Optical detection of ferromagnetic and fluorescently labeled microparticles, simulation of a magnetic trap

A microsphere-based detoxification system (MDS) [1,2] is an adsorption system, whereby microadsorbent particles having diameters of 1–20 µm 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, causing critical side effects. A non invasive optical detection system was developed to monitor the extracorporeal venous bloodstream for the presence of released microparticles. For detection purposes, polymeric microspheres, both ferromagnetic and fluorescently labeled, are suspended with the adsorbent particles. In the case of a membrane rupture, the labeled particles would be released together with the microadsorbent [2]. A high effective magnetic trap collect the ferromagnetic marker beats in the focus of an optical fluorescence detection device where the signal output is proportional to the trapped amount of labeled particles. A simulation model based on fluidic, gravitational and magnetic forces was developed to analyze the motion and sedimentation of the marker particles in the magnetic trap. The simulation results show excellent accordance to the laboratory experiments.