Method for producing a standard for detecting protein aggregates of a protein misfolding disease, standard and use thereof

A method of using a standard for the detection of a protein aggregate of Alzheimer's disease, comprising:

• providing an inorganic silica nanoparticle having the size 15 to 200 nm;
• forming free amino groups on the surface of the inorganic silica nanoparticle for functionalizing the inorganic silica nanoparticle surface into an amine-functionalized nanoparticle;
• binding a maleinimido spacer carboxylic acid to the free amino groups;
• binding an amyloid beta monomer of the protein aggregate to the maleinimido spacer carboxylic acid by way of a sulfhydryl group at a free end of the amyloid beta monomer of the protein aggregate, thereby producing the standard comprising a known number of binding sites;
• providing a sample comprising an unknown number of binding sites;
• treating the sample and the standard with a fluorescent-labeled antibody;
• and
• inferring the number of binding sites in the sample from the standard treated with said fluorescent-labeled antibody.