Continuous biomolecule separation in a nanofilter

Abstract

This invention provides a method and an apparatus for quickly continuously fractionating biomolecules, such as DNAs, proteins and carbohydrates by taking advantage of differential bidirectional transport of biomolecules with varying physico-chemical characteristics, for example size, charge, hydrophobicity, or combinations thereof, through periodic arrays of microfabricated nanofilters. The passage of biomolecules through the nanofilter is a function of both steric and electrostatic interactions between charged macromolecules and charged nanofilter walls, Continuous-flow separation through the devices of this invention are applicable for molecules varying in terms of any molecular properties (e.g., size, charge density or hydrophobicity) that can lead to differential transport across the nanofilters.

1 . A biomolecular sorter comprising: 
 a) a substrate;    b) a plurality of obstacles arranged at regular intervals in a plurality of rows, columns or combinations thereof on a surface of said substrate;    c) a sample inlet to said sorter;    d) at least a first conduit for applying an electrostatic force field or hydrodynamic force field parallel in direction to said rows; and    e) at least a second conduit for applying an electrostatic force field or hydrodynamic force field parallel in direction to said columns, and perpendicular in direction to said rows;    wherein said obstacles are so arranged as to form gaps between said obstacles, with horizontal gaps being of a width less than vertical gaps between said obstacles.    
     
     
         2 . The sorter of  claim 1 , wherein said horizontal gaps are from about 10-5000 nm.  
     
     
         3 . The sorter of  claim 1 , wherein said vertical gaps are from about 0.1-10 μm.  
     
     
         4 . The sorter of  claim 1 , wherein said obstacles in said rows are laterally shifted with respect to each row.  
     
     
         5 . The sorter of  claim 1 , wherein said gaps form channels for fluid conductance, when fluid is introduced in said sorter.  
     
     
         6 . The sorter of  claim 5 , comprising microfluidic channels in fluid communication with said channels.  
     
     
         7 . The sorter of  claim 6 , wherein said channels comprise sample loading ports.  
     
     
         8 . The sorter of  claim 6 , wherein said channels comprise sample collection ports.  
     
     
         9 . The sorter of  claim 6 , wherein said microfluidic channels are in fluid communication with a reservoir.  
     
     
         10 . The sorter of  claim 9 , wherein voltage is applied to said reservoir.  
     
     
         11 . The sorter of  claim 10 , wherein said applied voltage is less than 1000 V.  
     
     
         12 . The sorter of  claim 9 , wherein pressure is applied to said reservoir.  
     
     
         13 . The sorter of  claim 1 , wherein said electrostatic force field or hydrodynamic force field is applied in pulse-field operation mode.  
     
     
         14 . The sorter of  claim 1 , wherein said electrostatic force field or hydrodynamic force field is applied in continuous-field operation mode.  
     
     
         15 . The sorter of  claim 1 , wherein said substrate comprises silicon.  
     
     
         16 . A microchip comprising the sorter of  claim 1 .  
     
     
         17 . A method of sorting a fluid mixture comprising a plurality of biopolymers, which vary in terms of the physico-chemical characteristics of each of said plurality of biopolymers, said method comprising the steps of: 
 a) loading a fluid mixture comprising a plurality of biopolymers in a biomolecular sorter comprising: 
 i. a substrate;  
 ii. a plurality of obstacles arranged at regular intervals in a plurality of rows, columns or combinations thereof on a surface of said substrate, wherein said obstacles are so arranged as to form gaps between said obstacles, with horizontal gaps being of a width less than vertical gaps between said obstacles, and said gaps form channels for fluid conductance, when fluid is introduced in said sorter;  
 iii. a sample inlet to said sorter;  
 iv. microfluidic channels in fluid communication with said channels;  
 v. sample collection ports in fluid communication with said channels;  
 vi. at least a first conduit for applying an electrostatic force field or hydrodynamic force field parallel in direction to said rows;  
 vii. at least a second conduit for applying an electrostatic force field or hydrodynamic force field parallel in direction to said columns, and perpendicular in direction to said rows; and  
   b) applying said electrostatic force field or hydrodynamic force field parallel in direction to said rows, and said electrostatic force field or hydrodynamic force field parallel in direction to said columns, and perpendicular in direction to said rows, whereby applying said force fields allows for separation of said plurality of biopolymers through said channels; and    c) collecting separated biopolymers obtained in (b) from said sample collection ports.    
     
     
         18 . The method of  claim 17 , wherein said electrostatic force field parallel in direction to said rows provides an electroosmotic driving force for said fluid.  
     
     
         19 . The method of  claim 17 , wherein said fluid has an ionic strength of about 1-1000 mM.  
     
     
         20 . The method of  claim 19 , wherein said sorting is size-based.  
     
     
         21 . The method of  claim 17 , wherein said physico-chemical characteristics comprise size, charge, hydrophobicity, hydrophilicity, or a combination thereof.  
     
     
         22 . The method of  claim 17 , wherein said fluid has an ionic strength of about 1-1000 mM.  
     
     
         23 . The method of  claim 22 , wherein said sorting is charge-based.  
     
     
         24 . The method of  claim 17 , wherein greater resolution of said biopolymers is achieved when said applied voltage is greater than 40 V.  
     
     
         25 . The method of  claim 17 , wherein said horizontal gaps are from about 10-5000 nm.  
     
     
         26 . The method of  claim 17 , wherein said vertical gaps are from about 0.1-10 μm.  
     
     
         27 . The method of  claim 17 , wherein said obstacles in said rows are laterally shifted with respect to each row.  
     
     
         28 . The method of  claim 17 , wherein said sample inlet is a microchannel, in fluid communication with said channels.  
     
     
         29 . The method of  claim 17 , wherein said microfluidic channels are in fluid communication with a reservoir.  
     
     
         30 . The method of  claim 29 , wherein voltage is applied to said reservoir.  
     
     
         31 . The method of  claim 29 , wherein said applied voltage is less than 1000 V.  
     
     
         32 . The method of  claim 31 , wherein pressure is applied to said reservoir.  
     
     
         33 . The method of  claim 17 , wherein said electrostatic force field or hydrodynamic force field is applied in pulse-field operation mode.  
     
     
         34 . The method of  claim 17 , wherein said electrostatic force field or hydrodynamic force field is applied in continuous-field operation mode.  
     
     
         35 . The method of  claim 17 , wherein said fluid mixture comprises a cell lysate or tissue homogenate.  
     
     
         36 . The method of  claim 17 , wherein said fluid mixture comprises a large sample of deoxyribonucleic acids (DNA), proteins, or a combination thereof.  
     
     
         37 . The method of  claim 17 , wherein said fluid mixture comprises a buffered solution.  
     
     
         38 . The method of  claim 37 , further comprising the step of sorting a sample of said mixture two or more times, wherein the pH or ionic strength of said buffered solution is varied at the time of said sorting.