Accurate glucose detection in a small etalon
2010
We are developing a continuous glucose monitor for subcutaneous long-term
implantation. This detector contains a double chamber Fabry-Perot-etalon that
measures the differential refractive index (RI) between a reference and a
measurement chamber at 850 nm. The etalon chambers have wavelength
dependent transmission maxima which dependent linearly on the RI of their
contents. An RI difference of un=1.5·10 -6 changes the spectral position of a
transmission maximum by 1pm in our measurement. By sweeping the
wavelength of a single-mode Vertical-Cavity-Surface-Emitting-Laser (VCSEL)
linearly in time and detecting the maximum transmission peaks of the etalon we
are able to measure the RI of a liquid. We have demonstrated accuracy of
un=±3.5·10 -6 over a un-range of 0 to 1.75·10 -4 and an accuracy of 2% over a unrange
of 1.75·10 -4 to 9.8·10 -4 . The accuracy is primarily limited by the reference
measurement.
The RI difference between the etalon chambers is made specific to glucose by
the competitive, reversible release of Concanavalin A (ConA) from an
immobilized dextran matrix. The matrix and ConA bound to it, is positioned
outside the optical detection path. ConA is released from the matrix by reacting
with glucose and diffuses into the optical path to change the RI in the etalon.
Factors such as temperature affect the RI in measurement and detection
chamber equally but do not affect the differential measurement. A typical
standard deviation in RI is ±1.4·10 -6 over the range 32°C to 42°C. The detector
enables an accurate glucose specific concentration measurement.
Keywords:
- Correction
- Source
- Cite
- Save
- Machine Reading By IdeaReader
0
References
0
Citations
NaN
KQI