fig2 ( a ) illustrates a gel membrane probe constructed in accordance with the principles of a preferred embodiment of the present invention . the measuring probe includes : a plurality of measuring molecules having an affinity for the target molecules whose concentration is to be measured ; a solution that permits the measuring molecules to change their orientation when attracted or repelled by the target molecules ; means for measuring the orientation of the measuring molecules . the type of molecules used as measuring molecules depends on the type of molecules to be measured . for example , if the target molecule is an antibody , then the measuring molecule may be an antigen . alternatively , to measure concentration of an enzyme , a corresponding “ reaction substrate ” or “ reaction product ” may be used . the preferred embodiments of the invention are in principle applicable to any two types of molecules that attract or repel each other on a molecular level by a force sufficient to cause effects at the distance , or across the barrier , separating the measuring and target molecules during a measurement . an example of an enzyme - substrate pair to which the principles of the invention may be applied is a glucose enzyme - glucose pair such as glucose oxidase - glucose , glucose dehydrogenase - glucose , or glucose mutarotase - glucose . glucose is usually monitored in diabetics and sometimes referred to as blood sugar . an example of a suitable antibody antigen pair is crp specific monoclonal antibody — crp , the detection of which in blood is used to determine the presence and severity of infections present in the body . alternatively , the target molecule could be an antigen and the measuring molecule could be an antibody . other examples of target molecules to which the device of the invention may be applied include immunogobulins such as igg , igm , and iga , and lipoproteins . in addition , the device may be used for non - invasive detection of allergic reactions , difficult to detect diseases or infections caused by microorganisms such as viruses or bacteria , and any other type of infection or immune system reaction to a chemical or biological entity . the solution in which the measuring molecules are suspended or otherwise situated will depend on the type of measuring molecule . for example , in the illustrated example , the solution is a gel . alternatively , it might be possible to use liquids , solids , or other materials to contain the measuring molecules while permitting changes in orientation in response to the presence of the target molecule . in addition , the solution in which the measuring molecules are contained may include cofactors as necessary to increase the attractive or repulsive forces . in the example illustrated in fig2 ( a ) and 2 ( b ), electrodes are positioned on either side of the solution to enable measurement of the resistivity of the solution to an applied electric current . the change in resistance δr of a given measuring molecule ( mm ) laden gel layer when brought into proximity with complimentary target molecules ( tm ) across a barrier , such as a patient &# 39 ; s skin , is a function ( f ) of the affinity ( a ) or attractive / repulsive force of the mm - tm pair , the concentration of target molecules ctm , and the inverse of the distance ( d ) between the complimentary molecules . this may be expressed mathematically as follows : δ ⁢ ⁢ r ∝ f ⁡ ( actm d ) where δr ═ rb — rm , rb is the resistivity of the gel layer before being brought into proximity of the target molecules , rm is the resistivity of the gel layer after being brought into proximity with the gel layer , ( f ) is any function , whether linear or non - linear , that describes the relation between δr and actm / d , and both the function ( f ) and affinity variable ( a ) depend on the nature of the affinity pair . in addition to resistivity or conductivity , there are several ways in which the molecular orientation may be measured using this set up , including changes in the nuclear magnetic resonance ( nmr ) of the molecules , or measurement of changes in other properties of the solution , including electrical , magnetic , or optical properties , that are affected or caused to be affected by molecular orientation . those skilled in the art will understand that measuring molecules may be modified , for example , by providing chemically labeled cofactors , etc ., to enhance the affinity forces on the target molecules . furthermore , those skilled in the art will appreciate that spatial orientation may not be the only molecular property affected by the presence of the target molecules . for example , affinity forces may affect the phenomenon of electrophoresis , in which the molecules migrate across the gel in response to an applied field . those skilled in the art will appreciate that changes in such migration may be used instead of , or in addition to , orientation as a way of detecting the presence of affinity forces between the measuring and target molecules . practical implementation of the probe illustrated in fig2 ( a ) and 2 ( b ) requires a probe that can induce uniform molecular rotation in a sample of measuring molecules , to provide a baseline against which target molecule induced changes can be detected . for many applications , at least a 98 % rotation will be required . this unidirectional rotation of measuring molecules may be verified by conventional fluorescence optical spectroscopy techniques . in a preferred embodiment of the invention , in order to achieve the required unidirectional rotation , a uniform unidirectional current may be applied to a measuring molecule solution that has been uniformly applied on the measuring film , or that is homogeneously situated in a gel - like media . the uniform current and verification of the current is provided by an electrophoretic device capable of unidirectional current induction and planar conductivity measurement in a 360 ° array , currently envisioned to be a perpendicular mode relative to the applied current . a roller - type temperature controlled gel coating device may be used to achieve uniform application of the measuring molecular solution , preferably to a uniform thickness of between a few angstroms ( to accommodate at least one layer of measuring molecules and allow for their unhindered molecular rotation ) to a few millimeters . the gel - like media may , by way of illustration and not limitation , be a non - polar gel media readily soluble in water capable of producing a homogenous solution of measuring molecules , and that is liquid between 40 - 60 ° c . and that forms a gel - like solid between 5 - 40 ° c . upon achieving uniform rotation of the measuring molecules , implementation of the invention requires monitoring of molecular orientation , preferably to a rotation accuracy of at least + 5 %, which may again be verified by fluorescence spectroscopy of fluorescent labeled measuring molecules . once it is possible to “ see ” the spatial configuration of the uniformly rotated molecules , commercially available measuring devices can be used to measure current variance , directional variance of the applied current , and voltage variance , given a uniformly positioned gel coated film . the conductance of the film at different angles relative to the applied electrophoretic current in the “ off ” mode , i . e ., in the absence of electrophoretic field potential , must then be determined . commercially available measuring devices are currently capable of measuring resistance along and perpendicular to the current direction in a three dimensional mode , at 10 °± 2 ° intervals in a planar 360 ° array . the key is to be able to measure a small enough change in resistance due to current impedance caused by molecular rotation in the path of the current applied . the gel media should be selected to have a large variation in directional conductivity between electrophoretic conduction and conduction perpendicular to the electrophoretic field , with minimal time required for complete rotation of the measuring molecules at a constant voltage and current . widely used gel media include polyacrylamide gel and agarose gels . for each candidate gel , specific electrophoretic parameters of the measuring molecules in each gel should be measured , for a particular apparatus , as a function of concentration , temperature , and solvent composition . in order for the sensor of the invention to detect rotation of the measuring molecules in response the presence of target molecules , as described above , it is helpful to determine the exact effect of measuring molecule rotation on the conductivity or resistivity of the gel solution . this may be accomplished by measuring conductivity using electrophoretic electrodes when the residual electrophoretic current and voltage is zero , and measuring in a perpendicular plane at ten degree increments to the applied electrophoretic current . the sensor thereby determines the relation between measurable changes in conductivity or resistivity as a function of ( a ) direction of measuring current relative to the electrophoretic current applied to the gel media , ( b ) concentration of measuring molecules dissolved in the gel , and ( c ) electrophoretic field application time necessary for complete uniform rotation of the measuring molecules . the rotation of the measuring molecules may be monitored and verified by a fluorescence optical rotation measuring device . once a correlation between applied current and measuring molecule rotation is established , the effect of target solution concentration and proximity of target molecules on the conductance or resistivity of the gel solution can be established by measuring the conductance or resistivity of the gel solution for different target solutions . if a measurable difference in rotation of the measuring molecules is detected , a relationship between target distance and measuring molecule rotation can be established for different molecular pairs . rotation of the measuring molecules in response to proximity of target molecules can again be verified by fluorescence optical spectroscopy . a probe prototype 1 that can be used to verify directional conductance or resistivity changes in response to rotation of measuring molecules , to establish the composition and thickness of the gel media , and to identify the choice and concentration of measuring molecules necessary for targeted sensitivity , is illustrated in fig3 . the probe prototype is a modified electrophoretic cell including a cylindrical body 2 having respective electrodes 3 and 4 at the top and bottom for creating an electrophoretic field across a gel coated membrane 5 wrapped around the cylinder . the electrophoretic field causes the measuring molecules in the gel to orient relative to the field , at which time current to the electrodes is switched off or the effect of the electrodes is neutralized or removed , and the resistance for the gel coated film is measured perpendicular to and across the 360 ° array . as indicated above , once a suitable gel is found and a correlation between rotation of the measuring molecules and the resistance of the gel coated film is established , then measurements can also be made in the presence of target molecules , for example , by bringing the coated membrane into contact with a beaker of solution of the target molecules . for the next phase of verification , the probe should be sensitive enough to produce a measurable change in resistivity when ± 5 % of the measurement molecules rotate , precise enough to achieve a ± 10 % coefficient of variation for a standard solution of target molecules at an upper limit of a clinical normal range of the target , and sufficiently accurate to reproduce standard curves of pure target solution with equimolar mixtures of nonspecific homologues to within ± 15 % coefficient of variation . ultimately , a practical version of the probe with require a sensitivity of at least ± 2 %, precision of ± 5 %, and accuracy , using actual patient serum / blood sample with the following minimum correlation parameter values versus a standard reference method , of 0 . 9 ± 0 . 1 regression coefficient , 0 . 9 ± 0 . 15 slope , and y intercept of ± 10 % of the lower limit of a clinical normal range . having thus described a preferred embodiment of the invention in sufficient detail to enable those skilled in the art to make and use the invention , it will nevertheless be appreciated that numerous variations and modifications of the illustrated embodiment may be made without departing from the spirit of the invention , and it is intended that the invention not be limited by the above description or accompanying drawings , but that it be defined solely in accordance with the appended claims .
an apparatus and method for detecting the presence and measuring the concentrations of molecules through a barrier and / or at a distance utilizes the principle of chemical / electrostatic attraction , i . e ., the affinity between charged atoms and molecules that cause their chemical interactions and reactions , to infer , based on the behavior of molecules on one side of the barrier , the presence and concentration of corresponding molecules on the other side of the barrier . the invention is useful , by way of example and not limitation , in non - invasively measuring glucose levels of diabetic patients .