Biomedical Engineering Reference
In-Depth Information
photoelectric cell through an interference i lter with maximum band-pass
at 520 nm (12). h e signal from each photoelectric cell (15) enters the two-
channel photon counter and is then passed to the two-channel recorder
(16) through the analogous transformer. To remove artifacts caused by
instability of the light source, part of the laser rays rel ected on the l at
parallel plate is arranged by lenses (3) and with the help of i ber light con-
ductors (4) reaches the photodiode (5). h e photodiode signal is amplii ed
and registered by a voltmeter (7) and recorder (8).
h e value of the specii c signal (B) is calculated as follows: B = (I -I
0
)/I,
where I - maximum value of the signal, I
0
- the light background of pho-
toelectric cell. An optrode is i xed at the distal end only. It permits rapid
replacement of them and maximum use of the energy of the evanescent
wave. h e 1.6-mm inner diameter of the microcell provides a usable capac-
ity of up to 20 μl. For such a biosensor, we used an argon laser as the light
source as well as the optrodes from quartz optic i bers (diameter 1.3 mm,
length 60 mm). In experiments we have taken phenatoine, lidocaine, spe-
cii c Ab to them and as well as they labeled forms by FITC. All operations
were carried out at the room temperature.
h e optic i bers were pretreated as follows:
• First, to form a high concentration of hydroxylic groups
on the surface the optrodes were immersed in hot acetone
for 5 min. h en, these glass i bers were boiled in water for
5 h. To obtain uniformly distributed active groups on the
surface the optrodes were treated with 2% monofunctional
4-aminobutyldimethylmethoxysilane in acetone for 40 min
at 60
0
C. At er washing with distilled water the optrode sur-
face was activated by 5% GA at pH 6.8 for 40 min. h en the
optrodes were washed carefully in 0.05 M PhB, pH 7.2. For
immobilization of the Ab the optrodes with the modii ed
surface were immersed for about 1 h into a solution contain-
ing 500 ng/ml of the mixture (1:l) of the Ab to phenatoine
and lidocaine prepared in the PhB mentioned above. h e
remaining free functional dialdehyde groups were blocked
by a 0.1 M glycine solution for 40 min. Finally, the optrodes
were washed with 0.05 M PhB, pH 7.2 and dried in air.
h e concentrations of the determined substances are estimated by the
competitive method. In this case a sample containing equal volumes of
control and analyzed solution is introduced into the microcell. As refer-
ence samples we used phenatoine labeled with FITC and lidocaine labeled
with B-Phyco which were diluted 1:20. h e solution for the calibration
