4 research outputs found
More than magnetic isolation: Dynabeads as strong Raman reporters towards simultaneous capture and identification of targets
Dynabeads are superparamagnetic particles used for immunomagnetic
purification of cells and biomolecules. Post-capture, however, target
identification relies on tedious culturing, fluorescence staining and/or target
amplification. Raman spectroscopy presents a rapid detection alternative, but
current implementations target cells themselves with weak Raman signals. We
present antibody-coated Dynabeads as strong Raman reporter labels whose effect
can be considered a Raman parallel of immunofluorescent probes. Recent
developments in techniques for separating target-bound Dynabeads from unbound
Dynabeads makes such an implementation feasible. We deploy Dynabeads
anti-Salmonella to bind and identify Salmonella enterica, a major foodborne
pathogen. Dynabeads present signature peaks at 1000 and 1600 1/cm from
aliphatic and aromatic C-C stretching of polystyrene, and 1350 1/cm and 1600
1/cm from amide, alpha-helix and beta-sheet of antibody coatings of the Fe2O3
core, confirmed with electron dispersive X-ray (EDX) imaging. Their Raman
signature can be measured in dry and liquid samples even at single shot ~30 x
30-micrometer area imaging using 0.5 s, 7 mW laser acquisition with single and
clustered beads providing a 44- and 68-fold larger Raman intensity compared to
signature from cells. Higher polystyrene and antibody content in clusters
yields to the larger signal intensity and conjugation to bacteria strengthens
clustering as a bacterium can bind to more than one bead as observed via
transmission electron microscopy (TEM). Our findings shed light on the
intrinsic Raman reporter nature of Dynabeads, demonstrating their dual function
for target isolation and detection without additional sample preparation,
staining, or unique plasmonic substrate engineering, advancing their
applications in heterogeneous samples like food, water, and blood.Comment: 35 pages, 19 figures, submitted to the Journal of Raman Spectroscop
Predicting tuberculosis drug resistance with machine learning-assisted Raman spectroscopy
Tuberculosis (TB) is the world's deadliest infectious disease, with 1.5
million annual deaths and half a million annual infections. Rapid TB diagnosis
and antibiotic susceptibility testing (AST) are critical to improve patient
treatment and to reduce the rise of new drug resistance. Here, we develop a
rapid, label-free approach to identify Mycobacterium tuberculosis (Mtb) strains
and antibiotic-resistant mutants. We collect over 20,000 single-cell Raman
spectra from isogenic mycobacterial strains each resistant to one of the four
mainstay anti-TB drugs (isoniazid, rifampicin, moxifloxacin and amikacin) and
train a machine-learning model on these spectra. On dried TB samples, we
achieve > 98% classification accuracy of the antibiotic resistance profile,
without the need for antibiotic co-incubation; in dried patient sputum, we
achieve average classification accuracies of ~ 79%. We also develop a low-cost,
portable Raman microscope suitable for field-deployment of this method in
TB-endemic regions
Biotemplating pores with size and shape diversity for Li-oxygen Battery Cathodes
Synthetic porogens provide an easy way to create porous structures, but their usage is limited due to synthetic difficulties, process complexities and prohibitive costs. Here we investigate the use of bacteria, sustainable and naturally abundant materials, as a pore template. The bacteria require no chemical synthesis, come in variable sizes and shapes, degrade easier and are approximately a million times cheaper than conventional porogens. We fabricate free standing porous multiwalled carbon nanotube (MWCNT) films using cultured, harmless bacteria as porogens, and demonstrate substantial Li-oxygen battery performance improvement by porosity control. Pore volume as well as shape in the cathodes were easily tuned to improve oxygen evolution efficiency by 30% and double the full discharge capacity in repeated cycles compared to the compact MWCNT electrode films. The interconnected pores produced by the templates greatly improve the accessibility of reactants allowing the achievement of 4,942 W/kg (8,649 Wh/kg) at 2 A/ge (1.7 mA/cm2)