligible magnetic susceptibility. Thus, using magnetic nanoparticles for biosensing not only enhances sensitivity but also effectively reduces sample preparation needs. This review focuses on the use of magnetic nanoparticles for in vitro detection of biomolecules and cells based on magnetic resonance effects. This detection platform, termed diagnostic magnetic resonance (DMR), exploits magnetic nanoparticles as proximity sensors, which modulate the spin-spin relaxation time of water molecules surrounding molecularly-targeted nanoparticles. By developing more effective magnetic nanoparticle biosensors, DMR detection limits for various target moieties have been considerably improved over the last few years. Already, a library of magnetic nanoparticles has been developed, in which a wide range of targets, including DNA/mRNA, proteins, small molecules/drugs, bacteria, and tumor cells, have been quantified. More recently, the capabilities of DMR technology have been further advanced with new developments such as miniaturized nuclear magnetic resonance detectors, better magnetic nanoparticles and novel conjugational methods. These developments have enabled parallel and sensitive measurements to be made from small volume samples. Thus, the DMR technology is a highly attractive platform for portable, low-cost, and efficient biomolecular detection within a biomedical setting.

Magnetic nanoparticle sensors

Many types of biosensors employ magnetic nanoparticles (diameter = 5–300 nm) or magnetic particles (diameter = 300–5,000 nm) which have been surface functionalized to recognize specific molecular targets. Here we cover three types of biosensors that employ different biosensing principles, magnetic materials, and instrumentation. The first type consists of magnetic relaxation switch assay-sensors, which are based on the effects magnetic particles exert on water proton relaxation rates. The second type consists of magnetic particle relaxation sensors, which determine the relaxation of the magnetic moment within the magnetic particle. The third type is magnetoresistive sensors, which detect the presence of magnetic particles on the surface of electronic devices that are sensitive to changes in magnetic fields on their surface. Recent improvements in the design of magnetic nanoparticles (and magnetic particles), together with improvements in instrumentation, suggest that magnetic material-based biosensors may become widely used in the future.

Role of nanoparticle valency in the nondestructive magnetic-relaxation-mediated detection and magnetic isolation of cells in complex media

Nanoparticle-based diagnostics typically involve the conjugation of targeting ligands to the nanoparticle to create a sensitive and specific nanosensor that can bind and detect the presence of a target, such as a bacterium, cancer cell, protein, or DNA sequence. Studies that address the effect of multivalency on the binding and detection pattern of these nanosensors, particularly on magnetic relaxation nanosensors that sense the presence of a target in a dose-dependent manner by changes in the water relaxation times (DeltaT2), are scarce. Herein, we study the effect of multivalency on the detection profile of cancer cells and bacteria in complex media, such as blood and milk. In these studies, we conjugated folic acid at two different densities (low-folate and high-folate) on polyacrylic-acid-coated iron oxide nanoparticles and studied the interaction of these magnetic nanosensors with cancer cells expressing the folate receptor. Results showed that the multivalent high-folate magnetic relaxation nanosensor performed better than its low folate counterpart, achieving single cancer cell detection in blood samples within 15 min. Similar results were also observed when a high molecular weight anti-folate antibody (MW 150 kDa) was used instead of the low molecular weight folic acid ligand (MW 441.4 kDa), although better results in terms of sensitivity, dynamic range, and speed of detection were obtained when the folate ligand was used. Studies using bacteria in milk suspensions corroborated the results observed with cancer cells. Taken together, these studies demonstrate that nanoparticle multivalency plays a key role in the interaction of the nanoparticle with the cellular target and modulate the behavior and sensitivity of the assay. Furthermore, as detection with magnetic relaxation nanosensors is a nondestructive technique, magnetic isolation and further characterization of the cancer cells is possible.

Integrated nanosensors to determine levels and functional activity of human telomerase

Telomerase is a key oncogenic enzyme, and a number of novel telomerase inhibitors are currently under development. Because inhibition can be achieved either at the protein or at the enzymatic activity level, independent measurements of these parameters are important in the development of effective therapeutic agents. In the current study, we have developed a set of functional magnetic nanosensors capable of measuring the concentration of telomerase, as well as its enzymatic activity in parallel. The method is based on a magnetic relaxation switch assay, which can be performed in crude tissue samples and is fast and extremely sensitive. Using this method, we were able to detect different amounts of telomerase protein and activity in various cancer and normal cell lines. Furthermore, we were able to study the effect of phosphorylation on telomerase activity. This system not only could provide a rapid assay for the evaluation of antitelomerase therapies but could also be implemented to the study of other cancer markers.

Rapid nanoparticle-mediated monitoring of bacterial metabolic activity and assessment of antimicrobial susceptibility in blood with magnetic relaxation

Considering the increased incidence of bacterial infections and the emergence of multidrug resistant bacteria at the global level, we designed superparamagnetic iron oxide nanoparticles as nanosensors for the assessment of antimicrobial susceptibility through magnetic relaxation. In this report, we demonstrate that iron oxide nanosensors, either dextran-coated supplemented with Con A or silica-coated conjugated directly to Con A, can be used for the fast (1) quantification of polysaccharides, (2) assessment of metabolic activity and (3) determination of antimicrobial susceptibility in blood. The use of these polysaccharide nanosensors in the determination of antimicrobial susceptibility in the clinic or the field, and the utilization of these nanoprobes in pharmaceutical R&D are anticipated.

Multifunctional magnetic nanoparticles for targeted imaging and therapy

Magnetic nanoparticles have become important tools for the imaging of prevalent diseases, such as cancer, atherosclerosis, diabetes, and others. While first generation nanoparticles were fairly nonspecific, newer generations have been targeted to specific cell types and molecular targets via affinity ligands. Commonly, these ligands emerge from phage or small molecule screens, or are based on antibodies or aptamers. Secondary reporters and combined therapeutic molecules have further opened potential clinical applications of these materials. This review summarizes some of the recent biomedical applications of these newer magnetic nanomaterials.

Application of magnetic nanoparticles in biomedicine

The use of nanomaterials offers many advantages due to their unique properties. They can be used as building blocks for the fabrication of various functional diagnostic systems and agents of therapy. This article focuses on the application of magnetic nanoparticles in biomedicine such as magnetic separation, biosensor, contrast agents for MRI (magnetic resonance imaging), local operated hyperthermic treatment of tumors, drug delivery, gene therapy, tissue engineering.

A novel magnetic bead-based assay with high sensitivity and selectivity for analysis of telomerase in exfoliated cells from patients with bladder and colon cancer

Telomerase activity is elevated in more than 85% of cancer cells and absent in most of the normal cells and thus represents a potential cancer biomarker. We report its measurement in colon and bladder cancer cells captured using antibody-coated magnetic beads. The cells are lysed and telomerase activity is detected using a biosensor assay that employs an oligonucleotide containing the telomerase recognition sequence also covalently coupled to magnetic beads. Telomerase activity is measured by the incorporation of multiple biotinylated nucleotides at the 3'-end of the oligonucleotide strands during elongation which are then reacted with streptavidin-conjugated horseradish peroxidase. A luminescent signal is generated when hydrogen peroxidase is added in the presence of luminol and a signal enhancer. LOD experiments confirm sensitivity down to ten cancer cell equivalents. The telomerase assay reliably identified patient samples considered by an independent pathological review to contain cancer cells. Samples from normal healthy volunteers were all telomerase negative. The assay, which is amenable to automation, demonstrated high sensitivity and specificity in a small clinical cohort, making it of potential benefit as a first line assay for detection and monitoring of colon and bladder cancer.

Magnetic labeling, detection, and system integration

Among the plethora of affinity biosensor systems based on biomolecular recognition and labeling assays, magnetic labeling and detection is emerging as a promising new approach. Magnetic labels can be non-invasively detected by a wide range of methods, are physically and chemically stable, relatively inexpensive to produce, and can be easily made biocompatible. Here we provide an overview of the various approaches developed for magnetic labeling and detection as applied to biosensing. We illustrate the challenges to integrating one such approach into a complete sensing system with a more detailed discussion of the compact Bead Array Sensor System developed at the U.S. Naval Research Laboratory, the first system to use magnetic labels and microchip-based detection.

Biosensor Techniques Used for Determination of Telomerase Activity in Cancer Cells

Measuring telomerase activity has proven successful for the determination of cancer in malignant somatic cells. Early conventional methods for the detection of telomerase activity include in vitro analysis via a primer extension assay, and the telomeric repeat amplification protocol (TRAP) assay. TRAP incorporates the polymerase chain reaction (PCR) step to increase the sensitivity of a given sample. However, research suggests that the TRAP technique suffers from false negative results, caused by failure of its PCR step. Other limitations of TRAP include the post-PCR steps involving polyacrylamide gel electrophoresis which are time inefficient. Thus, various efforts have been made to eliminate the PCR step of TRAP by using a variety of biosensor detection devices. This review mainly focuses on these alternatives including: optical, electrochemical, magnetic, and nanowire conductive signaling techniques to measure the telomerase activity produced via label free biosensor assay—via biocatalytic labels involving beacons, DNAzyme, ferrocenyl-naphthalene diimides, avidin-alkaline phosphatase and semiconductor quantum dots (QDs). These biosensor techniques are sensitive and provide precise and rapid results in the detection of telomerase activity.

Biodegradable, polymeric nanoparticle delivery systems for cancer therapy

Nanotechnology has the potential to impact the treatment of cancer significantly. This review will explore how this potential is beginning to be realized through the design of polymeric nanoparticle delivery systems. Current research is focused on developing biocompatible nanoparticles capable of targeting specific cancer markers and delivering imaging and therapeutic agents for the detection and treatment of cancer, resulting in a number of preclinical and clinical applications. More sophisticated nanoparticle designs are now in development, including particles able to release multiple drugs for enhanced treatment efficacy and targeted, multifunctional particles capable of combining imaging and drug release.

Transcription MRI: a new view of the living brain

Altered gene activities are underlying causes of many neurological disorders. The ability to detect, image, and report endogenous gene transcription using magnetic resonance (MR) holds great potential for providing significant clinical benefits. In this review, we present the development of conjugates consisting of gene-targeting short nucleic acids (oligodeoxynucleotides, or sODN) and superparamagnetic iron oxide nanoparticles (SPION, an MR susceptibility T(2) agent) for reporting gene activity using transcription MRI (tMRI). We will discuss 1) the target specificity of sODN, 2) selection of contrast agents for tMRI, 3) the distribution and uptake, 4) sequence specificity, 5) histology of SPION and sODN, 6) data acquisition and quantitative analysis for tMRI, and 7) application of gene transcript-targeting nanoparticles in biology and medicine. We will also discuss methods of validating the correlation between results from conventional assays (in situ hybridization, PCR, histology Prussian blue stain and immunohistochemistry) in postmortem samples and retention of SPION-sODN using tMRI. The application of our novel contrast probe to report and target gene transcripts in the mesolimbic pathways of living mouse brains after amphetamine exposure will be discussed. Because of the targeting ability in the nucleic acid sequence, the concept of tMRI probes with complementary nucleic acid (antisense DNA or short interfering RNA) allows not only tracking, targeting, binding to intracellular mRNA, and manipulating gene action but also tracing cells with specific gene action in living brains. Transcription MRI will lend itself to myriad applications in living organs.

Analysis of human telomerase activity and function by two color single molecule coincidence fluorescence spectroscopy

Telomerase is a nonclassical DNA polymerase that uses its integral RNA as a template to synthesize telomeric repeats onto chromosome ends. The molecular mechanism of telomerase is unique and involves a translocation step after the synthesis of each telomeric repeat. To directly measure the enzymatic turnover of substrate and the efficiency of the translocation step we have extended our two-color single molecule fluorescence coincidence method (Anal.Chem. 2003, 75, 1664-1670). The method employs Cy5-dATP incorporation into a DNA primer that has been prelabeled with a reference fluorophore. Measurements are performed in the single molecule regime and products, which necessarily have both fluorophores, are excited by two independent lasers, and give rise to coincident events. By counting the number of coincident events and using the coincidence detection efficiency, it is possible to determine the number of the extended products generated by attomole quantities of telomerase, without separation or the use of PCR or radioactivity. Histograms of the logarithms of the ratios of the Cy5 to the reference fluorophore fluorescence can be used to determine the length distribution of the products and hence the enzyme processivity. The mean processivity obtained from the single molecule fluorescence coincidence assay is 0.32 +/- 0.04, in good agreement with the value of 0.37 +/- 0.05 derived from the direct radioactive assay approach. The function of the alignment domain of human telomerase RNA in sustaining catalytic activity in vitro has been reevaluated using this method. Together with our previous results (Nucleic Acids Res. 2002, 30, 4470-4480) these experiments identify the essential residues in the alignment domain of human telomerase RNA that contribute to the activity and processivity of telomerase.

Targeted delivery of multifunctional magnetic nanoparticles

Magnetic nanoparticles and their magnetofluorescent analogues have become important tools for in vivo imaging using magnetic resonance imaging and fluorescent optical methods. A number of monodisperse magnetic nanoparticle preparations have been developed over the last decade for angiogenesis imaging, cancer staging, tracking of immune cells (monocyte/macrophage, T cells) and for molecular and cellular targeting. Phage display and data mining have enabled the procurement of novel tissue- or receptor-specific peptides, while high-throughput screening of diversity-oriented synthesis libraries has identified small molecules that permit or prevent uptake by specific cell types. Next-generation magnetic nanoparticles are expected to be truly multifunctional, incorporating therapeutic functionalities and further enhancing an already diverse repertoire of capabilities.

Nanotechnology and its relevance to the urologist

OBJECTIVES

We review important aspects of nanotechnology, and discuss the wide range of research and clinical applications of nanomedicine in the field of urology. There is particular emphasis on key clinical and pre-clinical studies to provide an update on recent and potential applications in the care of urological patients.

METHODS

A directed Medline literature review of nanotechnology was performed. Important publications that have shaped our understanding of nanotechnology were selected for review and were augmented by manual searches of reference lists.

RESULTS

Nanotechnology is the study, design, creation, synthesis, manipulation, and application of functional materials, devices, and systems through control of matter at the nanometer scale. Studies demonstrate a number of important concepts. These include nanovectors, nanotubes, and nanosensors for targeted drug delivery; nanowires and nanocantilever arrays for early detection of precancerous and malignant lesions; and nanopores for DNA sequencing. These advances will lead to significant applications relevant to the diagnosis, management, and treatment of all urological conditions.

CONCLUSIONS

This review is designed for the urologist to provide an overview and update on nanotechnology and its applications in the field of urology. In the future, it is widely expected that nanotechnology and nanomedicine will have a significant impact on urological research and clinical practice, allowing urologists to intervene at the cellular and molecular level. With structured, safe implementation, nanotechnologies have the potential to revolutionise urological practice in our lifetime.

[Molecular imaging: future uses in arthritides]

Molecular imaging is an upcoming field in radiology as a result of great advances in imaging technology, genetics, and biochemistry in the recent past. Early-stage imaging of molecular pathological changes in cells opens the gates to new methods in medical treatment of diseases that otherwise would only be detected in advanced stages. Methods of imaging biochemical pathways with molecular agents are currently an issue of intensive research. This article reviews current modalities of molecular imaging in arthritis that should offer future perspective on early disease detection, diagnosis, and monitoring of treatment efficiency and how they can pave the way to optimized therapy.

Efficient manipulation of nanoparticle-bound DNA via restriction endonuclease

As a programmable biopolymer, DNA has shown great potential in the fabrication and construction of nanometer-scale assemblies and devices. In this report, we described a strategy for efficient manipulation of gold nanoparticle-bound DNA using restriction endonuclease. The digestion efficiency of this restriction enzyme was studied by varying the surface coverage of stabilizer, the size of nanoparticles, as well as the distance between the nanoparticle surface and the enzyme-cutting site of particle-bound DNA. We found that the surface coverage of stabilizer is crucial for achieving high digestion efficiency. In addition, this stabilizer surface coverage can be tailored by varying the ion strength of the system. Based on the results of polyacrylamide gel electrophoresis and fluorescent study, a high digestion efficiency of 90+% for particle-bound DNA was achieved for the first time. This restriction enzyme manipulation can be considered as an additional level of control of the particle-bound DNA and is expected to be applied to manipulate more complicated nanostructures assembled by DNA.

Emerging implications of nanotechnology on cancer diagnostics and therapeutics

Nanotechnology is multidisciplinary field that involves the design and engineering of objects <500 nanometers (nm) in size. The National Cancer Institute has recognized that nanotechnology offers an extraordinary, paradigm-changing opportunity to make significant advances in cancer diagnosis and treatment. In the last several decades, nanotechnology has been studied and developed primarily for use in novel drug-delivery systems (e.g. liposomes, gelatin nanoparticles, micelles). A recent explosion in engineering and technology has led to 1) the development of many new nanoscale platforms, including quantum dots, nanoshells, gold nanoparticles, paramagnetic nanoparticles, and carbon nanotubes, and 2) improvements in traditional, lipid-based nanoscale platforms. The emerging implications of these platforms for advances in cancer diagnostics and therapeutics form the basis of this review. A widespread understanding of these new technologies is important, because they currently are being integrated into the clinical practice of oncology.

Superparamagnetic Iron Oxide Nanoparticle Probes for Molecular Imaging

The field of molecular imaging has recently seen rapid advances in the development of novel contrast agents and the implementation of insightful approaches to monitor biological processes non-invasively. In particular, superparamagnetic iron oxide nanoparticles (SPIO) have demonstrated their utility as an important tool for enhancing magnetic resonance contrast, allowing researchers to monitor not only anatomical changes, but physiological and molecular changes as well. Applications have ranged from detecting inflammatory diseases via the accumulation of non-targeted SPIO in infiltrating macrophages to the specific identification of cell surface markers expressed on tumors. In this article, we attempt to illustrate the broad utility of SPIO in molecular imaging, including some of the recent developments, such as the transformation of SPIO into an activatable probe termed the magnetic relaxation switch.

Biofunctional magnetic nanoparticles for protein separation and pathogen detection

Recent successful syntheses of monodispersed magnetic nanoparticles have offered a unique opportunity to control and probe biological interactions using magnetic force. This paper highlights a general strategy to generate biofunctional magnetic nanoparticles, illustrates applications for these nanoparticles in protein separation and pathogen detection, and analyzes the high sensitivity and high selectivity achieved by this system.

Nanotechnology: Towards the detection and treatment of inflammatory diseases

Biological systems operate at the nanoscale. Nanomedicine is the application of nanotechnology to monitor and treat biological systems in health and disease. This is accomplished by real time monitoring of molecular signaling at the cellular and tissue level. During the past decade, there has been an explosion in this field, resulting in revolutionary advances in determining the microstructure and function of living systems. These discoveries have led to the development of powerful tools for fundamental biological and medical research. Nanotechnology has been applied to targeted drug delivery to minimize side effects, creating implantable materials as scaffolds for tissue engineering, creating implantable devices, surgical aids and nanorobotics, as well as throughput drug screening and medical diagnostic imaging. The nanoinitiatives are funded by governments and private sources throughout the world to develop or further refine the technology to provide the beyond-imaginable, most sophisticated tools to a physician and scientists to inflammatory diseases. No doubt, there will be many technical, regulatory and legal challenges in the deployment of these technologies. Unquestionably, there is enough desire and commitment to meet these challenges for the good of society and betterment of the quality of life.

The role of nanobiotechnology in drug discovery

The application of nanotechnology in life sciences, nanobiotechnology, is already having an impact on diagnostics and drug delivery. Now, researchers are starting to use nanotechnology in the field of drug discovery. This review explains how several technologies, including nanoparticles and nanodevices such as nanobiosensors and nanobiochips, are used to improve drug discovery and development. Nanoscale assays can contribute significantly to cost-saving in screening campaigns. In addition, some nanosubstances (such as fullerenes) could be potential drugs for the future. Although there might be some safety concerns with respect to the in vivo use of nanoparticles, studies are in place to determine the nature and extent of adverse events. Future prospects for the application of nanotechnology in healthcare and for the development of personalized medicine appear to be excellent.

Nanotechnology in clinical laboratory diagnostics

Nanotechnology-the creation and utilization of materials, devices, and systems through the control of matter on the nanometer-has been applied to molecular diagnostics. This article reviews nanobiotechnologies that are clinically relevant and have the potential to be incorporated in clinical laboratory diagnosis. Nanotechnologies enable the diagnosis at single cell and molecule level and some of these can be incorporated in the current molecular diagnostics such as biochips. Nanoparticles, such as gold nanoparticles and quantum dots, are the most widely used but various other nanotechnologies for manipulation at nanoscale as well as nanobiosensors are reviewed. These technologies will extend the limits of current molecular diagnostics and enable point-of-care diagnosis as well as the development of personalized medicine. Although the potential diagnostic applications are unlimited, most important current applications are foreseen in the areas of biomarker research, cancer diagnosis and detection of infectious microorganisms.

Molecular MR Imaging Probes

Magnetic resonance imaging (MRI) has been successfully applied to many of the applications of molecular imaging. This review discusses by example some of the advances in areas such as multimodality MR-optical agents, receptor imaging, apoptosis imaging, angiogenesis imaging, noninvasive cell tracking, and imaging of MR marker genes.

MR and optical approaches to molecular imaging

With an increasing understanding of the molecular basis of disease, various new imaging targets have recently been defined that potentially allow for an early, sensitive, and specific diagnosis of disease or monitoring of treatment response. Different approaches to depict these molecular structures in vivo are currently being explored by the molecular imaging community. We briefly review methodologies for molecular imaging by magnetic resonance imaging and optical methods. Special emphasis is put on different contrast agent designs (e.g., targeted and smart probes). New technical developments in optical imaging are briefly discussed. In addition, current research results are put into a clinical perspective to elucidate the potential merits one might expect from this new research field.

Cancer nanotechnology: opportunities and challenges

Nanotechnology is a multidisciplinary field, which covers a vast and diverse array of devices derived from engineering, biology, physics and chemistry. These devices include nanovectors for the targeted delivery of anticancer drugs and imaging contrast agents. Nanowires and nanocantilever arrays are among the leading approaches under development for the early detection of precancerous and malignant lesions from biological fluids. These and other nanodevices can provide essential breakthroughs in the fight against cancer.

Magnetic Resonance Imaging: Utility as a Molecular Imaging Modality

Significant scientific effort has gone into the deconvolution and understanding of complex biological systems. These efforts have yielded much information about the molecular changes that are causative or arise as a result of disease. Molecular imaging is a relatively newer field that is attempting to use these molecular data to generate images that report on changes in gene expression. It has been demonstrated that generating images based on molecular differences rather than anatomical differences between tissues has resulted in more sensitive detection of diseased tissues and has allowed imaging of drug efficacy against particular drug targets. This chapter discusses the application of magnetic resonance imaging (MRI) to molecular imaging. It begins with a review of the basis for magnetic resonance image generation and how manipulation of different parameters of the system can be applied to molecular imaging. It then specifically reviews some of the problematic areas for magnetic resonance application to molecular imaging and how these can be resolved by manipulating the magnetic resonance system, altering magnetic resonance probe characteristics, or exploiting the biology to be imaged. It concludes with several examples demonstrating the utility of MRI to generate high-resolution, noninvasive images of molecular events occurring in vivo.

Iron oxide MR contrast agents for molecular and cellular imaging

Molecular and cellular MR imaging is a rapidly growing field that aims to visualize targeted macromolecules or cells in living organisms. In order to provide a different signal intensity of the target, gadolinium-based MR contrast agents can be employed although they suffer from an inherent high threshold of detectability. Superparamagnetic iron oxide (SPIO) particles can be detected at micromolar concentrations of iron, and offer sufficient sensitivity for T2(*)-weighted imaging. Over the past two decades, biocompatible particles have been linked to specific ligands for molecular imaging. However, due to their relatively large size and clearance by the reticuloendothelial system (RES), widespread biomedical molecular applications have yet to be implemented and few studies have been reproduced between different laboratories. SPIO-based cellular imaging, on the other hand, has now become an established technique to label and detect the cells of interest. Imaging of macrophage activity was the initial and still is the most significant application, in particular for tumor staging of the liver and lymph nodes, with several products either approved or in clinical trials. The ability to now also label non-phagocytic cells in culture using derivatized particles, followed by transplantation or transfusion in living organisms, has led to an active research interest to monitor the cellular biodistribution in vivo including cell migration and trafficking. While most of these studies to date have been mere of the 'proof-of-principle' type, further exploitation of this technique will be aimed at obtaining a deeper insight into the dynamics of in vivo cell biology, including lymphocyte trafficking, and at monitoring therapies that are based on the use of stem cells and progenitors.