Biomedical Engineering Reference
In-Depth Information
variuos agents to be
released
biodegradable
polymeric
substrate
seal
layer
reservoirs with
biodegradable
membranes
Fig. 4.5
The controlled polymer drug delivery system
accelerator mass spectrometer. In in vivo experiments, drug delivery follows the
electrochemical dissolution of the gold membranes placed on top of the reservoirs.
These experiments have indicated that the device displayed in Fig. 4.1 is able to
deliver various drugs with precise profiles in localized places. The role of the RF
emitter is played by 14 C. The need to eliminate such a MEMS drug delivery device
from the body is fulfilled by a biodegradable polymer chip, which contains an array
of microreservoirs terminated with different resorbable membranes. The drugs to be
released are placed in microreservoirs, as illustrated in Fig. 4.5 ( Grayson et al. 2003 ).
A similar drug release device is based on a MEMS-like polymer that seals the
drug reservoir and contracts or expands, similar to a muscle, in the presence of an
electric signal emitted by an electronic circuit ( Staples et al. 2006 ). In this way, in
a single-reservoir device, the contained drug is released with targeted kinetics when
the biosensor is triggered by a certain electric signal. This device is displayed in
Fig. 4.6 .
The next generation of stents, which are made from metals, will be integrated
with microprobes to allow the delivery of antirestenosis or other types of drugs. A
micromachined stent is acting as an antenna for wireless control of microprobes.
An inductive stent antenna, as that in Fig. 4.7 , with a total length of 20 mm and a
diameter of 3.5 mm is loaded with a capacitor. The stent can be thus interrogated via
wireless signals. The antenna is integrated with sensors to measure the changes in
pressure and flow of blood ( Takahata et al. 2006 ).
Wireless techniques are widespread in modern biochips and implants. For
example, wireless capsule endoscopy is among the most advanced techniques to
assess the mucosa of the gastrointestinal tract ( Moglia et al. 2007 ). The basic
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