15 Smart Platforms for Biomedical Applications
371
for clinical deployment. These approaches may feed into novel iron oxide-based
nanoparticle development with interesting shape and magnetic structures that could
unlock high SAR values while allowing for safe clinical deployment [168, 169]. The
second goal for magnetic hyperthermia has been in establishing a general theoretical
framework. Strong steps forward have been made by creating theoretical models
for the various aspects comprising the whole. This includes modelling hysteresis
processes [170, 171], understanding the role of interparticle dipolar interactions on
the SLP [136–139, 172, 173], and the role of the anisotropy of magnetic particle
aggregates [75, 174]. Developing a theoretical framework that encapsulates the full
complexity of hyperthermia processes, along with a strong push towards optimizing
nanoparticle fabrication within the toxicity restrictions of an in vivo application is
crucial for the commercial future of clinical magnetically driven thermal ablation
techniques. It is expected to be unlikely [175] that magnetic particle hyperthermia
will in the short term be the silver bullet that entirely replaces the more damaging
cancer therapies of chemo and radiotherapy, but it may find applicability in specific
instances of cancer treatment [176, 177].
Diagnostics applications that do not require in vivo deployment of magnetic
nanoparticles allow more flexibility in particle composition as they are not as
restricted by toxicity considerations. This may be of relevance for MR-based
sensing techniques where the sensor detects the stray field from a nanoparticle
as a positive signal. Here, nanoparticle development may be towards developing
techniques that maximize the stray field of the particles while minimizing agglomeration, and developing nanoparticles optimized for detection by MR type sensors
may prove worthwhile [96]. With recent interest in the manipulation of magnetic
beads on chips using the motion of domain walls or patterned magnetic structures [140–145, 178, 179], there is potentially an alternative to microfluidic-based
approaches to biomolecule capture, transport and detection. Combined with optical,
electrical or magnetic sensing-based approaches, this is an interesting way forward
for nanoparticle techniques in the biosensing space.
In addition to colloidally synthesized magnetic nanoparticles, lithographically
defined structures for biotechnology applications have also been discussed here. The
attraction of lithographically defined microdiscs is the ability to engineer magnetic
particles with a precision that is simply not offered by colloidal chemistry fabrication
techniques [99]. By being able to finely tune the size and shape of the discs, as well
as the amount of magnetic material, and the strength and orientation of the magnetic
anisotropy, local forces and torques may be applied with a high degree of control.
This is particularly relevant in cell manipulation for downstream responses as cellular
processes may be triggered by mechanical stimulation. For cancer cell death, for
example, torques in the range of aNm may trigger apoptotic cell death [36] via ion
channel mediation, a mechanism that does not trigger an inflammatory response in
the body and is important for treatments in the brain.
While work thus far has focussed on their use in therapy type applications, it will
be worthwhile to explore the potential of lithographically defined particles in labon-chip-type systems. A need for the controlled manipulation of magnetic particles
on chip may better suit the lower fabrication yields and precisely tunable magnetic
371
for clinical deployment. These approaches may feed into novel iron oxide-based
nanoparticle development with interesting shape and magnetic structures that could
unlock high SAR values while allowing for safe clinical deployment [168, 169]. The
second goal for magnetic hyperthermia has been in establishing a general theoretical
framework. Strong steps forward have been made by creating theoretical models
for the various aspects comprising the whole. This includes modelling hysteresis
processes [170, 171], understanding the role of interparticle dipolar interactions on
the SLP [136–139, 172, 173], and the role of the anisotropy of magnetic particle
aggregates [75, 174]. Developing a theoretical framework that encapsulates the full
complexity of hyperthermia processes, along with a strong push towards optimizing
nanoparticle fabrication within the toxicity restrictions of an in vivo application is
crucial for the commercial future of clinical magnetically driven thermal ablation
techniques. It is expected to be unlikely [175] that magnetic particle hyperthermia
will in the short term be the silver bullet that entirely replaces the more damaging
cancer therapies of chemo and radiotherapy, but it may find applicability in specific
instances of cancer treatment [176, 177].
Diagnostics applications that do not require in vivo deployment of magnetic
nanoparticles allow more flexibility in particle composition as they are not as
restricted by toxicity considerations. This may be of relevance for MR-based
sensing techniques where the sensor detects the stray field from a nanoparticle
as a positive signal. Here, nanoparticle development may be towards developing
techniques that maximize the stray field of the particles while minimizing agglomeration, and developing nanoparticles optimized for detection by MR type sensors
may prove worthwhile [96]. With recent interest in the manipulation of magnetic
beads on chips using the motion of domain walls or patterned magnetic structures [140–145, 178, 179], there is potentially an alternative to microfluidic-based
approaches to biomolecule capture, transport and detection. Combined with optical,
electrical or magnetic sensing-based approaches, this is an interesting way forward
for nanoparticle techniques in the biosensing space.
In addition to colloidally synthesized magnetic nanoparticles, lithographically
defined structures for biotechnology applications have also been discussed here. The
attraction of lithographically defined microdiscs is the ability to engineer magnetic
particles with a precision that is simply not offered by colloidal chemistry fabrication
techniques [99]. By being able to finely tune the size and shape of the discs, as well
as the amount of magnetic material, and the strength and orientation of the magnetic
anisotropy, local forces and torques may be applied with a high degree of control.
This is particularly relevant in cell manipulation for downstream responses as cellular
processes may be triggered by mechanical stimulation. For cancer cell death, for
example, torques in the range of aNm may trigger apoptotic cell death [36] via ion
channel mediation, a mechanism that does not trigger an inflammatory response in
the body and is important for treatments in the brain.
While work thus far has focussed on their use in therapy type applications, it will
be worthwhile to explore the potential of lithographically defined particles in labon-chip-type systems. A need for the controlled manipulation of magnetic particles
on chip may better suit the lower fabrication yields and precisely tunable magnetic