(163f) Developing Janus Particles Enabled Rotational Diffusometry for High-Sensitive Diabetic Retinopathy Detection | AIChE

(163f) Developing Janus Particles Enabled Rotational Diffusometry for High-Sensitive Diabetic Retinopathy Detection


Chen, W. L. - Presenter, National Cheng Kung University
Chuang, H. S., National Cheng Kung University

Developing Janus Particles Enabled
Rotational Diffusometry for High-Sensitive Diabetic Retinopathy Detection

Wei-Long Chen1, and
Han-Sheng Chuang1
,2 *


Department of Biomedical Engineering

National Cheng Kung University, Tainan 701,

2 Center for Micro/Nano Science and

National Cheng Kung University,
Tainan 701, Taiwan.

Abstract- Brownian motion is a natural phenomenon in which tiny particles display
random motion in fluids. Nevertheless, the diffusion of particles is
proportional to temperature and viscosity but inversely proportional to radius
of particles according to the Stokes-Einstein equation [1]. Based on this
principle, diffusometry has been applied to detect fluid temperature, fluid
viscosity, and particle dimeter. Recently, this technique has been extended to
biomedical fields, such as investigation of microorganism motility [1] and rapid
diagnosis of diseases with specific biomarkers [2]. Despite the above mentioned
advantages, the conventional diffusometry is incapable of detecting
low-abundance analytes. Unlike translational Brownian motion, rotational
Brownian motion emerges a more sensitive response to the particle size.
According to Stokes-Einstein Debye equation [3], the rotational diffusion of
the particles is inversely proportional to the cubic radius of the
particles under the consistent temperature and viscosity of fluid. In this paper, we aimed to diagnose DR
with a selective biomarker, tumor necrosis factor alpha (TNF-ɑ), in the early diagnose. Past
literature [4] has reported that TNF-ɑ is one of the biomarker proteins
associated with DR in human tear. In this research, we developed a
novel technique for sensing target proteins based on rotational Brownian motion using Janus particles. Only
a small sample volume (~2
µL) was required (Figure 1A). Janus particles were fabricated by coating
half of fluorescent polystyrene (PS) beads with a gold film, and purified with a
disk filter. Taking the advantage of the characteristic of half gold/
fluorescence surface, the rotational Brownian motion signal was expressed
through blinking intensity. In the preparation of functionalized particles,
polyclonal antibodies were conjugated with functional submicron-sized PS
particles by EDC and NHS, while monoclonal antibodies were conjugated on the
gold side of Janus particles. As TNF-ɑ
was present in the sample, submicron-sized PS particles would attached to Janus
particles to form a sandwich immunocomplex, resulting in a change of rotational
Brownian motion. A parameter, correlation time, was used to quantify the
cross-correlation intensity of Janus particles [5]. The correlation time was
observed to significantly increase with TNF-ɑ. The
results showed that the correlation time of the immunocomplexed Janus particles
was longer than that of pure Janus particles. The present limit of detection
of the technique could achieve 10 ng/mL (Figure 1B). The Janus particles enabled rotational
diffusometry was herein proven to be a prospective diagnostic for more other
protein detections in the future.

Janus particles, TNF-ɑ, Rotational Brownian motion, Protein detection,
Biosensor, Immuno-sensing, Diffusometry

Figure 1: The experimental setup and results. (A)
The experimental schematic. TNF-ɑ antigen and functionalized submicron size PS
particles were incubated with functionalized Janus particles to form the
immunocomplex. Rotational Brownian motion could be examined under microscope.
Correlation time could be estimated from the correlation intensity of Janus
particles by computer. (B) The correlation time of different condition. The
result show that the significantly increase with concentration of TNF-ɑ. There
is no significant difference when lack of submicron PS particles and TNF-ɑ
antigen compare to the pure Janus particles.


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