Electrostatic control of ionic environment in a droplet based platform for biological applications

Abstract

A process and device for electrostatically controlling an ionic environment in a droplet, such as in a droplet-based platform including polymerase-chain reaction (PCR) applications. The process includes providing a chip that comprises at least a pair of electrodes, placing a salt-containing droplet on the chip, and then applying a bias across the electrodes to accumulate ions near surfaces of the electrodes, thereby depleting a bulk salt concentration in regions of the droplet away from the electrodes.

1 . A process for electrostatically controlling an ionic environment in a droplet, the process comprising:
 providing a chip that comprises at least a pair of electrodes;   placing a salt-containing droplet on the chip so that the droplet contacts the pair of electrodes; and then   applying a bias across the pair of electrodes to accumulate ions near surfaces of the electrodes, thereby reducing the salt concentration in regions of the droplet away from the electrodes.   
     
     
         2 . The process according to  claim 1 , wherein the droplet contains DNA and the step of applying the bias causes denaturation of the DNA by modification of the melting temperature thereof. 
     
     
         3 . The process according to  claim 1 , wherein the droplet contains DNA, and reduction of the bulk salt concentration reduces the melting temperature of the DNA. 
     
     
         4 . The process according to  claim 1 , wherein the step of applying the bias serves to modulate a pH profile in the droplet for isoelectric protein separation. 
     
     
         5 . The process according to any one of  claim 1 , wherein the process is a PCR-based process. 
     
     
         6 . The process according to  claim 5 , wherein the droplet contains DNA and magnesium ions, and the step of applying the bias modulates the magnesium ion concentration in the droplet for PCR optimization. 
     
     
         7 . The process according to  claim 5 , wherein the process is used in DNA fingerprinting. 
     
     
         8 . The process according to  claim 5 , wherein the process is used in cloning. 
     
     
         9 . The process according to  claim 5 , wherein the process is used in, phylogenetics. 
     
     
         10 . The process according to  claim 5 , wherein the process is used in mutagenesis. 
     
     
         11 . The process according to  claim 5 , wherein the process is used in analysis of gene expression. 
     
     
         12 . The process according to  claim 1 , wherein the electrodes have a dentritic surface morphology. 
     
     
         13 . The process according to  claim 1 , wherein the electrodes are formed using Pt-black. 
     
     
         14 . A device for controlling an ionic environment in a droplet, comprising:
 a dielectric substrate;   a biological sensor mounted to the substrate; and   at least a pair of electrodes mounted to the substrate and electrically isolated from each other and from the sensor, the electrodes having a dentritic surface morphology;   wherein the biological sensor is disposed between the pair of electrodes.   
     
     
         15 . The device of  claim 15 , wherein the dentritic surface morphology is formed from Pt-black. 
     
     
         16 . The device of  claim 14 , further comprising a voltage source connected across the pair of electrodes, the voltage source configured to apply a voltage bias across the pair of electrodes to accumulate ions near surfaces of the electrodes when a droplet is placed on the sensor and the electrodes, thereby reducing the bulk salt concentration in regions of the droplet away from the electrodes. 
     
     
         17 . The device of  claim 16 , further comprising an electronic controller having a computer processor and a memory, the electronic controller operatively connected to the voltage source and the biological sensor, the electronic controller configured to control the applied voltage and monitor a signal output from the biological sensor. 
     
     
         18 . The device of  claim 14 , wherein the biological sensor is a DNA sensor. 
     
     
         19 . The device of  claim 18 , wherein the DNA sensor is coated with a receptor DNA material. 
     
     
         20 . A process for performing a polymerase-chain reaction, comprising:
 providing a chip that comprises at least a pair of electrodes;   placing a droplet comprising DNA, DNA primer, and polymerase on the chip so that the droplet contacts the pair of electrodes;   applying a bias across the pair of electrodes to accumulate ions near surfaces of the electrodes, thereby reducing the bulk salt concentration in regions of the droplet away from the electrodes and denaturing the DNA in the droplet;   controlling the temperature of the droplet to achieve annealing of the denatured DNA to the primer; and   controlling the temperature of the droplet to achieve extension of the DNA using the polymerase.