Biosensor method and system

Abstract

A method of detecting a target biological entity comprising: introducing a biofluid to a suspension to provide a precursor mixture, the biofluid comprising a plurality of target biological entities, and the suspension comprising a plurality of nanoparticles, wherein each of the plurality of nanoparticles is functionalized so that it may bind with the target biological entity to produce a bound nanoparticle-entity assembly; treating the precursor mixture to separate/isolate the bound nanoparticle-entity assemblies to provide a treated precursor mixture; and characterizing the treated precursor mixture with a sensor comprising a substrate bearing electrodes separated by a lateral distance of less than 100 nm, wherein a region between the electrodes defines a sensing region. The characterizing comprises: applying an electric field to the treated precursor mixture to concentrate the assemblies in the sensing region; applying a nanoparticle sensing voltage between the electrodes; characterizing a response of the sensing region to the nanoparticle sensing voltage to determine treated precursor mixture characterizing data.

1 - 36 . (canceled) 
     
     
         37 . A method of detecting a target biological entity in a biofluid, the method comprising:
 introducing the biofluid to a suspension to provide a precursor mixture, wherein the biofluid comprises a plurality of target biological entities, and the suspension comprises a plurality of nanoparticles, wherein each of the plurality of nanoparticles is functionalized so that it is able to bind with the target biological entity to produce a bound nanoparticle-entity assembly;   treating the precursor mixture to separate the bound nanoparticle-entity assemblies from nanoparticles not comprised in one of the bound nanoparticle-entity assemblies to provide a treated precursor mixture; and   characterizing the treated precursor mixture with a sensor, the sensor comprising a substrate bearing a pair of electrodes separated by a lateral distance of less than 100 nm, wherein a region between the electrodes defines a sensing region, and wherein the characterizing comprises:   applying an electric field to the treated precursor mixture to concentrate the bound nanoparticle-entity assemblies in the sensing region;   applying a nanoparticle sensing voltage between the electrodes;   characterizing a response of the sensing region to the nanoparticle sensing voltage to determine treated precursor mixture characterizing data; and   detecting the presence of the target biological entity from the treated precursor mixture characterizing data.   
     
     
         38 . The method as claimed in  claim 37 , wherein applying the electric field to the treated precursor mixture comprises applying an AC voltage to a pair of treatment electrodes. 
     
     
         39 . The method as claimed in  claim 38 , wherein the pair of treatment electrodes is the pair of electrodes on the substrate separated by a lateral distance of less than 100 nm. 
     
     
         40 . The method as claimed in  claim 37  wherein characterizing a response of the sensing region to the nanoparticle sensing voltage to determine treated precursor mixture characterizing data comprises identifying whether, after concentrating the bound nanoparticle-entity assemblies in the sensing region, the sensing region exhibits ohmic behaviour. 
     
     
         41 . The method as claimed in  claim 37 , wherein substrate bears a group of at least 10 or 100 pairs of electrodes each with electrodes separated by a lateral distance of less than 100 nm, to define a group of the sensing regions, wherein applying the electric field to the treated precursor mixture concentrates the bound nanoparticle-entity assemblies in the group of sensing regions, and wherein the characterizing comprises characterizing the response of each sensing region of the group of sensing regions and combining the responses to determine the treated precursor mixture characterizing data. 
     
     
         42 . The method as claimed in  claim 37 , wherein a conductivity of the plurality of nanoparticles is higher relative to a conductivity of the precursor mixture. 
     
     
         43 . The method as claimed in  claim 37 , wherein applying the electric field induces an attractive force acting between the sensing region of the electrodes and the nanoparticle. 
     
     
         44 . The method as claimed in  claim 37 , wherein the nanoparticle sensing voltage is a constant voltage which induces a direct current between the electrodes. 
     
     
         45 . The method as claimed in  claim 37 , wherein each of the plurality of nanoparticles is functionalized with a binding element which provides a capability to bind with the target biological entity to produce the bound nanoparticle-entity assembly. 
     
     
         46 . The method as claimed in  claim 37  wherein the binding element comprises an aptamer or antibody, and wherein each nanoparticle has, on average, less than five aptamers or antibodies attached or just a single aptamer or antibody attached. 
     
     
         47 . The method as claimed in  claim 37 , wherein a surface of each of the electrodes adjacent to the sensing region is functionalized by providing the surface with linker molecules which enhance the binding the bound nanoparticle-entity assembly between the electrodes. 
     
     
         48 . The method as claimed in  claim 47 , wherein the linker molecules comprise a thiol linker. 
     
     
         49 . The method as claimed in  claim 37 , wherein an average maximum dimension of the nanoparticles is greater than about 20 nm and/or less than about 100 nm. 
     
     
         50 . The method as claimed in  claim 37 , wherein the plurality of nanoparticles comprises gold nanoparticles. 
     
     
         51 . The method as claimed in  claim 37 , wherein the treating the precursor mixture comprises selective separation of the bound nanoparticle-entity assemblies from the nanoparticles not comprised in one of the bound nanoparticle-entity assemblies according to a property of any of: density, size, permittivity and conductivity. 
     
     
         52 . The method as claimed in  claim 51 , wherein treating according to density in the precursor mixture comprises centrifugation of the precursor mixture. 
     
     
         53 . The method as claimed in  claim 51 , wherein treating according to size in the precursor mixture comprises passing the precursor mixture through a microfluidic array comprising a mechanical filter. 
     
     
         54 . The method as claimed in  claim 51 , wherein treating according to conductivity in the precursor mixture comprises applying an alternating electric field to the precursor mixture. 
     
     
         55 . The method as claimed in  claim 37 , wherein the target biological entity is an extracellular vesicle or exosome. 
     
     
         56 . A microfluidic system for detecting a target biological entity in a biofluid, the system comprising:
 a first microfluidic input to receive a biofluid, wherein the biofluid comprises a plurality of target biological entities;   a second microfluidic input to receive a suspension of nanoparticles, wherein each of the plurality of nanoparticles is functionalized so that it is able to bind with the target biological entity to produce a bound nanoparticle-entity assembly;   a mixing chamber or channel to mix the biofluid with the suspension of nanoparticles to form a precursor mixture;   a precursor mixture treatment chamber or channel configured to treat the precursor mixture to separate the bound nanoparticle-entity assemblies from nanoparticles not comprised in one of the bound nanoparticle-entity assemblies to provide a treated precursor mixture;   a precursor characterization chamber or channel to characterize the treated precursor mixture, the precursor characterization chamber or channel comprising a sensor with a substrate bearing a pair of electrodes separated by a lateral distance of less than 100 nm, wherein a region between the electrodes defines a sensing region; and   a treated precursor mixture characterization system configured to:
 apply an electric field to the treated precursor mixture to concentrate the bound nanoparticle-entity assemblies in the sensing region; 
 apply a nanoparticle sensing voltage between the electrodes; 
 characterize a response of the sensing region to the nanoparticle sensing voltage to determine treated precursor mixture characterizing data; and 
   a detector configured to use the treated precursor mixture characterizing data to detect to the presence of the target biological entity in the biofluid.