Page 559 - Book Hosokawa Nanoparticle Technology Handbook

27 DEVELOPMENT OF THE THERMORESPONSIVE MAGNETIC NANOPARTICLE APPLICATIONS
APPLICATION 27

27 DEVELOPMENT OF THE THERMORESPONSIVE MAGNETIC NANOPARTICLE AND
ITS DEPLOYMENT IN THE BIOTECHNOLOGY FIELD

1. Magnetic nanoparticle material polymers responding to external stimuli, including
temperature, light, electric field, and pH, are immobi-
Among granular materials, magnetic microparticle lized. For example, Fig. 27.1 shows thermoresponsive
material has been widely used in the biotechnology magnetic nanoparticles where magnetic nanopolymers
field [1, 2]. A further increase in its use is also are coated with thermoresponsive polymers. In these
expected in a variety of fields, such as biosepara- particles, coagulation and distribution conditions vary,
tion, various assays, diagnosis methods, and drug responding to changes in stimuli through the hydration–
delivery systems (DDS). However, the size of the dehydration of polymers or varied interaction between
micro-magnetic particles conventionally used is polymers according to the temperature change (details
around several micrometers [3]. to be described later).
Reducing the particles to nanosize will dramati- Accordingly, coagulating magnetic nanoparticles
cally increase the adsorption amount available for by temperature change will enable rapid collection by
separation because of their increased surface area magnets. In other words, these particles will become
for mutual interactions, resulting in a remarkable innovative material that can be rapidly separated mag-
improvement in analytical sensitivity. This size netically, even when nanosized [4–6].
reduction facilitates rapid and highly sensitive diag-
nosis, and the nanomaterial has become useful to
establish high-throughput screening systems (HTS), 2. What is a thermoresponsive polymer?
typically like those for proteome analysis, for various
types and kinds of proteins. However, making the Thermoresponsive polymers, which vary their physical
particle diameter smaller than several hundred properties reversibly and discontinuously when
nanometers will weaken their magnetism, which exposed to slight temperature change, respond to such
hampers separation using magnets. general stimulus as temperature changes. Accordingly,
To solve this dilemma, we have developed stimuli- many studies on their application, including actuators,
responsive magnetic nanoparticles, on whose surface separating agents, and DDS agents, are underway,

Hyperthermia
The smaller particle size is desirable
because of its larger surface area.
However, overly compact particles
cannot be separated magnetically.
Conventional magnetic nanoparticles

Modification by thermoresponsive polymers

C n o i t a l u g a o R y r e v o c e

Temperature Magnetic
change separation
Thermoresponsive magnetic Magnet
nanoparticles

Figure 27.1
Thermoresponsive magnetic nanoparticles.

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