Design and Development of In Vivo Sensor Systems: The Long and Tortured Road to a Self-Contained, Implantable Glucose Sensor for Diabetes Management - Designing Receptors for the Next Generation of Biosensors - page 213

Bloodstream
Glucose

Bliocompatible
Membrane

Glucose Sensor Response Curve

120
100
80
60
40
20
0

GLUCOSE LOW

Competition
/Signaling
Component
DBA

GLUCOSE SAFE

Glucose
Competitive
Binding
Environment
iDIOL

GLUCOSE HIGH

0 5 10
Glucose Concentration (Arbitrary Units)

15 20 25 30

Signal Transduction and RFID Electronics

Fig. 3 Sensing system components. The glucose sensing system includes the glucose-competitive
DBA binding environment (iDIOL) and the competition/signaling component (DBA). The system
will produce a response proportionate to the bloodstream glucose levels. The readout will be one of
three messages: LOW, SAFE, HIGH, which correspond to adult glucose levels of below 70 mg/dL,
between 70 and 130 mg/dL and above 130 mg/dL, respectively, as they pertain to fasting glucose
levels (American Diabetes Association 2010)

may require more advanced sensing component materials in order to substantially
increase sensitivity and selectivity due to the complexity of the sample matrix and
the inherently low analyte concentration that can exist in a physiological system
[ 43 ]. The approach of utilizing synthetic materials for the construction of chemical
recognition systems provides the structural and functional materials required for
effective and robust sensing/receptor function [ 54 ]. Developing synthetic recogni-
tion materials with known physical and chemical properties provides the advantage
of flexibility in selecting compatible sensing system reagents that meet the design
criteria for operation within a physiological environment. It is critical that the
reagents simultaneously function in complex, aqueous media while maintaining
performance integrity under physiological pH and temperature [ 54 ]. It is also
imperative that the materials not only preserve sensitivity and selectivity within
complicated matrices of potentially competing analytes, but also retain sensitivity
for a particular moiety whose physiological concentration may be low. The design
challenges of an in vivo sensing system can be overcome using synthetically
optimized recognition materials.
The applicability of artificial receptor materials to the development of saccharide
sensors, especially as it relates to glucose detection, has attracted a great deal of
interest [ 55 - 58 ]. Efforts to improve signaling technology continue to make head-
way because materials with enhanced biocompatibility and superior sensitivity and
selectivity toward glucose are fundamental requirements for monitoring glucose
levels in an implantable device. Our group has developed a sensing system tech-
nology for in vivo glucose analysis that utilizes synthetically optimized materials to
fulfill the reagent requirements of a self-contained and closed-cycle, stable glucose