On-Chip Biosensing utilizing the Motion of Magnetic Particles

Magnetic micro or nanoparticles (MAPs) coated with ligands (e.g. antibodies) of specific affinity to the bioanalyte (biomolecules, cells or viruses) to be detected are mixed with the fluid under investigation (e.g. blood). If bioanalyte is present, they will bind to the coated MAPs. The resulting fluid is then directed to a microfluidic channel. Once the bioanalyte is bound to a MAP, a compound is formed (LMAP) and the total volume of the MAP increases; the resulting volume is larger than the volume of a bare MAP. The MAPs are then accelerated, from the inlet towards the outlet, within the microfluidic channel by a defined, externally applied, magnetic field. The velocity of the MAPs or the time they require to travel a certain distance depends on (i) the magnetic force which is applied on the MAPs by the magnetic field, (ii) the drag force which results from the movement of the MAP in the liquid and (iii) the gravitational force if present. The magnetic force is the same for bare MAPs as well as for MAPs with attached bioanalyte, since both of them have the same magnetic moment. On the other side, the drag force depends on the square of the radius of the MAP and hence it is different for the bare MAP and the MAP with attached bioanalyte. Therefore, bare MAPs will reach a higher velocity or travel a certain distance faster than the MAPs with attached bioanalyte (LMAPs). The time they require to reach the outlet from the inlet is detected by magnetic field microsensors placed at the inlet and outlet of the microfluidic channel. Once this time difference is measured the velocity of the MAPs can be calculated. In conclusion, this volumetric increase of the MAP when the bioanalyte is bound onto its surface, changes consequently the velocity of the MAP under application of the same external magnetic force. The resulting LMAPs consume more time to complete the same distance compared to bare MAPs (smaller). This change in velocity between bare MAPs and LMAPs which are loaded with bioanalyte is then calculated. Thus, once a change in the velocity of the accelerated MAPs occurs it will be the demonstration of bioanalyte presence in the liquid which is under examination.

Magnetic micro or nanoparticles (MPs) coated with ligands (e.g. antibodies) of specific affinity to the bioanalyte (biomolecules, cells or viruses) to be detected are mixed with the fluid under investigation (e.g. water). If bioanalyte is present, they will bind to the coated MPs. The resulting fluid is then directed to a microfluidic channel. Once the bioanalyte is bound to a MP, a compound is formed (LMP) and the total volume of the MP increases; the resulting volume is larger than the volume of a bare MP. The MPs are then accelerated, from the inlet towards the outlet, within the microfluidic channel by a defined, externally applied, magnetic field. The velocity of the MPs or the time they require to travel a certain distance depends on (i) the magnetic force which is applied on the MPs by the magnetic field, (ii) the drag force which results from the movement of the MP in the liquid and (iii) the gravitational force if present. The magnetic force is the same for bare MPs as well as for MPs with attached bioanalyte, since both of them have the same magnetic moment. On the other side, the drag force depends on the square of the radius of the MP and hence it is different for the bare MP and the MP with attached bioanalyte. Therefore, bare MPs will reach a higher velocity or travel a certain distance faster than the MPs with attached bioanalyte (LMPs). The time they require to reach the outlet from the inlet is detected by magnetic field microsensors placed at the inlet and outlet of the microfluidic channel. Once this time difference is measured the velocity of the MPs can be calculated. In conclusion, this volumetric increase of the MP when the bioanalyte is bound onto its surface, changes consequently the velocity of the MP under application of the same external magnetic force. The resulting LMPs consume more time to complete the same distance compared to bare MPs (smaller). This change in velocity between bare MPs and LMPs which are loaded with bioanalyte is then calculated. Thus, once a change in the velocity of the accelerated MPs occurs it will be the demonstration of bioanalyte presence in the liquid which is under examination.