Biomedical Engineering Reference
In-Depth Information
Ham, demonstrated the capability of signifi cantly downsizing the spectrometer.
Although, prior to the studies of Y. Liu
et al.
, single PCB spectrometers had
been demonstrated [129-131], in order for MRSw biosensor detectors to
achieve the size, cost, and range of applications of conventional portable electron-
ics, it was necessary to downsize the entire magnetic resonance spectrometer
to the scale of an integrated circuit (IC). The studies of Liu
et al.
represented the
most signifi cant steps towards achieving this, by showing that the heart of a spec-
trometer - the transceiver - could be hosted on an IC. The CMOS design of Liu
et al.
was able to transmit and receive RF pulses to and from a detection coil [132],
although a similar performance was reported (in terms of sensitivity) to that
achieved by Lee
et al.
with a transceiver built from off-the-shelf, discrete compo-
nents. The RF transceiver of Liu
et al.
has proved to be one of the smallest trans-
ceiver units reported to date [132]. The integration of other spectrometer
components should enable an extremely small complete magnetic resonance
spectrometer.
These breakthroughs in magnetic resonance detection instrumentation suggest
that this technology can be tailored to biosensor applications that require down-
sized and portable readers. In fact, efforts are currently under way at T2 Biosys-
tems to produce completely integrated, portable MRSw biosensor readers that
would most likely consist of a relaxometer (magnet, detection coil, and spectrom-
eter) as well as a user interface, power source, and connection to external data
networks. Depending on the application, the MRSw biosensor reader may also
provide sample incubation, disposable cartridge reading and handling, and fl uidics
actuation. Recently, a team from T2 Biosystems, led by P. Prado, introduced a
shoebox-sized, fully integrated relaxometer that weighs less than 4kg [73], and
consists of a 0.5T magnet, spectrometer, operating system, touchscreen user
interface, and DC power input. Additional investigations at T2 Biosystems have
demonstrated the capability of further downsizing a 0.5 T magnet unit to be 10 000-
fold smaller than a commercial bench-top magnet and probehead units [73], by
means of an extremely low-cost magnet and coil architecture. Moreover, when
using this prototype magnet and microcoil, MRSw biosensor- mediated measure-
ments of hCG protein were conducted at femtomolar levels, in nanoliter sample
volumes. Due to the range of application of these MRSw biosensor tests, and the
recent and ongoing breakthroughs in the downsizing of instruments, continued
development will in time surely enable the deployment of MRSw biosensors
within virtually any setting, and for virtually any target.
Acknowledgments
The author acknowledges the T2 Biosystems team and expresses his gratitude to
those who provided helpful feedback for this chapter, including Lee Josephson,
Sonia Taktak, Hakho Lee, Pablo Prado, Vicky Demas, Kim Foster, and Sonia
Kumar. The author also acknowledges the many hours of relinquished time from
Sherri, Sophia, and Henry Lowery.
