Fluidic device for quantifying the dynamic permeability and hydraulic conductivitiy of living tissue layers

Abstract

Systems and methods for measuring dynamic hydraulic conductivity and permeability associated with a cell layer are disclosed. Some systems include a microfluidic device, one or more working-fluid reservoirs, and one or more fluid-resistance element. The microfluidic device includes a first microchannel, a second microchannel, and a barrier therebetween. The barrier includes a cell layer adhered thereto. The working fluids are delivered to the microfluidic device. The fluid-resistance elements are coupled to one or more of the fluid paths and provide fluidic resistance to cause a pressure drop across the fluid-resistance elements. Mass transfer occurs between the first microchannel and the second microchannel, which is indicative of the hydraulic conductivity and/or dynamic permeability associated with the cells.

What is claimed is: 
     
         1 . A method for measuring hydraulic conductivity associated with cells, the method comprising:
 flowing a working fluid through a first microchannel at a first flow rate along a layer of cells, the layer of cells being disposed on a barrier, the first flow rate causing a first shear stress on the layer of cells;   applying a first pressure to the working fluid in the first microchannel to cause a portion of the working fluid to travel to a second microchannel through the layer of cells and the barrier; and   calculating a hydraulic conductivity of the layer of cells.   
     
     
         2 . The method of  claim 1 , wherein some of the portion of the working fluid, that travels through the layer of cells and the barrier, exits the second microchannel. 
     
     
         3 . The method of  claim 2 , further comprising collecting the working fluid exiting the second microchannel. 
     
     
         4 . The method of  claim 3 , wherein said calculating is based on said pressure and said collected working fluid exiting the second microchannel. 
     
     
         5 . The method of  claim 1 , further comprising performing an image-gathering technique on the layer of cells during the flowing and applying pressure steps. 
     
     
         6 . The method of  claim 2 , further comprising monitoring a marker associated with the fluid that travels through the layer of cells and the barrier and that exits the second microchannel. 
     
     
         7 . The method of  claim 6 , wherein said marker comprises the leading edge of the fluid that exist the second microchannel. 
     
     
         8 . The method of  claim 7 , wherein the leading edge is monitored in a fluid line coupled to said second microchannel. 
     
     
         9 . The method of  claim 1 , further comprising applying a fluidic resistance to the working fluid using a first fluid-resistance element. 
     
     
         10 . The method of  claim 9 , wherein the fluidic resistance is configured to cause the applied pressure to be generally constant pressure along the layer of cells. 
     
     
         11 . The method of  claim 1 , wherein said first microchannel is fluidically coupled to a working fluid reservoir containing working fluid. 
     
     
         12 . The method of  claim 11 , wherein said applying a pressure comprises raising the working fluid reservoir such that said working fluid flows by gravity. 
     
     
         13 . The method of  claim 1 , wherein pressure is applied while flowing said working fluid through said first microchannel. 
     
     
         14 . A method for measuring hydraulic conductivity associated with cells, the method comprising:
 moving a working fluid through a first microchannel of a microfluidic device, the microfluidic device including a second microchannel and a barrier located at an interface region between the first microchannel and the second microchannel, the barrier including a first side facing toward the first microchannel and having the cells adhered thereto;   measuring a portion of the working fluid that migrates through the cell layer and the barrier and exits the second microchannel; and   determining the hydraulic conductivity of the cells.   
     
     
         15 . The method of  claim 14 , wherein the pressure gradient across the barrier is zero. 
     
     
         16 . The method of  claim 14 , wherein said portion that migrates through the cell layer and the barrier moves by an active transport process. 
     
     
         17 . The method of  claim 14 , wherein said measuring comprises monitoring a marker associated with the working fluid that exits the second microchannel. 
     
     
         18 . The method of  claim 17 , wherein said marker comprises the leading edge of the portion of the working fluid that exits the second microchannel. 
     
     
         19 . The method of  claim 18 , wherein the leading edge is monitored in a fluid line coupled to said second microchannel. 
     
     
         20 . The method of  claim 14 , wherein said determining comprises determining the flow rate of the portion of the working fluid that migrates through the barrier. 
     
     
         21 . The method of  claim 14 , further including applying a fluidic resistance along a fluid path associated with the first microchannel. 
     
     
         22 . The method of  claim 21 , further including applying a pressure to the working fluid within the first microchannel to create a first pressure differential between the first microchannel and the second microchannel. 
     
     
         23 . The method of  claim 14 , wherein a fluid path associated with the first microchannel includes a fluidic resistor at a location downstream of the first microchannel to ensure a substantially constant pressure gradient along the cells on the barrier. 
     
     
         24 . A method for measuring hydraulic conductivity associated with cells, the method comprising:
 moving a working fluid through a first microchannel of a microfluidic device, the microfluidic device including a second microchannel and a barrier located at an interface region between the first microchannel and the second microchannel, the barrier including a first side facing toward the first microchannel and having the cells adhered thereto;   monitoring a marker associated with a portion of the working fluid that migrates through the cell layer and the barrier and exits the second microchannel; and   determining the hydraulic conductivity of the cells.   
     
     
         25 . The method of  claim 24 , wherein the marker is monitored in a fluid line coupled to said second microchannel.