Detection of fluorescently labeled microparticles in blood.
BACKGROUND
A microsphere-based detoxification system is an adsorption system, whereby microadsorbent particles having diameters of 1-20 microm circulate in an extracorporeal filtrate circle. A thin-wall hollow-fiber membrane filter separates the microparticle-plasma suspension from the bloodstream. For patient safety, it is necessary to have a means to detect membrane ruptures that could lead to a release of microparticles into the patient's bloodstream.


METHODS
An optical detection system was developed to monitor the venous bloodstream for the presence of microparticles from the filtrate circuit. For detection purposes, cellulose microspheres, both ferromagnetic and fluorescence labeled, were included with the microsphere adsorbant particles. In the case of a membrane rupture, the labeled particles would also be released into the bloodstream. By illuminating a small volume of blood with an excitation wavelength (590 nm) of the fluorescence marker, the particles can be detected by their emission light at 620 nm. The detector sensitivity is increased by collecting the ferromagnetic and fluorescently labeled microparticles using a magnetic trap. The efficiency of magnetic trap arrangements was tested by adjusting the magnet placements.


RESULTS
In vitro experiments were performed by pumping whole blood and labeled microparticles through the fluorescence detector. The efficiency of a magnetic trap arrangement was determined. With an optimal trap setup, 5-10 microl of labeled microparticles can be clearly detected in streaming whole blood.


CONCLUSIONS
An easy to handle microparticle detector was developed, ready for use in particle based blood detoxification systems. The microparticle detection system fulfills the medical and technical requirements to bring the MDS into clinical tests.
Brandl
M
M
Center for Biomedical Technology, Danube University Krems, AT-3500 Krems, Austria. martin.brandl@donau-uni.ac.at
Hartmann
J
J
Posnicek
T
T
Ausenegg
F R
FR
Leitner
A
A
Falkenhagen
D
D
D001774:Blood Chemical Analysis; D005112:Extracorporeal Circulation; D005453:Fluorescence; D005470:Fluorometry / Q000295:instrumentation / Q000379:methods; D006801:Humans; D008567:Membranes, Artificial; D008863:Microspheres; D012680:Sensitivity and Specificity; D016060:Sorption Detoxification / Q000379:methods
D008567:Membranes, Artificial