Concentration and separation of biological organisms by ultrafiltration and dielectrophoresis
Disclosed is a method for monitoring sources of public water supply for a variety of pathogens by using a combination of ultrafiltration techniques together dielectrophoretic separation techniques. Because water-borne pathogens, whether present due to “natural” contamination or intentional introduction, would likely be present in drinking water at low concentrations when samples are collected for monitoring or outbreak investigations, an approach is needed to quickly and efficiently concentrate and separate particles such as viruses, bacteria, and parasites in large volumes of water (e.g., 100 L or more) while simultaneously reducing the sample volume to levels sufficient for detecting low concentrations of microbes (e.g., <10 mL). The technique is also designed to screen the separated microbes based on specific conductivity and size.
1. An apparatus for concentrating and separating particles in water, comprising:
an ultrafiltration (“UF”) module comprising a feed port, at least one filtrate port, a retentate port, and a filtering media comprising a molecular weight cut-off (“MWCO”) smaller than an average mean diameter of a particle of interest, wherein a volume of water comprising particles having an average mean diameter greater than said MWCO are retained and concentrated in said UF module;
an insulator-based dielectrophoresis (“iDEP”) module comprising:
a plurality of fluid flow channels disposed on a substrate, wherein each of said fluid flow channels comprises a fluid inlet and a fluid outlet and a plurality of insulating flow structures disposed on said substrate, wherein each of said fluid inlets is separately connected to a first inlet manifold means, and wherein each of said fluid outlets is separately connected to a first outlet manifold means;
electrodes in electrical communication with the fluid inlet and outlet of each of the plurality of fluid flow channels, wherein the electrodes are positioned to generate a spatially non-uniform electric field across the plurality of insulating flow structures of each fluid flow channel, and wherein the spatially non-uniform electric field exerts a dielectrophoretic force on particles suspended in a quantity of water passing through each of the fluid flow channels; and
power supply means connected to each of the electrodes to generate an electric field within said fluid flow channel; and
conduit means disposed between the UF retentate port and the iDEP first inlet manifold means, wherein the UF module is placed in fluid communication with the iDEP module.
2. The apparatus of claim 1 , wherein the filter media MWCO is between about 10 kDaltons and about 300 kDaltons.
3. The apparatus of claim 1 , further comprising second and third iDEP modules, second inlet and outlet manifold means disposed between the first and second iDEP modules, and third inlet and outlet manifold means disposed between the second and third iDEP modules, wherein the first, second and third iDEP modules are connected in series and placed in fluid communication.
4. The device of claim 3 , wherein the wherein the electric field maintained on electrodes comprising the third iDEP module is greater than the electric field maintained on electrodes comprising the second iDEP module, and wherein the electric field maintained on electrodes comprising the second iDEP module is greater than the electric field maintained on electrodes comprising the first iDEP module.
5. The device of claim 1 , wherein said plurality of insulating flow structures are disposed in an ordered array.
6. The device of claim 1 , wherein said plurality of insulating flow structures are disposed randomly.
7. The device of claims 5 or 6 , wherein said plurality of insulating flow structures comprise one or more shapes.
8. The device of claim 7 , wherein said one or more shapes are the same or different.
9. The device of claims 5 or 6 , wherein said plurality of insulating flow structures comprise a plurality of post-like structures.
10. The device of claims 5 or 6 , wherein said plurality of insulating flow structures comprise a plurality of depressions.
11. The device of claim 1 , wherein the electric field comprises constant or variable components or both.