Biosensor and method of analyte measuring

Abstract

A biosensor capable of analyzing an object, such as antigen, antibody, DNA or RNA, through detection of magnetic field to thereby allow washout of unbound label molecules to be unnecessary, which biosensor is compact and available at low price, excelling in detection precision. Coils are arranged at an upper part and a lower part of a magnetic sensor using a hall element as a magnetic field detection element. An object and magnetic particles having an antibody capable of specific bonding with the object bound to the surface thereof are introduced in the magnetic sensor having a molecular receptor capable of specific bonding with the object attached to the surface thereof. Therefore, a change in magnetic field by magnetic particles bonded through the molecular receptor to the surface of the magnetic sensor is detected by means of the hall element. At that time, one applied magnetic field is set so that the magnetization intensity of magnetic particles falls within the range from initial magnetic permeability to maximum magnetic permeability while another applied magnetic field is set so that the magnetization intensity of some or all of the magnetic particles becomes saturated, and output signals are compared with each other. Thus, the amount of bonded magnetic particles can be identified.

1 . A sensor comprising a magnetic sensor, which has a plurality of magnetic field detection elements arranged two dimensionally in X rows and Y columns (X and Y are natural numbers), said detection elements each generating an output value according to the intensity of a detected magnetic field, and measures an amount of magnetic particles on said magnetic sensor based on said output values, 
 wherein said sensor has a signal processing means by which said amount of magnetic particles is determined based on a dispersion of an output value distribution obtained from said output values of the plurality of magnetic field detection elements.    
   
   
       2 . A sensor according to  claim 1 , wherein 
 said magnetic particles bind to an object that is bound to said magnetic sensor, and    said signal processing means determines the amount of magnetic particles bound to said magnetic sensor through said object and further an amount of said object based on the amount of said magnetic particles.    
   
   
       3 . A biosensor according to  claim 2 , wherein 
 said signal processing means determines the amount of said bound magnetic particles based on the difference between the dispersion of said output value distribution and the dispersion of the reference distribution, the latter distribution being obtained from the output value of the plurality of magnetic field detection elements in the state where the magnetic particles are not bound to said magnetic sensor.    
   
   
       4 . A biosensor according to  claim 2 , 
 comprising a means for applying external magnetic fields of greatly different intensities to said magnetic sensor bound to said magnetic particles, wherein one of said external magnetic fields of greatly different intensities is such a strong magnetic field that the magnetization intensity of at least some of the bound magnetic particles becomes saturated, and another external magnetic field is such a weak magnetic field that said bound magnetic particles each have a magnetic permeability falling within a range from an initial magnetic permeability to a maximum magnetic permeability, and    wherein said signal processing means determines an amount of said bound magnetic particles based on the difference between the dispersion of said output value distribution when said strong magnetic field is applied and the dispersion of said output value distribution when said weak magnetic field is applied.    
   
   
       5 . A biosensor comprising a magnetic sensor, which has a plurality of magnetic field detection elements arranged two dimensionally in X rows and Y columns (X and Y are natural numbers), said detection elements each generating an output value according to the intensity of a detected magnetic field, and measures an amount of magnetic particles on said magnetic sensor based on said output values, 
 further comprising:    a means for applying external magnetic field of greatly different intensities to said magnetic sensor bound to said magnetic particles;    a signal processing means that determines the amount of said bound magnetic particles by comparing output values of respective said magnetic field detection elements when the external magnetic field of greatly different intensities is applied, and    wherein one of said external magnetic field of greatly different intensities is such a strong magnetic field that the magnetization intensity of at least some of said bound magnetic particles becomes saturated, and another external magnetic field is such a weak magnetic field that of said bound magnetic particles each have the magnetic permeability falling within a range from an initial magnetic permeability to a maximum magnetic permeability.    
   
   
       6 . A biosensor according to  claim 5 , wherein 
 said strong magnetic field changes in intensity within such a range that at least some of said bound magnetic particles becomes saturated, and said weak magnetic field changes in intensity within such a range that the permeability of said magnetic particles changes from the initial magnetic permeability to the maximum magnetic permeability, and    said signal processing means obtains changes in output values of said magnetic field detection elements according to changes in intensity of the external magnetic field, when external magnetic fields of greatly different intensities including said strong magnetic field and said weak magnetic field are applied,    and determines the amount of said bound magnetic particles based on differentials of the changes in these output values.    
   
   
       7 . A biosensor according to  claim 4 , wherein 
 the output values are obtained from said plurality of said magnetic field detection elements first by applying said weak magnetic field by said means for applying an external magnetic field, and then another set of output values is obtained from said plurality of said magnetic field detection elements by applying said strong magnetic field by said means for applying an external magnetic field.    
   
   
       8 . A biosensor according to  claim 4 , 
 wherein said means for applying an external magnetic field applies a magnetic field vertically to said magnetic sensor.    
   
   
       9 . A biosensor according to  4 , 
 wherein said means for applying an external magnetic field applies a DC magnetic field.    
   
   
       10 . A biosensor according to  claim 4 , 
 wherein said means for applying an external magnetic field applies an AC magnetic field.    
   
   
       11 . A biosensor according to  claim 4 , 
 wherein    said weak magnetic field is an AC magnetic field with such an intensity that the magnetic permeability of said each bound magnetic particle falls within a range from the initial magnetic permeability to the maximum magnetic permeability, and    said strong magnetic field is an external magnetic field of said AC magnetic field plus a DC magnetic field, with such an intensity that the magnetization intensity of at least some of said bound magnetic particles becomes saturated.    
   
   
       12 . A biosensor according to  claim 10 , 
 wherein said signal processing means further includes:    a noise prediction means that predicts noise components from frequency components other than those corresponding to said AC magnetic field, said noise components being included in output values of said magnetic field detection elements; and    a noise removal means that removes noise components from frequency components corresponding to said AC magnetic field included in output values from said magnetic field detection elements based on the noise components predicted by said noise prediction means.    
   
   
       13 . A biosensor according to  claim 4 , 
 wherein the magnetic particles bound to said magnetic sensor are associated with other magnetic particles in a direction of the magnetic flux formed by said external magnetic field.    
   
   
       14 . A biosensor according to  claim 2 , 
 wherein said magnetic field detection elements generate output values in proportion to a magnetic flux density of a magnetic flux formed in a detection space where a magnetic field may be detected.    
   
   
       15 . A biosensor according to  claim 2 , 
 wherein said magnetic field detection elements each comprise a hall element.    
   
   
       16 . A biosensor according to  claim 15 , comprising further a selection means for selecting an arbitrary element among said plurality of said magnetic field detection elements and obtaining an output value therefrom.  
   
   
       17 . A biosensor according to  claim 16 , comprising still further a signal amplification circuit that amplifies the output value of said magnetic field detection element selected by said selection means, 
 wherein said magnetic sensor, said selection means and the signal amplification circuit are formed on a chip.    
   
   
       18 . A biosensor according to  claim 15 , 
 wherein said hall element comprises: a pair of current terminals; a gate electrode that controls a current flowing between said pair of current terminals; and a pair of output terminals that are disposed so that a current flows in almost vertical direction against the current flowing between said pair of current terminals.    
   
   
       19 . A biosensor according to  claim 18  including: said gate electrode that is connected to a gate electrode interconnect which is common for said hall elements arranged in a same row; said pair of current terminals that are connected to a pair of current terminal interconnects which are common for said hall elements arranged in a same column; and said pair of output terminals that are connected to a pair of output terminals which are common for said hall elements arranged in a same column, and 
 wherein said selection means selects an arbitrary element from a plurality of hall elements and obtains output value thereof, by selecting one from Y numbers of gate electrode interconnects, a pair from X numbers of pairs of current terminal interconnects and a pair from X numbers of pairs of output terminal interconnects.    
   
   
       20 . A biosensor according to  claim 2 , 
 wherein, in each detection space where each magnetic field may be detected by said magnetic field detection elements, an area of a vertical cross section of a magnetic flux formed on a surface of said magnetic sensor is almost the same as a maximum cross section area of said magnetic particle.    
   
   
       21 . A biosensor according to  claim 2 , 
 wherein said each magnetic field detection element is arranged with a space so that each element detects different magnetic particles from each other.    
   
   
       22 . A biosensor according to  claim 2 , 
 wherein a surface of said magnetic sensor is treated so that molecular receptors capable of binding to said magnetic particles may be immobilized thereto.    
   
   
       23 . A biosensor according to  claim 22 , 
 wherein the surface of said magnetic sensor is treated so that the molecular receptors capable of binding to said magnetic particles may be immobilized selectively to a specific area.    
   
   
       24 . A biosensor according to  claim 2 , in which recesses corresponding to the magnetic particles in size are formed on the surface of said magnetic sensor in a detection space capable of magnetic field detection, 
 wherein the molecular receptors capable of binding to magnetic particles are present only in these recesses.    
   
   
       25 . A biosensor according to  claim 2 , 
 wherein a first magnetic field generating means, which generates a magnetic field that keeps away the magnetic particles from the surface of said magnetic sensor so that the magnetic particles are not bound to the surface thereof, is provided facing said surface.    
   
   
       26 . A biosensor according to  claim 2 , 
 wherein a second magnetic field generating means, which generates a magnetic field that keeps said magnetic particles closer to the surface of said magnetic sensor, is further provided.    
   
   
       27 . A biosensor according to  claim 25 , 
 further comprising: a second magnetic field generating means, which generates a magnetic field that keeps said magnetic particles closer to the surface of said magnetic sensor; and a magnetic field device control means that operates said first magnetic field generating means and said second magnetic field generating means alternately, to generate a magnetic field so that magnetic particles not bound to the surface of said magnetic sensor are stirred.    
   
   
       28 . A biosensor comprising a magnetic sensor, in which a plurality of magnetic field detection elements are arranged, said elements each producing an output value corresponding to the intensity of the detected magnetic field; and a signal processing means that determines an amount of magnetic each particles bound to said magnetic sensor based on respective output values obtained from said plurality of magnetic field detection elements, 
 wherein said signal processing means judges the dispersion condition of said magnetic particles based on the output values obtained from said plurality of magnetic field detection elements, after introducing said magnetic particles to said magnetic sensor and before removing said unbound magnetic particles from said magnetic sensor.    
   
   
       29 . A method of assaying an object using a biosensor according to  claim 2 , in which said magnetic particles bind specifically to an object that binds to said magnetic sensor, 
 wherein said method comprises the steps of: determining an amount of said magnetic particles bound to said magnetic sensor through said object using said biosensor; and determining an amount of said object based on the amount of said magnetic particles.    
   
   
       30 . A method according to  claim 29 , 
 wherein coupling of said magnetic sensor and said object and coupling of said object and said magnetic particles, are carried out at the same time in a reaction vessel containing said magnetic sensor.    
   
   
       31 . A method of assaying an object using a biosensor according to  claim 2 , in which said magnetic particles can replace an object bound to said magnetic sensor reversibly, 
 wherein said method comprises the steps of: determining an amount of said magnetic particles which have bound to said magnetic sensor by replacement of said object using said biosensor; and determining an amount of said object based on the amount of said magnetic particles.