Isfet array for detecting a single nucleotide polymorphism

A method of detecting a Single Nucleotide Polymorphism, SNP, within a genome, the method comprising:

• receiving a fluid sample containing a genome in four reaction chambers, the reaction chambers each containing a different, single one of the bases A, C, G, T, and an identical primer;
• detecting any pH changes within the reaction chambers using a pair of Ion Sensitive Field Effect Transistors, ISFETs, within each reaction chamber, the ISFETs of each pair comprising respective sensing membranes, or a common sensing membrane, exposed within the associated reaction chamber;
• and
• providing an output from a plurality of difference detectors, each difference detector having a pair of inputs coupled respectively to outputs of the ISFETs associated with different reaction chambers.

Apparatus comprising a module for detecting a single nucleotide polymorphism, SNP, within a genome and comprising:

• four reaction chambers for receiving a fluid sample, the reaction chambers each containing a different one of the bases A, C, G, T, and a primer;
• a reference electrode which in use is immersed in said fluid sample;
• and
• associated with each reaction chamber
• a pair of Ion Sensitive Field Effect Transistors, ISFETs, the ISFETs of each pair comprising respective sensing membranes, or a common sensing membrane, exposed within the associated reaction chamber, and the pair of ISFETs being coupled in a push-pull configuration;
• a MOSFET inverter stage having an input coupled to an output of said push-pull configuration;
• and
• an output stage providing a digital output that is switchable in dependence upon the voltage present at said sensing membrane(s).

A method of detecting a Single Nucleotide Polymorphism, SNP, within a genome, the method comprising:

• receiving a fluid sample in four reaction chambers, the reaction chambers each containing a different one of the bases A, C, G, T, and a primer;
• detecting any pH changes within the reaction chambers using a pair of Ion Sensitive Field Effect Transistors, ISFETs, associated with each reaction chamber, the ISFETs of each pair comprising respective sensing membranes, or a common sensing membrane, exposed within the associated reaction chamber, and the pair of ISFETs being coupled in a push-pull configuration;
• coupling the output of the push-pull ISFETs to the input of a MOSFET inverter stage;
• and
• providing a digital output from an output stage, the digital output being switchable in dependence upon the voltage present at said sensing membrane(s).