Determination of biological conditions using impedance measurements

Abstract

Apparatus and methods for the diagnostics of biological conditions using impedance measurements are provided wherein an electrical conducting probe can be placed against a skin surface of the subject, wherein the probe is made up of a plurality of electrodes in the form of spikes, the spikes being laterally spaced apart from each other and being of sufficient length to penetrate the stratum corneum, passing an electrical current through the electrodes to obtain a value of impedance for the skin, and converting the impedance to a concentration of a substance such as glucose in blood of a subject.

1 . A method for the non-invasive determination of the concentration of a substance (glucose) in blood of a subject, the method comprising the steps of: 
 (a) placing an electrical conducting probe against a skin surface of the subject, wherein the probe comprises a plurality of electrodes, each electrode comprising a spike, the spikes being laterally spaced apart from each other and being of sufficient length to penetrate the stratum corneum;    (b) passing an electrical current through the electrodes to obtain a value of impedance for the skin; and    (c) converting the impedance to said concentration.    
     
     
         2 . A method according to  claim 1 , wherein each spike is at least 10 μm in length.  
     
     
         3 . The method of  claim 1 , wherein the probe comprises three said electrodes, the spikes of first and second of the electrodes being laterally spaced a first distance from each other, the spikes of the first and third electrodes being laterally spaced a second distance from each other, and wherein and step (b) includes separately passing an electrical current between the first and second electrodes and the first and third electrodes to obtain first and second said values of skin impedance.  
     
     
         4 . The method of  claim 3 , wherein the first and second distances are different from each other.  
     
     
         5 . The method of  claim 3 , wherein the first distance is between about 0.1 mm and about 40 mm; or between about 0.1 mm and 30 mm; or between about 0.1 mm and 25 mm; or between about 0.1 mm and 20 mm; or between about 0.1 mm and 15 mm; or between about 0.2 mm and 10 mm; or between about 0.2 mm and 8 mm; or between about 0.2 mm and 5 mm; or between about 0.2 mm and 3 mm; or between about 0.2 mm and 2 mm; or between about 0.2 mm and 1.5 mm; or between about 0.2 mm and 1 mm; or between about 0.2 mm and 0.5 mm.  
     
     
         6 . The method of  claim 5 , wherein the second distance is between about 1 mm and about 50 mm; or between about 1 mm and 40 mm; or between about 1 mm and 30 mm; or between about 1 mm and 25 mm; or between about 1 mm and 20 mm; or between about 1 mm and 15 mm; or between about 1 mm and 10 mm; or between about 1 mm and 9 mm; or between about 1 mm and 8 mm; or between about 1 mm and 7 mm; or between about 2 mm and 8 mm; or between about 3 mm and 7 mm; or between about 4 mm and 7 mm; or between about 4 mm and 6 mm; or about 5 mm.  
     
     
         7 . The method of  claim 1 , wherein for each electrode, there are at least two said spikes, or at least three said spikes, or at least four said spikes, or at least five said spikes, or at least six said spikes, or at least seven said spikes, or at least eight said spikes, or at least nine said spikes, or at least ten said spikes, or at least twelve said spikes, or at least fifteen said spikes, or at eighteen said spikes, or at least twenty said spikes, or at least twenty-five said spikes, or at least thirty said spikes, or at least thirty-five said spikes, or at least fifty said spikes.  
     
     
         8 . The method of  claim 1  wherein each said spike is up to 250, or up to 240, or up to 230, or up to 220, or up to 210, or up to 200, or up to 190 or up to 180 or up to 170 or up to 160 or up to 150 or up to 140 or up to 130 or up to 120 or up to 110 or up to 100 μm in length.  
     
     
         9 . The method of  claim 1  wherein each said spike is at least 20, or at least 30 or at least 40 or at least 50, or at least 60 or is at least 70 or is at least 80 or is at least 90 μm in length.  
     
     
         10 . The method of  claim 1 , wherein each said spike is of sufficient length to penetrate below the skin surface to the Stratum Germinativum.  
     
     
         11 . The method of  claim 1 , wherein the outer diameter of each spike on the electrodes is between about 20 μm and about 50 μm.  
     
     
         12 . The method of  claim 1 , wherein said electrical current has a frequency of between about 10 Hz and about 10 MHz.  
     
     
         13 . The method of  claim 12 , wherein step (b) is conducted a first time at a first said frequency, and step (b) is conducted a second time at a second said frequency.