High sensitivity determination of the concentration of analyte molecules or particles in a fluid sample

A system for detecting analyte molecules or particles, comprising;

• an array comprising a plurality of reaction vessels, wherein at least some of the reaction vessels contain no analyte molecules or particles and at least some of the reaction vessels contain at least one analyte molecule or particle;
• at least one binding ligand immobilized with respect an analyte molecule or particle within each reaction vessel containing an analyte molecule or particle;
• and
• precursor labeling agent molecules solubilized or suspended in a liquid contained within the reaction vessels, wherein the precursor labeling agent molecules are able to convert upon exposure to a binding ligand to labeling agent molecules that are insoluble within the liquid and/or that become immobilized within reaction vessels containing a binding ligand.

A method of detecting analyte molecules or particles in a fluid sample containing or suspected of containing analyte molecules or particles, comprising:

• providing a fluid sample containing or suspected of containing analyte molecules or particles;
• immobilizing at least one binding ligand with respect to at least some of the analyte molecules or particles;
• exposing the at least one binding ligand to a liquid in which is solubilized or suspended precursor labeling agent molecules, wherein exposing the precursor labeling agent molecules to the at least one binding ligand converts at least some of the precursor labeling agent molecules into labeling agent molecules which are insoluble in the liquid and/or which become immobilized within the reaction vessel;
• and
• determining a measure of the concentration of the analyte molecules or particles in the fluid sample based on the detection of labeling agent molecules wherein the true concentration of the analyte molecules or particles in the fluid sample is less than about 100×10−15 molar, and wherein the measure of the concentration determined in the determining act differs from the true concentration by no greater than 10%.

A kit for detecting analyte molecules or particles comprising:

• an array comprising a plurality of reaction vessels, each reaction vessel having a volume not exceeding about 100 femtoliters and each reaction vessel containing at least one analyte capture component immobilized or able to become immobilized within the reaction vessels having binding specificity for the analyte molecules or particles;
• at least one binding ligand having binding specificity for the analyte molecules or particles;
• and
• precursor labeling agent molecules able to be solubilized or suspended in a liquid, wherein the precursor labeling agent molecules are able to convert upon exposure to the at least one binding ligand to labeling agent molecules that are insoluble within the liquid and/or that become immobilized within the reaction vessels.

A method of detecting analyte molecules or particles in a fluid sample containing or suspected of containing analyte molecules or particles, comprising:

• partitioning the fluid sample across an array comprising a plurality of reaction vessels, so that at least some of the reaction vessels contain no analyte molecules or particles and at least some of the reaction vessels contain at least one analyte molecule or particle;
• immobilizing at least one binding ligand comprising a binding site with respect to an analyte molecule or particle within each reaction vessel containing at least one analyte molecule or particle;
• applying an enzymatic component to the array and capturing the enzymatic component with the binding site;
• contacting the enzymatic component with precursor labeling agent molecules, wherein the precursor labeling agent molecules are converted to labeling agent molecules upon contact with enzymatic components;
• detecting the labeling agent molecules;
• and
• determining from the detection of the labeling agent molecules the number of reaction vessels which contain an analyte molecule or particle.