5 research outputs found
Mechanism of Magnetic Relaxation Switching Sensing
Magnetic relaxation switching (MRSw) assays that employ target-induced aggregation (or disaggregation) of magnetic nanoparticles (MNPs) can be used to detect a wide range of biomolecules. The precise working mechanisms, however, remain poorly understood, often leading to confounding interpretation. We herein present a systematic and comprehensive characterization of MRSw sensing. By using different types of MNPs with varying physical properties, we analyzed the nature and transverse relaxation modes for MRSw detection. The study found that clustered MNPs are universally in a diffusion-limited fractal state (dimension of ∼2.4). Importantly, a new model for transverse relaxation was constructed that accurately recapitulates observed MRSw phenomena and predicts the MRSw detection sensitivities and dynamic ranges
Ubiquitous Detection of Gram-Positive Bacteria with Bioorthogonal Magnetofluorescent Nanoparticles
The ability to rapidly diagnose gram-positive pathogenic bacteria would have far reaching biomedical and technological applications. Here we describe the bioorthogonal modification of small molecule antibiotics (vancomycin and daptomycin), which bind to the cell wall of gram-positive bacteria. The bound antibiotics conjugates can be reacted orthogonally with tetrazine-modified nanoparticles, <i>via</i> an almost instantaneous cycloaddition, which subsequently renders the bacteria detectable by optical or magnetic sensing. We show that this approach is specific, selective, fast and biocompatible. Furthermore, it can be adapted to the detection of intracellular pathogens. Importantly, this strategy enables detection of entire classes of bacteria, a feat that is difficult to achieve using current antibody approaches. Compared to covalent nanoparticle conjugates, our bioorthogonal method demonstrated 1–2 orders of magnitude greater sensitivity. This bioorthogonal labeling method could ultimately be applied to a variety of other small molecules with specificity for infectious pathogens, enabling their detection and diagnosis
Nanoparticle-Mediated Measurement of Target–Drug Binding in Cancer Cells
Responses to molecularly targeted therapies can be highly variable and depend on mutations, fluctuations in target protein levels in individual cells, and drug delivery. The ability to rapidly quantitate drug response in cells harvested from patients in a point-of-care setting would have far reaching implications. Capitalizing on recent developments with miniaturized NMR technologies, we have developed a magnetic nanoparticle-based approach to directly measure both target expression and drug binding in scant human cells. The method involves covalent conjugation of the small-molecule drug to a magnetic nanoparticle that is then used as a read-out for target expression and drug-binding affinity. Using poly(ADP-ribose) polymerase (PARP) inhibition as a model system, we developed an approach to distinguish differential expression of PARP in scant cells with excellent correlation to gold standards, the ability to mimic drug pharmacodynamics <i>ex vivo</i> through competitive target–drug binding, and the potential to perform such measurements in clinical samples
Nanomagnetic System for Rapid Diagnosis of Acute Infection
Pathogen-activated antibody-secreting
cells (ASCs) produce and secrete antigen-specific antibodies. ASCs
are detectable in the peripheral blood as early as 3 days after antigen
exposure, which makes ASCs a potential biomarker for early disease
detection. Here, we present a magnetic capture and detection (MCD)
assay for sensitive, on-site detection of ASCs. In this approach,
ASCs are enriched through magnetic capture, and secreted antibodies
are magnetically detected by a miniaturized nuclear magnetic resonance
(μNMR) system. This approach is based entirely on magnetics,
which supports high contrast against biological background and simplifies
assay procedures. We advanced the MCD system by (i) synthesizing magnetic
nanoparticles with high magnetic moments for both cell capture and
antibody detection, (ii) developing a miniaturized magnetic device
for high-yield cell capture, and (iii) optimizing the μNMR assay
for antibody detection. Antibody responses targeting hemolysin E (HlyE)
can accurately identify individuals with acute enteric fever. As a
proof-of-concept, we applied MCD to detect antibodies produced by
HlyE-specific hybridoma cells. The MCD achieved high sensitivity in
detecting antibodies secreted from as few as 5 hybridoma cells (50
cells/mL). Importantly, the assay could be performed with whole blood
with minimal sample processing
Integrated Kidney Exosome Analysis for the Detection of Kidney Transplant Rejection
Kidney
transplant patients require life-long surveillance to detect
allograft rejection. Repeated biopsy, albeit the clinical gold standard,
is an invasive procedure with the risk of complications and comparatively
high cost. Conversely, serum creatinine or urinary proteins are noninvasive
alternatives but are late markers with low specificity. We report
a urine-based platform to detect kidney transplant rejection. Termed
iKEA (integrated kidney exosome analysis), the approach detects extracellular
vesicles (EVs) released by immune cells into urine; we reasoned that
T cells, attacking kidney allografts, would shed EVs, which in turn
can be used as a surrogate marker for inflammation. We optimized iKEA
to detect T-cell-derived EVs and implemented a portable sensing system.
When applied to clinical urine samples, iKEA revealed high level of
CD3-positive EVs in kidney rejection patients and achieved high detection
accuracy (91.1%). Fast, noninvasive, and cost-effective, iKEA could
offer new opportunities in managing transplant recipients, perhaps
even in a home setting