Multiplexed magnetic labeling amplification using oligonucleotide hybridization

A non-lipid nucleic acid delivery vector with dendritic cell tropism and stimulation

Rationale: Nucleic acid constructs are commonly used for vaccination, immune stimulation, and gene therapy, but their use in cancer still remains limited. One of the reasons is that systemic delivery to tumor-associated antigen-presenting cells (dendritic cells and macrophages) is often inefficient, while off-target nucleic acid-sensing immune pathways can stimulate systemic immune responses. Conversely, certain carbohydrate nanoparticles with small molecule payloads have been shown to target these cells efficiently in the tumor microenvironment. Yet, nucleic acid incorporation into such carbohydrate-based nanoparticles has proven challenging. Methods: We developed a novel approach using cross-linked bis succinyl-cyclodextrin (b-s-CD) nanoparticles to efficiently deliver nucleic acids and small-molecule immune enhancer to phagocytic cells in tumor environments and lymph nodes. Our study involved incorporating these components into the nanoparticles and assessing their efficacy in activating antigen-presenting cells. Results: The multi-modality immune stimulators effectively activated antigen-presenting cells and promoted anti-tumor immunity in vivo. This was evidenced by enhanced delivery to phagocytic cells and subsequent immune response activation in tumor environments and lymph nodes. Conclusion: Here, we describe a new approach to incorporating both nucleic acids and small-molecule immune enhancers into cross-linked bis succinyl-cyclodextrin (b-s-CD) nanoparticles for efficient delivery to phagocytic cells in tumor environments and lymph nodes in vivo. These multi-modality immune stimulators can activate antigen-presenting cells and foster anti-tumor immunity. We argue that this strategy can potentially be used to enhance anti-tumor efficacy.

Advances in the Application of Magnetic Nanoparticles for Sensing

Magnetic nanoparticles (MNPs) are of high significance in sensing as they provide viable solutions to the enduring challenges related to lower detection limits and nonspecific effects. The rapid expansion in the applications of MNPs creates a need to overview the current state of the field of MNPs for sensing applications. In this review, the trends and concepts in the literature are critically appraised in terms of the opportunities and limitations of MNPs used for the most advanced sensing applications. The latest progress in MNP sensor technologies is overviewed with a focus on MNP structures and properties, as well as the strategies of incorporating these MNPs into devices. By looking at recent synthetic advancements, and the key challenges that face nanoparticle-based sensors, this review aims to outline how to design, synthesize, and use MNPs to make the most effective and sensitive sensors.

Diagnostic Applications of Morpholinos and Label-Free Electrochemical Detection of Nucleic Acids

Diagnostic applications of morpholinos take advantage of their unique properties including backbone charge neutrality, a weak impact of ionic strength on their hybridization behavior, and their resistance to enzymatic degradation. This chapter overviews how these properties have advanced transduction and other capabilities useful for the analysis of nucleic acids. In many cases, the benefits stem from electrostatic mechanisms; for example, use of low ionic strengths improves sensitivity of detection while decreasing background signals because only the nucleic acid analyte is charged. While most literature reports focus on in vitro assays in buffer, morpholinos have been also used for biodistribution measurements of species such as fungal rRNA and miRNA. After reviewing the diagnostic applications of morpholinos, the chapter describes preparation of morpholino monolayers on metal supports for electrochemical diagnostics and the procedure for performing label-free detection of DNA from changes in surface capacitance.

Facile Coating Strategy to Functionalize Inorganic Nanoparticles for Biosensing

The use of inorganic nanoparticles (NPs) for biosensing requires that they exhibit high colloidal stability under various physiological conditions. Here, we report on a general approach to render hydrophobic NPs into hydrophilic ones that are ready for bioconjugation. The method uses peglyated polymers conjugated with multiple dopamines, which results in multidentate coordination. As proof-of-concept, we applied the coating to stabilize ferrite and lanthanide NPs synthesized by thermal decomposition. Both polymer-coated NPs showed excellent water solubility and were stable at high salt concentrations under physiological conditions. We used these NPs as molecular-sensing agents to detect exosomes and bacterial nucleic acids.

Antibody-free detection of infectious bacteria using quantum dots-based barcode assay

Staphylococcus aureus, methicillin-resistant Staphylococcus aureus and Klebsiella pneumoniae are the most representative bacteria causing infectious diseases. Due to the increased application of antibiotics, the bacterial resistance is growing causing severe complications. Therefore, a sensitive determination of these pathogens is crucial for effective treatment. The aim of this study was to design an effective method for multiplex detection of Staphylococcus aureus, methicillin-resistant Staphylococcus aureus and Klebsiella pneumoniae taking advantage from properties of magnetic particles as well as fluorescent nanoparticles (quantum dots). The method was able to detect as low concentrations of bacteria as 10² CFU/mL using the bacteria-specific genes (fnbA, mecA and wcaG).

Click Chemistry-Mediated Nanosensors for Biochemical Assays

Click chemistry combined with functional nanoparticles have drawn increasing attention in biochemical assays because they are promising in developing biosensors with effective signal transformation/amplification and straightforward signal readout for clinical diagnostic assays. In this review, we focus on the latest advances of biochemical assays based on Cu (I)-catalyzed 1, 3-dipolar cycloaddition of azides and alkynes (CuAAC)-mediated nanosensors, as well as the functionalization of nanoprobes based on click chemistry. Nanoprobes including gold nanoparticles, quantum dots, magnetic nanoparticles and carbon nanomaterials are covered. We discuss the advantages of click chemistry-mediated nanosensors for biochemical assays, and give perspectives on the development of click chemistry-mediated approaches for clinical diagnosis and other biomedical applications.

Nanotheranostics: Congo Red/Rutin-MNPs with Enhanced Magnetic Resonance Imaging and H2O2-Responsive Therapy of Alzheimer's Disease in APPswe/PS1dE9 Transgenic Mice

As nanotheranostics, Congo red/Rutin-MNPs combine the abilities of diagnosis and treatment of Alzheimer's disease (AD). The biocompatible nanotheranostics system based on iron oxide magnetic nanoparticles, with ultrasmall size and excellent magnetic properties, can specifically detect amyloid plaques by magnetic resonance imaging, realize targeted delivery of AD therapeutic agents, achieve drug controlled release by H2O2 response, and prevent oxidative stress.

Magnetic sensing technology for molecular analyses

Magnetic biosensors, based on nanomaterials and miniature electronics, have emerged as a powerful diagnostic platform. Benefiting from the inherently negligible magnetic background of biological objects, magnetic detection is highly selective even in complex biological media. The sensing thus requires minimal sample purification and yet achieves a high signal-to-background contrast. Moreover, magnetic sensors are also well-suited for miniaturization to match the size of biological targets, which enables sensitive detection of rare cells and small amounts of molecular markers. We herein summarize recent advances in magnetic sensing technologies, with an emphasis on clinical applications in point-of-care settings. Key components of sensors, including magnetic nanomaterials, labeling strategies and magnetometry, are reviewed.

Magnetic ligation method for quantitative detection of microRNAs

A magnetic ligation method is utilized for the detection of microRNAs among a complex biological background without polymerase chain reaction or nucleotide modification. The sandwich probes assay can be adapted to analyze a panel of microRNAs associated with cardiovascular diseases in heart tissue samples.

Microchip-based detection of magnetically labeled cancer biomarkers

Micro-magnetic sensing and actuation have emerged as powerful tools for the diagnosis and monitoring of cancer. These technologies can be miniaturized and integrated onto compact, microfluidic platforms, enabling molecular diagnostics to be performed in practical clinical settings. Molecular targets tagged with magnetic nanoparticles can be detected with high sensitivity directly in unprocessed clinical samples (e.g. blood, sputum) due to the inherently negligible magnetic susceptibility of biological material. As a result, magnetic microchip-based diagnostics have been applied with great success to the isolation and detection of rare cells and the measurement of sparse soluble proteins. In this paper, we review recent advances in microchip-based detection of magnetically labeled biomarkers and their translation to clinical applications in cancer.

Magnetic barcode assay for genetic detection of pathogens

The task of rapidly identifying patients infected with Mycobacterium tuberculosis in resource-constrained environments remains a challenge. A sensitive and robust platform that does not require bacterial isolation or culture is critical in making informed diagnostic and therapeutic decisions. Here we introduce a platform for the detection of nucleic acids based on a magnetic barcoding strategy. PCR-amplified mycobacterial genes are sequence-specifically captured on microspheres, labelled by magnetic nanoprobes and detected by nuclear magnetic resonance. All components are integrated into a single, small fluidic cartridge for streamlined on-chip operation. We use this platform to detect M. tuberculosis and identify drug-resistance strains from mechanically processed sputum samples within 2.5 h. The specificity of the assay is confirmed by detecting a panel of clinically relevant non-M. tuberculosis bacteria, and the clinical utility is demonstrated by the measurements in M. tuberculosis-positive patient specimens. Combined with portable systems, the magnetic barcode assay holds promise to become a sensitive, high-throughput and low-cost platform for point-of-care diagnostics.

Comparison of select cancer biomarkers in human circulating and bulk tumor cells using magnetic nanoparticles and a miniaturized micro-NMR system

Circulating tumor cells (CTC) harvested from peripheral blood have received significant interest as sources for serial sampling to gauge treatment efficacy. Nanotechnology and microfluidic based approaches are emerging to facilitate such analyses. While of considerable clinical importance, there is little information on how similar or different CTCs are from their shedding bulk tumors. In this clinical study, paired tumor fine needle aspirate and peripheral blood samples were obtained from cancer patients during image-guided biopsy. Using targeted magnetic nanoparticles and a point-of-care micro-NMR system, we compared selected biomarkers (EpCAM, EGFR, HER-2 and vimentin) in both CTC and fine needle biopsies of solid epithelial cancers. We show a weak correlation between each paired sample, suggesting that use of CTC as "liquid biopsies" and proxies to metastatic solid lesions could be misleading.

FROM THE CLINICAL EDITOR

In this clinical study, paired tumor fine needle aspirate and peripheral blood samples were obtained from patients with solid epithelial cancers during image-guided biopsy. Using targeted magnetic nanoparticles and a point-of-care micro-NMR system, the authors compared selected biomarkers in both circulating tumor cells (CTC) and fine needle biopsies, demonstrating a weak correlation between each paired sample, suggesting that use of CTC could be misleading in this context.

On-chip bioorthogonal chemistry enables immobilization of in situ modified nanoparticles and small molecules for label-free monitoring of protein binding and reaction kinetics

Efficient methods to immobilize small molecules under continuous-flow microfluidic conditions would greatly improve label-free molecular interaction studies using biosensor technology. At present, small-molecule immobilization chemistries require special conditions and in many cases must be performed outside the detector and microfluidic system where real-time monitoring is not possible. Here, we have developed and optimized a method for on-chip bioorthogonal chemistry that enables rapid, reversible immobilization of small molecules with control over orientation and immobilization density, and apply this technique to surface plasmon resonance (SPR) studies. Immobilized small molecules reverse the orientation of canonical SPR interaction studies, and also enable a variety of new SPR applications including on-chip assembly and interaction studies of multicomponent structures, such as functionalized nanoparticles, and measurement of bioorthogonal reaction rates. We use this approach to demonstrate that on-chip assembled functionalized nanoparticles show a preserved ability to interact with their target protein, and to measure rapid bioorthogonal reaction rates with k(2) > 10(3) M(-1) s(-1). This method offers multiple benefits for microfluidic biological applications, including rapid screening of targeted nanoparticles with vastly decreased nanoparticle synthetic requirements, robust immobilization chemistry in the presence of serum, and a continuous flow technique that mimics biologic contexts better than current methods used to measure bioorthogonal reaction kinetics such as NMR or UV-vis spectroscopy (e.g., stopped flow kinetics). Taken together, this approach constitutes a flexible and powerful technique for evaluating a wide variety of reactions and intermolecular interactions for in vitro or in vivo applications.

Orthogonal amplification of nanoparticles for improved diagnostic sensing

There remains an ongoing need for fast, highly sensitive, and quantitative technologies that can detect and profile rare cells in freshly harvested samples. Recent developments in nanomaterial-based detection platforms provide advantages over traditional approaches in terms of signal sensitivity, stability, and the possibility for performing multiplexed measurements. Here, we describe a bioorthogonal, nanoparticle amplification technique capable of rapid augmentation of detection sensitivities by up to 1-2 orders of magnitude over current methods. This improvement in sensitivity was achieved by (i) significantly reducing background noise arising from nonspecific nanoparticle binding, (ii) increasing nanomaterial binding through orthogonal rounds of amplification, and (iii) implementing a cleavage step to improve assay robustness. The developed method allowed sensitive detection and molecular profiling of scant tumor cells directly in unpurified human clinical samples such as ascites. With its high sensitivity and simplified assay steps, this technique will likely have broad utility in nanomaterial-based diagnostics.

Magnetic Nanoparticles and microNMR for Diagnostic Applications

Sensitive and quantitative measurements of clinically relevant protein biomarkers, pathogens and cells in biological samples would be invaluable for disease diagnosis, monitoring of malignancy, and for evaluating therapy efficacy. Biosensing strategies using magnetic nanoparticles (MNPs) have recently received considerable attention, since they offer unique advantages over traditional detection methods. Specifically, because biological samples have negligible magnetic background, MNPs can be used to obtain highly sensitive measurements in minimally processed samples. This review focuses on the use of MNPs for in vitro detection of cellular biomarkers based on nuclear magnetic resonance (NMR) effects. This detection platform, termed diagnostic magnetic resonance (DMR), exploits MNPs as proximity sensors to modulate the spin-spin relaxation time of water molecules surrounding the molecularly-targeted nanoparticles. With new developments such as more effective MNP biosensors, advanced conjugational strategies, and highly sensitive miniaturized NMR systems, the DMR detection capabilities have been considerably improved. These developments have also enabled parallel and rapid measurements from small sample volumes and on a wide range of targets, including whole cells, proteins, DNA/mRNA, metabolites, drugs, viruses and bacteria. The DMR platform thus makes a robust and easy-to-use sensor system with broad applications in biomedicine, as well as clinical utility in point-of-care settings.