Negative dielectrophoresis for selective elution of immuno-bound particles
The procedure of dielectric electrophoresis (dielectrophoresis or DEP) utilizes field-polarized particles that move under the application of positive (attractive) and/or negative (repulsive) applied forces. This invention uses negative dielectric electrophoresis (negative dielectrophoresis or nDEP) within a microchannel separation apparatus to make particles move (detached) or remain stationary (attached). In an embodiment of the present invention, the nDEP force generated was strong enough to detach Ag-Ab (antigen-antibody) bonds, which are in the order of 400 pN (piconewtons) while maintaining the integrity of the system components.
1. A microfluidic separation method, comprising:
(a) providing a housing, said housing forming a microchannel having an interior surface;
(b) functionalizing said interior surface with a particle-attaching chemical species;
(c) contacting a particle with said functionalized interior surface, thereby initiating attachment of said particle to said functionalized interior surface, wherein the particle forms a molecular bond with the particle-attaching chemical species;
(d) positioning at least two controllable electrodes in the microchannel which when energized facilitate release of the particle by subjecting the particle to a non-uniform electric field; and
(e) generating the non-uniform electric field in said microchannel to break the molecular bond between the particle and the particle-attaching chemical species and release the particle from said functionalized interior surface,
wherein the at least two controllable electrodes are connected to a voltage source.
2. The microfluidic separation method according to claim 1 , wherein said particle-attaching chemical species is a biological macromolecule having an affinity for the particle.
3. The microfluidic separation method according to claim 1 , wherein said attaching to and releasing from said particle-attaching chemical species are influenced by a base concentration in the microchannel.
4. The microfluidic separation method according to claim 1 :
wherein said at least two controllable electrodes are coated with an oxide layer; and
wherein the voltage source generates a negative dielectrophoresis force strong enough to break the molecular bond of at least approximately 400 pN.
5. The microfluidic separation method according to claim 4 , wherein a desired region of said microchannel is subjected to said negative dielectrophoresis force, thereby facilitating release of particles selectively from said desired region of the microchannel.
6. A microfluidic separation and quantification method, the method comprising:
(a) providing a substrate, the substrate having a microchannel, the microchannel adjacent to a plurality of electrodes;
(b) connecting the plurality of electrodes to a voltage source to generate a negative dielectrophoresis field;
(c) functionalizing an interior surface of the microchannel with a first particle-attaching chemical species;
(d) introducing a first microfluid containing particles into the microchannel;
(e) moving the particles through the microchannel, wherein specific particles form a first chemical bond with the first particle-attaching chemical species;
(f) introducing a second microfluid containing beads into the microchannel, said beads functionalized with a second particle-attaching chemical species;
(g) moving the second microfluid through the microchannel, wherein the beads bind to the specific particles via a second chemical bond and are immobilized within the microchannel, and wherein the specific particles are situated in between the functionalized interior surface of the microchannel and the functionalized surface of the beads;
(h) generating the negative dielectrophoresis field from said plurality of electrodes;
(i) introducing a third microfluid into the microchannel;
(j) moving the third microfluid through the microchannel, wherein the third microfluid has a flow rate and the negative dielectrophoresis field has a force whereby the flow rate and the force in combination are sufficient enough to break the first chemical bond between either the first particle-attaching chemical species and the specific particles or the second chemical bond between the second particle-attaching chemical species and the specific particles, wherein the beads detach and become mobilized within the interior of the microchannel; and
(k) quantifying the beads that detach, wherein the number of beads that detach corresponds to a concentration of the specific particles within the first microfluid.
7. A microfluidic separation and quantification method, the method comprising:
(a) providing a substrate, the substrate having a microchannel, the microchannel adjacent to a plurality of electrodes;
(b) connecting the plurality of electrodes to a voltage source to generate a negative dielectrophoresis field;
(c) functionalizing an interior surface of the microchannel with a first particle-attaching chemical species;
(d) introducing a first microfluid containing particles into the microchannel;
(e) moving the particles through the microchannel, wherein specific particles form a first chemical bond with the first particle-attaching chemical species;
(f) introducing a second microfluid containing beads into the microchannel, said beads functionalized with a second particle-attaching chemical species;
(g) moving the second microfluid through the microchannel, wherein the beads bind to the specific particles via a second chemical bond and are immobilized within the microchannel, and wherein the specific particles are situated in between the functionalized interior surface of the microchannel and the functionalized surface of the beads;
(h) introducing a third microfluid into the microchannel, the third microfluid having a base concentration which weakens the first chemical bond between the specific particles and the first particle-attaching species on the interior surface of the microchannel and the second chemical bond between the specific particles and the second particle-attaching chemical species on the beads;
(i) generating the negative dielectrophoresis field from said plurality of electrodes;
(j) moving the third microfluid through the microchannel, wherein the negative dielectrophoresis field has a force applied to a weakened chemical bond that is sufficient to break said weakened chemical bond and detach the beads which become mobile within the interior of the microchannel; and
(k) quantifying the beads that detach, wherein the number of beads that detach corresponds to a concentration of the specific particles within the first microfluid.
8. A microfluidic separation and quantification method, the method comprising:
(a) providing a substrate, the substrate having a microchannel, the microchannel adjacent to a plurality of electrodes;
(b) depositing a layer of oxide in between the plurality of electrodes and the microchannel;
(c) connecting the plurality of electrodes to a voltage source to generate a negative dielectrophoresis field;
(d) functionalizing an interior surface of the microchannel with a first particle-attaching chemical species;
(e) introducing a first microfluid containing particles into the microchannel;
(f) moving the particles through the microchannel, wherein specific particles form a first chemical bond with the first particle-attaching chemical species;
(g) introducing a second microfluid containing beads into the microchannel, said beads functionalized with a second particle-attaching chemical species;
(h) moving the second microfluid through the microchannel, wherein the beads bind to the specific particles via a second chemical bond and are immobilized within the microchannel, and wherein the specific particles are situated in between the functionalized interior surface of the microchannel and the functionalized surface of the beads;
(i) generating the negative dielectrophoresis field from said plurality of electrodes, wherein the oxide layer allows application of a voltage sufficient enough for the negative dielectrophoresis field to break the first chemical bond between the specific particles and the first particle-attaching species on the interior surface of the microchannel and the second chemical bond between the specific particles and the second particle-attaching chemical species on the beads, and wherein the beads become detached and mobile within the interior of the microchannel;
(j) introducing a third microfluid into the microchannel;
(k) moving the third microfluid through the microchannel; and
(l) quantifying the beads that detach, wherein the number of beads that detach corresponds to a concentration of the specific particles within the first microfluid.