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The porphyrin handbook - Kadish K.M.

Kadish K.M. The porphyrin handbook - Academic press, 2000. - 368 p.
Download (direct link): kadishsmishgulilard2000.djvu
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lead with silver epoxy cement. The polymeric porphyrinic film is
deposited on a single carbon fiber from a solution 5x10"4 M monomeric
(TMHPP)Nin, or (1,10-phen)(TMHPP)2Ni(II) or (PUP)-Ni(II) using cyclic
scanning of potential (Table 3) with a scan rate of 100 mV/s for 10-30
scans. The optimal surface coverage of polymeric film is in the range of
0.8-1.5 nmol cm-2. Dip-coating the dried polymeric porphyrin/ carbon-
fiber tip (3 -4 times, 5 second) in 1 % Nafion in ethanol produces a thin
anionic film that repels or retards charged ionic species while allowing
the small neutral and hydrophobic NO molecule access to the underlying
catalytic surface. Thickness of the Nafion layer should be 0.1-0.3 .
2. Catheter-Protected Sensors
For in vivo and in vitro measurements of NO in tissue and blood, a
catheter-protected porphyrinic NO sensor is constructed from the needle
of a 22-gauge 25 -long intravenous catheter-needle unit truncated and
polished flat so that it was 5 mm shorter than a 22-gauge catheter.65 68
75'80 A bundle of seven carbon fibers (each 7 diameter, protruding 5
mm) is mounted inside the hollow tmncated 22-gauge needle with conducting
epoxy cement. After
246
Malinski
Tabie 3. Optimum Conditions for Preparation of Porphyrinic Sensor for
Detection of Nitric Oxide
Process Materials Parameters
Supporting material Carbon fiber 6-8 diameter
preparation 6-7 cm length
Reduction of carbon Microburner 800-1000C
fiber diameter
Deposition of Monomeric (1-5) x 10 ~4M
polymeric porphyrin NiTMHPP in 0.1 M NaOH
Voltage range 0.00-1.00 V
Scan rate 0.1 V s 1
Number of scans 10-18
Deposition of Nafion Nafion solution 3% (w/v)
in alcohol
Time 2-5 s
Drying time 10-15 min
Determination of NO Amperometry 0.68 V
Differential pulse 0.40-0.70 V
voltammetry
Scan rate 2 mV s 1
Amplitude 40 mV
curing, the exterior of the truncated needle is coated with nonconductive
epoxy and allowed to cure again. The protruding 5-mm carbon-fiber bundle
is made more sensitive and selective for NO by covering it with polymeric
porphyrin and Nafion, before calibration with NO. To implant the
porphyrinic NO sensor, the tissue of interest is pierced with a standard
22-gauge angiocatheter needle (clad with its catheter containing 4x 100
| ventilation holes near the tip), which is then advanced to the
desired location. After intracavitary contact, the catheter tip is
withdrawn 2-4 mm. The position of the catheter is secured, and the
placement of the needle is removed and quickly replaced with the
truncated 22-gauge porphyrinic NO sensor.
3. Cell Culture Sensors
A tissue culture can be grown directly on a porphyrinic sensor and
measurements of NO can be made by using voltammetric or amperometric
methods/'681 This macrosize sensor is advantageous for screening large
numbers of cells for NO release without using more tedious microelectrode
techniques. Sensor production consists of deposition of conductive
polymeric film on the surface of the conductive solid support-,
recticulated vitrous carbon (RVC).
The recticulated vitrous carbon is cut into 2mm x 1 mm x 0.5 mm. A
copper connective wire (0.3 mm) with thermoplastic insulation is attached
to the RVC by silver epoxy. The silver epoxy is allowed to dry overnight
in a vacuum oven (70 C.) and is then insulated by nonconductive epoxy.
The polymeric film is deposited from a degased solution of monomeric
porphyrin using the same procedure as described for the preparation of a
single-fiber sensor. After film formation, the electrode is dried in a
vacuum oven at 40 and then dip-coated in 1% Nafion in alcohol. The
biological cells suspended in 3 ml culture medium are placed dropwise
onto the sensor (sterilized by UV light) located in a 60 x 15 mm tissue
culture dish. The concentrated cell suspension on the sensor is incubated
for approxi-
Figure 12. Photograph of endothelial cells (porcine aorta) grown directly
on a porphyrinic sensor (deposited on recticulated vitrous carbon (RVC)).
mately 5 h to allow the cells to settle and adhere to it solid support,
at which time, additional fresh media is added. The cells should be
incubated until confluent (Figure 12).
4. Calibration
A standard calibration curve is prepared by subsequent addition of small
volumes of standard aqueous saturated NO solution (concentration 1.74 mM)
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