ac0c01733_si_002.mp4 (15.56 MB)
Trace Biomolecule Detection with Functionalized Janus Particles by Rotational Diffusion
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posted on 2020-09-25, 21:07 authored by Wei-Long Chen, Han-Sheng ChuangCytokines are small
proteins secreted by cells in innate and adaptive
immune systems. Abnormal cytokine secretion is often regarded as an
early cue of dysregulation of homeostasis due to diseases or infections.
Early detection allows early medical intervention. In this study,
a natural phenomenon called rotational Brownian motion was characterized
by Janus particles and its potential use in detection of trace biomolecules
explored. Through the functionalization of the Janus particles with
an antibody, the target cytokine, that is, tumor necrosis factor-α,
was measured in terms of rotational diffusion. Rotational diffusion
is highly sensitive to the particle volume change according to the
Stokes–Einstein–Debye relation and can be quantified
by blinking signal. Accordingly, 1 μm half-gold and half-fluorescent
microbeads were conjugated with 200 nm nanobeads through sandwiched
immunocomplexes. The light source, lead time for stabilization, and
purification were investigated for optimization. Particle images can
be captured with green light at 5 Hz within 300 s. Under such conditions,
the functionalized Janus particles eventually achieved a limit of
detection of 1 pg/mL. The rotational diffusometry realized by Janus
particles was power-free and feasible for ultrasensitive detection,
such as early disease detection.