Biomedical Engineering Reference
In-Depth Information
complicated invasive surgery. In this light, miniaturization of all the components of
the sensor, such as the power source, signal processing units, sensory elements, and
electrodes, becomes essential. Currently, carbon nanofibers and ultrathin Pt wires
are used for the fabrication of miniaturized electrodes [
33
,
34
]. The electrocatalytic
properties of these electrodes can be further improved by incorporating metal
nanoparticles [
35
], furthering neuroscience research on nerve stimulation [
36
],
acute pain [
37
], and implantable drug-delivery systems [
38
]. Another prospect for
sensor miniaturization resides in top-down nanofabrication techniques such as
photolithography, dip-pen nanolithography, and micromachining. Etching pro-
cesses and photolithography permit the creation of needle-shaped biosensors for
glucose monitoring [
39
,
40
] that can be produced on an industrial scale. What is
more, carbon nanotubes [
41
], nanorods [
42
,
43
], nanowires [
44
], and semiconduct-
ing polymers [
45
] are used to develop sensors based on changes to gate conductance
[
46
], hysteresis [
47
], or threshold voltage [
48
].
Conclusively, it is imperative to develop implantable biosensors for the simulta-
neous detection of multiple interdependent metabolites in order to increase confi-
dence in the results obtained and to assist in early disease detection.
Multidisciplinary fields of nanotechnology can bring about the development of
highly sensitive, multi-analyte sensors.
1.2.2 Nanosurgery
The advent of lasers in the early 1960s changed the face of surgery by making it
possible to ablate biological tissue with high precision and minimal invasiveness. It
is now possible to perform highly targeted manipulation and ablation at the
nanoscale impacting the fields of developmental biology, cellular biology, and
assisted reproductive technologies. Ultrashort laser pulses at the picosecond and
femtosecond scale are increasingly used in biological applications, such as manip-
ulation and dissection of individual cells in tissue [
49
-
51
], ablation of structures
and organelles inside a living cell [
52
,
53
], or modification of a medical implant
[
54
]. Recently, femtosecond lasers in combination with gold nanoparticles have
been used as a means for virus-free transfection method of human cancer melanoma
cells [
55
].
Moreover, an array of fuel-powered and fuel-free microscale motors have
recently been developed for multiple biomedical applications, such as directed
drug delivery, biopsy, and precision nanosurgery [
56
,
57
]. Chemically powered
nanoscale motors based on the catalytic breakdown of a solution fuel, such as
hydrogen peroxide, have gathered much attention [
58
-
60
]. Motion control of
nanomotors has been enabled by magnetically managing their directionality and
adjusting their speed using different stimuli [
61
,
62
]. Fuel-free nanometers are
based on externally applied magnetic fields and include helical microstructures
and flexible or tumbling nanowires. While remarkable progress has been made
regarding the development of nanoscale engines, much improvement needs to be
