Biomedical Engineering Reference
In-Depth Information
• Compatible with some organic solvents (acetone, alcohols, aromat-
ics, etc.).
• Sol-gel material chosen over typical polymer method, allowing
for faster response time, versatility in the desired dopants, greater
chemical compatibility, flexible coating, and enhanced thermal and
optical performance.
• Indicator molecule allows high-resolution measurement in biologi-
cal range (pH 5-9).
• Simplified algorithm takes analytical and baseline wavelengths into
account to reduce errors caused by optical shifts.
The TruFluor™ (
www.inesse.com
) DO and temperature sensor is a single-
use solution consisting of a disposable sheath, an optical reader, and a trans-
mitter. The single-use sheath can be preinserted in a disposable bioreactor
bag port and irradiated with the bag to both preserve and guarantee the ster-
ile barrier. All wetted materials of the sheath are USP class VI compliant. The
optical reader utilizes an light emitting diode (LED) and a large area photodi-
ode with integrated optical filtering that minimizes photodegradation of the
acting sensing element. The design has been optimized to provide accurate
in situ measurement of dissolved oxygen using phase fluorometric detection
in real time. The temperature measurement leverages a 316 L stainless steel
thermal window embedded in the sheath and provides a highly accurate tem-
perature measurement that can be used as a process variable or for tempera-
ture compensation.
Carbon dioxide sensors work on the principle of measure pH of a carbon-
ate buffer embedded in a CO
2
-permeable membrane. The reaction time of
the sensors is long, and the use of quaternary ammonium hydroxide has
been made to achieve a faster response. Fluorescence-based sensors are
attractive as they facilitate the development of portable and low-cost sys-
tems that can be easily deployed outside the laboratory environment. The
sensor developed for this work exploits a pH fluorescent dye 1-hydroxy-
pyrene-3,6,8-trisulfonic acid, ion-paired with cetyltrimethylammonium
bromide (HPTS-IP), which has been entrapped in a hybrid sol-gel-based
matrix derived from
n
-propyltriethoxysilane along with the lipophilic
organic base. The probe design involves the use of dual-LED excitation in
order to facilitate ratiometric operation and uses a silicon P-type intrinsic
n-type (PIN) photodiode. HPTS-IP exhibits two pH-dependent changes in
excitation bands, which allows for dual-excitation ratiometric detection as
an indirect measure of the pCO2. Such measurements are insensitive to
changes in dye concentration, leaching, and photobleaching of the fluoro-
phore and instrument fluctuations unlike unreferenced fluorescence inten-
sity measurements. The performance of the sensor system is characterized
by a high degree of repeatability, reversibility, and stability.
